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There is a strong real-time coupling between seabed topography and wave field, current field and wind field in shallow water area. The existing analysis model cannot directly consider the influence factors of seabed, and it is more difficult to explain the unsteady evolution mechanism of the coupling field between typical seabed topography and wave, shear flow and gradient wind. Based on the secondary development of STAR-CCM+platform, the shallow sea wind-wave-current numerical pool is constructed under four typical seabed landform conditions: seabed plain, seabed slope, trough, and flat landform. The multi-layer particle velocity coupling method is proposed and the multi-layer wind-wave-current coupling model is established. The wind-wave-current decoupling is realized at the initial time. The temporal and spatial evolution laws of wave field, current field, and wind field in different seabed topographies are compared and analyzed. The principal component analysis method is introduced to evaluate the unsteady effect of wind-wave-current in various typical seabed topographies, and the unsteady evaluation index of the whole life cycle of the wind-wave-current-seabed coupling field is established. The results show that the multi-layer wind-wave-current coupling model can more truly reflect the influence of vertical wind speed and uneven velocity distribution on wave field. The seabed topography can lead to a multi-stage time-history distribution of wave field in the evolution process. The flat topography, submarine slope, and trough conditions are divided into wave surface surge, attenuation, and stability stages. The submarine plain conditions are divided into external breaking wave, internal breaking wave, and climbing stage. The evolution of the current field presents a multi-stage spatial distribution, and the seabed leads to the formation of multi-vortex accumulation or multi-vortex coexistence in the current field. The coupling evolution of wind-wave-current-seabed has an amplification effect on the wind profile index, and positive relationship between seabed height and wind profile coefficient. The end-stage unsteady evaluation indices of flat landform, submarine plain, submarine slope, and trough are 0.268, 4.612, 0.672, and 0.926, respectively.

This paper presents a WENO-based upwind rotated lattice Boltzmann flux solver (WENO-URLBFS) in the finite difference framework for simulating compressible flows with contact discontinuities and strong shock waves. In the method, the original rotating lattice Boltzmann flux solver is improved by applying the theoretical solution of the Euler equation in the tangential direction of the cell interface to reconstruct the tangential flux so that the numerical dissipation can be reduced. The fluxes at each interface are evaluated using a weighted summation of lattice Boltzmann solutions in two local perpendicular directions decomposed from the direction vector so that the stability performance can be improved. To achieve high-order accuracy, both fifth and seventh-order WENO reconstructions of the flow variables in the characteristic spaces are carried out. The order accuracy of the WENO-URLBFS is evaluated and compared with the traditional Lax–Friedrichs scheme, Roe scheme, and the LBFS by simulating the advection of the density disturbance problem. It is shown that the fifth and seventh-order accuracy can be achieved by all considered flux-evaluation schemes, and the present WENO-URLBFS has the lowest numerical dissipation. The performance of the WENO-URLBFS is further examined by simulating several 1D and 2D examples, including shock tube problems, Shu–Osher problems, blast wave problems, double Mach reflections, 2D Riemann problems, K-H instability problems, and High Mach number astrophysical jets. Good agreements with published data have been achieved quantitatively. Moreover, complex flow structures, including shock waves and contact discontinuities, are successfully captured. The present WENO-URLBFS scheme seems to present an effective numerical tool with high-order accuracy, lower numerical dissipation, and strong robustness for simulating challenging compressible flow problems. [ABSTRACT FROM AUTHOR]

The comprehensive examination of typhoon impacts on offshore wind power in Chinese waters, which are prone to severe typhoons, remains largely unexplored. This paper takes a step toward assessing extreme design wind conditions for offshore wind turbines in Chinese waters and investigates typhoon-induced wind conditions considering their spatiotemporal effects. For this purpose, a spatiotemporal analysis framework for typhoons was proposed that includes a data-driven typhoon wind speed field model and estimation method of the extreme wind speed. The wind speed field model introduces a measured correction coefficient to enhance the generalization across various observed typhoons, thereby accurately capturing spatiotemporal typhoon effects. The analysis framework was applied to dozens of typical worst-case scenarios of typhoons passing through offshore wind farms in Chinese waters. These scenarios were selected based on typhoon observation data from the past 30 years. The quantitative analysis assesses and discusses the spatiotemporal impacts of typhoons on the mean wind speed, fluctuating wind speed, extreme wind speed, peak factor, and gust factor. The results indicate significant spatiotemporal impacts of typhoons on the inflow wind speed field. The maximum gust wind speed difference could exceed tenfold at various times or for different turbines. This study offers an interpretation of why wind turbines within the same wind farm may experience varying degrees of damage during identical typhoon attacks. By examining the spatiotemporal variation characteristics of typhoons and the corresponding induced wind speed fields, this paper highlights the significance of these factors for typhoon-resistant design in offshore wind farms, thus aiding in ensuring the structural safety of offshore wind turbines. [ABSTRACT FROM AUTHOR]

In this study, the tallest cooling tower (228 m) completed construction in the world in northwest China was chosen to investigate wind-induced failure mechanism of superlarge cooling towers under tornado. A multiscale finite-element model of the structure was established based on the layered shell element method, and a wind tunnel pressure test was carried out using the tornado simulator. Wind pressure distribution characteristics on inner and outer surfaces of the cooling tower under tornado were analyzed. Moreover, characteristics of the whole wind-induced collapse process of the cooling tower under tornado were studied by combining incremental dynamic analytical method, and the collapse mechanism of a superlarge cooling tower under tornado was extracted. Finally, the failure criterion of the structure under tornado based on the variation rate of the torsion angle was proposed. Results demonstrated that wind pressure showed a circumferential even distribution pattern on the surface of the superlarge cooling tower under tornado, and it generally presented negative pressures. When the cooling tower is located at the tornado vortex core, it is the most dangerous and vulnerable to collapse. Under tornado effects, the cooling tower presented bypassing suction and torsional collapse attitudes from inside to outside. The cooling tower element is designed to improve the antitornado bearing capacity by developing a membrane mechanism. The cooling tower collapsed and failed when the torsion angle failure index φ>0.25. [ABSTRACT FROM AUTHOR]