Velocity Field around a Rigid Flapping Wing with a Winglet in Quiescent Water

This study investigated the effect of a winglet on the velocity field around a rigid flapping wing. Two-dimensional particle image velocimetry was used to capture the velocity field of asymmetric one-degree-of-freedom flapping motion. A comparison was conducted between wings with and without a winglet at two flapping frequencies, namely 1.5 and 2.0 Hz. The effect of the winglet on the velocity field was determined by systematically comparing the velocity fields for several wing phase angles during the downstroke and upstroke. The presence of a winglet considerably affected the flow field around the wingtip, residual flow, and added mass interaction. The added mass was lower and residual flow was weaker for the wings with a winglet than for the wings without a winglet. The added mass and velocity magnitudes of the flow field increased proportionally with the flapping frequency

Evolution of Vortex Structures Generated by a Rigid Flapping Wing with a Winglet in Quiescent Water

This study aims to the utilization of vortex structures generated through wing flapping for achieving sustainable flight, and the motivation is elicited by the phenomenon observed in natural flyers. The vortex structures in the flow field generated by a flapping rigid wing are captured using vorticity and the LAMDA2 criterion. The study investigates a comparative analysis between a wing both with and without a winglet. Moreover, the influence of flapping frequency is examined as well. For the experiments, particle image velocimetry (PIV) measurements are employed for the flow field around mechanical flapping motion in a quiescent water condition. The flapping mechanism has one-degree freedom, showing a 1:3 ratio in motion, and tested wings at 1.5 and 2.0 Hz. A “modified” vortex filamentation and fragmentation phenomenon is proposed as a significant finding in the present study, based on a comprehensive analysis of the flow field around the wing with a winglet

Velocity field around a rigid wing in mechanical main flapping motion

The natural flyers flap there wings for its flight. When the wings flap, flow field around the wings would be reoriented and flyers make use of it to sustain its flight. In the present study, particle image velocimetry measurements are used to capture the flow field around the rigid wings attached to a mechanical main flapping mechanism. The experiments are conducted for a kinematic asymmetry flapping of the wing with aspect ratio 1.0 and flapping frequency of 2.0 Hz in quiescent water medium. The dimensions of the wing are 40mm in chord, 40mm in span and thickness of 1.5mm. The Reynolds number is of the order of 104. The results revealed the formation of wingtip vortices, flow along the span, added mass and residual flow

A feasibility study of solar ponds for electricity generation at Yuma Proving Grounds, Arizona

Abstract not availabl

VELOCITY FIELD AROUND A RIGID WING IN MECHANICAL MAIN FLAPPING MOTION

International audienceThe natural flyers flap there wings for its flight. When the wings flap, flow field around the wings would be reoriented and flyers make use of it to sustain its flight. In the present study, particle image velocimetry measurements are used to capture the flow field around the rigid wings attached to a mechanical main flapping mechanism. The experiments are conducted for a kinematic asymmetry flapping of the wing with aspect ratio 1.0 and flapping frequency of 2.0 Hz in quiescent water medium. The dimensions of the wing are 40mm in chord, 40mm in span and thickness of 1.5mm. The Reynolds number is of the order of 10^4. The results revealed the formation of wingtip vortices, flow along the span, added mass and residual flow

Effect of marginal variation of aspect ratio and frequency with kinematic asymmetry on flow field around flapping rigid wing in hover

Phase-locked two dimensional particle image velocimetry (PIV) measurements are used to capture flow field around rigid flat plate wings undergoing main flapping motion (hover) with water as fluid medium in quiescent condition. Experiments are conducted using asymmetric upper-lower stroke single degree of freedom main flapping motion. Two different aspect ratio (AR) 1.5 and 1.0 rectangular wings at 1.5 Hz and 2.0 Hz flapping frequency and chord based Reynolds number of the order of 104 are studied. To achieve the desired aspect ratio, wing span is varied while wing chord remains fixed. Flow features for downstroke and upstroke are comparable for all four cases investigated. This includes vortex shedding from wingtip during wing stroke, vorticity intensification caused due to vortex stretching which occurs more dominantly for AR = 1.0, occurrence of KH instability in shear layer formed due to wing sweep and added mass effect due to the flow dragged by flapping wing. Vortex filamentation and fragmentation phenomena are observed during downstroke and upstroke respectively due to faster downstroke and slower upstroke. Rossby number, which is the ratio of inertial to Coriolis force is significant for rotational flapping wing. With increase in Rossby number there is a reduction in the spanwise flow over wing which influences strength of wingtip vortex at beginning of a stroke. It is found that spanwise flow for AR = 1.5 is stronger than AR = 1.0 and consequently the strength of wingtip vortex is higher for higher aspect ratio. However, peak vorticity is higher for AR = 1.0 due to vortex stretching effect which is expected to be more dominant at lower AR due to three dimensional effects. Effect of marginal variation in wing aspect ratio, flapping frequency with kinematic asymmetry are studied using velocity field, vorticity (ωz) contours, λ2 criterion, peak vorticity variation and its spatial distribution as well as kinetic energy variation of the flow field. Kinetic energy distribution and its connection with wake capture is explored