Resumo

GARCIA, EDUARD ALBERTO; OSORIO, JAIRO ALEXANDER  e  CORTES, MISAEL. MATHEMATICAL MODELING OF TWO-PHASE FLOW: PRESSURE - WAVE VELOCITY EFFECT ON THE MAGNITUDE AND PRESSURES DISTRIBUTION. Dyna rev.fac.nac.minas [online]. 2008, vol.75, n.154, pp.47-58. ISSN 0012-7353.

Quick movements of flow control system devices can produce transient flows where vapor pressure is reached, creating two-phase flows: liquid-vapor. Cavitation can be present in some cases. Under these conditions, the flow is characterized by spatial and temporal changes in the velocity of pressure waves due to an increase in the void fraction. Typically the wave velocity in two-phase flows is determined using an isothermal assumption like Wylie’s equation. In this research the adiabatic assumption was introduced and a new equation was obtained. Experimental set up was built; the results were used to analyze the system response and to study the wave velocity variation along the distributed vaporous cavitation zone and the vapor cavity. The experimental results were compared to numerical simulations assuming adiabatic and isothermal bubble vapor behavior. A good prediction of the maximum pressures magnitude was obtained with both models; however, both models predicted longer time intervals between consecutive pressure pulses compared to the measured data. In general, better predictions were obtained with the adiabatic wave velocity expression. The volume of the vapor cavity obtained by using adiabatic or isothermal behavior was similar; however, both models predicted the creation of additional cavities not detected in the experimental results.

Palavras-chave : two-phase flows; vaporous cavitation; pressure wave velocity.

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