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15. Zhu, Y., Liu, L., Han, T., Feng, Q., Moored, K., Zhong, Q. & Quinn, D. (2025) Wavenumber affects the lift of ray-inspired fins near a substrate. Under Review.
Rays and skates tend to have different fin kinematics depending on their proximity to a ground plane such as the sea floor. Near the ground, rays tend to be more undulatory (high wavenumber), while far from the ground, rays tend to be more oscillatory (low wavenumber). Here we show that near the ground, the time-averaged lift on a ray-like fin is highly dependent on wavenumber.
14. Upfal, I., Zhu, Y., Handy-Cardenas, E. & Breuer, K. (2025) Shape-morphing membranes augment the performance of oscillating foil energy harvesting turbines. Phys. Rev. Fluids, 10(3), 034702
Editors' Suggestion.
This work seeks to understand a) the performance of compliant membrane OFTs over their full kinematic parameter space and b) separate the roles of membrane camber and extensibility in LEV stabilization.
13. Zhu, Y. & Breuer, K. (2025) A data-driven approach for modeling large-amplitude flow-induced oscillations of elastically mounted pitching wings. J. Fluids Struct., 134, 104282
We propose and validate a data-driven approach for modeling large-amplitude flow-induced oscillations of elastically mounted pitching wings.
12. Qing, H., Guo, J., Zhu, Y., Chi, Y., Hong, Y., Quinn, D., Dong, H. & Yin, J. (2024) Spontaneous snapping-induced jet flows for fast, maneuverable surface and underwater soft flapping swimmer. Sci. Adv., 10(49), eadq4222
Featured on Science Magazine and Science Advances.
It remains a grand challenge to combine fast speed, high efficiency, and high maneuverability in a single soft swimmer while using simple actuation and control. Here, we report leveraging spontaneous snapping stroke in the monostable flapping wing of a manta-like soft swimmer to address the challenge.
Selected media coverage:
NCSU News: Manta Rays Inspire the Fastest Swimming Soft Robot Yet
New York Post: Bizarre ‘swimming robot’ was inspired by manta rays
Popular Science: This Manta ray robot is the world’s fastest soft-bodied swimmer
Space Daily: Manta ray-inspired soft robot sets new speed record
11. Handy-Cardenas, E., Zhu, Y. & Breuer, K. (2024) Optimal Kinematics for Energy Harvesting Using Favorable Wake-Foil Interactions in Tandem Oscillating Hydrofoils. Under Review.
The energy harvesting performance of a pair of oscillating hydrofoil turbines in tandem configuration is experimentally studied to determine the optimal kinematics of the array.
10. Zhu, Y. & Breuer, K. (2023) Flow-induced oscillations of pitching swept wings: Stability boundary, vortex dynamics and force partitioning. J. Fluid Mech., 977, A1
Software: Force and moment partitioning influence potential solver 3D
We experimentally study the aeroelastic instability boundaries and three-dimensional vortex dynamics of pitching swept wings, with the sweep angle ranging from 0 to 25 degrees.
9. Zhu, Y., Lee, H., Kumar, S., Menon, K., Mittal, R. & Breuer, K. (2023) Force moment partitioning and scaling analysis of vortices shed by a 2D pitching wing in quiescent fluid. Exp. Fluids, 64, 158
Software: Force and moment partitioning influence potential solver 2D
We experimentally study the dynamics and strength of vortices shed from a NACA 0012 wing undergoing sinusoidal pitching in quiescent water.
8. Guan, Y., Zhu, Y., Yang, Z., Yin, B., Gupta, V. & Li, L. K. B. (2023) Multifractality and scale-free network topology in a noise-perturbed laminar jet. J. Fluid Mech., 972, A6
We present experimental evidence of multifractality and scale-free network topology in a noise-perturbed laminar jet operated in a globally stable regime, prior to the critical point of a supercritical Hopf bifurcation and prior to the saddle-node point of a subcritical Hopf bifurcation.
7. Lee, H., Simone, N., Su, Y., Zhu, Y., Ribeiro, B. L. R., Franck, J. A. and Breuer, K. (2022) Leading edge vortex formation and wake trajectory: Synthesizing measurements, analysis, and machine learning. Phys. Rev. Fluids, 7(7), 074704
Support vector regression and Gaussian process regression are used to create regression models that predicts the vortex strength, shape, and trajectory during growth and after separation.
6. Zhu, Y., Mathai, V. & Breuer, K. (2021) Nonlinear fluid damping of elastically mounted pitching wings in quiescent water. J. Fluid Mech., 923, R2
We experimentally study the nonlinear fluid damping of a rigid but elastically mounted pitching wing in the absence of a free-stream flow. A universal fluid damping scaling is proposed to incorporate pitching frequency, pitching amplitude, pivot location and sweep angle.
5. Zhu, Y., Su, Y. & Breuer, K. (2020) Nonlinear flow-induced instability of an elastically mounted pitching wing. J. Fluid Mech., 899, A35
We study the nonlinear flow-induced instability of a cyber-physically mounted pitching wing in a water tunnel, and report two distinct oscillation modes, namely a structural mode, which occurred via a subcritical bifurcation and was associated with a high inertia, and a hydrodynamic mode, which occurred via a supercritical bifurcation and was associated with a low inertia.
4. Zhu, Y., Gupta, V. & Li, L. K. B. (2019) Coherence resonance in low-density jets. J. Fluid Mech., 881, R1
We report the first experimental evidence of coherence resonance (CR) in a hydrodynamic system, a low-density jet capable of undergoing both supercritical and subcritical Hopf bifurcations.
3. Lee, M., Zhu, Y., Li, L. K. B. & Gupta, V. (2019) System identification of a low-density jet via its noise-induced dynamics. J. Fluid Mech., 862, 200-215
We perform system identification of a low-density jet using measurements of its noise-induced dynamics in the unconditionally stable regime, prior to both the Hopf and saddle-node points.
2. Murugesan, M., Zhu, Y. & Li, L. K. B. (2019) Complex network analysis of forced synchronization in a hydrodynamically self-excited jet. Int. J. Heat Fluid Flow, 76, 14-25
In this study, we use complex networks to analyze and forecast these two routes to synchronization in a prototypical self-excited flow – an axisymmetric low-density jet at an operating condition close to its first Hopf point.
1. Zhu, Y., Gupta, V. & Li, L. K. B. (2017) Onset of global instability in low-density jets. J. Fluid Mech., 828, R1
In low-density axisymmetric jets, global instability depends on the density ratio (S), initial momentum thickness (θ), and Reynolds number (Re). Jets become oscillatory when Re exceeds a critical value (ReH). This study finds a bistable region (ReSN < Re < ReH), indicating subcritical bifurcation. A universal scaling for ReH supports the concept of universal global modes in low-density jets.
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