ABSTRACT

The Floating Drilling Production Storage and Offloading (FDPSO) Platform is functionally a non-propelled vessel and belongs to a subset of a wider group of vessels called Floating Production Systems (FPS). The FDPSO, besides its unique attribute of drilling capability, has all the functionalities of FPSOs. Given the remote offshore locations of oil fields, FDPSOs provide viable economic solution for drilling, production, storage and offloading to smaller vessels for transportation of oil. This paper addresses the designer’s concern in the critical role of positioning of the moonpool since it has a direct bearing on the dynamic effects experienced by the platform. The investigation provides valuable quantitative insights into the important effects on drag during towing, sloshing effect within the moonpool and motion dynamics due to the liquid oscillation. The results of this investigation using numerical and experimental tools, is expected to give key inputs for the designer towards the design of better performing FDPSO platform and benefit the industry. This paper investigates the vessel dynamics including the liquid oscillation behaviour inside the moonpool as a function of the moonpool location in the vessel. The results of the study are important inputs to a designer for consideration of new designs. The FDPSO is a dedicated design of a large capacity platform, different from the conventional FPSO which is usually a retrofitted ship for the purpose. The investigation is based on computational simulation using a commercial RANSE solver namely, STAR-CCM+. Comparison with results from towing tank tests serves to initially validate the numerical simulation-based results. The study performs hydrodynamic diffraction analysis using a potential flow-based solver, namely ANSYS – AQWA. A simplified hull form represents the FDPSO, considering that it is a platform predominantly stationary in operation. However, drag and interactive effects with the moonpool as well as a liquid oscillation in the moonpool are important dynamic conditions for investigation in stationary as well as transit conditions during the tow. The focus of the investigation is on moonpool dynamics in calm water and regular sea conditions and ship motion in waves. The moonpool is vertical circular cylindrical shaped and the investigation considers three moonpool locations namely, at the forward, the midship and the aft, respectively. The water column in the moonpool experiences large oscillatory motions in the piston mode or the sloshing mode. The analysis captures the flow physics, amplitude of oscillations, hydrodynamics resistance and the vessel motion response. The results obtained establish that the location of the moonpool contributes to the augmentation of the cavity drag in the FDPSO. For the selected parameters, the study indicates that the moonpool located in the forward region gives better performance as compared to responses in the other locations.

摘要

浮式钻井生产储存和卸载 (FDPSO) 平台在功能上是一种非推进船舶，属于更广泛的称为浮式生产系统 (FPS) 的船舶的一个子集。FDPSO除了具有钻井能力的独特属性外，还具有FPSO的所有功能。鉴于油田位于偏远的近海位置，FDPSO 为钻井、生产、储存和卸载到小型船舶以运输石油提供了可行的经济解决方案。本文解决了设计师对月池定位的关键作用的关注，因为它直接影响平台所经历的动态效应。该调查为拖曳过程中对阻力的重要影响提供了有价值的定量见解，月池内的晃动效应和液体振荡引起的运动动力学。这项使用数值和实验工具的调查结果预计将为设计人员提供关键输入，以设计性能更好的 FDPSO 平台并造福于行业。本文研究了船舶动力学，包括作为月池在船舶中位置的函数的月池内的液体振荡行为。研究结果是设计师考虑新设计的重要输入。FDPSO是大容量平台的专用设计，不同于传统的FPSO，后者通常是为此目的改装的船舶。该调查基于使用商业 RANSE 求解器即 STAR-CCM+ 的计算模拟。与拖曳水池试验结果的比较有助于初步验证基于数值模拟的结果。该研究使用基于潜在流的求解器（即 ANSYS – AQWA）进行流体动力学衍射分析。一个简化的船体形式代表了 FDPSO，考虑到它是一个在操作中主要是静止的平台。然而，拖曳和与月池的相互作用以及月池中的液体振荡是研究静止和拖曳过程中过境条件的重要动态条件。调查的重点是平静水域和常规海况下的月池动力学以及波浪中的船舶运动。月池为垂直圆柱形，研究考虑了三个月池位置，分别位于船首、船中和船尾。月池中的水柱在活塞模式或晃动模式下经历大的振荡运动。分析捕获流动物理、振荡幅度、流体动力学阻力和容器运动响应。获得的结果表明，月池的位置有助于增加 FDPSO 中的空腔阻力。对于选定的参数，研究表明，与其他位置的响应相比，位于前向区域的月池具有更好的性能。获得的结果表明，月池的位置有助于增加 FDPSO 中的空腔阻力。对于选定的参数，研究表明，与其他位置的响应相比，位于前向区域的月池具有更好的性能。获得的结果表明，月池的位置有助于增加 FDPSO 中的空腔阻力。对于选定的参数，研究表明，与其他位置的响应相比，位于前向区域的月池具有更好的性能。