Multi-target flow control device and method for compressing corner shock wave / boundary layer interference and application

Abstract

The invention relates to the technical field of fluid control of fluid mechanics, in particular to a multi-target flow control device and method for compression corner shock wave / boundary layer interference and application of the multi-target flow control device and method. The control device is arranged in front of the interference of the compression corner. By arranging a passive geometric transition structure, the flow direction of an incoming flow boundary layer can be adjusted, and the reverse pressure gradient caused by flow separation is reduced to suppress flow separation; the unsteady shock wave oscillation effect can be correspondingly improved due to the reduction of the separation area; by adjusting the inclination angle of the corner non-stick shock wave, the action strength of the corner non-stick shock wave and the separation shock wave of the separation area is weakened, the heat flow peak generation mechanism of the corner wall surface is destroyed, and the heat flow peak is reduced. And multi-target flow control of compression corner shock wave / boundary layer interference flow is realized.

Description

Technical Field

[0001] The present invention relates to the field of fluid mechanics and fluid control technology, and in particular to a multi-target flow control device, method and application of compression corner shock wave / boundary layer interference. Background Art

[0002] Compression corners are common local structures in the aerodynamic layout of supersonic / hypersonic aircraft, such as the protrusions of lifting body hypersonic aircraft, inlet corners and other areas. In similar local areas, the boundary layer of the incoming flow forms a local pressure gradient due to the influence of the corner, which can easily lead to flow separation and a decrease in the aerodynamic control rate. The flow separation forms a separation shock wave, which strongly interferes with the inviscid shock wave at the corner slope, forming a local high heat flux area on the wall near the corner, which can reach tens to hundreds of times the heat flux value of the boundary layer in the undisturbed state, posing severe challenges to the thermal protection design of the aircraft.

[0003] Flow separation and local high heat flux peaks at compression corners can easily lead to reduced aerodynamic performance of the aircraft and failure of aerodynamic thermal protection design, which seriously restricts the flight safety of hypersonic aircraft. At the same time, the interference zone and flow separation are in a highly unsteady state. The quasi-periodic saturation and shedding of the separation bubble cause low-frequency oscillation of the separation shock wave, which can lead to unsteady pressure loads on the wall, which can easily damage and affect the structural strength. For example, during the flight test of Columbia, the high heat flux peak and strong shock wave pulsation load caused by shock wave / boundary layer interference led to the disintegration of the thermal protection structure and flight accidents.

[0004] For a long time, people have realized the great harm of shock wave / boundary layer interference at compression corners to aircraft, and developed control devices to suppress flow separation, such as micro-scale vortex generators, passive cavities, etc. However, existing flow control technologies often lead to an increase in the peak heat flux on the slope surface of the compression corner while suppressing flow separation. The lack of flow control technology that can simultaneously suppress flow separation and reduce local heat flux intensity has severely restricted the aerodynamic design and flight safety of hypersonic aircraft, and it is urgent to establish effective multi-objective flow control means. Summary of the invention

[0005] The object of the present invention is to provide a multi-objective flow control device, method and application of compression corner shock wave / boundary layer interference, which can solve the above-mentioned technical problems.

[0006] The present invention provides a multi-objective flow control device for compression corner shock wave / boundary layer interference. The control device is a passive geometric transition structure starting from the front of the compression corner separation zone and ending at the corner wall. The control device is arranged in front of the interference of the compression corner. The control device is suitable for multi-objective flow control of flow separation, local heat flux peak and unsteady shock wave oscillation in typical local compression corner interference zones of various supersonic and hypersonic aircraft.

[0007] The control device can effectively adjust the local flow structure and shock wave / boundary layer interference intensity to achieve the control effect of suppressing flow separation in the interference area, reducing the local heat flux peak and improving the unsteady oscillation of the flow.

[0008] Preferably, the passive geometric transition structure is a geometric transition structure of an arc, a quadratic curve or a quadratic broken line.

[0009] Preferably, the spanwise dimension of the geometric transition structure is consistent with the spanwise dimension of the compression corner. The geometric shape transition of the corner structure from the flat plate before the compression corner to the sloped wall of the compression corner is achieved by introducing the geometric transition structure.

[0010] Preferably, the radius of the arc structure is determined by taking the starting point of the separation zone on the flat plate before the corner as the normal line and the corner wall as the normal line, and the intersection of the two as the center of the circle.

[0011] The starting position of the transition structure is the starting position of the compression corner flow separation, the distance from the starting point of the corner is L, and the ending position is the corner slope wall symmetrical to the corner point.

[0012] Preferably, when the cross-section of the control device is a quadratic fold line, the angle α1 of the first fold angle is smaller than the inclination angle α of the original corner slope.

