Numerical study of juncture flows

Abstract

A computational study of laminar/turbulent and subsonic/supersonic horseshoe vortex systems generated by a cylindrical protuberance mounted on a flat plate is presented. Various vortex structures have been predicted and are discussed. For a low subsonic laminar flow, the number of computed vortex arrays increases with Reynolds number (with fixed incoming boundary-layer thickness), in agreement with experimental and previous numerical observations. The relationships among pressure extrema, vorticity, and the singular points in the flow structure on the plane of symmetry over the flat plate are studied. Mach number effects have also been investigated for laminar flow at one Reynolds number. The outermost singular point moves upstream when freestream Mach number increases. The size of the whole vortex structure increases dramatically due to shock-wave/boundary-layer interaction. The computed laminar horseshoe vortex systems start from a saddle point of attachment. In the case of a supersonic turbulent flow at a high Reynolds number, the computed results predict the same features as those indicated by the experimental results, such as the upstream shock-wave/ boundary-layer interaction and the classical horseshoe vortex system starting from a saddle point of separation. The calculations provide details of the downstream wake/shock-wave interaction and the near wake tornadolike vortex structure. The overall flow topology is discussed. Nomenclaturemeasured from the flat plate and cylinder E = extremum of p(x) H = height or semiheight of cylinder (clear from context) MOO = freestream Mach number N, N' = node and half-node, respectively p = pressure Re D = Reynolds number based on cylinder diameter S = saddle or separation (clear from context) S'-half-saddle u = velocity component in x direction x, y, z = Cartesian coordinates (origin is at center of cylinder) 6, = incoming boundary-layer thickness <5= cylinder-location boundary-layer thickness £, ry = vorticity components in x, y directions 9 = angle of separation or attachment IJL, IJL ( = molecular and turbulence eddy viscosity

Structure of a double-fin turbulent interaction at high speed

“…The two values so obtained at each point are then blended with an appropriate function depending inversely on the distance to each surface. 8 The condition of symmetry is invoked on the central plane and, thus, only one-half the domain of the experiment is calculated. For the configuration examined by Kussoy and Horstman, 15 the fins end abruptly.…”

“…7) and 2) the inverse blending (IB) method. 8 Both procedures are employed in this work to assess the sensitivity of the computed flow to variations in eddy viscosity values.…”