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“翠洲”轮原是一艘从事长江仪征到栖霞过江运输的简易油船,主机功率较小,航速较低,在给该轮延伸航线改造时,船舶稳性、抗风性方面问题较为突出.通过理论分析和实航研究,解决了上述问题,确保了海上航行的安全.文章对此作了较详细的介绍. 相似文献
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Nonlinear hydrodynamics play a significant role in accurate prediction of the dynamic responses of floating wind turbines (FWTs), especially near the resonance frequencies. This study investigates the use of computational fluid dynamics (CFD) simulations to improve an engineering model (based on potential flow theory with Morison-type drag) by modifying the second-order difference-frequency quadratic transfer functions (QTFs) and frequency-dependent added mass and damping for a semi-submersible FWT. The results from the original and modified engineering models are compared to experimental data from decay tests and irregular wave tests. In general, the CFD results based on forced oscillation tests suggest increasing the frequency-depending added mass and damping at low frequencies compared to first order potential flow theory. The modified engineering model predicts natural periods close to the experimental results in decay tests (within 5%), and the underprediction of the damping is reduced compared to the original engineering model. The motions, mooring line tensions and tower-base loads in the low-frequency response to an irregular wave are underestimated using the original engineering model. The additional linear damping increases this underestimation, while the modified QTFs based on CFD simulations of a fixed floater in bichromatic waves result in larger difference-frequency wave loads. The combined modifications give improved agreement with experimental data in terms of damage equivalent loads for the mooring lines and tower base. 相似文献
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基于有限体积法建立了地铁车站三维静态数值计算模型,对列车阻塞隧道时站台滑动门所受的活塞风压进行了计算研究;分别对单、双两种活塞通风条件下,不同活塞风速、阻塞比、滑动门位置对滑动门所受风压的变化规律进行了分析。结果表明,双活塞通风能够有效减弱活塞风对滑动门的风压;单活塞通风条件下,滑动门在最不利位置时,需克服的最大风压约为230 Pa。 相似文献
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Fatigue damage is one of the governing factors for the design of offshore wind turbines. However, the full fatigue assessment is a time-consuming task. During the design process, the site-specific environmental parameters are usually condensed by a lumping process to reduce the computational effort. Preservation of fatigue damage during lumping requires an accurate consideration of the met-ocean climate and the dynamic response of the structure. Two lumping methods (time-domain and frequency-domain) have been evaluated for a monopile-based 10 MW offshore wind turbine, both based on damage-equivalent contour lines. Fatigue damage from lumped load cases was compared to full long-term fatigue assessment. The lumping methods had an accuracy of 94–98% for the total long-term fatigue damage and 90% for individual wind speed classes, for aligned wind and waves. Fatigue damage was preserved with the same accuracy levels for the whole support structure. A significant reduction of computational time (93%) was achieved compared to a full long-term fatigue assessment. For the cases with 30° and 60° wind-wave misalignment, there was a mean underestimation of approximately 10%. Variations in penetration depth did not affect the selection of the lumped sea-state parameters. This work presents a straightforward method for the selection of damage-equivalent lumped load cases, which can adequately preserve long-term fatigue damage throughout the support structure, providing considerable reduction of computational effort. 相似文献