Method and device for predicting leading edge position of shock wave string of air inlet with quasi-circular section

Abstract

The invention discloses a quasi-circular section air inlet shock train leading edge position prediction method and device. The method comprises the steps that flow field information of a quasi-circular section air inlet in a current through-flow state is acquired; determining the circumferential distribution of the flow direction shear stress of the wall surface of the outlet section of the isolation section from the flow field information, and taking the azimuth angle corresponding to the minimum value of the flow direction shear stress as the current forward extension azimuth angle; from the outlet position of the isolation section, the outlet back pressure is continuously increased along with the time change, a parameter value corresponding to the current time step determined based on the forward extension azimuth angle and the flow field information is substituted into a target shock wave string length empirical function, and the shock wave string leading edge position of the next time step is calculated until the outlet back pressure is increased to the set real back pressure; obtaining a final shock wave string leading edge position; wherein the target shock wave string length empirical function is obtained by correcting the shock wave string length empirical function of the uniform incoming flow round pipe through the local flow parameter at the forward extension azimuth angle and converting the corrected shock wave string length empirical function into time step correlation.

Description

Technical Field

[0001] This application relates to the field of hypersonic vehicle propulsion system technology, and in particular to a method and device for predicting the position of the leading edge of a shock wave train in a near-circular cross-section air inlet. Background Technology

[0002] The scramjet engine is the core power unit of air-breathing hypersonic vehicles, and the flow within the upstream inlet / isolation section of its combustion chamber is crucial to the engine's operational stability. During engine operation, the high back pressure generated in the combustion chamber propagates upstream, forming a complex flow structure—the shock train—within the isolation section, composed of a series of shock waves and boundary layer interactions. The position of the shock train within the isolation section directly determines the inlet's resistance to back pressure. If the shock train is pushed into the inlet upstream of the isolation section, it will cause the inlet to fail to start, resulting in a sharp drop in engine thrust. Therefore, accurately predicting the shock train position is a key technology for achieving stable engine operation.

[0003] Currently, the Billig formula, derived from experiments with uniform-flow circular tubes, is widely used to predict shock train length. However, hypersonic inlets with near-circular cross-sections exhibit strong three-dimensional flow characteristics. In particular, multiple pairs of streamer vortices of varying intensities and sizes are generated within the inlet. The interaction between these streamer vortices and the shock wave within the inlet results in a highly non-uniform distribution of flow field parameters circumferentially at the inlet of the isolation section. In this type of three-dimensional flow field, the shock train leading edge is no longer the axisymmetric shape assumed by uniform flow, but rather exhibits a locally protruding non-axisymmetric structure. Therefore, the Billig formula derived from experiments with uniform-flow circular tubes cannot characterize this three-dimensional effect dominated by streamer vortices, leading to significant deviations between its predictions and actual conditions. Summary of the Invention

[0004] In view of the shortcomings of the prior art, this application provides a method and apparatus for predicting the position of the shock wave front of a near-circular cross-section inlet, so as to solve the problem that the prior art cannot accurately predict the position of the shock wave front of a near-circular cross-section inlet.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] The first aspect of this application provides a method for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, including:

[0007] Obtain flow field information of a near-circular cross-section air inlet under the current flow conditions;

[0008] The circumferential distribution of the wall flow-direction shear stress of the outlet section of the isolation section of the near-circular cross-section inlet is determined from the current flow field information, and the azimuth angle corresponding to the minimum value of the flow-direction shear stress is taken as the current forward azimuth angle.

[0009] Starting from the outlet position of the isolation section of the near-circular cross-section inlet, the outlet back pressure is continuously increased over time. The parameter values ​​corresponding to the current time step, determined based on the current forward azimuth angle and the flow field information, are substituted into the target shock train length empirical function to calculate the shock train leading edge position for the next time step. This process continues until the outlet back pressure increases to the set true back pressure, yielding the final predicted shock train leading edge position. The target shock train length empirical function is obtained by converting the modified shock train length empirical function into a time-step-related function. The modified shock train length empirical function is obtained by correcting the shock train length empirical function of the uniformly flowing circular pipe using local flow parameters at the forward azimuth angle.

