It is well known that, in steady isentropic expansion of a gas from a reservoir, the maximum mass flux density, pu, occurs at Mach number M=u/a= 1 (p, u, and a are the local values of density, velocity, and speed of sound, respectively; po, 0, and a0 are corresponding reservoir values.) The proof is usually given for the special case of a perfect gas and it does not seem to be well known that t...

A relaxed splitting preconditioner based on matrix splitting is introduced in this paper for linear systems of saddle point problem arising from numerical solution of the incompressible NavierStokes equations. Spectral analysis of the preconditioned matrix is presented, and numerical experiments are carried out to illustrate the convergence behavior of the preconditioner for solving both steady...

Flows containing steady or nearly steady strong shocks on parts of the flow field, and unsteady turbulence with shocklets on other parts of the flow field are difficult to capture accurately and efficiently employing the same numerical scheme, even under the multiblock grid or adaptive grid refinement framework. While sixthorder or higher-order shock-capturing methods are appropriate for unstea...

We present an adaptation of the lattice BGK method for fast convergence of simulations of laminar time-dependent flows. The technique is an extension to the recent accelerated procedures for steady flow computations. Being based on Mach number annealing, the present technique substantially improves the accuracy and computational efficiency of the standard lattice BGK method for such unsteady fl...

The induced transient viscous flow due to a suddenly stretched surface is studied. After a similarity transform, the unsteady Navier–Stokes equation is solved by several methods, including perturbation for small times, numerical integration, and asymptotic analysis for large times. It is found that the validity of the small-time series can be greatly extended and the approach to steady state is...

Retrospective cost adaptive control is applied to low Reynolds number aerodynamics around an SD7003 airfoil with a dielectric barrier discharge (DBD) actuator located near the leading edge. The adaptive control algorithm uses knowledge of Markov parameters to capture information about any nonminimum-phase zeros in the dynamics. In this paper, we explore the impact of the adaptive controller on ...

Despite of a lot of efforts and interesting results, accretion disk theory is still under development and there are several unknowns: specifically, all available models are in the steady state approximation. In this letter, we investigate unsteady motion, beginning with shock wave–turbulence interaction. Indeed, unsteady flow allows this type of interaction, which in turn results in substantial...

This study deals with the use of optimization algorithms to determine efficient parameters of flow control devices. To improve the performance of systems characterized by detached flows and vortex shedding, the use of flow control devices such as oscillatory jets, are intensively studied, using numerical as well as experimental methods. However, the determination of efficient control parameters...