| The pipe network system is a very complicated system to supply water, to the improvement that water quality, water demand require , constant enlargement of the scale of water supply with users, In our country thousands of city supply water systems already existed don't meet demands of city development according to present experience operation way. In view of this kind of current situation, it is very necessary for us to make the theory to assess and analysis to design and transformation of the pipe network system. Hydraulic analysis of supply water pipe network is supply water pipe network design , transform and management various kinds of use theoretical foundation of problem to solve. The key question of hydraulic analysis in supply water pipe network is hydraulic computation of supply water pipe network . In traditional water supply pipe network simulation calculation , it considers the way head loss only usually, and has not considered local resistance losses caused the fittings of the valve inclusive and some appurtenance , thinks that they are very much little to may be ignored comparing with the way head loss. But in the hydraulic computation of short pipe , the some local resistance losses of such appurtenance as three –way pipe , valve ,etc. can't be neglected. And neglect the head losses of these appurtenances, its result might differ greatly with the actual conditions still. This text set up the physical models and mathematics models of discharge three-way pipe and conflux three-way pipe at first, adopt the k -εequation as calculating models of the turbulance , then carry on the data processing and calculation to the result of imitating , draw the local resistance coefficient of the three-way pipe. And then prove it with the experiment , the experiment result and simulation result are to be relatively good . Through studying the numerical simulation and experiment of discharge the three-way pipe , draw the following conclusion: (1)The line branch resistance coefficient of discharge three-way pipe ξc,Π= 1.9754x2-3.11x+1.20(among themx =υΠ/υc )(2)The resistance coefficient of side branch ξc,n= 3.3665x2-4.1266x+ 2.1729(among them x =υΠ/υc)(3)The flow distribution relation: To the same kind of model , with the increase of the pressure , the flow assign percentage to slightly increase in line branch , accordingly flow assign in side branch slightly reduce, but the changing amount is not big, the greatest change amount does not exceed 4% of the flow of total quality either. (4)In the the same flow condition, side branch quality flow assign increases as the area of the branch increases . Through studying the numerical simulation of the conflux three-way pipe , draw the following conclusion: (1) To the conflux three-way pipe resistance coefficient of line branch is foreign to its geometry, the formula in common use is: ? c , Π= 1.55x ? x2 (Among them n)cxm= m. (2)As to the standard conflux three-way pipe whose three pipes are same (namely d Π= d n = dc) ,The resistance coefficient of side branch 2ξc , n = ? 1.2203 x + 3.0576 x? 0.828 (among them n)cxm= m. Then, while local resistance of three-way pipe applying to hydraulic computation of the pipe network , draw : (1) Hydraulic computation in large-scale water supply pipe network ( l / d ≥1000) , some local loss comparing with head loss, Its value is relatively small, can be ignored in engineering calculation; (2)At appurtenance the more,or under the situation of l / d ≤1000,some error caused local loss reach 20% more than the percent , so it can not neglect ; (3)Pressure heavy, some local loss can heavy influence to the whole pipe network.. So, in small-scale or appurtenance more pipe networks calculation,we must consider the influence of local loss . Or else the local loss will cause assign inequality of flow or pressure, and cause inconvenient or serious consequence to user.
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