An Improved Multiphase Lattice Boltzmann Method Scheme for Large Density Ratio Simulation in Heat Pipe

Abstract Heat pipe reactor is a cutting-edge energy power technology for future deep space and deep sea exploration, its current bottleneck is the development of high performance heat pipe, and the wick structure is the key factor affecting the performance of heat pipe. To promote research on flow and heat transfer mechanism inside heat pipe, an improved scheme of Multiphase LBM is introduced, which not only eliminates error caused by inconsistency of discretization scheme of pressure term when introducing non-ideal gas equation of state, but also the cubic term error of velocity field in the recovered Navier-Stokes equation through LBM. With this improved scheme introduced, results of better accuracy can be obtained, so as its application into permeability prediction of porous media. An ideal Kelvin structure is constructed according to the production process and geometric parameters. The lattice Boltzmann method was used to directly simulate the three-dimensional flow inside Kelvin structured metal foam on the pore scale, and the permeability are measured through numerical experiments based on Darcy’s Law. When solving the multiphase flow problems such as gas-liquid flow with multiphase Lattice Boltzmann method (LBM), the gradient of the macroscopic quantity is required to calculate the interaction forcing term between the neighboring fluid particles. It is found that unphysical numerical oscillations would occur in the vicinity of the phase interface. Through analysis and test, this numerical oscillation is found to be related to the discretization scheme of gradient operator between the phase interface, and will lead to numerical instability, which limits the simulation ability of LBM in dealing with the two-phase interface problem with high density ratio. Simulations of flat interface problem and liquid droplet system are made to confirm better performance of this optimized forcing scheme, and results of higher resolution of the flow field was obtained, which are in good agreement with analytical solutions and experimental results.