Experimental Investigation on Nonlinear Analysis of Unsteady Flow Through Coarse Porous Media

An experimental investigation of water flowing through coarse porous media in an open channel with free surface was conducted to better understand the mechanism of energy loss and changes with flow velocity. In this research، experimentally، investigate water flowing through coarse porous media in nonlinear unsteady state. To cast light on the analytical characteristics of unsteady-turbulent flow within coastal rockfill structures، an extensive research program has been carried out using the open channel flow principles. Crushed coarse aggregates with pre-determined gradations were carefully packed in a 600 mm wide flume through which، variation of pheartic surface as a result of the tail-water variation – to resume unsteady flow conditions – were optically recorded by means of a set of piezometers installed along the flume’s side-wall. Discharge rates were measured by a calibrated v-notch and the tail-water surface variations were precisely timed by means of delicate electrical equipments specially designed and manufactured for these experiments. Observations on the flow behaviors were then analyzed using SPSS software in order to drive mathematical relationships between measured parameters. Findings indicate that: a) The so-called Forchheimer equation can be successfully employed for analyses of nonlinear- steady as well as nonlinear-unsteady regimes in coarse granular porous media. b) Although a third term defining effects of unsteadiness may be included in the above mentioned equation، it is of little engineering importance. c) The nature of hydraulic gradient (i) variations versus Reynolds number (Re) – which were plotted for all sets of observations – confirms existence of turbulent conditions in all experiments. d) Our unique experimentation set-up adequately resembles the actual prototype conditions.