Rotor blade and means for noise reduction for a rotor blade

Abstract

Wind turbine rotor blade, wherein the wind turbine rotor blade comprises: - a front edge section with a front edge; - a trailing edge section with a trailing edge; - a pressure-side surface and a suction-side surface extending from the leading edge section and meeting at the trailing edge section; and - an aerodynamic structure for noise reduction provided at the trailing edge section, wherein the aerodynamic structure comprises a plurality of pressure communication channels between the suction-side surface and the pressure-side surface; - a camber line connecting the leading edge section and the trailing edge section, located halfway between the pressure-side surface and the suction-side surface, wherein the camber line of the aerodynamic structure is inclined towards the suction-side surface with respect to a camber line of the remaining part of the wind turbine rotor blade.

Description

TECHNICAL FIELD

[0001] The present invention generally relates to a rotor blade, a means for reducing noise for a rotor blade, and a wind turbine having rotor blades. More particularly, the invention relates to noise reduction while simultaneously reducing drag at a trailing edge portion of a wind turbine rotor blade by incorporating pressure communication channels, such as through-holes, into the trailing edge portion. The pressure communication channels can be provided on rotor blades, trailing edge inserts, attachments, or in any other form capable of reducing the noise of a rotor blade. STATE OF THE ART

[0002] A wind turbine is a device designed to capture the energy of the wind and convert it into a form that can be used to generate electricity. The wind turbine includes a rotor mounted on a mast. The wind turbine includes a hub and one or more rotor blades mounted on the hub, which are configured to generate lift as the wind blows over them. The lift generated by the rotor blades causes the rotor to rotate about a hub axis, and this rotational energy is then transferred via a drivetrain to a generator. The generator converts the rotational energy into electrical energy, which is then transmitted to a power grid or stored in a battery system for later use.The wind turbine may also include various sensors and control systems designed to optimize its performance and ensure safe and efficient operation.

[0003] The wind turbine rotor blade has a leading edge, a trailing edge, and opposing side surfaces on the suction side (top) and the pressure side (bottom), each starting at the leading edge and ending at the trailing edge.

[0004] Wind turbine blades generate noise during operation. The blades move through the air at high speeds, and this movement can create turbulence and vortexes that cause noise. The materials used to manufacture the blades can also play a role in the level of noise, as some materials are more prone to vibration or other types of noise than others. Noise reduction is particularly important for onshore wind turbines because they are built on land; in contrast, offshore wind turbines are built in waters typically farther from residential areas. For industrial-scale onshore wind turbines, the noise issue is more problematic due to their high speed and physical size.The sound power of the noise generated by the trailing edge of a wind turbine blade increases exponentially with the flow velocity in freestream flow. Therefore, it is important to have suitable noise reduction technology to enable large wind turbines to be installed with reasonable noise levels at a site close to residential areas.

[0005] Due to the potential health risks and social impacts, government agencies issue regulations and guidelines for wind turbine noise control. For example, in 2018, the World Health Organization issued guidelines for wind turbine noise, which recommend that the weighted sound pressure level (SPL) for day / evening / night be below 45 dB. The noise level thus determines the region in which wind turbines can be installed and the manner in which the wind turbine can be operated to comply with noise protection requirements in the surrounding area.

[0006] Turbulent trailing-edge boundary-layer noise (TBL-TE noise) is a dominant noise source in a wind turbine and is caused by the interaction between the turbulent boundary layer of air flowing from the leading edge of the blade to its trailing edge, which is the rear edge of the blade from which the air flows. TBL-TE noise can be generated, among other things, by the formation of vortices at the blade's trailing edge. These vortices can create a fluctuating pressure field that radiates noise into the surrounding air.

[0007] There are several factors that can affect the level of TBL-TE noise generated by a wind turbine blade. These include the shape and size of the blade, the speed at which the blade moves through the air, the blade material, the surface structure and properties of the trailing edge, and the characteristics of the airflow over the blade.

[0008] One promising approach to reducing TBL-TE noise is the use of through-holes near the trailing edges. The through-holes can be integrally formed in a wind turbine blade or attached as an attachment to a trailing edge of a wind turbine blade. This through-hole approach uses a series of small through-holes, openings, or through-holes in or near a trailing edge portion of a blade. The through-holes allow air pressure communication between the suction and pressure surfaces. This allows the pressure differences between the suction and pressure sides at the trailing edge to blend more smoothly than for a blade without trailing edge through-holes; this can help reduce the level of turbulence and noise the blade generates as it moves through the air.One advantage of trailing edge attachments with through holes is that they are relatively simple and inexpensive to implement. They can be easily attached to existing wind turbine blades and do not require additional power or control systems for their operation.

[0009] Dutch patent NL2025831B1 discloses a wind turbine blade with a trailing edge, wherein the trailing edge is provided with an attachment with through-holes. The through-hole attachment is provided with through-holes such that the through-holes have an open area on the suction side that is larger than an open area on the pressure side. The increased dimension serves to provide anti-fogging properties through purging.

[0010] However, trailing edges with through-holes can increase drag on the blade, potentially reducing turbine efficiency. The through-holes or perforations allow the surrounding airflow to pass through, creating drag. Furthermore, the through-holes also pose the risk of reduced structural stability. The dynamics of the trade-offs between through-holes and their disadvantages are not yet fully understood in the engineering community and are the subject of intensive research.

[0011] Therefore, there is a need for a rotor blade in which the rotor blade has a trailing edge region with through holes that can reduce noise and minimize the drag generated by the aerodynamic structure.

[0012] The "Background" section of this document is intended to place embodiments of the present invention in a technological and operational context and to assist those skilled in the art in understanding the scope and utility of the present invention. Unless expressly indicated as such, no statement contained herein is admitted to be prior art merely by its inclusion in the "Background" section. SUMMARY

[0013] The invention is defined in the independent claims. One object of the present invention is to reduce noise at or near the trailing edge of a wind turbine blade while simultaneously achieving low drag.

[0014] According to a first aspect of the invention, the present disclosure relates to a wind turbine rotor blade for providing a low noise level at a trailing edge portion of the wind turbine rotor blade. Noise reduction is achieved passively by an aerodynamic structure located in the trailing edge portion of the rotor blade. The aerodynamic structure is designed to minimize the drag generated by the aerodynamic structure.

[0015] The wind turbine rotor blade is designed to utilize an airflow flowing from a leading edge to a trailing edge. The wind turbine rotor blade further includes a pressure-side surface and a suction-side surface extending from the leading edge and meeting at the trailing edge. The airflow arriving at the leading edge splits into a pressure-side flow and a suction-side flow. The trailing edge is the final part of the blade that separates the pressure-side flow from the suction-side flow before the airflows converge.

[0016] The wind turbine rotor blade comprises a leading edge subsection with a leading edge and a trailing edge subsection with a trailing edge. The term "subsection" is used in this document to refer to a part of a wind turbine rotor blade, which may be composed of one or more elements that form the part of the wind turbine rotor blade. A trailing edge subsection may include a trailing edge that defines one end of a wind turbine rotor blade in the direction of airflow. When an attachment structure is connected to the wind turbine rotor blade and extends the length of the wind turbine rotor blade in the direction of airflow, the attachment structure defines the trailing edge of the wind turbine rotor blade.

