Method and system for simulating aircraft plume based on similar drop pressure ratio and momentum ratio
Patent Information
- Application Number
- CN202611096690.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-23
- Publication Date
- 2026-08-18
AI Technical Summary
[0004]因此，在利用相似准则进行喷流相似模拟时，一般不能保证所有的相似参数都一致，如上述的动量比和静压比相似的喷流模拟方法，其并不能保证除此之二者外的其他相似参数一致
1、本发明基于动量比相似特性保障了喷流出口动量的一致性，精准复现喷流推力的主要贡献部分，使等效模拟喷流的推力水平与实际燃气介质喷流推力高度契合，同时真实还原喷流对自由来流的冲击效应，大幅提升喷流与飞行器流场干扰模拟结果的可靠性；同时，本发明基于落压比相似确保了喷流总压的等效匹配，在等熵假设前提下，实现喷流机械能的一致性模拟，保证喷流与来流相互作用过程中能量传递、转化规律的准确性，避免因能量特性偏差引发的流场模拟失真，进一步强化喷流-来流耦合干扰的模拟精度。
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Figure CN122595930A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft jet aerodynamic control technology, and in particular to an aircraft jet simulation method and system based on the similarity between drop pressure ratio and momentum ratio. Background Technology
[0002] Jet propulsion is a common power and control mechanism used in advanced aircraft, primarily encompassing two categories: main engine vectoring and lateral jet reaction control systems (RCS). When an aircraft immersed in the atmosphere uses or activates its onboard jet propulsion control system, it is not only affected by the direct force generated by the jet (i.e., jet thrust), but also by the jet interference force generated by the interaction between the jet and the free flow (where there is a relative velocity between the atmosphere and the aircraft). This makes the aerodynamic characteristics of the aircraft under jet propulsion complex and difficult to predict accurately. Currently, the prediction of the aerodynamic characteristics of aircraft under jet interference mainly relies on wind tunnel testing or numerical calculations. In engineering, when using these two methods for jet interference prediction, certain jet similarity criteria are typically employed to transform complex jets with multiple components of combustion gases into jets with a single medium (such as air), thereby reducing the difficulty of testing or the amount of computation.
[0003] In current engineering practice, the jet similarity criterion generally adopts the method of similarity between the nozzle exit momentum ratio (the ratio of jet momentum to incoming momentum) and the nozzle exit static pressure ratio (the ratio of jet static pressure to incoming static pressure). According to the one-dimensional jet thrust formula, this method simulates the direct force of the jet and ensures that the momentum ratio and static pressure ratio are equal between the gas medium jet and the single-medium jet. Existing research shows that this similarity method usually has good accuracy in simulating transverse jets. However, in addition to the two similarity parameters mentioned above, there are many other similarity parameters for jet interference, such as the exit Mach number and the pressure drop ratio (the ratio of total jet pressure to incoming static pressure).
[0004] Therefore, when using similarity criteria to perform jet similarity simulation, it is generally not possible to guarantee that all similarity parameters are consistent. For example, the jet simulation method mentioned above, which uses momentum ratio and static pressure ratio similarity, cannot guarantee that other similarity parameters besides these two are consistent. Summary of the Invention
[0005] To address the aforementioned issues, this invention proposes a method and system for simulating aircraft jet flow based on the similarity of pressure ratio and momentum ratio. This method can equivalently simulate any gas medium jet as a jet of a single medium and provides a calculation method for the equivalent nozzle shape. It can provide a jet flow simplification and equivalence strategy for wind tunnel testing and numerical calculation, and can, to a certain extent, ensure the consistency of the jet thrust principal quantity and mechanical energy under isentropic conditions during jet-flow interference.
