Showing papers by "Lars Davidson published in 1993"

Numerical simulation of vortex shedding past triangular cylinders at high Reynolds number using a k‐ε turbulence model

Abstract: Calculations of unsteady turbulent flow around and behind triangular-shaped flameholders using a finite volume code with a k-e model of turbulence are presented. The flow behind the flameholders is found to be unsteady (a von Karman vortex street appears) with a well defined Strouhal frequency (predicted Sr=0·27 compared with an experimental value of 0·25). The predicted profiles of velocity and fluctuating kinetic energy agree well with experiments. The periodic motions in the vortex street are shown to be far more important than the turbulent stochastic motions in exchanging momentum in the transversal direction. The pressure-velocity coupling is handled with the SIMPLEC pressure correction procedure. The discretization in time is fully implicit and 90 times steps are used to resolve one time cycle. It was found that to capture the vortex street it is very important that the grid spacing is sufficiently fine (180 × 100).

Employment of second‐moment closure for calculation of turbulent recirculating flows in complex geometries with collocated variable arrangement

Abstract: This paper addresses the implementation of second-moment closure into a collocated variable arrangement body-fitted-finite-volume scheme in which Cartesian velocity components are used. The methods for avoiding instability in the solution procedure are described. A new method for the treatment of the near-wall regions for the momentum equations, as well as the prescription of the stresses at the wall, is described in detail. The performance of the methodology is assessed by applying it to two flow situations, where experimental data are available: the flow over a backward step, and the flow through a sinusoidal pipe constriction. The results are very promising.