作者: Kuang Ding, Hong Wu Zhu, Jin Ya Zhang, Chuan Wang, Jian Sheng Hao

摘要: Deadleg is a kind of blind pipe connected with a main pipe used for fluid transportation, which has distinct flow characteristics. This work aims to investigate the complex flow, oil/water separation and the relation between fluid flow and water concentration of a vertical deadleg. The investigation was based on the solution of algebraic slip mixture model, which calculated the continuity and momentum equations for the mixture of oil and water, and solved the volume fraction equation for the secondary phase. The computed results indicated that the mixing zone of the deadleg consists of two circulation vortexes and the whole mixing length depends on the inlet flow intensity. Furthermore, distinct oil/water stratification forms in the stagnant zone, and the maximum water volumetric concentration is related to the length of stagnant zone and also influenced by the flow intensity of the main pipe, which could increase from 25% to 72% with inlet velocity ranges from 0.75m/s to 5m/s.

2465

作者: Xue Li Xia, Hong Fu Qiang

摘要: To evaluate an influence of the various bend diameter ratio R_{c}/R and velocity on the flow property of gel propellant in a 90^{0} pipe bend, the 3D governing equations of the steady, incompressible, isothermal, laminar flow of a power-law, shear-thinning gel propellant in pipe bend were formulated, discretized and solved, a SIMPLEC numerical algorithm was applied for the solution of the flow field, which on a series of sharp 90^{0} curved pipelines with nine kinds of bend diameter ratio and the inner diameters of 8mm were used on condition of seven kinds of Reynolds numbers. The pressure and velocity distributions were obtained, the empirical equation of local resistance coefficient from numerical experiments was conducted, providing the interrelations between the best bend diameter ratio and flow velocity in engineering design. The results indicate that the pressure and velocity distributions were non-linear, and which become tremendous with increasing Reynolds numbers. The results suggest that the dot of maximum velocity occurs the wall outside of a pipe bend, and which is more near to the wall outside of a pipe bend along the flowing direction and increasing the velocity. The phenomena of particle sedimentation should be took into account to investigate the flowing behavior of gel propellant in curved pipes on condition of lower Reynolds numbers.

2274

作者: I. Malico, C. Ferrão, P.J.S.A. Ferreira de Sousa

摘要: This paper presents direct numerical simulations for the flow through regular porous media composed of equal size staggered square cylinders obtained with a compact finite differences immersed boundary method. Different moderate Reynolds numbers are simulated in order to capture the dependence of the pressure drop with the Reynolds number in the Forchheimer regime. The pressure drop predictions agree well with the Hazen-Dupuit-Darcy model; however, when compared to a widely used semi-empirical correlation, the modified Ergun equation, the agreement is poor. A better agreement is found if the particle diameter is taken to be equal to the cylinder diameter. From the intrinsic-averaged pressure calculated along the flow direction, it can be seen that, for the porous media studied, the bulk pressure drop dominates and the entrance and exit effects are negligible.

192

作者: M Arul Prakash, K. Mayilsamy, P. Rajesh Kanna

摘要: The effect of obstacle in an incompressible laminar wall jet flow is investigated numerically. Heat transfer enhancements in cooling of heated objects are found wide application in almost all fields of engineering. Wall jet cooling is one such important application. From literature survey in the related area it is found that the influence of the presence of obstacles in the flow path of laminar wall jet needs to be investigated. The objective of the present work is to study the effect of obstacle on flow characteristics of the incompressible laminar wall jet. The wall jet is blown along a horizontal bottom wall. The obstacle block is placed on the bottom wall. A two dimensional computational domain is considered. At the left side of the computational domain a vertical wall is present. The right and top of the domains are open to ambient fluid. An in-house code developed based on vorticity-stream function formulation for the full computational domain is used to solve the problem. The flow pattern, formation and growth of recirculation, attachment and re-attachment behaviors and the velocity profiles were studied with and without obstacle. From the results of the investigations, the influences of obstacle on flow characteristics of wall jet was found more at higher Reynolds numbers and at the regions nearer to the obstacle.

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