The aerodynamics of an impulsively-started insect wing PDF
Preview The aerodynamics of an impulsively-started insect wing
Master of Science Thesis The aerodynamics of an impulsively-started insect wing An experimental and numerical investigation F.J. Venneman June 26, 2009 The aerodynamics of an impulsively-started insect wing An experimental and numerical investigation Master of Science Thesis For obtaining the degree of Master of Science in Applied Physics at Delft University of Technology F.J. Venneman June 26, 2009 Faculty of Aerospace Engineering Faculty of Applied Sciences · Delft University of Technology Copyright c Aerospace Engineering & Applied Physics, Delft University of Technology (cid:13) All rights reserved. DELFT UNIVERSITY OF TECHNOLOGY DEPARTMENT OF AERODYNAMICS & APPLIED PHYSICS The undersigned hereby certify that they have read and recommend to the Faculty of Ap- pliedSciences foracceptance thethesis entitled “The aerodynamics of an impulsively- started insect wing”byF.J. Vennemaninfulfillment oftherequirementsforthedegree of Master of Science. Dated: June 26, 2009 Supervisors: Prof.dr. R.F. Mudde Dr.eng. L.M. Portela Dr.ir. M. Tummers Prof.dr.ir.drs. H. Bijl Dr.ir. B.W. van Oudheusden Preface Inthe process of choosing a subject formy graduationproject Iknew for sure thatI wanted something that I was really passionate for. I also wanted to do something that I could basically explain on a birthday party. Many fields of applied physics seemed attractive, so it was a hard choice. Until a morning in the summer of 2008, under the shower, I realized I had to study the fluid dynamics of insects or birds. Flight of insects and specifically birds has astonished me for years and fluid dynamics has always been the part of physics that I felt most confident with. So I went ’shopping’ at various research groups (Multi-Scale Physics, the Laboratory for Aero & Hydrodynamics and the Aerodynamics group) and ended in the position that they all were part of my graduation project. At the start it was difficult to get a grip of the Aerodynamics vocabulary, but once used to it, you realize all the terms relate to basic physical transport phenomena. Besides the language, the challenge of graduation for me was to keep focused on the insects while debugging my corrupt scripts. Luckily once in a month a bug landed on one of my screens to tell me that he/she was the subject of my graduation. I would like to end this preface with some words of gratitude. First of all my girlfriend, Saskia, for understanding when I was in a ’dip’ and infinite support. Then I would like to thank, Christian Poelma for providing his piv data, Frank Bos for helping me out when I got segmentation errors, Bas van Oudheusden for advice and reading my report over and over again, Rob Mudde for coaching me through my graduation project and of course Hester Bijl for her enthusiasm and keeping me on schedule. Freek Venneman Delft, June 15, 2009 MSc. Thesis F.J.Venneman vi Preface F.J.Venneman MSc. Thesis Abstract The design of Micro Air Vehicles (mavs) is currently an area of rapid growth. To improve mavs, a better understanding of bird and insect aerodynamics is very helpful. In this study the time-dependent three-dimensional flow around an impulsively-started fruit-fly wing is investigated at a Reynolds number of 256 and a constant angle of attack (α = 50◦). Both the forces on the wing and the flow-field structure are studied from an experimental and a computational point of view. On the experimental part, the work presented in this thesis is a first application of a new tool to determine fluid dynamic forces in three dimensions. Experimentally obtained velocity-fields around a dynamically-scaled robotic wing, with the previously mentioned kinematics, are provided for the purpose of this study. Pressure-fields are deduced from these velocity-fields, by means of a new tool, called the planar Poisson approach. The forces on the wing are obtained by the momentum approach, using both the velocity and the pressure-fields. These forces are in good agreement with the forces that were directly measured by a sensor mounted on the robotic wing. Excellent agreement is found in the steady part of the stroke, where the relative difference with the measurements is within 13%. For the computational element of this study, the Navier-Stokes equations around the insect wing are solved using OpenFOAM as a framework. The incompressible flow is solved on a dynamically moving mesh, which deforms based on Radial Basis Function interpolation, which is a new mesh deformation tool. The forces obtained from the computations are also in good agreement with the measurements, in the steady part of the stroke, the relative difference with the measurements in the steady part of the stroke is within 22%. MSc. Thesis F.J.Venneman
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