هيدروليك جريان بر روي سرريزهاي كليد پيانويي

چكيده انگليسي :

Hydraulics of flow over Piano Key Weirs Amir Javaheri a javaheri@cv iut ac ir January 28 2012 Civil Engineering Department Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Abdorreza Kabiri Samani Email address akabiri@cc iut ac irAbstractWeirs are normally provided for water level and flood control flow measurement environmentalenhancement and channel stabilization In engineering expression a weir must be able to satisfy thefundamental requirements such as hydraulic performance structural stability and environmental impacts Due to the extensive use of weirs in hydraulic systems more investigations are needed on such structures Weirs in channel are classified according to their configuration Based on their crest thickness weirs aredivided to sharp and broad crested weirs Weirs also divided in respect to their crest length sorted incontracted suppressed and long crested weir categories The capacity of weir refers to the discharge for agiven head of flow over its crest If the capacity of the weir is to be increased for a given width of approachchannel the long crested weirs offer feasible alternatives There are several ways to enlarge the weir crestfor a given approach width Oblique Labyrinth Duckbill and Piano Key weirs are the most commonexamples of long crested type weirs Search for an optimal weir shape which maintains high performanceand low cost guided researchers to the concept of non rectilinear weirs The innovative shape of a non rectilinear weir known as a Piano Key weir PK weir is an interesting structure that increases the totaleffective crest length thereby increasing the discharge capacity of the weir Piano Key weir can be placedon existing or new gravity dam section it will allow for specific flows of up to 100 m3 s m it can multiplyat least by four the flow of a normal weir and it is structurally simple and easy to build Although this weirhas significant benefits there is no extensive study to determine discharge coefficient in free andsubmerged flow and threshold submergence was not determined Because of complexity of flow over Pianokey weirs the best choice to investigate flow characteristics is employing experimental data In this study acomprehensive experimental investigation was performed to better understand the effects of Piano Keyweir geometry on discharge coefficient for both free and submerged flow conditions and thresholdsubmergence The effects of the Piano Key weir s geometric parameters including weir length and height up and downstream key widths as well as up and downstream apex overhangs on weir flow dischargecoefficient were investigated Using the results on the basis of a comprehensive dataset practical dischargecoefficient relations associated with the standard weir equation were proposed for both free and submergedflow over the Piano Key weirs and discharge coefficient relation for rectangular labyrinth weirs in free flowcondition In addition an equation was proposed to determine the threshold submergence of PK weirs Equations were developed by using the Statistical Package for the Social Sciences SPSS To check thecorrelations the normalized root mean square error NRMSE the weighted quadratic deviation WQD and the coefficient of determination R2 were considered Contrary to R2 both NRMSE and WQD must besmall to have a good relation among parameters and the data Key WordsDischarge coefficient Experimental model Free flow Piano Key weir Submerged flow Threshold submergence

جواهري، امير

هيدروليك جريان بر روي سرريزهاي كليد پيانويي

ضريب دبي , جريان آزاد , جريان مستغرق , آستانه استغراق