30 results about "Euler equations" patented technology

The invention discloses a four-rotor aircraft control method based on PID neural network (PIDNN) control. First, dynamic equations of a four-rotor aircraft are established based on the Newton-Euler equations, and then, a nested controller is proposed. An inner loop decentralized controller is designed based on a PIDNN method to realize attitude control, and the outer loop adopts a classical PID control method. Next, online learning of a PIDNN controller is realized by an error back propagation method, the connection initial weight of PIDNN is determined based on the principle of PID control, and an appropriate learning step is selected according to the discrete Lyapunov theory to guarantee the convergence of the controller. Thus, the control problem of a four-rotor aircraft caused by high degree of nonlinearity, strong coupling and under-actuating capability, disturbance from the external environment in the process of flight and other factors can be effectively solved.

The invention provides an improved high-order nonlinear spatial discretization method for solving an Euler equation, and the method comprises the following steps: 1, reading initial flow field data, and calculating the positive and negative fluxes of each node at the moment of the Euler equation; 2, performing feature projection on the positive flux and the negative flux on each node to obtain a feature flux, and calculating an intermittent detection factor according to the feature flux on each node; 3, constructing a high-order hybrid calculation method of numerical flux on a half point according to the intermittent detection factor, and completing spatial discretization of the Euler equation; 4, discretizing the time items by adopting a three-order Runge-Kutta method; and 5, pushing thetime to a specified tN to finish calculation to obtain flow field data at the tN moment. According to the improved high-order nonlinear spatial discretization method, the WENN-LC format has higher flow structure resolution than a traditional NND format under the same grid; in addition, the hyWENN-LC mixed format not only has higher resolution, but also has higher calculation efficiency.

The invention discloses a rigid body control method for fluid guide based on deep reinforcement learning. In the method, the behavior of a fluid-rigid body simulator is changed by applying a control force only at the boundary of a simulated region, and the fluid is controlled by a Navier-Stokes equation and the rigid body is controlled by a Newton-Euler equation in the simulated region. The controller of the method is a neural network trained by deep reinforcement learning, and through pre-training, a control action can be generated in an online mode. The controller based on the method receives states of the fluid and the rigid body as input, a fluid nozzle is controlled to move at the boundary and injects fluid towards the rigid body in the simulated region, and thus, physical realistic simulation results can be generated, and good effects are obtained in multiple two-dimensional fluid-rigid control tasks. The method can also expanded to a three-dimensional fluid-rigid coupling system, for example, the rigid body can be controlled to accurately move to a specified three-dimensional target point.

The invention relates to a flight dynamics modeling and analysis method for a wingtip hinge combined type flight platform, and belongs to the technical field of aircraft flight mechanics modeling andsimulation analysis. According to the method disclosed in the invention, the sub-aircrafts in the wingtip hinged combined type flying platform are treated as rigid bodies; the degree of freedom of motion is expressed in the form of absolute coordinates relative to an inertial coordinate system, a multi-body dynamics theoretical analysis method is introduced, a constraint equation is established incombination with a Lagrange multiplier method to express an articulation relationship, and a Newton-Euler equation is utilized to establish a flight mechanical equation of the flight platform. The invention provides a method and process for analyzing the flight mechanical characteristics of the wingtip hinge combined type flight platform. Aircraft trimming and flight mechanical stability analysiscan be carried out.

The invention discloses a method and a system for estimating disturbance torque caused by an asymmetric rotational scanning load. The method comprises the following steps of: calculating according to coordinate conversion to obtain a rotational inertia matrix of a rotating body formed by a load cabin and a magnetic suspension joint rotor in an orbital coordinate system; calculating to obtain the angular velocity vector of the rotating body in the inertial coordinate system; calculating the angular momentum of the load cabin according to the rotational inertia matrix and the angular velocity vector of the rotating body; establishing the attitude dynamic model of the rotating body according to an Euler equation; classifying nominal rotating speeds in the attitude dynamical model to obtain a variable inertia reaction torque and gyroscopic torque interference model caused by an orbital angular velocity and a rotating body angular velocity; and substituting the rotational inertia of the rotating body in the satellite and the nominal rotating speed of the rotating body into the interference model, and estimating constant value, first frequency multiplication and second frequency multiplication interference torques caused by the rotating body. According to the invention, a basis for applying interference is provided for control, ground simulation and test verification of the magnetic suspension rotary joint and the satellite.

