Thesis Format
Monograph
Degree
Master of Engineering Science
Program
Mechanical and Materials Engineering
Supervisor
Dr. Remus Tutunea-Fatan
2nd Supervisor
Dr. Evgueni Bordatchev
Co-Supervisor
Abstract
Drag reductive functional surfaces can reduce the environmental impact and operational costs, and improve the performance of equipment in various industries. These motivations lead to the increasing demand for scientific understanding of the mechanism behind drag reduction and engineering developing the manufacturing, modeling, and testing of the surfaces. CFD simulations were used to analyze the turbulent flow surrounding the riblets (protrusions defining the surface) using unique variables. Pressure differential experiments were used for validation of the drag reduction results. It was shown both computationally and experimentally that a maximum of roughly 10% drag reduction is possible using streamwise triangular riblets and the non-dimensional riblet spacing that this occurs at is proportional to the included angle. Additionally, groundwork for a new experimental Taylor-Couette system was done including design, fabrication, and testing. The groundwork for this experiment will successfully allow future studies to easily evaluate the drag reductive properties of various surfaces.
Summary for Lay Audience
With a global call for a reduction in greenhouse gas emissions, there is an increasing demand for scientific advancements for methods of reducing fossil fuel consumption in various industries. One method of this is reducing the friction drag on a surface moving through a fluid. It has been shown that surfaces with microscopic protrusions (called riblets) can reduce 10% of the friction drag. The riblets studied in this research are known as streamwise triangular riblets and are triangular grooves parallel to the main flow direction. This research aimed to use fluid simulations to gain a better understanding of the patterns in the turbulent flow associated with drag reduction. Furthermore, as simulations are only designed to model the real world and are imperfect, experimental validation is required to make conclusive observations. This was done using a modified experiment that was previously designed and used by Dr. Benjamin Hamilton which took measurements using a pressure sensor. The results from these simulations and experiments aligned well with the current scientific understanding of the surfaces.
It was noticed that a new experiment designed to be quick and simple when taking measurements would benefit future studies. This new experiment had to provide accurate and repeatable results over a wide range of velocities. It was determined that a rotational device would suit this need well. Specifically, a modified rheometer would be the best option as it includes a built-in motor, high-precision sensors, and a software which allows easy control of the system. This system can produce Taylor-Couette flow, a flow condition created between two cylinders, one rotating and one stationary. It was found that the surfaces in these experiments exhibit drag reduction for a larger window of velocities compared to the previously examined linear flow experiments, while reaching a maximum of around 10% (these results varied between riblet geometries). Furthermore, at high velocities, it was found that air became incorporated into the water and caused a significant increase in drag reduction, which is theoretically caused by air bubbles becoming trapped in the riblets and acting as a lubricant between the surface and the water.
Recommended Citation
Gordon, William B., "Design, Fabrication, and Performance Evaluation of Drag Reductive Functional Surfaces with Streamwise Triangular Riblets" (2025). Electronic Thesis and Dissertation Repository. 10738.
https://ir.lib.uwo.ca/etd/10738
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