37 results about "Compressible flow" patented technology

A valve arrangement (10) for reducing the instability of fluid flow in a compressible flow governor valve includes a cutoff plug (12) with a lateral concave surface (14) and an end portion (16) having a substantially circular cross section, and a seat (30) with a convex surface (32). The lateral concave surface (14) and the end portion (16) of the cutoff plug (12) define an abrupt cutoff corner (18). The radius (re) of the end portion (16) of the cutoff plug (12) is less than the radius (Rs) of the seat (30). The radius of curvature (R) of the seat (30) is less than the radius of curvature (rq) of the lateral concave surface (14) of the cutoff plug (12). The configuration of the cutoff plug (12) and seat (30) enhances the annular flow pattern beneath the cutoff plug (12) at all lift positions thus reducing flow instability.

The invention discloses a numerical simulation method for cavitation compressible flow shock wave dynamics and belongs to the field of numerical simulation of cavitation compressible flow and shock wave dynamics. A three-dimensional computing watershed based on three-dimensional geometric modeling software is established; a three-dimensional computing watershed mesh is divided based on mesh generation software; a cavitation compressible flow computational fluid dynamics model is established; an initial boundary condition is set to perform a three-dimensional computational domain flow field numerical computation; based on flow field post-processing software, the computational result is post-processed to obtain the unsteady evolution process of a multi-phase bubble structure. The numerical simulation method for cavitation compressible flow shock wave dynamics in the invention facilitates in-depth study of the cavitation physical mechanism, can be applied to the field of cavitation compressible flow and shock dynamics numerical simulation and solves related engineering problems. The cavitation compressible flow and shock dynamics numerical simulation engineering application area comprises hydraulic machinery, marine propellers, aviation turbo pump induction wheels, underwater supercavitation weapon applications.

The invention discloses a disturbance region updating method of steady compressible flow, and belongs to the technical field of computational fluid mechanics. The method includes steps of input file loading, flow field initialization, dynamic-computation-domain establishment, boundary virtual-grid updating, dynamic-computation-domain updating, residual estimation, time integration, judgment of whether convergence occurs and result output. The method is suitable for use in solving of any compressible flow on the basis of a time-propulsion method, can be combined with any spatial discrete formatand time-propulsion format and other existing time-propulsion acceleration technology, and is suitable for use in different initialization methods and complex and discontinuous wall surface conditions. The method can greatly improve calculation efficiency; for the subsonic-speed flow problem, the method can reasonably remove redundant far-field units in a later stage of solving near a steady state, and effectively narrow a computational domain; and for the supersonic-speed flow problem, the method can also reduce a storage requirement of a solving process.

The invention discloses a numerical simulation method for analyzing a wall surface function based on compressible flow. The method comprises the following steps: establishing a Navier-Stokes equationaccording to compressible flow characteristics, simplifying the Navier-Stokes equation, analyzing the Navier-Stokes equation to obtain a full turbulence zone speed equation, a viscous bottom layer speed equation, a full turbulence zone temperature equation and a viscous bottom layer temperature equation, and further defining a stress equation and a heat flow equation; giving an initial value of the temperature Tv of the viscous bottom layer, and calculating according to the Tv to obtain stress and heat flow; updating a stress item and a heat flow item by utilizing the calculated stress and heat flow; updating the values of a generation item and a dissipation item in the turbulence energy equation by calculating the average quantity of the turbulence energy generation item and the turbulence energy dissipation item; and finally, recalculating Tv by utilizing a viscous bottom layer temperature equation, and repeatedly updating in the next time step cycle. Based on the compressible flow characteristic, the method is particularly suitable for hypersonic flow, and the wall surface heat flow can be predicted more accurately.

The invention provides a whole-flow-field simulation method of the Hermite interpolation basic weighted non-oscillatory format. A finite-volume Robust HWENO format is constructed in the Cartesian coordinate, and through the cooperation with the immersed boundary method, a compressible flowing-around problem is calculated, the robustness of the Robust HWENO format is better than that of a HWENO format, and the Robust HWENO format is more easily popularized into a high-dimensional or movable and self-adaptive grid. Under a structural grid, when directly simulating the problem, the finite-volume Robust HWENO format requires a high-quality grid, however, generation of the high-quality grid is very complicated, and the immersed boundary method is a good method which can well process the boundary of an object surface and can be effectively used in various computational grids. Therefore, in the method, the finite-volume Robust HWENO format is effectively combined with the immersed boundary method, numerical simulation of the compressible flowing-around problem can be effectively conducted on a very simple Cartesian grid, and several numerical value simulation results of classical steady and unsteady problems fully verify the effectiveness of the method.