The invention discloses a method for predicting a full characteristic curve of a centrifugal pump, which comprises the following steps of: establishing a mathematical model for representing a water head full characteristic relation and a torque full characteristic relation of the centrifugal pump according to a similar law on the basis of an Euler equation during stable operation of the centrifugal pump and a flow velocity triangle of water flow at an impeller; centrifugal pump full characteristic curve data of various specific speeds are collected, a centrifugal pump full characteristic curve is transformed, and characteristic parameter values corresponding to characteristic working condition points on the transformed curve are extracted; establishing a relation function between the characteristic parameters of each characteristic working condition point and the specific speed of the centrifugal pump by adopting a nonlinear regression model; and substituting the relation function into a mathematical model for describing the full characteristics of the centrifugal pump, solving an undetermined coefficient in the model, and predicting a full characteristic curve of the centrifugal pump at any specific speed through inverse transformation. The method is high in theoretical property and simple in procedure, the problem that the centrifugal pump full characteristic curve cannot be obtained through linear interpolation in some projects is effectively solved, manpower and material resources are saved, and the project design process is accelerated.

The invention is applicable to the field of computational fluid mechanics, and provides a compressible fluid numerical simulation method which comprises the following steps: S10: reading physical variable distribution, boundary conditions and test duration of computational grids and moments; s20, on the computational grid, obtaining a conservation variable and a convection flux according to the physical variables of the moments; s30: respectively calculating the convection flux, the numerical flux in the physical space, and the numerical flux in the physical space; s40, substituting the conservation variable and the numerical flux into a discrete Euler equation to obtain a conservation variable at the n + 1 moment and a corresponding physical variable; and S50, n is traversed from 1-k, k is the serial number of the test duration at the moment, and the conservation variable and the physical variable at the moment serve as the final test result. By means of the method, the calculation efficiency is improved, the essential oscillation-free characteristic during numerical calculation is guaranteed, and stable calculation is achieved.

The invention discloses a telemetering automatic meteorological station system and a meteorological prediction method thereof, after a meteorological simulation model is constructed, meteorological data is acquired through a meteorological station for meteorological prediction, and the method comprises the following steps: establishing a compressible Euler equation, performing hydrostatic pressure approximation on the pressure p, endowing time information to a meteorological prediction data result y, giving y time integral to the meteorological prediction data result, constructing a time integral model based on an Euler equation, and forecasting and solving the weather data within the time interval delta t; according to the telemetering automatic meteorological station system and the meteorological forecasting method, the meteorological forecasting result with time information can be provided, the meteorological forecasting accuracy is improved, the data maintenance is good, the observation cost is reduced, and good man-machine interaction can be realized.

The invention provides a one-dimensional calculation method considering centrifugal fan impeller working capacity during natural prewhirl, which comprises the following steps of: considering the influence of inlet natural prewhirl in an actual centrifugal fan on the impeller working capacity, and applying a method for processing centrifugal impeller outlet airflow slippage by Stodola to an impeller inlet; by correcting a simplified cycle speed coefficient phi < 2 > u of an Euler equation in an original one-dimensional calculation method, a corrected cycle speed coefficient phi '< 2 > u considering the natural prewhirl influence is proposed; and directly correlating the corrected cycle speed coefficient phi '2u with the inlet and outlet diameters of the centrifugal impeller, the inlet and outlet blade mounting angles, the number of impeller blades, the fan rotating speed and the flow parameters, and deriving and proposing a novel one-dimensional calculation method considering the actingcapacity of the centrifugal fan impeller when the inlet is naturally pre-rotated. According to the novel calculation method, the accuracy and reliability of one-dimensional scheme design of the centrifugal fan are remarkably improved; the workload of fan test correction in the product development process is reduced, the degree of dependence of centrifugal fan one-dimensional scheme design on design experience of research and development personnel is reduced, and the method has the advantages of being simple in mathematical formula, clear in physical significance, easy to apply to engineeringdesign and the like.

