A fast equivalent flow field calculation method for a submerged inlet fused with inlet grid

Abstract

The present invention proposes a method for calculating the fast equivalent flow field of a buried inlet duct with an integrated inlet grid. First, the flow field information of the buried inlet duct with and without a grid is calculated under a certain working condition; a characteristic section is established near the bottom of the grid in the buried inlet duct, and the flow field information of the buried inlet duct with and without a grid is interpolated to the characteristic section to obtain the total pressure distribution of the characteristic section with and without a grid, and then the total pressure loss distribution of the characteristic section caused by the grid is obtained; the total pressure loss distribution of the characteristic section and the geometric characteristics of the grid are combined, and the momentum source term is used to realize the calculation of the equivalent flow field under the set working condition. The present invention avoids the difficulty of direct CFD numerical simulation of the complex geometric configuration of the grid during the calculation process, and greatly reduces the calculation complexity and cost.

Description

Technical Field

[0001] The present invention relates to the field of fluid mechanics calculation technology, and in particular to a method for calculating the fast equivalent flow field of a buried air inlet fused with an inlet grid. Background Art

[0002] At present, there are two main methods for obtaining inlet aerodynamic performance data: wind tunnel test and CFD numerical simulation method. In general, when obtaining inlet aerodynamic characteristics data of coupled internal and external flows, wind tunnel test has high authenticity, but the cost is too high, and the data acquisition efficiency is low, making it difficult to carry out on a large scale. With the development of computational fluid dynamics and computer science, computational fluid dynamics (CFD) simulation has made great progress in both computational accuracy and efficiency. With the advantages of low cost, strong flexibility, high repeatability and high computational accuracy, it has become an indispensable tool in the design process of modern aircraft. However, CFD numerical simulation method also shows certain limitations when targeting complex geometric models. The first is that it is difficult to divide high-quality computational grids. In CFD simulation, grid division is the process of discretizing continuous physical space into a series of units, which are used for numerical solution. High-quality grids can speed up the computational convergence speed and improve the computational stability, because it is necessary to ensure that the quality of the grid (such as aspect ratio, twist, etc.) meets the requirements. Complex geometric models have a large number of sharp boundaries and narrow spaces, which bring huge challenges to grid division. The second is the surge in the number of grids. The number of grids has many effects on CFD numerical calculations, which are directly related to the demand for computing resources and computing efficiency. Complex geometric models often have very small features. In order to capture the impact of these features on the flow field, the grid size must also be reduced to the corresponding order of magnitude, which will greatly increase the number of grids. In view of the limitations of CFD numerical simulation methods when facing complex geometries, researchers have proposed a series of simplified models for different application scenarios. The most representative of these is the propeller equivalent disk model. The basic idea of ​​the propeller equivalent disk model is to simplify the complex flow characteristics of the propeller into the effect of a disc without thickness. The airflow parameters before and after the disc are the same as those before and after the propeller. The aerodynamic characteristics of the real propeller are simulated by setting the corresponding parameters. This method avoids the difficulty of directly simulating the complex geometry and flow characteristics of the propeller during the calculation process, and reduces the calculation complexity and cost.

[0003] As the "breathing duct" of the air-breathing propulsion system, the air inlet is responsible for capturing, compressing, and rectifying the airflow. Its design features and operating characteristics have a significant impact on the engine's operating efficiency and the envelope of the aircraft. Advanced air inlets often need to pay attention to factors such as electromagnetic shielding, structural weight, and external resistance while continuously tapping the aerodynamic potential. Therefore, the inlet grid is combined with the embedded inlet to obtain an embedded inlet called a fused inlet grid.

[0004] The aerodynamic performance of the inlet is closely related to the changes in its design parameters and flight conditions. When designing a buried inlet with a fused inlet grid, in order to make its air intake performance meet the entire flight envelope, it is necessary to obtain the aerodynamic performance under different design parameters and different flight conditions. For the buried inlet with a fused inlet grid, the characteristic size of the grid hole is quite different from the characteristic size of the aircraft inlet (the characteristic size of the grid aperture is often in the order of millimeters, about one-fifth of the wavelength of the electromagnetic wave, while the characteristic size of the aircraft inlet is in the order of meters), and because the grid has a small diversion angle, there are a large number of sharp boundaries and narrow spaces in the grid geometry model. Therefore, if the grid is not divided properly, it is easy to cause local grid distortion, which seriously affects the calculation accuracy and convergence. Therefore, the grid near the inlet must be encrypted. In addition, the multi-channel structure of the grid itself will also greatly increase the calculation grid (based on previous experience, the number of grids after the buried inlet is covered with a grid is about 8-10 times that before the grid is covered). With the surge in the number of grids, the computational cost increases significantly, so the current design cycle of the embedded air inlet fusion inlet grid is relatively long. Summary of the invention