[0010] Optionally, in the above-described method for predicting the position of the shock front of a near-circular cross-section inlet, obtaining the flow field information of the near-circular cross-section inlet under the current flow conditions includes:

[0011] By performing numerical simulation on the near-circular cross-section inlet under the current flow conditions, the flow field information under the current flow conditions is obtained; wherein, the flow field information includes the wall shear stress distribution of the near-circular cross-section inlet and the three-dimensional flow parameters of the entire flow field.

[0012] Optionally, in the above-described method for predicting the position of the shock front of a near-circular cross-section inlet, determining the circumferential distribution of the wall flow-direction shear stress at the outlet section of the isolation section of the near-circular cross-section inlet from the current flow field information includes:

[0013] Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

[0014] Optionally, the above-described method for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet also includes:

[0015] An empirical function for obtaining the shock train length of a uniformly flowing circular pipe;

[0016] The empirical function for the shock train length of the uniformly flowing circular pipe is corrected by using the average Mach number at the shock train leading edge to correct the incoming Mach number, the average static pressure at the local flow rate to correct the incoming static pressure, the distance between the shock train leading edge and the outlet of the isolation section to correct the shock train length, the local boundary layer momentum thickness at the leading edge azimuth angle to correct the incoming flow velocity thickness, and the local momentum thickness Reynolds number to correct the flow velocity thickness Reynolds number. The corrected empirical function for the shock train length is then obtained as follows:

[0017] ;

[0018] in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

[0019] Optionally, the above-described method for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet also includes:

[0020] The modified empirical function for shock train length is converted into an expression for the shock train leading edge position, and time steps are added to the shock train leading edge position and the outlet back pressure of the isolation section to obtain the empirical function for the target shock train length:

[0021] .

[0022] A second aspect of this application provides a device for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, comprising:

[0023] The data acquisition unit is used to acquire the flow field information of the near-circular cross-section air inlet under the current flow conditions;

[0024] The azimuth angle determination unit is used to determine the circumferential distribution of the wall flow-direction shear stress of the outlet section of the isolation section of the near-circular cross-section air inlet from the current flow field information, and take the azimuth angle corresponding to the minimum value of the flow-direction shear stress as the current forward azimuth angle.

[0025] The position prediction unit is used to continuously increase the outlet back pressure over time, starting from the outlet position of the isolation section of the near-circular cross-section inlet, and substitute the parameter values ​​corresponding to the current time step determined based on the current forward azimuth angle and the flow field information into the target shock train length empirical function to calculate the shock train leading edge position for the next time step, until the outlet back pressure increases to the set true back pressure, thus obtaining the final predicted shock train leading edge position; wherein, the target shock train length empirical function is obtained by converting the modified shock train length empirical function into a function related to the time step; the modified shock train length empirical function is obtained by modifying the shock train length empirical function of the uniformly flowing circular pipe using the local flow parameters at the forward azimuth angle.

[0026] Optionally, in the above-mentioned near-circular cross-section inlet shock wave front position prediction device, the data acquisition unit includes:

[0027] The numerical simulation unit is used to obtain the flow field information under the current flow state by performing numerical simulation on the near-circular cross-section air inlet; wherein, the flow field information includes the wall shear stress distribution of the near-circular cross-section air inlet and the three-dimensional flow parameters of the entire flow field.

