Experimental Study of Unsteady Turbulent Flow Coefficients through Granular Porous Media and Their Contribution to the Energy Losses

摘要

This paper aims to cast light on the coefficients of non-linear equation governing unsteady turbulent flow through coarse porous media commonly known as Forchheimer's equation. Experimental pilot made use of a physical model consisting of a flume of 13 m length, being controlled by an electro-mechanical device to create different types of flow regimes. A range of granular media with a mean diameter of 7.5 mm for Small crashed (Sc) to 14 mm for Medium crashed (Mc) were packed in the flume at different runs to simulate coarse porous media capable of sustaining turbulent flow, either unsteady or steady. Findings indicate that: coefficient of the linear flow term decreases (47.3% and 91.9% in Sc and Mc aggregate) with increasing mean grain size, respectively. In addition, coefficient of the turbulent term-the effects of inertia forces-increases (87.9% and 27.2% in 5c and Me aggregate) with increasing mean grain size, respectively. Furthermore, coefficient of the unsteady term-local acceleration term in the Forchheimer's equation-shows a rapid increase (146.9% in Sc and 125.6% in Mc) with increasing velocity. Moreover, the nature of hydraulic gradient (ⅰ) variations versus Reynolds number (Re) - which were plotted for all sets of observations-confirms the existence of turbulent conditions in most experiments. Finally, the head losses and contribution of above-mentioned terms to the pressure drop was quite analyzed.