An arc plasma enhanced grooved turbulent friction drag reduction device and method

Abstract

An arc plasma-enhanced trench turbulent friction drag reduction device is provided, comprising a trench wall (1) and an arc electrode assembly (2). The trench wall (1) is formed by multiple trenches extending along the flow direction and equidistantly distributed along the spanwise direction. The arc electrode assembly (2) is arranged in an array on the trench wall (1). A corresponding drag reduction method is also provided: a sensor is placed in the flow field to collect flow field data and inputs the data into a controller; the controller analyzes the data and selects the working mode and parameters accordingly; the sensor collects flow field data again to gather flow field information after arc discharge; the controller analyzes the data again, measures the surface friction resistance, and compares the change in friction resistance before and after arc discharge. If the expected drag reduction effect is achieved, the operation ends; otherwise, it returns to the second step to select a new working mode or discharge state. This invention combines actively controllable arc plasma discharge with passive trench flow control technology, which can achieve effective drag reduction under complex inflow conditions in actual flight.

Description

Technical Field

[0001] This invention relates to the field of flow control technology, and in particular to a highly adaptable arc plasma-enhanced trench turbulent friction drag reduction device and method. Background Technology

[0002] In the field of aerodynamics, reducing aircraft drag is a perpetual pursuit. For civil aircraft (taking the Boeing 747 as an example), assuming a constant range, every 1% increase in drag will increase annual fuel consumption by approximately 4.5 × 10⁻⁶. 5 For every unit of drag reduction (L), it's equivalent to adding eight passengers. For a typical high-subsonic large aircraft, frictional drag during the cruise phase accounts for about half of the total drag. Since maintaining a large area of ​​laminar flow on the aircraft surface is extremely difficult, turbulent friction drag reduction has become a crucial method for aircraft drag reduction. Reducing aircraft turbulent friction drag can significantly increase flight range and time, reduce environmental pollution and fuel consumption, and lower flight costs, which is of great significance for improving aircraft flight performance and economic efficiency.

[0003] To reduce turbulent frictional drag in aircraft, various flow control methods have been developed. Groove turbulence drag reduction technology is a passive flow control method that involves periodically arranging flow-directing protrusions or grooves along the spanwise direction at the boundary layer wall to control the turbulent structure at the bottom layer, thereby achieving frictional drag reduction. Due to its advantages such as simple structure and zero energy consumption, groove turbulence drag reduction technology has become a research hotspot in turbulence drag reduction technology. However, trench drag reduction still suffers from the following problems, severely limiting its practical application: First, poor adaptability. Since different trench geometric parameters are required to achieve drag reduction at different Reynolds numbers, most trenches can only achieve optimal drag reduction within a very small Reynolds number range. Once the design Reynolds number is deviated due to changes in flight speed, altitude, or weather, the drag reduction effect will decrease significantly, or even increase drag. These changes are unavoidable in actual flight, making it difficult for simple trenches to achieve drag reduction in real-world applications. Second, limited disturbance effect. With increased inflow velocity, the fixed trench spacing cannot match the spacing of the denser turbulent stripe structures, making it difficult to effectively intervene in the turbulent boundary layer, thus losing the drag reduction effect. Therefore, to solve the above-mentioned technical problems of trench drag reduction, new methods need to be invented to improve the adaptability of trench turbulence drag reduction technology and broaden the effective drag reduction Reynolds number range. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an arc plasma enhanced trench turbulent friction drag reduction device, comprising a trench wall 1 and an arc electrode assembly 2. The geometric dimensions of the trench wall 1 and the arc electrode assembly 2 are adaptively designed according to specific application scenarios.

[0005] The trench wall 1 is formed by multiple trenches extending along the flow direction and equidistantly distributed along the spanwise direction; the trench depth h and the trench spanwise width s satisfy:

[0006] h = 8~12δ v (1)

[0007] s = 15~20δ v (2)

[0008] δ v =v / u τ (3)

[0009] Where v is the kinematic viscosity, h is the trench depth, s is the trench width, and δ v For the boundary layer viscous length scale, u τ The boundary layer friction velocity is V-shaped. The bottom of the trench is a flat valley with a certain width, and the highest peak of the trench wall also has a certain width. The trench geometry is designed to be larger than Equation (1-3).

[0010] The arc electrode groups 2 are arranged in an array on the trench wall 1. Depending on their location, they are divided into trench valley bottom electrode groups 21 and trench peak electrode groups 22. The trench valley bottom electrode groups 21 are arranged along the flow direction at the lowest point of the trench wall, while the trench peak electrode groups 22 are arranged along the flow direction at the highest point of the trench wall. The flow direction represents the direction in the plane that is the same as the incoming flow, and the spanwise direction represents the direction in the plane that is perpendicular to the incoming flow. The number of electrode groups at the trench peaks and valleys varies depending on the specific application scenario. The trench valley bottom electrode groups 21 can be arranged in one or multiple spanwise rows. Multiple spanwise rows mean that multiple rows of electrode groups are arranged along the spanwise direction in a single trench valley or a single trench peak. Along the flow direction, they are divided into valley bottom electrode groups 1 (group 211), 2 (group 212), 3 (group 213)... and peak electrode groups 1 (group 221), 2 (group 222), 3 (group 223)..., each... The electrode group consists of P groups of positive and negative electrodes, i.e., 2P electrodes. Each electrode group—the valley electrode group and the peak electrode group—consists of P groups of positive and negative electrodes. For the valley electrode group: the valley electrode group consists of P high-voltage electrodes 2111 and P low-voltage electrodes 2112, arranged sequentially along the flow direction in the order of high-voltage electrode 2111, low-voltage electrode 2112, high-voltage electrode 2111, low-voltage electrode 2112… Each group of positive and negative electrodes includes one high-voltage electrode 2111 and one low-voltage electrode 2112. Arc discharge can be generated between the positive and negative electrodes in each group within the electrode group. The number of electrodes in the electrode group can be changed as needed. When the required single-group discharge length is long, the number of electrodes can be increased accordingly, but the number of electrodes in the electrode group must be even, with cathodes and anodes each accounting for half of the number. The electrode polarities in each electrode group are arranged in the same order.

[0011] The external spacing of an electrode group is defined as the minimum flow distance between two adjacent groups of electrode groups 21 at the bottom of the same trench or between adjacent groups of electrode groups 22 at the peak of the same trench. The internal spacing of an electrode group is defined as the minimum flow distance between two adjacent positive and negative electrode groups within the same electrode group. The electrode spacing is defined as the minimum flow distance between positive and negative electrodes within the same positive and negative electrode group. The internal spacing, external spacing, and electrode spacing of an electrode group are adjusted according to energy requirements and working environment conditions. The external spacing of an electrode group should be greater than the internal spacing, and the internal spacing should be greater than the electrode spacing.

[0012] The high-voltage electrode 2111 and the low-voltage electrode 2112 are connected to the positive and negative terminals of the power supply 3 respectively through wires. The positive terminal is connected to the high-voltage electrode 2111, and the negative terminal is connected to the low-voltage electrode 2112 and grounded, forming a complete discharge circuit.

[0013] In a specific embodiment of the present invention, u τ mainstream speed u ∞ 0.035.

[0014] In another specific embodiment of the present invention, the groove cross-sectional shape is a V-shaped groove with an included angle of 60°.

[0015] In one embodiment of the present invention, the trench wall 1 is made by 3D printing, machining, high-energy beam processing, etching or hot stamping, with ABS photosensitive resin as its raw material.

