Subsequently, the transport states in relation to the average flow velocity, shown in the figure, are explained further:

Transport state b), floating and leaping motion, occurs with the reduction of the average flow velocity, and has a solids concentration profile in the lower flow cross-section, wherein all the solid particles are still in suspension. The resulting irregular or heterogeneous distribution is due to the lower concentration compared to the state a) flow rate. The backward turbulence leads to an increase of the solids content in the lower area of the flow cross-section [Führb62] [SteinR2005].