transition regime modelling..

sriram g s

hello.. can u plz help me with this..

while modelling flow in a confined channel(say flow inside a tube).. how am i suppossed to model the flow in transition zone.. around reynolds no. 3000, 3500 etc.. i tried using all the turbulent models.. but im not getting a satisfactory solution.. is there any thumbrule associated with creating the mesh..??

thanks