Propulsion performance numerical calculation method, program and equipment for bionic undulating fin bionic undulating coupling pump spraying and storage medium

Abstract

The invention discloses a bionic fluctuation coupling pump jet propulsion performance numerical calculation method, program and equipment and a storage medium, and belongs to the technical field of underwater bionic robots. According to the method, a physical model is established according to bionics and fish taxonomy principles, the external flow field range and the boundary condition type of the bionic propeller are determined, a structured grid and non-structured grid combination technology is adopted, the calculation accuracy is improved, and a dynamic grid method is adopted for simulation calculation; the numerical calculation method provided by the invention is based on combination of various grids, can more accurately control the initial state of the propeller, improves the accuracy of a simulation result, obtains a fin surface pressure distribution rule of the undulating fin in one period and a flow field evolution rule along with the motion of the undulating fin, and obtains a blade surface pressure distribution rule of the pump-jet rotor in one period at the same time; the propelling performance of the bionic fluctuation coupling pump jet is effectively predicted, and a theoretical foundation is laid for structural design optimization and motion control of the bionic fluctuation coupling pump jet propeller.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater bionic robots, and in particular relates to a method, program, device and storage medium for numerically calculating the propulsion performance of a bionic undulating fin and a bionic undulating coupled pump jet. Background Art

[0002] Intelligent underwater robots (AUVs) are a key technology in the development of a new generation of marine equipment and have become a cutting-edge field of research that has garnered significant attention from governments, scientists, and businesses worldwide. Nature offers important insights into the development of high-performance underwater equipment. The bionic wave-fin underwater propulsion system, inspired by the efficient locomotion of fish, is a prime example. Currently, extensive research has been conducted both domestically and internationally on the appearance, structure, and performance of bionic propulsion systems. Compared to traditional underwater vehicles, bionic propulsion systems offer advantages such as high propulsion efficiency, enhanced stealth, compact size, and low cost. They demonstrate significant potential in resource exploration, environmental monitoring, underwater operations, and other areas.

[0003] Researching underwater vehicles that can both detect the ocean environment and possess efficient propulsion capabilities and strong environmental adaptability is of great practical significance for marine resource exploration and offshore surveillance. To address the poor environmental adaptability and instability of existing underwater vehicles, this paper combines a biomimetic propulsion mechanism with a traditional one to design a high-performance combined propulsion underwater vehicle. The underwater propulsion performance of a vehicle is closely related to its operating state, making research on its hydrodynamic performance crucial.

[0004] Hydrodynamic performance analysis is the theoretical basis for the structural design and motion control of bionic propulsion, and plays a vital role in improving the overall performance of propulsion. Traditional performance testing methods mainly include water tunnel and wind tunnel experiments, which have the disadvantages of high cost and long time consumption. In recent decades, computational fluid dynamics (CFD) technology has flourished. Using electronic computers as tools and applying various discrete mathematical methods, numerical experiments, computer simulations and analytical research on various problems in fluid mechanics are carried out to solve various practical problems, greatly saving manpower and material resources. In the field of bionic undulating fin research, many researchers have combined CFD technology to carry out research on the motion mechanism of undulating fins and the evolution law of flow field structures. However, no specific conclusions have been drawn on the specific influencing factors and change laws of the propulsion force of undulating fins. Existing research cannot provide guidance for the structural design and optimization of bionic undulating fin propulsion.

[0005] The combined propulsion system consists of two propulsion systems: a pump-jet propulsor and a flexible, undulating, long-fin bionic propulsor. The pump-jet propulsor primarily consists of a rotor system, a stator system, and a duct. The stator can be either a front-mounted stator or a rear-mounted stator. The front-mounted stator improves incoming flow conditions and provides a certain amount of pre-swirl for the rear rotor; the rear-mounted stator absorbs the wake of the front rotor to improve the pump-jet propulsor's efficiency. The pump-jet propulsor's duct also has accelerating and decelerating ducts. The decelerating duct reduces the inflow velocity in the internal flow field, allowing the rotor blades to operate in a relatively high-pressure environment, delaying cavitation and improving the propulsor's acoustic stealth. The accelerating duct accelerates the incoming flow, increasing the propulsor's thrust and improving the pump-jet propulsor's efficiency.

