عنوان مقاله [English]
Though various relationships for the non-linear analysis of flow through coarse porous media may be found in the literature, their applicability for engineering usage is limited. Difficulties in determining the grain mean hydraulic radius is a basic issue in this regard, due to the complexities in estimating the specific surface parameter involved for such calculations. After reviewing related theoretical bases, this article examines the reliability of a number of recent models proposed for determination of the specific surface, using actual data. Findings indicate that the Sabin-Hansen method is a more realistic means for such a purpose and, in spite of it's simplicity, the Bazargan model leads to least accurate results.