[0005] In view of the problems of difficult grid division, high performance evaluation cost and long design cycle in the design of embedded inlet ducts with integrated inlet grids, the present invention proposes a fast equivalent flow field calculation method for embedded inlet ducts with integrated inlet grids. The basic idea of ​​this equivalent method is to load the complex influence of the grid on the airflow in the grid equivalent area through the momentum source term, and simulate the flow characteristics of the airflow through the real grid by setting the corresponding parameters, so as to simulate the influence of the inlet grid on the internal flow field of the embedded inlet duct. This method avoids the difficulty of direct CFD numerical simulation of the complex geometric configuration of the grid during the calculation process, and greatly reduces the calculation complexity and cost.

[0006] The technical solution of the present invention is:

[0007] The method for calculating the fast equivalent flow field of a buried air inlet fused with an inlet grid comprises the following steps:

[0008] Step 1: Through CFD numerical simulation, the flow field information of the submerged air intake duct without a grid and the flow field information of the submerged air intake duct with a grid under a certain working condition are obtained respectively;

[0009] Step 2: Establish a characteristic section near the bottom of the grid in the buried air inlet, and interpolate the flow field information of the buried air inlet without a grid and the flow field information of the buried air inlet with a grid to the characteristic section, respectively, to obtain the total pressure distribution of the characteristic section of the buried air inlet without a grid and the total pressure distribution of the characteristic section of the buried air inlet with a grid; and calculate the total pressure loss distribution of the characteristic section caused by the grid;

[0010] Step 3: Combined with the total pressure loss distribution of the characteristic section obtained in step 2 and the geometric characteristics of the grid, the equivalent flow field calculation under the set working conditions is realized by using the momentum source term; specifically, the following steps are included:

[0011] Step 3.1: Based on the total pressure loss distribution of the characteristic section obtained in step 2, the characteristic section is divided into several regions, and a certain set statistic reflecting the dispersion of the total pressure loss in a single region is not greater than a set threshold;

[0012] Step 3.2: Calculate the average total pressure loss of each area and combine the average total pressure loss of each area with the geometric characteristics of the grid according to the formula

[0013]

[0014] Calculate the unit flow resistance of the corresponding area along the flow direction; is the length of the grid in the flow direction, h is the thickness of the grid, is the grid diversion angle, is the unit flow resistance of the grid corresponding area in the x direction, is the unit flow resistance of the grid corresponding area in the z direction, is the average total pressure loss in the corresponding area, and After vector superposition, the unit flow resistance of the grid corresponding area along the flow direction is obtained;

[0015] Step 3.3: Replace the flow field grid of the actual grid area with an equivalent area grid; the equivalent area is a number of areas obtained by dividing the area divided by the characteristic cross section on the grid, and the equivalent area is grid-divided to obtain the equivalent area grid;

[0016] Step 3.4: For a certain working condition that needs to be calculated, use the equivalent grid to calculate the buried inlet flow field in the grid state, in which the unit flow resistance of the grid corresponding area along the flow direction is integrated into the momentum conservation equation in the form of a momentum source term. In the flow field calculation, the flow field is iterated and updated so that the airflow flowing through the grid equivalent area is subject to the same effect as the airflow flowing through the real grid, thereby realizing the equivalent flow field calculation.

[0017] Furthermore, when the flow field information of the embedded air inlet is obtained through CFD numerical simulation, part of the aircraft body upstream of the embedded air inlet is retained.

[0018] Furthermore, when performing CFD numerical simulation in step 1, the embedded air inlet with and without grids is meshed, where the maximum grid size of the far field of the computational domain is 500 mm, the maximum grid size of the aircraft body and the air inlet surface is 3 mm, the minimum grid size is 0.5 mm, the number of boundary layers is set to 10, the first layer grid height is 0.1 mm, and the growth rate is 1.2.

[0019] Furthermore, in step 2, a characteristic section is created in the embedded air intake duct at a position 1 mm away from the bottom of the grid, and a surface mesh of the characteristic section is generated.