[0016] In another embodiment of the present invention, the electrode spacing is 0.1 mm to 2 mm; the spacing within the electrode group is 1 mm to 3 mm; and the spacing outside the electrode group is 3 mm to 10 mm.

[0017] In another specific embodiment of the present invention, the electrode spacing is 0.5 mm; the spacing within the electrode group is 1 mm; the spacing outside the electrode group is 3 mm; and the diameters of the high-voltage electrode 2111 and the low-voltage electrode 2112 are 0.1 mm to 0.5 mm.

[0018] A driving circuit is also provided for driving the aforementioned arc plasma enhanced trench turbulent friction drag reduction device. This driving circuit includes a power supply 3, a capacitor 5, a valley main circuit switch 61, a valley variable resistor 62, a valley branch switch 63, a valley electrode group, a valley discharge switch 64, a spike main circuit switch 65, a spike variable resistor 66, a spike branch switch 67, a spike discharge electrode group, and a spike discharge switch 68. The valley electrode group includes a first valley electrode group 211, a second valley electrode group 212, and a third valley electrode group 213, and the valley discharge... Switch 64 includes a valley electrode group 1 switch 641, a valley electrode group 2 switch 642, and a valley electrode group 3 switch 643; peak discharge electrode group includes a peak electrode group 1 switch 221, a peak electrode group 222, and a peak electrode group 3 switch 223; peak discharge switch 68 includes a peak electrode group 1 switch 681, a peak electrode group 2 switch 682, and a peak electrode group 3 switch 683; the valley discharge electrode group and valley discharge switch 64 are collectively referred to as the valley discharge unit, and the peak discharge electrode group and peak discharge switch 68 are collectively referred to as the peak discharge unit;

[0019] The circuit connection relationship of valley discharge is described as follows: Power supply 3 is connected in parallel with capacitor 5; for valley discharge, the positive terminal of power supply 3 is connected in series with valley main circuit switch 61, valley variable resistor 62, valley branch switch 63, and valley discharge unit in sequence, and then grounded; the negative terminal of power supply 3 is grounded; specifically: for valley discharge unit, each valley electrode group is first connected in parallel with the corresponding valley electrode group switch; the four electrodes of valley electrode group 1 211 are connected in parallel with the four switches of valley electrode group 1 switch 641 to form a parallel group; the parallel group 1 includes four parallel components in sequence: the first, second, third, and fourth; the four electrodes of valley electrode group 2 212 are connected in parallel with the four switches of valley electrode group 2 switch 642 to form a parallel group 2; the parallel group 2 includes four parallel components in sequence: the fifth, sixth, seventh, and eighth; the four electrodes of valley electrode group 3 213 are connected in parallel with the four switches of valley electrode group 3 switch 643 to form a parallel group 3; the parallel group 3 includes the ninth, tenth, and twelfth; The eleventh and twelfth parallel components are connected in series. Then, they are connected in series sequentially: the first parallel component of parallel group 1, the fifth parallel component of parallel group 2, and the ninth parallel component of parallel group 3 are connected in series; the second parallel component of parallel group 1, the sixth parallel component of parallel group 2, and the tenth parallel component of parallel group 3 are connected in series; the third parallel component of parallel group 1, the seventh parallel component of parallel group 2, and the eleventh parallel component of parallel group 3 are connected in series; the fourth parallel component of parallel group 1, the eighth parallel component of parallel group 2, and the twelfth parallel component of parallel group 3 are connected in series, forming a valley discharge unit. Multiple valley discharge units are connected in parallel and then connected in series with the valley branch switch 63 in the circuit. Specifically, the free ends of the first, second, third, and fourth parallel components are connected to one end of the four switches connected in parallel within the valley branch switch 63, and the other ends of the four switches are connected to the valley variable resistor 62. The free ends of the ninth, tenth, eleventh, and twelfth parallel components are grounded.

[0020] The circuit connection relationship of the spike discharge is described as follows: The positive terminal of power supply 3 is connected in series with the spike main circuit switch 65, the spike variable resistor 66, the spike branch switch 67, and the spike discharge unit in sequence, and then grounded, and connected to the negative terminal of power supply 3 for grounding; specifically: for the spike discharge unit, each spike electrode group is first connected in parallel with the corresponding spike electrode group switch, and the four electrodes of the first set of spike electrode group 221 are connected in parallel with the four switches of the first set of spike electrode group switch 681 to form parallel group one, and parallel group one is connected in sequence according to The first group includes four parallel components: the 1st, 2nd, 3rd, and 4th. The four electrodes of the second peak electrode group 222 and the four switches of the second peak electrode group switch 682 are connected in parallel to form the second parallel group, which includes four parallel components: the 5th, 6th, 7th, and 8th. The four electrodes of the third peak electrode group 223 and the four switches of the third peak electrode group switch 683 are connected in parallel to form the third parallel group, which includes four parallel components: the 9th, 10th, 11th, and 12th. The components are connected in parallel; then they are connected in series sequentially, that is, the first parallel component of parallel group one, the fifth parallel component of parallel group two, and the ninth parallel component of parallel group three are connected in series in sequence; the second parallel component of parallel group one, the sixth parallel component of parallel group two, and the tenth parallel component of parallel group three are connected in series in sequence; the third parallel component of parallel group one, the seventh parallel component of parallel group two, and the eleventh parallel component of parallel group three are connected in series in sequence; the fourth parallel component of parallel group one, the eighth parallel component of parallel group two, and the... The 12th parallel component of the third parallel group is connected in series to form a spike discharge unit; multiple spike discharge units are connected in parallel and connected in series with the spike branch switch 67 into the circuit. Specifically, the free ends of the 1st, 2nd, 3rd and 4th parallel components are respectively connected to one end of the four switches in parallel within the spike branch switch 67, and the other ends of the four switches are connected to the spike variable resistor 66; the free ends of the 9th, 10th, 11th and 12th parallel components are grounded.

[0021] Furthermore, a method for generating and controlling virtual profiles for drag reduction based on electric arc discharge is provided. This method is based on the aforementioned electric arc plasma enhanced trench turbulent friction drag reduction device. When the electric arc electrode group is not working, the trench plays the role of separating the bottom strip structure of the boundary layer in the flow field, effectively reducing turbulent friction drag at the designed Reynolds number. However, when the Reynolds number changes, the drag reduction effect weakens and disappears. Electric arc plasma discharge can generate gas Joule heating. The heated gas is elongated along the flow direction by the incoming flow and produces a blocking effect in the flow field, thereby forming the effect of "virtual" flow direction ribs. Therefore, by performing electric arc discharge at different positions in the trench, it is possible to achieve trench densification, trench heightening, and other more flexible functions by opening and closing the electric arc at different locations, so as to realize the trench's adaptation to the spatial scale requirements of the turbulent boundary layer at different velocities.

[0022] The discharge modes are divided into the following three types: trench valley discharge, trench peak discharge, and intermittent discharge within trench valley and peak groups.

[0023] Mode 1: Discharge at the bottom of the trench

[0024] All the valley bottom electrode groups 21 in the trench are in a discharge state, generating a virtual arc 4 along the flow direction at the valley bottom, generating a virtual arc peak at the bottom of the trench, achieving the effect of denser trench spacing, providing denser spanwise disturbance to the flow field, and better adapting to the needs of controlling the boundary layer strip structure at high speed.

