Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150109

150109 - Blade-Vortex Interaction on a Twisting Flat Plate 

Abstract:

Vortex dynamics during parallel blade-vortex interaction (BVI) of a tandem-wing configuration are studied in a towing tank using planar particle image velocimetry (PIV) and force sensor data. Vortices are generated by applying a rapid pitching motion to a leading rigid flat plate. The generated vortices collide with a trailing flat plate undergoing dynamic twisting. The interaction between the vortex and leading edge, the interaction between the vortex and the boundary layer, and the subsequent evolution of the vortex over the surface of the trailing plate are investigated for varying twisting kinematics. Vortex trajectory and strength are obtained from PIV data. The results are used to study the mechanisms of vortex decay and the effects of key parameters on vortex dynamics. The subsequent effects on the hydrodynamic forces experienced by the trailing plate are studied by analyzing force sensor data in conjunction with PIV results.

 

Introduction:

The development of Micro-Air Vehicles (MAVs) has become a topic of interest for their potential uses in unsteady and unpredictable aerial conditions commonly encountered in civilian and military operations. MAVs typically fly at low altitude and low speed in order to maneuver in the obstacle-dense environments they are deployed in. As a result, they are routinely subject to sudden flow disturbances (i.e. gusts) that are inherent in these environments. Interestingly, many small flying animals of similar size demonstrate proficiency in navigating these similar conditions. Natural flyers employ various mechanisms, often simultaneously, to mitigate the effects of wind gusts of varying intensity and frequency. Revealing these mechanisms is of particular importance to the development of highly maneuverable, stable MAVs.

 

Methodology:

Two flat plates are used to perform the experiments in this study. The first flat plate, referred to as the generator wing, is used to generate a vortical gust. The second flat plate, referred to as the morphing wing, is impacted by the vortical gust and is the object of this study.The two plates are oriented in a tandem-wing configuration with the generator wing leading, and the morphing wing following. Experiments are conducted in a 6×1×1.5 m water tank at the University of Central Florida’s Experimental Fluid Mechanics Laboratory. The tank is equipped with a linear traverse to perform towing movements along the length of the tank. A an aluminum frame is affixed to the traverse to provide mounting locations for additional motors, sensors, and the flat plates. A transparent acrylic skim plate is attached just above the root the plates to suppress the formation of surface waves.

Preliminary "vortex generation" experiments were conducted in order to optimize the pitching motion of the generator wing, and to characterize the generated vortex. First, dye flow visualization was performed to qualitatively select an initial set of pitching parameters. Next, planar Particle Image Velocimetry (PIV) was performed to determine the trajectory, size, and strength of the generated columnar vortices. The researchers selected for a vortex column that maintained coherency for the longest time, and showed the least variation in spanwise strength distribution. Based on these criteria, the generator wing is set to pitch from 0deg to 30deg in one second.

Presenting Author: Carlos Soto University of Central Florida

Presenting Author Biography: Carlos Soto is an Aerospace Engineering PhD student at the University of Central Florida's Experimental Fluid Mechanics Laboratory. His research thus far has been focused on unsteady fluid mechanics, vortex dynamics, and flow control; particularly in the context of flexible and actively morphing wings. His work is heavily bio-inspired, drawing upon the effortless acrobatics of natural flyers and swimmers.

Authors:

Carlos Soto University of Central Florida
Samik Bhattacharya University of Central Florida