Turbulence studies in open channel transition using laser doppler velocimetry

As the flow passes through a bridges, a channel transi t ion in the form of contraction and subsequentexpansion is involved. Open channel transitions are commonlyused in hydraul ic structures in variety of si tuat ions toserve as link or connection with minimum possible energyloss. Since these transitions are meant for continuous use,their role in minimization of the energy loss and attenuationof turbulence assumes significance. Non-uniform distributionof velocity in rapidly changing turbulent flow transitionoften leads to appreciable error in the estimate of theenergy loss. In designing channel transitions, such asexpansion or contraction or a change in bed elevation orboth, it is always desirable to avoid, excessive energylosses.Turbulence in open channels differs from the turbulencein conduits in that the effect of a free surface onturbulence, peculiar to open channel flow assumes greatsignificance. Free surface has a unique role in governingthe turbulence in the open channel flows. The effect of afree surface on turbulence is particularly important for thecalculation of open channel transition flows. Hence theeffect of free surface is emphasized in this research.It is indispensable in hydr-au l ic engineering toinvestigate structures of turbulence in open channeltransition in order to control turbulent flows and to designhydraulic structures properly. Thus, one of the purposes tostudy the turbulence in open channel transition is to gaininsight into the properties and interactions of theseturbulent structures. Much less information is availableregarding the turbulence characteristics in the open channeltransitions. The study of the problem of the open channeltransitions has fundamental significance. These problems arecharacterised by a rapidly changi ng flow field which displays