[0025] Mode 2: Trench Spike Discharge

[0026] All the trench spike electrode groups 22 are in a discharge state, generating a virtual arc 4 at the spike with the same flow direction, further increasing the height and strengthening of the trench spike to adapt to more complex flow conditions, generate stronger disturbance to the flow field, stabilize the strip structure, and reduce frictional resistance; by controlling the magnitude of the discharge current, the intensity of the virtual spike profile can be continuously controlled, thereby adapting to a wider range of flow field conditions.

[0027] Mode 3: Intermittent discharge at the bottom of trenches and within peak groups

[0028] The bottom electrode group 1 (211), bottom electrode group 3 (213), and peak electrode group 1 (221) and peak electrode group 3 (223) located at the bottom of the trough and peak discharge, while the bottom electrode group 2 (212) and peak electrode group 2 (222) are in the closed state, generating a wave-shaped virtual surface along the flow direction. By utilizing the control effect of the wave-shaped surface on the turbulent boundary layer, the drag reduction is further enhanced.

[0029] When the system operates in the above three discharge modes, the circuit control is as follows:

[0030] When the discharge is in mode one, the valley bottom main circuit switch 61 and valley bottom branch switch 63 of the trench valley bottom electrode group 21 are in the closed state, the discharge switch 64 of each discharge unit is in the open state, the peak main circuit switch 65 corresponding to the trench peak electrode group 22 is in the open state, and the valley bottom electrode group discharges.

[0031] In mode two, the peak main circuit switch 65 and peak branch switch 67 of the trench peak electrode group 22 are in the closed state, the discharge switch 68 of each discharge unit is in the open state, the valley main circuit switch 61 corresponding to the trench valley electrode group 21 is in the open state, and the peak electrode group discharges.

[0032] In Mode 3, the valley bottom main circuit switch 61, valley bottom branch switch 63, peak main circuit switch 65, and peak branch switch 67 are all in the closed state, while the discharge switches corresponding to the three sets of discharge units in each branch are in the open, closed, and open states, respectively, forming intermittent discharge. That is, the discharge switches corresponding to the valley bottom electrode group 1 211, valley bottom electrode group 3 213, and peak electrode group 1 221 and peak electrode group 3 223 located at the bottom of the trench and the peak are open, while the discharge switches corresponding to the valley bottom electrode group 212 and peak electrode group 222 are closed, forming intermittent discharge within the valley bottom and peak electrode group.

[0033] Furthermore, during implementation, by controlling the resistance value of the variable resistor 62, the current and intensity of the arc discharge can be continuously adjusted, thereby continuously adjusting the height of the virtual rib to further adapt to the drag reduction requirements.

[0034] In addition, an arc plasma-enhanced trench turbulent friction drag reduction method is also provided, which is based on the above-mentioned arc plasma-enhanced trench turbulent friction drag reduction device and the above-mentioned method for generating and controlling the drag reduction virtual profile based on arc discharge, as detailed below:

[0035] Step S1: The sensor collects flow field data. The sensor is placed in the flow field to collect information such as temperature, pressure, velocity, and wall shear stress in the flow field in real time, and inputs the data into the controller.

[0036] Step S2: The data collected by the sensor is analyzed in the controller. The specific analysis method is described later. Based on this, the appropriate working mode and parameters are selected through the control circuit: Mode 1 S21, Mode 2 S22, Mode 3 S23, or no operation S24. The controller can determine the required discharge strategy according to equation (1-3). If the trench spacing s when not discharging is > 15~20δ v , where δ v To test the obtained boundary layer viscous length scale, mode S21 can be used to actively refine the trenches; if the trench height h without discharge is < 8~12δ v In this case, mode 2 S22 can be used to actively raise the trench; at the same time, mode 3 S23 can be used depending on the specific situation to obtain a better drag reduction effect.

[0037] Step S3: The sensor collects flow field data again to gather flow field information after arc discharge;

[0038] In step S4, the data collected by the sensors is analyzed again in the controller using software. Surface friction resistance is measured using surface shear stress sensors such as hot-film sensors. The change in friction resistance measured before and after arc discharge is compared. If the measured friction resistance is less than the friction resistance before arc discharge, the expected drag reduction effect is achieved, and the operation ends. Otherwise, a new working mode or a new discharge state is selected again from step S2 based on the flow field information. The discharge intensity of each discharge mode is adjustable and changeable.

[0039] This invention addresses the problems of passive drag reduction methods using trenches, such as the inability to change the trench spacing leading to flow field deviations from the design state, and the limited effect of disturbance on the flow field, making effective drag reduction difficult at high speeds. It combines actively controllable arc plasma discharge with passive trench flow control technology. The thermal blocking effect generated by the arc discharge forms virtual ribs, allowing the spanwise spacing and normal height of the trenches to be adjusted in real time according to the flow field conditions during flight, thus adapting to the need to reduce frictional drag. Furthermore, the flexible control of plasma discharge can also create virtual wavy walls along the flow direction. The wavy walls' control over the turbulent boundary layer further enhances the drag reduction effect, thus forming a novel, highly adaptable active-passive combined turbulence drag reduction control method that achieves effective drag reduction under complex inflow conditions during actual aircraft flight. Attached Figure Description

[0040] Figure 1 A schematic diagram of the overall structure of the device of the present invention is shown, wherein... Figure 1 (a) shows an isometric view of the device of the present invention. Figure 1 (a) shows a top view of the device of the present invention;

[0041] Figure 2 A top view and a cross-sectional view of the device of the present invention are shown;

[0042] Figure 3 The circuit diagram of the device of the present invention is shown;

[0043] Figure 4 This illustrates a specific embodiment of the present invention;

[0044] Figure 5 The diagram shows the discharge effect of Mode 1, in which... Figure 5 (a) shows a cross-sectional view of the discharge effect in Mode 1. Figure 5 (b) An isometric view of the discharge effect in Mode 1 is shown;

[0045] Figure 6 The diagram shows the discharge effect of mode two, in which... Figure 6 (a) shows a cross-sectional view of the discharge effect in Mode 2. Figure 6(b) shows an isometric view of the discharge effect in Mode 2;

[0046] Figure 7 A schematic diagram of the discharge effect in Mode 3 is shown;

[0047] Figure 8 A flowchart of the drag reduction method of the device of the present invention is shown;

[0048] Figure 9 The diagram shows the relationship of the drag reduction device.

[0049] Attached image annotations:

[0050] 1. Trench wall

[0051] 2 Arc electrode group 21 Trench valley bottom electrode group 211 Valley bottom electrode group one 2111 High voltage electrode 2112 Low voltage electrode 212 Valley bottom electrode group two 213 Valley bottom electrode group three 22 Trench peak electrode group 221 Peak electrode group one 222 Peak electrode group two 223 Peak electrode group three

[0052] 3 power supplies

[0053] 4. Electric arc

[0054] 5 capacitors

[0055] 61 Valley bottom main circuit switch; 62 Valley bottom variable resistor; 63 Valley bottom branch switch; 64 Valley bottom discharge switch; 641 Valley bottom electrode group 1 switch; 642 Valley bottom electrode group 2 switch; 643 Valley bottom electrode group 3 switch; 65 Peak main circuit switch; 66 Peak variable resistor; 67 Peak branch switch; 68 Peak discharge switch; 681 Peak electrode group 1 switch; 682 Peak electrode group 2 switch; 683 Peak electrode group 3 switch Detailed Implementation

