Developing large eddy simulation for turbomachinery applications

2009 ◽  
Vol 367 (1899) ◽  
pp. 2999-3013 ◽  
Author(s):  
Simon J. Eastwood ◽  
Paul G. Tucker ◽  
Hao Xia ◽  
Christian Klostermeier
Keyword(s):  
Large Eddy Simulation ◽  
Leading Edge ◽  
Problem Definition ◽  
Navier Stokes ◽  
Complex Geometries ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Chevron Nozzle ◽  
Inflow Conditions

For jets, large eddy resolving simulations are compared for a range of numerical schemes with no subgrid scale (SGS) model and for a range of SGS models with the same scheme. There is little variation in results for the different SGS models, and it is shown that, for schemes which tend towards having dissipative elements, the SGS model can be abandoned, giving what can be termed numerical large eddy simulation (NLES). More complex geometries are investigated, including coaxial and chevron nozzle jets. A near-wall Reynolds-averaged Navier–Stokes (RANS) model is used to cover over streak-like structures that cannot be resolved. Compressor and turbine flows are also successfully computed using a similar NLES–RANS strategy. Upstream of the compressor leading edge, the RANS layer is helpful in preventing premature separation. Capturing the correct flow over the turbine is particularly challenging, but nonetheless the RANS layer is helpful. In relation to the SGS model, for the flows considered, evidence suggests issues such as inflow conditions, problem definition and transition are more influential.

Application of a Dynamic Global-Coefficient Subgrid-Scale Model for Large-Eddy Simulation in Complex Geometries

2007 ◽  
Author(s):  
Donghyun You ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Eddy Viscosity ◽  
Viscosity Model ◽  
Scale Model ◽  
Complex Geometries ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Large Eddy ◽  
Model Coefficient

The application of a dynamic global-coefficient subgrid-scale eddy-viscosity model for large-eddy simulation in complex geometries is presented. The model employs a dynamic procedure for closure of the subgrid-scale eddy-viscosity model developed by Vreman [Phys. Fluids 16, 3670 (2004)]. The model coefficient which is globally constant in space but varies in time is dynamically determined assuming the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation of which utilization was proposed by Park et al. [Phys. Fluids 18, 125109 (2006)]. Like the Vreman’s model with a fixed coefficient and the dynamic-coefficient model of Park et al., the present model predicts zero eddy-viscosity in regions where the vanishing eddy viscosity is theoretically expected. The present dynamic model is especially suitable for large-eddy simulation in complex geometries since it does not require any ad hoc spatial and temporal averaging or clipping of the model coefficient for numerical stabilization and requires only a single-level test filter.

scholarly journals Jet Noise in Airframe Integration and Shielding

2020 ◽  
Vol 10 (2) ◽  
pp. 511
Author(s):  
Saman Salehian ◽  
Reda Mankbadi
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Jet Noise ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Complex Geometries ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

This paper reviews and presents new results on the effect of airframe integration and shielding on jet noise. Available experimental data on integration effects are analyzed. The available options for the computation of jet noise are discussed, and a practical numerical approach for the present topic is recommended. Here, it is demonstrated how a hybrid large eddy simulation—unsteady Reynolds-averaged Navier-Stokes approach can be implemented to simulate the effect of shielding on radiated jet noise. This approach provides results consistent with the experiment and suggests a framework for studying more complex geometries involving airframe integration effects.

Dynamic Global Model for Large Eddy Simulation in Complex Geometries

2011 ◽  
Vol 261-263 ◽  
pp. 837-841
Author(s):  
Wen Quan Wang ◽  
Yan Yan
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Viscous Dissipation ◽  
Global Model ◽  
Complex Geometries ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Model Coefficient ◽  
Global Equilibrium

In the present study, the dynamic Vreman model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation with a global model coefficient are applied to large eddy simulation of turbulent flow in complex geometries. Distributions of pressure, velocity and vorticity as well as some flow structure are gained, which is helpful to examine the performance of SGS model and understand the flow characters in complex geometries.

scholarly journals Applied large eddy simulation

2009 ◽  
Vol 367 (1899) ◽  
pp. 2809-2818 ◽  
Author(s):  
Paul G. Tucker ◽  
Sylvain Lardeau
Keyword(s):  
Large Eddy Simulation ◽  
Computer Modelling ◽  
Industrial Sector ◽  
Problem Definition ◽  
Navier Stokes ◽  
Sector Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Recent Developments ◽  
To Come

