Experimental study on a plate freely falling in quiescent water

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Experimental study on a plate freely falling in quiescent water

 

Author: Gao, Han
Title: Experimental study on a plate freely falling in quiescent water
Degree: M.Sc.
Year: 2016
Subject: Unsteady flow (Aerodynamics)
Hong Kong Polytechnic University -- Dissertations
Fluids.
Department: Faculty of Engineering
Pages: xi, 80 pages : illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2917024
URI: http://theses.lib.polyu.edu.hk/handle/200/8599
Abstract: The descent motion of freely falling objects is generally complex, even for regularly shaped objects such as homogeneous cards. Although the problem has attracted attention for ages, it is only recently that the tremendous progress in the development of experimental and computational techniques and the emergence of new theoretical concepts have led to a better understanding of the underlying physical mechanisms. The trajectories of solid objects like feather, leaf and business card can be predicted if aerodynamic forces are known. According to Ern (2011), normally falling regimes of a two-dimensional homogeneous plate include fluttering motion, transitional motion and tumbling motion, similar to the findings of Field et al. (1997) and Luke Heisinger et al. (2014) with thin disks. The main purpose of the dissertation is to build up experimental apparatus, and to study freely falling plates falling in quiescent water. Three motion regimes of a freely falling plate with aspect ratio ranging from 2 to 8 were studied. The plate was released in quiescent water in a water tank of 600 mm x600 mm x600 mm, and its trajectories were recorded using a high-speed camera. Then images of trajectories proceeded using MATLAB. Instantaneous and average kinematic parameters, including midpoint trajectories and descent angle variation, were analyzed. It is found that the trajectories match with previous results published by Smith (1971). The vortices of fluttering and transitional motions were successfully visualized and analyzed using fluorescent dye.

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