[0020] Furthermore, in step 3.1, the statistic is characterized by range or variance.

[0021] Furthermore, in step 3.3, the equivalent region grid is not encrypted, and the grid volume is lower than the actual grid region grid volume.

[0022] Beneficial effects:

[0023] As an equivalent method for the complex structure of the embedded air intake duct with integrated inlet grid in CFD calculation, the present invention has the characteristics of high calculation efficiency, high flow field restoration degree and simple equivalent method, breaking through the limitations of difficult grid division, too large number of grids and low calculation efficiency in CFD calculation of the embedded air intake duct with integrated inlet grid, and also provides a new idea for CFD calculation of small-sized and complex-structured components. Based on this method, the design cycle of the embedded air intake duct with integrated inlet grid can be greatly shortened and the performance evaluation efficiency can be improved.

[0024] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0026] Figure 1 :Flowchart of the fast equivalent flow field calculation method for the buried inlet duct with integrated inlet grid;

[0027] Figure 2 : Typical embedded air inlet configuration and front view of aircraft body;

[0028] Figure 3 : Figure 2 A top view of

[0029] Figure 4 : Schematic diagram of the geometric model of the non-grid embedded inlet;

[0030] Figure 5 : Schematic diagram of the geometric model of the buried inlet duct with an inlet grid;

[0031] Figure 6 : Grid 3D view;

[0032] Figure 7 : The surface mesh of the buried air inlet without grid;

[0033] Figure 8 : The surface grid of the buried air inlet covered with grid;

[0034] Fig. 9 : far-field grid of computational domain;

[0035] Fig.10 : The grid at the symmetry surface (taking no grid as an example);

[0036] Fig.11 : Total pressure distribution cloud diagram of the gridless buried inlet along the flow direction;

[0037] Fig.12 : Total pressure distribution cloud diagram of the buried inlet covered with grid along the flow direction;

[0038] Fig.13 : Schematic diagram of characteristic section position;

[0039] Fig.14 : Schematic diagram of characteristic cross section;

[0040] Fig.15 : Schematic diagram of characteristic cross-section mesh;

[0041] Fig.16 : Total pressure distribution of non-grid characteristic section;

[0042] Fig.17 : Total pressure distribution in grid characteristic section;

[0043] Fig.18 : Total pressure loss distribution of characteristic cross section;

[0044] Fig.19 : Partition diagram;

[0045] Fig. 20 : Schematic diagram of grid structure;

[0046] Fig.21 : Actual grid and equivalent area geometric model; DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0048] The CFD numerical simulation method has certain limitations when facing complex geometric models. Therefore, in actual engineering, there are problems of high cost and low efficiency when designing and evaluating the performance of the embedded air inlet with a fused inlet grid. In order to improve the CFD calculation efficiency of the embedded air inlet with a fused inlet grid and shorten the design cycle of the embedded air inlet with a fused inlet grid, this embodiment proposes a fast equivalent flow field calculation method for the embedded air inlet with a fused inlet grid. The method establishes a connection between the momentum source term in the momentum equation and the geometric parameters and flight conditions of the grid, and replaces the CFD calculation grid of the actual grid structure by reasonably setting the momentum source term, thereby achieving the equivalence of the grid and the rapid evaluation of the intake performance of the embedded air inlet with a fused inlet grid.

[0049] like Figure 1 As shown, the specific steps include:

[0050] Step 1: Through CFD numerical simulation, the flow field information of the submerged air inlet duct without a grid and with a grid under a certain working condition are obtained respectively.

[0051] The embedded air inlet is designed to be embedded in the fuselage or wing of the aircraft. Its structure is relatively complex and more sensitive than ordinary air inlets. When designing, factors such as the curved surface shape of the aircraft upstream of the air inlet entrance and the boundary layer effect need to be considered to achieve a good airflow guidance effect. Therefore, when evaluating its performance and analyzing its flow characteristics, it is often necessary to retain part of the aircraft body upstream of the embedded air inlet, so as to restore the impact of the aircraft body on the airflow during actual flight.