[0006] The technical solution adopted in this invention is as follows: A method for simulating aircraft jet flow based on the similarity between drop pressure ratio and momentum ratio includes: Based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated, calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft. Based on the momentum ratio similarity and pressure ratio similarity criteria, the unit time momentum and total pressure of the simulated jet at the nozzle exit are calculated after similarity comparison. Based on the one-dimensional isentropic formula, the relationship between momentum and total pressure with respect to static pressure and Mach number at the nozzle exit is combined to solve for the static pressure and Mach number corresponding to the simulated jet. Combining the isentropic assumption and the principle of flow conservation within the nozzle, the area of the nozzle throat after similarity comparison is solved by using the area ratio between the nozzle outlet and the nozzle throat. Based on the size relationship of the nozzle throat before and after similarity comparison, a new nozzle throat is designed according to the original nozzle shape to obtain a nozzle shape that is suitable for simulated jet flow.
[0007] Furthermore, the calculation of the unit-time momentum and total pressure at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated includes: Based on the ideal gas law Formula for the speed of sound ,in For static pressure, For density, The gas constant is... For static temperature, At the speed of light, The specific heat ratio of the gas is given; for any supersonic exit nozzle, the static pressure of the gas medium jet at the nozzle exit is known. ,Mach number Specific heat ratio of gases and nozzle exit area Calculate the momentum per unit time of the gas medium jet at the nozzle exit. :
[0008] in, The density of the gas medium jet. The velocity of the gas medium jet; Based on the one-dimensional isentropic relationship, the total pressure of the gas medium jet at the nozzle outlet is calculated. : .
[0009] Furthermore, the calculation of the unit-time momentum and total pressure at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated also includes: The static pressure of a real free flow is known. ,Mach number Specific heat ratio of gases Calculate the momentum per unit time of the actual free flow at the nozzle exit. :
[0010] The static pressure of the free flow to be simulated is known. ,Mach number Specific heat ratio of gases Calculate the momentum of the free flow to be simulated at the nozzle exit per unit time. : .
[0011] Furthermore, the calculation of the unit-time momentum and total pressure of the simulated jet at the nozzle exit after similarity comparison, based on the momentum ratio similarity and pressure ratio similarity criteria, includes: Let the momentum per unit time of the simulated jet at the nozzle exit after analogy be . Based on the similarity of momentum ratios, we have:
[0012] Let the total pressure of the simulated jet at the nozzle exit be . Based on the similarity of the drop pressure ratio, we have:
[0013] Therefore, the unit-time momentum and total pressure of the simulated jet at the nozzle exit after analogy are obtained as follows:
[0014] .
[0015] Furthermore, the method of solving for the static pressure and Mach number corresponding to the simulated jet by simultaneously solving the relationship between momentum and total pressure with respect to static pressure and Mach number at the nozzle exit, based on the one-dimensional isentropic formula, includes: The specific heat ratio of the simulated jet is known to be... Let the Mach number of the simulated jet at the nozzle exit be . And the static pressure is According to the one-dimensional isentropic formula, we get:
[0016]
[0017] Solving the simultaneous equations yields a set of variables and The nonlinear equations are solved using numerical methods to obtain the static pressure and Mach number corresponding to the simulated jet.
[0018] Furthermore, the method of combining the isentropic assumption and the principle of flow conservation within the nozzle, and using the area ratio between the nozzle exit and the nozzle throat to solve for the nozzle throat area after similarity comparison, includes: Known similarity comparison nozzle throat area And let the area of the nozzle throat after the similar analogy be denoted as . For the nozzle throat after analogy, the nozzle throat area is obtained based on the one-dimensional isentropic formula and the fact that the flow rates of any two cross sections within the nozzle are equal. With nozzle exit area Relationship:
[0019] For a supersonic exit nozzle, the Mach number of its nozzle throat is... Then, the nozzle throat area after similarity comparison is calculated. .
[0020] Furthermore, the step of designing a new nozzle throat based on the size relationship of the nozzle throat before and after similarity comparison, and obtaining a nozzle shape adapted to the simulated jet flow, includes: like In this case, the nozzle does not need to be redesigned, and the original nozzle can be used directly for simulation.
[0021] like If the area of the nozzle throat after analogy is larger than that of the original nozzle throat, then a cross-section perpendicular to the jet exit direction is selected in the expansion section of the original nozzle, such that the area of this cross-section is equal to... .
