About

Ranga Narayanan is a Distinguished Professor in the Department of Chemical Engineering at the University of Florida. His research focuses on the transport of heat, mass, and momentum, particularly in relation to spatial and temporal pattern formation during processes such as additive manufacturing of metals, bulk crystal growth of semiconductors, thin film growth during evaporation, and electroplating. He examines the physics of spontaneous spatial pattern generation in processes involving solidification, electrodeposition, resonance, and free-surface convection, with a specific interest in instabilities of parent states as control parameters change. His work employs mathematical methods related to bifurcation theory, non-linear energy methods, and perturbation techniques, complemented by experimental techniques including flow sensing via infrared imaging, shadowgraphy, and electrochemical titration. Dr. Narayanan has made significant contributions to understanding instabilities in fluid flows and material processing, and his research has applications in earth-based and microgravity environments.

Research topics

• Physics
• Thermodynamics
• Mechanics
• Composite material
• Materials science
• Chemistry
• Classical mechanics
• Optics
• Condensed matter physics
• Optoelectronics
• Quantum mechanics
• Mathematics
• Geometry

Selected publications

• Knowing Thermo-Physical Properties For Space Manufacturing

  SPACE · 2026-04-29

  article1st authorCorresponding

  Future space manufacturing, thermal management, and life-support technologies depend on reliable thermophysical property data. Quantities such as viscosity, surface tension, thermal conductivity, and diffusion coefficients determine the dynamics of fluids, heat transport, and materials processing under extreme extraterrestrial conditions. Terrestrial methods are often compromised by gravity-driven effects, container interactions, and limited access to interfacial or high-temperature data. Microgravity environments provide an avenue to circumvent these obstacles by enabling container-less processing, interfacial studies, and precise transport measurements. Establishing robust data repositories is essential for predictive models, optimized algorithms, and integration with machine learning. The result will be reduced risk, improved efficiency, and rapid progress in both terrestrial and space-based manufacturing.

  PublisherDOI

• Enhancement of heat transfer using Faraday instability

  Journal of Fluid Mechanics · 2025-08-04

  articleOpen accessSenior author

  This study explores the Faraday instability as a mechanism to enhance heat transfer in two-phase systems by exciting interfacial waves through resonance. The approach is particularly applicable to reduced-gravity environments where buoyancy-driven convection is ineffective. A reduced-order model, based on a weighted residual integral boundary layer method, is used to predict interfacial dynamics and heat flux under vertical oscillations with a stabilising thermal gradient. The model employs long-wave and one-way coupling approximations to simplify the governing equations. Linear stability theory informs the oscillation parameters for subsequent nonlinear simulations, which are then qualitatively compared against experiments conducted under Earth’s gravity. Experimental results show up to a 4.5-fold enhancement in heat transfer over pure conduction. Key findings include: (i) reduced gravity lowers interfacial stability, promoting mixing and heat transfer; and (ii) oscillation-induced instability significantly improves heat transport under Earth’s gravity. Theoretical predictions qualitatively validate experimental trends in wavelength-dependent enhancement of heat transfer. Quantitative discrepancies between model and experiment are rationalised by model assumptions, such as neglecting higher-order inertial terms, idealised boundary conditions, and simplified interface dynamics. These limitations lead to underprediction of interface deflection and heat flux. Nevertheless, the study underscores the value of Faraday instability as a means to boost heat transfer in reduced gravity, with implications for thermal management in space applications.

  PublisherOA PDFDOI

• Thwarting Marangoni instability in a viscoelastic liquid film via parametric forcing

  Physical Review Fluids · 2025-04-17

  articleOpen accessSenior author

  The suppression of Marangoni-driven instability in a heated viscoelastic thin film was investigated under parametric forcing. It was found that, unlike Newtonian systems which exhibit a single-frequency stabilization threshold, an island of stability bounded by two critical frequencies emerges due to fluid elasticity. Stabilization and destabilization were both shown to result from the memory effects imparted by elasticity. A fundamental shift in the conditions for instability suppression was thereby revealed.

