Fluids Mechanics and Waves Seminar - Spring 2026
Seminars are held Mondays from 2:30 - 3:30 PM in CULM 611 and/or Zoom, unless otherwise noted.
For questions about the seminar schedule, please contact Thi Phong Nguyen.
Zoom Link for talks: https://njit-edu.zoom.us/j/99973535435?pwd=fUENHPxybbpXp2ImpWuXalrO26ErbP.1
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February 09 (Virtual Talk)
Kunlun Qi, Michigan State University
Fast Fourier spectral method for kinetic equations: from particle to wave
Homepage: https://kunlun-qi.github.io/
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February 23 (Virtual Talk)
Govanni Granados, University of North Carolina (UNC)-Chapel Hill
Recovering elastic subdomains with strain-gradient elastic interfaces from force measurements
In this talk, we introduce a new inverse problem for two-dimensional antiplane shear in elastic bodies with strain-gradient interfaces. The setting is a homogeneous isotropic elastic body that contains an inclusion separated by a thin interface endowed with higher-order surface energy. We show that the Dirichlet-to-Neumann map, which encodes displacement-stress measurements on the exterior boundary, uniquely recovers the mechanical parameters, as well as the shape of the inclusion. To address the inverse shape problem, we adapt the Factorization Method to handle the complications arising from a higher-order boundary operator and its nontrivial null space. Numerical examples will be presented in the unit circle.
Homepage: https://sites.google.com/view/govannigranadosmath/home
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March 09
Ricardo Barros, Loughborough University, UK
Mode-1 and mode-2 internal solitary waves in a three-layer fluid
There are infinitely many propagation modes in a continuously density-stratified fluid. In the ocean, more than 90% of the kinetic energy associated with internal solitary waves (ISWs) resides in the first two baroclinic modes (mode-1 and mode-2). To investigate the main characteristics and complex behaviour of these waves, we consider stratifications featuring a double pycnocline which, when sufficiently sharp, can be effectively approximated by a three-layer fluid system. Within this reduced framework, we provide a comprehensive classification of mode-1 ISWs and reveal the existence of mode-2 ISWs characterised by multi-humped profiles. Our findings are validated through comparison with solutions of the fully nonlinear Euler theory.
Homepage: https://www.lboro.ac.uk/departments/maths/staff/ricardo-barros/
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March 11 (Special Addition)
Alex Doak, University of Bath, UK
Free-surface flows past a point vortex
In this talk, I will present a numerical method for computing free-surface flows in which a point vortex lies inside the domain. We start by revisiting the gravity-free case, where an analytic solution was derived by Gurevich and extended by Shaw. We then demonstrate how to modify the method to include gravity. Finally, we extend the result to include multiple point vortices.
Homepage: https://researchportal.bath.ac.uk/en/persons/alex-doak/
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March 23
Giuseppe Pucci, CNR-Nanotec at the University of Calabria, Italy
Wave-driven active systems at fluid interfaces
Active systems consist of self-driven units that convert energy from their environment into motion or mechanical forces. Their study has motivated efforts to extend statistical mechanics to nonequilibrium systems. Most work to date has focused on two limiting regimes: overdamped systems, such as bacteria and colloids, whose interactions are mediated by viscous flows that decay monotonically with distance, and inertial systems, such as flocks of birds or schools of fish, characterized by complex spatiotemporal interactions.
In this talk, I will review recent work on wave-driven active systems at vibrating fluid interfaces, which operate in an intermediate regime where both viscosity and inertia play important roles. In these systems, interactions are mediated by surface waves and are therefore spatiotemporally oscillatory, leading to collective behaviors that differ qualitatively from those observed in more conventional active matter.
I will first present hydrodynamic spin lattices, an active system composed of droplets that orbit in submerged wells while interacting through the waves they generate on a vibrating bath [1]. The resulting wave-mediated coupling gives rise to emergent collective states with striking analogies to magnetic ordering in electronic systems.
In the second part of the talk, I will introduce recent work on capillary surfers [2,3] and capillary spinners [4], asymmetric solid particles that propel or rotate at a vibrating fluid interface through asymmetric wave generation. Their propulsion speed and interactions can be tuned through particle geometry, fluid properties, and vibration parameters. Surfers interact through their mutual capillary wavefield and exhibit multiple bound states characterized by discrete equilibrium spacings, while spinners display synchronization phenomena arising from wave-mediated coupling.
These systems provide a tunable platform for exploring active matter with oscillatory long-range interactions at intermediate Reynolds numbers.
[1] Sáenz et al. Nature 596, 58 (2021).
[2] Ho et al. Phys. Rev. Fluids 8, L112001 (2023).
[3] Oza et al. Phys. Rev. Fluids 8, 114001 (2023).
[4] Barotta et al. Phys. Rev. E 111, 035105 (2025).
