Instability in two-phase flows of steam

Abstract

In two-phase flows of steam, when the velocity is between the equilibrium and frozen speeds of sound, the system is fundamentally unstable. Because any disturbance of the system, e.g. imposition of a small supercooling on the fluid, will cause condensation, the resulting heat release will accelerate the flow and increase the supercooling and thus move the system further from thermodynamic equilibrium. But in high-speed flows of a two-phase mixture, dynamic changes affect the thermodynamic equilibrium within the fluid, leading to phase change, and the heat release resulting from condensation disturbs the flow further and can also cause the disturbances to be amplified at other Mach numbers. To investigate the existence of instabilities in such flows, the behaviour of small perturbations of the system has been examined using stability theory. It is found that, although the amplification rate is highest between the equilibrium and frozen speeds of sound, such flows are temporally unstable at all Mach numbers.

Numerical modeling and high-order scheme for wet steam flow

“…In equation (39), the expression _ p e h m þ _ p is proved to be the square of frozen speed of sound 40 (detailed derivation is presented in Appendix 2)…”

Time-Marching Method for Computations of High-Speed Compressible Flow on Structured and Unstructured Grid

“…There are two basic types of computational grid, known as structured grid and unstructured grid. A structured grid looks most generally like a twisted coordinate system with each node of a cell represented by an (x, y, z) notation, as denoted by [5][6][7][8][9][10][11][12] . It is a common practice to use structured mesh in a relatively simple geometry because its generation process is easy, both in practicing and programming.…”