Simulation of the askervein flow. Part 2: Large-eddy simulations

• Type: Article in International Scientific Journal
• Date: 2007

Authors

A. Silva Lopes (Author) Other; José Laginha Palma (Author) FEUP; Castro, FA (Author) Other

Journal

Title: Boundary-Layer Meteorology

Vol. 125 No. 1

Pages: 85-108

ISSN: 0006-8314

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 51 Citations

Scopus - 74 Citations

Other information

Authenticus ID: P-004-6XN

DOI: 10.1007/s10546-007-9195-4

Abstract (EN): Large- eddy simulations of the neutrally stratified flow over the Askervein Hill were performed, to improve the knowledge of the flow obtained from fieldmeasurements and numerical simulations with Reynolds averaged Navier- Stokes ( RANS) methods. A Lagrangian dynamic subgrid model was used but, to avoid the underdissipative character near the ground, it was merged with a damped Smagorinsky model. Simulations of a flat boundarylayer flow with this subgrid model showed that the turbulent vertical motions and shear stress were better resolved using grids with a stream to spanwise aspect ratio Delta x/ Delta y = 2 than with an aspect ratio Delta x/ Delta y = 1. Regarding the flow over the Askervein Hill, it was found that large- eddy simulations provide an acceptable solution for the mean- velocity field and better predictions of the turbulent kinetic energy in the upstream side of the hill than the k - epsilon model. However, as with the k - e model, grid convergence was not achieved in the lee side and the size of the zone with reversed flow increased with the grid refinement. Nevertheless, the existence of the intermittent separation predicted with unsteady RANS in part one of this work seems unquestionable, due to the deceleration of the flow. In our opinion, a better modelling of the decelerating boundary layer in the lee side is required to improve the results obtained using equilibrium assumptions and achieve grid convergence.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 24