Modeling turbulent wall flows subjected to strong pressure variations

Mean pressure gradient affects the turbulence mainly through the modulation of the mean rate of strain. Modification of the turbulence structure feeds , in turn, back into rite mean flow. Particularly affected is the near wall region (including the viscous sublayer) where the pressure gradient invali dates the conventional boundary-layer "equilibrium" assumptions and inner-w all scaling. Accurate predictions of such flows require application of adva nced turbulence closures, preferably at the differential second-moment leve l,with integration Lip to the wall. This paper aims at demonstrating the po tential usefulness of such a model to engineers by revisiting some of the r ecent experimental and DNS results and by presenting a series of computatio ns relevant to low-speed external aerodynamics. Several attached and separa ted flows, subjected to strong adverse and favorable pressure gradient, as well as to periodic alternation of the pressure gradient sign, all computed with a low-Re-number second-moment closure, display good agreement with ex perimental and DNS data. It is argued that models of this kind (in full or a truncated form) may serve both Sol steady or transient Reynolds-Averaged Navier-Stokes (RANS, TRANS) computations of a variety of industrial and aer onautical flows, particularly if transition phenomena, wall friction, and h ear transfer are in focus.