  PublisherOA PDFDOI

• Gravitational effects on Faraday instability in a viscoelastic liquid

  Journal of Fluid Mechanics · 2025-05-14

  articleSenior author

  The influence of parametric forcing on a viscoelastic fluid layer, in both gravitationally stable and unstable configurations, is investigated via linear stability analysis. When such a layer is vertically oscillated beyond a threshold amplitude, large interface deflections are caused by Faraday instability. Viscosity and elasticity affect the damping rate of momentary disturbances with arbitrary wavelength, thereby altering the threshold and temporal response of this instability. In gravitationally stable configurations, calculations show that increased elasticity can either stabilize or destabilize the viscoelastic system. In weakly elastic liquids, higher elasticity increases damping, raising the threshold for Faraday instability, whereas the opposite is observed in strongly elastic liquids. While oscillatory instability occurs in Newtonian fluids for all gravity levels, we find that parametric forcing below a critical frequency will cause a monotonic instability for viscoelastic systems at microgravity. Importantly, in gravitationally unstable configurations, parametric forcing above this frequency stabilizes viscoelastic fluids, until the occurrence of a second critical frequency. This result contrasts with the case of Newtonian liquids, where under the same conditions, forcing stabilizes a system for all frequencies below a single critical frequency. Analytical expressions are obtained under the assumption of long wavelength disturbances predicting the damping rate of momentary disturbances as well as the range of parameters that lead to a monotonic response under parametric forcing.

  PublisherDOI

• A digital image processing tool for characterizing dendritic trunks

  Signal Image and Video Processing · 2024-03-11 · 1 citations

  article
  PublisherDOI

• Stabilizing an Adverse Density Difference in the Presence of Phase Change

  Research Square · 2024-01-16

  preprintOpen accessSenior author

  <title>Abstract</title> Given two phases in equilibrium in a porous solid, the heavy phase lying above the light phase in a gravitational field, we stabilize this adverse density arrangement by heating from below and derive a formula for how steep the temperature gradient must be to do this. The input temperature gradient has two effects on the stability of our system. Its effect on the heat convection is destabilizing, its effect on the heat conduction at the surface is stabilizing. By directing our attention to the case of zero growth rate, we obtain the critical value of the input temperature gradient as it depends on the permeability of the porous solid, the density difference across the surface, the distance between the planes bounding our system, and the physical properties. Our problem makes connections to the Benard problem where it has two, one, or no critical points, and to the Rayleigh-Taylor problem where it has no critical points.

  PublisherOA PDFDOI

• Effect of a deep corrugated wall on the natural frequencies and the Faraday instability of a fluid interface

  Physical Review Fluids · 2024-07-15 · 1 citations

  articleSenior author

  The natural frequency of a fluid overlying on a wavy wall in general reduces. This reduction is observed by a shift in the minimum of the Faraday threshold, i.e., in the parametric acceleration versus frequency plot.

