Large Eddy Simulation Of Turbulent Flow Of Power-law Fluid In Circular Pipe

As the "blood of industry",oil is an irreplaceable energy material.In petroleum engineering,most of the fluids involved are non-newtonian fluids,such as drilling fluids,completion fluids,asphalt,crude oil,polymer and so on.These fluids play a key role in the safety of oil production,the reduction of energy consumption and the improvement of oil recovery.Therefore,it is necessary to analyze the non-Newtonian fluid theory from the perspective of petroleum industry.In this paper,the dynamic subgrid-scale stress model is used to simulate the turbulent flow of power-law fluid in a circular pipe.First,the turbulent flow of higher Reynolds number is compared with the results of direct numerical simulation to verify the accuracy and applicability of the model and meshing selected in this paper.The effect of Reynolds number on the turbulent flow characteristics of Newtonian fluid is simulated by changing the inlet velocity.The research results show that the dimensionless mean axial velocity distribution conforms to the linear distribution in the viscous sublayer and the logarithmic distribution in the log-region.With the increase of Reynolds number,the values of the root mean square and Reynolds stress increase gradually,and the position of peak values move away from the wall.The instantaneous flow contour and velocity vector contour of different Reynolds numbers are also compared in the paper.It is concluded that with the increase of Reynolds number,the mixing ability of the fluid flow is strengthened,and the velocity distribution is more uniform.By changing the power-law index,the influence of different power-law indexes on the turbulent characteristics of power-law fluid is studied,and the influence of Reynolds number on the flow characteristics of shear-thinning fluid is studied.It is concluded that the influence of power-law index on the mean velocity distribution and dimensionless viscosity is mainly in the log-region.With the increase of power-law index,the mean velocity distribution decreases and the dimensionless viscosity decreases in the log-region.The predicted friction coefficient decreases with the decrease of power-law index.And the influence of power-law index on the second-order statistics of turbulence shows that with the increase of power-law index in logarithmic coordinates,the root mean square value and Reynolds stress increase gradually,and the position where the peak values move away from the wall.The effect of Reynolds number on the turbulent flow of shear-thinning fluid is that the mean velocity distribution of shear-thinning fluid gradually increases with the increase of Reynolds number.The simulated friction coefficient decreases with the increase of Reynolds number.In logarithmiccoordinates,with the increase of Reynolds number,the values of the root mean square of fluctuating velocity and Reynolds stress increase gradually,and the positions of peak values move towards the wall.Meanwhile,the instantaneous velocity contour and viscosity contour at the same position were also observed at the same time.It is clear that with the increase of Reynolds number,the low-velocity region near the wall gradually decreases.