Dampening Flow Induced Vibration Due To Branching Of Duct at Elbow

Ducts are closed path used for conveying air, Flue gas, Material, ash and etc from one system to another, in the power plant and in the industries. Ducts are routed to long distances, having abrupt change in direction and cross section which requires proper design for preventing the energy losses. Elbows are used for changing the direction of flow to 90 0 .Due to this abrupt change, eddies, Recirculation zones are formed. These Eddies having energy gradients, which produces thrust and in turn Vibration to the duct wall. Eddies Should be broken by stream lining the flow before taking any branching from the main duct. But in some ducting system either in power plant or Industrial, due to constraints Elbow duct itself is to be branched out. This paper presents dampening flow induced vibration, by analyzing the various arrangements using computational Fluid dynamic software Gambit-Fluent. becomes sharp 90 0 Elbow with branching at the elbow itself. The flow inside this ducting system is quite complicated and its difficult to predict the flow in this system by analytical methods. The flow pattern inside this arrangement can be visualised by using computational fluid dynamic software Gambit- Fluent. Grid is formed representing Flow field by using elements connected at the nodes using elements in the Gambit. The grid is then exported to Fluent , where the Boundary condition is applied and Solved. The Fluent have inviscid, Laminat, Spalart Almaras(1 equation), K-epsilon(2 equation), K omega( 2 Equation), Reynolds stress( 7 Equation),Detached Eddy simulation and Large eddy simulation for modeling the Viscous flow The K-epsilon model is one of the most common turbulence models, although it just doesn't perform well in cases of large adverse pressure gradients. It is a two equation model that means, it includes two extra transport equations to represent the turbulent properties of the flow. This allows a two equation model to account for history effects like convection and diffusion of turbulent energy. The first transported variable is turbulent kinetic energy, K. The second transported variable in this case is the turbulent dissipation,€ . It is the variable that determines the scale of the turbulence, whereas the first variable, K, determines the energy in the turbulence. There are two major formulations of K-epsilon models that of Launder and Sharma is typically called the "Standard" K-epsilon Model. The original impetus for the K-epsilon model was to improve the mixing-length model, as well as to find an alternative to algebraically prescribing turbulent length scales in moderate to high complexity flows.K-epsilon model has been shown to be useful for free-shear layer flows with relatively small pressure gradients. Similarly, for wall-bounded and internal flows, the model gives good results only in cases where mean pressure gradients are small; accuracy has been shown experimentally to be reduced for flows containing large adverse pressure gradients. The equation for the K-epsilon model is in built in fluent software itself.