Dr. Prabhakar Ranganathan
Dr. Prabhakar Ranganathan
Prabhakar Ranganathan leads CReSI, the Computational Rheology for Sustainable Industry group, in the Department of Mechanical and Aerospace Engineering at Monash University. The group works on the flow of polymer solutions, using microstructural theory, large-scale simulation and high-performance computing.
One question runs through all of it. When a dissolved polymer is carried into a strong flow, its chains stretch, relax and reorient, and it is this conformational state, not the composition of the fluid, that sets what happens next. The group builds predictive links between microstructure, flow history and measurable rheology across shear, extensional and mixed flows, and across the unsteady and turbulent flows where conformational history matters most.
Three application areas are currently in focus.
Jets and filaments of viscoelastic polymer solutions. Capillary thinning, breakup and the drop-size distributions that follow, in sprays, coatings, printing and fibre spinning, where better prediction means less wasted material and less spray drift.
Turbulent drag reduction with polymeric additives. How chain stretching in a turbulent flow alters momentum transport, and what that implies for the pumping energy of pipelines, district heating and cooling loops, and other large fluid networks.
Physiologically active polymers in biomedical devices. The conformation-dependent behaviour of blood-borne macromolecules such as von Willebrand factor in the strong and unsteady flows inside circulatory-support devices, where unfolding governs how the molecule is processed and lost.
The methodological theme tying these together is full-stack rheology: developing the theory and computation needed to go from molecular or particulate models, through continuum constitutive equations, to process-level prediction. On the methods side the group works on multiscale simulation and the high-performance computing that supports it. In the longer term, the group is also interested in inverse problems and in physics-informed machine learning for constitutive model discovery, and in semi-autonomous rheology labs that couple experiment design with simulation.
Earlier work in the group examined flagellar propulsion, ciliary flows and other active-matter systems, and this continues to inform the broader perspective on how local driving and interactions produce emergent macroscopic transport.
Prabhakar welcomes PhD students with strong interests in fluid mechanics, soft matter, applied mathematics or scientific computing, and is keen to collaborate with experimentalists working on complex fluids.
Qualifications
- B Tech, Chemical Engineering, Indian Institute of Technology Madras.
- MS, Chemical Engineering, Indian Institute of Technology Madras.
- Ph.D, Chemical Engineering, Monash University.
Expertise
- Rheology
- Viscoelasticity
- Polymer solutions
- Complex fluids
- Mesoscale simulation methods
- Computational Fluid Dynamics
Research Interests
Mesoscale simulations
Computing how conformation and structure respond to flow with methods that resolve the chains and particles themselves: Brownian dynamics and Stokesian dynamics, with hydrodynamic interactions treated directly, together with the coarse-graining that makes such simulations affordable at scale.
- Ganesh A, Vincenzi D, Prabhakar R, Picardo JR. How hydrodynamic interactions alter polymer stretching in turbulence. Physical Review Fluids 11, 053301 (2026).
- Veeraragavan S, Yazdan Parast F, Nosrati R, Prabhakar R. Elastohydrodynamic mechanisms govern beat pattern transitions in eukaryotic flagella. Cell Reports Physical Science 7 (2026).
- Wang HY, Prabhakar R, Ravi Prakash J, Larson RG. Using Brownian dynamics simulations to demystify capillary breakup extensional rheometry (CaBER). Journal of Rheology 69, 641-656 (2025).
- Prabhakar R, Sasmal C, Nguyen DA, Sridhar T, Prakash JR. Effect of stretching-induced changes in hydrodynamic screening on coil-stretch hysteresis of unentangled polymer solutions. Physical Review Fluids 2, 011301 (2017).
- Ramesh KV, Thaokar R, Prakash JR, Prabhakar R. Significance of thermal fluctuations and hydrodynamic interactions in receptor-ligand-mediated adhesive dynamics of a spherical particle in wall-bound shear flow. Physical Review E 91, 022302 (2015).
