طراحي تبديل همگرا در بالا دست دريچه كشويي در كانال باعرض متفاوت

چكيده انگليسي :

Design of Contraction Transition at the Upstream Reach for Sluice Gates in Channels of Different Widths Tohid Samiadel tohid samiadel@cv iut ac ir tohid samiadel@gmail com Date of Submission 2009 06 8 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor M K Beirami beirami@cc iut ac irAbstract Transitions are hydraulic structures which are used in the case of changing cross sectionaldimensions in a relatively short distance They include contractions and expansions Contractions are used for the reduction but expansions are for the broading of the channelsection Straight vertical types of contraction are mostly suitable for flow in rectangularchannels Certain flow discharge measurement or control gates in channels may be calledunderflow gates Common examples are the sluice and radial gates In literatures manyresearches related to the sluice gates have done without contractions at the upstream reach ofthe gate In this research the main aim was the usage of a contraction for reducingundesirable vortices at the upstream reach of the sluice gates reducing the disturbances andstanding waves at the downstream reach of the gate and also reducing the energy loss of theflow through the gate Experiments are completed in a channel with 0 405m width and 9 5mlong The channel upstream width was 0 405m and at the downstream reach channels of 0 2 0 24 and 0 3m were used In various designs of transitions a straight length paralleling to theflow direction with the same width as the gate and inclined length for transition have beenused The relative lengths of the straight one to the width of the gate were 0 0 8 and 1 4 Angle of the inclined one with the flow direction was 30 45 and 90 degrees Totally 9experimental models for each downstream width of the channel i e 27 models and 1152 runson the models with free and submerged flow at the downstream reach have been done Toestimate free and submerge discharge 5 semi theoretical models using the Energy Momentum Continuity equations and also equations of Froude numbers of flow T theupstream reach of the transition and gate cross section are presented Equations have givenwithout contraction coefficients Comparison a few data of this research with someexperimental data of the other investigators which have done in the same experimentalconditions proved the accuracy of the experiments The results of this research showed thatthe straight length of transition paralleling to the flow direction is more effective in reducingdisturbances and standing waves at the downstream reach of the gate but inclined part of thetransition reduces the intensity of vortices appearing at the upstream reach of the gate Transitions with only inclined angle give the best result in reducing the flow energy loss Results of this investigation gave the following recommendations First using a transitioncontaining an inclined wall with a contraction angle equal or less than 30 degrees and astraight wall paralleling to the flow direction with a length not less than the gate width Second applying the Froude number at the upstream reach of the gate to predict the flowdischarge under the sluice gate Keywords Transition Contraction Sluice gate Vortex Energy equation Momentumequation Continuity equation Stilling basin

سميع عادل، توحيد

طراحي تبديل همگرا در بالا دست دريچه كشويي در كانال باعرض متفاوت

گرداب , رابطه انرژي , رابطه اندازه حركت , رابطه پيوستگي , حوضچه آرامش