problem about square duct.
 

dear all

the full development turbulence in square duct is simulated with LES, Re=4800, Ma=0.3. the period BC is set in streamwise. in order to balance the friction of the wall, the gradient of pressure P is given, so the wall friction tau_w is solved from the formula. problem is that: the velocity along streamwise is biger and biger? why? the aveage velocity of one certain grid point is evaluated in four turnoff time of votex, is the time too little? another thing puzzled me, my bulk velocity is not change biger as the time going. in web, the useful results of the compressilbe square duct is very very few, even search by google. thanks a lot. yours sincerely Bin Li