![]() ![]() ![]() When a flow regime transition takes place, the topographical structure of the solution changes very little and instead the constitutive relations (interfacial drag, wall shear, etc.,) change dramatically via the flow regime maps.ĬFD: As part of my thesis, some multidimensional CFD has been required to (roughly) model the turbulent viscosity present in the Thorpe experiment for use in the 1-D model. Currently, work is underway to extend the analysis to two-phase flows with a large density ratio, i.e., air-water, which is more relevant to nuclear reactor safety applications.ġHistorically, the 1-D two-fluid model for nuclear safety applications has been tightly coupled to static flow regime maps. ![]() For the case of dense liquid-liquid flows, the hypothesis of Kreiss and Yström (2002) has been demonstrated for the unstable two-fluid model: the energy created by the instability is dissipated by the interaction of the nonlinearity and a viscous diffusion term to create a bounded, nonlinearly stable model. To study the nonlinear stability characteristics of the 1-D two-fluid model the code TFIT has been developed and utilized to simulate Thorpe’s experiment (1969) of the KH instability. Linear theory can only tell if waves will grow not how they will evolve. However, simply studying the linear stability of an unstable model is not enough. It is shown that when the 1-D two-fluid model is properly constituted, a well-posed yet unstable model is able to accurately predict the onset of the KH instability by linear stability theory. Since this approach is relatively novel 1, the simplest transition has been studied: the transition from smooth to wavy (nearly) horizontal stratified flow, i.e., the Kelvin-Helmholtz (KH) instability. The focus of my PhD work has been to use the inherent instability of the 1-D two-fluid model to dynamically capture flow regime transitions. ![]() While advances are being made to extend nuclear thermal hydraulics to multidimensional CFD, the 1-D two-fluid model will likely continue to be a mainstay in reactor safety analysis for years to come. Summary: The 1-D two-fluid model has been used extensively in nuclear reactor safety analysis calculations for the past 40 years. Nonlinear Stability Analysis of a 1-D Two-fluid Model for the Kelvin- Helmholtz RESEARCH EXPERIENCE PhD Research (2009-present) ![]()
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