[0017] An aerodynamic structure is provided at the trailing edge section. An aerodynamic structure at the trailing edge section is positioned upstream of the trailing edge, where the airflows converge. In other words, at least a portion of an airflow flowing from the leading edge to the trailing edge will enter the aerodynamic structure and, in embodiments, pass through it before reaching the trailing edge. The aerodynamic structure provides partial communication between the airflows on the pressure side and the suction side of the blade, upstream of the trailing edge of that blade.

[0018] In embodiments, the aerodynamic structure comprises a plurality of through-holes or pressure communication channels. The plurality of pressure communication channels may include at least one pressure communication channel with an hourglass channel configuration (HGCC). When a pressure communication channel has the hourglass channel configuration (HGCC), the HGCC is formed by a channel connecting: - a first area formed on the suction-side surface and having a first size; - a second area formed on the pressure-side surface and having a second size; - a third minimum area having a third size formed within the pressure communication channel and located between the first area and the second area, the third size preferably being at least 10%, more preferably at least 20%, smaller than the first area and the second area.

[0019] Embodiments or details of a duct with HGCC are provided below. The hourglass duct configuration shows a duct with an hourglass shape in cross-section, starting from a plane perpendicular to the longitudinal axis of the wind turbine rotor blade. The duct starts on either the suction or pressure side of the trailing edge section and is connected via a narrow waist between the pressure-side and suction-side surfaces. The narrow waist acts as a throttle valve. The pressure communication duct can be formed in the manner of a tube that is throttled in a central section. The throttling is preferably gradual. An HGCC is also formed by a duct that has starting points on both sides of the trailing edge and is connected via a throttled connection. The term "pressure communication duct" includes any air passage that allows the transmission of air pressure between two points or surfaces.A pressure communication channel can be a through-hole or an air passage with other aerodynamic components. In preferred embodiments, the pressure communication channel is a direct channel connection between two points, without side channels or other connection points.

[0020] In embodiments, the aerodynamic structure may include a first pressure communication channel with the HGCC and a second pressure communication channel with the HGCC. The second pressure communication channel is separate from the first channel, i.e., it is not connected to it. The aerodynamic structure may also include pressure communication channels that do not have the HGCC. The plurality of pressure communication channels is configured to influence an airflow flowing from the leading edge section to the trailing edge section.

[0021] A size of an area of ​​a pressure communication channel can be defined by an average diameter of the cross-sectional area when viewed from the direction perpendicular to the pressure-side surface or to the suction-side surface.

[0022] In embodiments, the third minimum area is located in the throttle between the first area and the second area. The third minimum area has a third size that is smaller than the first size and the second size. The through-holes are configured to form pressure communication channels between the suction-side surface and the pressure-side surface. The blade forms the boundary between the pressure and suction sides, which in turn allows a pressure differential between both sides. The pressure communication channels form the (first) open connection between the two sides at a location above / upstream of the trailing edge, where the two different pressures meet. The channel equalizes a pressure differential between the two sides. This throttles the pressure communication channel.The third minimal area throttles the air flow from the pressure to the suction side, but still allows a limited amount of air to flow through, which reduces the pressure difference.

[0023] In embodiments, the plurality of through-holes or pressure communication channels may define a density of the number of pressure communication channels, which indicates how densely the plurality of through-holes or pressure communication channels are distributed numerically. The sizes of the pressure communication channels and the density of the number of pressure communication channels combined may determine a total area density occupied by the pressure communication channels. The total area density may be defined between 0 and 0.99, where 0 means that no pressure communication channel is present on a surface, such as a suction-side surface or a pressure-side surface, and where 0.99 means that 99% of the pressure-side or suction-side surface is occupied by pressure communication channels.In embodiments, the total areal density is between 0.01 and 0.80, preferably between 0.05 and 0.70, more preferably between 0.07 and 0.60.

[0024] A camber line is a reference line that runs from the leading edge to the trailing edge and connects the midpoints between the pressure-side surface and the suction-side surface. The density of the number of pressure communication channels of the plurality of pressure communication channels may vary along the camber line. Preferably, the plurality of pressure communication channels is provided with an increasing density of the number of pressure communication channels in the direction from the leading edge section to the trailing edge section along the camber line, which is also referred to as the airflow direction. More preferably, the density of the number of pressure communication channels of similar size continuously increases in the direction from the leading edge section to the trailing edge section along the camber line.

[0025] In embodiments, the hourglass shape of the pressure communication channels with the HGCC can be viewed from a cross-sectional plane substantially perpendicular to a camber line and / or from a cross-sectional plane substantially perpendicular to a longitudinal axis of the wind turbine blade. The HGCC profile can be symmetrical or asymmetrical. The first size of the first area on the suction-side surface can differ from the second size of the second area on the pressure-side surface. A pressure communication channel can define a centerline, which is a reference line connecting the center of the pressure communication channel. The centerline is substantially perpendicular to the suction-side and pressure-side surfaces. The cross-sectional area of ​​the pressure communication channel can vary along the centerline.The pressure communication channel may have one or more minimal surfaces located at a location along the centerline or continuously along a portion of the centerline.

[0026] In embodiments, the plurality of pressure communication channels on the suction-side and pressure-side surfaces may have various cross-sectional shapes, such as a circle, a circle with a flat section, an ellipse, a triangle, a diamond, a rectangle, a kite, a trapezoid, a parallelogram, a rhombus, polygons, or any combination thereof.

[0027] In embodiments, the plurality of pressure communication channels may be some form of acoustic communication channels. The acoustic communication channels, preferably formed by pressure communication channels or channels with a membrane, enable acoustic communication between the pressure-side and suction-side surfaces and can prevent airflow. The prevention of airflow can be achieved by a structure in the acoustic communication channel preventing airflow while simultaneously allowing the passage of sound waves from one surface to the other. The prevention can be achieved by pressure communication channels or channels with a membrane.

[0028] By increasing the density of the number of pressure communication channels, a periodic distribution of the pressure communication channels can be avoided, which may generate additional noise or may not be able to mitigate the noise at certain acoustic frequencies. The periodic distribution can also be referred to as positions according to a regular grid. Furthermore, by increasing the density of the number of pressure communication channels in the direction from the leading edge subsection to the trailing edge subsection, the pressure communication channels can be arranged more effectively according to the noise level generated along a camber line. It is known that the level of turbulent trailing edge boundary layer noise is mainly concentrated at the trailing edge.This increasing density of pressure communication channels helps avoid an excessive number of pressure communication channels located away from the trailing edge, as this can lead to an unnecessary drag effect that can impair the overall efficiency of the wind turbine. On most wind turbine blades, the distance between the pressure-side and suction-side surfaces decreases along the camber line toward the trailing edge.

[0029] In embodiments, the plurality of pressure communication channels are distributed in an arbitrary, irregular manner such that they do not exhibit any periodicity in any direction on the pressure-side and suction-side surfaces. This periodicity may perform poorly at certain frequencies. Regardless of theory, noise generated by such a periodic structure is referred to as tonal noise. Preferably, the plurality of pressure communication channels are distributed irregularly, with at least three different spacings between the pressure communication channels, more preferably with at least four different spacings, even more preferably with at least five different spacings, and even more preferably with at least six different spacings.

