More Like this

1. Wave-by-Wave Control of a Wave Energy Converter with Deterministic Wave Prediction

   Korde, Umesh A. (September 2017, European Wave and Tidal Energy Conference)

   This paper discusses wave-by-wave near-optimal control of a wave energy device in irregular waves. A deterministic propagation model is used to predict the wave elevation several seconds into the future at the device location. Two prediction approaches are considered. The first is based on a time series being measured over an advancing time window at a particular up-wave location. This approach is here utilized in long-crested irregular waves. The second approach uses successive snapshots of wave elevation measurements over an up-wave area. This approach is found more convenient for multi-directional waves, and is here applied in a bi-directional wave irregular wave field. A small, heaving vertical cylinder reacting against a deeply submerged (i.e. assumed to undergo negligible oscillations) mass is studied under wave-by-wave control. The non-causal feedforward control force required for optimum velocity under a swept-volume constraint is based on the past, current, and predicted wave elevation at the device. Results for time-averaged converted power and displacement/force maxima are obtained for a range of irregular wave conditions. Also presented in addition are energy conversion results with a feedback-alone control force using a multi-resonant control technique. 

   more » « less
2. Gravitational wave memory and the wave equation

   https://doi.org/10.1088/1361-6382/ac7203  

   Garfinkle, David (June 2022, Classical and Quantum Gravity)

   Abstract Gravitational wave memory and its electromagnetic analog are shown to be straightforward consequences of the wave equation. From Maxwell’s equations one can derive a wave equation for the electric field, while from the Bianchi identity one can derive a wave equation for the Riemann tensor in linearized gravity. Memory in both cases is derived from the structure of the source of those wave equations. 

   more » « less
3. Impacts of Limited Model Resolution on the Representation of Mountain Wave and Secondary Wave Dynamics in Local and Global Models: 2. Mountain Wave and Secondary Wave Evolutions in the Thermosphere

   https://doi.org/10.1029/2021JD036035  

   Fritts, David C.; Lund, Adam C.; Lund, Thomas S.; Yudin, Valery (May 2022, Journal of Geophysical Research: Atmospheres)
4. Full-wave modeling of EMIC wave packets: ducted propagation and reflected waves

   https://doi.org/10.3389/fspas.2023.1251563  

   Hanzelka, Miroslav; Li, Wen; Ma, Qianli; Qin, Murong; Shen, Xiao-Chen; Capannolo, Luisa; Gan, Longzhi (October 2023, Frontiers in Astronomy and Space Sciences)

   Electromagnetic ion cyclotron (EMIC) waves can scatter radiation belt electrons with energies of a few hundred keV and higher. To accurately predict this scattering and the resulting precipitation of these relativistic electrons on short time scales, we need detailed knowledge of the wave field’s spatio-temporal evolution, which cannot be obtained from single spacecraft measurements. Our study presents EMIC wave models obtained from two-dimensional (2D) finite-difference time-domain (FDTD) simulations in the Earth’s dipole magnetic field. We study cases of hydrogen band and helium band wave propagation, rising-tone emissions, packets with amplitude modulations, and ducted waves. We analyze the wave propagation properties in the time domain, enabling comparison within situobservations. We show that cold plasma density gradients can keep the wave vector quasiparallel, guide the wave energy efficiently, and have a profound effect on mode conversion and reflections. The wave normal angle of unducted waves increases rapidly with latitude, resulting in reflection on the ion hybrid frequency, which prohibits propagation to low altitudes. The modeled wave fields can serve as an input for test-particle analysis of scattering and precipitation of relativistic electrons and energetic ions. 

   more » « less
5. Wellposedness, spectral analysis and asymptotic stability of a multilayered heat-wave-wave system

   Avalos, George; Geredeli, Pelin G.; Muha, Boris (November 2020, Journal of differential equations)

   null (Ed.)