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Numerical investigation of cryogenic cavitation in liquefied natural gas (LNG) flows using a homogeneous flow model Rahbarimanesh, Saeed


Fluid machinery used for pumping cryogenic liquid fuels are severely impacted by the onset and development of cavitation. Cavitation in non-cryogenic fluids is commonly assumed to be isothermal, but cavitation in cryogenic fluids is substantially influenced by thermal effects. The present research investigates the cavitation in liquefied natural gas (LNG) flows by developing a computational fluid dynamics solver for modeling cryogenic cavitation. The solver employs a homogenous equilibrium mixture approach to compute the multiphase solution in a density-based Eulerian framework. Thermal effects are captured via a coupled solution of a cryogenic form of the density, momentum, and energy equations. Thermophysical properties of the cryogenic fluid are corrected using the computed pressure and temperature fields to account for the baroclinic nature of the density field and temperature dependence of the fluid’s saturation properties, specific heat, and dynamic viscosity. The developed cryogenic solver is validated against experimental measurements of cavitating flow of liquid nitrogen in a circular orifice and a Laval nozzle, achieving good agreement for the considered range of operating conditions. The resulting fluid properties of a simulated LNG cavitation flow inside the Laval nozzle are also verified with a good accuracy against the reference property database. Detailed physics of the LNG phase-change phenomena is investigated by employing the developed solver for simulating two fundamental case studies in a variety range of operating conditions: 1) cavitating flow of LNG inside the Laval nozzle; and 2) cavitating mixing layer of LNG behind a flat plate splitter, with the aim of characterizing the interaction mechanisms between LNG vaporization-condensation processes and shear-layer instabilities, and their correlations with thermodynamic effects. The conducted investigations exemplify the dynamics of LNG cavitation in basic wall-bounded and free shear layers of LNG, so providing a refined database for understanding cavity-vortex interactions in complex LNG-based turbomachinery.

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