Turbulent boundary layers developing over rough surfaces

Project description

The majority of laboratory studies of turbulent boundary layers are performed over smooth surfaces. However, for most engineering applications (where Reynolds numbers are typically very large), the aero/hydrodynamic surface tends to be rough to some extent. For example, to be dynamically smooth the fuselage of a large commercial aircraft must be free of imperfections to less than 10 microns, with similarly stringent requirements for large ships. In both systems, it is unlikely that these requirements are adequately met, in which case we pay an additional drag (and hence fuel and emissions) penalty due to these surface imperfections. For aircraft the build-up of roughness between exterior cleaning cycles can result in increases in drag, that add significantly to the overall operating cost. For ships, where biofouling is an ever-present problem, the surfaces are often very rough, with reported increases in drag as large as 70%. Rough wall boundary layers are also important beyond such engineering systems. The first few hundred meters of the Earth's atmosphere is also a turbulent boundary layer, again developed over a surface with varying degrees of roughness.

The aim of this project is to study the evolving turbulent boundary layer over a rough surface. Various types of roughness will be tested, including the replication of real engineering roughness / fouling for accurate testing in laboratory wind / water tunnel facilities.  The novelty of this work lies in the Reynolds numbers that we are able to attain within unique facilities at the University of Melbourne, and also the high resolution measurement systems that we use to probe these flows. This work is complimented by computational simulations of turbulent flows through roughened pipes. It is intended that a simultaneous component of this project will involve the collation and analysis of the vast wealth of existing data on this subject.

PhD students are sought for this project

Project team

Leader: Nicholas Hutchins

Staff: Jason Monty, Daniel Chung, Andrew Ooi

Students: Leon Chan, Michael McDonald

Collaborators: Mike Schultz (US Naval Academy), Andrew Scardino (DSTO)

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