- Prabhakar R, Sevick EM, Williams DRM. Coarse-graining intramolecular hydrodynamic interaction in dilute solutions of flexible polymers. Physical Review E 76, 011809 (2007).
- Prabhakar R, Prakash JR, Sridhar T. Effect of configuration-dependent intramolecular hydrodynamic interaction on elastocapillary thinning and breakup of filaments of dilute polymer solutions. Journal of Rheology 50, 925-947 (2006).
- Prabhakar R, Prakash JR. Gaussian approximation for finitely extensible bead-spring chains with hydrodynamic interaction. Journal of Rheology 50, 561-593 (2006).
Microstructure-based constitutive modelling
Turning what the chains do into equations a continuum solver can use, and testing those equations against rheometric data in shear, extensional and mixed flows.
- Prabhakar R, Connell JP. To win, a model must thin: capillary thinning as a benchmark complex flow for constitutive models of viscoelastic polymer solutions. arXiv:2607.17197 (2026).
- Prabhakar R, Sasmal C, Nguyen DA, Sridhar T, Prakash JR. Effect of stretching-induced changes in hydrodynamic screening on coil-stretch hysteresis of unentangled polymer solutions. Physical Review Fluids 2, 011301 (2017).
- Prabhakar R, Gadkari S, Gopesh T, Shaw MJ. Influence of stretching induced self-concentration and self-dilution on coil-stretch hysteresis and capillary thinning of unentangled polymer solutions. Journal of Rheology 60, 345-366 (2016).
- Sridhar T, Nguyen DA, Prabhakar R, Prakash JR. Rheological observation of glassy dynamics of dilute polymer solutions near the coil-stretch transition in elongational flows. Physical Review Letters 98, 167801 (2007).
Continuum simulation and process-level prediction
Whole-flow prediction and the measurement geometries that test it: liquid bridges, capillary thinning, and the rheometers built around them.
- Connell J, Rudman M, Prabhakar R. Influence of volume and aspect ratio of liquid bridges on capillary breakup rheometry. Physics of Fluids 34, 033104 (2022).
- McDonnell AG, Jason NN, Yeo LY, Friend JR, Cheng W, Prabhakar R. Extensional viscosity of copper nanowire suspensions in an aqueous polymer solution. Soft Matter 11, 8076-8082 (2015).
- Bhattacharjee PK, McDonnell AG, Prabhakar R, Yeo LY, Friend J. Extensional flow of low-viscosity fluids in capillary bridges formed by pulsed surface acoustic wave jetting. New Journal of Physics 13, 023005 (2011).
Flagellar propulsion and microswimmer suspensions
How a flagellum converts internal power into swimming, what the surrounding fluid takes back, and what a suspension of swimmers does to the rheology of the fluid carrying them.
- Veeraragavan S, Yazdan Parast F, Nosrati R, Prabhakar R. Elastohydrodynamic mechanisms govern beat pattern transitions in eukaryotic flagella. Cell Reports Physical Science 7 (2026).
- Yazdan Parast F, Veeraragavan S, Gaikwad AS, Powar S, Prabhakar R, O’Bryan MK, Nosrati R. Viscous loading regulates the flagellar energetics of human and bull sperm. Small Methods 8, 2300928 (2024).
- Yazdan Parast F, Gaikwad AS, Prabhakar R, O’Bryan MK, Nosrati R. The cooperative impact of flow and viscosity on sperm flagellar energetics in biomimetic environments. Cell Reports Physical Science 4 (2023).
- Castro JO, Abdul Halim MS, Ambattu LA, Rezk AR, Prabhakar R, Nosrati R, Yeo L. Acoustofluidic semen analysis for veterinary male bovine infertility assessment. Flow 3, E6 (2023).
- Powar S, Yazdan Parast F, Nandagiri A, Gaikwad AS, Potter DL, O’Bryan MK, Prabhakar R, Nosrati R. Unravelling the kinematics of sperm motion by reconstructing the flagellar wave motion in 3D. Small Methods 6, 2101089 (2022).
