The migration of deformable drops in the channel flow neglecting the gravity influence is investigated numerically by solving the incompressible Navier-Stokes equations using the finite- difference method coupled with the front-tracking technique.The objectives of this study are to examine the effectiveness of the present approach for predicting the migration of drops in a shear flow and to investigate the behavior of the drop migration in the channel flow under zero-gravity.To validate the present calculation,some typical results are compared with available computational and theoretical data,which confirms that the present approach is reliable in predicting the drop migration. With respect to the drop migration in the channel flow at finite Reynolds numbers,the drops either move to an equilibrium lateral position or undergo an oscillatory motion under different conditions. The effects of some typical parameters,e.g.,the Reynolds number,the Weber number,the viscosity ratio and the density ratio of the drop fluid to the suspending medium,and the drop size,on the migration of drops are discussed and analyzed.
A new dynamic subgrid-scale (SGS) model, which is proved to satisfy the principle of asymptotic material frame indifference (AMFI) for rotating turbulence, is proposed based on physical and mathematical analysis. Comparison with direct numerical simulation (DNS) results verifies that the new SGS model is effective for large eddy simulation (LES) on rotating turbulent flow. The SGS model is then applied to the LES of the spanwise rotating turbulent channel flow to investigate the rotation effect on turbulence characteristics, budget terms in the transport equations of resolved Reynolds stresses, and flow structures near the wall regions of the rotating channel.
Direct Nmerical Simulation （DNS） of turbulent heat transfer in a wall-normal rotating channel flow has been carried out for the rotation number Nr from 0 to 0.1, the Reynolds number 194 based on the friction velocity of non ro taring case and the half-height of the channel, and the Prandtl number 1. The objective of this study is to reveal the effects of rotation on the characteristics of turbulent flow and heat transfer. Based on the present calculated results, two typical rotation regimes are identified. When 0 〈 Nr 〈 0.06, turbu lence and thermal statistics correlated with the spanwise veloc ity fluctuation are enhanced since the shear rate of spanwise mean flow induced by Coriolis force increases; however, the other statistics are suppressed. When Nr 〉 0.06, turbulence and thermal statistics are suppressed significantly because the Coriolis force effect plays as a dominated role in the rotating flow. Remarkable change of the direction of near wall streak structures based on the velocity and temperature fluctuations is identified.
A discontinuity-capturing scheme of finite element method(FEM)is proposed.The unstructured-grid technique combined with a new type of adaptive mesh approach is developed for both compressible and incompressible unsteady flows,which exhibits the capability of capturing the shock waves and/or thin shear layers accurately in an unsteady viscous flow at high Reynolds number. In particular,a new testing variable,i.e.,the disturbed kinetic energy E,is suggested and used in the adaptive mesh computation,which is universally applicable to the capturing of both shock waves and shear layers in the inviscid flow and viscous flow at high Reynolds number.Based on several calculated examples,this approach has been proved to be effective and efficient for the calculations of compressible and incompressible flows.
