Experimental Investigation of Propeller Wake Wash

在结冰的沃茨中航行要求船舶能够在自然冰条件下操作，例如破碎的浮冰和完整的水平冰。传统的破冰作业很大程度上依赖于船舶的质量和动力来破冰。船的结构必须相应地坚固。船舶推进技术的最新创新提供了使用螺旋桨尾流作为另一种破冰、清除和以其他方式管理冰的手段的机会。采用螺旋桨尾流的破冰作业可以显著减少传统破冰作业中涉及的船舶结构-冰相互作用，从而减少结构损坏和燃料或货物意外溢出的可能性，并提高作业的能量效率。螺旋桨尾流清洗已经被水手们使用多年，以清除航道上的碎冰，但只是在方位角型推进器出现后，它才被设计纳入操作中。目前，设计是在特设的基础上进行的，因为对螺旋桨下游的尾流如何发展以及随后如何与自由表面处的海冰相互作用的基本理解有限。拟议的研究将解决这一知识差距。* 拟议的研究将根据下游的三维流体速度场（包括自由表面的速度场）来表征螺旋桨尾流。表征将基于实验室实验。实验将在纪念大学海洋工程研究中心的拖曳池中进行。实验将首先集中在没有冰的情况下的螺旋桨尾流，然后集中在尾流和冰的相互作用上。在冰的特点方面，感兴趣的焦点将是浮冰。将建立下游尾流的半经验数学模型，以及自由表面水流与浮冰相互作用之间的相互作用。尾流洗场模型将包括平均速度及其在整个下游尾流中的变化。作为拟议工作的最后一项实验内容，将根据对冰中船舶的实地观察对其进行测试。尾流模型将预测下游表面速度场的关键因素：交付功率，螺旋桨的沉没深度，螺旋桨的倾斜角的自由表面。当与冰相互作用模型耦合时，该模型应预测尾流如何清除螺旋桨下游的积冰。 这将对设计师和运营商有用，例如商业航运，海岸警卫队，海军和其他与运输，勘探和防御有关的冰中航行的人。拟议的研究涵盖了5年的时间跨度。四个硕士生将在这个项目上工作。所有研究生将在论文为基础的学位课程。

Navigation in ice-covered waters requires that vessels be capable of operating in natural ice conditions, such as broken pack ice and intact level ice. Conventional ice-breaking operations rely largely on the mass and power of the vessel to break through ice. The ship's structure must be correspondingly strong. Recent innovations in marine propulsion technology have provided opportunities to use propeller wake wash as another means to break, clear, and otherwise manage ice. Icebreaking operations employing propeller wake wash can reduce significantly the ship structure-ice interaction involved in conventional icebreaking, thereby reducing the likelihood of structural damage and accidental spills of fuel or cargo, and improving the operation's energy efficiency. Propeller wake wash has been used for years by mariners to clear broken ice from shipping channels, but it has only been since the advent of azimuthing types of propulsors that it has been incorporated into operations by design. At present, the design is done on an ad hoc basis as there is limited fundamental understanding of how the wake wash develops downstream of the propeller and subsequently interacts with sea ice at the free surface. The proposed research will address this knowledge gap. *******The proposed research will characterize propeller wake wash in terms of the 3-D fluid velocity field downstream, including the velocity field at the free surface. The characterization will be based on laboratory experiments. Experiments will be done in the tow tank at Memorial University's Ocean Engineering Research Centre. Experiments will focus first on the propeller wake wash in the absence of ice, and then on the interactions of the wake wash and ice. The focus of interest in terms of ice features will be on pack ice. A semi-empirical mathematical model will be developed of the downstream wake, and the interaction between the flow at the free surface and its interaction with pack ice. The model of the wake wash field will include mean velocities, as well as of its variability throughout the downstream wake. It will be tested against field observations of ships in ice, as the final experimental element of the proposed work. The wake model will predict the downstream surface velocity field in terms of key factors: delivered power, depth of submergence of the propeller, and inclination angle of the propeller to the free surface. When coupled to the ice interaction model, the model should predict how wake wash can clear pack ice en masse downstream from the propeller. This will be useful for designers and operators, such as commercial shipping, the Coast Guard, Navy and others who navigate in ice in connection with transportation, exploration and defense.******The proposed research covers a 5 year time span. Four Master's students will work on this program. All graduate students will be in a thesis-based degree program.