[0006] After millions of years of evolution, fish have developed two highly efficient swimming modes: BCF (Body and / or Caudal Fin propulsion) and MPF (Media and / or Paired Fin propulsion). Approximately 15% of fish species use MPF propulsion, primarily using their dorsal, pectoral, and pelvic fins. While MPF propulsion struggles to achieve high-speed cruising and rapid acceleration, it maintains good stability and propulsion efficiency at low speeds. Summary of the Invention

[0007] The present invention provides a method for numerically calculating the propulsion performance of a bionic wave-coupled pump-jet, comprising the following steps:

[0008] Step 1: Establish a simulation calculation physical model of the bionic wave fin and pump jet to be calculated;

[0009] Step 2: Determine the flow field range and boundary conditions outside the simulation calculation physical model;

[0010] Step 3: Establish structured grids and unstructured grids according to the external flow field range and boundary conditions, and initialize the wave fin motion and pump jet rotation to obtain the composite grid simulation calculation physical model and optimize it to determine the initial spatial positions of the wave fin and pump jet;

[0011] Step 4: Set simulation parameters and motion conditions for the optimized composite grid simulation calculation physical model;

[0012] Step 5: Calculate the bionic wave fin thrust based on the set simulation parameters and motion condition parameters: select the total calculation time, time step and number of calculation iterations, use the iterative method to calculate the bionic wave fin thrust, and obtain the final propulsion performance value of the bionic wave coupled pump-jet thrust.

[0013] Furthermore, the external flow field range and boundary conditions of the simulation calculation physical model determined in step 2 are specifically as follows: the external flow field range is determined to determine the flow field range around the undulating fin, and the size range of the flow field around the undulating fin and the pump jet; the boundary conditions are determined to set the front semicircular surface of the flow field as the velocity inlet condition, the rear end plane as the pressure outlet condition, and the surrounding square cylindrical surface as the wall condition.

[0014] Furthermore, the initial spatial position of the undulating fin is determined according to the fin surface motion equation, which is as follows:

[0015]

[0016] Take time t = 0s as the initial spatial position of the undulating fin:

[0017]

[0018] Among them, ρ and u are the three-dimensional space cylindrical coordinate parameters, θ max is the maximum swing angle, λ is the wavelength of the traveling wave, ω is the circular frequency, t is the time, is the initial phase angle.

[0019] Furthermore, the composite grid simulation calculation physical model is obtained and optimized in step 3 as follows: the grid simulation calculation physical model is divided into two calculation domains, the grid of the bionic wave fin model is encrypted, the grid type is a tetrahedral grid, and it is set as one calculation domain; the flow field of the pump-jet rotor, the grid type is a hexahedral grid, and it is set as another calculation domain; the two calculation domains are connected by a common node surface.

[0020] Furthermore, in step 4, simulation parameters and motion conditions are set for the optimized composite grid simulation calculation physical model, specifically: the optimized composite grid simulation calculation physical model is imported into the software, simulation parameters and motion conditions are set, and the stress tensor is solved using an unsteady and pressure-based turbulence solver.

[0021] Furthermore, the step 5 adopts an iterative method to calculate the thrust of the bionic undulating fin. Specifically, a separate solution algorithm is used for the thrust of the undulating fin. The flow field velocity is first solved under the initial value conditions, and the pressure correction is performed so that the solved physical quantity satisfies the conservation equation; then the turbulent kinetic energy scalar is numerically calculated. After the flow field physical quantity is solved, the thrust is calculated according to the solution value:

[0022] F T =T(t)-D(t)

[0023] Where T(t) and D(t) represent the propulsion and resistance effects caused by pressure and friction, respectively;

[0024] T(t) and D(t) are:

[0025]

[0026] Where p is the unit pressure, n1 is the surface normal vector, τ j1 is the viscous stress tensor component in the x direction, n j is the direction vector, and A is the total area of ​​the undulating fin.

[0027] Furthermore, the propulsion performance value of the final bionic wave-coupled pump-jet thrust obtained in step 5 is specifically as follows: the pump-jet thrust calculation is divided into three parts, namely rotor force, stator force, and duct force:

[0028] T P =T r +T s +T d

[0029] Where T P is the total pump-jet thrust, T r is the rotor force, T s is the stator force, T d catheter force;

[0030]

[0031] in: and are the pressure and shear force vectors on the surface, f and n respectively f is the specified direction vector, which indicates the direction in which the force is calculated;

[0032] Pressure vector on the surface The calculation is as follows:

[0033]

[0034] Among them, p f is the surface static pressure, a f is the surface mesh area vector, p ref is the reference pressure;

[0035] Shear force vector on the surface The calculation is as follows:

[0036]

[0037] Among them, T f is the stress tensor on the surface f, the shear force exerted on the surface by the fluid.

