Lattice Boltzmann simulation of flows in bifurcate channel at rotating inflow boundary conditions and resulted different outflow fluxes

摘要

The Lattice Boltzmann method(LBM) is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results,some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself,but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient,and changes the velocity profile.If the outlet contains more than one exit,the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.