Numerical methods and software for computational fluid dynamics (CFD), nek5000

Paul Fischer, University of Illinois at Urbana-Champaign

Usage Details

Turbulent transport is the principal driver for many processes in physics, engineering, geosciences, and biology. Examples include the in-fall of matter into black holes, combustion in automotive and aerospace applications, sediment and pollutant transport in rivers and oceans, and atherogenesis in arterial blood flow. Our objective is to address these questions through direct numerical and large-eddy simulation of turbulent flow by solving the governing Navier-Stokes and associated transport equations. Current simulations within our group are addressing a variety of questions relating to turbulent transport in engineering sciences.

The first project is analyzing mechanisms for sediment transport in bifurcating rivers. Experimental evidence indicates that a disproportionate amount of near-bed sediment is directed into side channels when streams bifurcate, which ultimately alters the flow dynamics and leads to potential blockage of the side channel. Investigations into this effect date back almost a century, but the dynamics of the process have yet to be clearly identified.

A second project is looking at heat transfer enhancement in cooling passages by using wire coil inserts. Experiments and simulations have indicated that up to a four-fold increase in the heat transfer coefficient for optimally-sized inserts. Our objective is to understand the fundamental enhancement mechanisms in order to aid in the design process and to predict off-design behavior.

We are also investigating compressible multiphase turbulence for a variety of applications in turbine and internal-combustion engines. This work entails significant development efforts in Nek5000 and we do not anticipate many full production runs on Blue Waters for this project until the end of the year.

Free-surface turbulence is another question of interest. One of the applications is in the sediment transport case described above. Near-bed sediment transport is driven by secondary flows that are governed by far-field pressure gradients. The pressure distribution for open channels differs significantly from closed channels, so support for free-surface turbulence is of primary importance.