Large Eddy Simulation of Stratified Flow over Hills
Final Report Abstract
The major scientific results gained through this project relative to the state of the art are. 1. The separated flow over a 3-D hill is a very important test case for the turbulence modelling and simulation community. It presents challenging features encountered in a broad range of practical three-dimensional flows separating from curved surfaces. The calculations performed in this project have shed light on important fundamental aspects of separation from curved surfaces. 2. The results obtained from the calculations, together with the experimental data by Simpson and co-workers, may be claimed to provide a reliable benchmark for assessing the capabilities of other computational techniques, thereby contributing to progress in obtaining reliable calculation methods for three-dimensinoal separating flows in practice. 3. A high-quality database of stably-stratified turbulent channel flow has been generated. We have considered higher Reynolds numbers than previous works (upto Ret = 550), we have used very large computational boxes to ensure that the flow physics is not constrained and we have considered a wide range of stratification levels. This database can be used to test turbulence models employed in engineering and geophysics simulations. 4. Some fundamental aspects of stably-stratified shear flows have been clari?ed, like for example: the generation of internal gravity waves in the core of the channel and the observation of turbulent-laminar patterns for high levels of stratification. 5. A simple linear model has been able to predict some of the characteristics observed in the DNS of stably-stratified channel flows.
Publications
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(2008) ‘Direct numerical simulations and linear analysis of stably-stratified turbulent channel flow from zero to very strong stratification’, IUTAM - Rotating Stratified Turbulence and Turbulence in the Atmosphere and Oceans, Cambridge, UK
M. García-Villalba, C. Yánez and J.C. del Álamo
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(2008) ‘Turbulence and internal waves in a stably-stratified channel flow’, High Performance Computing in Science and Engineering ’08, W. E. Nagel et al. (eds.), Springer, 217-227
M. García-Villalba and J.C. del Álamo
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(2009) ‘A note on optimal transient growth in turbulent channel flows’, Phys. Fluids, 21, 015109
G. Pujals, M. García-Villalba, C. Cossu and S. Depardon
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(2009) ‘Large eddy simulation of separated flow over a three-dimensional axisymmetric hill’, J. Fluid Mech., 627, p. 55-96
M. García-Villalba, N. Li, W. Rodi and M.A. Leschziner
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(2009) ‘Observation of turbulent-laminar patterns in direct numerical simulation of stably-stratified channel flow’, IUTAM Symposium on Laminar-Turbulent Transition. Stockholm. Sweden
M. García-Villalba and J.C. del Álamo
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(2009) ‘Influence of the approach boundary layer on the flow over an axisymmetric hill at a moderate Reynolds number’, J. Turbulence
M. García-Villalba, J.G. Wissink and W. Rodi
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(2009) ‘Direct numerical simulation of stably-stratified turbulent channel flow’
M. García-Villalba and J.C. del Álamo
