Dynamic Properties of Steel Catenary Riser near Touchdown Point Under Coplanar Vessel Heave and Vortex Induced Vibration

The present study establishes a simple numerical model for the coupled response of a steel catenary riser(SCR) subjected to coplanar vessel motion and vortex-induced vibration(VIV). Owing to the large deflection of the SCR, the geometric nonlinearity is considered in this model. The hydrodynamic force comprises the excitation force and hydrodynamic damping, where the excitation force that only exists when the non-dimensional frequency is located in the lock-in range, is associated with the VIV. The hydrodynamic force model is validated based on the published VIV test data.As for the seabed resistance at the touchdown zone(TDZ), integrated with an initial seabed trench, the hysteretic feature is modeled. Based on the model, the study emphasizes on the coupled response characteristics near the touchdown point(TDP) induced by coplanar vessel heave and VIV, and analyzes the sensitivity of the coupled response to the heaving amplitude and frequency. It is found that with the increase of the heave amplitude and frequency, the VIV can be obviously mitigated, but the heave-related response in the coupled analysis seems to be close to that in the heave-only simulation. Finally, the fatigue damage near TDP is parametrically investigated based on the separate analysis and the coupled analysis. The results demonstrate that the coupled effect plays a significant role in the fatigue assessment near TDP. Besides, the proportion of the coupled effect accounting for the total fatigue damage decreases with the increasing seabed stiffness, while increases with the increasing seabed trench depth.

溶菌酶在桑葚果酒中的应用研究

溶菌酶与SO_(2)均有杀菌作用,为探究溶菌酶在桑葚果酒酿造中的应用效果,分别在桑葚果酒酿造过程中添加溶菌酶和SO_(2)进行对比。通过跟踪测定桑葚果酒在主发酵和后发酵过程中溶菌酶和SO_(2)对酒精度、总酸、还原糖、花青素、多酚、黄酮、色度、菌落总数和酵母菌数量等指标的影响,探讨溶菌酶和SO_(2)对桑葚果酒发酵进程及品质的影响,得出除了花青素、黄酮溶菌酶组均高于SO_(2)组,其余指标两组相差不大。结果显示与SO_(2)相比溶菌酶不仅不影响果酒前期酒精度上升,还能减少果酒发酵过程中功能性成分的损失,保留其含量。此研究为桑葚果酒生产过程中利用溶菌酶替代SO_(2)提供了基础研究。

船舶区域舱室复合环境综合评价方法研究

舱室环境直接影响船舶居住性和船员舒适性,可以此为切入点通过环境评价来验证布置方案的合理性。该文通过对舱室温度、光照、通风和噪声的分析,明确了舱室环境因子的影响原则,并在此基础上引入模糊数学理论,建立综合评价数学模型并进行验证。结果表明:模糊综合评价方法能较好反映区域舱室复合环境状况的好坏,为舱室布置提供客观的数据支撑。

航行要素对坞舱水深分布及船尾流场特性的影响

带坞舱船舶作为一种相对较为特殊的船型,主要通过沉浮作业将坞舱与外界水域直接相连,达到快速进出舟艇、车辆的目的。正是因为其湿坞作业时会形成半开敞水域,当母船以一定航速前进时将对坞舱内水深分布和坞舱口尾流区域产生明显的影响,需要事先进行预报评估避免因水深估计不足造成内部舟艇搁浅、碰顶等问题的发生。通过建立带尾跳板及坞舱的母船几何模型,并引入螺旋桨体积力法考虑螺旋桨对尾流场的影响,开发螺旋桨转速自适应调节程序,形成带坞舱船舶匀速运动数值仿真模型。研究不同航速及尾跳板攻角下舱内水深分布及船尾流动情况,开展半开敞水域水体流动特征机理分析。数值仿真结果表明:坞舱内水体运动达到稳定后的水位低于平均自由面;母船航速越高舱内水位越低;跳板攻角越大舱内水体稳定性越差。研究成果能为带坞舱船舶的设计提供参考,同时为浮式装备进出坞的作业安全性评估提供技术手段。