[0056] The arc plasma enhanced trench turbulence friction reduction device includes a trench wall 1 and an arc electrode assembly 2, such as Figure 1 , 2 As shown. The geometry of the trench wall 1 and the arc electrode assembly 2 needs to be adaptively designed according to the specific application scenario. Figure 1 In a specific implementation example, the trench wall 1 is formed by multiple trenches extending along the flow direction and equidistantly distributed along the spanwise direction. Generally speaking, for ordinary trenches, to achieve a good drag reduction effect, the trench depth h and the trench spanwise width s (e.g., Figure 2 (As shown in section CC) must satisfy:

[0057] h = 8~12δ v (1)

[0058] s = 15~20δ v (2)

[0059] δ v =v / u τ (3)

[0060] Where v is the kinematic viscosity, h is the trench depth, s is the trench width, and δ v For the boundary layer viscous length scale, u τ Let u be the boundary layer friction velocity. τ The mainstream speed is u. ∞ The effective Reynolds number is approximately 0.035, therefore, as the mainstream velocity increases, the viscous length scale decreases, and the trench spacing must also decrease accordingly to achieve a better drag reduction effect. In this embodiment, the trench cross-section is a V-shaped trench with an included angle of 60°. The bottom of the trench is a flat valley with a certain width, and the highest point (peak) of the trench wall also has a certain width. The trench geometry is designed to be relatively large according to formulas (1-3) to facilitate subsequent densification using arc discharge, thereby increasing the effective Reynolds number range and enhancing adaptability, while making the effective Reynolds number range closer to the target incoming flow velocity range. The trench wall 1 can be manufactured by 3D printing, machining, high-energy beam processing, etching, and hot stamping, with ABS photosensitive resin being the preferred raw material.

[0061] The arc electrode group 2 is arranged in an array on the trench wall 1. Depending on the arrangement position, it is divided into trench valley electrode group 21 and trench peak electrode group 22. The trench valley electrode group 21 is arranged along the flow direction at the lowest point (valley) of the trench wall, and the trench peak electrode group 22 is arranged along the flow direction at the highest point (peak) of the trench wall. The flow direction represents the direction in the plane that is the same as the incoming flow, and the spanwise direction represents the direction in the plane that is perpendicular to the incoming flow. The number of electrode groups at the trench peaks and valleys can be changed according to the specific application scenario. The trench valley electrode group 21 can be a single row or multiple rows spanwise. Figure 1 (The case of a single row in the spanwise direction is shown in the middle). Multiple rows in the spanwise direction refer to multiple rows of electrode groups arranged along the spanwise direction within a trench valley or a trench peak. Figure 1-2In the implementation example, along the flow direction, there are two electrode groups: Valley Electrode Group 1 (211), Valley Electrode Group 2 (212), Valley Electrode Group 3 (213), etc., and Peak Electrode Group 1 (221), Peak Electrode Group 2 (222), Peak Electrode Group 3 (223), etc. (Only three electrode groups are shown in the figure; in reality, there may be more groups). Each dot in the figure represents one electrode. Each electrode group includes two subgroups of positive and negative electrodes, i.e., four electrodes (four dots). Each electrode group (valley electrode group and peak electrode group) includes two subgroups of positive and negative electrodes. Taking the valley electrode group as an example, the valley electrode group consists of two high-voltage electrodes 2111 and two low-voltage electrodes 2112, arranged sequentially along the flow direction in the order of high-voltage electrode 2111, low-voltage electrode 2112, high-voltage electrode 2111, low-voltage electrode 2112. Each subgroup of positive and negative electrodes includes one high-voltage electrode and one low-voltage electrode, for example, high-voltage electrode 2111 and low-voltage electrode 2112. Arc discharge can occur between the positive and negative electrodes in each subgroup within the electrode group. In other embodiments, the number of electrodes in the electrode group can also be changed as needed. When the required single discharge length is long, the number of electrodes can be increased accordingly. However, the number of electrodes in the electrode group must be even, with the cathode and anode each accounting for half of the number. The electrode polarities of each electrode group are arranged in the same order. Figure 1-2 Only the representative row of trench bottom electrode group 21 and the row of trench peak electrode group 22 are labeled. The electrode groups in other trench locations also belong to the above two types, and for the sake of simplicity, they are not labeled.

[0062] The external spacing of an electrode group is defined as the minimum flow distance between two adjacent groups of electrode groups 21 at the bottom of the same trench or adjacent groups of electrode groups 22 at the peak of the same trench. The internal spacing of an electrode group is the minimum flow distance between two adjacent positive and negative electrode groups within the same electrode group. The electrode spacing is the minimum flow distance between positive and negative electrodes within a single positive and negative electrode group. The internal spacing, external spacing, and electrode spacing of an electrode group can be adjusted according to energy requirements and working environment conditions. The external spacing of an electrode group should be greater than the internal spacing, and the internal spacing should be greater than the electrode spacing. The electrode spacing can be 0.1mm to 2mm, preferably 0.5mm. The internal spacing of an electrode group can be 1mm to 3mm, preferably 1mm. The external spacing of an electrode group can be 3mm to 10mm, preferably 3mm.

[0063] The high-voltage electrode 2111 and the low-voltage electrode 2112 can be made of conductive metals such as copper, silver, or tungsten (the electrode diameter can be 0.1mm to 0.5mm, preferably a tungsten needle with a diameter of 0.2mm, but copper wire can also be used). The high-voltage electrode 2111 and the low-voltage electrode 2112 are connected to the positive and negative terminals of the power supply 3 respectively through wires, wherein the positive terminal is connected to the high-voltage electrode 2111, and the negative terminal is connected to the low-voltage electrode 2112 and grounded, forming a complete discharge circuit. This invention does not limit the frequency and voltage range of the power supply driving waveform, as long as it can break down the air to generate an electric arc plasma.

[0064] use Figure 3 The circuit shown drives the device of the present invention to discharge, including a power supply 3, a capacitor 5, a valley main circuit switch 61, a valley variable resistor 62, a valley branch switch 63, a valley electrode group (e.g., including a valley electrode group 1 211, a valley electrode group 212, and a valley electrode group 3 213), a valley discharge switch 64 (e.g., including a valley electrode group 1 switch 641, a valley electrode group 2 switch 642, and a valley electrode group 3 switch 643), a peak main circuit switch 65, a peak variable resistor 66, a peak branch switch 67, a peak discharge electrode group (e.g., including a peak electrode group 1 221, a peak electrode group 222, and a peak electrode group 3 223), and a peak discharge switch 68 (e.g., including a peak electrode group 1 switch 681, a peak electrode group 2 switch 682, and a peak electrode group 3 switch 683). The valley discharge electrode assembly and valley discharge switch 64 are collectively referred to as the valley discharge unit, and the spike discharge electrode assembly and spike discharge switch 68 are collectively referred to as the spike discharge unit. Because the circuit components are very small and lightweight, they can be attached to the internal surface of the aircraft skin below the drag reduction area.

