| Author: | Huang, Guangyuan |
| Title: | Aeroacoustics of a D-shaped generic vehicle profile |
| Advisors: | Leung, C. K. Randolph (ME) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Motor vehicles -- Aerodynamics Ground-effect machines Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | 182 pages : color illustrations |
| Language: | English |
| Abstract: | Driven by tightened environmental legislative requirements and increasing consumer demand for quiet road vehicles, research on the aeroacoustics of road vehicles has recently received immense attention in both the automotive industry and the academic community. For road vehicle aerodynamics, ground proximity is one of the most fundamental features which plays an important role in automotive aerodynamics. In this thesis, the aeroacoustics of a D-shaped generic vehicle profile concerning the ground effect is investigated by both experimental and numerical methods. The D-shaped body, which is a popular generic vehicle model in automotive aerodynamic research, consists of a rectangular cylinder with a rounded head. Firstly, the aerodynamics of the D-shaped body in free space and proximity to a stationary ground is investigated experimentally in a low-speed wind tunnel. The gap-to-height ratio is G/H = 0.2 and the Reynolds number is ReH = 23000 based on the body height. Particle Image Velocimetry (PIV), how-wire velocimetry, and surface oil-flow visualization are employed in the measurements. Proper orthogonal decomposition is performed to examine the wake modes. Secondly, the aeroacoustics of the D-shaped body in free space is investigated by Direct Aeroacosutric Simulation (DAS) in two dimensions using an in-house solver based on the Conservational Element and Solution Element (CE/SE) method. The Reynolds number and the Mach number are ReH = 23000 and Ma = 0.2 respectively. The numerical method is carefully validated against the experimental results. Thirdly, the aeroacoustics of the D-shaped body near a stationary ground is investigated by DAS in both three and two dimensions using a commercial solver of ANSYS Fluent. The gap-to-height ratio is G/H = 0.2. The Reynolds number and the Mach number are ReH = 23000 and Ma = 0.2 respectively. The three-dimensional calculation shows good agreement with the experiment results. The capacity of the two-dimensional calculation for capturing the dominant flow and acoustic features is evaluated. Finally, the aeroacoustics of the D-shaped body near a moving ground is investigated by DAS in two dimensions using the CE/SE solver. The gap-to-height ratio is G/H = 0.2. The Reynolds number and the Mach number are ReH = 23000 and Ma = 0.2 respectively. The results are compared against those from the free-space calculation. Concerning the key engineering requirement for quieter vehicles, as well as the fundamental interests in bluff body aeroacoustics, the present work has made three major contributions: i. clarified the mechanism of sound generated from flow around a D-shaped bluff body in ground proximity and revealed the ground effect on the sound sources, propagating paths, and far-field features, filling the research gap in aeroacoustics of a bluff body concerning ground proximity; ii. confirmed the existence of self-sustained oscillations in the flow around an elongated bluff cylinder at a sub-critical Reynolds number and revealed the mechanism of the influence of the acoustic perturbations, extending the research into the sub-critical Reynolds number regime and the boundary condition with ground proximity; iii. revealed multiple wake modes of the D-shaped body flow and clarified the generation mechanism of the low-frequency oscillations in the wake, giving insight into the research of low-frequency oscillations in the bluff body flows. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/12093