Direct Numerical Simulations of turbulent flow in a driven cavity

Direct numerical simulations (DNS) of 2 and 3D turbulent flows in a lid-driven cavity have been performed. DNS are numerical solutions of the unsteady (here: incompressible) Navier-Stokes equations that compute the evolution of all dynamically significant scales of motion. In view of the large computing resources needed for DNS cost-effective and accurate numerical methods are to be selected. Here, various-order accurate spatial discretization methods for DNS have been evaluated by applying them to the 2D driven cavity at Re = 22,000. To analyze the results of the DNS of the 2D flow in a driven cavity at Re = 22,000 the proper orthogonal decomposition (POD) technique has been applied. POD is an unbiased method to determine coherent structures. The Galerkin projection of the Navier-Stokes equations on the space spanned by the POD-basis-functions yields a relatively low-dimensional set of ordinary differential equations that mimics the dynamics of the Navier-Stokes equations. 3D DNS with no-slip conditions at all walls of the cavity have been performed at both Re = 3,200 and Re = 10,000. The results reproduce the experimentally observed Taylor-Görtler-like vortices.

Samenstelling van rundergehakt

In oktober 1989 werden 100 monsters rundergehakt onderzocht op de chemische samenstelling. Dertien van de honderd monsters waren ingekocht als mager rundergehakt. De monsters werden onderzocht op de gehalten aan vocht, vet, eiwit, collageen en op de toevoeging van varkensvlees. Uit de analyseresultaten werden de vocht/eiwitverhoudingen en de collageen/eiwitverhoudingen berekend. Zeventien monsters voldeden niet aan in de Warenwet gestelde eisen: vijf als magere gehakt verkochte monsters bevatten meer dan 20% vet en in twaalf monsters werd meer dan 10% varkensvlees aangetoond. Uit vergelijking met ander in Nederland (Vermunt 1986 en de Boer et al., 1990) en in Engeland (Hudson et al., 1986) uitgevoerd onderzoek blijkt dat de analyseresultaten goed met elkaar overeenkomen. De enige duidelijke verschillen waren dat de Boer et al. minder vet en minder monsters met varkensvlees vonden

Summary of results and conclusions from the first phase (1988 - 1989) of the Netherlands research programme "Ecological rehabilitation Rhine"

In 1988 a research program for the ecological rehabilitation of the river Rhine was started. In this research program three Dutch governmental institutes are working together: the Institute for Inland Water Management and Waste Water Treatment (D.B.W/RIZA), the National Institute for Public Health and Environmental Protection (RTVM) and the Netherlands Institute for Fishery Investigations (RTVO). The research program covers the period 1988-1991 and amounts to 20 manyears per year