بررسي تاثير زبري موضعي بر ضريب اختلاط عرضي در يك كانال باز مستطيلي

چكيده انگليسي :

AbstractDue to increasing number of world population and deficiency of the reliable resources of suitable water there is ahighly request for optimal use of both surface and ground water The continuous growth of surface waterpollution especially in developing countries is one of the most critical issues for human communities In thisregard using mixing processes of the pollutants to refine and make the possibility of reusing the polluted water isone of the valuable methods to increase the amount of usable water Transverse mixing coefficient is one of thehydraulic parameters of flow by which the amount of self refinement and dilatation of rivers can be estimated This thesis investigates an experimental method for measuring and evaluating the hydraulic parameters of asurface water flow which are useful for refinement and re using polluted waters The investigation focuses oneffects of local roughness on transverse mixing coefficients of a flow that are key parameters to estimate theamount of self refinement and dilatation of rivers To investigate these effects the experimental method wasinitially employed to determine the transverse mixing coefficients of a flow by injecting a pollutant in the centerof an open channel flow and measuring its concentration at several sections located downstream of the injectionpoint To demonstrate and evaluate the method two rectangular straight open channels were used The length width and depth of the channels were 7m x 0 32m x 0 35m for the first one and 20m x 0 6m x 0 6m for thesecond one respectively The maximum flow rate of the first channel was 16 4 lit s and for the second channel itwas 75 lit s Water was circulated in the channels the flow was uniform and the depth of water was controlledwith a gate way Subsequently by means of submerged blocks various bottom roughness configurations werearranged and tested for the channels to investigate their effects on the measured coefficients Using the massconservation equation for calculating the spreading rate of materials and their concentration in channels theresults showed that for the first channel the arrangements of blocks could increased or decreased the transversemixing coefficients of the flow depending on the shape of roughness However for the second channel theexistence of blocks with any configuration overall increased the transverse mixing coefficient Also increasingthe distance of the blocks from the polluting source increased the effects of the bottom roughness on thecoefficients and mixing length for the first channel however no significant changes was observed in thecoefficient of the second channel Furthermore the test results showed that decreasing the alternative distancebetween blocks in the first channel increased the transverse mixing coefficient and for the second channel thebest alternative distance between the blocks measured at about 1 meter Finally an analysis was performedshowing that for a constant flow velocity transverse mixing coefficient increased with the width to depth ratio To sum up the results show that the secondary circulations in narrow waterways have more relative influenceand hence have more effects on the flow As a result the turbulent intensity and accordingly the turbulentdiffusion have been increased Keywords Transverse mixing coefficients surface water pollution self refinement of surfacewater alternative local roughness complete mixing length

سعادت پور، عاليه

بررسي تاثير زبري موضعي بر ضريب اختلاط عرضي در يك كانال باز مستطيلي

آلودگي , طول اختلاط كامل