[0038] The present invention also provides a computer device / equipment / system, comprising a memory, a processor, and a computer program stored in the memory. When the processor executes the computer program, the steps of the method for numerically calculating the propulsion performance of a bionic undulating fin and a bionic undulating coupled pump-jet as described in any of the above items are implemented.

[0039] The present invention also provides a computer-readable storage medium having a computer program / instruction stored thereon, which, when executed by a processor, implements the steps of a method for numerically calculating the propulsion performance of a bionic undulating fin and a bionic undulating coupled pump-jet as described in any of the above items.

[0040] The present invention also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the method for numerically calculating the propulsion performance of a bionic undulating fin and a bionic undulating coupled pump-jet as described in any of the above items.

[0041] The beneficial effects of the present invention are:

[0042] The present invention proposes a numerical calculation method for the propulsion performance of a bionic wave-coupled pump-jet, which adopts a combination of structured grid and unstructured grid technology to improve the calculation accuracy, and adopts a dynamic grid method for simulation calculation; the numerical calculation method proposed in the present invention is based on the combination of multiple grids, can more accurately control the initial state of the propeller, improve the accuracy of the simulation results, obtain the pressure distribution law on the fin surface of the wave fin within a cycle, the evolution law of the flow field with the movement of the wave fin, and at the same time obtain the pressure distribution law on the blade surface of the pump-jet rotor within a cycle, effectively predicting the propulsion performance of the bionic wave-coupled pump-jet. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the numerical calculation method of the present invention.

[0044] Figure 2 It is a schematic diagram of the flow field around the undulating fin and pump jet of the present invention.

[0045] Figure 3 This is a schematic diagram of initialization of the undulating fin motion of the present invention.

[0046] Figure 4 This is a diagram of the wave fin and pump jet grid of the present invention.

[0047] Figure 5 This is a flow chart of thrust value calculation of the present invention.

[0048] Figure 6 The figure shows the distribution diagram of the undulating fin and pump jet pressure obtained by the numerical method of the present invention.

[0049] Figure 7 This is the vortex distribution diagram of the wave-combined pump jet field obtained using the numerical method of the present invention. DETAILED DESCRIPTION

[0050] The present invention is described in further detail below with reference to the accompanying drawings:

[0051] A method for numerically calculating the propulsion performance of a bionic wave-coupled pump-jet comprises the following steps:

[0052] Step 1: Establish a simulation calculation physical model of the bionic wave fin and pump jet to be calculated;

[0053] The simulation computational physical model includes the submersible body, left and right wave fins, and the tail pump jet. The submersible, as the main body, is simplified in the computational model as a streamlined rigid body with specific contours. The left and right wave fins are elongated strips, measuring 0.7m long and 0.2m wide, with zero thickness. They generate forward propulsion by simulating MPF undulations.

[0054] Step 2: Determine the flow field range and boundary conditions outside the simulation calculation physical model;

[0055] Specifically determine the external flow field area based on the overall size of the submersible and simulate the flow field environment around the physical model;

[0056] like Figure 2 As shown, determining the scope of the external flow field area refers to determining the scope of the flow field around the submersible, determining the size range of the flow field around the wave fins and the pump jet, the external flow field size is 5L*2L*L, L is the total length of the submersible, and L in the present invention is 1.5m; determining the flow field boundary conditions refers to the front end surface of the external flow field of the submersible being the velocity inlet condition, the rear end plane being the pressure outlet condition, and the four surfaces of the body being the symmetric plane conditions.

[0057] Step 3: Establish structured grids and unstructured grids according to the external flow field range and boundary conditions, and initialize the wave fin motion and pump jet rotation to obtain the composite grid simulation calculation physical model and optimize it to determine the initial spatial positions of the wave fin and pump jet;

[0058] like Figure 3 As shown in FIG, the initialization of the undulating fin motion means that since the fin is a periodic undulation, the initial shape of the fin at time t=0 will directly affect the propulsion performance of the submersible, so the initial position needs to be determined according to relevant theories.

[0059] Secondly, the initial spatial position of the fin surface is determined according to the fin surface motion equation, which is as follows:

[0060]

[0061] Taking time t = 0s, the initial spatial position of the undulating fin can be determined according to the equation;

[0062]

[0063] Among them, ρ and u are the three-dimensional space cylindrical coordinate parameters, θ max is the maximum swing angle, λ is the wavelength of the traveling wave, ω is the circular frequency, t is the time, is the initial phase angle.

