GALCIT Colloquium

Many beautiful theoretical predictions about turbulence have been made in the limit of Infinite Reynolds numbers. However, no real application operates at infinite Reynolds number, and it is often not clear when the Reynolds number is high enough, or how low Reynolds numbers affect the flow dynamics. What makes turbulent flows particularly challenging—theoretically, numerically and experimentally—is the large range of spatial and temporal scales contained within them, with the smallest eddies typically many orders of magnitude smaller than the largest eddies. Here, we are pushing the boundaries for what can be tested in a laboratory setting, including full Reynolds number wind turbine tests and wall-bounded flows at Reynolds numbers not far from what is seen in the atmospheric boundary layer. Not only do these experiments require extreme facilities, but also novel sensing techniques in order to resolve even the finest details of turbulence. These extreme tests allow us to evaluate if and when the flow reaches its infinite Reynolds number behavior, and furthermore, they allow us to study the effect of low Reynolds numbers on the turbulence itself. Equipped with this information we can evaluate existing, and develop new, theoretical approaches to turbulence that better describe realistic flows. The theoretical and experimental tools developed for the velocity field are adopted to give us information about other fields, such as temperature, to yield improved heat transfer predictions in turbulent flows.