A stochastic perturbation method to generate inflow turbulence in large-eddy simulation models: Application to neutrally stratified atmospheric boundary layers
- Earth and Environmental Sciences Division (EES-16), Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)
- National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307 (United States)
- von Karman Institute for Fluid Dynamics, 72 Chaussée de Waterloo, B-1640 Rhode-St-Genèse (Belgium)
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
Despite the variety of existing methods, efficient generation of turbulent inflow conditions for large-eddy simulation (LES) models remains a challenging and active research area. Herein, we extend our previous research on the cell perturbation method, which uses a novel stochastic approach based upon finite amplitude perturbations of the potential temperature field applied within a region near the inflow boundaries of the LES domain [Muñoz-Esparza et al., “Bridging the transition from mesoscale to microscale turbulence in numerical weather prediction models,” Boundary-Layer Meteorol., 153, 409–440 (2014)]. The objective was twofold: (i) to identify the governing parameters of the method and their optimum values and (ii) to generalize the results over a broad range of atmospheric large-scale forcing conditions, U{sub g} = 5 − 25 m s{sup −1}, where U{sub g} is the geostrophic wind. We identified the perturbation Eckert number, Ec=U{sub g}{sup 2}/ρc{sub p}θ{sup ~}{sub pm}, to be the parameter governing the flow transition to turbulence in neutrally stratified boundary layers. Here, θ{sup ~}{sub pm} is the maximum perturbation amplitude applied, c{sub p} is the specific heat capacity at constant pressure, and ρ is the density. The optimal Eckert number was found for nonlinear perturbations allowed by Ec ≈ 0.16, which instigate formation of hairpin-like vortices that most rapidly transition to a developed turbulent state. Larger Ec numbers (linear small-amplitude perturbations) result in streaky structures requiring larger fetches to reach the quasi-equilibrium solution, while smaller Ec numbers lead to buoyancy dominated perturbations exhibiting difficulties for hairpin-like vortices to emerge. Cell perturbations with wavelengths within the inertial range of three-dimensional turbulence achieved identical quasi-equilibrium values of resolved turbulent kinetic energy, q, and Reynolds-shear stress, . In contrast, large-scale perturbations acting at the production range exhibited reduced levels of , due to the formation of coherent streamwise structures, while q was maintained, requiring larger fetches for the turbulent solution to stabilize. Additionally, the cell perturbation method was compared to a synthetic turbulence generator. The proposed stochastic approach provided at least the same efficiency in developing realistic turbulence, while accelerating the formation of large-scales associated with production of turbulent kinetic energy. Also, it is computationally inexpensive and does not require any turbulent information.
- OSTI ID:
- 22403216
- Journal Information:
- Physics of Fluids (1994), Vol. 27, Issue 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-6631
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
AMPLITUDES
BOUNDARY LAYERS
DISTURBANCES
EQUILIBRIUM
KINETIC ENERGY
LARGE-EDDY SIMULATION
MATHEMATICAL SOLUTIONS
NONLINEAR PROBLEMS
PERTURBATION THEORY
REYNOLDS NUMBER
SHEAR
SPECIFIC HEAT
STOCHASTIC PROCESSES
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE
VORTICES