مدل سازي تحليلي و عددي توزيع تنش برشي جداره در خم كانال هاي مركب

چكيده انگليسي :

Analytical and Numerical Modeling of the Boundary Shear Stress Distribution in the Curved compound Open Channels Fatemeh Farshi f farshi@cv iut ac ir Date of Submission April 7 2018 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree Ph D Language FarsiSupervisor Dr Abdorreza Kabiri Samani akabiri@cc iut ac ir Supervisor Dr Mohammad Reza Chamani mchamani@cc iut ac ir Advisor Dr Hossein Atoof h atoof@me iut ac ir AbstractThree previous researches were combined to develop an analytical model for evaluation of boundary shear stress incompound open channel bends In the present model perpendicular volumetric elements are generated in all crosssections of a bend Each element represents an equation with two parameters as secondary current parameter andmomentum transfer coefficient standing for acceleration and apparent shear forces For each cross section with Nelements N equations with N unknowns of stream wise depth averaged velocity are derived The boundary shearstress distribution is then calculated using the Darcy Weisbach relationship Simultaneous effects of centrifugalforce floodplain interferences and variation of the depth averaged velocity are combined in an analytical model toderive a relationship for estimating the secondary current parameter and the momentum transfer coefficient in bendsof the compound open channels This parameters are evaluated using the experimental data To generalize theobtained relationships numerical modelling is performed using an open source CFD software namely OpenFOAM In the present study the Reynolds Averaged Navier Stocks equations RANS are solved and a single phase solver simpleFoam is applied with an appropriate boundary condition on the free surface The SST k turbulent model isapplied for turbulence modelling of the flow field To obtain general correlations for the hydrodynamiccharacteristics of the flow such as the velocity components different numerical models are developed Accordingly all the present numerical results as well as the available experimental data are used to derive correlations for thesecondary current parameter and the momentum transfer coefficient in curved compound open channels Key Words Boundary shear stress Depth averaged velocity Secondary currents Compound channel Openchannel bend Momentum transfer coefficient IntroductionBoundary shear stress has a significant contribution in safe and economic design of openchannels especially in curved compound channels Analytical modelling of the flow field inopen channels requires proper identification of the hydrodynamic characteristics of the flow Open channels rarely have straight reaches they usually have floodplains known as compoundopen channels When the flow shifts away from the main channel into the floodplains itsstructures become more complex The difference in velocity between the main channel and thefloodplain leads to the generation of a shear layer which produces organized vortices at theinterface 1 In a compound curved channel the flow field is more complex than a straightcompound open channel The flow in the main channel follows a curved path whereas thefloodplain flow continues straightly The transversal velocities in the main channel increase up to Associate Professor Department of Civil Engineering Isfahan University of Technology Isfahan Iran Associate Professor Department of Civil Engineering Isfahan University of Technology Isfahan Iran Assistant Professor Iran Aircraft Manufacturing Industrial Company Isfahan Iran

فرشي، فاطمه

مدل سازي تحليلي و عددي توزيع تنش برشي جداره در خم كانال هاي مركب

تنش برشي جداره , جريان هاي ثانويه , كانال مركب , خم كانال , ضريب انتقال مومنتوم