Woodruff School of Mechanical Engineering


Turbulent Flow Interactions with Complex Topography: From Permeable Walls to Barchan Dunes.


Prof. Kenneth T. Christensen


University of Notre Dame


Thursday, November 8, 2018 at 11:00:00 AM


MRDC Building, Room 4211


Dr. Devesh Ranjan


This talk will highlight on-going studies of interactions between turbulence and complex topography. The latter is encountered in a multitude of engineering and natural flow scenarios and can lead to significant modifications of the overlying flow as well as unique coupling between the flow and the topography. This talk will focus on two specific flow-topography situations that are often observed in nature: flow overlying a permeable boundary (like a gravel river bed, for example) and flow over barchan dunes - crescent-shaped bedforms that form in aeolian and sub-aqueous environments with a limited sediment supply and relatively unidirectional flow. In the study of permeable boundaries, models were formed from cubic and body-centered arrangements of spheres wherein the surface exposed to the flow was either smooth or rough (the former meaning no spheres protruded into the flow, though the boundary was still permeable). For the barchan-dune work, fixed-bed barchan models were developed to reflect morphologies identified in nature when these dunes come in close proximity. In both cases, the models were fabricated in acrylic and deployed in a refractive-index-matched (RIM) flow facility whose working fluid has the same optical refractive index as the models. The optically-unimpeded access afforded by the RIM methodology, coupled with particle-image velocimetry measurements, provides unique views of the rich flow dynamics associated with both of these turbulence–complex topography interactions.


Kenneth T. Christensen is the Viola D. Hank Professor at the University of Notre Dame, with a joint appointment in the Departments of Aerospace & Mechanical Engineering and Civil & Environmental Engineering & Earth Sciences. He also presently serves as the Department Chair of Aerospace & Mechanical Engineering and as a Provost's Fellow at Notre Dame. He joined the ND faculty after ten-plus years on the faculty at the University of Illinois at Urbana-Champaign. Christensen directs a research group that pursues experimental studies of turbulence, geophysical flows and microfluidics and is a WPI Principal Investigator in the Carbon Dioxide Storage Division of the International Institute for Carbon-Neutral Energy Research (I2CNER) based at Kyushu University in Japan. He is a Fellow of AAAS, APS and ASME, an Associate Fellow of AIAA and has received the AFOSR Young Investigator Award (2006), the NSF CAREER Award (2007), the Francois Frenkiel Award for Fluid Mechanics from APS-DFD (2011) and the Gustus Larson Memorial Award from ASME (2016).


Refreshments will be served.