[0052] The typical embedded air inlet configuration and aircraft body used in this embodiment are as follows: Figure 2 and Figure 3 As shown. The cross-sectional shape of the fuselage is a rounded rectangle, and the embedded air inlet is located on the lower belly plane of the aircraft body. For ease of observation, the upper and lower surfaces of the aircraft body are inverted in subsequent pictures. The cross-section of the air inlet outlet is circular with a diameter of D=65mm. The air inlet length is 5.48D, and the centerline offset is 0.88D. The air inlet inlet is a rectangle with a length and width of 1.78D and 0.84D respectively. The front lip guide angle and the rear lip guide angle are both 22.5°. The geometric model of the air inlet before and after the grid is added is shown in the figure. Figure 4 and Figure 5 The grid 3D view is shown as Figure 6 As shown, the grid thickness is 5.38 mm, the characteristic size of the grid holes is 10 mm, and the grid diversion angle is 22.5°.

[0053] During CFD numerical simulation, the embedded air intake with and without grids is first meshed. This embodiment uses full-mode meshes for calculation. The object surface meshes, computational domain far fields, and meshes on the symmetry plane of the embedded air intake with and without grids are shown in Figure 1. Figure 7~Figure 10 As shown. The computational domain is a cuboid with dimensions of 30m in length, 10m in width and 10m in height. The maximum grid size of the computational domain far field is 500mm, the maximum grid size of the aircraft body and the air inlet surface is 3mm, and the minimum grid size is 0.5mm. Too dense boundary layer grids will result in low grid quality and reduce the accuracy of the calculation. Therefore, the boundary layer grids are appropriately adjusted to maintain the accuracy of the simulation. In this embodiment, the final number of boundary layers is set to 10, the first layer grid height is 0.1mm, and the growth rate is 1.2. The number of volume grids of the embedded air inlet benchmark configuration is approximately 1 million.

[0054] Then, numerical simulations are performed on the embedded inlet with and without grids. The numerical simulation conditions in this embodiment are: the incoming flow Mach number is 0.7, the inlet exit Mach number is 0.4, and the sideslip angle and angle of attack are both 0°. The flow field information in the calculation domain with and without grids is obtained, including the total pressure distribution, static pressure distribution, and velocity distribution in the flow field. In this embodiment, the main focus is on the total pressure distribution in the flow field, such as Fig.11 and Fig.12 As shown, there are cloud diagrams of the total pressure distribution along the flow direction of the buried air inlet with and without the grid.

[0055] Step 2: Establish a characteristic section near the bottom of the grid in the buried air inlet, and interpolate the flow field information of the buried air inlet without a grid and the flow field information of the buried air inlet with a grid to the characteristic section respectively, to obtain the total pressure distribution of the characteristic section of the buried air inlet without a grid and the total pressure distribution of the characteristic section of the buried air inlet with a grid; and calculate the total pressure loss distribution of the characteristic section caused by the grid.

[0056] In this embodiment, a section is created in the embedded air intake duct at a distance of 1 mm from the bottom of the grid, which is called the characteristic section. The size of the characteristic section depends on the size of the section surface of the embedded air intake duct at a distance of 1 mm from the bottom of the grid. Fig.13 Then generate the surface mesh of the characteristic section with a mesh size of 1 mm. The characteristic section and its surface mesh are shown in Fig.14 and Fig.15 Then, the flow field data of the embedded inlet with and without grids are interpolated to the characteristic cross section, and the total pressure distribution of the embedded inlet characteristic cross section without grid and the total pressure distribution of the embedded inlet characteristic cross section with grid are obtained. The total pressure distribution on the characteristic cross section with and without grid is shown in Fig.16 and Fig.17 shown.

[0057] Since the characteristic cross-section grids used in interpolation are exactly the same, the grid nodes are completely corresponding. Therefore, the total pressure loss distribution caused by the grid is obtained by the difference in total pressure data on the corresponding grid nodes on the characteristic cross-section with and without the grid. The calculation formula is shown below.

[0058]

[0059] Where: is the total pressure loss value of the corresponding grid node on the characteristic section; is the total pressure of the corresponding node on the characteristic section in the non-grid state; is the total pressure at the corresponding node on the characteristic section with grid.

[0060] The above method can be used to obtain the total pressure loss distribution of the characteristic cross section caused by the grid. The total pressure loss distribution of the characteristic cross section is as follows: Fig.18 shown.

[0061] Step 3: Combined with the total pressure loss distribution of the characteristic section obtained in step 2 and the geometric characteristics of the grid, the momentum source term is used to realize the equivalent flow field calculation under other working conditions.

[0062] First, based on the total pressure loss distribution of the characteristic section caused by the grid obtained in step 2, the characteristic section is divided into several regions, and a set statistic reflecting the discreteness of the total pressure loss in a single region is not greater than a set threshold. The statistic can be characterized by a range or variance, and the range or variance of the total pressure loss in a single region is not greater than the set threshold.

