arXiv subjects

Enrique M. Padilla

Publications and source records attributed to Enrique M. Padilla.

5 recordsLinked to original sources

arXiv2026

Breaking-induced energy dissipation of surface gravity waves at varying scales and co-flowing wind stresses

Breaking-induced energy dissipation is studied for individual unsteady breaking waves using laboratory measurements of unidirectional surface gravity wave groups across a range of wave scales and wind stresses. A refined framework to estimate breaking-induced dissipation $ΔE_{br}$ is proposed that accounts for background dissipation from non-breaking processes. Using this framework, we show that variations in wave scale primarily influence breaking energetics, such as fractional dissipation $ΔE_{br}/E_0$ and dissipation rate $ε_b$, by modifying the breaking onset threshold. Also, co-flowing wind systematically reduces both $ΔE_{br}/E_0$ and $ε_b$ relative to unforced conditions, as wind-forced waves break earlier with reduced crest forward-leaning. Exploiting the crest-front steepness at incipient breaking $\mathcal{S}_{\text{front}}(t_b)$ to characterise breaking onset and local crest geometry, we formulate a scaling for $ε_b$ based on this local measure. This then yields $ΔE_{br}/E_0 \propto β^{*}\,\mathcal{S}_b\,(τ_b/T_b)$, where $β^{*}$ is crest forward leaning, $\mathcal{S}_b$ local steepness, and $τ_b/T_b$ non-dimensional breaking duration. This scaling highlights the important roles of crest asymmetry and breaking duration in setting the breaking energy dissipation. Finally, we consider the breaking strength parameter $b$ by assessing existing steepness-based scaling laws, and relate $b$ to $\mathcal{S}_{\text{front}}(t_b)$, yielding an approximately linear dependence once the breaking-onset threshold is considered.

physics.flu-dyn↗

arXiv2026

On the limiting geometry of unsteady breaking waves subject to co-flowing wind: spectrally-informed versus locally-measured steepness

Wave steepness is a key geometric variable for describing breaking occurrence and its consequences, including energy dissipation and air entrainment. Using three laboratory campaigns under varying spectral conditions and co-flowing wind forcing, we contrast two types of steepness commonly used for unsteady breaking waves: spectrally-informed wave-group steepness (prognostic), obtained from fixed-point surface-elevation records, and locally-measured crest steepness (diagnostic), obtained from spatial surface profiles extracted using the SDBW-I image-processing method developed herein. For the former, the long-adopted $\mathcal{S}_n$ (linear sum of Fourier-component steepness) increases appreciably within about two dominant wavelengths upstream of breaking because of its sensitivity to evolving high-frequency content. When measured sufficiently far upstream, however, wave-group steepness remains approximately linearly related to the local zero-crossing steepness $\mathcal{S}_b$ across bulk unforced conditions. Notwithstanding this, we argue that the crest-front steepness, $\mathcal{S}_{\mathrm{front}}(t_b)$, which delineates the front-face slope at incipient breaking, is the most physically meaningful metric examined here. It exhibits a consistent breaking-onset lower-bound threshold of $\mathcal{S}_{\mathrm{front}}(t_b)\approx0.2$, while values above this threshold decrease with wind speed as crests become less forward leaning. This may be attributed to wind-modified dispersion, enhanced high-frequency spectral content and aerodynamic sheltering, suggesting that wind--wave and wave--wave interactions act as competing mechanisms in triggering breaking through kinematic and energetic processes beyond what geometry alone can explain. Even so, $\mathcal{S}_{\mathrm{front}}(t_b)$ has strong potential as a controlling variable for future studies of breaking energetics and crest-scale dynamics.

physics.flu-dyn↗

arXiv2025

Physics-informed neural networks for phase-resolved data assimilation and prediction of nonlinear ocean waves

The assimilation and prediction of phase-resolved surface gravity waves are critical challenges in ocean science and engineering. Potential flow theory (PFT) has been widely employed to develop wave models and numerical techniques for wave prediction. However, traditional wave prediction methods are often limited. For example, most simplified wave models have a limited ability to capture strong wave nonlinearity, while fully nonlinear PFT solvers often fail to meet the speed requirements of engineering applications. This computational inefficiency also hinders the development of effective data assimilation techniques, which are required to reconstruct spatial wave information from sparse measurements to initialize the wave prediction. To address these challenges, we propose a novel solver method that leverages physics-informed neural networks (PINNs) that parameterize PFT solutions as neural networks. This provides a computationally inexpensive way to assimilate and predict wave data. The proposed PINN framework is validated through comparisons with analytical linear PFT solutions and experimental data collected in a laboratory wave flume. The results demonstrate that our approach accurately captures and predicts irregular, nonlinear, and dispersive wave surface dynamics. Moreover, the PINN can infer the fully nonlinear velocity potential throughout the entire fluid volume solely from surface elevation measurements, enabling the calculation of fluid velocities that are difficult to measure experimentally.

cs.LG↗

arXiv2023

Non-newtonian wind-driven flows in homogeneous semienclosed basins

Wind-driven flow in power-law viscous fluids in homogeneous semienclosed basins is analyzed. Analytical solutions for vertical current profiles for non-newtonian fluids with different power-law indexes are derived assuming a wind shear stress at the surface and zero net transport. Previous classical solutions for wind-driven flows in semienclosed basins are thus generalized. A bidirectional flow in the fluid column is obtained: downwind near the surface and a weaker compensating upwind flow near the bottom. Shear-thickening fluids exhibit larger maximum currents at the surface, although reducing the difference between the maximum current at the surface and the maximum current near the bottom, than newtonian and shear-thinning fluids. The larger the flow behavior index n of the power-law, the more acute the effects. For the same physical conditions (depth, wind shear stress, and flow consistency index), the opposite occurs for shear-thinning fluids. The lower the n value the lower the current at the surface and the larger the differences between the upper and lower layer.

physics.flu-dyn↗

arXiv2022

German to Spanish translation of Einstein's work on the formation of meanders in rivers

In 1926 Albert Einstein gave a clear explanation of the physical processes involved in the meander formation and evolution in open channels (Einstein, 1926). Although this work is far from being recognized as one of his greatest achievements, such as his annus mirabilis papers in 1905, he shows a truly remarkable didactic skills that make it easy to understand even to the non-specialist. In particular, a brilliant explanation of the tea leaf paradox can be found in this paper of 1926, presented as a simple experiment for clarifying the role of Earth rotation and flow curvature in the differential river banks erosion. This work deserves to be considered as a pioneering work that has laid a basic knowledge in currently very active research fields in fluvial geomorphology, estuarine physics, and hydraulic engineering. In response to the curiosity aroused and transmitted to the authors over the years by undergraduates and MSc. students, and also due to its historical and scientific significance, we present here the Spanish translation of Einstein's original work published in German in 1926 in Die Naturwissenschaften (Einstein, 1926). Einstein's drawings have not been interpreted, but just updated preserving their original spirit.

physics.hist-ph↗