Wall pressure events in turbulent wall-bounded flow

The wall pressure field from a direct numerical simulation of turbulent channel flow was used for the analysis of significant pressure events in space and time. Both positive and negative wall pressure events in the database were detected using a pressure peak conditional sampling technique. The recovered events were ensemble averaged to provide a space and time record of a typical event. Both positive and negative pressure peak events have regions of pressure of the opposite sign just ahead of and behind them, but the regions of opposite sign do not extend to the sides of the events. Although a positive pressure peak event begins as a double positive pressure hump, the downstream hump eventually dominates and becomes the pressure peak before the event decays. Negative pressure peak events begin as a positive hump leading a negative hump. The negative hump grows to become the peak before decaying. For both positive and negative events, the event begins about 400 wall units upstream of where the maximum pressure occurs and persists to about 400 wall units downstream of the pressure peak. The entire event lasts about 0.4 δ/U_τ.