[0065] The circuit connection is described as follows. Power supply 3 is connected in parallel with capacitor 5. For valley discharge, the positive terminal of power supply 3 is connected in series with valley main circuit switch 61, valley variable resistor 62, valley branch switch 63, and valley discharge unit, and then grounded. The negative terminal of power supply 3 is grounded. Specifically, for the valley discharge unit, each valley electrode group is first connected in parallel with the corresponding valley electrode group switch. For example, the four electrodes of valley electrode group 1 211 are connected in parallel with the four switches of valley electrode group 1 switch 641 to form a parallel group 1, which includes four parallel components in sequence: the first, second, third, and fourth. The four electrodes of valley electrode group 2 212 are connected in parallel with the four switches of valley electrode group 2 switch 642 to form a parallel group 2, which includes four parallel components in sequence: the fifth, sixth, seventh, and eighth. The four electrodes of valley electrode group 3 213 are connected in parallel with the four switches of valley electrode group 3 switch 643 to form a parallel group 3, which includes four parallel components in sequence: the ninth, tenth, eleventh, and twelfth. Then, they are connected in series sequentially: the first parallel component of parallel group 1, the fifth parallel component of parallel group 2, and the ninth parallel component of parallel group 3 are connected in series; the second parallel component of parallel group 1, the sixth parallel component of parallel group 2, and the tenth parallel component of parallel group 3 are connected in series; the third parallel component of parallel group 1, the seventh parallel component of parallel group 2, and the eleventh parallel component of parallel group 3 are connected in series; and the fourth parallel component of parallel group 1, the eighth parallel component of parallel group 2, and the twelfth parallel component of parallel group 3 are connected in series, forming a valley discharge unit. Multiple valley discharge units are connected in parallel and then connected in series with the valley branch switch 63 in the circuit. Specifically, the free ends of the first, second, third, and fourth parallel components are connected to one end of the four switches connected in parallel within the valley branch switch 63, and the other ends of the four switches are connected to the valley variable resistor 62. The free ends of the ninth, tenth, eleventh, and twelfth parallel components are grounded.

[0066] For peak discharge, the connection method is exactly the same as for valley discharge. The positive terminal of power supply 3 is connected in series with peak main circuit switch 65, peak variable resistor 66, peak branch switch 67, and peak discharge unit, and then grounded, and connected to the negative terminal of power supply 3 and grounded. Specifically, for the peak discharge unit, each peak electrode group is first connected in parallel with the corresponding peak electrode group switch. For example, the four electrodes of peak electrode group 221 and the four switches of peak electrode group 681 are connected in parallel to form parallel group one, which includes four parallel components in sequence: the 1st, 2nd, 3rd, and 4th. The four electrodes of peak electrode group 222 and the four switches of peak electrode group 2 are connected in parallel to form parallel group two, which includes four parallel components in sequence: the 5th, 6th, 7th, and 8th. The four electrodes of peak electrode group 223 and the four switches of peak electrode group 3 are connected in parallel to form parallel group three, which includes four parallel components in sequence: the 9th, 10th, 11th, and 12th. Then, they are connected in series sequentially: the first parallel component of parallel group one, the fifth parallel component of parallel group two, and the ninth parallel component of parallel group three are connected in series; the second parallel component of parallel group one, the sixth parallel component of parallel group two, and the tenth parallel component of parallel group three are connected in series; the third parallel component of parallel group one, the seventh parallel component of parallel group two, and the eleventh parallel component of parallel group three are connected in series; and the fourth parallel component of parallel group one, the eighth parallel component of parallel group two, and the twelfth parallel component of parallel group three are connected in series, forming a spike discharge unit. Multiple spike discharge units are connected in parallel and then connected in series with the spike branch switch 67 in the circuit. Specifically, the free ends of the four parallel components (first, second, third, and fourth) are connected to one end of the four switches that are connected in parallel within the spike branch switch 67, and the other ends of the four switches are connected to the spike variable resistor 66. The free ends of the four parallel components, numbered 9, 10, 11, and 12, are grounded.

[0067] Power supply 3 is an adjustable high-voltage DC power supply (0-10kV) serving as the power supply for the entire device. Capacitor 5 acts as an energy storage device in the circuit, working with the high-voltage DC power supply to form pulsed discharge. The closing of the valley bottom main circuit switch 61 and the peak main circuit switch 65 enables the discharge switch control of the trench valley bottom electrode group 21 or the trench peak electrode group 22. The valley bottom variable resistor 62 and the peak variable resistor 66 protect power supply 3 and stabilize the pulse current. The valley bottom branch switch 63 is used to control the electrode groups arranged in a longitudinal array at the bottom of the trench. Each branch includes three sets of discharge units arranged in the flow direction and corresponding discharge switches, namely valley bottom electrode group 1 211, valley bottom electrode group 212, valley bottom electrode group 3 213 and corresponding discharge switches 64 (valley bottom electrode group 1 switch 641, valley bottom electrode group 2 switch 642 and valley bottom electrode group 3 switch 643). The discharge switches can be used to control the discharge of each electrode group. The functions and principles of the components in the peak branch are similar to those in the valley branch, so they will not be described further here.

[0068] The implementation method of the above-mentioned highly adaptable arc plasma enhanced trench turbulent friction drag reduction device is as follows: Figure 4 As shown. When the arc electrode assembly is not working, the trenches act as separators for the bottom strip structure of the boundary layer in the flow field, effectively reducing turbulent frictional drag at the designed Reynolds number. However, when the Reynolds number changes, the drag reduction effect weakens and disappears. Arc plasma discharge can generate Joule heating of the gas. The heated gas is elongated along the flow direction by the incoming flow and creates a blocking effect in the flow field, thus forming a "virtual" flow-direction rib effect. Therefore, by performing arc discharge at different locations in the trench, it is possible to achieve trench densification, trench heightening, and other more flexible functions by opening and closing the arc at different locations, so as to adapt the trenches to the spatial scale requirements of the turbulent boundary layer at different velocities.

[0069] Discharge modes can be divided into the following three types: trench valley discharge, trench peak discharge, and intermittent discharge within trench valley and peak groups, such as... Figure 4 As shown.

[0070] Mode 1 trench bottom discharge, such as Figure 5 As shown, all the valley bottom electrode groups 21 in the trench are in a discharged state, generating a virtual arc 4 along the flow direction at the valley bottom. This creates a virtual arc peak at the bottom of the trench, achieving a denser trench spacing and providing denser spanwise disturbances to the flow field, better meeting the requirements for controlling the boundary layer strip structure at high speeds. This embodiment only shows the case of a single row of spanwise valley bottom electrodes. In reality, multiple rows of spanwise trench valley bottom electrodes can also be set, i.e., multiple rows of spanwise valley bottom electrodes can be arranged at the bottom of a single trench, thereby generating multiple virtual arc peaks. In the case of multiple rows, one row or several rows with uniform spacing can be selected for discharge, thus achieving different spanwise spacings.

[0071] Mode 2 trench spike discharge, such as Figure 6 As shown, all the trench spike electrode groups 22 are in a discharge state at this time, generating a virtual arc 4 shape along the flow direction at the spike, further increasing the height and strength of the trench spike to adapt to more complex flow conditions, generate stronger disturbance to the flow field, stabilize the strip structure, and reduce frictional resistance. By controlling the magnitude of the discharge current, the intensity of the virtual spike shape can be continuously controlled, thereby adapting to a wider range of flow field conditions.

[0072] Mode 3: Intermittent discharge within the trench valley and peak group. Figure 7 As shown, the first set of valley electrode group 211, the third set of valley electrode group 213, and the first set of peak electrode group 221 and the third set of peak electrode group 223, located at the bottom of the trough and the peak, are discharging, while the second set of valley electrode group 212 and the second set of peak electrode group 222 are in a closed state. This generates a wave-like virtual surface along the flow direction. By utilizing the control effect of the wave-like surface on the turbulent boundary layer, drag reduction is further enhanced. This embodiment only shows the case of discharging with one set of electrodes intermittently. In actual implementation, multiple sets of electrodes can be discharged intermittently to achieve different wavelengths of the virtual wave-like surface, adapting to more drag reduction scenarios. In addition, by controlling the discharge state of electrode groups at different positions, more different modes of discharge effects can be achieved, which will not be described in detail here.

