H. Iacovides et al., THE COMPUTATION OF FLOW DEVELOPMENT THROUGH STATIONARY AND ROTATING U-DUCTS OF STRONG CURVATURE, International journal of heat and fluid flow, 17(1), 1996, pp. 22-33
This article presents comparisons between predictions, obtained during
the course of this investigation, and recently produced measurements
of the flow development through a square cross-sectioned U-bend of str
ong curvature, Rc/D = 0.65, that is either stationary or in orthogonal
rotation. For the stationary case, four turbulence models have been t
ested; a high-Re k-epsilon model interfaced with the low-Re 1-equation
model in the near-wall regions, a high-Re algebraic second-moment (AS
M) closure with the low-Re 1-equation model in the near-wall regions,
and two versions of a low-Re ASM model. The two low-Re ASM models retu
rn noticeably better predictions of the flow development. There is, ho
wever further scope for improvement, especially in the downstream sect
ion. Two rotating flow cases have been computed both with the axis of
rotation parallel to the axis of bend curvature; one at a positive rot
ation number R(0) = Omega D/W-b of 0.2 and one at R(0) = -0.2. In the
case of positive rotation, where the Coriolis and curvature forces rei
nforce each other, the flow predictions of the low-Re ASM are in very
close agreement with the data. When the section is not well reproduced
by the low-Re ASM model. More refined turbulence models are thus nece
ssary when the curvature and Coriolis forces oppose each other.