Turbulent Flows over Complex Boundaries: Applications in Engineering and Environmental Fluid Mechanics William Anderson Mechanical Engineering Department and Center for Astrophysics, Space Physics, and Engineering Research, Baylor University, Waco, Texas
Abstract: A moving fluid responds to the presence of a solid, fixed boundary with a velocity field that tends to zero as the boundary is approached. When the spatial velocity gradient associated with this response is adequately high, instabilities emerge in the flow, eventually leading to a chaotic turbulent flow field. These turbulent wall bounded flows are ubiquitous in nature and are of critical importance, for example, to the performance of airfoils or dispersion of air pollutants in urban environments. The speaker studies these flows numerically with large-eddy simulation, and collaborates with experimentalists for validation. The speaker will first present results of flow over complex aeolian sand dunes from the White Sands National Monument. In this research, results showed that the bulk characteristics of flow in the dune field closely resemble a turbulent mixing layer, not a boundary layer. This is important since momentum transported by turbulent winds incrementally erode the dunes. More recently, the speaker has been working to understand the presence of mean flow heterogeneities in flows over complex, multiscale (fractal-like) topographies. Using controlled cases and LES, it is thought that these mean flow heterogeneities (i.e. mean streamwise vorticity) constitute Prandtl’s secondary flow of the second kind, and we are using budgets of vorticity production and turbulence kinetic energy to explain such flow heterogeneities. The talk with conclude with studies of atmospheric flow over urban environments and evaluation of interactions between turbulent structures in the ``outer’’ regions of the flow and dynamics of flow in close proximity to the urban obstacles.
Bio: Anderson received his PhD in Mechanical Engineering from The Johns Hopkins University in July, 2011. He began as a tenure-track faculty in the Mechanical Engineering Department at Baylor University in August, 2011. His interests focus on the dynamics of turbulent flows responding to complex bounding geometries. Research activities are funded by the Army Research Office, Shell Exploration and Production Company, and Air Force Office of Scientific Research.