This paper proposes and validates a jet formation criterion for synthetic jet actuators. The synthetic jet is a zero net mass flux device, adding additional momentum but no mass to its surroundings. Jet formation is defined as a mean outward velocity along the jet axis and corresponds to the clear formation of shed vortices. It is shown that the synthetic jet formation is governed by the Strouh...

A thermal characterization study of laminar air jet impingement cooling of electronic components within a geometry representative of the CPU compartment of a typical portable computer is reported. A finite control volume technique was used to solve for the velocity and temperature fields. Convection, conduction and radiation effects were included in the simulations. The range of jet Reynolds nu...

A pro®le tracking system (PTS) is developed to make measurements at previously inaccessible dimension-less distances from a discharge in a moving environment. With this system the measuring components remain stationary as the source is towed away from them. Image processing techniques are then employed to track concentration pro®les through a sequence of images, which are a constant distance fr...

Prediction of jet noise is important for civil aircraft. Some CAA methodologies predict the full unsteady flow field of a jet in order to ascertain the far-field noise. The approach adopted here is to utilise CFD to obtain steady state information using a turbulence model and hence to provide inputs to a semi-empirical noise model, herein after referred to as the four source model. Predictions ...

We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of the gravitational collapse of a magnetized rotating massive star as a model of gamma ray bursts (GRBs). Initially, a few M⊙ black hole is produced at the center of the stellar remnant with a weak shock standing at a radius of a few hundred km and the post-shock gas falling onto the central black hole...

We present two-dimensional hydrodynamical simulations of both jet-and wind-driven models for protostellar outflows in order to make detailed comparisons to the kinematics of observed molecular outflows. The simulations are performed with the ZEUS-2D hydrodynamical code using a simplified equation of state, simplified cooling and no external heating, and no self-gravity. In simulations of steady...

A jet of a Newtonian liquid impacting on a wall at right angle spreads as a thin liquid sheet which preserves the radial symmetry of the jet. We report that for a viscoelastic jet (solution of polyethylene glycol in water) this symmetry can break; close to the wall, the jet cross section becomes faceted and radial steady liquid films (wings) form, which connect the cross-section vertices to the...

Observations of the core of the giant radio galaxy NGC315 made with VLBI interferometers are discussed in the context of a relativistic jet. The sidedness asymmetry suggests Doppler favoritism from a relativistic jet. The presence of moving features in the jet as well as jet counter–jet brightness ratios hint at an accelerating, relativistic jet. An increasing jet velocity is also supported by ...