Symmetric and Asymmetric Turbulent Flows in a Rectangular Duct With a Pair of Ribs

Abstract

Laser-Doppler velocimetry (LDV) measurements are presented of mean velocity and turbulence intensity for turbulent flows past a pair of ribs in a rectangular duct of aspect ratio 2. The Reynolds number based on the duct hydraulic diameter was varied in the range of 2.0 × 103 to 7.6 × 104. The experiments cover ribs with rib height to duct height ratios from 0.13 to 0.33 and with rib width to height ratios from 1 to 10. The critical rib height above which and the critical Reynolds number below which the flow patterns become asymmetric were determined from the results. In addition, the effects of the rib width and boundary layer thickness on the formation and the size of the separation bubbles on the top surface of the ribs as well as on the reattachment length behind the ribs were documented. Furthermore, the degree of turbulence enhancement was compared between the asymmetric and the symmetric flows.

Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

“…However at every location in the channel, the 0 / Nu Nu values decrease as Re increases. Liou et al [21] and Liou et al [22] showed a similar trend. Note that due to the evolution of the Dittus-Boelter Nusselt number, increasing with Re number, Nu values increase with the Reynolds number.…”

Excited turbulent flow behind a square rib

“…Arnal and Friedrich (1991) from their large eddy simulation of backward facing step flow observed large departures of the instantaneous flow field from the mean flow field and concluded that for a complete understanding of the reattaching shear flow, the instantaneous flow structure is required. Nearly all the reported measurements (Antonia and Luxton, 1971;Tropea and Gackstatter, 1985;Liou and Kao, 1988;Durao et al, 1991;Myrum et al, 1993) that have presented Reynolds stresses and heat fluxes in ribbed ducts, have done so without carefully identifying the mechanisms associated with the production and transport of these fluxes. Yet this information is critical, not only in understanding the basic flow mechanisms, but also in developing suitable models for turbulent transport.…”

Prediction of turbulent flow structure in a fully developed rib-roughened narrow rectangular channel

“…Other numerous experimental studies of Antoniou and Bergeles [3], Durst and Rastogi [7] and Liou and Kao [10] investigated the flow behavior over surface-mounted two-dimensional ribs at different rib intensities with air as a working fluid. It was revealed that the reattachment length varies up to 16 times of the rib height depending on the rib shape, the degree of tunnel blockage and the flow regime namely, Reynolds number.…”