The Hawaiian mesopelagic boundary community, consisting of island-associated, midwater sound-scattering layers, undergoes diel migrations with both vertical and horizontal components. To understand the dynamics of the community’s migration at fine temporal scales, we utilized a bottom-mounted, 200-kHz active-acoustic mooring that transmitted 10 signals every 15min, from dusk until dawn for 5 da...

A numerical implementation of the advection equation is proposed to increase the temporal resolution of PIV time series. The method is based on the principle that velocity fluctuations are transported passively, similar to Taylor's hypothesis of frozen turbulence. In the present work, the advection model is extended to unsteady three-dimensional flows. The main objective of the method is that o...

When a pulsed light beam propagates through ruby, it is delayed by a slow-light mechanism. This mechanism has been the subject of debate (Wisniewski-Barker et al 2013 New J. Phys. 15 083020; Kozlov et al 2014 New J. Phys. 16 038001; Wisniewski-Barker et al 2014 New J. Phys. 16 038002). To distinguish between the two main proposed mechanisms, we investigate the trailing edge of a squarewave puls...

Resolved computation of two dimensional insect hovering shows for the first time that a two dimensional hovering motion can generate enough lift to support a typical insect weight. The computation reveals a two dimensional mechanism of creating a downward dipole jet of counterrotating vortices, which are formed from leading and trailing edge vortices. The vortex dynamics further elucidates the ...

Submit Manuscript | http://medcraveonline.com Abbreviations: c: chord; u∞ : Free Stream Velocity; ν: Kinematic Viscosity; Re: Chord Reynolds number, ( ) / u c n ∞ = ; OGE: Out of the Ground Effect; GE: Ground Effect; Cd: Sectional Drag Coefficient; Cdp: Sectional Pressure Drag Coefficient; Cl: Sectional Lift Coefficient; Cl,max: Maximum Cl; l C α :Lift-Curve Slope; Cm: Sectional Pitching Moment...

This paper concerns a numerical study of employing an adaptive trailing edge flap to control the lift of an airfoil subject to unsteady inflow conditions. The periodically varying inflow is generated by two oscillating airfoils, which are located upstream of the controlled airfoil. To establish the control system, a standard PID controller is implemented in a finite volume based incompressible ...

Unsteady inviscid flow models of wings and airfoils have been developed to study the aerodynamics of natural and man-made flyers. Vortex methods have been extensively applied to reduce the dimensionality of these aerodynamic models, based on the proper estimation of the strength and distribution of the vortices in the wake. In such modelling approaches, one of the most fundamental questions is ...

The problem of potential flow of a second-order fluid around an ellipsoid is solved, following general expressions in Lamb (1993), and the flow and stress fields are computed. The flow fields are determined by the harmonic potential but the stress fields depend on viscosity and the parameters of the second-order fluid. The stress fields on the surface of a tri-axial ellipsoid depend strongly on...

Submit Manuscript | http://medcraveonline.com Abbreviations: c: chord; u∞ : Free Stream Velocity; ν: Kinematic Viscosity; Re: Chord Reynolds number, ( ) / u c n ∞ = ; OGE: Out of the Ground Effect; GE: Ground Effect; Cd: Sectional Drag Coefficient; Cdp: Sectional Pressure Drag Coefficient; Cl: Sectional Lift Coefficient; Cl,max: Maximum Cl; l C α :Lift-Curve Slope; Cm: Sectional Pitching Moment...

Direct numerical simulations were performed to study the effect of an elastically mounted trailing edge actuator on the unsteady flow over a plunging, thin airfoil at Reynolds number of 14700 based on the chord length. The goal is to investigate potential benefits of flow-induced passive actuation of the trailing edge to the lift and drag characteristics of flapping MAV wings. The trailing edge...