[0030] In embodiments, the plurality of pressure communication channels on the suction-side and pressure-side surfaces may comprise pressure communication channels of different sizes and shapes. The sizes and shapes of pressure communication channels are defined as the sizes and shapes in the planes perpendicular to the centerline of the pressure communication channel. The sizes and shapes may also vary along the centerline. This allows for a further reduction in periodicities that can impair noise reduction performance and thus a broadening of the target noise frequencies. The plurality of pressure communication channels may have cross-sectional areas with an average diameter between 0.5 and 2.0 mm. In other words, the first size of the first area and the second size of the second area may be between 0.5 and 2.0 mm.The ratio between the third size of the minimum area and the first or second size may be between 1:1 and 1:2. Preferably, the plurality of pressure communication channels has at least three different sizes, more preferably at least five different sizes.

[0031] In embodiments, the pressure side and / or the suction side may be connected to an inner surface of the pressure communication channel in a generally continuous manner with limited discontinuity. In other words, a pressure communication channel may have a generally continuous inner surface that is continuously connected to the suction side or the pressure side. This allows the airflow to flow smoothly from the suction side or the pressure side into the pressure communication channel without flowing over discontinuous obstructions that could cause noise. The generally continuous inner surface may be present over the entire length of the pressure communication channel along the reference centerline along the longitudinal axis. The generally continuous surface may also be present between the surface of the suction side of the blade and the inner surface of the pressure communication channel.The inner surface of the plurality of pressure communication channels is smooth or continuously variable, so it does not have any significant irregularities or sharp edges that could cause additional localized noise. This smoothness allows the airflow flowing through the pressure communication channel to merge smoothly with the airflow flowing on the suction-side or pressure-side surface, thereby minimizing the drag force due to the airflow flowing through the pressure communication channel. This prevents the airflow through the pressure communication channel from being separated at a sharp edge, which would result in increased air resistance.The pressure communication channels can be configured to have a gradually decreasing cross-sectional area from the first surface formed on the suction-side surface and / or the second surface formed on the pressure-side surface toward the minimum area. Preferably, the gradual decrease is gentle and forms a smooth surface within the pressure communication channels. The smooth transition of the surface enables a reduction or dampening of the velocity of the air flow flowing from the suction-side surface and / or the pressure-side surface into the pressure communication channels. Due to the dampened velocity of the air flow, a smaller amount of air flows through the pressure communication channels, creating less air resistance.

[0032] In embodiments, the plurality of pressure communication channels may further include at least one airflow blocking device located adjacent to the minimum surface. The airflow blocking device is configured to block airflow pressure communication between the first surface and the second surface. The airflow blocking device may be acoustically transparent. For example, the airflow blocking device may be a flexible or elastic membrane covering a cross-section adjacent to the minimum surface and allowing kinetic energy, e.g., vibrational energy, to be transferred between the suction-side surface and the pressure-side surface. The airflow blocking device may be configured to filter out airflow but allow vibrations or vibrational energy to flow through the pressure communication channels.This means that the air flow cannot flow through the pressure communication channels, but the vibration energy can be transferred to the other side of the air flow blocking device and thus communicated.

[0033] In embodiments, the aerodynamic structure with the plurality of pressure communication channels is an attachment attached to the remaining portion of the wind turbine rotor blade, and while the attachment structure extends the length of the wind turbine rotor blade in the direction of airflow, it defines the trailing edge of the wind turbine rotor blade. If the attachment extends a longitudinal length (from the leading edge to the trailing edge) of the blade, the trailing edge is an extension edge provided by the attachment. An attachment configuration allows the aerodynamic structure to be easily replaced for maintenance purposes or to modify the pressure communication channels. Preferably, the attachment comprises multiple parts or elements that can be installed side by side along the trailing edge portion.

[0034] In embodiments, the aerodynamic structure is formed integrally with the remaining part of the wind turbine rotor blade.

[0035] In embodiments, the aerodynamic structure may be the trailing edge section of a wind turbine rotor blade and connected to the remaining part of the wind turbine rotor blade via a connecting means. The connecting means may consist of, or be any combination of: (i) a butt joint, (ii) a bushing on the suction-side surface, (iii) a bushing on the pressure-side surface, (iv) a hinge, (v) a flexible connecting element, or (vi) flexible connecting plate elements.

[0036] The butt joint can be created by mechanical fastening or chemical bonding. Mechanical fastening can include riveting, bolting, welding, and screwing. Chemical bonding can include the use of adhesive, glue, epoxy resin, solvent bonding, or viscosity-enhanced bonding.

[0037] The bushings on the suction and / or pressure-side surfaces can be designed as bolt bushings, nut plates, pins, captive screws, quick-release pins, press-in pins, or knurled pins. The connection via the bushings can also be achieved by chemical bonding.

[0038] The hinge can be a pin hinge, a friction hinge, a flexible hinge or a movable hinge.

[0039] The flexible connecting element may be a flexible or elastic body placed between the aerodynamic structure and the remaining part of the wind turbine rotor blade. The flexible connecting element may be physically and / or chemically bonded to the aerodynamic structure and the remaining part of the wind turbine rotor blade. The flexibility of the flexible connecting element allows the aerodynamic structure to move passively in response to the airflow passing over the blade surfaces. Alternatively, the flexible connecting element may be flexible plates attached to the suction-side and pressure-side surfaces of the aerodynamic structure and configured to contact the suction-side and pressure-side surfaces.The flexible plates may have an elasticity that allows a firm connection of the aerodynamic structure to the rest of the wind turbine rotor blade. A flexible plate holder may be installed on the pressure-side and / or suction-side surface to accommodate and hold the flexible plates between the pressure-side surface and the flexible plate holder and / or between the suction-side surface and the flexible plate holder.

[0040] In embodiments, a camber line of the aerodynamic structure may differ from a camber line of the remaining part of the wind turbine rotor blade. As already mentioned, a camber line is a reference line running from the leading edge to the trailing edge and connecting the midpoints between the pressure-side surface and the suction-side surface. Preferably, the camber line of the aerodynamic structure is inclined toward the suction-side surface relative to the camber line of the remaining part of the wind turbine rotor blade. More preferably, the camber line of the aerodynamic structure is inclined toward the suction-side surface at an angle of at least 1°. In embodiments, the angle is between 1° and 10°. In preferred embodiments, the angle is between 1° and 5°.In embodiments, the angle is more preferably between 5° and 10°, even more preferably between 10° and 20°, and even more preferably between 20° and 30°.

[0041] In embodiments, the aerodynamic structure may further comprise trailing edge spikes, wherein the dimension of the spikes is less than one centimeter.

[0042] According to a second aspect of the invention, the present disclosure relates to an aerodynamic structure that can be attached or connected to a wind turbine rotor blade for noise reduction with low air resistance.

