8 results about "Distribution function" patented technology

The invention relates to the technical field of fluid dynamics, in particular to a lattice-Boltzmann method-based thin particle flow two-way coupling modeling method, which comprises the following steps of: performing field domain discretization by selecting spatial resolution, performing collision migration and viscosity coefficient setting, establishing a time step sequence and a fluid initial speed, determining a speed disturbance parameter, and establishing a two-way coupling model; calculating particle volume fraction and density distribution to obtain a speed distribution function set. According to the method, the spatial resolution is selected for field domain discretization, so that flow field division is more refined, the motion resolution of particles in different regions is enhanced, and the numerical error of the particles in a local region is reduced. And through collision migration and viscosity coefficient setting, it is ensured that the particles are evenly stressed in different flowing states, and the stability of the particle motion trail is improved. A time step sequence and a fluid initial speed are established, so that the time advancing process of particle movement is kept consistent, and speed deviation caused by mismatching of time steps is reduced.

The invention discloses a cross-scale discrete Boltzmann method suitable for calculation of an interference flow field of a hypersonic shock wave boundary layer, and the method comprises the steps: building an evolution equation of a cross-scale discrete Boltzmann model based on a Boltzmann-BGK equation, the discrete speed selection of the discrete particle speed space meets the kinetic moment constraint determined based on Chapman-Enskog multi-scale analysis; based on the kinetic moment constraint and the fluid macroscopic physical quantity, a discrete equilibrium state distribution function is solved by adopting a matrix inversion method; obtaining an initial discrete distribution function based on a local equilibrium state hypothesis; performing numerical solution on the evolution equation based on the initial discrete distribution function and the equilibrium state distribution function to obtain an evolved distribution function; and calculating a high-order non-conservation momentum between the evolved distribution function and a discrete equilibrium state distribution function corresponding to the evolved distribution function to obtain a physical quantity for quantifying the thermodynamic unbalance characteristic of the flow field.

The invention relates to the technical field of computational fluid mechanics, in particular to a method for simulating the freezing process of a liquid drop impacting a cold surface. According to the specific technical scheme, migration calculation is conducted through an obtained distribution function; according to the mass distribution function and the energy distribution function, calculating a macroscopic physical quantity in the flow field, and calculating the pressure intensity and the pseudo potential energy of the fluid; the pseudo potential energy of the virtual fluid is calculated, and the interaction force between fluid particles and the interaction force between the fluid particles and the solid wall surface are calculated; calculating a real macroscopic velocity, an enthalpy value and a solid-phase volume fraction of the fluid, and a collision term, an acting force source phase and a heat source term of a distribution function; performing collision calculation on the mass distribution function and the energy distribution function, judging whether a convergence condition or a preset number of iterations is reached, and outputting a calculation result if the convergence condition or the preset number of iterations is reached; otherwise, continuing to execute the iteration process. According to the invention, a means can be provided for exploring freezing characteristics and mechanisms of impact of tiny liquid drops on a low-temperature surface, and a thought is provided for design and development of an anti-icing surface.

This invention relates to the field of centrifuge separation performance prediction technology, and proposes a method for predicting the separation performance of a horizontal screw centrifuge. The method involves establishing a single-phase fluid flow field model and flow field control equations; extracting flow field characteristic parameters; establishing a sedimentation separation criterion based on the preset condition that the parabolic trajectory of particles in the drum just falls on the drum wall, and calculating the particle settling velocity and settling threshold particle size; establishing a floating separation criterion based on the condition that particles are not carried out at the overflow port, and calculating the floating critical particle size; establishing a separation efficiency model based on the settling threshold particle size, floating critical particle size, and distribution function; and calculating the overall separation efficiency of the horizontal screw centrifuge based on the separation efficiency model. This invention establishes single-phase flow field models for centrifuges with different structural parameters and operating conditions, and uses thin-layer flow theory, sedimentation separation criteria, and floating separation criteria as theoretical foundations. The algorithm is simpler, the analysis results are more consistent with reality, and the theoretical basis is more sufficient.

