Experimental investigation of flow behavior in smooth and rough artificial fractures

- A bump is seen in the Moody diagram.
- The Forchheimer and Izbash laws describe flow behavior in fractures.
- The semi-empirical model predicts satisfactorily the experimental results.
- The experimental results are compatible with data of other researchers.
- The Dupuit approximation for flow in fractures is explicitly verified.

SummaryThe flow behavior in smooth and artificial rough fractures is experimentally investigated. The piezometric head is measured at several positions to determine experimentally the head gradient through a sophisticated procedure, and the hypothesis of one-dimensional flow is verified. It is demonstrated that both the Forchheimer and Izbash equations adequately describe the flow conditions, and proper coefficients for these equations are estimated. The experimental results are also used to construct a Moody-type diagram, where a non-monotonic dependence is shown to characterize the friction factor - Reynolds number relationship in the transition between laminar and weak turbulent flow.