Homepage: https://www.gpucci.net/
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April 06
Uyen Le, Texas A&M University - Corpus Christi
Existence and Stability of Periodic Waves in the Fractional Korteweg de Vries Equation
The fractional Korteweg–de Vries (fKdV) equation models the unidirectional propagation of weakly nonlinear dispersive waves of long-wavelength. The existence of periodic waves in the fKdV equation has been studied using fixed point, perturbative, and variational methods. From the point of view of variational method, the periodic waves are characterized as constrained minimizers of the energy functional subject to fixed mass and momentum. In this talk, we are going to discuss two results regarding the existence and stability of the periodic waves of the fKdV equation. First, we are going to show the existence of positive periodic solution by proving that the Green’s function for the linear operator in the fKdV equation is strictly positive. Second, in the context of variational method, we are going to propose an alternative framework in which the periodic waves are constrained minimizers of the quadratic form of energy subject to fixed cubic part of energy and the zero mean. This new characterization allows us to fully unfold the region of existence of the periodic waves and to establish a sharp stability criteria based on the monotonicity of the map from the wave speed to the wave momentum.
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April 07 (Special Addition)
Pouria Behnoudfar, University of Wisconsin-Madison
Bridging idealized and operational models: an explainable AI framework for Earth system emulators
Computational models are indispensable for understanding complex dynamical systems. High-fidelity operational models offer rich resolution and comprehensive state descriptions but often suffer from persistent biases, particularly in extreme events and long-term statistics. At the other end of the spectrum, coarse-grained idealized models isolate fundamental processes and can be precisely calibrated to excel in characterizing specific dynamical and statistical features. However, different models remain siloed by disciplinary boundaries. In this talk, we present an explainable AI framework that bridges the model hierarchy through a reconfigured latent data assimilation technique, uniquely suited to exploit the sparse output from the idealized models. The resulting bridging model inherits the high resolution and comprehensive variables of operational models while achieving global accuracy enhancements through targeted improvements from idealized models. Crucially, the mechanism of AI provides a clear rationale for these advancements, moving beyond black-box correction to physically insightful understanding in a computationally efficient framework that enables effective physics-assisted digital twins and uncertainty quantification. We demonstrate its power by significantly correcting biases in CMIP6 simulations of El Niño spatiotemporal patterns, leveraging statistically accurate idealized models.
Homepage: https://scholar.google.com/citations?user=Imuw5CMAAAAJ&hl=fa
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April 20
Xin Guan, Imperial College London
Curvature Singularity in Electrified Vortex Sheets
Vortex sheet model is widely used to simulate water/interfacial waves. A famous result of Moore shows that it suffers from finite-time curvature singularity because of the Kelvin-Helmholtz instability. By incorporating surface tension, finite-thickness effect, or vortex blob, the curvature singularity can be successfully suppressed. In this talk, we investigate the dynamics of electrified vortex sheets, i.e. vortex sheets coupling an electric field whose direction is parallel to the undisturbed interface. In electrohydrodynamics, it is well known that horizontal electric fields can stabilise flows, thereby motivating the current study. Our study combines fully nonlinear numerical simulations using boundary integral method and weakly nonlinear models derived using Dirichlet-Neumann operator expansion. Although linear theory shows that there is no Kelvin-Helmholtz instability when the electric field strength Eb exceeds a critical value, we find that curvature singularity persists for any value of Eb. More interestingly, the singularity time follows two distinct scaling laws, depending on Eb. For small values of Eb, we recover the classical logarithm-scaling law found by Moore; for large values of Eb, an algebraic-scaling law is found.
Homepage: https://scholar.google.com/citations?user=N0ISMdYAAAAJ&hl=en
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May 04
Matteo Polimeno, NJIT
Mathematical and Physical Modeling of aggregation dynamics in marine environments
In this talk, I will briefly describe two modeling efforts that aim to characterize the dynamics of marine aggregates. First, I will discuss a Brownian dynamics formulation to model the formation of aggregates in the ocean. I incorporate rotational effects, and size-dependent diffusivities into the well-established framework of Diffusion-Limited Cluster Aggregation, and show how the inclusion of rotational effects lowers the fractal dimension typically found in aggregates, while size-dependent diffusivities slow down their growth rate.
Then, to better understand the processes that may lead to aggregates’ break-ups, I will discuss a boundary integral formulation to solve the Stokes Equations to characterize the internal and external stresses felt by different types of marine aggregates settling under gravity or exposed to some laminar shear flow. I find that the internal stresses induced by gravity distribute differently in aggregates compared to those induced by a shear flow, leading to different breakup distributions. The results of this work can provide insights on how to build a physically-accurate dynamic model of aggregation.
Homepage: https://scholar.google.com/citations?user=Pna2K9wAAAAJ&hl=it
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Last edited: April 27, 2026