[0028] Optionally, in the above-described device for predicting the position of the shock front edge of a near-circular cross-section inlet, when the azimuth angle determination unit performs the step of determining the circumferential distribution of the wall flow-direction shear stress at the outlet section of the near-circular cross-section inlet from the current flow field information, it is used to:

[0029] Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

[0030] Optionally, the above-mentioned near-circular cross-section inlet shock wave front position prediction device further includes:

[0031] The function acquisition unit is used to obtain the empirical function for the shock train length of a uniformly flowing circular pipe;

[0032] The correction unit is used to correct the empirical function of the shock train length of the uniformly flowing circular pipe by using the average Mach number of the flow rate at the shock train leading edge position to correct the incoming Mach number, using the average static pressure of the local flow rate to correct the incoming static pressure, using the distance between the shock train leading edge position and the outlet of the isolation section to correct the shock train length, using the local boundary layer momentum thickness at the leading azimuth angle to correct the incoming flow velocity thickness, and using the local momentum thickness Reynolds number to correct the incoming flow velocity thickness Reynolds number, thereby obtaining the corrected empirical function of the shock train length:

[0033] ;

[0034] in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

[0035] Optionally, the above-mentioned near-circular cross-section inlet shock wave front position prediction device further includes:

[0036] The conversion unit is used to convert the modified empirical function of shock train length into an expression for the shock train leading edge position, and to add time steps to the shock train leading edge position and the outlet back pressure of the isolation section to obtain the target empirical function of shock train length:

[0037] .

[0038] This application provides a method for predicting the shock wave front position of a near-circular cross-section inlet. The method acquires the flow field information of the near-circular cross-section inlet under the current flow conditions. Then, based on the current flow field information, it determines the circumferential distribution of the flow-direction shear stress on the wall surface of the isolator section outlet cross-section of the near-circular cross-section inlet. The azimuth angle corresponding to the minimum flow-direction shear stress is taken as the current forward azimuth angle. Finally, starting from the outlet position of the isolator section of the near-circular cross-section inlet, the outlet back pressure is continuously increased over time. The parameter values ​​corresponding to the current time step, determined based on the current forward azimuth angle and flow field information, are substituted into the empirical function of the target shock wave length to calculate the shock wave front position for the next time step. This process continues until the outlet back pressure increases to the set true back pressure, yielding the final predicted shock wave front position. The empirical function of the shock wave length for a uniformly flowing circular pipe is corrected using local flow parameters at the forward azimuth angle to obtain a corrected empirical function of the shock wave length, which is then modified to reflect the flow field of the near-circular cross-section inlet. Furthermore, the modified empirical function of shock train length is transformed into a time-step-related function to obtain the empirical function of target shock train length. By assuming that the outlet back pressure changes with time, the position of the shock train leading edge corresponding to the set outlet back pressure can be obtained through continuous iterative calculation. This directly correlates the three-dimensional forward structure of the shock train in the near-circular cross-section inlet with its inducing factor, namely the reduction of wall shear stress caused by the upstream flow vortex. Based on the local flow parameters, the Billig formula is modified to achieve accurate prediction of the position of the three-dimensional shock train in the near-circular cross-section inlet. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0040] Figure 1 A flowchart illustrating a method for predicting the position of the leading edge of a near-circular cross-section inlet shock train, provided in an embodiment of this application;

[0041] Figure 2 A schematic diagram illustrating an example of a circular cross-section isolation segment provided in an embodiment of this application;

[0042] Figure 3 A schematic diagram illustrating an example of the wall flow-direction shear stress distribution at the outlet of an isolation section under flow field conditions with multiple angles of attack, provided for an embodiment of this application;

[0043] Figure 4 A schematic diagram illustrating an example of the velocity divergence isosurface of the flow field in the isolation section under different angles of attack and back pressure states, provided for an embodiment of this application.

[0044] Figure 5 A schematic diagram illustrating an example of the curve showing the change in the flow direction position of the shock wave front at different angles of attack with back pressure, provided for an embodiment of this application;

[0045] Figure 6 This is a schematic diagram of the architecture of a near-circular cross-section inlet shock wave front position prediction device provided in an embodiment of this application. Detailed Implementation

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0048] This application provides a method for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, such as... Figure 1 As shown, it includes:

[0049] S101. Obtain the flow field information of the near-circular cross-section air inlet under the current flow conditions.

