Lattice Boltzmann Simulation On Displacement Process Of Non-Newtonian Fluid/Newtonian Fluid

Non-Newtonian fluid widely exists in the fields of biological, chemical and petroleum engineering. With the wider range of its application, the study for fluid flow characteristics of non-Newtonian fluid has become an important subject. The lattice Boltzmann method as a new hydrodynamic calculation method also attracted the attention of scholars in the application of non-Newtonian fluid.Viscosity of Newtonian fluid can be characterized as a single coefficient, but for non-Newtonian fluid, the viscosity could be varied with the shear stress. The lattice Boltzmann method established for Newtonian fluid is not applicable to non-Newtonian fluid, so it needs to be perfected and supplemented.Based on the traditional LBM model, the LBM model for single phase non Newtonian fluid has been proposed on the basis of the constitutive equation. After the model validation, the flowing of power law and Bingham fluid in the rough channel has been investigated by proposed model, respectively. The flow field distribution and influence factor on the flow friction resistance coefficient in the rough channel have been discussed. As to Bingham plastic fluid, the distribution of yield region has been given. Based on Zheng two-phase flow model, the two-phase LBM model for non-Newtonian fluid has been proposed. It is validated by simulating power-law fluid displacing Newtonian droplet over obstacles. The good comparision with the results in literatures demonstrates its validity. On this basis, the two-phase displacement Newtonian fluid by non-Newtonian in the rough channel is simulated and the following conclusions have been obtained. The influence factors of displacement mainly include power-law index, surface tension, rough element spacing and relative roughness height. The smaller surface tension is, the rate of displacement faster is. When the surface tension is small, the displaced fluid would be separated from the rough wall, and flow fully into the middle of the channel. With the increase of the surface tension, the displacement velocity changes from the wave-like uplift into the wave-like decline. The decreasing of the power law index of displaced fluid could also accelerate the displacement rate, consequently greatly reducing the displacement time. At the same time, the displacing front end becomes flat with the reduction of the power law index. More, the increasing of relative roughness height and the decreasing of roughness element space could increase the flowing resistance, reduce the displacement rate and prolong the displacement time.