[0073] When the system operates in the above three discharge modes, the circuit control is as follows. In mode one, the valley bottom main circuit switch 61 and valley bottom branch switch 63 of the trench valley bottom electrode group 21 are closed, the discharge switch 64 of each discharge unit is open, and the peak main circuit switch 65 corresponding to the trench peak electrode group 22 is open, allowing the valley bottom electrode group to discharge. In mode two, the peak main circuit switch 65 and peak branch switch 67 of the trench peak electrode group 22 are closed, the discharge switch 68 of each discharge unit is open, and the valley bottom main circuit switch 61 corresponding to the trench valley bottom electrode group 21 is open, allowing the peak electrode group to discharge. In mode three… The valley bottom main circuit switch 61, valley bottom branch circuit switch 63, peak main circuit switch 65, and peak branch circuit switch 67 are all in the closed state. Meanwhile, the discharge switches corresponding to the three sets of discharge units in each branch are in the open, closed, and open states, respectively, forming intermittent discharge. Specifically, the discharge switches corresponding to the valley bottom electrode group 1 (211), valley bottom electrode group 3 (213), and peak electrode group 1 (221) and peak electrode group 3 (223) located at the valley bottom and peak are open, while the discharge switches corresponding to the valley bottom electrode group 2 (212) and peak electrode group 2 (222) are closed, forming intermittent discharge within the valley bottom and peak electrode groups. Furthermore, during implementation, by controlling the resistance value of the variable resistor 62, the current and intensity of the arc discharge can be continuously adjusted, thereby continuously adjusting the height of the virtual ribs to further adapt to the drag reduction requirements.

[0074] To better demonstrate the advantages of the present invention, a drag reduction method based on the above-described device is further described below, such as... Figure 8 and Figure 9 As shown.

[0075] Step S1: The sensor collects flow field data. The sensor is placed in the flow field to collect information such as temperature, pressure, velocity, and wall shear stress in the flow field in real time, and inputs the data into the controller.

[0076] Step S2: The controller analyzes the data collected by the sensor. The specific analysis method is described in the following paragraph. Based on this, the control circuit selects the appropriate operating mode and parameters: Mode 1 (S21), Mode 2 (S22), Mode 3 (S23), or no operation (S24). The controller can determine the required discharge strategy according to equation (1-3). If the trench spacing s when not discharging is > 15~20δ... v , where δ v To test the obtained boundary layer viscous length scale, mode one S21 can be used to actively refine the trenches; if the trench height h when not discharging is < 8~12δ v In this case, mode 2 S22 can be used to actively raise the trench; at the same time, mode 3 S23 can be used depending on the specific situation to obtain a better drag reduction effect.

[0077] Specifically, in one embodiment of the present invention, based on the mainstream velocity u measured by the sensor... ∞ Take the friction speed u τ =0.035u ∞ Then, the boundary layer viscous length scale δ is calculated based on equation (3). v This allows us to determine whether the current trench height h is between 8 and 12δ. v Between, if the trench height h is less than 8δ v If the trench spike discharge (mode 2 S22) is performed, or the resistance of the spike variable resistor 66 is reduced to increase the arc current on the spike, thereby enhancing the discharge and strengthening the virtual ribs on the spike; conversely, if the trench height h is greater than 12δ v If the resistance of the peak variable resistor 66 is increased, the arc current on the peak will decrease, the discharge will weaken, the virtual ribs on the peak will weaken, or the trench peak discharge will stop (Mode 2 S22). Then determine whether the trench width s is within 15-20δ. v Between, if the trench width s is greater than 20δ v If the trench valley discharge (mode 1 S21) is performed, virtual ribs are generated at the valley bottom, or the number of rows of trench valley discharge is increased, the trench width is reduced, and the density is increased; conversely, if the trench width s is less than 15δ vIf the discharge at the bottom of the trench is stopped (mode 1 S21), the virtual ribs at the bottom of the trench will disappear, or the number of rows of discharge at the bottom of the trench will be reduced, the trench width will be increased, and the density will be reduced, so that the trench parameters are always in the optimal state under different flow field parameters, and the best drag reduction effect will be achieved.

[0078] Step S3: The sensor collects flow field data again to gather flow field information after arc discharge.

[0079] Step S4: The data collected by the sensors is analyzed again in the controller using software. Here, a surface shear stress sensor, such as a hot-film sensor (publication number: CN111351609A), is used to measure the surface frictional resistance. The change in frictional resistance before and after the arc discharge is compared. If the measured frictional resistance is less than that before the arc discharge, the expected drag reduction effect is achieved, and the operation ends. Otherwise, a new operating mode or a new discharge state is selected starting from step S2 based on the flow field information. The discharge intensity of each discharge mode is adjustable and changeable.

[0080] The above working method can enhance the adaptability of the trench by utilizing arc plasma discharge. In actual flight, the sensor detects changes in the incoming flow state and then actively adjusts the working mode and intensity of the arc discharge. By changing parameters such as trench depth, spacing, and wave surface wavelength through virtual surface, it can adapt to the current incoming flow conditions in real time and achieve better drag reduction effect.

[0081] From the above description of the working method and structure, it is easy to see that the advantages and effects of this invention are mainly as follows:

[0082] 1. High adaptability. This invention combines electric arc plasma discharge and trenching to achieve a novel flow control method that combines active and passive approaches. Compared with traditional trench drag reduction methods, it effectively improves the problems of poor adaptability and limited disturbance intensity of traditional trenches, broadens the effective drag reduction wind speed range of trench drag reduction, and adapts to more incoming flow conditions.

[0083] 2. Rapid Response. Because the arc electrode assembly of this invention can be controlled by a power supply signal, compared to other turbulence drag reduction devices such as wall blowing and spanwise wall oscillation, the response time is greatly shortened, generating a discharge effect within microseconds and achieving a rapid response to the flow field. This rapid response capability allows the invention to reach its optimal design state more quickly, achieving better drag reduction effects. It also makes it possible to combine this invention with various intelligent control methods such as deep reinforcement learning.

[0084] 3. Diverse drag reduction mechanisms and strong capabilities. Compared with general flow control methods, the device provided by this invention combines array-type plasma arc discharge and trenches, along with multiple operating modes and discharge intensities, to achieve multi-scale coupling with the boundary layer. It proposes a novel flow control method with variable flow wavelength, adjustable spanwise spacing, and adjustable normal height. It can fully utilize multiple turbulence drag reduction mechanisms such as spanwise trenches and flow-oriented wavy walls to reduce frictional resistance from multiple angles, thereby achieving better drag reduction results.

