expertise in physical models


Transient laminar 2D Navier-Stokes flow at a higher Reynolds number of ~ 2000, which models a flute-like instrument. The inlet air flow at a velocity of 3 m/s is switched on at t = 0. After that, the boundary conditions remain unchanged. The flow impinges on a wedge, and although the flow remains pretty steady near the wedge tip, after 0.21 s suddenly the unsteadiness becomes visible through vortex shedding. When you look at the transient pressure field near the end (0.5 s) of the simulation, you can not only see the intense vortices, but also the periodicity further away from the wedge tip. This period or frequency would be the sound frequency that someone would hear who listens to the musician.




The Elder problem for buoyant ground water flow: part of an aquifer in 2D, where at time = 0 salt starts diffusing from the top into the fully saturated ground water. The water density is a function of the salt concentration c: dens = 1000*(1-C)+1200*C, so the salty water will move down and the salt-less water will move up. The flow is described by the Darcy- or porous flow equations. This benchmark case for porous flow shows the transient change (0-3 years) of the salt concentration, where the typical fingers are clearly visible.





Flow round cylinder at Re 100, a well known benchmark for CFD codes: transient laminar Navier-Stokes flow which shows vortex shedding behind a cylinder that is placed just below the center of a channel.