A force balance to measure the total drag of biofilms on test plates

A floating force balance has been designed and integrated into the working section of a to enable the measurement of total drag on test plates, which form part of the tunnel wall. Measurements completed include a calibration of the rig using a smooth acrylic plate, a smooth painted plate, and an artificially roughened plate. The painted plate and rough plate have also been studied with biofilms attached to their surface. The water tunnel and total drag rig have been built specifically to allow the detailed investigation of freshwater biofilm effects have on the flow through hydraulic conduits. Calibration results show that useful information can be obtained by using the force balance, particularly in association with other measurement techniques. Research into the effects of biofilms showsthat large increases in friction and effective roughness can be expected.