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In practical engineering applications, has been widely applied to the fluid piped. Whether conveying what substances are required to properly resolve the contradiction between energy consumption and supply of fluid along the pipeline, to ensure the safety of the completion of the economic task of gathering and transport. The friction loss is one of the main factors of pressure energy consumption of piped process. The two parts of the pipe friction losses, including along the friction loss and the loss of local friction, Friction Loss along has reached widespread, systematic extent for local friction loss, due to limitations of the experimental studies , discrete and inaccuracies, resulting in a great error of the experimental determination of a variety of local friction of the relevant data with actual data. Since the end of the 20th century, with the rapid development of computer technology, as well as the formation of computational fluid dynamics, making possible the original can not be experimentally determined, and not through theoretical analysis to solve local friction, fluid mechanics has been solved numerically. In this paper, the sudden expansion pipe T tee and 90 ° elbow typical valve parts, the use of computational fluid dynamics software FLUENT General, in laminar and turbulent flow conditions, the numerical simulation of the flow in the pipe, The internal flow field characteristics of three typical valve element analysis of the local resistance characteristics. Sudden expansion tube, the Reynolds number and the sudden expansion than the local resistance of the pipeline has a great influence, as the Reynolds number increases, after the sudden expansion interface along deceleration supercharged, close to the wall near the low-speed laminar flow of fluid The particles, in the opposite flow direction under the pressure differential, flow rate is gradually reduced to zero, then the mainstream and the side wall out of, and the formation of the recirculation zone, and the length of the recirculation zone and the Reynolds number, sudden expansion ratio were highly proportional relationship. T-tee, local resistance is generally produced in the position of the mainstream and tributary confluence and collision, and its role as the extension of the axial distance gradually weakened. In the case of the horizontal feed pipe to maintain a constant, within a certain range, with the vertical tube diameter increases, the local head loss increases. The bends in the flow field, due to the inertial force and the curve of the role of water, the pressure is maximum in the vicinity of the plane of symmetry of the 90 ° elbow, the pressure distribution of the entire pipe section zonal, and since the generated orthogonal to the direction of the mainstream secondary flow, the inside of the curve presented to the outside of the bend pressure gradually increasing trend. For sudden pipe expansion and 90 ° elbow local friction coefficient is calculated and compared with the corresponding experience obtained simulation values ??floating experience up and down and little change in the two match, simulation value can be changed to some extent on the value of experience in engineering practice.
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