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...

Statistical flow modelling does not provide enough detail for many flows of engineering relevance in which unsteadiness is a central feature. This applies particularly to bluff-bodies and assemblies comprising bluff components for which the resolution of peak forces, unsteady loading, acoustics and fatigue are of interest as part of the design process. An example application which has been stud...

Today, Flapping Micro Aerial Vehicles (MAV) are used in many different applications. Reynolds Number for this kind of aerial vehicle is about 104 ~ 105 which shows dominancy of inertial effects in comparison of viscous effects in flow field except adjacent of the solid boundaries. Due to periodic flapping stroke, fluid flow is unsteady. In addition, these creatures have some complexities in kin...

A number of closed-form fundamental solutions for generalized unsteady Oseen and Stokes flows associated with arbitrary time-dependent translational and rotational motions have been developed. These solutions are decomposed into two parts corresponding to a longitudinal wave and a transversal wave. As examples of application, the hydrodynamic forces acting on a sphere and on a circular cylinder...

An analysis is suggested to study the impact of Hall currents in Jeffrey fluid which is chemically reactive through a porous medium limited by a semi-infinite vertical permeable plate within the existence of heat generation. An evenly distributed magnetic field turns vertically on the porous surface which absorbs the Jeffrey fluid with a changed suction velocity with time. The analytical expres...

A compensated compactness framework is established for sonic-subsonic approximate solutions to the two-dimensional Euler equations for steady irrotational flows that may contain stagnation points. Only crude estimates are required for establishing compactness. It follows that the set of subsonic irrotational solutions to the Euler equations is compact; thus flows with sonic points over an obsta...

Measurements of air–water flow properties are reasonably simple in steady flows, but not so in unsteady flows. Some studies investigated periodic flows in which instantaneous data were averaged over several cycles. During the present work, new unsteady air–water flow measurements were performed in sudden open channel flow surges. Unsteady air–water flow measurements were performed in the wave f...

In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to exp...

This paper presents a review and discussion on the numerical studies on steady and unsteady flow in collapsible channels using both the fluid-membrane model and the fluid-beam model. The aim of the research is to explore the possible mechanisms of self-excited oscillations observed in experiments on flow in collapsible tubes. The existence and stability of the steady solutions for different con...