Large eddy simulation (LES) is now seen more and more as a viable alternative to current industrial practice, usually based on problem-specific Reynolds-averaged Navier–Stokes (RANS) methods. Access to detailed flow physics is attractive to industry, especially in an environment in which computer modelling is bound to play an ever increasing role. However, the improvement in accuracy and flow detail has substantial cost. This has so far prevented wider industrial use of LES. The purpose of the applied LES discussion meeting was to address questions regarding what is achievable and what is not, given the current technology and knowledge, for an industrial practitioner who is interested in using LES. The use of LES was explored in an application-centred context between diverse fields. The general flow-governing equation form was explored along with various LES models. The errors occurring in LES were analysed. Also, the hybridization of RANS and LES was considered. The importance of modelling relative to boundary conditions, problem definition and other more mundane aspects were examined. It was to an extent concluded that for LES to make most rapid industrial impact, pragmatic hybrid use of LES, implicit LES and RANS elements will probably be needed. Added to this further, highly industrial sector model parametrizations will be required with clear thought on the key target design parameter(s). The combination of good numerical modelling expertise, a sound understanding of turbulence, along with artistry, pragmatism and the use of recent developments in computer science should dramatically add impetus to the industrial uptake of LES. In the light of the numerous technical challenges that remain it appears that for some time to come LES will have echoes of the high levels of technical knowledge required for safe use of RANS but with much greater fidelity.

MATHEMATICAL ANALYSIS FOR THE RATIONAL LARGE EDDY SIMULATION MODEL

2002 ◽  
Vol 12 (08) ◽  
pp. 1131-1152 ◽  
Author(s):  
LUIGI C. BERSELLI ◽  
GIOVANNI P. GALDI ◽  
TRAIAN ILIESCU ◽  
WILLIAM J. LAYTON
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Model ◽  
Stokes Equations ◽  
Strong Solutions ◽  
Navier Stokes ◽  
Subgrid Scale ◽  
Navier Stokes Equations ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy

In this paper we consider the Rational Large Eddy Simulation model recently introduced by Galdi and Layton. We briefly present this model, which (in principle) is similar to others commonly used, and we prove the existence and uniqueness of a class of strong solutions. Contrary to the gradient model, the main feature of this model is that it allows a better control of the kinetic energy. Consequently, to prove existence of strong solutions, we do not need subgrid-scale regularization operators, as proposed by Smagorinsky. We also introduce some breakdown criteria that are related to the Euler and Navier–Stokes equations.

On the modelling of the subgrid-scale and filtered-scale stress tensors in large-eddy simulation

2001 ◽  
Vol 441 ◽  
pp. 119-138 ◽  
Author(s):  
DANIELE CARATI ◽  
GRÉGOIRE S. WINCKELMANS ◽  
HERVÉ JEANMART
Keyword(s):  
Large Eddy Simulation ◽  
Stress Tensor ◽  
Large Scale ◽  
Stokes Equations ◽  
Exact Result ◽  
Navier Stokes ◽  
Exact Nature ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy

The large-eddy simulation (LES) equations are obtained from the application of two operators to the Navier-Stokes equations: a smooth filter and a discretization operator. The introduction ab initio of the discretization influences the structure of the unknown stress in the LES equations, which now contain a subgrid-scale stress tensor mainly due to discretization, and a filtered-scale stress tensor mainly due to filtering. Theoretical arguments are proposed supporting eddy viscosity models for the subgrid-scale stress tensor. However, no exact result can be derived for this term because the discretization is responsible for a loss of information and because its exact nature is usually unknown. The situation is different for the filtered-scale stress tensor for which an exact expansion in terms of the large-scale velocity and its derivatives is derived for a wide class of filters including the Gaussian, the tophat and all discrete filters. As a consequence of this generalized result, the filtered-scale stress tensor is shown to be invariant under the change of sign of the large-scale velocity. This implies that the filtered-scale stress tensor should lead to reversible dynamics in the limit of zero molecular viscosity when the discretization effects are neglected. Numerical results that illustrate this effect are presented together with a discussion on other approaches leading to reversible dynamics like the scale similarity based models and, surprisingly, the dynamic procedure.

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