Secondary Flow Phenomena in Rotating Radial Straight Pipes

K C Cheng,Liqiu Wang

doi:10.1155/s1023621x9500025x

K C Cheng, Liqiu Wang

Open Access

https://doi.org/10.1155/s1023621x9500025x

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Abstract

Flow visualization results for secondary flow phenomena near the exit of a rotating radial-axis straight pipe (length ࡁ = 82 cm, inside diameter d = 3.81 cm, ࡁ/d 21.52) are presented to study the stabilizing (relaminarization) and destabilizing (early transition from laminar to turbulent flow) effects of Coriolis forces for Reynolds numbers Re = 500 ∼ 4,500 and rotating speeds n = 0 ∼ 200 rpm. The flow visualization was realised by smoke injection method. The main features of the transition phenomena are disclosed for Re = 1,500 and 4,500. The observed secondary flow patterns are found to be quite different from those obtained by theoretical or numerical analysis with one pair of symmetric and steady counter-rotating vortices. The practical implications of the visualization study are pointed out.

Highlights

Flow visualization results for secondary flow phenomena near the exit of a rotating radial-axis straight pipe are presented to study the stabilizing and destabilizing effects of Coriolis forces for Reynolds numbers Re 500 4,500 and rotating speeds n 0 200 rpm
It is generally understood that secondary flow phenomena in curved pipes, heated or cooled horizontal pipes, and rotating radial straight pipes caused by centrifugal, buoyancy, and Coriolis forces, respectively, are somewhat analogous and are characterized by a pair of counter-rotating vortices across the cross-section normal to the main flow
The purpose of this paper is to present further flow visualization results as revealed by a smoke injection method for secondary flow phenomena depicting instability, transition to turbulence and relaminarization for Reynolds numbers Re 1500 and 4500 and rotating speeds n 25 200 rpm

Summary

Introduction

Flow visualization results for secondary flow phenomena near the exit of a rotating radial-axis straight pipe (length 82 cm, inside diameter d 3.81 cm, f/d 21.52) are presented to study the stabilizing (relaminarization) and destabilizing (early transition from laminar to turbulent flow) effects of Coriolis forces for Reynolds numbers Re 500 4,500 and rotating speeds n 0 200 rpm. Cheng and Wang [1993] presented flow visualization studies on the stabilizing and destabilizing effects of Coriolis forces in rotating radial straight pipes for Reynolds numbers Re 500, 2000, 3000 and 4000 and rotating speeds n 24 350 rpm. The purpose of this paper is to present further flow visualization results as revealed by a smoke injection method for secondary flow phenomena depicting instability, transition to turbulence and relaminarization for Reynolds numbers Re 1500 and 4500 and rotating speeds n 25 200 rpm. At present flow visualization results for secondary flow phenomena in rotating radial channels are rather limited and experimental results are mainly concerned with friction factor and heat transfer results

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