Friction Factors in Solid Material Laden Systems

The value of the Darcy-Weisbach friction factor, necessary for calculating energy losses in transporting solid materials, is determined. The Darcy-Weisbach friction factor f is divided into two parts, f' and f. Term f' is related with the grain roughness and term f is related with the form drag of the bed configurations or modes of transport. The form-drag factor f is expressed as a function of Φ and 4R/d₅₀. Dimensional analysis is made for the variables involved in the resistance phenomenon both in free surface and pressurized flows. The functional relationships between the above mentioned dimensionless groups are obtained by using the data given in literature for both types of flows. The wide scatter of the data points reflects the need for better experimental techniques and a better understanding of transport modes and bed forms related with them.