[0063] In this embodiment, Fig.19 As shown, the characteristic cross section is divided into eleven regions, namely L1, R1, and F1 to F9. Fig.18 From the total pressure loss distribution of the characteristic cross section shown, it can be clearly observed that there are obvious low-pressure areas on the left and right sides. Therefore, the shapes of these two low-pressure areas are divided into separate areas (L1, R1). The high-pressure area in the middle part gradually increases from front to back (red part). Considering that there may be more changes in the leading edge and trailing edge, more areas are divided in the leading edge and trailing edge areas (F1~F9).

[0064] Then the average total pressure loss of each area is calculated by integration, and the average total pressure loss of each area is combined with the geometric characteristics of the grid according to the formula

[0065]

[0066] Calculate the unit flow resistance of the corresponding area along the flow direction; Fig. 20 As shown, is the length of the grid in the flow direction, h is the thickness of the grid, is the grid diversion angle, is the unit flow resistance of the grid corresponding area in the x direction, is the unit flow resistance of the grid corresponding area in the z direction, is the average total pressure loss in the corresponding area, and After vector superposition, the unit flow resistance of the grid corresponding area is obtained.

[0067] Then replace the flow field grid of the actual grid area with the equivalent area grid. The equivalent area is a number of areas obtained by dividing the area divided by the characteristic cross section onto the grid. The geometric model of the actual grid and the equivalent area is as follows: Fig.21 As shown. Then the equivalent area is meshed, and the mesh of the actual grid area is replaced with the mesh of the equivalent area. When using the real grid for CFD calculations, the flow field near the grid is a separate grid area, and the flow field of the air inlet and the rest of the area is a region. These two grid areas are spliced ​​into an overall calculation grid through the interface. However, due to the large number of sharp boundaries and narrow spaces in the grid geometry model, the flow field grid area near the grid is encrypted. With the surge in the number of grids, the computational cost is significantly increased; when the equivalent area is meshed, due to the simple structure of the equivalent area geometry model, there is no need to encrypt the grid area, and the amount of grids is significantly reduced. After replacing the mesh of the actual grid area with the mesh of the equivalent area, the mesh of the equivalent area is spliced ​​into a whole with the mesh area of ​​the air inlet and the rest of the flow field through the interface.

[0068] For a certain working condition that needs to be calculated, when reusing the equivalent grid for flow field calculation, the unit flow resistance of the grid corresponding area along the flow direction is incorporated into the momentum conservation equation in the form of momentum source term:

[0069]

[0070] In CFD calculation, by iterating and updating the flow field, the airflow flowing through the grid equivalent area is subjected to the same effect as the airflow flowing through the real grid, thereby realizing the equivalent flow field calculation. In the above momentum conservation equation, f is the unit flow resistance of the corresponding area. During CFD calculation, after the momentum source term is loaded in the corresponding area, the calculation can reflect the additional resistance of the airflow when it flows through the grid area. Therefore, the calculated flow state of the flow field will change. By iterating and updating the flow field during the calculation process, the calculated flow state of the flow field will eventually gradually converge and stabilize.

[0071] As mentioned above, when meshing the equivalent area, due to the simple structure of the geometric model of the equivalent area, there is no need to encrypt the grid area, and the amount of grids is significantly reduced, so the calculation efficiency is greatly improved, thereby enabling the rapid equivalent flow field calculation of the embedded inlet duct with a fused inlet grid. When subsequently calculating the flow field under different working conditions, there is no need to use the actual grid grid for calculation, but the equivalent area grid can be used for rapid equivalent flow field calculation.

[0072] Method Validation:

[0073] Since there is a gap between the calculation results of the equivalent method and the direct calculation of the real grid, in order to control the error within an acceptable range, we take the total pressure recovery characteristics and distortion index of the inlet outlet section, which are the most concerned in the inlet design and performance evaluation, as the object, and compare the error between the actual grid calculation results and the grid equivalent method proposed in this invention. The calculation conditions are as follows: the incoming flow Mach number is 0.7, the inlet outlet Mach number is 0.4, the sideslip angle and the angle of attack are both 0°, and the calculation errors are shown in Table 1.

