GALCIT Colloquium

Turbulent flows over roughness are ubiquitous in engineering and geophysical applications, where the rough surface typically increases momentum and heat transfer. However, accurately predicting these effects is often exceedingly expensive, as it requires carefully controlled and calibrated laboratory experiments or conventional direct numerical simulations (DNS). This makes design predictions and the examination of rough-wall flows challenging for both industry and academic research. In this talk, I outline a framework termed the minimal channel in which fully resolved numerical simulations of rough-wall turbulent flows can be conducted at a much reduced cost compared to conventional DNS. The minimal channel is used to simulate turbulent flow over a variety of roughness geometries that would otherwise be prohibitively expensive to study.  In particular, we are able to investigate roughness configurations in which the elements are tightly packed together, the so-called dense regime of roughness, which yields a substantially different flow compared to sparsely packed roughness elements.  I will also demonstrate that the minimal channel technique can be applied to forced convection turbulent flows, in order to understand how roughness alters heat transfer.