The variation of the water's density due to sedimentation processes and its role in modelling open channel flow

The complexity of the sediment dynamics and its relation with the free-surface flow is a constraint that derived on several assumptions for its theoretical analysis. One of these assumptions is to consider the density of the fluid a constant. Nevertheless, the interaction of the material from the bed and the flowing water provoke changes on the fluid density as a function of the water depth due to the sedimentation processes that take place in the viscous sublayer. The variation of the fluid's density is as well function of the velocity, channel roughness and flow rate. This paper describes some experimental works that had been taking place at the laboratory of the Institute of Geotechnichs and Hydro-engineering in order to determine the changes on the water density flowing through a flume over a movable sandy bed. Experimental density functions for different flow rates are depicted.