[0064] Furthermore, the equations were written as user-defined functions (UDFs) in C language and the program was compiled in Fluent to control the fluctuation of the fins.

[0065] like Figure 4 , import the simulation calculation physical model obtained in step 3 into the software Meshing and ICEM respectively, and mesh the fin and pump jet respectively; in order to ensure the accuracy of the calculation results, the total number of meshes is not less than 5.5 million, and the simulation calculation physical model is divided into two domains. The mesh of the bionic wave fin model is encrypted, the mesh type is tetrahedral mesh, and it is set as one calculation domain; the flow field of the pump jet rotor, the mesh type is hexahedral mesh, and it is set as another calculation domain; the two calculation domains are connected by common node surfaces.

[0066] Step 4: Set simulation parameters and motion conditions for the optimized composite grid simulation calculation physical model;

[0067] The optimized composite grid simulation calculation physical model obtained in step 4 is imported into the software Fluent to set the relevant parameters for numerical solution, and the stress tensor is solved using the unsteady and pressure-based turbulence solver.

[0068] The turbulence solver uses the Reynolds time-averaged equations and the SST k-ω model k equation and ω equation in the two-party model under the vortex model:

[0069] The Reynolds time-averaged equation:

[0070]

[0071] Where ρ is the density of the fluid, u i is x i Speed ​​in direction, u j is x j The velocity in the direction, μ is the dynamic viscosity, t is the time, p is the pressure, is the Reynolds stress term;

[0072] The SST k-ω model k equation and ω equation in the two-party model under the vortex model are:

[0073]

[0074] Where k is the turbulent kinetic energy, ω is the specific dissipation rate, Γ k and Γω are the effective diffusion of k and ω respectively; Y k and Y ω are the dissipation of k and ω respectively, G ω represents the generation term of ω, G k represents the generation term of k, D ω is the cross diffusion term, S k and S ω For custom sources.

[0075] Step 5: Calculate the bionic wave fin thrust based on the simulation parameters and motion condition parameters set in step 4: select the total calculation time, time step and number of calculation iterations, use the iterative method to calculate the bionic wave fin thrust, and obtain the final propulsion performance value of the bionic wave coupled pump-jet thrust.

[0076] like Figure 5 As shown, based on the simulation parameters and motion condition parameters set in step 5, the total calculation time is selected as 5s, the calculation step is 0.001s, and the number of internal iterations is 20;

[0077] A separate solution algorithm is used for the undulating fin thrust. Under the initial conditions, the flow field velocity is first solved and the pressure correction is performed so that the solved physical quantities satisfy the conservation equations. Secondly, the turbulent kinetic energy scalar is numerically calculated. After the flow field physical quantities are solved, the thrust is calculated based on the solution value:

[0078] F T =T(t)-D(t)

[0079] Where T(t) and D(t) represent the propulsion and resistance effects caused by pressure and friction, respectively;

[0080] T(t) and D(t) are:

[0081]

[0082] Where p is the unit pressure, n1 is the surface normal vector, τ j1 is the viscous stress tensor component in the x direction, n j is the direction vector, and A is the total area of ​​the undulating fin.

[0083] Furthermore, the calculation of pump-jet thrust is divided into three parts: rotor force, stator force, and duct force:

[0084] T P =T r +T s +T d

[0085] Where T P is the total pump-jet thrust, T ris the rotor force, T s is the stator force, T d Catheter force.

[0086]

[0087] in: and are the pressure and shear force vectors on the surface, f and n respectively f A specified direction vector indicating the direction in which the force is calculated.

[0088] Pressure vector on the surface The calculation is as follows:

[0089]

[0090] Among them, p f is the surface static pressure, a f is the surface mesh area vector, p ref is the reference pressure.

[0091] Shear force vector on the surface The calculation is as follows:

[0092]

[0093] Among them, T f is the stress tensor on the surface f. This shear force is exerted on the surface by the fluid.

