An efficient pressure-based methodology for low Mach flow simulations

International audienc

The simulation of low Mach flows: from the AUSM-IT flux scheme to ATCBC boundary conditions

Seminar - Universidad Nacional de Córdoba - ArgentinaInternational audienc

Pressure-based methodologies for zero Mach and low Mach flow simulations

International audienc

Un algorithme pour la simulation du transport convectif et de la propagation acoustique à tout mombre de Mach

A pressure-correction algorithm is presented for compressible fluid flow regimes. It is well-suited to simulate flows at all levels of Mach number with smooth and discontinuous flow field changes, by providing a precise representation of convective transport and acoustic propagation. The co-located finite volume space discretisation is used with the AUSM flux splitting. It is demonstrated that two ingredients are essential for obtaining good quality solutions : the presence of an inertia term in the transporting velocity expression ; a velocity difference diffusive term in the face pressure expression, with a correct Mach number scaling to recover the hydrodynamic and acoustic low Mach number limits. To meet these two requirements, a new flux scheme, named MIAU, for Momentum Interpolation with Advection Upstream splitting is proposed

A Robust methodology for RANS Simulations of Highly Underexpanded Jets

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Pressure-velocity coupling allowing acoustic calculation in low Mach number flow

International audienceLow Mach number flow computation in co-located grid arrangement requires pressure-velocity coupling in order to prevent the checkerboard phenomenon. Two broad categories of pressure-velocity coupling methods for unsteady flows can be distinguished based on the time-step dependency of the coupling coefficient in the definition of the transporting velocity on a face of a control volume. As an example of the time-step independent category , the AUSM +-up scheme is studied. As an example of the second category, Rhie-Chow momentum interpolation methods are studied. Within the momentum interpolation techniques, again two broad categories can be distinguished based on the time-step dependency of the coupling coefficient used for unsteady flow computations, but when a steady state is reached. Variants of Rhie-Chow interpolation methods in each subcategory are studied on critical test cases. The result of the study is that for a good representation of unsteady flows containing acoustic information, the pressure-velocity coupling coefficient must explicitly depend on the time-step, but that the transporting velocity must become independent of the time-step when a steady state is reached

Behaviour of upwind schemes in low Mach number flow

International audienceIn the present work, we are interested in the direct numerical simulation of the compressible Euler and Navier Stokes equations at low Mach number regime. First, we propose a review of existing work on the subject in order to identify the issues raised by the simulation of in this kind of flow, and the existing relevant solutions. Then, we will test different selected compressible low Mach solvers using the discontinuous Galerkin space discretisation and discuss about their behaviour

Interferencia de flujo entre cilindros circulares en disposición tándem cercanos al suelo

National audienceThis study focuses on the numerical simulations of the flow around two tandem cylinders placed near a wall. The cylinders are immersed in a flow with a boundary layer profile at a subcritical Reynolds number (Re=10000). The three-dimensional transient turbulent flow around the cylinders is simulated numerically using the Scale-Adaptive Simulation (SAS) turbulence model by means of the Fluent code. The effects of wake interference due to the proximity between the cylinders and the proximity with the wall are examined through the values of drag and lift coefficients. Also, the details of the flow fields in the near wake of the cylinders are analyzed. The results are compared with experimental and numerical results reported in the literature, as well as to the case of a single cylinder near a wall.Este trabajo se enfoca en estudiar por medio de simulaciones numéricas el flujo alrededor de dos cilindros circulares en tándem considerando su proximidad con el suelo. Los cilindros se encuentran inmersos en un flujo con capa límite del suelo para un número de Reynolds subcrítico Re=10000. Para modelar el flujo turbulento tridimensional y dependiente del tiempo se utiliza el modelo de turbulencia SAS (Scale-Adaptive Simulation) por medio del código Fluent. La interferencia entre los cilindros y con el suelo se analiza para distintas separaciones entre cilindros y distintas proximidades con el suelo. Se examinan los coeficientes de sustentación, de arrastre, y el comportamiento del desprendimiento de vór-tices. Los resultados son comparados con resultados de cilindros en tándem de ensayos experimentales y simulaciones numéricas disponibles en la literatura, como así también con el caso de un cilindro solo cercano al suelo

Modelizacion numerica de cargas de viento sobre un tanque de almacenamiento de combustible

National audienceOne of the structural problems detected on oil storage tanks is wind-induced buckling failure. Accurate estimation of wind loads is important for the evaluation of structural integrity of these facilities. In this context, a numerical study is presented, employing the Reynolds Averaging Navier Stokes (RANS) methodology for the prediction of wind-induced pressure loads over a cylindrical storage tank. Mean pressure distributions obtained through RANS turbulence models, are compared with atmospheric boundary layer wind tunnel experimental measurements for a tank with both closed planar and conical roof shapes. Different aspect ratios and Reynolds numbers representative of the conditions present in oil storage tanks exposed to the atmosphere are considered. Details regarding both the employed numerical methodology and the computer implementation are discussed and presented. Finally, the conclusions obtained based on the present numerical study are introduced.Uno de los problemas estructurales detectados en tanques de almacenamiento de combustible es la falla por pandeo debido a cargas de viento. La adecuada estimación de estas cargas es importante para la evaluación de la integridad estructural de los mismos. En este contexto, se presenta un estudio numérico empleando la metodología Reynolds Averaging Navier Stokes (RANS) para la predicción de cargas de presión producida por el flujo de viento atmosférico sobre un tanque de almacenamiento ci-líndrico. Distribuciones de presión media obtenidas empleando distintos modelos de turbulencia RANS, son comparadas con las mediciones relevadas en un túnel de viento de capa límite atmosférica para un tanque con techo cerrado de forma plana y techo cónico de 25 grados. Diferentes relaciones de aspecto y números de Reynolds representativos de las condiciones presentes en tanques de almacenamiento de combustible expuestos a la atmósfera son considerados. Detalles sobre la metodología numérica em-pleada y aspectos de la implementación computacional son discutidos y presentados. Finalmente, se introducen las conclusiones obtenidas a partir del presente análisis numérico

Pertinence et limitations des modèles d'impédance acoustique au niveau de parois multiperforées des chambres de combustion aéronautiques

L'étude thermo-acoustique de chambres de combustion aéronautiques requiert l'implémentation de conditions aux limites pertinentes. Ceci passe en particulier, par la modélisation approprié de l'impédance acoustique associé aux parois multiperforées. La présente étude établit un panorama d'ensemble des approches théoriques et des modèles d'impédance acoustique considérés jusqu'à présent en précisant les conditions d'emploi et limitations éventuelles pour le cas spécifique d'une paroi multiperforée de chambre de combustion