Turbulence in radial flow between parallel disks at medium and low Reynolds numbers

Abstract

The radial flow of air between two closely spaced parallel disks is studied experimentally and the behaviour of the flow, especially the turbulence decay mechanism, is examined. At high Reynolds numbers the flow resembles fully developed turbulent two-dimensional channel flow. A quasi-laminar boundary layer is found to gradually replace the viscous sublayer as the Reynolds number decreases. At low Reynolds numbers, the turbulence decays and the flow gradually approaches a laminar-type profile. The decay process is shown to be very slow and indications of a weak turbulence-generating mechanism is observed even at very low Reynolds numbers. Relaminarization, rather than being an abrupt change in the state of the flow, is an eventual outcome of the turbulence decay process.

Design optimization of a centrifugal compressor vaneless diffuser

“…The numerical model was also validated by comparing its results with the experimental results of Tabatabai and Pollard [28] and the numerical results of Colaciti et al [23]. A closer investigation of the experimental results of Tabatabai and Pollard [28] showed a high adverse pressure gradient due to the large diffuser radius.…”

“…Numerical simulation of the standard radial diffuser was performed using the CFD code Fluent. Numerical results were then validated using available experimental data of Tabatabai and Pollard [28]. Numerical simulations of the proposed variable area designs were performed after validating the numerical results of the standard radial vaneless diffuser.…”

“…To validate the numerical model, the numerically investigated radial vaneless diffuser in the present work is the one that was experimentally investigated by Tabatabai and Pollard [28] and numerically by Colaciti et al [23]. Figure 3 shows a schematic of the computational domain.…”

“…The diffuser has a radius at outlet of r 2 = 600 mm and a constant width of b = 10 mm. The shaped inlet and the inlet piece were sketched according to the recommendations of Moller [33] as stated by Tabatabai and Pollard [28]. The computational domain was extended a distance of 30 times the inlet pipe diameter (30D i ) upstream the diffuser to ensure fully developed turbulent flow at diffuser inlet piece, Figure 3.…”

Pressure distribution on the frontal disk for turbulent flows in a radial diffuser

“…Numerical solutions for incompressible laminar flows [1][2][3][4][5][6] and for incompressible turbulent flows [7,8] have been performed. Experimental work on this subject has been accomplished by Wark and Foss [9], Ferreira and Driessen [10], Tabatabai and Pollard [11], Ervin et al [12], Gasche et al [13], and Souto [14].…”