DEVELOPING AND PERIODICALLY DEVELOPED FLOW, TEMPERATURE AND HEAT-TRANSFER IN A RIBBED DUCT

Measurements of the flow field and thermal field are reported for a fl ow in a periodically ribbed duct al two Reynolds number, 3400 and 24 0 00. At the lower Reynolds number, the incoming flow is transitional, w hile at Re = 24 000, the incoming flow is fully turbulent. Thus, the r eported measurements highlight the differences in the development of t he surface heat transfer of a flow undergoing transition (Re = 3400) w ith that of a fully turbulent flow (Re = 24 000) in a ribbed duct. At Re = 3400, the heat transfer in the first interrib module, due to the transitional nature of the flow, is lower than the hear transfer in th e second interrib module. For the Fully turbulent flow, the heat trans fer profile in successive interrib modules decays to the periodic stat e. Associated velocity measurements confirm the transitional behavior al Re = 3400, with nearly a twofold increase in the normalized streamw ise velocity fluctuations past the first interrib module, where transi tion is completed. At Re = 24 000, no such dramatic increases of strea mwise turbulence levels is noted. The detailed set of measurements pro vides a complete picture of the transitional and fully turbulent flow and heat transfer in a ribbed duct. Copyright (C) 1996 Elsevier Scienc e Ltd.