A new annular lift fan configuration that has very high lift efficiency is explored by using a numerical scheme. The inlet lip radius and diffuser angle are maximized by semicircle duct walls and the location of the lift fan is moved from the throat to the diffuser area to maximize the diffusion effect of the ducted fan. The improved lift fan achieves the figure of merit of 0.772 and the power ...

Squids use a pulsed jet and fin movements to swim both arms-first (forward) and tail-first (backward). Given the complexity of the squid multi-propulsor system, 3D velocimetry techniques are required for the comprehensive study of wake dynamics. Defocusing digital particle tracking velocimetry, a volumetric velocimetry technique, and high-speed videography were used to study arms-first and tail...

Previous studies on the sound attenuation in particle-laden flows under Stokesian drag and conduction-controlled heat transfer have been extended to accommodate the nonlinear drag and heat transfer. It has been shown that for large particle-to-fluid density ratio, the particle Reynolds number bears a cubic relationship with omegatau(d) (where omega is the circular frequency and tau(d) is the St...

This paper discusses our efforts to simulate large systems of bubbles in complex geometries, with specific application to modeling cavitation instabilities. An important unstable regime is the transition from sheet-to-cloud cavitation (SCC). Experiments performed by Callenaere et al. (2001) highlight the unsteady flow structures of SCC, which is characterized by unstable regions of vapor bubble...

The dynamical origin of midlatitude zonal-jet variability is examined in a thermally forced, quasi-geostrophic, two-layer channel model on a β-plane. The model’s behavior is studied as a function of the bottom-friction strength. Two distinct zonal-flow states exist at realistic, low and intermediate values of the bottom drag; these two states are maintained by the eddies and differ mainly in te...

The impact of transient mountain waves on a large-scale flow is examined through idealized numerical simulations of the passage of a time-evolving synoptic-scale jet over an isolated 3D mountain. Both the global momentum budget and the spatial flow response are examined to illustrate the impact of transient mountain waves on the large-scale flow. Additionally, aspects of the spatial response ar...

The persistence of the North Atlantic Oscillation (NAO) is studied using observations of the threedimensional vorticity budget in the Atlantic sector. Analysis of the relative vorticity tendency equation shows that convergence of eddy vorticity flux in the upper troposphere counteracts the effect of anomalous largescale divergence at the upper level. At low levels, the convergence associated wi...

and suppressing fluctuating amplitude of the dynamic wind loads acting on the test model. With 24 suction/jet holes evenly distributed over the cylindrical test model (i.e., the N13 design of the present study), the passive jet control method was found to be able to achieve up to 33.7 % in drag reduction and 90.6 % in fluctuating wind loading suppression, in comparison with the baseline case. T...