[0013] Preferably, the end position of the first fold angle is the x-axis coordinate position of the compressed corner, and the second fold angle extends from the end position of the first fold angle toward the corner wall until the corner wall ends.

[0014] When the cross-sectional form of the control device is a quadratic curve or an arc, the curvature is large enough to avoid or minimize the interference intensity between the separation shock wave and the corner slope shock wave.

[0015] When the cross-sectional form of the control device is a quadratic curve or a quadratic broken line, the cross-sectional shape can adjust the interference intensity between the separation shock wave and the corner slope inviscid shock wave, weakening the Mach bar and the interference intensity.

[0016] Preferably, the control effect of the control device for suppressing flow separation is defined in the following manner:

[0017]

[0018] Where ΔL Sep is the change in the length of the separation zone, L Sep,nocontrol is the flow separation length under uncontrolled conditions, L Sep,control is the flow separation length after control. The length of the separation zone L Sep The length definition is that the component Cf of the flow friction resistance coefficient is less than 0.

[0019] L Sep =Cf<0 X,max -Cf<0 X,min

[0020] Among them, Cf<0 X,max is the maximum x-coordinate at which the flow friction component is less than 0, Cf<0 X,min is the minimum x-coordinate where the flow friction resistance component is less than 0, and the distance between them is the length of the separation zone.

[0021] Preferably, the control effect of the control device in reducing the peak value of the heat flux is defined in the following manner:

[0022]

[0023] Where ΔQ max is the change in the local maximum heat flux load peak value, Q max,nocontrol is the local maximum heat flux load peak value under uncontrolled state, Q max,control It is the local maximum heat flux load peak after control. Heat flux peak Q max is the maximum peak value of heat flux load. In numerical calculation, the heat flux load on the wall is obtained by CFD calculation; in the experiment, the heat flux distribution on the surface of the test model is calculated by infrared test data, physical parameters of non-metallic model and one-dimensional heat conduction assumption.

[0024] The control device improves the control effect of the non-steady flow field, and qualitatively determines the control effect by recording the flow field images at different times and comparing the positions of the separation shock waves at different times based on image processing. In addition, the positions of the separation shock waves at different times are recorded at the monitoring point to form a time series, and the spectrum is obtained by Fourier transformation, and the spectrum with and without the control flow field is compared to quantitatively verify the control effect.

[0025] The present invention also provides an optimization design method, which uses the above-mentioned multi-objective flow control device for compression corner shock wave boundary layer interference, and installs the control device in front of the slope wall surface of the compression corner to improve or adjust the local corner shaping.

[0026] The present invention also provides a multi-objective flow control device for the above-mentioned compression corner shock wave boundary layer interference, which is used to adjust the incoming flow direction, reduce the interference intensity between the compression corner inviscid shock wave and the separation shock wave in the flow separation zone, and realize multi-objective flow control in the interference zone.

[0027] Beneficial effects:

[0028] The present invention arranges a geometric transition structure upstream of the compression corner local structure to reduce the adverse pressure gradient and weaken the shock wave interference intensity, thereby achieving effective control of flow separation, heat flux peak and unsteady shock wave oscillation in the interference zone. The present invention arranges a passive geometric transition structure to adjust the flow direction of the incoming boundary layer, reduce the adverse pressure gradient that causes flow separation and inhibit flow separation; the reduction of the separation zone can correspondingly improve the unsteady shock wave oscillation effect; by adjusting the inclination angle of the corner inviscid shock wave, the action intensity of the corner inviscid shock wave and the separation shock wave in the separation zone is weakened, the heat flux peak generation mechanism of the corner wall is destroyed, and the heat flux peak is reduced. Multi-target flow control of compression corner shock wave / boundary layer interference flow is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of the installation position of the flow control device of the present invention;

[0031] Figure 2 Conceptual image of the flow image of the compression corner shock wave / turbulent boundary layer interaction;

[0032] Figure 3 The three views and characteristic parameters of the arc transition structure of the present invention;

[0033] Figure 4 The three views and characteristic parameters of the secondary fold line transition structure of the present invention;

[0034] Figure 5 A schematic diagram of the geometric model used in the numerical simulation and wind tunnel test of the present invention;

[0035] Figure 6 A three-dimensional schematic diagram of the installation of the control device of the present invention on a compression corner;

[0036] Figure 7 A comparison of calculation results of the control device of the present invention for suppressing flow separation and a conceptual diagram of the flow control principle;

[0037] Figure 8 The test images and infrared thermal images of compression corner shock wave / turbulent boundary layer flow are shown;

[0038] Fig. 9 Comparison of heat flow curves with and without control device;

[0039] Fig.10 Comparison of spatial flow field images in the interference area with and without control devices;

[0040] Fig.11 Comparison of the wall pulsating pressure spectra in the interference zone with and without the control device.