[0043] In embodiments, the aerodynamic structure may have a pressure-side surface and a suction-side surface adapted to form a continuous airfoil with a wind turbine rotor blade. When attached or connected to the wind turbine rotor blade, the pressure-side and suction-side surfaces of the aerodynamic structure are flush with the pressure-side and suction-side surfaces of the wind turbine rotor blade, respectively. The aerodynamic structure includes a downstream trailing edge where the pressure-side and suction-side surfaces meet. The side opposite the trailing edge along a camber line is a connecting edge positioned upstream. The connecting edge may be connected to the trailing edge of a wind turbine rotor blade.The aerodynamic structure includes a plurality of pressure communication channels, wherein each of a first and a second separate pressure communication channel has an hourglass channel configuration (HGCC) or one of the embodiments described herein. The pressure communication channels form pressure communication channels between the suction-side surface and the pressure-side surface. The pressure communication channels facilitate the equalization of pressure fluctuations in two turbulent boundary layer air flows on the suction-side surface and the pressure-side surface. As a result, the profile of the pressure communication channel has, for example, an hourglass-like structure with a narrow waist between the suction-side and pressure-side surfaces.

[0044] In embodiments, the plurality of pressure communication channels may define a density of the number of pressure communication channels, which indicates how densely the plurality of pressure communication channels are distributed. A camber line of the aerodynamic structure is defined by a reference line running from the connecting edge to the trailing edge and connecting the midpoints between the pressure-side surface and the suction-side surface. The density of the number of pressure communication channels of the plurality of pressure communication channels may vary along the camber line. Preferably, the plurality of pressure communication channels is provided with an increasing density of the number of pressure communication channels in the direction from the connecting edge portion to the trailing edge portion along the camber line.Even more preferably, the density of the number of pressure communication channels continuously increases in the direction from the connecting edge portion to the trailing edge portion along the camber line.

[0045] Increasing the density of the number of pressure communication channels can prevent a local periodic distribution, which may not contribute to reducing noise at certain acoustic frequencies. Furthermore, by concentrating the pressure communication channel density near the trailing edge, the pressure communication channels can be more effectively localized according to the noise level generated along a camber line. It is known that the noise level increases along the camber line toward the trailing edge. This effective distribution of pressure communication channels can avoid excessively large numbers of pressure communication channels located away from the trailing edge, which can create an unnecessary drag effect that can impair the overall efficiency of the wind turbine.On most wind turbine rotor blades, the distance between the pressure and suction surfaces decreases along the camber line toward the trailing edge. The increasing density of pressure communication channels therefore also allows for a smaller number of pressure communication channels in the thicker region, which can generate significant drag due to the large pressure difference between the suction and pressure surfaces.

[0046] In embodiments, the plurality of pressure communication channels is distributed in a random, irregular manner such that it does not exhibit any periodicity in any direction on the pressure-side and suction-side surfaces. At certain frequencies, noise reduction may be insufficient with periodic aerodynamic structures. Preferably, the plurality of pressure communication channels is distributed irregularly, with at least three different spacings between the pressure communication channels, more preferably with at least four different spacings, even more preferably with at least five different spacings, and even more preferably with at least six different spacings.

[0047] In embodiments, the plurality of pressure communication channels may have various cross-sectional shapes, such as circle, ellipse, triangle, diamond, rectangle, kite, trapezoid, parallelogram, rhombus, polygons, or any combination thereof.

[0048] In embodiments, the plurality of pressure communication channels may comprise pressure communication channels of different sizes and shapes. This allows for a further reduction in periodicities that can impair noise reduction performance and thus a broadening of the target noise frequencies. The plurality of pressure communication channels may have cross-sectional areas with average diameters between 0.5 and 2.0 mm. In other words, the first size of the first area and the second size of the second area may be between 0.5 and 2.0 mm. The ratio between the third size of the minimum area and the first or second size may be between 1:1 and 1:2. Preferably, the plurality of pressure communication channels have at least three different sizes, more preferably at least five different sizes.

[0049] In embodiments, the plurality of pressure communication channels are configured to influence an airflow flowing from the connecting edge portion to the trailing edge portion.

[0050] In embodiments, the inner surface of the plurality of pressure communication channels is smooth, so that it does not have any significant irregularities or sharp edges that could cause additional localized noise. The pressure communication channels can be configured to have a gradually decreasing cross-sectional area from the first surface formed on the suction-side surface and / or the second surface formed on the pressure-side surface towards the minimum area. Preferably, the gradual decrease is gentle and forms a smooth surface within the pressure communication channels. The smooth transition of the surface enables a reduction or attenuation of the velocity of the air flow flowing from the suction-side surface and / or the pressure-side surface into the pressure communication channels.Due to the dampened speed of the air flow, a smaller amount of air flows through the pressure communication channels and there is less air resistance.

[0051] In embodiments, the plurality of pressure communication channels may further include at least one airflow blocking device located adjacent to the minimum surface. The airflow blocking device is configured to block airflow pressure communication between the first surface and the second surface. The airflow blocking device may be acoustically transparent. For example, the airflow blocking device may be a flexible or elastic membrane covering a cross-section adjacent to the minimum surface and enabling transfer of kinetic energy, e.g., vibrational energy, between the suction-side surface and the pressure-side surface. The airflow blocking device may be configured to flexibly vibrate, thus enabling acoustic communication between the suction-side surface and the pressure-side surface.This means that the airflow cannot flow through the pressure communication channels, but the kinetic energy can be transferred to the other side of the airflow blocking device and thus communicated.

[0052] In embodiments, the aerodynamic structure may include a connecting element configured to connect the aerodynamic structure to a wind turbine rotor blade through mechanical fastening or chemical bonding. Mechanical fastening may include riveting, bolting, welding, and screwing. Chemical bonding may include the use of adhesive, glue, epoxy, solvent bonding, viscosity-enhanced bonding, or tapping with an adhesive.

[0053] In embodiments, the aerodynamic structure may further comprise serrations on the trailing edge, wherein the size of the serrations is preferably less than one centimeter.

[0054] According to a third aspect of the invention, the present disclosure relates to an aerodynamic structure to be attached to a trailing edge of a wind turbine rotor blade to reduce noise while maintaining low drag. The aerodynamic structure includes an increasing pressure communication channel density along a camber line.

[0055] In embodiments, the aerodynamic structure may have a pressure-side surface and a suction-side surface adapted to form a continuous airfoil with a wind turbine rotor blade. When attached or connected to the wind turbine rotor blade, the pressure-side and suction-side surfaces of the aerodynamic structure are flush with the pressure-side and suction-side surfaces of the wind turbine rotor blade, respectively. The aerodynamic structure includes a trailing edge where the pressure-side and suction-side surfaces meet. The side opposite the trailing edge along a camber line is a connecting edge. The connecting edge may be connected to the trailing edge of a wind turbine rotor blade.The aerodynamic structure has a plurality of pressure communication channels, the pressure communication channels comprising a first surface formed on the suction side surface and a second surface formed on the pressure side surface.

[0056] In embodiments, the plurality of pressure communication channels may have various cross-sectional shapes, such as a circle, ellipse, triangle, rhombus, rectangle, kite, trapezoid, parallelogram, rhombus, polygon, or any combination thereof. In embodiments, at least two of the plurality of pressure communication channels in the aerodynamic structure of the third aspect comprise HGCCs.

