Praveen Ramaprabhu’s research while affiliated with University of North Carolina at Chapel Hill and other places

... In contrast, the evolution of the mixing width under longwave perturbations displays characteristics without a fixed power-law exponent, which is significantly influenced by the perturbation mode but generally follows θ > 0.25 (Dimonte, Frerking & Schneider 1995Groom et al. 2020;Weber et al. 2012Weber et al. , 2014Mohaghar et al. 2017Mohaghar et al. , 2019Zhuo 2007). Recently, the extended multi-mode wave-packet model developed by Dimonte et al. (2024), incorporating dynamic saturation and logarithmic growth, has successfully described the transition from linear to nonlinear power-law growth in the RM instability with broadband perturbations, demonstrating its validity across a wide range of parameters. ...

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Modelling the evolution of Richtmyer-Meshkov mixing width during shock compression phases

... Other research programs described in the literature for undergraduates include interdisciplinary research for medicine, biology, and computer science [16,17], teaching research skills during a summer program [18], online research programs [19], and alternative roadmaps for STEM doctoral candidates [20]. Our program set up follows in the footsteps of interdisciplinary research programs, however it is novel from prior works, focusing on project-based learning, applying AI to the topic of health misinformation with a diverse set of undergraduates students across many majors. ...

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Multidisciplinary Engagement of Diverse Students in Computer Science Education through Research Focused on Social Media COVID-19 Misinformation

... However, due to the limitations of their numerical method, the study used the stiffened gas equations of state for n-dodecane, which did not account for the thermodynamic effects of real fluids, and only a two-dimensional cylindrical configuration was discussed. Additionally, Tarey et al. 39 conducted detailed numerical simulations of the deformation and breakup behavior of ndodecane droplets under shock waves at Mach 5, focusing on the phase change effects induced by chemical reactions and evaporation. The study showed that in the presence of evaporation, a recondensed vapor layer forms around the droplet surface, which helps suppress the growth of surface Kelvin-Helmholtz (KH) instability waves. ...

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Three-dimensional numerical simulations of phase change effects on shock-droplet interactions

... The first is Lagrangian particle tracking (LPT), wherein discrete liquid particles in a Lagrangian reference frame interact with the surrounding gaseous flow, which is simulated in the Eulerian reference frame. This approach is commonly used to study spray combustion and full-scale propulsion devices [36][37][38], but its predictive capabilities are often limited by its need for heat transfer, evaporation, and breakup models [39,40]. The second type of numerical approach encompasses interface-tracking techniques, such as level set or ghost-fluid methods, where liquid-gas interfaces are represented as discontinuities within the flow [41][42][43]. ...

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Numerical Simulation of Reacting and Non-Reacting Liquid Jets in Supersonic Crossflow

... Traditional BEMT procedures discretize each rotor disk into radial sections and assume that the turbine is operating in uniform flow. To model a rotor's response in a spatially varying flow, a new radiallyazimuthally discretized BEMT method (RAD-BEMT) was developed [15], in which the rotor disk was discretized into polar area components and the traditional BEMT procedure was applied to each individual radial-azimuthal element. RAD-BEMT was applied to the back rotor to model the back rotor's performance within the nonuniform wake of the front rotor. ...

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Demonstration of a Towed Coaxial Turbine Subscale Prototype for Hydrokinetic Energy Harvesting in Skew

... Among these, researchers favor the LS method because of its local smoothness. For the evolution of the flow field near the interface, the ghost fluid method (GFM, [42][43][44][45]) is a SIM widely used to treat cells near the interface owing the simplicity of the algorithm. This method originated in a study by Fedkiw et al. ( [4]), where a ghost fluid was added with a fixed isobaric hypothesis to maintain the uniformity of the interpolation stencil near the interface. ...

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A Conservative Sharp-Interface Numerical Method for Two-dimensional Compressible Two-phase Flows

... A two-point spectral closure model [23,24] modified from the constant-density BHRZ model [25] for variable-density flows was analyzed for the buoyancy-driven variable-density homogeneous turbulence [26]. The model with minimal augmentation was further assessed for the RTI turbulence [27]. In addition to the BHR family of models, there are also similar models for turbulent mixing such as the second-moment model by Grégoire et al. [28] with a Boussinesq approximation and the k-L-a model by Morgan and Wickett [29] extended from the k-L model [30]. ...

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Analysis of second moments and their budgets for Richtmyer-Meshkov instability and variable-density turbulence induced by reshock

... The Rayleigh-Taylor (RT) instability is a fundamental hydrodynamic phenomenon that occurs when a denser fluid is accelerated against a lighter fluid, resulting in the formation of coherent structures such as bubbles and spikes, enhanced mixing, and eventually turbulent flows [2][3][4][5][6]. This instability plays a pivotal role in a wide range of scientific and engineering phenomena, including supernova explosion [7][8][9], inertial confinement fusion [10][11][12], and combustion [13][14][15]. ...

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Evolution of Rayleigh-Taylor turbulence under vorticity and strain-rate control

... The fuel is combusted by one or a few RDWs inside the annular 9 or hollow 10,11 combustor. The RDWs may be co-rotating 12 or counter-rotating 13 . Longitudinal pulsed detonations and RDWs occur alternately if the pressure ratio between the air plenum and detonation channel is low 14 . ...

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Experimental study of sharp noise caused by rotating detonation waves

... For example, detailed geometric information of the interface avails many predicative models of bubble and spike growth of singlemode RT in the highly nonlinear stage, 26 while the interfacial dynamics controls many physical and chemical processes occurring at the interface, such as mass ablation in inertial confinement fusion and fuel/oxidizer mixing and reaction in combustion chambers. 46 In the following, we first provide details on the numerical simulation of RT flows and the Lagrangian tracking approach. Next, we perform statistical analysis on Lagrangian velocity, acceleration, curvature, etc., focusing on different stages and different regions of singlemode RT. ...

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Lagrangian investigation of the interface dynamics in single-mode Rayleigh–Taylor instability