The application discloses a kind of based on raindrop spectrum phase evolution transmission line icing thickness prediction method and system, belong to transmission line early warning technical field.Its method includes obtaining meteorological data in the area where transmission line is located and identifying warm layer and cold layer;Combining precipitation intensity and radar reflectivity, the relationship between particle number concentration and particle size is estimated, and the particle spectrum distribution function is obtained;Theoretical heat required for particle from ice state heating and melting is calculated, whether particle is completely melted is judged by energy conservation;Estimate the residence time and heat exchange of particle in cold layer, determine the phase state of particle when reaching ground;Combining particle spectrum distribution function and the phase state of particle when reaching ground, the collision efficiency between particle and transmission line and icing thickness growth rate are calculated;Transmission line icing thickness is obtained based on time accumulation.The application can carry out high-precision quantitative prediction on the thickness change of transmission line icing, and is especially suitable for fine power grid disaster prevention demand under the background of glaze weather.

The invention relates to the field of computational physics and particle simulation, and particularly provides an inverse transformation sampling energy spectrum incidence method. The method comprises the following steps: firstly, obtaining discrete energy spectrum data of beta decay based on theoretical calculation, constructing energy-probability density function mapping, and further generating a normalized cumulative distribution function; and then, performing inverse transformation operation on the uniformly distributed random numbers in the [0, 1] interval to generate energy distribution data conforming to the target energy spectrum. By taking beta decay of 63Ni as an example, whole-process modeling and simulation are realized through MATLAB and Geant4 platforms, results show that the method can effectively reconstruct a theoretical energy spectrum, is high in goodness of fit, has relatively high universality and accuracy, is applicable to most standard energy spectrums when being used for energy spectrum incidence simulation of beta decay type particles, has universality, and can be widely applied to the field of energy spectrum incidence simulation of beta decay type particles. The method can effectively process a complex spectrum pattern without closed expression, and is widely applied to researches such as radiation detection, nuclear reaction simulation, particle transport and high-energy physics.

The invention belongs to the related technical field of multi-scale particle transport solving, and discloses a multi-scale particle transport simulation kinematics solving method and system, and the method comprises the steps: selecting speed space discrete points based on a particle kinematics model in a discrete speed form; calculating a distribution function at the center of the grid along the discrete point direction of the speed space according to a compact format; accumulating the contribution values of the distribution function to the macroscopic physical quantity; scanning downstream grids in sequence based on a speed space discrete point direction; the speed space discrete points are replaced, the operation is repeated until the contribution values of the grid on all the speed space discrete points are accumulated, and the final macroscopic physical quantity is obtained; and outputting a macroscopic physical quantity calculation result when a convergence condition is met. The invention discloses a multi-scale particle transport simulation kinematics method and a multi-scale particle transport simulation kinematics system considering calculation memory, precision and efficiency. The method and the system are especially suitable for multi-scale particle transport simulation solution with large-speed spatial discrete points and relatively high heterogeneity and heterogeneity.

The invention discloses a raindrop spectrum phase evolution-based power transmission line icing thickness prediction method and system, and belongs to the technical field of power transmission line early warning. The method comprises the steps of obtaining meteorological data of an area where a power transmission line is located and identifying a warm layer and a cold layer; estimating the relationship between the particle number concentration and the particle size in combination with the rainfall intensity and the radar reflectivity to obtain a particle spectrum distribution function; calculating theoretical heat required for heating and melting the particles from the ice state, and judging whether the particles are completely melted or not through energy conservation; estimating residence time and heat exchange capacity of the particles in a cold layer, and determining a phase state when the particles reach the ground; the collision efficiency and the icing thickness growth rate between the particles and the power transmission line are calculated by combining the particle spectrum distribution function and the phase state when the particles reach the ground; and obtaining the icing thickness of the power transmission line based on time accumulation. According to the method, high-precision quantitative forecasting can be carried out on the icing thickness change of the power transmission line, and the method is particularly suitable for the refined power grid disaster prevention requirement under the glaze weather background.