[0057] In embodiments, the plurality of pressure communication channels may include pressure communication channels of different sizes and shapes. The "size" of a pressure communication channel or the area of ​​a pressure communication channel is used herein to indicate an average diameter of the pressure communication channel or the area of ​​the pressure communication channel. This allows for a further reduction in periodicities that can impair noise reduction performance and thus an expansion of the target noise frequencies. The plurality of pressure communication channels may have cross-sectional areas with average diameters between 0.5 and 2.0 mm. In other words, the first size of the first area and the second size of the second area may be between 0.5 and 2.0 mm. The ratio between the third size of the minimum area and the first or second size may be between 1:1 and 1:2.Preferably, the plurality of pressure communication channels has at least three different sizes, more preferably at least five different sizes.

[0058] In embodiments, the plurality of pressure communication channels are configured to influence an airflow flowing from the connecting edge portion to the trailing edge portion.

[0059] In embodiments, the inner surface of the plurality of pressure communication channels is smooth, so that it does not have any significant irregularities or sharp edges that could cause additional localized noise. This prevents the airflow through the pressure communication channel from being severed at a sharp edge, which would lead to increased air resistance. Furthermore, it creates a more favorable airflow attack point for a voluminous airflow and prevents noise from localized vortices that can be generated by the sharp edge. The pressure communication channels can be configured to have a gradually decreasing cross-sectional area from the first surface formed on the suction-side surface and / or the second surface formed on the pressure-side surface towards the minimum area.Preferably, the gradual decrease is gentle, forming a smooth surface within the pressure communication channels. The smooth transition of the surface allows for a reduction or damping of the airflow velocity flowing from the suction-side surface and / or the pressure-side surface into the pressure communication channels. Due to the dampened airflow velocity, a smaller amount of air flows through the pressure communication channels, creating less air resistance.

[0060] In embodiments, the plurality of pressure communication channels may further comprise at least one airflow blocking device located between the first and second surfaces. The airflow blocking device is configured to block airflow pressure communication between the first surface and the second surface. The airflow blocking device may be acoustically transparent. For example, the airflow blocking device may be a flexible or elastic membrane covering a cross-section adjacent to the minimum surface and enabling transfer of kinetic energy, e.g., vibrational energy, between the suction-side surface and the pressure-side surface. The airflow blocking device may be configured to flexibly vibrate, thus enabling acoustic communication between the suction-side surface and the pressure-side surface.This means that the air flow cannot flow through the pressure communication channels, but the kinetic energy can be transferred to the other side of the air flow blocking device and thus communicated.

[0061] In embodiments, the aerodynamic structure may include a connecting element configured to connect the aerodynamic structure to a wind turbine rotor blade through mechanical fastening or chemical bonding. Mechanical fastening may include riveting, bolting, welding, and screwing. Chemical bonding may include the use of adhesive, glue, epoxy, solvent bonding, viscosity-enhanced bonding, or tapping with an adhesive.

[0062] In embodiments, the aerodynamic structure may further comprise trailing edge spikes, wherein the dimension of the spikes is less than one centimeter.

[0063] According to a fourth aspect of the invention, the present disclosure relates to a wind turbine rotor blade comprising an aerodynamic structure with a plurality of pressure communication channels located at a trailing edge portion of the wind turbine rotor blade. The aerodynamic structure forms a camber line that is inclined toward a suction-side surface relative to a camber line of the remaining portion of the wind turbine rotor blade.

[0064] In embodiments, the noise is passively reduced by the aerodynamic structure arranged at the trailing edge. Due to the passive flow control, the aerodynamic structure does not require external energy to achieve the noise reduction. The wind turbine rotor blade comprises a leading edge section having a leading edge and a trailing edge section having a trailing edge. The wind turbine rotor blade further comprises a pressure-side surface and a suction-side surface extending from the leading edge section and meeting at the trailing edge section. An aerodynamic structure is provided at the trailing edge section. The aerodynamic structure has a plurality of pressure communication channels, the pressure communication channels comprising a first surface formed on the suction-side surface and a second surface formed on the pressure-side surface.

[0065] In embodiments, a camber line of the aerodynamic structure may differ from a camber line of the remaining part of the wind turbine rotor blade. As already mentioned, a camber line is a reference line running from the leading edge to the trailing edge and connecting the midpoints between the pressure-side surface and the suction-side surface. Preferably, the camber line of the aerodynamic structure is inclined towards the suction-side surface relative to the camber line of the remaining part of the wind turbine rotor blade. More preferably, the camber line of the aerodynamic structure is inclined to the suction-side surface at an angle of at least 1°, preferably between 1° and 10°, preferably between 2° and 5°. In embodiments, the angle is more preferably between 5° and 10°, even more preferably between 10° and 20°, and even more preferably between 20° and 30°. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will now be described in more detail below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, this invention should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the spirit and scope of the invention to those skilled in the art. Reference is made to the accompanying figures. Fig. Figure 1 illustrates a perspective view of a wind turbine rotor blade with a plurality of pressure communication channels for noise reduction at low drag. Fig. Figure 2 illustrates a perspective view of an alternative embodiment of the Fig. 1 shown wind turbine rotor blade. Fig. Figure 3 illustrates an aerodynamic structure incorporated into or added to a wind turbine blade for noise reduction and low drag. Fig. 4 illustrates a side cross-sectional view of an aerodynamic structure of a wind turbine rotor blade, the aerodynamic structure including a plurality of pressure communication channels. Fig. Figure 5 illustrates a perspective view of the aerodynamic structure of Fig. 1-2, which is contained in or added to a wind turbine rotor blade to reduce noise and provide low drag. Fig. Figure 6 illustrates a top view of the aerodynamic structure of Fig. 1-2, which is contained in or added to a wind turbine rotor blade to reduce noise and provide low drag. Fig. Figure 7 illustrates a plan view of an alternative aerodynamic structure incorporating spikes. Fig. Figures 8a-8h illustrate a cross-sectional side view of aerodynamic structures integrated into or connected to wind turbine rotor blades. Fig. Figure 8a illustrates the aerodynamic structure of Fig. 3, which is formed integrally on the trailing edge section of a wind turbine rotor blade. Fig. Figure 8b illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of a butt joint. Fig. Figure 8c illustrates the aerodynamic structure of Fig. 8b, wherein a camber line of the aerodynamic structure is inclined with respect to a camber line of the remaining part of a wind turbine rotor blade towards a suction-side surface. Fig. Figure 8d illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of a flexible connecting element. Fig. Figure 8e illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of a bushing arranged on a pressure-side surface. Fig. Figure 8f illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of a bushing located on both the pressure-side and the suction-side surfaces. Fig. Figure 8g illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of flexible plates and a flexible plate holder. Fig. 8h illustrates the aerodynamic structure of Fig. 3, which is connected within a wind turbine rotor blade by means of a hinge. Fig. 9 is a graph illustrating a result of sound pressure level reduction measurement, indicating an improved noise reducing effect of the first aspect of the present invention over a trailing edge having pressure communication channels without a minimum area. DETAILED DESCRIPTION

[0067] For simplicity and illustrative purposes, the present invention will be described primarily with reference to exemplary embodiments. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention.

[0068] However, it will be readily apparent to one of ordinary skill in the art that the present invention may be practiced without limitation to these specific details. In this specification, well-known methods and structures have not been described in detail in order not to unnecessarily obscure the present invention.

