Laterally converging flow. Part 1. Mean flow

Laterally converging flow occurs between two parallel surfaces with an exit hole formed in one. The present study examines the flow at a distance from the exit as a means of investigating an accelerating radial internal flow induced by the lateral convergence and satisfying the boundary-layer approximations. The measurements range from laminar to turbulent conditions, including the intermediate stage referred to by some investigators as laminarizing or laminarescent. The acceleration parameter K v = (ν/ V 2 ) dV / dr ranges from 2·6 × 10 −8 to 2·2 × 10 ×4 and the local Reynolds number varies from 210 to 6·8 × 10 4 for the data reported; the relation between the Reynolds number and the acceleration parameter was varied by adjusting the convergence angle or the plate spacing. For the main experiment the accelerating region is 86 plate spacings in length. Comparison with numerical predictions for laminar and turbulent flow leads to identification of flow regimes in terms of popular acceleration parameters K v , K p = (ν/ρ u 3 * ) dp / dr and K τ = (ν/ρ u 3 * ) (∂τ/∂ z ) w . Results demonstrate that a potentially turbulent entry flow subjected to accleration due to lateral convergence shows features common to laminarization in accelerating turbulent boundary layers in other geometries. Application of the function A + ( K p ) for a modified van Driest wall-region model is examined briefly for the intermediate regime.