Experimental and numerical investigation of cutter head dredging flows

To increase the understanding of complex flows in dredging cutter heads, an experimental and numerical investigation of these flows has been made. As a first step toward the investigation of the mixture flow in a complete cutter head that actually cuts the soil, the simplified case of the flow of water in a freely rotating cutter head is considered here. Using stationary acoustic doppler velocimetry, three-dimensional velocity fields inside a cutter head have been measured. In addition, finite-element computations of the velocity field have been performed, using the potential flow model. These experimental and numerical investigations clarify the role of the angular velocity of the cutter head and the suction flow rate in the suction pipe that is generated by the dredge pump. Depending on a nondimensional flow number, three flow regimes are observed in the computations. For low flow numbers, the rotation of the cutter head dominates the flow, and an outward flow occurs near the cutter ring. For high flow numbers, the suction flow dominates the flow, and an inward flow exists around the entire contour of the cutter head. For the flow number corresponding to the theoretical hydraulic design condition, there is a balance between the flows induced by rotation and suction. The measured and computed velocity fields have been compared, showing good qualitative agreement and reasonable quantitative agreement.