Implicit Solution Of Three Dimensional Internal Turbulent Flows

Implicit Solution of Three-dimensional Internal Turbulent Flows

Implicit Solution of Three-Dimensional Internal Turbulent Flows

The scalar form of the approximate factorization method was used to develop a new code for the solution of three-dimensional internal laminar and turbulent compressible flows. The Navier-Stokes equations in their Reynolds-averaged form are iterated in time until a steady solution is reached. Evidence is given to the implicit and explicit artificial damping schemes that proved to be particularly efficient in speeding up convergence and enhancing the algorithm robustness. A conservative treatment of these terms at domain boundaries is proposed in order to avoid undesired mass and/or momentum artificial fluxes. Turbulence effects are accounted for by the zero-equation Baldwin-Lomax turbulence model and the q-omega two-equation model. For the first, an investigation on the model behavior in case of multiple boundaries is performed. The flow in a developing S-duct is then solved in the laminar regime at Reynolds number (Re) 790 and in the turbulent regime at Re=40,000 using the Baldwin-Lomax model . The Stanitz elbow is then solved using an inviscid version of the same code at M(sub inlet)=0.4. Grid dependence and convergence rate are investigated showing that for this solver the implicit damping scheme may play a critical role for convergence characteristics. The same flow at Re=2.5x10(exp 6) is solved with the Baldwin-Lomax and the q-omega models. Both approaches showed satisfactory agreement with experiments, although the q-omega model is slightly more accurate. Michelassi, V. and Liou, M.-S. and Povinelli, L. A. Glenn Research Center NASA-ORDER C-99066-G; RTOP 505-62-21...

Computation of Three-Dimensional Complex Flows

The IMACS-COST conference on "Computational Fluid Dynamics, Three-Dimensional Complex Flows" was held in Lausanne, Switzerland, September 13 - 15, 1995. The scien tific sponsors of the conference were • IMACS: International Association for Mathematics and Computers in Simulation, • COST: European Cooperation in the field of Scientific and Technical Research, • ERCOFTAC: European Research Community on Flow, Turbulence and Combus tion. The scientific interests of the IMACS and ERCOFTAC associations are closely related to computational fluid dynamics whereas the European Union programme COST covers a wider range of scientific subjects. The COST' Action F1' launched in 1992 by Professor I. L. Ryhming deals with "Complex three-dimensional viscous flows: prediction, modelling, manipulation and control". It has several subtopics among which numerical methods and modelling issues are the main areas of research and development. The meeting gathered together eighty-seven scientists, engineers and researchers from sev enteen countries: Belgium, Finland, France, Germany, Greece, Hong Kong, Israel, Italy, Japan, the Netherlands, Norway, Russia, Spain, Sweden, Switzerland, United Kingdom, United States of America. All major numerical approximation methods were discussed: finite differences, finite volumes, finite elements, spectral methods. The topics covered by the sixty communications spanned the full spectrum of computational fluid dynam ics: direct numerical simulation, large-eddy simulation, turbulence modelling, free surface flows, non Newtonian fluids, thermal convection, etc.