Air layer distribution state monitoring device for air layer drag reduction of a ship

Abstract

The present application relates to a kind of air layer distribution state monitoring devices for ship air layer drag reduction, including being arranged in the multiple feature points of ship bottom plate, the feature point is arranged in the middle and both sides of ship bottom plate along ship length direction, the feature point is arranged in the bow of ship bottom and is distributed as escaping radian, the feature point is arranged in the stern of ship bottom and is distributed as with fairing convergence;The fixed base is arranged on ship bottom plate, the bottom end of the automatic lifting rod is fixedly arranged on fixed base, the top of the automatic lifting rod is fixedly arranged on fixed cover by buckle, the viscometer is fixedly arranged on fixed cover, the viscometer is connected with data processing module, the data processing module is respectively connected with automatic lifting rod, GUI interface, the probe is arranged in the bottom of viscometer and located in ship bottom plate.The present application measures the thickness of ship bottom air layer, quantifies the state of ship bottom air layer, improves air layer quality monitoring accuracy, while avoiding the increase of ship additional resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ship and ocean engineering gas drag reduction, more particularly to a gas layer distribution state monitoring device for ship gas layer drag reduction. BACKGROUND

[0002] Gas drag reduction technology attempts to form a uniform and stable gas film between the wet surface of the ship and the water by releasing gas underwater, mainly by changing the effective viscosity and flow state of the fluid near the boundary layer, etc., to achieve the purpose of significantly reducing frictional resistance. When the gas bubbles generated by the gas jet are impacted by the water flow and gravity, some of the gas bubbles will escape from the ship bottom or be annihilated, resulting in the quality of the gas layer on the ship bottom deviating from the ideal state. Effective monitoring of the state of the gas layer on the ship bottom is a prerequisite for correctly controlling the gas jet device and improving the quality of the gas layer on the ship bottom. Currently, traditional visual gas layer monitoring equipment is mainly used in laboratory conditions and is installed on transparent ship bottom plates or pool bottoms.

[0003] In the actual ship sailing state, the light on the ship bottom is dim, and the flow on the ship bottom is complex and variable, making it challenging to observe using traditional visual monitoring equipment. Furthermore, the subjective factors of the naked eye are numerous, and there is a lack of quantitative standards. In addition, the shooting equipment may increase the additional resistance of the ship body, affecting the drag reduction effect. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a gas layer distribution state monitoring device for ship gas layer drag reduction, which utilizes the obvious physical characteristics of the difference in dynamic viscosity of water and air at a certain temperature to measure the thickness of the gas layer on the ship bottom, quantifies the state of the gas layer on the ship bottom, improves the accuracy of gas layer quality monitoring, and avoids the increase in additional resistance of the ship body.

[0005] The technical solution adopted by the present application to solve its technical problem is: a gas layer distribution state monitoring device for ship gas layer drag reduction is constructed, which includes a plurality of characteristic points arranged on the ship bottom plate, the characteristic points are arranged on the middle and both sides of the ship bottom plate along the ship length direction, the characteristic points arranged on the bow of the ship bottom are distributed in a divergent arc shape, and the characteristic points arranged on the stern of the ship bottom are distributed in a shape line converging shape.

[0006] The characteristic points include a viscometer, a probe, an automatic lifting rod, a fixed cover, a fixed base, a water-tight rubber ring, a data processing module, and a GUI interface. The fixed base is arranged on the ship bottom plate, the bottom end of the automatic lifting rod is fixedly arranged on the fixed base, the top end of the automatic lifting rod is fixedly arranged on the fixed cover through buckling, the viscometer is fixedly arranged on the fixed cover, the viscometer is connected with the data processing module, the data processing module is connected with the automatic lifting rod and the GUI interface respectively, the water-tight rubber ring is arranged on the opening of the viscometer installation position in the middle of the fixed base to prevent water flow from entering, and the probe is arranged on the bottom of the viscometer and located on the ship bottom plate.

[0007] According to the above scheme, two or three viscometers are arranged at the feature points.