[0094] Step 6: Analyze the propulsion performance of the submersible;

[0095] like Figure 6 、 7 As shown in the figure, the propulsion performance refers to the thrust generated by the movement of the submersible; by changing the inlet velocity, the changing law of the submersible thrust is obtained; within a period T, the pressure cloud diagrams at four moments t = 0.25T, t = 0.5T, t = 0.75T, and t = 1T are selected for analysis; the vorticity cloud diagrams at four moments t = 0.25T, t = 0.5T, t = 0.75T, and t = 1T are selected for analysis.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A numerical calculation method for the propulsion performance of a bionic wave-coupled pump-jet, characterized by: The following steps are involved: Step 1: Establish a simulation calculation physical model of the bionic wave fin and pump jet to be calculated; Step 2: Determine the flow field range and boundary conditions outside the simulation calculation physical model; Step 3: Establish structured grids and unstructured grids according to the external flow field range and boundary conditions, and initialize the wave fin motion and pump jet rotation to obtain the composite grid simulation calculation physical model and optimize it to determine the initial spatial positions of the wave fin and pump jet; Step 4: Set simulation parameters and motion conditions for the optimized composite grid simulation calculation physical model; Step 5: Calculate the bionic wave fin thrust based on the set simulation parameters and motion condition parameters: select the total calculation time, time step and number of calculation iterations, use the iterative method to calculate the bionic wave fin thrust, and obtain the final propulsion performance value of the bionic wave coupled pump-jet thrust.

2. The method for numerically calculating propulsion performance of a bionic wave-coupled pump-jet according to claim 1 is characterized by: The external flow field range and boundary conditions of the simulation calculation physical model determined in step 2 are specifically as follows: the external flow field range is determined to determine the flow field range around the undulating fin, and the size range of the flow field around the undulating fin and the pump jet; the boundary conditions are determined to set the front semicircular surface of the flow field as the velocity inlet condition, the rear end plane as the pressure outlet condition, and the surrounding square cylindrical surface as the wall condition.

3. The method for numerically calculating propulsion performance of a bionic wave-coupled pump-jet according to claim 1 is characterized by: The initial spatial position of the undulating fin is determined according to the fin surface motion equation, which is as follows: Take time t = 0s as the initial spatial position of the undulating fin: Among them, ρ and u are the three-dimensional space cylindrical coordinate parameters, θ max is the maximum swing angle, λ is the wavelength of the traveling wave, ω is the circular frequency, t is the time, is the initial phase angle.

4. The method for numerically calculating propulsion performance of a bionic wave-coupled pump-jet according to claim 1 is characterized by: The composite grid simulation calculation physical model is obtained and optimized in step 3 as follows: the grid simulation calculation physical model is divided into two calculation domains, the grid of the bionic wave fin model is encrypted, the grid type is a tetrahedral grid, and it is set as one calculation domain; the flow field of the pump-jet rotor, the grid type is a hexahedral grid, and it is set as another calculation domain; the two calculation domains are connected by a common node surface.

5. The method for numerically calculating propulsion performance of a bionic undulating fin according to claim 1, characterized in that: In step 4, simulation parameters and motion conditions are set for the optimized composite grid simulation calculation physical model, specifically: the optimized composite grid simulation calculation physical model is imported into the software, simulation parameters and motion conditions are set, and the stress tensor is solved using an unsteady and pressure-based turbulence solver.

6. The method for numerically calculating propulsion performance of a bionic wave-coupled pump-jet according to claim 5 is characterized by: The step 5 uses an iterative method to calculate the thrust of the bionic undulating fin. Specifically, a separate solution algorithm is used for the thrust of the undulating fin. The flow field velocity is first solved under the initial value conditions, and the pressure correction is performed so that the solved physical quantity satisfies the conservation equation. Then, the turbulent kinetic energy scalar is numerically calculated. After the flow field physical quantity is solved, the thrust is calculated according to the solution value: F T =T(t)-D(t) Where T(t) and D(t) represent the propulsion and resistance effects caused by pressure and friction, respectively; T(t) and D(t) are: Where p is the unit pressure, n1 is the surface normal vector, τ j1 is the viscous stress tensor component in the x direction, n j is the direction vector, and A is the total area of ​​the undulating fin.

7. The method for numerically calculating propulsion performance of a bionic wave-coupled pump-jet according to claim 6 is characterized in that The propulsion performance value of the final bionic wave-coupled pump-jet thrust obtained in step 5 is specifically as follows: The pump-jet thrust calculation is divided into three parts, namely rotor force, stator force, and duct force: T P =T r +T s +T d Where T P is the total pump-jet thrust, T r is the rotor force, T s is the stator force, T d catheter force; in: and are the pressure and shear force vectors on the surface, f and n respectively f is the specified direction vector, which indicates the direction in which the force is calculated; Pressure vector on the surface The calculation is as follows: Among them, p f is the surface static pressure, a f is the surface mesh area vector, p ref is the reference pressure; Shear force vector on the surface The calculation is as follows: Among them, T f is the stress tensor on the surface f, the shear force exerted on the surface by the fluid.

8. A computer device / apparatus / system comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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