Study of the Transition to Turbulence Within a Curved Rectangular Channel With 40to 1 Aspect Ratio

摘要

Longitudinal turbulence intensity and streamwise mean velocity variations arestudied from measurements using single-sensor hot-wire probes at Dean numbers from 50 to about 450 in a curved rectangular channel with 40 to 1 aspect ratio, mild curvature, and an inner to outer radius ratio of 0.979. Measured results show significant increases in the longitudinal turbulence intensity as the Dean number increases above 150. These increases are first apparent near the concave surface in upwash regions between individual vortices which make up each vortex pair. Such increases correspond closely with twisting vortex motions, which is important in regard to transition from laminar to turbulent flow because these variations provide evidence that twisting results in the first important increases in turbulence energy at a given location as the Dean number increases.