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Displaying 61 –
80 of
356
The calculation of sound generation and propagation in low Mach number flows requires serious reflections on the characteristics of the underlying equations. Although the compressible Euler/Navier-Stokes equations cover all effects, an approximation via standard compressible solvers does not have the ability to represent acoustic waves correctly. Therefore, different methods have been developed to deal with the problem. In this paper, three of them are considered and compared to each other. They...
The calculation of sound generation and propagation in low
Mach number flows requires serious reflections on the characteristics of the
underlying equations. Although the compressible Euler/Navier-Stokes
equations cover all effects, an approximation via standard compressible
solvers does not have the ability to represent acoustic waves
correctly. Therefore, different methods have been developed to deal with the
problem. In this paper, three of them are considered and compared to each
other....
This article is devoted to incompressible Euler equations (or to Navier-Stokes equations in the vanishing viscosity limit). It describes the propagation of quasi-singularities. The underlying phenomena are consistent with the notion of a cascade of energy.
This work is devoted to the numerical comparison of four active control techniques in order to increase the pressure recovery generated by the deceleration of a slightly compressible viscous flow over a dihedral plane. It is performed by the use of vortex generator jets and intrusive sensors. The governing equations, the two-dimensional direct numerical simulation code and the flow configuration are first briefly recalled. Then, the objective of the control is carefully displayed, and the uncontrolled...
This work is devoted to the numerical comparison of four active control
techniques in order to increase the pressure recovery generated by the
deceleration of a slightly compressible viscous flow over a dihedral plane.
It is performed by the
use of vortex generator jets and intrusive sensors. The governing equations,
the two-dimensional direct numerical simulation code and the
flow configuration are first briefly recalled. Then, the objective of the
control is carefully displayed, and the uncontrolled...
This paper concerns numerical methods for two-phase flows. The governing equations are the compressible 2-velocity, 2-pressure flow model. Pressure and velocity relaxation are included as source terms. Results obtained by a Godunov-type central scheme and a Roe-type upwind scheme are presented. Issues of preservation of pressure equilibrium, and positivity of the partial densities are addressed.
This paper concerns numerical methods for two-phase flows.
The governing equations are the compressible 2-velocity,
2-pressure flow model. Pressure and velocity relaxation
are included as source terms. Results obtained by a
Godunov-type central scheme and a Roe-type upwind scheme
are presented. Issues of preservation of pressure equilibrium,
and positivity of the partial densities are addressed.
We consider models based on conservation laws. For the optimization of such systems, a sensitivity analysis is essential to determine how changes in the decision variables influence the objective function. Here we study the sensitivity with respect to the initial data of objective functions that depend upon the solution of Riemann problems with piecewise linear flux functions. We present representations for the one–sided directional derivatives of the objective functions. The results can be used...
We consider models based on conservation laws. For the optimization
of such systems, a sensitivity analysis is essential to determine
how changes in the decision variables influence the objective
function. Here we study the sensitivity with respect to the initial
data of objective functions that depend upon the solution of Riemann
problems with piecewise linear flux functions. We present
representations for the one–sided directional derivatives of the
objective functions. The results can be used...
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 .
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 .
We consider the initial value problem for degenerate viscous and inviscid scalar conservation laws where the flux function depends on the spatial location through a “rough” coefficient function . We show that the Engquist-Osher (and hence all monotone) finite difference approximations converge to the unique entropy solution of the governing equation if, among other demands, is in , thereby providing alternative (new) existence proofs for entropy solutions of degenerate convection-diffusion equations...
We consider the initial value problem for degenerate
viscous and inviscid scalar conservation laws where the
flux function depends on the spatial location through a
"rough"coefficient function k(x).
We show that the Engquist-Osher
(and hence all monotone)
finite difference approximations converge
to the unique entropy solution
of the governing equation
if, among other demands, k' is in BV, thereby providing
alternative (new) existence proofs for entropy solutions of
degenerate convection-diffusion...
In this paper, we prove the convergence of the current defined from the Schrödinger-Poisson system with the presence of a strong magnetic field toward a dissipative solution of the Euler equations.
In this paper, we prove the convergence of the current defined from the Schrödinger-Poisson system with the presence of a strong magnetic field toward a dissipative solution of the Euler equations.
Currently displaying 61 –
80 of
356