Study On Hydraulic Calculation And Velocity Distribution Of The Lower Channel Of A Novel Double-layer Sewer

Urban drainage system is an important kind of urban infrastructure. It is of greatimpacts on the investment, land use, operation and maintenance of the total urbandrainage system. It is well known that currently widely applied combined seweragesystem and separate sewerage system are with the problems of overflows, first flushrunoff pollution and misconnection, while the alternatives still in developing such asstormwater retention tank are infeasible to most of the developing countries due to highcost, extra land use and other issues.An in-line first flush runoff interception system based on novel double-layer pipeand double-layer manhole has been developed, which is able to achieve theabovementioned function. However, as an interlayer with various shapes is set, thelower channel of the double-layer pipe will have special hydraulic characteristics whichwill lead to different hydraulic calculation method and velocity distribution. Thisdissertation is intended to carry out researches on this topic by using theoreticalanalysis,experiments and numerical simulation. The key results are as follows:â‘ Hydraulic calculation for the lower channel of the double-layer pipe was studiedtheoretically with application of fundamental hydraulics and with respect to theparticular section shape, and some basic important findings were obtained. Thecalculation formula of common hydraulic elements of cross section was summarized,with respect to the geometrical characteristics of cross section, and general calculationformula for hydraulic elements of the0.50RH1,0.50RH2and1.0RH1type doublepipelower channelwere deducted.â‘¡Based on the analysis of the hydraulic experimental double pipe lower fluid, togain an understanding of the empirical hydraulic characteristics of fluid in pipeline.Verifying and correcting the applicability of the hydraulic calculation formula andgetting hydraulic calculation formula applied to0.5RH1and0.5RH2type double pipelower fluid. Establishing hydraulic calculation table and using FLUENT softwaresimulation to verify the correctness of the hydraulic calculation table.â‘¢Using FLUENT software to simulate the same experimental conditions of thelower pipe water flow and comparing simulation and experimental results.Themaximum error is less than five percent,which indicates that the simulation results havehigher accuracy. According to the simulation results, drawing the vertical velocity profile and sectional velocity distribution.Velocity distributions of the vertical sides arealmost symmetrical. Flow velocity contours closing to the side walls are similar to theside wall profile. With water depth increasing, the maximum velocity positions decline.