Two-step explicit procedure formulation for fast decompression of two-phase water/steam mixture. [LMFBR]
For numerical solution of fast two-phase decompression taking place in heat transfer tubes following sudden tube rupture, the problem has been formulated in two-step explicit procedures. The basic schemes used are the two-step Lax-Wendroff scheme and the Rubin-Burstein scheme with special treatments provided for boundary condition formulation. The weak numerical instabilities associated with the basic Lax-Wendroff scheme are treated by aid of a pseudoviscous term added in the governing conservation equations. The pseudoviscous term will also spread any sharp discontinuities over a few mesh points so that the shocks are represented approximately. An earlier approach to this problem using the method of characteristics faced considerable difficulties in handling the flashing transients. The main difficulty was due to the increased nonlinearity, since the sonic speed changes by many factors and the flow accelerates with phase change, that results in large discontinuities which must be handled as internal boundaries. The direct finite difference technique with the pseudoviscosity treatment considered here is one of the approaches chosen to overcome this difficulty. Formulations given in the report include special considerations in the boundary condition treatment in anticipation of potential difficulties at the boundaries. The transient is actually driven from the boundaries, and prior works revealed that the boundary treatment is the key problem area.
- Research Organization:
- Argonne National Lab., Ill. (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 7246967
- Report Number(s):
- ANL-CT-76-46; TRN: 77-002019
- Country of Publication:
- United States
- Language:
- English
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