[0041] Explanation of reference numerals: 1-control device, 2-compression corner, 3-corner front plate. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] Example 1

[0046] According to the flow characteristics of passive flow control devices in supersonic and hypersonic shock wave / turbulent boundary layer interference, the present invention proposes a passive flow control device with a geometric transition structure to achieve the transition between the flat boundary layer and the flow of the compression corner wall. By adjusting the incoming flow direction, the adverse pressure gradient that causes flow separation is relieved, the flow separation is suppressed, and the unsteady shock wave oscillation caused by flow separation is correspondingly improved; by adjusting the inclination angle of the corner inviscid shock wave, the interference intensity between the corner inviscid shock wave and the separation shock wave caused by flow separation is weakened, and the control goal of reducing the local heat flux peak is achieved. Finally, multi-objective flow control for compression corner shock wave / boundary layer interference flow is achieved.

[0047] like Figure 1 As shown, the control device of the present invention starts at the shock wave / turbulent boundary layer interference separation point, and the device connects the boundary layer before separation with the slope of the compression corner. By setting the control device in the separation zone, the airflow can slowly change the flow direction under the action of the control device, adjust the inclination angle of the corner inviscid shock wave, and weaken the shock wave interference intensity. A multi-objective control effect of suppressing flow separation, adjusting unsteady shock wave oscillation and reducing the local heat flux peak is achieved.

[0048] like Figure 3 and Figure 4As shown, three views of the flow control device are given respectively. The key dimensional parameters of the arc transition flow control device include the starting position and the arc radius; the geometric parameters of the secondary fold line transition include the starting position and the angle of the first corner. The spanwise dimension of the control device is the same width as the corner structure. The geometric form is an arc, a quadratic curve or a secondary fold line. The arc radius takes the starting point of the separation zone on the plate as the normal line and the corner wall as the normal line. The intersection of the two is the center of the circle to determine the arc radius. The secondary fold line ensures that the angle of the first corner is less than the inclination angle α of the original corner. The end point is the x-axis coordinate position of the corner. The second corner extends from the end position of the first corner to the corner wall until it ends at the corner wall. The angle of the second corner is α2.

[0049] For example, the present invention is applied to suppress the compression corner type shock wave / turbulent boundary layer interference zone, and the actual effect of the control device of the present invention is verified through numerical simulation and wind tunnel test. Under the conditions of this example, flow separation and high heat flux intensity areas caused by shock wave / turbulent boundary layer interference appear in the corner interference zone.

[0050] Figure 5 Given is a schematic diagram of the geometric model used in numerical simulation and wind tunnel test.

[0051] The following table shows the wind tunnel test conditions for testing and verifying the control device of the present invention.

[0052] Test status

[0053] Ma Total pressure <![CDATA[T ∞ (K)]]> <![CDATA[Re(m -1 )]]> 6 2MPa 215 <![CDATA[18×10 7 ]]>

[0054] Figure 7 This is a conceptual diagram of the control device of the present invention to suppress flow separation and the control principle. Without the control device, the adverse pressure gradient caused by the corner leads to large-scale flow separation, and the inclination angle of the separation shock wave is large, causing strong shock wave interference on the corner wall, resulting in a high heat flux peak. After the control device is adopted, the incoming flow direction and the inclination angle of the separation shock wave are effectively adjusted, the shock wave interference intensity is significantly reduced, and the heat flux peak is significantly reduced.

[0055] Figure 8This is an experimental image of the compressed corner shock wave / turbulent boundary layer flow, and an infrared display photo. (a) Arc transition. From the temperature image results, it can be seen that the separation zone on the model surface disappears significantly after control, and the area before the corner is a low-temperature area. From the temperature profile, the temperature peak before control is 51.75℃, and the temperature rise is 27.75K; the temperature peak of the model surface after control is 43.09℃, and the temperature rise is 19.09K; the peak temperature rise is reduced by 31.21%. (b) Experimental results of the corner transition device. From the temperature image results, it can be seen that the separation zone on the model surface almost disappears after control, and the area before the corner is a low-temperature area. From the temperature profile, the temperature peak before control is 53.63℃, and the temperature rise is 29.63K; the temperature peak of the model surface after control is 44.48℃, and the temperature rise is 20.48K, and the peak value is reduced by 30.88%.

[0056] Fig. 9 Comparison of heat flow curves with and without control device conditions; the heat flow peak on the control side is significantly reduced, with a reduction of 26.85%-41.07%.

