排序方式: 共有180条查询结果,搜索用时 15 毫秒
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基于CFD的拖式吊舱推进器斜流状态下数值模拟 总被引:2,自引:0,他引:2
采用FLUENT软件计算了某拖式吊舱推进器在直航以及斜流状态下的水动力性能.采用滑移面网格方法以模拟桨叶、支架、以及舱体之间的非定常干扰.文中首先计算了直航时不同进速系数下的桨叶推力系数、扭矩系数,并与实验结果进行了对比.计算了在不同斜流角(15°、30°、45°)、不同载荷系数时桨叶本身的推力系数、扭矩系数、侧向力系数与直航时(0°)的比较.文中还讨论了支架、舱体在直航以及不同斜流角时的侧向力问题,并将其大小与桨叶本身产生的侧向力进行了比较,部分计算结果与已有的实验值进行了比较、分析. 相似文献
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Surf-riding/broaching is one of the five stability failure modes to be included into the International Maritime Organization (IMO) second generation intact stability criteria (which are risk-based stability criteria) that can ensure the safety of ships in actual seaways more effectively. This study focuses on the influence of wave surge force prediction accuracy on surf-riding/broaching vulnerability criterion check result. Firstly, it is demonstrated that the wave surge force prediction method adopted in the current vulnerability criterion check procedure is not accurate and may lead to wrong conclusions. The experimental data from captive model test and the numerical result based on 3D panel method both indicate that the diffraction effect must be considered to correctly predict the wave surge forces. Besides, sophisticated methods are not suitable for Level 2 vulnerability criterion check due to their complexity. Therefore, an empirical formula for wave surge force correction based on sample ship calculation results is proposed. The proposed empirical correction formula can effectively improve the vulnerability criterion check accuracy and thus contribute to the design and safety of the ships which are vulnerable to this stability failure mode. 相似文献
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分布式电源系统在启动时,会面临级联电路带来的母线电压振荡及异常工作电压等稳定性问题,因此需要进行针对性设计和改进。本文针对两级Buck电路级联电源系统,基于功率守恒原理建立大信号系统模型,直观地分析了系统启动过程中各个模块软启动工作原理及出现关断重启现象的原因,并推导出级联电源系统启动稳定性的关键参数公式。接着对系统进行行为级建模仿真,在满足电路性能需求的基础上,验证了通过合理设置两级电源输出电容、负载电源启动点、系统软启动时间等以符合启动稳定性参数公式,可保证分布式电源系统的启动稳定性。 相似文献
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对KCS的船首和船尾型线优化开展研究。船体采用径向基函数描述,艏部型线以减小总阻力为目标,艉部型线则侧重于降低尾流不均匀度,以期提高推进效率。在优化过程中,利用基于拉丁超立方采样点构建Kriging近似模型替代直接计算流体力学(CFD)模拟。分别采用多岛遗传算法和非支配排序遗传算法-Ⅱ开展单目标和多目标优化,避免优化的早熟。结果表明,在服务航速下,优化船型的总阻力降低了1.36%,优化船型的伴流目标函数降低了10.2%。在此基础上,进一步针对优化过程中产生的3个优化船型以及原始船型,选用KP505桨进行自航模拟,结果显示虽然阻力有些许增大,但伴流不均匀度明显降低的优化船型的推进效率更优,相对于原始船型,其推进效率最高提升了1.08%。 相似文献