Claims

1. An arc plasma-enhanced trench turbulent friction drag reduction device, characterized in that, The system includes a trench wall (1) and an arc electrode assembly (2). The geometric dimensions of the trench wall (1) and the arc electrode assembly (2) are adaptively designed according to the specific application scenario. The trench wall (1) is formed by multiple trenches extending along the flow direction and equidistantly distributed along the spanwise direction; the trench depth h and the trench spanwise width s satisfy: h=8~12d v (1) s=15~20δ v (2) δ v =v / u τ (3) Where v is the kinematic viscosity, h is the trench depth, s is the trench width, and δ v For the boundary layer viscous length scale, u τ This refers to the boundary layer friction velocity; The trench has a V-shaped profile, with a flat valley bottom of a certain width at the bottom and a peak at the highest point of the trench wall of a certain width. The trench's geometric dimensions are designed to be larger than those in Equations (1) to (3). The arc electrode group (2) is arranged in an array on the trench wall (1). According to the different arrangement positions, it is divided into the trench valley bottom electrode group (21) and the trench peak electrode group (22). The trench valley bottom electrode group (21) is arranged along the flow direction at the lowest point of the trench wall, and the trench peak electrode group (22) is arranged along the flow direction at the highest point of the trench wall. The flow direction represents the direction in the plane that is the same as the incoming flow, and the spanning direction represents the direction in the plane that is perpendicular to the incoming flow. The number of electrode groups at the trench peak and valley bottom is changed according to the specific application scenario. The trench valley bottom electrode group (21) can be a single row or multiple rows in the spanning direction. Multiple rows in the spanning direction means that multiple rows of electrode groups are arranged along the spanning direction in a trench valley bottom or a trench peak. Along the flow direction, it is divided into one group (211), two groups (212), three groups (213)... and one group (221), two groups (222), three groups (223) of the peak electrode group. ..., each electrode group includes P groups of positive and negative electrodes, i.e., 2P electrodes. Each electrode group - valley electrode group and peak electrode group - includes P groups of positive and negative electrodes. For the valley electrode group: the valley electrode group consists of P high-voltage electrodes (2111) and P low-voltage electrodes (2112), arranged in the order of high-voltage electrode (2111), low-voltage electrode (2112), high-voltage electrode (2111), low-voltage electrode (2112)... along the flow direction. Each group of positive and negative electrodes includes one high-voltage electrode (2111) and one low-voltage electrode (2112). Arc discharge can be generated between the positive and negative electrodes in each group of electrodes. The number of electrodes in the electrode group can be changed as needed. When the required single-group discharge length is long, the number of electrodes can be increased accordingly, but the number of electrodes in the electrode group must be even, with the cathode and anode each accounting for half of the number. The electrode polarity of each electrode group is arranged in the same order. The electrode group spacing outside the group is defined as the minimum flow distance between two adjacent groups of bottom electrode groups (21) at the bottom of the same trench or between adjacent peak electrode groups (22) at the same peak of the same trench. The electrode group spacing inside the group is defined as the minimum flow distance between two adjacent positive and negative electrode groups within the same electrode group. The electrode spacing is defined as the minimum flow distance between positive and negative electrodes within the same positive and negative electrode group. The electrode group spacing inside the group, the electrode group spacing outside the group, and the electrode spacing are adjusted according to energy requirements and working environment conditions. The electrode group spacing outside the group should be greater than the electrode group spacing, and the electrode group spacing inside the group should be greater than the electrode spacing. The high-voltage electrode (2111) and the low-voltage electrode (2112) are connected to the positive and negative terminals of the power supply (3) respectively through wires. The positive terminal is connected to the high-voltage electrode (2111), and the negative terminal is connected to the low-voltage electrode (2112) and grounded, forming a complete discharge circuit.

2. The arc plasma enhanced trench turbulent friction drag reduction device as described in claim 1, characterized in that, u τ mainstream speed u ∞ 0.

035.

3. The arc plasma enhanced trench turbulent friction drag reduction device as described in claim 1, characterized in that, The trench cross-section is a V-shaped trench with an included angle of 60°.

4. The arc plasma enhanced trench turbulent friction drag reduction device as described in claim 1, characterized in that, The trench wall (1) is made by 3D printing, machining, high-energy beam processing, etching or hot stamping, with ABS photosensitive resin as its raw material.

5. The arc plasma enhanced groove turbulent friction drag reduction device as described in claim 1, characterized in that, The electrode spacing is 0.1mm to 2mm; the spacing within an electrode group is 1mm to 3mm; and the spacing between electrodes outside an electrode group is 3mm to 10mm.

6. The arc plasma enhanced trench turbulent friction reduction device as described in claim 5, characterized in that, The electrode spacing is 0.5 mm; the spacing within the electrode group is 1 mm; the spacing between the electrodes outside the electrode group is 3 mm; the diameter of the high-voltage electrode (2111) and the low-voltage electrode (2112) is 0.1 mm to 0.5 mm.

7. A driving circuit for driving the arc plasma enhanced trench turbulent friction reduction device as described in any one of claims 1 to 6, characterized in that, The drive circuit includes a power supply (3), a capacitor (5), a valley main circuit switch (61), a valley variable resistor (62), a valley branch switch (63), a valley electrode group, a valley discharge switch (64), a peak main circuit switch (65), a peak variable resistor (66), a peak branch switch (67), a peak discharge electrode group, and a peak discharge switch (68); wherein, the valley electrode group includes a first valley electrode group (211), a second valley electrode group (212), and a third valley electrode group (213), and the valley discharge switch (64) includes a first valley electrode group switch ( 641), Valley electrode group two switches (642) and Valley electrode group three switches (643), Peak discharge electrode group includes Peak electrode group one (221), Peak electrode group two (222) and Peak electrode group three (223), Peak discharge switch (68) includes Peak electrode group one switch (681), Peak electrode group two switches (682) and Peak electrode group three switches (683); Valley discharge electrode group and valley discharge switch (64) are collectively referred to as valley discharge unit, Peak discharge electrode group and peak discharge switch (68) are collectively referred to as peak discharge unit; The circuit connection relationship of valley discharge is described as follows: the power supply (3) is connected in parallel with the capacitor (5); for valley discharge, the positive terminal of the power supply (3) is connected in series with the valley main circuit switch (61), the valley variable resistor (62), the valley branch switch (63), and the valley discharge unit in sequence, and then grounded, and the negative terminal of the power supply (3) is grounded; specifically: for the valley discharge unit, each valley electrode group is first connected in parallel with the corresponding valley electrode group switch, and the four electrodes of the valley electrode group group (211) are connected to the valley electrode group group switch (641) The four switches of the valley electrode group (212) are connected in parallel to form a parallel group, which includes four parallel components in sequence: the first, the second, the third, and the fourth. The four electrodes of the valley electrode group (212) and the four switches of the valley electrode group (242) are connected in parallel to form a parallel group, which includes four parallel components in sequence: the fifth, the sixth, the seventh, and the eighth. The four electrodes of the valley electrode group (213) and the four switches of the valley electrode group (3) are connected in parallel to form a parallel group, which includes four parallel components in sequence: the fifth, the sixth, the seventh, and the eighth. The first parallel component consists of four parallel components: the ninth, tenth, eleventh, and twelfth. Then, they are connected in series in sequence: the first parallel component of the first parallel group, the fifth parallel component of the second parallel group, and the ninth parallel component of the third parallel group are connected in series in sequence; the second parallel component of the first parallel group, the sixth parallel component of the second parallel group, and the tenth parallel component of the third parallel group are connected in series in sequence; the third parallel component of the first parallel group, the seventh parallel component of the second parallel group, and the eleventh parallel component of the third parallel group are connected in series in sequence; the fourth parallel component of the first parallel group, the eighth parallel component of the second parallel group, and the twelfth parallel component of the third parallel group are connected in series in sequence to form a valley discharge unit. After multiple valley discharge units are connected in parallel, they are connected in series with the valley branch switch (63) and connected to the circuit. Specifically, the free ends of the four parallel components (the first, second, third, and fourth) are connected to one end of the four switches that are connected in parallel to each other in the valley branch switch (63), and the other ends of the four switches are connected to the valley variable resistor (62); the free ends of the four parallel components (the ninth, tenth, eleventh, and twelfth) are grounded. The circuit connection relationship of the spike discharge is described as follows: The positive terminal of the power supply (3) is connected in series with the spike main circuit switch (65), the spike variable resistor (66), the spike branch switch (67), and the spike discharge unit in sequence, and then grounded, and connected to the negative terminal of the power supply (3) grounded; Specifically: For the spike discharge unit, each spike electrode group is first connected in parallel with the corresponding spike electrode group switch, and the four electrodes of the first group of spike electrode groups (221) are connected in parallel with the four switches of the first group of spike electrode groups (681) to form a parallel group respectively. First, parallel group one includes four parallel components: number 1, number 2, number 3, and number 4. The four electrodes of peak electrode group two (222) and the four switches of peak electrode group two (682) are connected in parallel to form parallel group two, which includes four parallel components: number 5, number 6, number 7, and number 8. The four electrodes of peak electrode group three (223) and the four switches of peak electrode group three (683) are connected in parallel to form parallel group three, which includes four parallel components: number 9, number 10, number 11, number 12 ...