The invention discloses a method for measuring the circulation area of complex profile hole, main contents of which are that the air pressure P₁^* in front of the workpiece profile hole to be measured is adjusted to the supercritical pressure ratio, namely not less than 2 times of atmospheric pressure P_o in order to ensure that air passes through the profile hole at a critical speed, and the air after further expansion is discharged into the atmosphere through an exhaust pipe. Measuring the air pressure P₁^* in front of the profile hole, the air temperature T₁^* and the air flow Ga through a pipeline, calculating the coefficient m of the air through the air adiabatic index K and the gas constant R, and substituting these data into the flow equation of compressible flow to calculate the circulation area of the complex profile hole to be measured. Compared with the prior art method of measuring the area of the profile hole with the air power, the method disclosed by the invention, which measures the circulation area of the complex profile hole with the supercritical pressure ratio, has the advantages of the high measurement precision, the large measurement range, the strong commonality of a measuring device and the convenient operation, and solves the problem of precise measurement of the circulation area of the complex profile hole with the small circulation area.

The invention discloses a low-speed wind tunnel speed pressure measurement and control method based on a multi-parameter pressure regression algorithm, wherein the method comprises the steps: arranging two total pressure and total temperature measurement points at the middle part of a wind tunnel contraction section or a stable section, and respectively arranging a static pressure hole in the four walls of an outlet of the contraction section, and carrying out the static pressure measurement; acquiring the total pressure and the total static pressure difference in front of an inlet of a wind tunnel test section through a block multi-path average calculation mode and are subjected to multiple times of fitting with the standard total pressure and the total static pressure difference measured in the center of the wind tunnel test section through a least square method, and establishing a relational expression between the center pressure of the test section and the pressure of a wind tunnel flow field parameter pressure measurement point under different wind speeds; finally, obtaining a test center velocity pressure based on a compressible flow theory by adopting a multi-flow-field pressure parameter pressure regression algorithm, and performing drop coefficient correction by arranging a pitot tube at the center of a test section, wherein the test section center velocity pressure is directly taken as a control object in a wind tunnel test. The real velocity pressure of the model area can be reflected more truly under the large-model and large-angle conditions, and the measurement accuracy of the incoming flow velocity pressure of the model area is improved.

The invention provides a high-power centrifugal pump hydraulic performance prediction method based on weak compressible flow analysis. The method comprises the following steps that (1) a new sub-gridstress model is determined; (2) numerical calculation of a total flow field in a pump is carried out to obtain basic data of hydraulic performance prediction; and (3) the lift, the hydraulic efficiency and the net positive suction head are calculated according to the basic data of hydraulic performance prediction. According to the method, for the inner flow characteristic of a high-power highs-speed flow centrifugal pump and the defects of a dynamic sub-grid stress mode, the dynamic sub-grid mode with helicity constraints is constructed, the numerical simulation method of an in-pump weak compressible high-rotating-speed flow field is set up, and accurate numerical prediction of the hydraulic performance of the centrifugal pump is achieved.

The invention relates to a simulation method of pressure difference in low Reynolds number incompressible flow at bending boundaries. The method comprises the following steps of S1, enabling a calculation module to determine if the formula (1) is met or not for the given low Reynolds number incompressible flow, or R0<<x0, L>>R0, Re<1; S2, if the formula (1) in the step S1 is met, enabling the calculation module to generate or inherit particles in a simulation flow field, and adopting a multi-boundary tangential technology to process the fixed-wall boundary and generating virtual particles according to the requirement of the technology; S3, enabling the calculation module to calculate the volume force FA2 of each particle at the x point of any position according to the formula (2), and calculating the volume force FA1 at an inlet by the formula (3); S4, enabling an output module to output the volume force FA2 at the x point in the step S3. The method can conveniently convert the pressure difference in the low Reynolds number incompressible flow at the bending boundaries into the volume force at any part.

The invention discloses a method for determining the noise source position and the noise directivity of a high-parameter pressure-reducing valve, and the method is used to position a sound source of the high-parameter pressure-reducing valve under complex condition. The method comprises that hydrodynamics software is used to establish compressible flow value models of the high-parameter pressure-reducing valve; flow field distribution of the high-parameter pressure-reducing valve without an orifice plate and the high-parameter pressure-reducing valve with an orifice plate is solved via a basic control equation or a large eddy simulation turbulent flow model equation; the sound power level distribution maps in the symmetrical planes of the two models are obtained via calculation of the stable state flow field; noise source positions of the two models are obtained via stable state analysis; the noise directivity is determined by utilizing sound pressure monitoring points arranged in the downstream of an outlet of the high-parameter pressure-reducing valve; and noise directivity distribution maps of the two models are obtained. According to the invention, the noise source can be found accurately and effectively, and reliable basis is provided for noise reduction in a targeted manner.

The invention relates to a method for simulating a compressible flow field problem in a multi-resolution TWENO format, and provides a brand new finite difference multi-resolution trigonometric function weighted essentially non-oscillatory format, and is used for numerical simulation of a compressible flow field problem. Innovative points of the method are as follows: only information on a spatialcenter nesting hierarchical structure is used, and any equivalent multi-resolution is not introduced; the adopted linear weight does not need to be calculated through complicated numerical values to obtain a theoretically optimal solution, and the solution can be artificially set to be any positive number meeting the sum of 1. Compared with a classical WENO format, the method is simpler and more convenient, higher in robustness and easier to popularize to a high-dimensional space. Finally, the novel finite difference multi-resolution TWENO format effectively simulates a plurality of classicalhyperbolic conservation law equation problems in a numerical mode, and the effectiveness and reliability of the method are fully verified.