[0069] Fig. 1 illustrates a wind turbine rotor blade 100 that provides low noise while also having low drag at a trailing edge portion 114. The wind turbine rotor blade 100 includes a leading edge portion 104 having a leading edge 106. The leading edge 106 is an edge of the wind turbine rotor blade 100 that faces the airflow during rotation. On the other side of the leading edge 106 is a trailing edge portion 114 having a trailing edge 116. The trailing edge 106 is an edge that faces away from the airflow during rotation of the wind turbine rotor blade 100. The trailing edge portion 114 is typically flatter and thinner, and thus thinner than the leading edge portion 104 in a direction substantially perpendicular to the direction of an airflow that a wind turbine rotor blade is designed to utilize.The wind turbine rotor blade further includes a pressure-side surface 140 and a suction-side surface 130 extending from the leading edge section 104 and meeting at the trailing edge section 114. A span line 16 is a reference line located midway between the leading edge 106 and the trailing edge 116. The leading edge section 104 and the trailing edge section 114 can be defined with respect to the span line 16. The portion of the wind turbine rotor blade 100 located between the leading edge 106 and the tension line 16 is the leading edge subsection 104. Similarly, the portion of the wind turbine rotor blade 100 located between the trailing edge 116 and the tension line 16 is the trailing edge subsection 114. A pressure-side surface 130 and a suction-side surface 140 extend from the leading edge subsection 104 and meet at the trailing edge subsection 114.An aerodynamic structure 120 is provided at the trailing edge section 114. The aerodynamic structure 120 includes acoustic communication channels formed by a plurality of pressure communication channels 300.

[0070] Fig. Figure 2 illustrates another embodiment of the wind turbine rotor blade 100. This embodiment differs from Fig. 1 in that a camber line 17 of an aerodynamic structure 120 is inclined toward a suction-side surface 130 with respect to a camber line 15 of the remaining part of the wind turbine rotor blade 100. A camber line (15, 17) or camber centerline is a reference line that runs from the leading edge 106 to the trailing edge 116 and connects the midpoints between the pressure-side surface 140 and the suction-side surface 130. The inclination angle θ can be any angle between 0° and 90°.

[0071] Fig. 3 illustrates an aerodynamic structure 120 with a plurality of through-holes 300. A pressure communication channel 300 may include a first surface 302 formed on the suction-side surface 130 and a second surface 304 formed on the pressure-side surface 140. The first surface 302 has a first size and the second surface 304 has a second size. The sizes are defined by the cross-sectional area of ​​the surfaces 302, 304. The pressure communication channel 300 may further include a minimum area 306. The minimum area 306 has a cross-sectional area that is smaller than the size of the first surface 302 and the second surface 304. The minimum area 306 shown in this embodiment is cylindrical.

[0072] The plurality of pressure communication channels 300 may define a density of the number of pressure communication channels, which is defined by the number of pressure communication channels 300 per unit area or by the number of pressure communication channels per length along a camber line 17. The density of the number of pressure communication channels thus indicates how densely the plurality of pressure communication channels 300 are distributed in the aerodynamic structure 120. The plurality of pressure communication channels 300 may be configured to form a density of the number of pressure communication channels that increases along the camber line 17 in an airflow direction 150. The airflow direction 150 is also a direction pointing from the leading edge section 104 to the trailing edge section 114 of the wind turbine rotor blade 100. The density of the number of pressure communication channels may vary continuously in the airflow direction 150.

[0073] The plurality of pressure communication channels 300 includes at least a first and a second channel. The first and second channels are separate channels. The first and second channels each have two connection points. The first and second channels each have HGCC.

[0074] The plurality of pressure communication channels 300 may have a smooth interior surface so that it does not contain any significant irregularities or sharp edges that could generate additional localized noise at high frequencies. This is intended to provide a more favorable airflow attack point for a voluminous airflow and to prevent noise from localized vortices that can be generated by a sharp edge. The pressure communication channel 300 may be configured to have a gradually decreasing cross-sectional area from the first surface 302 formed on the suction-side surface 130 and / or from the second surface 302 formed on the pressure-side surface 140 toward the minimum area 306. Preferably, the gradual decrease is gentle and forms a smooth surface within the pressure communication channel 300.The smooth transition of the surface allows for a reduction or damping of the velocity of the air flow flowing from the suction-side surface 130 and / or the pressure-side surface 140 into the pressure communication channels 300. Due to the dampened velocity of the air flow, a smaller amount of air flows through the pressure communication channels 300 and less air resistance is created.

[0075] Fig. Figure 4 illustrates a cross-sectional side view of an aerodynamic structure 120 having a plurality of pressure communication channels, wherein the aerodynamic structure 120 is connected to the remaining part of the wind turbine rotor blade 100 of Fig. 2. A camber line 17 of an aerodynamic structure 120 may form an angle θ with a camber line 15 of a wind turbine rotor blade 100 and may be inclined toward the suction-side surface 130 with respect to the camber line 15 of the remaining part of the wind turbine rotor blade 100.

[0076] The side cross-sectional view of the plurality of pressure communication channels 300 shows the channels having HGCC. HGCC is characterized by a minimum area 306 that is smaller than the first area 302 on the suction-side surface 130 and the second area 304 on the pressure-side surface 140; the cross-sectional side view of the pressure communication channels forms an hourglass-like shape. The density of the number of pressure communication channels can vary in an airflow direction 150 pointing from the leading edge section 104 to the trailing edge section 114 of the wind turbine rotor blade 100. The Fig. The embodiment illustrated in Figure 4 shows that the plurality of pressure communication channels 300 are distributed such that the density of the number of pressure communication channels increases along the direction of an airflow 150 toward the trailing edge 116.

[0077] Fig. Figure 5 illustrates an alternative embodiment of the Fig. 3 illustrated aerodynamic structure 120. This embodiment differs from Fig. 3 in that the pressure communication channel 300 further comprises at least one airflow blocking device 500 disposed adjacent to a minimal surface 306. The airflow blocking device 500 is configured to block airflow pressure communication between the first surface 302 and the second surface 304. The airflow blocking device 500 may be acoustically transparent. For example, the airflow blocking device may be a flexible or elastic membrane that may allow transmission of vibration energy and sound waves between the suction-side surface 130 and the pressure-side surface 140. By blocking pressure flow but allowing acoustic flow, the pressure communication channel 300 is not flow-permeable but acoustically transparent. It should be noted that the flow permeability may create air resistance, which this airflow blocking device 500 prevents.

[0078] Fig. 6 illustrates an aerodynamic structure 120 wherein the plurality of pressure communication channels 300 are distributed in an arbitrary, irregular manner so as not to form any periodicity in one direction on a suction-side surface 130 and a pressure-side surface 140. Fig. 6 is a plan view showing the suction-side surface 130. The suction-side surface 130 can be divided into two orthogonal directions: an airflow direction 150 and a spanwise direction 160 that is substantially perpendicular to the airflow direction 150. As shown in Fig. 6, the pressure communication channels 300 may be irregularly distributed in the air flow direction 150 and / or the spanwise direction 160 as viewed from the suction-side surface 130. Preferably, the plurality of pressure communication channels 300 has at least three different distances between the pressure communication channels, more preferably at least four different distances, even more preferably at least five different distances, and even more preferably at least six different distances. The plurality of pressure communication channels 300 may have different sizes and shapes. The plurality of pressure communication channels may have cross-sectional areas with average diameters between 0.5 and 2.0 mm. In other words, the first size of the first area and the second size of the second area may be between 0.5 and 2.0 mm.The ratio between the third minimum area size and the first or second size can be between 1:1 and 1:2. The shape can be any irregular shape, a circle, an ellipse, a triangle, a rhombus, a rectangle, a kite, a trapezoid, a parallelogram, a rhombus, polygons, or any combination thereof.

