TY - JOUR

T1 - Experimental study of the flow in helical circular pipes

T2 - Torsion effect on the flow velocity and turbulence

AU - Hayamizu, Yasutaka

AU - Yamamoto, Kyoji

AU - Yanase, Shinichiro

AU - Hyakutake, Toru

AU - Shinohara, Toru

AU - Morita, Shinichi

N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.

PY - 2008/9

Y1 - 2008/9

N2 - An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β 0, which is defined by β 0 = τ/(2δ)1/2 with non-dimensional torsion τ, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows: The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion (toroidal pipe) to a single vortex type after one of the twin-vortex gradually disappears as β 0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β 0, but changes its shape as β 0 increases, and attains the shape similar to that in a straight circular pipe when β 0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as β 0 increases for small β 0, and then increases after taking a minimum at β 0 ≈ 1.4 as β 0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at β 0 ≈ 1.4.

AB - An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β 0, which is defined by β 0 = τ/(2δ)1/2 with non-dimensional torsion τ, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows: The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion (toroidal pipe) to a single vortex type after one of the twin-vortex gradually disappears as β 0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β 0, but changes its shape as β 0 increases, and attains the shape similar to that in a straight circular pipe when β 0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as β 0 increases for small β 0, and then increases after taking a minimum at β 0 ≈ 1.4 as β 0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at β 0 ≈ 1.4.

KW - Critical reynolds number

KW - Helical circular pipe

KW - Torsion effect

KW - Turbulence

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U2 - 10.1007/s11630-008-0193-8

DO - 10.1007/s11630-008-0193-8

M3 - Article

AN - SCOPUS:54149086730

VL - 17

SP - 193

EP - 198

JO - Journal of Thermal Science

JF - Journal of Thermal Science

SN - 1003-2169

IS - 3

ER -