Environmental Engineering Reference
In-Depth Information
1.11 Novel Mesh Adaptive LES Simulations
for Multi-Scale Atmospheric Flows: Application
to the Urban Environment
D. Pavlidis
1
, J.L.M.A. Gomes
1
, G.J. Gorman
1
, E. Aristodemou
1
,
1
2
3
C.C. Pain , H. ApSimon , and A.G. Robins
1
Applied Modelling and Computation Group, Dept. Earth Science and Engineering, Imperial
College London
2
Centre for Environmental Policy, Imperial College London
3
Fluids Research Centre, School of Engineering, University of Surrey
1. Introduction
Effective air quality management necessitates the implementation and validation
of multi-scale models that are able to capture adequate spatial and temporal vari-
ability of urban pollution dispersion patterns. A new LES approach is implemented in
a general purpose CFD model (Fluidity) with anisotropic mesh adaptivity for
simulating turbulent airflows within complex urban environments. The model is
compared to field and wind tunnel data considering a passive tracer dispersion
scenario.
2. Methodology
Fluidity is capable of numerically solving the Navier-Stokes and accompanying
field equations on arbitrary unstructured finite element meshes (Mansoorzadeh
et al., 1998). It uses a moving finite element/spectral element methods which allow
arbitrary movement of the mesh with time dependent problems (Pain et al., 2001).
The LES model used to calculate the eddy viscosity is a variation of the Smagorinsky
model developed by (Bentham, 2003). The advantage of the SGS model used
here over the original Smagorinsky model is that the length-scale is related
directly to the local length-scale of the flow, and is allowed to vary in space and
direction, rather than being fixed and predetermined. For the generation of turbu-
lent inlet boundary conditions the method described and validated in (Pavlidis
et al., 2009) is used. It is based upon the view of turbulence as a superposition of