[0050] It should be noted that, as Figure 2 As shown, the rectangular-to-circular inlet has a roughly circular cross-section isolation section. Therefore, a cylindrical coordinate system can be established with the centerline of the isolation section as the axis, allowing any point on the wall to be described by its flow direction position x and circumferential azimuth angle φ. Specifically, x is 0 at the inlet lip, the lateral azimuth angle φ = 180° at the lip, and the lateral azimuth angle φ = 0° at the forebody. For subsequent calculations, information on the entire flow field of the roughly circular cross-section inlet under the current flow conditions is obtained to provide the necessary numerical values ​​for the calculations.

[0051] Optionally, in another embodiment of this application, one specific implementation of step S101 includes:

[0052] By performing numerical simulation on a near-circular cross-section air inlet under the current flow conditions, the flow field information under the current flow conditions is obtained.

[0053] The flow field information includes the distribution of shear stress along the wall of the near-circular cross-section inlet, as well as the three-dimensional flow parameters of the entire flow field, such as the average static pressure and the distribution of Mach number along the flow direction.

[0054] Specifically, in this embodiment, the Reynolds-averaged Navier-Stokes equation numerical simulation method is used to calculate the flow field data of the near-circular cross-section inlet under a specified current flow state. For example, the flow field of the inlet is calculated under the following conditions: incoming Mach number 8, static temperature 62K, static pressure 318Pa, and specified angles of attack (e.g., 0°, 4°, and 8°). This allows for the acquisition of complete flow field data, particularly the distribution of the shear stress τ along the wall flow direction on the entire circumference of the outlet section of the isolation section. x (φ).

[0055] S102. Determine the circumferential distribution of the flow-direction shear stress on the wall of the outlet section of the isolation section of the near-circular cross-section inlet from the current flow field information, and take the azimuth angle corresponding to the minimum value of the flow-direction shear stress as the current forward azimuth angle.

[0056] It should be noted that, as Figure 3 The diagram shows the distribution of flow-directed shear stress on the outlet wall of the isolation section under flow fields with angles of attack of 0°, 4°, and 8°. The flow-directed shear stress is used to make the flow pressure dimensionless. It can be seen that at an angle of attack of 0°, the minimum shear stress occurs at φ=10° (near the inlet forebody side); at an angle of attack of 4°, the minimum shear stress occurs at φ=7° (near the inlet forebody side); and at an angle of attack of 8°, the minimum shear stress occurs at φ=180° (near the inlet lip side). Based on this, it is predicted that at angles of attack of 0° and 4°, when back pressure is applied, the shock wave front will be located at the inlet forebody side (φ...). sAt angles of attack of 10° and 7°, local forward extension occurs; at an angle of attack of 8°, when back pressure is applied, the leading edge of the shock wave will be on the inlet lip side (φ). s =180°) Local forward extension occurs. Therefore, it is necessary to analyze the circumferential distribution of the flow-direction shear stress on the wall of the isolation section outlet section, and take the azimuth angle corresponding to the minimum flow-direction shear stress as the current forward extension azimuth angle, so as to perform analysis and calculation for this azimuth.

[0057] Optionally, in another embodiment of this application, a specific implementation for determining the circumferential distribution of the wall flow shear stress at the outlet section of the isolation section of a near-circular cross-section inlet includes:

[0058] Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

[0059] S103. Starting from the outlet position of the isolation section of the near-circular cross-section inlet, the outlet back pressure is continuously increased over time. The parameter values ​​corresponding to the current time step, determined based on the current forward azimuth and flow field information, are substituted into the empirical function of the target shock train length to calculate the position of the shock train leading edge in the next time step. This process continues until the outlet back pressure increases to the set true back pressure, thus obtaining the final predicted position of the shock train leading edge.

[0060] The target shock train length empirical function is obtained by converting the modified shock train length empirical function into a time-step-dependent function. The modified shock train length empirical function is obtained by modifying the shock train length empirical function of a uniformly flowing circular pipe using local flow parameters at the forward azimuth angle.