- Nandagiri A, Gaikwad AS, Potter DL, Nosrati R, Soria J, O’Bryan MK, Jadhav S, Prabhakar R. Flagellar energetics from high-resolution imaging of beating patterns in tethered mouse sperm. eLife 10, e62524 (2021).
- McDonnell AG, Gopesh TC, Lo J, O’Bryan M, Yeo LY, Friend JR, Prabhakar R. Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows. Soft Matter 11, 4658-4668 (2015).
- Clark S, Prabhakar R. Effect of helicity on wrapping and bundling of semi-flexible filaments twirled in a viscous fluid. Soft Matter 7, 5536-5539 (2011).
Other active matter
Suspensions and tissues whose constituents drive themselves, and the patterns and stresses that emerge when local activity couples to hydrodynamics or to a deformable substrate.
- Bajpai S, Chelakkot R, Prabhakar R, Inamdar MM. Role of Delta-Notch signalling molecules on cell-cell adhesion in determining heterogeneous chemical and cell morphological patterning. Soft Matter 18, 3505-3520 (2022).
- Imaran M, Inamdar MM, Prabhakar R, Chelakkot R. Cluster and conquer: the morphodynamics of invasion of a compliant substrate by active rods. Soft Matter 17, 7459-7465 (2021).
- Bajpai S, Prabhakar R, Chelakkot R, Inamdar MM. Role of cell polarity dynamics and motility in pattern formation due to contact-dependent signalling. Journal of the Royal Society Interface 18, 20200825 (2021).
- Nagilla A, Prabhakar R, Jadhav S. Linear stability of an active fluid interface. Physics of Fluids 30, 022109 (2018).
- Gloag ES, Turnbull L, Huang A, Vallotton P, Wang H, Nolan LM, et al. Self-organization of bacterial biofilms is facilitated by extracellular DNA. Proceedings of the National Academy of Sciences 110, 11541-11546 (2013).
Other
Work that does not sit under the headings above, mostly collaborations where the contribution was on the modelling or the statistical mechanics.
- Daware SV, Liu ACY, Prabhakar R, Kumaraswamy G. Control of monolayer sheet size and spatial order in colloidal assemblies by drying sessile drops of suspensions on oil layers. Soft Matter 21, 4467-4475 (2025).
- Daware SV, Mondal R, Kothari M, Chowdhury A, Liu ACY, Prabhakar R, Kumaraswamy G. Synthesis and characterization of monolayer colloidal sheets. Langmuir 40, 23198-23208 (2024).
- Amini Horri B, Ranganathan P, Selomulya C, Wang H. A new empirical viscosity model for ceramic suspensions. Chemical Engineering Science 66, 2798-2806 (2011).
- Wang GM, Prabhakar R, Sevick EM. Hydrodynamic mobility of an optically trapped colloidal particle near fluid-fluid interfaces. Physical Review Letters 103, 248303 (2009).
- Sevick EM, Prabhakar R, Williams SR, Searles DJ. Fluctuation theorems. Annual Review of Physical Chemistry 59, 603-633 (2008).
Research Projects
Current projects
Mesoscale simulations
Building simulation codes for Brownian particles and polymer chains with full hydrodynamic and other long-range interactions, in periodic and confined geometries; using them to probe how chain conformation responds to steady, time-dependent, stochastic and turbulent-like flows; and developing efficient algorithms and data structures for large-scale HPC runs, such as fast summation methods, domain decomposition and GPU-friendly kernels.
Microstructure-based constitutive modelling
Constructing constitutive models for polymer solutions and suspensions from statistical mechanics and kinetic theory; calibrating and testing them against rheometric data from the literature and from collaborators, in shear, extensional and mixed flows; and extending them where the microstructure itself evolves with the flow, including thixotropic, elastic and yielding response in structured suspensions.
