An experimental investigation of flow and diffusion in the disturbed boundary layer over a ridge—I. Mean flow and turbulence structure

摘要: Abstract The influence of a low ridge on the mean flow and turbulence structure boundary layer is investigated through experiments conducted in large meteorological wind tunnel. A two-dimensional triangular ridge, having slope 2 to 1 height (h) about 10 thickness, was placed normal air flow. Observations were made turbulent at various positions relative compared with measurements without ridge. biggest effect cause separation bubble or cavity region much reduced but recirculating very intense turbulence; this extends distance 13 h downstream from top maximum 2.5 h. In addition, there results an extended wake which velocity enhanced considerably distances (x) behind indicate that thickness increases roughly proportion ( (x ) , while perturbations velocity, Reynolds stress variances fluctuations decay as x −1 . Other observations flows square blocks gentle hills also show obstacle-caused although proportionality constants are found be strongly dependent obstacle shape. There no satisfactory theory present explain all these experimental results.