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Titolo:
TRIPLE-SHOCK ENTROPY THEOREM AND ITS CONSEQUENCES
Autore:
HENDERSON LF; MENIKOFF R;
Indirizzi:
8 DAMOUR AV,E LINDFIELD SYDNEY NSW 2070 AUSTRALIA CNRS,AEROTHERM LAB F-92190 MEUDON FRANCE TOHOKU UNIV,INST FLUID SCI,SHOCK WAVE RES CTR SENDAI MIYAGI 980 JAPAN BEN GURION UNIV NEGEV,DEPT MECH ENGN IL-84105 BEER SHEVA ISRAEL LOS ALAMOS NATL LAB,DIV THEORET LOS ALAMOS NM 87545
Titolo Testata:
Journal of Fluid Mechanics
, volume: 366, anno: 1998,
pagine: 179 - 210
SICI:
0022-1120(1998)366:<179:TETAIC>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
MACH REFLECTION; WAVE REFLECTIONS; STEADY FLOWS; TRANSITION; RECONSIDERATION; INTERFACE; EMISSION; FRONTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
42
Recensione:
Indirizzi per estratti:
Citazione:
L.F. Henderson e R. Menikoff, "TRIPLE-SHOCK ENTROPY THEOREM AND ITS CONSEQUENCES", Journal of Fluid Mechanics, 366, 1998, pp. 179-210

Abstract

For a convex equation of state, a general theorem on shock waves is proved: a sequence of two shocks has a lower entropy than a single shock to the same final pressure. We call this the triple-shock entropy theorem. This theorem has important consequences for shock interactions. In one dimension the interaction of two shock waves of the opposite family always results in two outgoing shock waves. In two dimensions the intersection of three shocks, such as a Mach configuration, must have a contact. Moreover, the state behind the Mach stem has a higher entropy than the state behind the reflected shock. For the transition between a regular and Mach reflection, this suggests that the von Neumann(mechanical equilibrium) criterion would be prefered based on thermodynamic stability, i.e. maximum entropy subject to the system constraint that the total specific enthalpy is fixed. However, to explain the observed hysteresis of the transition we propose an analogy with phase transitions in which locally stable wave patterns (regular or Mach reflection) play the role of meta-stable thermodynamic states. The hysteresis effect would occur only when the transition threshold exceeds thebackground fluctuations. The transition threshold is affected by flowgradients in the neighbourhood of the shock intersection point and the background fluctuations are due to acoustic noise. Consequently, theoccurrence of hysteresis is sensitive to the experimental design, andonly under special circumstances is hysteresis observed.

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Documento generato il 23/11/20 alle ore 20:13:12