Gravity-driven open-channel flows carrying coarse sediment over an erodible granular deposit are studied. Results of laboratory experiments with artificial sediments in a rectangular tilting flume are described and analyzed. Besides integral quantities such as flow rate of mixture, transport concentration of sediment and hydraulic gradient, the experiments include measurements of the one-dimensional velocity distribution across the flow. A vertical profile of the longitudinal component of local velocity is measured across the vertical axis of symmetry of a flume cross section using three independent measuring methods. Due to strong flow stratification, the velocity profile covers regions of very different local concentrations of sediment from virtually zero concentration to the maximum concentration of bed packing. The layered character of the flow results in a velocity distribution which tends to be different in the transport layer above the bed and in the sediment-free region between the top of the transport layer and the water surface. Velocity profiles and integral flow quantities are analyzed with the aim of evaluating the layered structure of the flow and identifying interfaces in the flow with a developed transport layer above the upper plane bed.
The present paper deals with the classification of the suitability of combined sewers for the installation of heat exchangers and with assessment of the theoretical potential of wastewater in the sewer system for heating of buildings. A classification scheme involving criteria like theoretically available heat, sewer diameter, number of the heat exchanger parallel modules in the sewer cross-section, hydraulic conditions (hydraulic capacity of the sewer, pressurized flow), and potential fouling by biofilm growth was developed. First, individual sewers in the pilot catchment were assessed based on monitoring the flow characteristics and wastewater temperatures and on pipe flow modelling. Second, connectivity of the suitable and partly suitable sewers was examined with respect to the length necessary for the installation of the heat exchanger with the minimum required power of 100 kW. For the continuous sewer sections, the maximum potential power was calculated. The presented approach is generally applicable, however, for other heat exchanger types and other climatic and economic conditions, values of the suitability criteria for the heat exchanger installation must be adapted.