Computation of incompressible viscous flows through artificial heart devices with moving boundaries

The extension of computational fluid dynamics techniques to artificial heart flow simulations is illustrated. Unsteady incompressible Navier-Stokes equations written in 3-D generalized curvilinear coordinates are solved iteratively at each physical time step until the incompressibility condition is satisfied. The solution method is based on the pseudo compressibility approach and uses an implicit upwind differencing scheme together with the Gauss-Seidel line relaxation method. The efficiency and robustness of the time accurate formulation of the algorithm are tested by computing the flow through model geometries. A channel flow with a moving indentation is computed and validated with experimental measurements and other numerical solutions. In order to handle the geometric complexity and the moving boundary problems, a zonal method and an overlapping grid embedding scheme are used, respectively. Steady state solutions for the flow through a tilting disk heart valve was compared against experimental measurements. Good agreement was obtained. The flow computation during the valve opening and closing is carried out to illustrate the moving boundary capability

Simulation of copper-water nanofluid in a microchannel in slip flow regime using the lattice Boltzmann method with heat flux boundary condition

Laminar forced convection heat transfer of water–Cu nanofluids in a microchannel is studied using the double population Thermal Lattice Boltzmann method (TLBM). The entering flow is at a lower temperature compared to the microchannel walls. The middle section of the microchannel is heated with a constant and uniform heat flux, simulated by means of the counter slip thermal energy boundary condition. Simulations are performed for nanoparticle volume fractions equal to 0.00%, 0.02% and 0.04% and slip coefficient equal to 0.001, 0.01 and 0.1. Reynolds number is equal to 1, 10 and 50.The model predictions are found to be in good agreement with earlier studies. Streamlines, isotherms, longitudinal variations of Nusselt number and slip velocity as well as velocity and temperature profiles for different cross sections are presented. The results indicate that LBM can be used to simulate forced convection for the nanofluid micro flows. They show that the microchannel performs better heat transfers at higher values of the Reynolds number. For all values of the Reynolds considered in this study, the average Nusselt number increases slightly as the solid volume fraction increases and the slip coefficient increases. The rate of this increase is more significant at higher values of the Reynolds number