Spotlight on a Student: Morgan Li

Experimental study of a turbulent boundary layer over surfaces with spatially varying roughness


Morgan Li is a PhD candidate in Mechanical Engineering at the University of Melbourne, researching how a turbulent boundary layer evolves when the surface condition varies from rough to smooth.

She plans to submit her thesis in February 2020, after which she will join the physics of fluids group in the University of Twente in the Netherlands as a postdoctoral researcher.

What is your research about?

My PhD project is focused on the experimental study of how a turbulent boundary layer evolves when the surface condition varies from rough to smooth. The overall aim is to simulate flows over more complicated heterogeneous roughness that profoundly influence our daily life. For instance, the landscape transitioning from dense urban to open rural areas or from a forest to a prairie can affect the meteorological observations and weather predictions; localised patches of bio-fouling on a ship’s hull or rivets on an aircraft can change the skin friction, which constitutes a large proportion of the overall drag and fuel consumption of the vehicle.

Although the streamwise rough-to-smooth heterogeneity has been studied over the past few decades, to date, the recovery of a turbulent boundary layer following such a transition is still not fully understood. For example, determining the local wall-shear stress after the rough-to-smooth transition has been hampered by the issue of data repeatability, and there is a large scatter of wall-shear stress recovery trends in the literature. Therefore, my PhD aims at systematically investigating the flow recovery downstream of the rough-to-smooth transition to settle the dispute on the inconsistent data available in the literature. The experiments are carried out in the High Reynolds Number Boundary Layer Wind Tunnel in the University of Melbourne. In addition, we incorporate these experimental observations into a theoretical model to predict the flow evolution with given upstream conditions.

In engineering applications, the theoretical model considering the heterogeneity of surface roughness can be a more realistic alternative to the assumption of homogeneous roughness commonly used in the overall drag prediction of a bio-fouled ship hull in shipping industry. With refined calculations, a stronger economic case can be made to ship operators, leading to more informed and efficient ship operations (well-designed cleaning schedules etc.).

Who are your supervisors?

My supervisors are Prof. Nicholas Hutchins and Prof. Ivan Marusic, both within the Department of Mechanical Engineering at the University of Melbourne, and Dr. Charitha de Silva from the University of New South Wales, who until very recently was a research fellow in the same department. They are world-renowned scientists pioneering many concepts in the field of fluid dynamics. I am grateful for their deep insight in turbulent flows and their valuable guidance in my PhD journey.

What do you want to do next?

After completing my PhD, I plan to investigate multiphase flows using advanced experimental techniques as a postdoctoral researcher in the Netherlands.


I received Melbourne International Research Scholarship (MIRS), Melbourne International Fee Remission Scholarship (MIFRS) as well as MSE Conference Travel Scholarship.----

Morgan and her supervisors welcome any enquiries about her research. You can email her at:

Morgan spoke at the MEI Symposium on 13 December, which showcased the University of Melbourne’s multi-disciplinary energy research. Read about the symposium.

More Information

Ruby Brown

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