[0022] like If the area of the nozzle throat after analogy is smaller than that of the original nozzle throat, then at one end of the throat of the original nozzle expansion section, the nozzle profile is smoothly extended in the opposite direction of jet ejection, and a cross-section perpendicular to the jet ejection direction is selected on the extended curved surface, such that the area of this cross-section is equal to... Thus, the shape of the nozzle expansion section after similar analogy is obtained.
[0023] A jet jet simulation system based on the similarity between drop pressure ratio and momentum ratio includes: The momentum and total pressure calculation module is configured to calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated. The similarity module is configured to calculate the unit time momentum and total pressure of the simulated jet at the nozzle exit based on momentum ratio similarity and pressure ratio similarity criteria. The static pressure and Mach number calculation module is configured to solve for the static pressure and Mach number of the simulated jet by combining the momentum and total pressure with respect to the static pressure and Mach number at the nozzle exit using the one-dimensional isentropic formula. The nozzle throat area calculation module is configured to combine the isentropic assumption and the principle of flow conservation in the nozzle, and use the area ratio between the nozzle outlet and the nozzle throat to solve for the nozzle throat area after similarity comparison. The nozzle shape adjustment module is configured to design a new nozzle throat based on the size relationship of the nozzle throat before and after similar analogy, thereby obtaining a nozzle shape that is adapted to the simulated jet.
[0024] The beneficial effects of this invention are as follows: 1. This invention ensures the consistency of jet outlet momentum based on momentum ratio similarity, accurately reproduces the main contribution of jet thrust, and makes the thrust level of the equivalent simulated jet highly consistent with the actual gas medium jet thrust. At the same time, it realistically restores the impact effect of the jet on the free flow, greatly improving the reliability of the simulation results of jet and aircraft flow field interference. In addition, this invention ensures the equivalent matching of jet total pressure based on pressure ratio similarity. Under the assumption of isentropicity, it achieves consistent simulation of jet mechanical energy, ensuring the accuracy of energy transfer and conversion laws during the interaction between jet and incoming flow, avoiding flow field simulation distortion caused by energy characteristic deviation, and further enhancing the simulation accuracy of jet-incoming flow coupling interference.
[0025] 2. This invention, through the linkage isentropic formula and the principle of nozzle flow conservation, can accurately solve key geometric parameters such as the throat area of the equivalent nozzle, thereby completing the nozzle shape design adapted to the simulated jet flow and forming a complete jet flow simulation solution. It not only adapts to the jet flow simulation needs under various working conditions, but also provides theoretical support for the optimized design of aircraft nozzle structures, and has both good theoretical value and engineering application prospects. Attached Figure Description
[0026] Figure 1 This is a flowchart of an aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio, according to Embodiment 1 of the present invention.
[0027] Figure 2 This is one of the schematic diagrams of the front and rear nozzle throats in a similar analogy to Embodiment 1 of the present invention.
[0028] Figure 3 This is the second schematic diagram of the front and rear nozzle throats in similar analogy to Embodiment 1 of the present invention. Detailed Implementation
[0029] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0030] Example 1 like Figure 1 As shown, this embodiment provides a method for simulating aircraft jet flow based on the similarity between drop pressure ratio and momentum ratio, including: Based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated, calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft. Based on the momentum ratio similarity and pressure ratio similarity criteria, the unit time momentum and total pressure of the simulated jet at the nozzle exit are calculated after similarity comparison. Based on the one-dimensional isentropic formula, the relationship between momentum and total pressure with respect to static pressure and Mach number at the nozzle exit is combined to solve for the static pressure and Mach number corresponding to the simulated jet. Combining the isentropic assumption and the principle of flow conservation within the nozzle, the area of the nozzle throat after similarity comparison is solved by using the area ratio between the nozzle outlet and the nozzle throat. Based on the size relationship of the nozzle throat before and after similarity comparison, a new nozzle throat is designed according to the original nozzle shape to obtain a nozzle shape that is suitable for simulated jet flow.
