Parametric Wave Spectrum Model for Typhoon-Generated Waves Based on Field Measurements in Nearshore Strait Water

The stochastic waves generated by storm landfalls usually determine the design and safety of coastal and offshore structures in typhoon regions. This study developed a parametric wave spectrum model for typhoon-generated stochastic waves that considers the variation in the wave spectrum due to the temporal variation in the typhoon. A field measurement campaign was conducted in nearshore strait water on the east coast of China to measure the wave data for two landfall typhoons: Soudelor and Dujuan. The measured wave data were filtered through a preprocessing framework. The parametric wave spectrum model was then developed based on the measured wave spectra for different stages of the typhoon. The main conclusions include the following: (1) 78% of the measured wave spectra at the example site under a typhoon are double-peaked, and approximately 15% are single-peaked; (2) the parametric model with either the Joint North Sea Wave Project (JONSWAP) or Ochi-Hubble (OH) kernel function is effective in defining the typhoon-generated wave spectra; and (3) the critical parameters of the developed model for typhoon-generated waves are site-specific and depend on the temporal variation of the typhoon.

Strongly coherent dynamics of stochastic waves causes abnormal sea states

<p>The dynamic kurtosis (i.e., produced by the free wave component) is shown to contribute essentially to the abnormally large values of the full kurtosis of the surface displacement, according to the direct numerical simulations of realistic directional sea waves within the HOSM framework. In this situation the free wave stochastic dynamics is strongly non-Gaussian, and the kinetic approach is inapplicable. Traces of coherent wave patterns are found in the Fourier transform of the directional irregular sea waves. They strongly violate the classic dispersion relation and hence lead to a greater spread of the actual wave frequencies for given wavenumbers.</p><p>The research by is supported by the RSF grant No. 16-17-00041.</p><p>Slunyaev, A. Kokorina, The method of spectral decomposition into free and bound wave components. Numerical simulations of the 3D sea wave states. Geophysical Research Abstracts, V. 21, EGU2019-546 (2019).</p><p>A.V. Slunyaev, A.V. Kokorina, Spectral decomposition of simulated sea waves into free and bound wave components. Proc. VII Int. Conf. “Frontiers of Nonlinear Physics”, 189-190 (2019).</p><p>Slunyaev, A. Kokorina, I. Didenkulova, Statistics of free and bound components of deep-water waves. Proc. 14th Int. MEDCOAST Congress on Coastal and Marine Sciences, Engineering, Management and Conservation (Ed. E. Ozhan), Vol. 2, 775-786 (2019).</p><p>Slunyaev, Strongly coherent dynamics of stochastic waves causes abnormal sea states. arXiv: 1911.11532 (2019).</p>

Intrinsic noise, Delta-Notch signalling and delayed reactions promote sustained, coherent, synchronized oscillations in the presomitic mesoderm

Using a stochastic individual-based modelling approach, we examine the role that Delta-Notch signalling plays in the regulation of a robust and reliable somite segmentation clock. We find that not only can Delta-Notch signalling synchronize noisy cycles of gene expression in adjacent cells in the presomitic mesoderm (as is known), but it can also amplify and increase the coherence of these cycles. We examine some of the shortcomings of deterministic approaches to modelling these cycles and demonstrate how intrinsic noise can play an active role in promoting sustained oscillations, giving rise to noise-induced quasi-cycles. Finally, we explore how translational/transcriptional delays can result in the cycles in neighbouring cells oscillating in anti-phase and we study how this effect relates to the propagation of noise-induced stochastic waves.

Atomic Momentum Diffusion in the Field of Counter-Propagating Stochastic Light Waves

The momentum diffusion of atoms in the field of two counter-propagating stochastic waves, one of which reproduces the other one with a certain time delay, has been studied. It is shown that the parameters of atom-field interaction, at which the light pressure force is maximum, correspond to the increasing momentum diffusion coefficient. In the case of high-intensity field described by the stochastic field model, the momentum diffusion coefficient was found to be proportional to the square root of the field autocorrelation time. The wave function describing the inner state of atoms is modeled, by using the Monte-Carlo method. Numerical calculations are carried out for cesium atoms.

Dynamic analysis of parametrically excited marine riser under simultaneous stochastic waves and vortex

This study investigates the dynamic analysis of parametrically excited marine riser under simultaneous stochastic waves and vortex. A general analysis considers the parametric excitation resulting from platform motion, ocean wave loading directly on the rise, and vortex-shedding excitation due to flow bypassing the risers. Stochastic wave force and vortex excitation acting on the riser in the time domain is formulated by the stochastic phase spectrum method and derived by the linear-wave theory using a Pierson–Moskowitz wave spectrum to simulate real sea conditions. A derived parametrically excited top tensioned riser model subjected to simultaneous stochastic waves and vortex excitations is proposed. The efficacy of the present method is assessed by solutions obtained from other existing methods and experimental data of two test models. The present method is evaluated by solutions computed from existing methods and experimental data of two test models, and a general good agreement of the analyses between the proposed approach and other methods is observed. The availability of resonance, parametric stability, energy distribution and transfer, and the sensitivity of key parameters estimated by single-frequency and multi-frequency excitation are compared and discussed. Comparing with the results obtained from the harmonic excitation method, the present method can be used to make more reasonable and accurate calculations of the dynamic response of risers operating in real sea conditions.