Regarding the two domains in the simulation of stirred tank
 

Hi,i am carrying on the simulation of stirred tanks, and in all the papers, the tanks were divided into two domains, a roational domain including the shaft and impeller and a stational domain including the baffles and tank walls, interfaces were used to connect them together. i wonder why cannot use only one domain and set the surface of the impeller and shaft as rotational wall and give a rotaional speed?

Thanks for everyone who help me.

Best Regards,Li