VELOCITY AND TURBULENCE INTENSITY DISTRIBUTIONS OF DEVELOPING TURBULENT PULSATING FLOWS IN SQUARE DUCT

Turbulent pulsating air flows in the entrance region of a square duct are investigated with a hot-wire anemometer system. The velocity wavef orms, the mean and turbulence components of the axial velocity, and th e entrance length are obtained as major characteristics of the develop ing turbulent pulsating flows. An inviscid flow theory coupled with th e quasi-steady wall shear stress assumption is presented to describe t he developing axial mean velocity profiles. A good agreement is seen b etween the measured and theoretically predicted values. The propagatio n of turbulence generated near the entrance of the square duct is sati sfactorily approximated by an empirical correlation of the propagation of turbulence proposed previously. The local turbulence intensity is found to be slightly weaker in the accelerating phase than in the dece lerating phase. The entrance length is about 60 times as large as the hydraulic diameter.