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In molecular kinetic theory in physics, a particle's distribution function is a function of seven variables, f(x,y,z,t;vₓ,vy,vz), which gives the number of particles per unit volume in single-particle phase space. It is the number of particles per unit volume having approximately the velocity 𝐯=(vₓ,vy,vz) near the position 𝐫=(x,y,z) and time t. The usual normalization of the distribution function is n(x,y,z,t)=∫f dvₓ dvy dvz, N(t)=∫n dx dy dz, where, N is the total number of particles, and n is the number density of particles – the number of particles per unit volume, or the density divided by the mass of individual particles.
Cross-scale discrete Boltzmann method suitable for calculating interference flow field of hypersonic shock wave boundary layer
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.
Owner:BEIJING INST OF TECH
A horizontal screw centrifuge separation performance prediction method
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.
Owner:SICHUAN UNIV