[0031] It should be noted that this method selects the jet momentum ratio and drop pressure ratio as similarity parameters for jet simulation, mainly based on the following considerations: (1) The momentum ratio ensures the consistency of jet outlet momentum. According to the one-dimensional thrust formula, jet thrust consists of two parts: mass flow thrust and static pressure difference (the difference between jet static pressure and ambient pressure). The former is the product of jet flow rate and outlet area at the outlet, while the latter is the product of jet static pressure difference and outlet area at the outlet. For general supersonic nozzles, the former is much larger than the latter, meaning that the former is the main contributor to jet thrust. Therefore, ensuring the consistency of outlet momentum makes the jet thrust after similaration approximately close to that before similaration. At the same time, momentum is an important characteristic of jet impact effect, and ensuring the consistency of this parameter can also simulate the impact of the jet on the incoming flow to a certain extent.
[0032] (2) The pressure drop ratio ensures the consistency of the total jet pressure. Under the isentropic assumption, the total jet pressure characterizes the magnitude of mechanical energy in the jet. Ensuring the consistency of the total jet pressure can further ensure the consistency of the mechanical energy simulation when the jet interacts with the incoming flow. In this method, when performing jet similarity simulation, based on the isentropic expansion formula of the supersonic exit jet, it is necessary to recalculate and adjust the geometric dimensions of some features of the nozzle accordingly, and finally obtain the similar nozzle shape.
[0033] Preferably, the step of calculating the unit-time momentum and total pressure at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated includes: Based on the ideal gas law Formula for the speed of sound ,in For static pressure, For density, The gas constant is... For static temperature, At the speed of light, The specific heat ratio of the gas is given; for any supersonic exit nozzle, the static pressure of the gas medium jet at the nozzle exit is known. ,Mach number Specific heat ratio of gases and nozzle exit area Calculate the momentum per unit time of the gas medium jet at the nozzle exit. : (1) in, The density of the gas medium jet. The velocity of the gas medium jet; Based on the one-dimensional isentropic relationship, the total pressure of the gas medium jet at the nozzle outlet is calculated. : (2).
[0034] Similarly, given the static pressure of a real free flow... ,Mach number Specific heat ratio of gases Calculate the momentum per unit time of the actual free flow at the nozzle exit. (Here, use subscript) fs_ 1 represents actual free flow). (3) Similarly, the static pressure of the free flow to be simulated (by wind tunnel testing or numerical calculation) is known. ,Mach number Specific heat ratio of gases Calculate the momentum of the free flow to be simulated at the nozzle exit per unit time. (Here, use subscript) fs_ 2 indicates the free flow to be simulated). (4).
[0035] Preferably, the step of calculating the unit-time momentum and total pressure of the simulated jet at the nozzle exit based on momentum ratio similarity and pressure ratio similarity criteria includes: Let the momentum per unit time of the simulated jet at the nozzle exit after analogy be . Based on the similarity of momentum ratios, we have: (5) Let the total pressure of the simulated jet at the nozzle exit be . Based on the similarity of the drop pressure ratio, we have: (6) Therefore, the unit-time momentum and total pressure of the simulated jet at the nozzle exit after analogy are obtained as follows: (7) (8).
[0036] Preferably, the step of solving for the static pressure and Mach number corresponding to the simulated jet by simultaneously solving the relationship between momentum and total pressure with respect to static pressure and Mach number at the nozzle exit, based on the one-dimensional isentropic formula, includes: For the jet (single) medium to be simulated in wind tunnel tests or numerical calculations, its gas specific heat ratio is known to be... Let the Mach number of the simulated jet at the nozzle exit be . And the static pressure is According to the one-dimensional isentropic formula, we get: (9) (10) Solving the simultaneous equations yields a set of variables and The nonlinear equations are solved using numerical methods to obtain the static pressure and Mach number corresponding to the simulated jet.
