Benard convection
 

For the natural convection in a horizontal retangular chamber of aspect ratio 3:1, the chamber was 0.00275 maters in heigh.For the parameter of the fluid are Prandtl number Pr=7.396, Grashof number Gr=900,Reynolds number Re=30.The temperature difference between hot(bottom)and cold(top)walls of the container was 22K. In this case, how many vortexs would appear in the chamber? For the Rayleigh-Benard convection,what does the wavenumber mean? thanks.