[0057] Fig.10 The figure shows the spatial flow field image comparison of the interference zone with and without the device. It can be seen that after the introduction of the compression corner device, the spatial flow field shows that the flow separation is significantly reduced. The vertical lines given in the figure are the start and end of the separation zone at two different times. It can be seen that after the control, the separation zone is significantly reduced while the position hardly changes, which qualitatively shows that the unsteady oscillation phenomenon of the shock wave is also effectively controlled.

[0058] Fig.11 The comparison of the wall pulsating pressure spectrum of the interference zone with and without the device. It can be clearly seen that there is a low-frequency peak in the interference zone before control, and after control, the low-frequency peak energy is transferred to high frequency.

[0059] The present invention is based on the flow mechanism of compression corner shock wave / turbulent boundary layer interference, the generation mechanism of flow separation, local heat flux peak and flow field unsteadiness, and proposes a multi-objective flow control device for compression corner shock wave / boundary layer interference. The device provides a novel passive control device configuration, and is based on the generation mechanism of flow separation caused by the adverse pressure gradient at the compression corner, peak heat flux caused by shock wave interference, and expansion and contraction of the separation zone. The device uses the control principle of adjusting the direction of the oncoming flow before the corner and reducing the intensity of the shock wave separating the inviscid shock wave and the interference zone, so as to achieve effective suppression of the separation zone and significant reduction of the heat flux peak. The unsteady shock wave oscillation characteristics are adjusted based on the reduction of the separation zone, so as to achieve the multi-objective control effect of suppressing flow separation, reducing the heat flux peak and improving the unsteady shock wave oscillation.

[0060] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-objective flow control device for compression corner shock wave / boundary layer interference, characterized in that: The control device is a passive geometric transition structure starting from the front of the compression corner separation zone and ending at the corner wall. The control device is arranged in front of the interference of the compression corner. The control device is suitable for flow control of supersonic or hypersonic compression corner shock wave / turbulent boundary layer interference.

2. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 1, characterized in that: The passive geometric transition structure is a geometric transition structure of an arc, a quadratic curve or a quadratic polyline.

3. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 2, characterized in that: The spanwise dimension of the geometric transition structure is consistent with the spanwise dimension of the compression corner.

4. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 2, characterized in that: The radius of the arc structure is determined by taking the starting point of the separation zone on the flat plate before the corner as the normal line and the corner wall as the normal line, and the intersection of the two as the center of the circle.

5. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 2, characterized in that: When the cross-section of the control device is a quadratic fold line, the angle α1 of the first fold angle is smaller than the inclination angle α of the original corner slope.

6. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 5, characterized in that: The end position of the first fold angle is the x-axis coordinate position of the compressed corner, and the second fold angle extends from the end position of the first fold angle toward the corner wall until it ends at the corner wall.

7. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 1, characterized in that: The control effect of the control device in suppressing flow separation is defined in the following manner: Where ΔL Sep is the change in the length of the separation zone, L Sep,nocontrol is the flow separation length under uncontrolled conditions, L Sep,control is the flow separation length after control, the length of the separation zone L Sep The length definition is that the component Cf of the flow friction resistance coefficient is less than 0. L Sep =Cf<0 X,max -Cf<0 X,min Among them, Cf<0 X,max is the maximum x-coordinate at which the flow friction component is less than 0, Cf<0 X,min is the minimum x-coordinate where the flow friction resistance component is less than 0, and the distance between them is the length of the separation zone.

8. The multi-objective flow control device of compression corner shock wave / boundary layer interference according to claim 1, characterized in that: The control effect of the control device on reducing the peak value of the heat flux is defined in the following way: Where ΔQ max is the change in the local maximum heat flux load peak value, Q max,nocontrol is the local maximum heat flux load peak value under uncontrolled state, Q max,control is the local maximum heat flux load peak after control, the heat flux peak Q max is the maximum peak value of the heat flux load. In the numerical calculation, the heat flux load on the wall is obtained by CFD calculation. In the experiment, the heat flux distribution on the surface of the test model is calculated by infrared test data, physical parameters of the non-metallic model and one-dimensional heat conduction assumption.

9. An optimization design method, characterized in that: A multi-objective flow control device for compression corner shock wave boundary layer interference as described in any one of claims 1-8 is used, and the control device is installed in front of the slope wall surface of the compression corner to improve or adjust the local corner shaping.

10. The multi-objective flow control device for compression corner shock wave boundary layer interference as described in any one of claims 1-8 is used to adjust the incoming flow direction, reduce the interference intensity between the compression corner inviscid shock wave and the separation shock wave in the flow separation zone, and realize multi-objective flow control in the interference zone.

Images