[0061] It should be noted that since the shock wave front of the near-circular cross-section inlet is no longer axisymmetric as assumed by uniform inflow, the inflow at different azimuths and the conditions at different locations are also different. Therefore, in order to analyze the flow field at the forward azimuth angle, the empirical function of the shock wave length of the original uniform inflow circular pipe is modified by the local flow parameters at the forward azimuth angle, so that it can reflect the flow field at any forward azimuth angle. Furthermore, since the flow field conditions at different locations are also different, in this embodiment, a time step is introduced into the modified empirical function of shock wave length. It is assumed that the outlet back pressure increases slowly with the time step, and different outlet back pressures correspond to different locations, so the location also changes accordingly. Thus, through continuous iterative calculation, the position of the shock wave front corresponding to the set true back pressure can be calculated, and the final prediction result can be obtained.

[0062] Therefore, it is necessary to pre-analyze the empirical function for the target shock wave train length in order to calculate the position of the shock wave train leading edge for the current near-circular cross-section inlet. Optionally, in the embodiments of this application, the specific method for determining the empirical function for the target shock wave train length includes:

[0063] First, obtain an empirical function for the shock train length of a uniformly flowing circular pipe.

[0064] Among them, the empirical function for shock train length (Billig formula) summarized from the uniform inflow circular pipe experiment is:

[0065]

[0066] in, For shock train length, For the incoming Mach number, For the outlet back pressure of the isolation section, For incoming static pressure, For the outlet diameter of the isolation section, For the thickness of the flow, The thickness of the flow is the Reynolds number.

[0067] Then, the empirical function of the shock train length for a uniformly flowing circular pipe is corrected by using the average Mach number of the flow rate at the shock train leading edge position to correct the incoming Mach number, using the average static pressure of the local flow rate to correct the incoming static pressure, using the distance between the shock train leading edge position and the outlet of the isolation section to correct the shock train length, using the local boundary layer momentum thickness at the leading edge azimuth angle to correct the incoming flow velocity thickness, and using the local momentum thickness Reynolds number to correct the incoming flow velocity thickness Reynolds number.

[0068] Therefore, the corrected empirical function for shock train length is:

[0069]

[0070] in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

[0071] Finally, the modified empirical function for shock train length is converted into an expression for the position of the shock train leading edge, and time steps are added to the position of the shock train leading edge and the outlet back pressure of the isolation section to obtain the empirical function for the target shock train length.

[0072] In other words, assuming the outlet back pressure of the isolation section increases slowly with time, the modified Billig formula is rewritten as a time-step-dependent modified Billig formula, i.e., an empirical function of the target shock train length:

[0073]

[0074] It should be noted that by adding a time step, the outlet back pressure in the modified Billig formula changes with time, and the position of the shock wave front will also shift accordingly. However, other parameters related to the position of the shock wave front (such as...) The parameters also change with the time step. When the change is small, these parameters can be considered to remain unchanged. Therefore, as shown by the empirical function of the target shock train length, the position of the shock train leading edge in the next time step can be calculated by continuously and slowly increasing the time and the outlet back pressure, thereby using the parameters of the previous time step. This process continues until the set true back pressure is reached, at which point the position of the shock train leading edge corresponding to the true back pressure can be obtained.

[0075] Therefore, specifically from time t=0, the initial position x of the shock wave front... s (0)=x e Export pressure Initially, the outlet back pressure is increased by Δt for every increase of time t. Then, the local flow state parameters of the shock front at the current time step are obtained. Specifically, based on the current x... s Based on (t) and the flow field information obtained above, the local flow parameters at this location in the forward azimuth angle are obtained by interpolation, such as the flow-average Mach number Ma. a (x s ), average static pressure p a (x s ), boundary layer momentum thickness θ(x) s ,φ s ) and momentum thickness Reynolds number Re θ (x s ,φ s Then, the obtained parameter values ​​are substituted into the time-step-related modified Billig formula (an empirical function for the target shock train length) to calculate the position of the shock train leading edge at the next time step. By continuously iterating the calculations as described above, the calculation can be stopped when the assumed outlet back pressure increases to the set actual outlet back pressure. The final position of the shock wave front is then the predicted position of the shock wave front flow direction.