[0074] Table 1 Calculation accuracy and number of grids of equivalent method and real grid

[0075]

[0076] As shown in Table 1, the relative error of the total pressure recovery coefficient between the equivalent method and the actual grid calculation result is 1.2%, and the relative error of the distortion rate is 3.1%, both of which are less than 5%. Therefore, the method proposed in the present invention can basically reflect the flow characteristics of the embedded inlet duct with fused inlet grid, and the distribution position and range of the high and low pressure areas are basically consistent with the actual grid calculation results, and the calculation efficiency is greatly improved, which meets the demand for rapid evaluation of the intake performance of the embedded inlet duct with fused inlet grid.

[0077] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for calculating the fast equivalent flow field of a submerged inlet fused with an inlet grid, characterized by: The following steps are involved: Step 1: Through CFD numerical simulation, the flow field information of the submerged air intake duct without a grid and the flow field information of the submerged air intake duct with a grid under a certain working condition are obtained respectively; Step 2: Establish a characteristic section near the bottom of the grid in the buried air inlet, and interpolate the flow field information of the buried air inlet without a grid and the flow field information of the buried air inlet with a grid to the characteristic section, respectively, to obtain the total pressure distribution of the characteristic section of the buried air inlet without a grid and the total pressure distribution of the characteristic section of the buried air inlet with a grid; and calculate the total pressure loss distribution of the characteristic section caused by the grid; Step 3: Combined with the total pressure loss distribution of the characteristic section obtained in step 2 and the geometric characteristics of the grid, the momentum source term is used to realize the equivalent flow field calculation under the set working conditions; specifically, the following steps are included: Step 3.1: Based on the total pressure loss distribution of the characteristic section obtained in step 2, the characteristic section is divided into several regions, and a certain set statistic reflecting the dispersion of the total pressure loss in a single region is not greater than a set threshold; Step 3.2: Calculate the average total pressure loss of each area and combine the average total pressure loss of each area with the geometric characteristics of the grid according to the formula Calculate the unit flow resistance of the corresponding area along the flow direction; is the length of the grid in the flow direction, h is the thickness of the grid, is the grid diversion angle, is the unit flow resistance of the grid corresponding area in the x direction, is the unit flow resistance of the grid corresponding area in the z direction, is the average total pressure loss in the corresponding area, and After vector superposition, the unit flow resistance of the grid corresponding area along the flow direction is obtained; Step 3.3: Replace the flow field grid of the actual grid area with an equivalent area grid; the equivalent area is a number of areas obtained by dividing the area divided by the characteristic cross section on the grid, and the equivalent area is grid-divided to obtain the equivalent area grid; Step 3.4: For a certain working condition that needs to be calculated, use the equivalent grid to calculate the buried inlet flow field in the grid state, in which the unit flow resistance of the grid corresponding area along the flow direction is integrated into the momentum conservation equation in the form of a momentum source term. In the flow field calculation, the flow field is iterated and updated so that the airflow flowing through the grid equivalent area is subject to the same effect as the airflow flowing through the real grid, thereby realizing the equivalent flow field calculation.

2. According to claim 1, a method for calculating the fast equivalent flow field of a submerged air inlet fused with an inlet grid is characterized by: When the flow field information of the embedded air inlet is obtained through CFD numerical simulation, part of the aircraft body upstream of the embedded air inlet is retained.

3. According to claim 1, a method for calculating the fast equivalent flow field of a submerged air inlet fused with an inlet grid is characterized by: When performing CFD numerical simulation in step 1, the embedded air inlet with and without grids is meshed, where the maximum grid size of the far field of the computational domain is 500 mm, the maximum grid size of the aircraft body and the air inlet surface is 3 mm, the minimum grid size is 0.5 mm, the number of boundary layers is set to 10, the first layer grid height is 0.1 mm, and the growth rate is 1.

2.

4. According to claim 1, a method for calculating the fast equivalent flow field of a submerged air inlet fused with an inlet grid is characterized by: In step 2, a characteristic section is created 1 mm from the bottom of the grid in the buried air intake duct, and a surface mesh of the characteristic section is generated.

5. According to claim 1, a method for calculating the fast equivalent flow field of a submerged air inlet fused with an inlet grid is characterized by: In step 3.1, the statistic is characterized by range or variance.

6. According to claim 1, a method for calculating the fast equivalent flow field of a submerged air inlet fused with an inlet grid is characterized by: In step 3.3, the equivalent area grid is not encrypted, and the grid volume is lower than the actual grid area grid volume.

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