Continuum simulations and process-level prediction
Developing continuum simulations of complex-fluid flows using finite-volume, finite-element, spectral or meshless methods, and applying them to capillary thinning and breakup, spray atomisation and drop-size distributions, drag-reduced turbulent flows, and the strong unsteady flows inside circulatory-support devices. Analytical techniques such as stability and bifurcation analysis, together with advanced visualisation, are used to interpret both simulation and experiment.
Interdisciplinary Seed Grant
Moira O’Bryan, RP, Julio Soria, David Potter
Monash University, 2016
Supervision
PHD
Aditya Ganesh
Stretching dynamics of linear and ring polymers in extensional and turbulent flow
2022 to 2026
Joe Connell
Understanding the influence of geometric parameters on capillary breakup rheometry using simulations of liquid bridges
2019 to 2026
Santosh Vasant Daware
Synthesis, characterization and application of colloidal sheets
2024 to 2026
Shibani Veeraragavan
Elastohydrodynamic origins of flagellar beat transitions in sperm
2019 to 2023
Supriya Bajpai
Modelling, simulation and analysis of mechanochemical patterns in active tissues
2016 to 2022
Md Imaran
Influence of particle smoothness and substrate mechanics on the clustering of self-propelled rods
2016 to 2022
Ashwin Lakshman Nandagiri
Beating patterns and energetics of sperm flagella
2014 to 2021
Amarender Nagilla
Modelling and simulations of active fluid interfaces
2014 to 2019
Amarin George McDonnell
The acoustically-driven microfluidic extensional rheometer: development, validation, and application to complex low-viscosity fluids
2011 to 2016
Chandi Sasmal
Simulating the flow of semidilute polymer solutions (associate supervisor)
2013 to 2016
Siddharth Gadkari
Viscous liquid jets and filaments in electric fields: stability analysis and role of viscoelasticity (associate supervisor)
2009 to 2013
Masters
Shriram Ravikumar
Experimental investigation of the motility of wildtype and mutant Caenorhabditis elegans using micro-PIV (associate supervisor)
2016 to 2018
Gopesh Chaitanyakumar Tilvawala
Using inertio-viscous stress balances to model the mid-filament dynamics of capillary thinning of Newtonian and non-Newtonian liquid bridges
2013 to 2014
Teaching Commitments
- MEC3451 - Fluid mechanics II
- MMA2003 - Thermofluids
PhD applications
Methods and skills PhD candidates will develop
Depending on your project, you can expect to develop a substantial toolkit, for example:
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Mathematical modelling of complex fluids (continuum and particle-based)
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Statistical mechanics and kinetic theory for polymers and suspensions
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Scientific computing and HPC: writing efficient code (e.g. C/C++/Fortran/Python/MATLAB/Julia), parallelisation, working on clusters
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CFD and numerics: finite-volume / finite-element / spectral / meshless methods, time integration, stability and bifurcation analysis
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Data analysis and visualisation for high-dimensional simulation and experimental data
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Collaborative research skills: working with experimental groups, reading and critiquing the literature, communicating results clearly in talks and papers
This is good preparation for careers in academia, scientific computing, or high-end R&D roles in materials, manufacturing and biomedical technology.
What I am looking for
I am keen to work with students who:
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have a strong background in at least one of: fluid mechanics, soft matter, applied mathematics, statistical mechanics, or computational physics
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are comfortable with programming or willing to learn it seriously
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enjoy thinking carefully about both physics and numerics, not just pushing buttons
Contact
If you are interested in a PhD in this area, please email prabhakar.ranganathan@monash.edu with:
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a short statement of your interests and background
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your CV
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your academic transcripts (unofficial is fine at the initial stage)
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a brief description of any research or substantial coding projects you have done (links to code or reports are helpful)
If there is a good fit, we can then discuss possible projects and scholarship options. It is also really important that applicants familiarize themselves with the admission process at Monash: https://www.monash.edu/graduate-research/study/apply.