[0076] For example, such as Figure 4 The velocity divergence isosurfaces of the flow field in the isolation section under different angles of attack and back pressure states represent the three-dimensional shock train structure. It can be seen that when the angle of attack is 0° and 4°, the shock train leading edge is located near the inlet forebody side; when the angle of attack is 8°, the shock train leading edge is located near the inlet lip side. Therefore, this verifies that the method provided in the embodiments of this application correctly predicts the leading azimuth angle of the shock train. Further, when the angle of attack is 0°, the ratio of back pressure to incoming static pressure is set to 175, 200, 225, and 250, respectively. When the angle of attack is 4°, the back pressure ratios are set to 250, 300, and 420, respectively. When the angle of attack is 8°, the back pressure ratios are set to 300, 375, 400, 430, 440, and 460, respectively. At this time, as... Figure 5 As shown, it presents the variation of the flow direction position of the shock front at different angles of attack with back pressure. A comparison of the predicted results with the numerical simulation results shows that the predicted results agree well with the numerical simulation results, and the maximum prediction deviation of the shock front flow direction position is only 14% of the length of the isolation section.

[0077] This application provides a method for predicting the shock wave front position of a near-circular cross-section inlet. The method acquires the flow field information of the near-circular cross-section inlet under the current flow conditions. Then, it determines the circumferential distribution of the flow-direction shear stress on the wall surface of the isolator section outlet cross-section of the near-circular cross-section inlet from the current flow field information, and uses the azimuth angle corresponding to the minimum flow-direction shear stress as the current forward azimuth angle. Finally, starting from the outlet position of the isolator section of the near-circular cross-section inlet, the outlet back pressure is continuously increased over time. The parameter values ​​corresponding to the current time step, determined based on the current forward azimuth angle and flow field information, are substituted into the empirical function of the target shock wave length to calculate the shock wave front position for the next time step. This process continues until the outlet back pressure increases to the set true back pressure, yielding the final predicted shock wave front position. The empirical function of the shock wave length for a uniformly flowing circular pipe is corrected using local flow parameters at the forward azimuth angle to obtain a corrected empirical function of the shock wave length, which is then modified to reflect the flow field of the near-circular cross-section inlet. Furthermore, the modified empirical function of shock train length is transformed into a time-step-related function to obtain the empirical function of target shock train length. By assuming that the outlet back pressure changes with time, the position of the shock train leading edge corresponding to the set outlet back pressure can be obtained through continuous iterative calculation. This directly correlates the three-dimensional forward structure of the shock train in the near-circular cross-section inlet with its inducing factor, namely the reduction of wall shear stress caused by the upstream flow vortex. Based on the local flow parameters, the Billig formula is modified to achieve accurate prediction of the position of the three-dimensional shock train in the near-circular cross-section inlet.

[0078] Another embodiment of this application provides a device for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, such as... Figure 6 As shown, it includes:

[0079] The data acquisition unit 601 is used to acquire the flow field information of the near-circular cross-section air intake under the current flow conditions.

[0080] The azimuth angle determination unit 602 is used to determine the circumferential distribution of the wall flow-direction shear stress of the outlet section of the isolation section of the near-circular cross-section inlet from the current flow field information, and take the azimuth angle corresponding to the minimum value of the flow-direction shear stress as the current forward azimuth angle.

[0081] The position prediction unit 603 is used to continuously increase the outlet back pressure over time, starting from the outlet position of the isolator section of the near-circular cross-section inlet. It substitutes the parameter values ​​corresponding to the current time step, determined based on the current forward azimuth angle and flow field information, into the target shock train length empirical function to calculate the shock train leading edge position for the next time step. This process continues until the outlet back pressure increases to the set true back pressure, yielding the final predicted shock train leading edge position. The target shock train length empirical function is obtained by converting a modified shock train length empirical function into a time-step-dependent function. The modified shock train length empirical function is obtained by correcting the shock train length empirical function of a uniformly flowing circular pipe using local flow parameters at the forward azimuth angle.