[0008] According to the above scheme, the air jet is arranged on the ship bottom plate along the ship width direction, and the air jet is arranged in two parts at the bow and the middle of the ship.

[0009] According to the above scheme, the probe is preset at the maximum boundary layer thickness δ of the ship bottom plate, and the boundary layer thickness formula is:

[0010] δ = 0.37L / (Re) 0.2

[0011] Where Re = ρvL / μ,

[0012] Where L is the length of the ship bottom plate, v is the rated speed of the ship, and ρ and μ are the density and dynamic viscosity of water at 20°C, respectively.

[0013] The air layer distribution state monitoring device for ship air layer drag reduction implemented by the present application has the following beneficial effects:

[0014] 1. The viscosity difference between water and air is large, and the existing viscosity measurement technology is mature, so the accuracy of the present application is greatly guaranteed.

[0015] 2. The selection of multiple feature points ensures the overall understanding of the state of the ship bottom air layer, and at the same time, the arrangement of two or three viscometers at each feature point ensures the measurement accuracy of the present application and greatly improves the fault tolerance.

[0016] 3. The numerical results of the ship bottom air layer thickness are combined with the ship speed, sailing state, draft and other data, and the change state of the air layer with time is considered, which is more easy to fundamentally derive the drag reduction law and air layer stability condition, and is beneficial to the development of theoretical research, and then guides the application of the actual ship. BRIEF DESCRIPTION OF DRAWINGS

[0017] The present application will be further described below in conjunction with the drawings and examples, and the drawings are as follows:

[0018] Figure 1 is the viscometer assembly structure diagram of the air layer distribution state monitoring device for ship air layer drag reduction of the present application;

[0019] Figure 2 is the air layer distribution state monitoring device layout diagram of the air layer distribution state monitoring device for ship air layer drag reduction of the present application;

[0020] In the figure: 1, viscometer; 2, probe; 3, fixed cover; 4, fixed base; 5, bolt; 6, watertight rubber ring; 7, automatic lifting rod; 8, ship bottom plate; 9, buckle; 10, air jet; 11, data processing module; 12, GUI interface. DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0022] The present invention's air layer distribution monitoring device for reducing air layer drag on ships includes multiple characteristic points disposed on the ship's bottom plating 8. These characteristic points are located in the center and on both sides of the plating 8 along the ship's length. The characteristic points at the bow of the ship are distributed in a diverging arc, while the characteristic points at the stern of the ship are distributed in a convergent pattern following the mold line. Air jets 10 are disposed along the ship's width, with two jets 10 located at the bow and midship, respectively.

[0023] The characteristic points include a viscometer 1, a probe 2, an automatic lifting rod 7, a fixed cover 3, a fixed base 4, a watertight rubber ring 6, a data processing module 11, and a GUI interface 12. The fixed base 4 is mounted on the bottom plate 8. The bottom end of the automatic lifting rod 7 is fixed to the fixed base 4. The top end of the automatic lifting rod 7 is fixed to the fixed cover 3 via a buckle 9. The viscometer 1 is fixed to the fixed cover 3. The viscometer 1 is connected to the data processing module 11, which is connected to the automatic lifting rod 7 and the GUI interface 12 respectively. A watertight rubber ring 6 is installed at the opening in the middle of the fixed base 4 where the viscometer 1 is installed to prevent water from entering. The probe 2 is located at the bottom of the viscometer 1 and is located on the bottom plate 8. Two or three viscometers 1 are installed at the characteristic points.

[0024] Probe 2 is preset at the maximum boundary layer thickness δ on the bottom of the ship. The empirical formula for boundary layer thickness is:

[0025] δ=0.37L / (Re) 0.2

[0026] Where Re=ρvL / μ,

[0027] Where L is the length of the bottom plate 8, v is the rated speed of the ship, ρ and μ are the density and dynamic viscosity of water at 20°C, respectively.