[0079] Fig. 7 illustrates an aerodynamic structure 120 with prongs 700 on the trailing edge 116. The aerodynamic structure 120 may include a plurality of pressure communication channels 300, wherein the plurality of pressure communication channels 300 has a density of the number of pressure communication channels that increases in an airflow direction 150. The prongs 700 may have a dimension of less than one centimeter. In other words, the length of the prongs 700 in the airflow direction 150 is less than one centimeter.

[0080] Fig. 8a-8h illustrate various embodiments of an aerodynamic structure 120 of a wind turbine rotor blade 100 that is integrally formed or connected to the remaining part of the wind turbine rotor blade 800 at the trailing edge portion 114. The aerodynamic structure 120 may form a trailing edge 116 of the wind turbine rotor blade 100.

[0081] As in Fig. As shown in Figure 8a, the aerodynamic structure 120 may be formed integrally with the remaining part of the wind turbine rotor blade 800.

[0082] Fig. Figure 8b shows that the aerodynamic structure 120 can be connected to the remaining part of the wind turbine rotor blade 800 by a butt joint. The butt joint can be achieved by mechanical fastening or chemical adhesion.

[0083] Fig. 8c shows that the aerodynamic structure 120 may be inclined toward the suction-side surface 130 of the wind turbine rotor blade 100. In other words, a camber line 17 of the aerodynamic structure 120 may be inclined toward the suction-side surface 130 with respect to a camber line 15 of the remaining part of the wind turbine rotor blade 800.

[0084] Fig. Figure 8d illustrates that the aerodynamic structure 120 may be connected to the remaining part of the wind turbine rotor blade 800 by a flexible connecting element 802 placed between the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800. The flexible connecting element may be physically and / or chemically connected to the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800.

[0085] Fig. 8e-8f shows that the connection between the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800 can be made by mechanical bushings. Fig. 8e shows a bushing formed on the pressure side 140 of the wind turbine rotor blade 800. Fig. 8f shows bushings formed on both the pressure side 140 and the suction side 130 of the wind turbine rotor blade 800.

[0086] Fig. Figure 8g shows that the connection between the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800 can be established using flexible plates 804, 806 of the aerodynamic structure and a flexible plate holder 808 of the remaining part of the wind turbine rotor blade 800. A first and a second flexible plate can be located on a suction-side surface and a pressure-side surface of the aerodynamic structure 120, respectively. When the first flexible plate 806 is connected to the remaining part of the wind turbine blade 800, it has close contact with the suction-side surface 130 of the wind turbine blade 800, while the second flexible plate 808 has close contact with the pressure-side surface 140. The connection can be further secured by a flexible plate holder 808 of the remaining part of the wind turbine rotor blade 800.

[0087] Fig. Figure 8h shows that the connection between the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800 can be established using a mechanical hinge. The hinge enables the formation of an adjustable angle between the aerodynamic structure 120 and the remaining part of the wind turbine rotor blade 800.

[0088] Fig. 9 illustrates a sound pressure level reduction measurement result indicating an improved noise reducing effect of the first aspect of the present invention over a wind turbine rotor blade having pressure communication channels without a minimum area.

[0089] Two different aerodynamic structures were measured to reduce TBL-TE noise at a trailing edge: • Sample 1: an aerodynamic structure with cylindrical pressure communication channels with a constant area of ​​1 mm • Sample 2: an aerodynamic structure of the first aspect of the present invention having a plurality of pressure communication channels comprising a minimum area of ​​1 mm and a larger first and second area of ​​1.5 mm

[0090] Samples 1 and 2 are provided for an identical DU-96 airfoil. The specification of the DU-96 airfoil is listed in Timmer et al., "Summary of the Delft University Wind Turbine Dedicated Airfoils," Journal of Solar Energy Engineering, Vol. 125, November 2003, pages 488-496. The chord length of the airfoil is 200 mm. The free stream velocity is set to 28 m / s. The two samples differ only in that Sample 2 has a minimum area located between a first area formed on a suction-side surface and a second area formed on a pressure-side surface. The minimum area has a size of 1 mm.

[0091] The diagram shows the reduction of the sound pressure level SPL Red plotted against the noise frequency f. The reduction of the sound pressure level SPL RedIndicates by how much the sound pressure level is reduced compared to a reference noise measurement. The reference noise measurement was performed using an aerodynamic structure without a pressure communication channel. A first curve 902 shows the measurement result for sample 1. A second curve 901 shows the measurement result for sample 2. As shown in the diagram, the second curve 901 shows a 1-2 dB higher noise reduction effect compared to the first curve 902 across the entire frequency range from 500 Hz to 1800 Hz.

[0092] It should be understood that the present invention may be embodied otherwise than as specifically set forth herein without departing from the essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes which come within the meaning and range of equivalence of the appended claims are intended to be embraced therein.

