Fluid Shear Mechanical Property Analysis Based on Molecular Dynamic Simulation

Taking the wall force effect into consideration, a molecular dynamic model for two-paralleled walls-fluid system was built and the related shear process was simulated by changing the tangential motion of wall. Under different wall velocity conditions, the shear mechanical property of fluid level at different positions from wall was studied. And the effects of shear rate, pressure and temperature, on macro shear mechanical property were investigated. Results show that the random thermal motion of molecules can lead to the fluctuation of shear stress for different fluid levels, and with the increase of shear velocity, the fluctuation decreases. In the condition of large tangential velocity of wall, the large velocity slip between surficial fluid and the surface occurs, as responses to the step increase of shear force. Pressure and temperature have great effects on molecular distance, thus increasing pressure or decreasing temperature can decrease distance, as results in the rising for both viscosity and shear force.