Modeling flow regime transition using the LES turbulence model
 

Hi Everyone,

I'm trying to simulate flow through an aortic valve. The inlet and outlet boundary conditions are pressure inlet and outlet, respectively. At the outlet, the specified pressure waveform is static pressure and remains zero for the first 0.015sec, while the dynamic pressure at the inlet increases from zero to 500 Pa during this time interval. The orifice area of the valve remains constant during this time and is equal to 5 percent of the inlet cross-sectional area. Using the laminar flow regime assumption, I have no backflow at the outlet from the beginning time point, while using the LES turbulence model there is backflow from the beginning till t=0.014sec. In other words, it seems the flow requires a greater pressure gradient to pass the valve using this turbulence model.


I know in turbulent flow more energy is dissipated by eddies. However, during this time interval, the Reynolds number is always less than 800. So, the results should be similar to those obtained by laminar flow. Does this mean that LES cannot model the transition accurately and is not suitable for this simulation? It has been used in literature but was not validated.

Many thanks in advance!