The heat transfer and fluid mechanics of a turbulent separating and reattaching flow past a single-sided backward-facing step are studied using large eddy simulation. A fully coupled, low Mach number preconditioned, collocated-grid, central differenced, compressible, finite volume formulation was developed to conduct the simulations. A sixth-order compact filter was used to prevent pressure-velocity decoupling. A compressible version of the dynamic subgrid scale model was used to model the effects of the smaller eddies. Navier-Stokes characteristic boundary conditions designed by Poinsot and Lele were used to provide boundary conditions. The isothermal turbulent flow past the step, at a Reynolds number of 5,540 (based on the step height and upstream centerline velocity) and a Mach number of 0.006, was simulated to validate the formulation. Subsequently, the bottom wall downstream of the step was supplied with constant wall heat flux levels of 1.0, 2.0, and 3.0 kW/m2. The viscous sub-layer played a critical role in controlling the heat transfer rate. Streamwise and wall-normal turbulent heat fluxes were of the same order of magnitude. The Reynolds analogy did not hold in the recirculation region. However, the Stanton number profiles showed a striking similarity with the fluctuating skin-friction profiles.

Der Band enthält den Abschlußbericht des DFG-Schwerpunktprogramms "Flußsimulation mit Höchstleistungsrechnern". Es führt die Arbeiten fort, die schon als Band 38 in der Reihe "Notes on Numerical Fluid Mechanics" erschienen sind.Work is reported, which was sponsored by the Deutsche Forschungsgemeinschaft from 1993 to 1995. Scientists from numerical mathematics, fluid mechanics, aerodynamics, and turbomachinery present their work on flow simulation with massively parallel systems, on the direct and large-eddy simulation of turbulence, and on mathematical foundations, general solution techniques and applications. Results are reported from benchmark computations of laminar flow around a cylinder, in which seventeen groups participated.

It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.

Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.