[0093] Below, numbered paragraphs define embodiments of the invention. Paragraph 1. Wind turbine rotor blade, the wind turbine rotor blade comprising: - a leading edge section with a leading edge; - a trailing edge section with a trailing edge; - a pressure-side surface and a suction-side surface extending from the leading edge section and meeting at the trailing edge section; and - an aerodynamic structure for noise reduction provided on the trailing edge section, the aerodynamic structure having a plurality of through-holes, the plurality of through-holes including at least one through-hole comprising: • a first area formed on the suction-side surface and having a first size; • a second area formed on the pressure-side surface and having a second size; and • a minimum area with a third size that lies between the first area and the second area, where the third size is smaller than both the first size and the second size. Paragraph 2. The wind turbine rotor blade of paragraph 1, wherein the plurality of through holes defines a density of the number of pressure communication channels that increases in the direction from the leading edge section to the trailing edge section. Paragraph 3. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the at least one through-hole is further configured to have a substantially continuous area from the pressure-side surface to the minimum area. Paragraph 4. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the at least one through-hole is further configured to have a substantially continuous area from the suction-side surface to the minimum area. Paragraph 5. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the wind turbine rotor blade further comprises a camber line connecting the leading edge sub-section and the trailing edge sub-section and located midway between the pressure-side surface and the suction-side surface, wherein the camber line of the aerodynamic structure is inclined towards the suction-side surface with respect to a camber line of the remaining part of the wind turbine rotor blade. Paragraph 6. Wind turbine rotor blade according to paragraph 5, wherein the camber line of the aerodynamic structure is inclined towards the suction-side surface at an angle of 1°, preferably between 2 and 5°. Paragraph 7. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes are configured to influence an airflow flowing from the leading edge section to the trailing edge section. Paragraph 8. Wind turbine rotor blade according to one of the preceding paragraphs, wherein a surface of the at least one through-hole has an average diameter between 0.5 and 2.0 mm. Paragraph 9. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the ratio between the third size and the first size is between 1:1 and 1:2. Paragraph 10. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the ratio between the third size and the second size is between 1:1 and 1:2. Paragraph 11. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes comprises at least three different sizes of the pressure-side surface. Paragraph 12. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes comprises at least three different sizes of the suction-side surface. Paragraph 13. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through holes can establish pressure communication between an air flow on the pressure-side surface and an air flow on the suction-side surface. Paragraph 14. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes comprises at least one airflow blocking device arranged between the suction-side surface and the pressure-side surface, wherein the at least one airflow blocking device is acoustically transparent. Paragraph 15. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the aerodynamic structure is an attachment attached to the trailing edge section of the wind turbine rotor blade. Paragraph 16. Wind turbine rotor blade according to one of the preceding paragraphs, wherein the aerodynamic structure is formed in one piece as a trailing edge section of the wind turbine rotor blade. Paragraph 17. A wind turbine rotor blade according to any one of paragraphs 1 to 16, wherein the aerodynamic structure forms the trailing edge section and is connected to the remainder of the wind turbine rotor blade using one or any combination of the following means: (i) a butt joint, (ii) a bushing on the suction side surface, (iii) a bushing on the pressure side surface, (iv) a hinge, (v) a flexible connecting element, or (vi) flexible connecting plate elements. Paragraph 18. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes comprises at least two different shapes of through-holes, wherein the at least two different shapes are any combination of the following: (i) circle, (ii) flat-surfaced circle, (iii) ellipse, (iv) triangle, and (v) rhombus. Paragraph 19. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the plurality of through-holes are irregularly distributed with at least three different pitches, preferably with at least four different pitches, more preferably with at least five different pitches, even more preferably with at least six different pitches. Paragraph 20. A wind turbine rotor blade according to any one of the preceding paragraphs, wherein the aerodynamic structure further comprises trailing edge serrations. Paragraph 21. An aerodynamic structure for mounting on a surface of a wind turbine rotor blade, the aerodynamic structure comprising: - a plurality of through-holes, wherein the plurality of through-holes comprises at least one through-hole defining a pressure-side surface and a suction-side surface; and - a minimum area smaller than the pressure side surface and the suction side surface located between the pressure side surface and the suction side surface. Paragraph 22. Wind turbine, comprising: - a wind turbine mast with an upper part and a lower part; - a nacelle located on top of the wind turbine mast; - a rotor hub rotatably mounted on the nacelle; - one or more wind turbine blades as defined in paragraph 1 mounted on the rotor hub, the wind turbine blades defining a rotor plane; - a shaft coupled to the rotor hub; and - a generator coupled to the shaft, the generator being configured to convert a torque of the shaft into electrical energy. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] NL 2025831B1

[0009] Cited non-patent literature

[0000] Timmer et al., „Summary of the Delft University Wind Turbine Dedicated Airfoils,“ Journal of Solar Energy Engineering, Bd. 125, November 2003, Seiten 488-496

[0090]

Claims

[1] Wind turbine rotor blade, wherein the wind turbine rotor blade comprises: - a leading edge section with a leading edge; - a trailing edge section with a trailing edge; - a pressure-side surface and a suction-side surface extending from the leading edge portion and meeting at the trailing edge portion; and - an aerodynamic structure for noise reduction provided at the trailing edge portion, the aerodynamic structure comprising a plurality of pressure communication channels between the suction-side surface and the pressure-side surface; - a camber line connecting the leading edge portion and the trailing edge portion and located midway between the pressure-side surface and the suction-side surface, the camber line of the aerodynamic structure being inclined towards the suction-side surface with respect to a camber line of the remaining part of the wind turbine rotor blade. [2] Wind turbine rotor blade according to claim 1, wherein the camber line of the aerodynamic structure is inclined towards the suction-side surface at an angle of at least 1°, preferably between 1.5 to 10°, preferably between 2 to 5°. [3] Wind turbine rotor blade according to one of claims 1 to 2, wherein the plurality of pressure communication channels comprises a first pressure communication channel and a second pressure communication channel, wherein the first pressure communication channel has an hourglass channel configuration (HGCC) and the second pressure communication channel has the HGCC, wherein the HGCC is formed by: - a first surface formed on the suction-side surface and having a first size, - a second surface formed on the pressure-side surface and having a second size, and - a third minimum surface having a third size formed in the pressure communication channel and disposed between the first surface and the second surface, the third size being smaller than the first size and the second size. [4] A wind turbine rotor blade according to claim 3, wherein the first and second pressure communication channels each have a center line which is a reference line substantially perpendicular to the suction side surface and the pressure side surface. [5] A wind turbine rotor blade according to any one of claims 1 to 3, wherein the first and second pressure communication channels each have a generally continuous inner surface connected to the pressure-side surface and / or the suction-side surface. [6] Wind turbine rotor blade according to one of claims 3 to 5, wherein the plurality of pressure communication channels define a pressure communication channel number density that increases with the direction from the leading edge portion to the trailing edge portion. [7] Wind turbine rotor blade according to one of claims 3 to 6, wherein the first and second sizes are sizes with respect to surfaces, which are preferably formed by a circle having a diameter between 0.5 to 2 millimeters; and / or where the ratio of the surfaces between the third size and the first size is between 1:1 and 1:2, and / or where the ratio of the surfaces between the third size and the second size is between 1:1 and 1:

2. [8] Wind turbine rotor blade according to one of claims 3 to 7, wherein the plurality of pressure communication channels have at least three different sizes of surfaces on the pressure-side surface and / or on the suction-side surface. [9] Wind turbine rotor blade according to one of claims 3 to 8, wherein at least one of the first and second pressure-side communication channels comprises at least one airflow blocking device configured between the suction-side surface and the pressure-side surface, wherein the at least one airflow blocking device is acoustically transparent and the airflow blocking device is preferably located at the third minimum area. [10] Wind turbine rotor blade according to one of claims 3 to 9, wherein the aerodynamic structure is an attachment which is attached to the trailing edge portion of the wind turbine rotor blade, or wherein the aerodynamic structure is formed in one piece as the trailing edge portion of the wind turbine rotor blade. [11] A wind turbine rotor blade according to any one of claims 3 to 10, wherein the aerodynamic structure forms the trailing edge portion and is connected to the remaining part of the wind turbine rotor blade using one or any combination of the following means: (i) a butt joint, (ii) a bushing on the suction side surface, (iii) a bushing on the pressure side surface, (iv) a hinge, (v) a flexible connecting element or (vi) flexible connecting plate elements. [12] Wind turbine rotor blade according to one of claims 3 to 11, wherein the plurality of pressure communication channels are irregularly distributed with at least 3 different distances, preferably with at least 4 different distances, preferably with at least 5 different distances, preferably with at least 6 different distances. [13] A wind turbine rotor blade according to any preceding claim, wherein the most aerodynamic structure further comprises trailing edge serrations. [14] Wind turbine, comprising: - a wind turbine mast, comprising an upper part and a lower part; - a nacelle located at the top of the wind turbine mast; - a rotor hub rotatably mounted on the nacelle; - one or more wind turbine blades according to claim 1 mounted on the rotor hub, the wind turbine blades defining a rotor plane; - a shaft coupled to the rotor hub; and - a generator coupled to the shaft, the generator configured to convert a torque of the shaft into electrical power.

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