Effects of impulsive change in pressure gradient in a two-dimensional turbulent channel flow have been experimentally investigated. The rapid change of pressure was obtained by passage through a contracted region. Wall shear stress, mean velocity profile and turbulence intensity measurements following the removal of rapid pressure change were performed using a Preston tube and a hot-wire anemometer. In the near-wall region, an equilibrium state was achieved quickly and the universal law of the wall was maintained, except quite close to the contracted region. On the other hand, the flow in the core region was significantly perturbed and the return of the flow to an equilibrium state was not achieved, even at a downstream distance of 30 channel heights.
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