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A numerical method for unsteady flows

Nicola Botta, Rolf Jeltsch (1995)

Applications of Mathematics

A high resolution finite volume method for the computation of unsteady solutions of the Euler equations in two space dimensions is presented and validated. The scheme is of Godunov-type. The first order part of the flux function uses the approximate Riemann problem solver of Pandolfi and here a new derivation of this solver is presented. This construction paves the way to understand the conditions under which the scheme satisfies an entropy condition. The extension to higher order is done by applying...

Automated CFD Analysis for the Investigation of Flight Handling Qualities

M. Ghoreyshi, K. J. Badcock, A. Da Ronch, D. Vallespin, A. Rizzi (2011)

Mathematical Modelling of Natural Phenomena

Physics based simulation is widely seen as a way of increasing the information about aircraft designs earlier in their definition, thus helping with the avoidance of unanticipated problems as the design is refined. This paper reports on an effort to assess the automated use of computational fluid dynamics level aerodynamics for the development of tables for flight dynamics analysis at the conceptual stage. These tables are then used to calculate...

Control of transonic shock positions

Olivier Pironneau (2002)

ESAIM: Control, Optimisation and Calculus of Variations

We wish to show how the shock position in a nozzle could be controlled. Optimal control theory and algorithm is applied to the transonic equation. The difficulty is that the derivative with respect to the shock position involves a Dirac mass. The one dimensional case is solved, the two dimensional one is analyzed .

Control of Transonic Shock Positions

Olivier Pironneau (2010)

ESAIM: Control, Optimisation and Calculus of Variations

We wish to show how the shock position in a nozzle could be controlled. Optimal control theory and algorithm is applied to the transonic equation. The difficulty is that the derivative with respect to the shock position involves a Dirac mass. The one dimensional case is solved, the two dimensional one is analyzed .

Free boundary problems and transonic shocks for the Euler equations in unbounded domains

Gui-Qiang Chen, Mikhail Feldman (2004)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We establish the existence and stability of multidimensional transonic shocks (hyperbolic-elliptic shocks), which are not nearly orthogonal to the flow direction, for the Euler equations for steady compressible potential fluids in unbounded domains in n , n 3 . The Euler equations can be written as a second order nonlinear equation of mixed hyperbolic-elliptic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the...

Global in Time Stability of Steady Shocks in Nozzles

Jeffrey Rauch, Chunjing Xie, Zhouping Xin (2011/2012)

Séminaire Laurent Schwartz — EDP et applications

We prove global dynamical stability of steady transonic shock solutions in divergent quasi-one-dimensional nozzles. One of the key improvements compared with previous results is that we assume neither the smallness of the slope of the nozzle nor the weakness of the shock strength. A key ingredient of the proof are the derivation a exponentially decaying energy estimates for a linearized problem.

High order finite volume schemes for numerical solution of 2D and 3D transonic flows

Jiří Fürst, Karel Kozel, Petr Furmánek (2009)

Kybernetika

The aim of this article is a qualitative analysis of two modern finite volume (FVM) schemes. First one is the so called Modified Causon’s scheme, which is based on the classical MacCormack FVM scheme in total variation diminishing (TVD) form, but is simplified in such a way that the demands on computational power are much smaller without loss of accuracy. Second one is implicit WLSQR (Weighted Least Square Reconstruction) scheme combined with various types of numerical fluxes (AUSMPW+ and HLLC)....

Non-uniqueness of almost unidirectional inviscid compressible flow

Pavel Šolín, Karel Segeth (2004)

Applications of Mathematics

Our aim is to find roots of the non-unique behavior of gases which can be observed in certain axisymmetric nozzle geometries under special flow regimes. For this purpose, we use several versions of the compressible Euler equations. We show that the main reason for the non-uniqueness is hidden in the energy decomposition into its internal and kinetic parts, and their complementary behavior. It turns out that, at least for inviscid compressible flows, a bifurcation can occur only at flow regimes with...

Numerical simulation of 3D transonic flow through cascades

Jaroslav Fořt, Jiří Fürst, J. Halama, Karel Kozel (2001)

Mathematica Bohemica

The paper deals with the numerical solution of 3D transonic flow through axial turbine cascades. Finite volume methods based on TVD MacCormack cell-centered and Ni’s cell-vertex schemes are discussed. A comparison of numerical results for 3D stator and rotor cascades is presented.

Numerical solution of several models of internal transonic flow

Jaroslav Fořt, Karel Kozel (2003)

Applications of Mathematics

The paper deals with numerical solution of internal flow problems. It mentions a long tradition of mathematical modeling of internal flow, especially transonic flow at our department. Several models of flow based on potential equation, Euler equations, Navier-Stokes and Reynolds averaged Navier-Stokes equations with proper closure are considered. Some mathematical and numerical properties of the model are mentioned and numerical results achieved by in-house developed methods are presented.

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