The Particle’s Coupled Lagrangian/Euler Algorithm Based On PDF Theory And Its Numerical Simulation

The solution of PDF equation has always been a challenging problem in the studying oftwo-phase flow theory, this paper proposes a new method which is called the particle’s coupledLagrangian/Euler algorithm. The whole algorithm consists four equations, which are turbulencek-ε standard equation, the two moments Euler equation of particles, the two moments Lagrangeequation of particles, and the coupled turbulent moment model of two-phase. The influence of theexistence particle flow field is mainly reflected in the gas phase on the equation of particle sourceterm, this paper mainly used the k-ε model and coupled turbulent moment model for gas phaseturbulence, using the SIMPLE method to solve the gas field of difference equations and calculatethe average speed of gas phase. This paper mainly used the particle’ two moments Euler equationsand the particle’ two moments Lagrange equations for particle phase, using the solution of gasphase equation to calculate the particle’ Lagrange equation, then using the Lagrange method tocalculate the particle phase two moments. we use new method to solve Euler equation and calculatethe velocity and concentration distribution of particles. Then we obtained particle velocity into thecoupling of two-phase turbulence equation, getting the new gas phase velocity, The new algorithmnot only closed the PDF equation, but also contained the superiority of Lagrange method and Eulermethod. The movement of the particle phase affect the air flow field, and the change of the gasphase flow also inevitably affects the moving track of particle phase, so the real movements of twophase flow field must be calculated by the gas phase flow equation and particle phase flow equationcoupling again and again.The backward-facing step two-phase flow is simulated by the particle’s coupledLagrangian/Euler algorithm, then the paper got the average speed of the two-phase flow simulation,pulse rate, the two tangent stress values compared with the experimental data and the value of othermethods. The results shows that the particle’s coupled Lagrangian/Euler algorithm can better reflectthe effect of gas phase, the result of particles numerical simulation are more close to reality, thenumerical characteristic curves of the particle phase is more smooth.