[0082] Optionally, in another embodiment of the inlet shock wave front position prediction device provided in this application, the data acquisition unit includes:

[0083] The numerical simulation unit is used to obtain the flow field information under the current flow conditions by numerically simulating the inlet with a near-circular cross-section. This flow field information includes the distribution of shear stress along the wall of the near-circular cross-section inlet and the three-dimensional flow parameters of the entire flow field.

[0084] Optionally, in the near-circular cross-section inlet shock wave front position prediction device provided in another embodiment of this application, when the azimuth angle determination unit performs the task of determining the circumferential distribution of the wall flow-direction shear stress at the outlet section of the near-circular cross-section inlet from the current flow field information, it is used for:

[0085] Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

[0086] Optionally, in another embodiment of this application, the shock wave front position prediction device for a near-circular cross-section inlet provides a further component:

[0087] The function acquisition unit is used to obtain the empirical function for the shock train length of a uniformly flowing circular pipe.

[0088] The correction unit is used to correct the empirical function of the shock train length for a uniformly flowing circular pipe by using the average Mach number of the flow rate at the shock train leading edge position to correct the incoming Mach number, using the average static pressure of the local flow rate to correct the incoming static pressure, using the distance between the shock train leading edge position and the outlet of the isolation section to correct the shock train length, using the local boundary layer momentum thickness at the leading edge azimuth angle to correct the incoming flow velocity thickness, and using the local momentum thickness Reynolds number to correct the incoming flow velocity thickness Reynolds number. The corrected empirical function of the shock train length is then obtained.

[0089] .

[0090] in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

[0091] Optionally, in another embodiment of this application, the shock wave front position prediction device for a near-circular cross-section inlet provides a further component:

[0092] The conversion unit is used to convert the modified empirical function of shock train length into an expression for the shock train leading edge position, and to add time steps for the shock train leading edge position and the outlet back pressure of the isolation section to obtain the target empirical function of shock train length:

[0093] .

[0094] It should be noted that the specific working process of each unit provided in the above embodiments of this application can be referred to the implementation process of the corresponding steps in the above method embodiments, and will not be repeated here.

[0095] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, characterized in that, include: Obtain flow field information of a near-circular cross-section air inlet under the current flow conditions; The circumferential distribution of the wall flow-direction shear stress of the outlet section of the isolation section of the near-circular cross-section inlet is determined from the current flow field information, and the azimuth angle corresponding to the minimum value of the flow-direction shear stress is taken as the current forward azimuth angle. Starting from the outlet position of the isolation section of the near-circular cross-section inlet, the outlet back pressure is continuously increased over time. The parameter values ​​corresponding to the current time step, determined based on the current forward azimuth angle and the flow field information, are substituted into the target shock train length empirical function to calculate the shock train leading edge position for the next time step. This process continues until the outlet back pressure increases to the set true back pressure, yielding the final predicted shock train leading edge position. The target shock train length empirical function is obtained by converting the modified shock train length empirical function into a time-step-related function. The modified shock train length empirical function is obtained by correcting the shock train length empirical function of the uniformly flowing circular pipe using local flow parameters at the forward azimuth angle.

2. The method according to claim 1, characterized in that, The acquisition of flow field information of the near-circular cross-section air inlet under the current flow conditions includes: By performing numerical simulation on the near-circular cross-section inlet under the current flow conditions, the flow field information under the current flow conditions is obtained; wherein, the flow field information includes the wall shear stress distribution of the near-circular cross-section inlet and the three-dimensional flow parameters of the entire flow field.

