Thesis
Experimental and numerical analysis of a falling plate
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2022
- Thesis identifier
- T16440
- Person Identifier (Local)
- 201659762
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The study of the motion of solids in fluids has always triggered interest in the scientific and research communities. This rich, dynamic behaviour dates back to the foundations of modern mechanics. However, understanding the dynamic behaviour of falling or rising objects in a viscous fluid under the effects of gravity, buoyancy, and the hydrodynamic/aerodynamic force in the fluid has long been a major issue in both the engineering and scientific communities. This research is subdivided into three categories: firstly, an experimental investigation of heavy plates freely falling in three-dimensional (3D) space by determining the transition between zigzag and tumbling. Secondly, the determination of numerical uncertainty and, finally, investigating the dynamics of a free-falling plate with initial speeds. In the first part, the free-falling of heavy plates both in air and water was investigated experimentally to determine the transition from zigzag to tumbling motions with different ranges of Re and I∗, a state-of-the-art technique is used to reduce the errors and inaccuracies during measurements, where the motion of the falling trajectories is calculated in 3D space using Qualisys. The 3D falling kinematics of the rectangular plate during descent were quantified by tracking the real-time centre of mass on the body during descent and measuring trajectories, speed, and azimuthal rotation. In the same way, the mapping of heavy plates was expanded to learn more about how they fall with bistability. It was concluded that the motion is similar to the three-dimensional dynamics of freely-falling bubbles with erratically wobbling behaviour and zigzag motion, but the motion changes with different oscillations of both vertical and horizontal velocity depending on the initial angle of release, but the vertical velocity is stochastic and does not depend on the initial release angle. As the Re increases, the frequency and pattern of oscillation increase with a decrease in aspect ratio and a high lift compared to previous literature. The second part investigated the tumbling motion of a freely falling plate numerically, where the measured trajectory and forces were validated using both the experimental and numerical data available in previous literature. Using the grid convergence index method, the numerical uncertainty of the plate in free fall is calculated at each point during the free fall. The numerical results adopted in this study provided realistic results of tumbling plate dynamics and correctly predicted the trajectories, forces, and torque but with phase shifts. The third part investigates the dynamic motion of a tumbling plate with different initial speeds. All previous experimental and computational investigations of freely falling plates, such as the influence of aspect ratio, density ratio, turbulence, Reynolds number, or the aerodynamics of multiple free-falling plates, and shape optimization, were carried out. The freely falling plate with initial speed was never explored. In the last part, the effect of initial speed on the tumbling motion of the body under the influence of gravity, including the falling paths, speeds, and forces, was studied numerically for the first time. Thus, it was observed that trajectories move to the left or right with different initial speeds, but the movement is stochastic and not dependent on initial speed. It was also observed that the measured horizontal velocity is different as the oscillation moves to the left or right with the same vertical velocity. The phase movement to the left looks similar to the double period motion in previous literature, while the phase movement to the right is a single periodic tumbling. Furthermore, a new triple period oscillation was observed and reported for the first time with a high frequency and low decent angle, horizontal, and vertical velocities.
- Advisor / supervisor
- Yuan, Zhiming
- Jia, Laibing
- Resource Type
- DOI
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PDF of thesis T16440 | 2022-12-13 | Public | Download |