The invention discloses an analytic Riemannian solution method aiming at a multi-dimensional Euler equation, which is characterized in that a multi-dimensional problem is converted into a one-dimensional shock tube problem based on a flowing physical law, a multi-dimensional velocity component is decomposed into a wave system-generating motion and a wave system-following motion, and a one-dimensional analytic Riemannian solution is applied in a normal direction based on velocity decomposition, the tangential velocity is kept unchanged through a wave system, so that the analysis Riemannian solution method is popularized to multi-dimensional flux calculation by utilizing the physical law, and the analysis Riemannian solution numerical solution of the multi-dimensional Euler equation is achieved. Compared with a general vector flux splitting method, the Riemann resolving method for analyzing the multi-dimensional Euler equation is small in format dissipation, and for viscous boundary layer calculation, a good result can be obtained by adopting a small number of grids or sparse grid distribution.

The invention discloses a method for processing a large airfoil attach angle solid wall boundary based on a Riemannian problem. For a large two-dimensional airfoil attach angle problem with a control equation as a Euler equation, the Riemannian problem is raised up in the normal direction of a sliding solid wall, the Riemannian problem is solved based on a shock wave or rarefaction wave relation, then, the value of the solid wall boundary is acquired, and a solid wall boundary condition is given; the method fully utilizes assurance of the solution of the Riemannian problem, the problem that usually negative pressure is easily generated to the solid wall boundary condition is solved, and the method is also used for small attach angle situations and has general applicability. The method has the advantages that the method for processing the large airfoil attach angle solid wall boundary solves the problem that negative pressure is easily generated in the two-dimensional airfoil flow field calculation process under a large attach angle, can be used for ordinary flow field calculation solid wall processing, and has good generality.

The invention discloses a closed non-circular gear pitch curve design method capable of realizing quick start and sudden stop, which comprises the following steps: designing a pitch curve of a non-circular gear pair in a working stage (2) according to a given non-uniform speed ratio transmission relationship serving as a design basis; establishing pitch curve mathematical models of a non-circular gear pair starting stage (1) and a sudden stop stage (3) according to differential and kinematics according to non-uniform transmission design requirements of quick starting and sudden stop; and finally, according to a variational method and an Euler equation of a fixed boundary condition, solving the pitch curve of the non-circular gear pair in a starting stage and a sudden stop stage, and realizing the design of the closed non-circular gear pair pitch curve with quick starting and sudden stop characteristics. According to the invention, the closed design is more free and flexible, the closed non-circular gear pair pitch curve meeting any given non-uniform speed ratio transmission design requirement can be designed by modifying the boundary conditions of the pitch curve in the working stage, it is ensured that the non-circular gear pair has the characteristics of quick start and sudden stop, and the transmission efficiency of the non-circular gear pair can be improved.

The invention belongs to the field of computational fluid mechanics numerical solution, and relates to an intermittent Galerkin finite element numerical solution method of an Euler equation, which isbased on orthogonal decomposition model order reduction. According to the invention, the discontinuous Galerkin finite element (DG) method and the orthogonal decomposition (POD) method are combined; solving variables are approximated by constructing a POD base so as to reduce the model dimension; the POD model is used for order reduction to perform low-dimensional approximate description on a multi-dimensional physical process, and the model dimension is reduced, so that in the calculation process of the DG algorithm, the degree of freedom of the calculation model is reduced while the acceptable precision is maintained, the calculation cost is reduced, and the time and memory consumption is reduced. Finally, the advantages of the finite element and the finite volume are kept, and the defects of the finite element and the finite volume are overcome.