[0037] Preferably, the step of combining the isentropic assumption and the principle of flow conservation within the nozzle, and using the area ratio between the nozzle outlet and the nozzle throat to solve for the nozzle throat area after similarity comparison, includes: Known similarity comparison nozzle throat area And let the area of the nozzle throat after the similar analogy be denoted as . For the nozzle throat after analogy, the nozzle throat area is obtained based on the one-dimensional isentropic formula and the fact that the flow rates of any two cross sections within the nozzle are equal. With nozzle exit area Relationship: (11) For a supersonic exit nozzle, the Mach number of its nozzle throat is... Then, the nozzle throat area after similarity comparison is calculated. .
[0038] Under normal circumstances, and They are not necessarily equal, therefore the nozzle expansion section after analogy needs to be redesigned in order to conduct subsequent wind tunnel tests or numerical calculations. The goal is to make the throat area of the redesigned nozzle equal to... .
[0039] Preferably, the step of designing a new nozzle throat based on the size relationship of the nozzle throat before and after similarity comparison, and obtaining a nozzle shape adapted to the simulated jet flow, includes: like If so, the nozzle does not need to be redesigned and the original nozzle can be used directly for simulation.
[0040] like That is, the area of the nozzle throat after similarity comparison is larger than the area of the original nozzle throat. A cross-section perpendicular to the jet exit direction can be selected in the expansion section of the original nozzle, such that the area of this cross-section is equal to the area of the jet exit direction. ,like Figure 2 As shown.
[0041] like That is, the area of the nozzle throat after similarity comparison is smaller than the area of the original nozzle throat. At one end of the throat of the original nozzle expansion section, the nozzle profile can be smoothly extended in the opposite direction of jet ejection. A cross-section perpendicular to the jet ejection direction can be selected on the extended curved surface, such that the area of this cross-section is equal to... ,like Figure 3As shown, the shape of the nozzle expansion section after similar analogy is obtained.
[0042] Accordingly, this embodiment also provides an aircraft jet flow simulation system based on the similarity between the drop pressure ratio and momentum ratio, including: The momentum and total pressure calculation module is configured to calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated. The similarity module is configured to calculate the unit time momentum and total pressure of the simulated jet at the nozzle exit based on momentum ratio similarity and pressure ratio similarity criteria. The static pressure and Mach number calculation module is configured to solve for the static pressure and Mach number of the simulated jet by combining the momentum and total pressure with respect to the static pressure and Mach number at the nozzle exit using the one-dimensional isentropic formula. The nozzle throat area calculation module is configured to combine the isentropic assumption and the principle of flow conservation in the nozzle, and use the area ratio between the nozzle outlet and the nozzle throat to solve for the nozzle throat area after similarity comparison. The nozzle shape adjustment module is configured to design a new nozzle throat based on the size relationship of the nozzle throat before and after similar analogy, thereby obtaining a nozzle shape that is adapted to the simulated jet.
[0043] Example 2 This embodiment is based on embodiment 1: This embodiment provides a method for simulating aircraft jet flow based on the similarity between drop pressure ratio and momentum ratio, including: Step 1: Given the outlet static pressure of the gas medium jet The pressure is 138175.65 Pa, and the nozzle exit Mach number is... The specific heat ratio of the nozzle outlet gas is 3.2. The value is 1.18 and the nozzle exit area. It is 0.002m 2 Then, from equation (1), the momentum per unit time at the outlet of the gas medium jet can be obtained. The total pressure at the outlet of the gas medium jet is 3339.21 N. From equation (2), the total pressure can be obtained. The value is 10,000,000.00 Pa.
[0044] Given the static pressure of the actual free-flowing airflow The Pa is 1197.03, and the Mach number is... The specific heat ratio is 6.0 and the specific heat ratio of the gas. If the value is 1.4, then from equation (3), we can obtain the momentum of the actual free-flowing jet per unit time at the nozzle exit. It is 120.66N.