[0028] like Figure 1 As shown, in a preferred embodiment of the present invention, a plurality of viscometers 1 are included. The viscometers 1 are mounted on an automatic lifting rod 7. The probe 2 is preset at the maximum boundary layer thickness δ of the bottom of the ship. The empirical formula for the boundary layer thickness is:

[0029] δ=0.37L / (Re) 0.2

[0030] Other empirical formulas can also be selected according to actual conditions.

[0031] Where Re = ρvL / μ

[0032] Wherein, L is the length of the bottom plate 8, v is the rated speed of the ship, and p and m are the density and dynamic viscosity of water at 20°C, respectively.

[0033] In the vicinity of the ship bottom boundary layer, the thickness of the air layer is obtained by monitoring the distribution of fluid viscosity, so as to monitor the state of the air layer formed on the ship bottom. When the ship sails at a specific speed, if the air layer drag reduction device is not used, the ship bottom surface is simply in contact with liquid, and the measured dynamic viscosity is close to 1.01 x 10 -3 Pa·s, while the dynamic viscosity coefficient of air is 17.9 x 10 -6 Pa·s. If the ship bottom starts to spray air, the ship bottom will form a gas-liquid two-phase flow, and the dynamic viscosity will be certainly less than that of water. The more uniform and stable the air layer formed, the closer the measured data to the dynamic viscosity of air.

[0034] The length of each lifting of the automatic lifting rod 7 determines the accuracy of the measurement: the shorter the unit lifting length, the longer the entire measurement time, and the higher the accuracy; the longer the unit lifting length, the shorter the entire measurement time, and the lower the accuracy. The probe 2 used in the device is small in volume, has extremely limited influence on the gas-liquid mixed multiphase flow field, and can guarantee the originality and accuracy of the measurement data.

[0035] Assuming that in this example, the ship sails at the rated speed, the atmospheric pressure is 101.325 kPa, the ship bottom temperature is 20°C, and the maximum boundary layer height is 10 mm according to the above empirical formula, the probe 2 is preset at a distance of 10 mm from the ship bottom. At this temperature, if the measured fluid dynamic viscosity is close to the dynamic viscosity of water 1.01 x 10 -3 Pa·s, the automatic lifting rod 7 rises until the measured viscosity is close to the dynamic viscosity of air 17.9 x 10 -6 Pa·s, the length of the top of the probe 2 from the ship bottom is 8 mm, indicating that the air layer thickness at this position is 8 mm; if the top of the probe 2 moves to the ship bottom position, and the measured fluid dynamic viscosity is always close to the viscosity value of water, it indicates that the area of the ship bottom plate 8 is not covered by gas and no air layer is formed. If the measured fluid dynamic viscosity is close to the dynamic viscosity of air 17.9 x 10 -6 Pa·s, the automatic lifting rod 7 descends until the measured dynamic viscosity is close to the dynamic viscosity of water 1.01 x 10 -3 Pa·s, the height of the bottom of the probe 2 from the ship bottom is 12 mm, and the air layer thickness at this position is 12 mm. The height of the probe 2 detection part is known, and the distance from the top to the bottom eliminates the influence of the height of the probe 2 itself on the measurement results. For the probe 2, the vertical direction is downward from top to bottom. If the quantitative lifting distance of the automatic lifting rod 7 is 1 mm each time, the accuracy is 1 mm, and if the quantitative lifting distance is 0.1 mm each time, the air layer thickness value is accurate to 0.1 mm.

[0036] In a preferred embodiment of the present invention, the viscometer 1 requires installation and fixation, including a fixed base 4 and a fixed cover 3. The fixed base 4 is connected to the ship's bottom plate 8 via bolts 5, maintaining the stability of the entire device. An automatic lifting rod 7 is threadedly connected to the fixed base 4 and fixed cover 3, respectively. The automatic lifting rod 7 is secured to the viscometer 1 via a buckle 9, thereby firmly attaching the viscometer 1 and the automatic lifting rod 7 to a specific point. A watertight rubber ring 6 is installed in the middle of the fixed base 4, where the viscometer 1 is mounted, to prevent water ingress.