The invention provides a method for analyzing shallow water shaking upsetting moment in a ship reception chamber of a winch type ship lift, and belongs to the technical field of data statistics. The method includes the following steps: collecting parameters of a ship reception chamber of the winch type vertical ship lift and a water area in the chamber, and establishing a longitudinal two-dimensional mechanical analysis model of the ship reception chamber; assuming that a water body in the ship reception chamber is an ideal fluid which is incompressible, free of rotation and small in free liquid level displacement, and establishing a Laplace equation and boundary conditions which meet working conditions according to the influence of trim motion on the ship reception chamber in the normal operation process; solving an absolute speed potential by using a multi-mode theory and combining a variable separation method; solving hydrodynamic pressure according to an Euler equation; solving the unit width upsetting moment acting on the center of the ship reception chamber bottom plate through integration; calculating and analyzing the convergence of the upsetting moment, and carrying out engineering simplification on the premise that the calculation precision is guaranteed; and finally carrying out programmed solution. The reliability and feasibility of the longitudinal anti-overturning treatment scheme design of the ship reception chamber of the winch type ship lift can be improved.

The invention relates to an ultrasonic numerical simulation method for disruptive discharge of a GIS (Gas Insulated Switchgear) under the condition of considering the influence of background fluid. The method comprises the following steps of: 1, establishing a corresponding numerical physical model according to an existing GIS physical model; 2, carrying out electric-magnetic-thermal-flow multi-physics field coupling simulation calculation, and obtaining a temperature distribution result, a pressure distribution result and a flow velocity distribution result of SF6 gas in the GIS in a steady state; 3, mapping temperature, pressure and flow velocity distribution results under the CFD calculation grid to a sound field grid through a weak-form partial differential equation; 4, according to the function that the density of the SF6 gas changes along with the temperature and the pressure during parameter setting, finally obtaining a linear Euler equation that the density, the pressure and the flow velocity of the SF6 gas change along with the space; and 5, obtaining a sound pressure instantaneous distribution result under the influence of the background fluid. Compared with the prior art, the method has the advantages that the precision of disruptive discharge ultrasonic simulation in the GIS is improved, and the like.

The invention provides a centrifugal compressor working capacity one-dimensional algorithm based on impeller inlet natural prewhirl, which comprises the following steps: 1) considering the influence of inlet natural prewhirl in an actual centrifugal compressor on the impeller working capacity, and applying a method for processing impeller outlet airflow slippage by Stodola to an impeller inlet; 2)correcting a simplified cycle speed coefficient of an Euler equation in the original one-dimensional calculation method of the impeller working capacity, and providing a corrected cycle speed coefficient; (3) directly associating the corrected cycle speed coefficient with the impeller inlet and outlet diameter, the impeller inlet and outlet blade installation angle, the number of impeller blades,the impeller rotating speed and the compressor flow parameters, and deducing and providing a novel one-dimensional calculation method considering the centrifugal compressor impeller acting capacity during impeller inlet natural prewhirl. According to the novel calculation method, the accuracy and reliability of one-dimensional scheme design of the centrifugal compressor are remarkably improved; the workload of model-level test correction in the product development process is reduced, the degree of dependence of centrifugal compressor scheme design on design experience of research and development personnel is reduced, and the method has the advantages of being simple in mathematical formula, clear in physical significance, easy to apply in engineering design and the like.

The invention discloses a high-precision numerical simulation method based on accurate solution of a Riemannian problem, and belongs to the field of multi-substance interaction high-precision numerical simulation. According to the method, a multi-substance random state equation Riemannian problem accurate solving method and a virtual fluid method (GFM) are combined, a real virtual fluid method (RGFM) and a wall surface virtual fluid method (WGFM) are included. Meanwhile, a weighted essential no-oscillation (WENO) finite difference method and a level set method (Level-Set) are coupled to form a high-precision numerical simulation method. According to the invention, the dissipation of shock waves and sparse waves in the propagation process can be reduced; a non-physical oscillation phenomenon generated at an interface when an Euler equation is solved can be effectively inhibited, and stable operation of a numerical value prediction process is guaranteed; by means of the method, the Riemannian problem of any state equation can be accurately solved, the accurate interface state of multi-substance interaction is obtained, the precision of the numerical calculation result of the multi-substance interaction process is improved, the prediction precision of the multi-substance interaction process is improved, and then the engineering technical problem related to the field of multi-substance interaction is solved.