THREE-DIMENSIONAL ANALYSIS OF TURBINE ROTOR FLOW INCLUDING TIP CLEARANCE

A 3D Navier-Stokes investigation of a high pressure turbine rotor blade including tip clearance effects is presented. The 3D Navier-Stokes code developed at ONERA solves the three-dimensional unsteady set of mass-averaged Navier-Stokes equations by the finite volume technique. A one step Lax-Wendroff type scheme is used in a rotating frame of reference. An implicit residual smoothing technique has been implemented, which accelerates the convergence towards the steady state. A mixing length model adapted to 3D configurations is used. The turbine rotor flow is calculated at transonic operating conditions. The tip clearance effect is taken into account. The gap region is discretized using more than 55,000 points within a multi-domain approach. The solution accounts for the relative motion of the blade and casing surfaces. The total mesh is composed of five sub-domains and counts 710,000 discretization points

Solution Strategies for Integration of Semi-Discretized Flow Equations in elsA and CEDRE.

International audienceThis paper is devoted to the presention of a selection of time integration methods used in the Onera elsA and Cedre software dedicated to the resolution of the compressible Navier-Stokes equations. The selected methodsare given in the framework of steady and unsteady flow simulations. Emphasis is put on methods for the resolution of algebraic systems associated with time integration methods for space-discretized equations

A residual-based variational multiscale discontinuous galerkin method for turbulent flows

International audienceTurbulent flows in aeronautical applications typically have a very wide range of length and time scales characterized by their high Reynolds numbers. Traditionally, the prohibitively large computational cost implied by a high Reynolds number has made physical modelling rather than direct computation of turbulent scales a more popular approach in the industry. While well-calibrated turbulence models can provide good accuracy at reasonable computational costs, they tend to have a very limited range of applicability. In particular, flows with inhomogeneous features sensitive to small errors, such as flow with detachment, cannot be accurately predicted by conventional models and require computing a greater range of turbulent scales. Large-eddy simulation (LES) aims to resolve all relevant turbulent scales while employing more fundamental models to account for the influence of the unresolved scales. Therefore, it has great potential for a more universal turbulence simulation methodology that is valid for any configuration. In order to make LES a tool of engineering practice, it is necessary to address issues of computational cost, handling of complex geometries and compatibility of the employed models with the used numerical method. In this work, we propose a residual- based variational multiscale discontinuous Galerkin method to address these issues and to ultimately improve efficiency by exploiting its flexibility in local refinement. The variational multiscale (VMS) [1] approach is a framework for designing numerical methods and associated models for multiscale phenomena. In this approach, the scales not resolved by the numerical scheme are modelled by a fine scale model. This apprach is particularly well-suited for higher order methods, since the model term does not add any low order consistency errors. In the context of LES, many VMS variants have been proposed, with implicit [2] and explicit [3] fine scale models. The implicit models have the disadvantage of introducing additional degrees of freedom for the fine scales, leading to a three-level decomposition of scales. In this work we concentrate on extending the cheaper explicit residual- based fine scale model developed in the framework of continuous finite element methods [3] to discontinuous Galerkin (DG) [4] methods to benefit from their excellent scalability properties in simulating unsteady phenomena on parallel computers. DG methods have been successfully used in the variational multiscale setting for the large-eddy simulation of turbulence [5, 6] with implicit fine scale models. In this work we propose a cheaper explicit fine scale model based on a scaling of the cell and face residuals of the resolved scales. We numerically explore various options for constructing residual-based fine scale models for DG discretizations. These methods differ in how (or whether) the jump residuals are taken into account for the fine scale model. We compare these options using the viscous Burgers’ equation in 1D to note that residual-based VMS DG with even the simplest fine scale model that disregards interface jumps gives results that are better than the plain DG method for underresoved simulations. In the second part of this study, we apply the proposed methodology to the compressible Navier-Stokes equations. We perform LES of wall-bounded turbulence based on the proposed residual-based VMS DG method and compare our results to the results obtained through implicit LES and LES based on the three-level VMS DG method in terms of accuracy and computational cost. We conclude that the proposed residual-based VMS DG method is competitive with the three-level VMS DG in terms of accuracy while retaining only the coarse scale degrees of freedom. In terms of computational cost, the proposed method is better than the three-level VMS and competitive with implicit LES

Recent developments performed at ONERA for the simulation of 3D inviscid and viscous flows in turbomachinery by the solution of Euler and Navier-Stokes equations

Communication to : 11th ISABE, Tokyo, JP, September 20-24, 1993SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1993 n.155 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Space Discretization Methods

International audienceOnera codes for CFD and Energetics are mostly based on a finite volume methodology. Within this common framework, a wide variety of space discretization techniques are available depending on the required degree of precision, on the kind of mesh and on the application domain. This paper describes three particular topics whichare central to the codes developed at Onera. The first section discusses cell-centered and cell-vertex techniques in the context of structured meshes and their extension to unstructured zones. The second part shows how efficient third order schemes can be implemented on Cartesian and curvilinear overlapping grids. Finally, the third section presents a Muscl-type discretization methodology currently used on general polyhedralmeshes, with indications on its generalization to high-order precision

Application des calculs Navier-Stokes a l'aerodynamique des turbines et des compresseurs

30"eme colloque d'aerodynamique appliquee : utilisation des calculs 'Navier-Stokes' pour les applications, Nantes (France), 25-27 octobre 1993SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1994 n.17 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Numerical methods and results for turbulent flows around transport aircrafts

Communication to : 1st ONERA-DLR Aerospace symposium, Paris (France), June 21-24, 1999SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1999 n.147 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc