EXPERIMENTAL TESTING OF DIFFUSION-MODELS IN A MANIPULATED TURBULENT BOUNDARY-LAYER

An experimental investigation of the performances of one-point closure turbulent diffusion models is performed in an externally manipulated turbulent boundary layer, Detailed hot mire anemometry measurements ar e performed on a refined two-dimensional grid, allowing the terms of t he transport equations of the turbulent stresses to be calculated, The turbulent diffusion terms as well as the convection, production, and viscous diffusion terms are then directly estimated, The dissipation t erms of each Reynolds tenser component are estimated by use of local i sotropy hypothesis (epsilon(ij) = 2/3 epsilon delta(ij)), epsilon bein g obtained by balancing the turbulent kinetic energy budget. The press ure-strain terms are then obtained by balancing the <(u'(i)u'(j))over bar> equations. The results are presented for a streamwise position lo cated near the manipulator trailing edge (x = 2 delta(0)). All of the measurements are performed at relatively large distances from the wall (y(+) > 120), allowing the minimization of the spatial integration ef fects of the probes. The balances show the modifications imposed to th e classical turbulent boundary-layer equilibria, Knowledge of the diff erent terms allows several experimental applications of the convention al turbulent diffusion models to be made. One-equation, k-epsilon, alg ebraic stress, and second-order principal hypothesis or closure models are tested,It is shown that conventional models, developed for equili brium flows perform quite well in this configuration, Because of imbal ance between terms, however, one-equation and k-epsilon models cannot be successful in predicting this flow; the algebraic stress model can be used, but only if starting far enough from the manipulator, Higher order closures should be correct, as confirmed by other authors' calcu lations.