One of the more promising recent approaches to turbulence modelling is the Variational Multiscale Large Eddy Simulation (VMS LES) method proposed by Hughes et al. [Comp. Visual. Sci., vol. 3, pp. 47-59, 2000]. This method avoids several conceptual issues of traditional filter-based LES by employing a priori scale partitioning in the discretization of the Navier-Stokes equations.Most applications of VMS LES reported to date have been based on hierarchical bases, in particular global spectral methods, in which scale partitioning is straightforward. In the present work we describe the implementation of the methodology in a three-dimensional high-order spectral element method with a nodal basis. We report results from coarse grid simulations of turbulent channel flow at different Reynolds numbers to assess the performance of the model.

SUMMARYThis paper reports the results of spectral element simulations of natural convection in two-dimensional cavities. In particular, a detailed comparison is performed with the reference data for the 8:1 cavity at Ra = 3:4 × 10 5 recently described by Christon et al. [Int. J. Numer. Methods Fluids 2002; 40:953 -980]. The Navier-Stokes equations augmented by the Boussinesq approximation to represent buoyancy e ects are solved by a numerical method based on a spectral element discretization and operator splitting. The computed solutions agree closely with the reference data for both the square and the rectangular cavity conÿgurations.

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We compare the performance of different pressure correction algorithms used as basic solvers in a multigrid method for the solution of the incompressible Navier–Stokes equations on non‐staggered grids. Numerical tests were performed on several cases of lid‐driven cavity flow using four different pressure correction schemes, including the traditional SIMPLE and SIMPLEC methods as well as novel variants, and varying combinations of underrelaxation parameters. The results show that three of the four algorithms tested are robust smoothers for the multigrid solver and that one of the new methods converges fastest in most of the tests. © 1997 John Wiley & Sons, Ltd.

Aerosol dispersion in the area surrounding an existing biological treatment facility is investigated using large-eddy simulation, with the objective to investigate the applicability of computational fluid dynamics to complex real-life problems. The aerosol sources consist of two large aeration ponds that slowly diffuse aerosols into the atmosphere. These sources are modelled as dilute concentrations of a non-buoyant non-reacting pollutant diffusing from two horizontal surfaces. The time frame of the aerosol release is restricted to the order of minutes, justifying a statistically steady inlet boundary condition. The numerical results are compared to wind-tunnel experiments for validation. The wind-tunnel flow characteristics resemble neutral atmospheric conditions with a Reynolds number, based on the boundary-layer thickness, of Re δ ≈ 2 × 10 5 . The numerical inflow conditions are based upon the wind-tunnel flow field. The predicted decay of both the mean and root-mean-square concentrations are in good agreement with experimental data; at 3 m from the ground, the plume mean concentration 200 m downwind of the source is approximately 2% of the source strength. The numerical data in the near-surface layer (0-50 m from the ground) correspond particularly well with the wind-tunnel data. Tentative deposition simulations suggest that there seems to be little difference in the deposition rates of large (1.8 × 10 −5 m) and small (3 × 10 −6 m) particles in the near-field under the flow conditions considered.