  PublisherDOI

• Influence of parametric forcing on Marangoni instability

  Journal of Fluid Mechanics · 2024-02-16 · 5 citations

  articleOpen accessSenior author

  We study a thin, laterally confined heated liquid layer subjected to mechanical parametric forcing without gravity. In the absence of parametric forcing, the liquid layer exhibits the Marangoni instability, provided the temperature difference across the layer exceeds a threshold. This threshold varies with the perturbation wavenumber, according to a curve with two minima, which correspond to long- and short-wave instability modes. The most unstable mode depends on the lateral confinement of the liquid layer. In wide containers, the long-wave mode is typically observed, and this can lead to the formation of dry spots. We focus on this mode, as the short-wave mode is found to be unaffected by parametric forcing. We use linear stability analysis and nonlinear computations based on a reduced-order model to investigate how parametric forcing can prevent the formation of dry spots. At low forcing frequencies, the liquid film can be rendered linearly stable within a finite range of forcing amplitudes, which decreases with increasing frequency and ultimately disappears at a cutoff frequency. Outside this range, the flow becomes unstable to either the Marangoni instability (for small amplitudes) or the Faraday instability (for large amplitudes). At high frequencies, beyond the cutoff frequency, linear stabilization through parametric forcing is not possible. However, a nonlinear saturation mechanism, occurring at forcing amplitudes below the Faraday instability threshold, can greatly reduce the film surface deformation and therefore prevent dry spots. Although dry spots can also be avoided at larger forcing amplitudes, this comes at the expense of generating large-amplitude Faraday waves.

  PublisherOA PDFDOI

• Stabilizing an adverse density difference in the presence of phase change

  Journal of Engineering Mathematics · 2024-06-18

  articleSenior authorCorresponding
  PublisherDOI

• Characterization of oscillation modes in levitated droplets using image and non-image based techniques

  npj Microgravity · 2023-01-18 · 6 citations

  articleOpen accessSenior author

  The dynamics of levitated liquid droplets can be used to measure their thermophysical properties by correlating the frequencies at which normal modes of oscillation most strongly resonate when subject to an external oscillatory force. In two preliminary works, it was shown via electrostatic levitation and processing of various metals and alloys that (1) the resonance of the first principal mode of oscillation (mode n = 2) can be used to accurately measure surface tension and (2) that so-called "higher-order resonance" of n = 3 is observable at a predictable frequency. It was also shown, in the context of future space-based experimentation on the Electrostatic Levitation Furnace (ELF), a setup on the International Space Station (ISS) operated by Japan Aerospace Exploration Agency (JAXA), that while the shadow array method in which droplet behavior is visualized would be challenging to identify the n = 3 resonance, the normal mode n = 4 was predicted to be more easily identifiable. In this short communication, experimental evidence of the first three principal modes of oscillation is provided using molten samples of Tin and Indium and it is subsequently shown that, as predicted, an "image-less" approach can be used to identify both n = 2 and n = 4 resonances in levitated liquid droplets. This suggests that the shadow array method may be satisfactorily used to obtain a self-consistent benchmark of thermophysical properties by comparing results from two successive even-mode natural frequencies.

  PublisherOA PDFDOI

Recent grants

• PIRE: Collaborations with France and Japan on Multiphase Fluid Science and Technologies

  NSF · $3.1M · 2010–2018

• TRAVEL GRANT FOR SEVENTH INTERNATIONAL CONFERENCE AND WORKSHOP ON INTERFACIAL FLUIDS AND TRANSPORT PHENOMENA PROCESSES to be held in Vienna, Austria, between June 23-26, 2014

  NSF · $10k · 2014–2015

• Travel Grant for the fourth international workshop in interfacial fluid mechanics and transport processes-IMA 4

  NSF · $10k · 2008–2009

• Travel Support for U.S. Participants Attending the Eighth Conference of the International Marangoni Association

  NSF · $7k · 2016–2017

• ISS: Gravitational Effects on the Faraday Instability

  NSF · $670k · 2020–2026

Frequent coauthors

• Farzam Zoueshtiagh

  Université de Lille

  46 shared

• L. E. Johns

  University of Florida

  28 shared

• William Batson

  New Jersey Institute of Technology

  21 shared

• Kevin Ward

  Highland Hospital

  18 shared

• Weidong Guo

  16 shared

• Nevin Brosius

  Banaras Hindu University

  15 shared

• A. L. Fripp

  14 shared

• Sakir Amiroudine

  13 shared

Awards & honors

• Fellow of the American Society Gravitational and Space Resea…
• University of Florida Foundation Professorship Award, 2022
• Edmond Safra Professor, Technion, 2019
• University Term Professor, 2018-2021
• Fellow of the American Institute of Chemical Engineers