Title：Wall-normal pressure gradient over the bottom of a turbulent open-channel flow

Reporter：Prof.B. Mutlu Sumer

Time：2025.11.24（Friday）14:30-16:30

Venue：G2-101, Guangzhou International Campus, South China University of Technology

Abstract：

Professor Sumer will present an experimental study on the wall-normal pressure gradient in a turbulent open-channel flow with a smooth bottom. Using neutrally-buoyant particles and analyzing their accelerations, the conditional-averaged pressure gradient (both upward and downward) was determined as a function of depth. The results show a radical difference from the mean-pressure gradient obtained from the Reynolds equation. The conditionally-averaged pressure gradient, upward or downward, reaches very large values near the wall in the range O(5)<y+<O(100), the range which practically coincides with the near-wall region where fluid ejections originate in the turbulent bursting process. Additionally, the instantaneous pressure gradient can be twice the mean values. These findings potentially explain the vigorous, impulsive suction of low-speed fluid observed during ejection events near the wall.

Resume:

B. Mutlu Sumer, a Turkish scholar, was a Professor at the Technical University of Denmark until his retirement in 2015, later holding the title of Professor Emeritus. He earned his PhD from Istanbul Technical University (ITU) and was a postdoctoral fellow at the University of Cambridge. His research focuses on flow around marine structures, scour, sediment transport, and turbulence. He is the author of several influential books and has received awards including the Karl Emil Hilgard Hydraulic Prize from ASCE.