[0037] like Figure 2 As shown, characteristic points are located in the center and on both sides of the bottom plating 8, distributed sequentially along the length of the ship. Near the bow, characteristic points follow the arc of bubble escape from the bottom. Near midship, bubbles generated by the bow and midship devices converge, requiring more characteristic points. Near the stern, characteristic points converge along the mold line, their specific locations determined by the volume fraction of the bottom air layer from numerical simulations and model experiments for that mold line. Due to the significant difference in viscosity between water and air, measuring the dynamic viscosity of the gas-liquid multiphase flow at these characteristic points provides a more intuitive understanding of the coverage of the bottom air layer. Placing two or three viscometers 1 at each characteristic point increases data accuracy and improves error tolerance.

[0038] The working process of the present invention is as follows:

[0039] When the air jet 10 begins generating an air layer, the device begins operating, transmitting data such as viscosity, air layer thickness, and lift height to the data processing module 11. A visualization interface is also included, allowing the above data to be plotted as needed, facilitating operator observation and assessment of the air layer's condition. The viscometer 1 is mounted on an automatic lift mast 7, with the probe 2 positioned at the height of the ship's bottom boundary layer. The mast 7 records its initial position. Due to the significant difference in dynamic viscosity between water and air at a given temperature, if the measured fluid dynamic viscosity approaches that of water, the mast 7 rises until the top of the probe 2 reaches the ship's bottom, or if the measured viscosity approaches that of air. The distance from the top of the probe 2 to the ship's bottom is the air layer thickness. If the measured fluid dynamic viscosity approaches that of air, the mast 7 descends until the viscosity approaches that of water, at which point the mast 7 stops moving. At this point, the distance from the bottom of the probe 2 to the ship's bottom is the air layer thickness. By setting multiple characteristic points and monitoring the air layer distribution at these points, the air layer coverage of the entire ship's bottom can be directly assessed, providing robust data support for adjusting the jet flow and improving drag reduction efficiency. This device will also continuously monitor the changes in the state of the gas layer over time, providing a reliable basis for maintaining the stability of the drag-reducing gas layer.

[0040] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection of the present application.

Claims

1. An air layer distribution state monitoring device for ship air layer drag reduction, characterized in that: The method comprises a plurality of characteristic points arranged on the bottom plate of the ship, wherein the characteristic points are arranged in the middle and on both sides of the bottom plate along the length direction of the ship, the characteristic points arranged at the bow of the ship bottom are distributed in a divergent arc, and the characteristic points arranged at the stern of the ship bottom are distributed in a convergent manner along the mold line; The characteristic points include a viscometer, a probe, an automatic lifting rod, a fixed cover, a fixed base, a watertight rubber ring, a data processing module and a GUI interface, wherein the fixed base is arranged on the bottom plate of the ship, the bottom end of the automatic lifting rod is fixedly arranged on the fixed base, the top end of the automatic lifting rod is fixedly arranged on the fixed cover by a buckle, the viscometer is fixedly arranged on the fixed cover, the viscometer is connected to the data processing module, the data processing module is respectively connected to the automatic lifting rod and the GUI interface, a watertight rubber ring is arranged at the opening at the viscometer installation position in the middle of the fixed base to prevent water from entering, and the probe is arranged at the bottom of the viscometer and located on the bottom plate of the ship; By monitoring the distribution of fluid viscosity, the thickness of the air layer is obtained, thereby monitoring the state of the air layer formed on the bottom of the ship.

2. The air layer distribution state monitoring device for ship air layer drag reduction according to claim 1 is characterized in that: Two or three viscometers are arranged at the characteristic points.

3. The air layer distribution state monitoring device for ship air layer drag reduction according to claim 1, characterized in that: The bottom plate of the ship is provided with air jets along the width direction of the ship, and two air jets are provided and are respectively located at the bow and the middle of the ship.

4. The air layer distribution state monitoring device for ship air layer drag reduction according to claim 1, characterized in that: The probe is preset at the maximum boundary layer thickness on the bottom of the ship At , the boundary layer thickness formula is: in , Where, L is the length of the bottom plate, is the rated speed of the ship, and are the density and dynamic viscosity of water at 20°C respectively.

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