Calculation of non-potential ideal gas flows in axisymmetric nozzles by the approximate factorization method

Formulations are developed in this study for rapid estimates of time-and-space-dependent pipe reaction forces caused by either sudden blowdown or flow stoppage in a fluid piping system. The analytical model is a uniform pipe with arbitrary bends and friction, a pressure source at one end, and a sudden opening or closing value at the other end. A homogeneous mixture of liquid and ideal gas flows in the system. The method of characteristics is used to obtain fluid-mechanical properties, which then are employed to predict associated pipe loads. A graphical summary of results includes initial and steady blowdown forces, wave propagation forces, and local force-time behavior. The formulations presented are expected to provide a basis for confident, efficient, and economical design of pipe system layout and motion restraints.

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Numerical Simulation of Viscous Flow-Field in Cascade Using Thin-Layer Equations and AF Method

Volume 2: 19th Computers and Information in Engineering Conference ◽

10.1115/detc99/cie-9045 ◽

1999 ◽

Author(s):

Yumin Xiao ◽

R. S. Amano

Keyword(s):

Flow Field ◽

Boundary Conditions ◽

Viscous Flow ◽

Secondary Flow ◽

Three Dimensional ◽

Factorization Method ◽

Computational Domain ◽

Approximate Factorization ◽

Calculation Results ◽

Transonic Cascade

Abstract In this paper an implicit 3-D solver for computations of a viscous flow has been developed and the computations of the flow between blade passage are presented. This method employs an AF (Approximate Factorization) method in which four techniques are incorporated to speed up convergence to the steady-state solutions: (1) body-fitted H-grid; (2) artificial viscosity; (3) implicit residual smoothing; and (4) local time-stepping. The two-dimensional pseudo-characteristic method was used to determine the inlet and outlet boundary conditions of the computational domain and the periodic boundary conditions were used at inter-boards. The validation cases include subsonic and transonic viscous flows in C3X cascade. Results for these turbine cascade flows are presented and compared with experiments at corresponding conditions. Computed pressure distributions on blade surfaces show good agreement with the published experimental data. This method was further applied to a three-dimensional case and demonstrated the code capability for predicting the secondary flow in a 3-D transonic flow-field. From these computations it was found that the proposed method possesses superior convergence characteristics and can be extended to unsteady flow calculations. Finally, it was observed that the three-dimensional calculation results show that the secondary flow mechanism in a transonic cascade seems to be quit different from those, in a subsonic case.

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