[0045] Given the static pressure of the free flow in the wind tunnel test or numerical calculation to be simulated. The Pa is 633.36, and the Mach number is... The specific heat ratio is 6.0 and the specific heat ratio of the gas. If the value is 1.4, then from equation (4), the momentum of the free flow at the nozzle exit per unit time, which is to be simulated by wind tunnel testing or numerical calculation, can be obtained. It is 63.84N.
[0046] Step 2: Calculate the momentum per unit time at the jet outlet after similarity comparison using equations (7) and (8). The total pressure at the outlet is 1766.81 N. The value is 5291106.24 Pa.
[0047] Step 3: Solve the nonlinear equations (9) and (10) simultaneously using the bisection method to obtain the Mach number of the jet (single) medium at the outlet for the wind tunnel test or numerical calculation to be simulated. The static pressure of the jet at the outlet is 3.85213. The value is 42523.55 Pa.
[0048] Step 4: Given the nozzle throat area before similarity comparison It is 0.0002066m 2 From equation (11), the nozzle throat area after similarity comparison can be obtained. It is 0.0002131m 2 .
[0049] Step 5: Due to the following in this embodiment This falls under the second category. Therefore, a cross-section perpendicular to the jet exit direction is cut within the original nozzle expansion section to construct the analog nozzle throat surface. The area of the cut cross-section must be equal to... (0.0002131m) 2 ),like Figure 2 As shown.
[0050] Example 3 This embodiment is based on embodiment 1: This embodiment provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the aircraft jet simulation method based on the similarity between the drop pressure ratio and momentum ratio in Embodiment 1. The computer program can be in the form of source code, object code, executable file, or some intermediate form.
[0051] Example 4 This embodiment is based on embodiment 1: This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aircraft jet flow simulation method based on the similarity between drop pressure ratio and momentum ratio described in Embodiment 1. The computer program can be in the form of source code, object code, executable file, or some intermediate form. The storage medium includes any entity or device capable of carrying computer program code, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.
[0052] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
[0053] It should be noted that, for the sake of simplicity, the foregoing method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.
Claims
1. A method for simulating aircraft jet flow based on the similarity between drop pressure ratio and momentum ratio, characterized in that, include: Based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated, calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft. Based on the momentum ratio similarity and pressure ratio similarity criteria, the unit time momentum and total pressure of the simulated jet at the nozzle exit are calculated after similarity comparison. Based on the one-dimensional isentropic formula, the relationship between momentum and total pressure with respect to static pressure and Mach number at the nozzle exit is combined to solve for the static pressure and Mach number corresponding to the simulated jet. Combining the isentropic assumption and the principle of flow conservation within the nozzle, the area of the nozzle throat after similarity comparison is solved by using the area ratio between the nozzle outlet and the nozzle throat. Based on the size relationship of the nozzle throat before and after similarity comparison, a new nozzle throat is designed according to the original nozzle shape to obtain a nozzle shape that is suitable for simulated jet flow.