The invention discloses a parafoil fluid-solid coupling numerical simulation method based on a compressible flow immersion boundary method, which comprises the following steps of: establishing a space background grid and a parafoil flow field grid, embedding the parafoil grid into the space background grid, performing grid encryption near a parafoil position, and simulating the parafoil flow field grid. Determining the intersection condition of the parafoil grid and the space background grid through a geometric intersection method, generating a structural finite element grid of the parafoil, and establishing a corresponding relation with the parafoil flow field grid; a compressible Navier-Stokes equation on a space background grid is solved by using a finite volume method, in boundary condition processing, the parafoil adopts a non-slip wall surface boundary condition, and a one-dimensional semi-Riemann problem is calculated by using an FIVER method to obtain flux on a parafoil boundary; the flow field aerodynamic force obtained through calculation acts on the parafoil, structural deformation and motion of the parafoil are solved through a nonlinear structural dynamics finite element method, and the position of a parafoil grid is updated; important reference is provided for analysis and research of the working process of the parafoil.

The invention discloses a method for calculating the range and strength of an artificial airflow disturbance temperature inversion layer in a small scale. According to the invention, the flow of the artificial jet flow in the atmosphere is divided into compressible flow and incompressible flow; flow field transient equations of a compressible flow area and an incompressible flow area are calculated respectively; the range and the strength of the artificial jet disturbance inversion layer can be known; the method can accurately calculate the disturbance range and intensity of the thermal inversion layer under a small scale, can provide a set of overall solution for cloud and mist removal of airports, bridges and expressways and treatment of urban atmospheric pollution, and has the advantages of being low in cost, flexible to use, obvious in effect and the like compared with other treatment modes.

The invention discloses a method for performing numerical simulation on a compressible flow problem through high-order WENO format order reduction, which comprises the following steps of: S1, judgingwhether order reduction is required or not according to a criterion for a given WENO format with the highest precision when numerical flux of a certain position is calculated; s2, if order reduction is needed, judging whether order reduction is needed or not for the second-high-precision WENO format after order reduction according to the same criterion in the step S1; s3, circularly executing thestep S2 until the WENO format with the lowest order precision does not need to be reduced or reached; and then calculating the numerical flux of the position by adopting a WENO format with corresponding precision so as to further calculate the numerical simulation value of the position for the compressible flow problem containing the shock waves. The method can be used for the conservation type differential format, and the calculation amount is small due to the fact that the used format is determined in advance.

The invention discloses an integrated mathematical modeling method for a cavity noise generation and propagation law. The method comprises the following steps of step S1, establishing a key influenceparameter of a cavity noise problem and a characterization parameter system of the cavity noise problem; step S2, establishing and simplifying a cavity compressible flow control equation; step S3, establishing an integrated mathematical modeling equation for cavity noise generation and propagation; step S4, establishing cavity aeroacoustic boundary conditions to obtain cavity aeroacoustic wall surface conditions and a governing equations for cavity aeroacoustic far field conditions. The method has the advantages that the integrated mathematical modeling equation of the cavity noise generationand propagation law is established, the correctness of the established equation can be ensured fundamentally, and the method is beneficial for grasping the essence and key parameters of a cavity noisegeneration and propagation coupling problem, has positive guiding effects on experiments and numerical researches of cavity noise researches, improves the research efficiency of a cavity noise problem, and lays a theoretical foundation for comprehensive analysis of a cavity noise generation and propagation mechanism.

The invention provides a three-dimensional numerical simulation method for droplet atomization in a transonic flow process of compressible fluid, and relates to the field of fine atomization. According to the invention, simulation of a process from generation of a transonic flow field to breaking of liquid particles in the transonic flow field in a three-dimensional model space is realized by using a numerical simulation method; the established numerical model and calculation steps can be used for visualizing and analyzing three-dimensional states of a liquid crushing process, a crushing mechanism, particle position distribution, particle size distribution, particle speed distribution and the like in transonic flow fields in spray pipes with different shapes and based on a Laval mechanism.The established numerical model provides accurate prediction and most intuitive theoretical basis for crushing processes and results of different liquid particles in flowing under different airflow inlet and outlet boundary conditions under initial conditions.

The invention relates to the technical field of computational fluid mechanics, and provides an incompressible flow disturbance domain propulsion method, which comprises the following steps of: establishing an initial incompressible flow computational domain and an initial flow field based on an incoming flow speed; on the basis of the initial flow field, first-step iteration is carried out through an SIMPLE method, and an updated velocity flow field and an updated pressure flow field are obtained; secondly, the local grid residual calculated through iteration in the first step serves as numerical disturbance, and disturbance domain propelling is conducted through judgment of the positions of grid units and the distance between the grid units and the wall face of an object; and after the disturbance domain is propelled, next iterative loop is carried out, and a convergent solution is obtained. According to the method, by establishing the dynamic disturbance domain changing along with the convergence progress, invalid calculation in the single iteration process is reduced, waste of a large number of calculation resources is avoided, and the calculation efficiency of incompressible flow numerical simulation solving is improved.