11. There are four parallel components in total, numbered 12. Then they are connected in series in sequence: the first parallel component of parallel group 1, the fifth parallel component of parallel group 2, and the ninth parallel component of parallel group 3 are connected in series; the second parallel component of parallel group 1, the sixth parallel component of parallel group 2, and the tenth parallel component of parallel group 3 are connected in series; the third parallel component of parallel group 1, the seventh parallel component of parallel group 2, and the eleventh parallel component of parallel group 3 are connected in series; and the fourth parallel component of parallel group 1 and the eighth parallel component of parallel group 2 are connected in series. The 12th parallel component of the third parallel group is connected in series to form a spike discharge unit; multiple spike discharge units are connected in parallel and connected in series with the spike branch switch (67) in the circuit. Specifically, the free ends of the four parallel components (1, 2, 3, and 4) are respectively connected to one end of the four switches that are connected in parallel to each other in the spike branch switch (67), and the other ends of the four switches are connected to the spike variable resistor (66); the free ends of the four parallel components (9, 10, 11, and 12) are grounded.

8. A method for generating and controlling a drag-reducing virtual surface based on arc discharge, which is based on the arc plasma-enhanced groove turbulent friction drag-reducing device as described in any one of claims 1 to 6, characterized in that, When the arc electrode assembly is not working, the trenches act as a separator for the bottom strip structure of the boundary layer in the flow field, effectively reducing turbulent frictional resistance at the designed Reynolds number. However, when the Reynolds number changes, the drag reduction effect weakens and disappears. Arc plasma discharge can generate Joule heating of the gas. The heated gas is elongated along the flow direction by the incoming flow and creates a blocking effect in the flow field, thus forming a "virtual" flow rib effect. Therefore, by performing arc discharge at different locations in the trench, it is possible to achieve the densification and heightening of the trench, as well as other more flexible functions, by opening and closing the arc at different locations. This allows the trenches to adapt to the spatial scale requirements of the turbulent boundary layer at different velocities. The discharge modes are divided into the following three types: trench valley discharge, trench peak discharge, and intermittent discharge within trench valley and peak groups. Mode 1: Discharge at the bottom of the trench All the trench bottom electrode groups (21) are in the discharge state, generating a virtual arc (4) shape along the flow direction at the bottom of the valley, generating a virtual arc peak at the bottom of the trench, achieving the effect of denser trench spacing, providing denser spanwise disturbance to the flow field, and better adapting to the needs of controlling the boundary layer strip structure at high speed. Mode 2: Trench Spike Discharge All the trench spike electrode groups (22) are in a discharge state, generating an arc (4) virtual surface along the flow direction at the spike, further increasing the height of the trench spike to adapt to more complex flow conditions, generating stronger disturbance to the flow field, stabilizing the strip structure, and reducing frictional resistance; by controlling the magnitude of the discharge current, the intensity of the virtual spike surface can be continuously controlled, thereby adapting to a wider range of flow field conditions; Mode 3: Intermittent discharge at the bottom of trenches and within peak groups The first group of bottom electrodes (211), the third group of bottom electrodes (213), the first group of peak electrodes (221), and the third group of peak electrodes (223) located at the bottom of the trough and the peak discharge, while the second group of bottom electrodes (212) and the second group of peak electrodes (222) are in the closed state, generating a wave-shaped virtual surface along the flow direction. By utilizing the control effect of the wave-shaped surface on the turbulent boundary layer, the drag reduction is further enhanced. When the system operates in the above three discharge modes, the circuit control is as follows: When the discharge is in mode one, the valley bottom main circuit switch (61) and valley bottom branch switch (63) of the trench valley bottom electrode group (21) are in the closed state, the discharge switch (64) of each discharge unit is in the open state, the peak main circuit switch (65) corresponding to the trench peak electrode group (22) is in the open state, and the valley bottom electrode group discharges. In mode two, the peak main circuit switch (65) and peak branch switch (67) of the trench peak electrode group (22) are closed, the discharge switch (68) of each discharge unit is open, the valley main circuit switch (61) corresponding to the trench valley electrode group (21) is open, and the peak electrode group discharges. In mode three, the valley bottom main circuit switch (61), valley bottom branch switch (63), peak main circuit switch (65) and peak branch switch (67) are all in the closed state, and the discharge switch states corresponding to the three sets of discharge units in each branch are open, closed and open, respectively, forming intermittent discharge. That is, the discharge switches corresponding to the valley bottom electrode group 1 (211), valley bottom electrode group 3 (213) and peak electrode group 1 (221) and peak electrode group 3 (223) located at the bottom of the trench and the peak are open, while the discharge switches corresponding to the valley bottom electrode group 2 (212) and peak electrode group 2 (222) are closed, forming intermittent discharge in the valley bottom and peak electrode group. Furthermore, during implementation, by controlling the resistance value of the variable resistor (62), the current and intensity of the arc discharge can be continuously adjusted, thereby continuously adjusting the height of the virtual rib to further adapt to the need for resistance reduction.

9. A method for reducing drag in turbulent friction in trenches using arc plasma enhancement, based on the arc plasma enhancement trench turbulent friction reduction device as described in any one of claims 1 to 6, and based on the method for generating and controlling drag-reducing virtual profiles based on arc discharge as described in claim 8, characterized in that... Step S1: The sensor collects flow field data. The sensor is placed in the flow field to collect temperature, pressure, velocity, and wall shear stress information in the flow field in real time, and inputs the data into the controller. Step S2: The data collected by the sensor is analyzed in the controller. The specific analysis method is described later. Based on this, the appropriate working mode and parameters are selected by the control circuit: Mode 1 S21, Mode 2 S22, Mode 3 S23 or no operation S24. The controller can determine the required discharge strategy according to Equations (1) to (3). If the trench spacing s when not discharging is greater than 15 to 20δ, the controller will determine the appropriate discharge strategy. v , where δ v To test the obtained boundary layer viscous length scale, mode S21 can be used to actively refine the trenches; if the trench height h without discharge is < 8~12δ v In this case, mode 2 S22 can be used to actively raise the trench; at the same time, mode 3 S23 can be used depending on the specific situation to obtain a better drag reduction effect. Step S3: The sensor collects flow field data again to gather flow field information after arc discharge; In step S4, the data collected by the sensors is analyzed again in the controller using software. Surface shear stress sensors such as hot-film sensors are used to measure the surface friction resistance. The change in friction resistance measured before and after the arc discharge is compared. If the friction resistance measured at this time is less than the friction resistance before the arc discharge, the expected drag reduction effect is achieved, and the work ends. Otherwise, a new working mode or a new discharge state is selected again from step S2 based on the flow field information. The discharge intensity of each discharge mode is adjustable and changeable.

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