2. The aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 1, characterized in that, The calculation of the unit-time momentum and total pressure at the nozzle exit of the aircraft, based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated, includes: Based on the ideal gas law Formula for the speed of sound ,in For static pressure, For density, The gas constant is For static temperature, At the speed of light, The specific heat ratio of the gas is given; for any supersonic exit nozzle, the static pressure of the gas medium jet at the nozzle exit is known. ,Mach number Specific heat ratio of gases and nozzle exit area Calculate the momentum per unit time of the gas medium jet at the nozzle exit. : in, The density of the gas medium jet. The velocity of the gas medium jet; Based on the one-dimensional isentropic relationship, the total pressure of the gas medium jet at the nozzle outlet is calculated. : 。 3. The aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 2, characterized in that, The calculation of the unit-time momentum and total pressure at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated also includes: The static pressure of a real free flow is known. ,Mach number Specific heat ratio of gases Calculate the momentum per unit time of the actual free flow at the nozzle exit. : The static pressure of the free flow to be simulated is known. ,Mach number Specific heat ratio of gases Calculate the momentum of the free flow to be simulated at the nozzle exit per unit time. : 。 4. The aircraft jet simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 3, characterized in that, The calculation of the unit-time momentum and total pressure of the simulated jet at the nozzle exit, based on momentum ratio similarity and pressure ratio similarity criteria, includes: Let the momentum per unit time of the simulated jet at the nozzle exit after analogy be . Based on the similarity of momentum ratios, we have: Let the total pressure of the simulated jet at the nozzle exit be . Based on the similarity of the drop pressure ratio, we have: Therefore, the unit-time momentum and total pressure of the simulated jet at the nozzle exit after analogy are obtained as follows: 。 5. The aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 4, characterized in that, The method, based on the one-dimensional isentropic formula, combines the relationships between momentum and total pressure with respect to the static pressure and Mach number at the nozzle exit to solve for the static pressure and Mach number corresponding to the simulated jet, including: The specific heat ratio of the simulated jet is known to be... Let the Mach number of the simulated jet at the nozzle exit be . And the static pressure is According to the one-dimensional isentropic formula, we get: Solving the simultaneous equations yields a set of variables and The nonlinear equations are solved using numerical methods to obtain the static pressure and Mach number corresponding to the simulated jet.
6. The aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 5, characterized in that, The method, combining the isentropic assumption and the principle of flow conservation within the nozzle, utilizes the area ratio between the nozzle exit and the nozzle throat to solve for the nozzle throat area after similarity comparison, including: Known similarity comparison nozzle throat area And let the area of the nozzle throat after similar analogy be denoted as . For the nozzle throat after analogy, the nozzle throat area is obtained based on the one-dimensional isentropic formula and the fact that the flow rates of any two cross sections within the nozzle are equal. With nozzle exit area Relationship: For a supersonic exit nozzle, the Mach number of its nozzle throat is... Then, the nozzle throat area after similarity comparison is calculated. .
7. The aircraft jet flow simulation method based on the similarity of drop pressure ratio and momentum ratio as described in claim 6, characterized in that, The process involves designing a new nozzle throat based on the size relationship of the nozzle throat before and after analogy, according to the original nozzle shape, to obtain a nozzle shape adapted to the simulated jet flow, including: like In this case, the nozzle does not need to be redesigned, and the original nozzle can be used directly for simulation; like If the area of the nozzle throat after analogy is larger than that of the original nozzle throat, then a cross-section perpendicular to the jet exit direction is selected in the expansion section of the original nozzle, such that the area of this cross-section is equal to... ; like If the area of the nozzle throat after analogy is smaller than that of the original nozzle throat, then at one end of the throat of the original nozzle expansion section, the nozzle profile is smoothly extended in the opposite direction of jet ejection, and a cross-section perpendicular to the jet ejection direction is selected on the extended curved surface, such that the area of this cross-section is equal to... Thus, the shape of the nozzle expansion section after similar analogy is obtained.
8. A jet flow simulation system for aircraft based on the similarity between drop pressure ratio and momentum ratio, characterized in that, include: The momentum and total pressure calculation module is configured to calculate the momentum and total pressure per unit time at the nozzle exit of the aircraft based on the input parameters of the actual free flow, the gas medium jet, and the free flow to be simulated. The similarity module is configured to calculate the unit time momentum and total pressure of the simulated jet at the nozzle exit based on momentum ratio similarity and pressure ratio similarity criteria. The static pressure and Mach number calculation module is configured to solve for the static pressure and Mach number of the simulated jet by combining the momentum and total pressure with respect to the static pressure and Mach number at the nozzle exit using the one-dimensional isentropic formula. The nozzle throat area calculation module is configured to combine the isentropic assumption and the principle of flow conservation in the nozzle, and use the area ratio between the nozzle outlet and the nozzle throat to solve for the nozzle throat area after similarity comparison. The nozzle shape adjustment module is configured to design a new nozzle throat based on the size relationship of the nozzle throat before and after similar analogy, thereby obtaining a nozzle shape that is adapted to the simulated jet.