A simplified model was employed to develop mathematically equations that describe the unsteadystate behavior of naturally fractured reservoirs, The analysis resulted in an equation of flow of radial symmetry whose solution, for the infinite case, is identical in form and function to that describing the unsteady-state behavior of homogeneous reservoirs. Accepting the assumed model, for all pract...

Propulsor crashback is an off-design operating condition where a propulsor rotates in the reverse direction to yield negative thrust. Crashback is characterized by the interaction of the free stream with the reverse flow generated by propulsor rotation. This causes a highly unsteady vortex ring which leads to flow separation and unsteady forces and moments on the blades. Large eddy simulation (...

A non-oscillatory numerical scheme based on a general solution of unsteady advection–di usion equations is presented. A general solution for initial value problems of linear two-dimensional unsteady advection–di usion equations is obtained using the spectral method. The resulting numerical scheme is explicit with respect to time, and ful lls the Patankar’s positive coe cients condition for any ...

The unsteady-state aerodynamic performance results of various MEMS-fabricated titanium-alloy wing designs are presented. These wing are tested in a high-quality low-speed wind tunnel with velocity uniformity of 0.5%.. For the first time, we have identified the importance of spanwise stiffness effect in generating the leading edge vortices. These vortices, generated around each wing, cause a low...

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing oil airfoils. The unsteady suction and blo...

We analyze the dynamics of a spatially extended system with bistability between a homogeneous stationary state and an unstable fixed point surrounded by an oscillatory state. We show that a wave front extinguishes homogeneous oscillations, replacing them with unsteady oscillations. A traveling wave solution connects the unsteady oscillations to the stationary state. The difference in potentials...

This paper reports comparative experiments with two novel and one conventional thrust control algorithms for the unsteady (transient) control of thrust generated by conventional bladedpropeller marine thrusters. First, comparative experiments with three different thrust control algorithms over a wide range of unsteady operating conditions suggest that model-based control algorithms offer transi...

Turbulent bursting events play a major role in natural systems in terms of sediment scour, transport and accretion as well as contaminant mixing and dispersion. The "bursts" were extensively studied in laboratory experiments under steady flow conditions, but rarely tested in unsteady natural flows. Herein a technique is described for the detection and analysis of turbulent events within large c...