Exploring Surface Pressure Fluctuations in DNS of Turbulent Channel Flow*

The pressure distribution generated by a turbulent boundary layer over a flat wall exhibits extreme localized variations in both space and time.  A physical interpretation of the relationship between such wall-pressure fluctuations and coherent velocity structures found in boundary layers is presented here, using direct numerical simulation (DNS) of a turbulent channel flow at Re_τ = 300. A visual inspection suggests that the variations in wall pressure may be isotropic. However, a closer examination using spatial and temporal correlations reveals the existence of distinct "pressure structures" in both the streamwise and spanwise directions. It is reasonable to expect that these pressure structures are closely related to the dynamics of wall-bounded turbulent flows, including the well-documented bursting events in the near-wall region. The dominant spatial and temporal frequencies that describe the evolution of wall-pressure distribution and their link to coherent velocity structures are examined using a highly time-resolved DNS database. Understanding the underlying causal link can benefit various practical applications such as noise suppression, sensor array design, and improving fluid transport efficiency in pipes.