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Stationary and oscillatory flow through coarse porous media

Measurements in a U-tube tunnel were carried out to study flow through coarse granular material. Tests with stationary flow and tests with oscillatory flow were done to study the differences between both. The coefficients from the extended Forchheimer equation, which is supposed to describe non-stationary porous flow, were determined. It appeared that for oscillatory flow the turbulent resistance is larger than under stationary flow conditions. This additional resistance is depending on the flow-field, expressed by the Keulegan-Carpenter number. The contribution of the inertial resistance is depending on the flow field as well. Its contribution to the total resistance was rather limited. The influence of the non-stationary flow conditions have been implemented in the expressions for the turbulent resistance and the inertial resistance. Comparisons of the results from the stationary flow tests with other measurements show that the results correspond reasonably well. This is not the case for existing expressions for stationary flow. The existing formulae under-predict the a-values while they over-predict the b-values. Further research must be concentrated on the influence of parameters such as grading, the aspect ratio and shape. These dependencies can be determined under stationary flow conditions.