Experimental Study on Energy Gradient of Sediment Transportation in Spiral Pipe Flow

Forced spiral flow can be produced in a circular pipe flow by erecting blades in the pipe. The velocity of spiral pipe flow with sediment can be decomposed into the circumferential vortex flow velocity and the axial flow velocity as normal pipe flow. The former acts as uplifting the sediment and the latter transports it. Therefore the transported sediment with the form of bed load can be changed as suspended load easily. In this paper, with the momentum law and the momentum moment law, the forced spiral flow was analysed and studied in theory and by experiment, which was in two states of clean water and sediment laden water separately. The obtained results are: the energy gradient of spiral pipe flow can be expressed with Darcy's equation; it has more ability of sediment transportation than normal pipe flow at the same energy gradient; the additional energy gradient of uplifting sediment is proportional to the sediment concentration in water. It lays a reliable basis for studying sediment transportation in spiral flow.