3. The method according to claim 2, characterized in that, Determining the circumferential distribution of the wall flow-direction shear stress at the outlet section of the isolation section of the near-circular cross-section inlet from the current flow field information includes: Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

4. The method according to claim 1, characterized in that, Also includes: An empirical function for obtaining the shock train length of a uniformly flowing circular pipe; The empirical function for the shock train length of the uniformly flowing circular pipe is corrected by using the average Mach number at the shock train leading edge to correct the incoming Mach number, the average static pressure at the local flow rate to correct the incoming static pressure, the distance between the shock train leading edge and the outlet of the isolation section to correct the shock train length, the local boundary layer momentum thickness at the leading edge azimuth angle to correct the incoming flow velocity thickness, and the local momentum thickness Reynolds number to correct the flow velocity thickness Reynolds number. The corrected empirical function for the shock train length is then obtained as follows: ； in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

5. The method according to claim 4, characterized in that, Also includes: The modified empirical function for shock train length is converted into an expression for the shock train leading edge position, and time steps are added to the shock train leading edge position and the outlet back pressure of the isolation section to obtain the empirical function for the target shock train length: 。 6. A device for predicting the position of the leading edge of a shock wave train in a near-circular cross-section inlet, characterized in that, include: The data acquisition unit is used to acquire the flow field information of the near-circular cross-section air inlet under the current flow conditions; The azimuth angle determination unit is used to determine the circumferential distribution of the wall flow-direction shear stress of the outlet section of the isolation section of the near-circular cross-section air inlet from the current flow field information, and take the azimuth angle corresponding to the minimum value of the flow-direction shear stress as the current forward azimuth angle. The position prediction unit is used to continuously increase the outlet back pressure over time, starting from the outlet position of the isolation section of the near-circular cross-section inlet, and substitute the parameter values ​​corresponding to the current time step determined based on the current forward azimuth angle and the flow field information into the target shock train length empirical function to calculate the shock train leading edge position for the next time step, until the outlet back pressure increases to the set true back pressure, thus obtaining the final predicted shock train leading edge position; wherein, the target shock train length empirical function is obtained by converting the modified shock train length empirical function into a function related to the time step; the modified shock train length empirical function is obtained by modifying the shock train length empirical function of the uniformly flowing circular pipe using the local flow parameters at the forward azimuth angle.

7. The apparatus according to claim 6, characterized in that, The data acquisition unit includes: The numerical simulation unit is used to obtain the flow field information under the current flow state by performing numerical simulation on the near-circular cross-section air inlet; wherein, the flow field information includes the wall shear stress distribution of the near-circular cross-section air inlet and the three-dimensional flow parameters of the entire flow field.

8. The apparatus according to claim 7, characterized in that, When the azimuth angle determination unit performs the task of determining the circumferential distribution of the wall flow-direction shear stress at the outlet section of the isolation section of the near-circular cross-section inlet from the current flow field information, it is used for: Based on the wall shear stress distribution in the flow field information, the wall shear stress at the outlet position of the isolation section is extracted to obtain the circumferential distribution of the wall shear stress at the outlet section of the isolation section of the near-circular cross-section inlet.

9. The apparatus according to claim 6, characterized in that, Also includes: The function acquisition unit is used to obtain the empirical function for the shock train length of a uniformly flowing circular pipe; The correction unit is used to correct the empirical function of the shock train length of the uniformly flowing circular pipe by using the average Mach number of the flow rate at the shock train leading edge position to correct the incoming Mach number, using the average static pressure of the local flow rate to correct the incoming static pressure, using the distance between the shock train leading edge position and the outlet of the isolation section to correct the shock train length, using the local boundary layer momentum thickness at the leading azimuth angle to correct the incoming flow velocity thickness, and using the local momentum thickness Reynolds number to correct the incoming flow velocity thickness Reynolds number, thereby obtaining the corrected empirical function of the shock train length: ； in, For the leading edge position of the shock wave, For the exit location of the isolation section, The average Mach number of the flow rate at the leading edge of the shock train, For the outlet back pressure of the isolation section, For local flow average static pressure, For the outlet diameter of the isolation section, Forward azimuth, For the local boundary layer momentum thickness at the forward azimuth angle, The local momentum thickness Reynolds number.

10. The apparatus according to claim 9, characterized in that, Also includes: The conversion unit is used to convert the modified empirical function of shock train length into an expression for the shock train leading edge position, and to add time steps to the shock train leading edge position and the outlet back pressure of the isolation section to obtain the target empirical function of shock train length: 。

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