FROTH: Fundamentals and Reliability of Offshore Structure Hydrodynamics

FROTH项目是五所大学之间的密切合作，这些大学在波浪与固定和浮动结构的相互作用研究方面有着丰富的经验，他们共同努力，将他们的专业知识结合起来，应用于问题的不同方面。目的是通过一个精心整合的数值模拟和大规模物理实验方案，研究刚性和弹性结构上剧烈流体动力冲击载荷的详细物理学。将开发开放源代码的数值代码，以模拟将在新的国家波浪和UoP现有设施中进行的实验室实验[http://www.plymouth.ac.uk/pages/view.asp?page=34369]]。众所周知，气候变化将导致海平面上升和风暴活动增加（要么是更严重的个别风暴，要么是更多的整体风暴，或者两者兼而有之），在英国和西北欧的近海海洋环境中。这对现有海上结构上人员的安全以及现有和新型LNG运输船的安全运行具有重要意义，这些运输船的结构由于在恶劣的海洋中运输的液体的剧烈晃动而受到巨大的瞬时载荷。英国海域现有的一些油气结构已经使用了40年，这些老化的结构需要重新评估，以确保它们能够承受由于气候变化而增加的负荷，并确认它们的寿命可以延长到未来25年。升级这些现有结构的成本，以及确保新结构和船舶的生存能力和安全运行的成本，将在很大程度上取决于水动力冲击载荷预测的可靠性。这些负荷会对海堤、储罐（如液化天然气运输船）造成严重破坏，并对fpso和其他海上浮动结构（如波浪能转换器）造成破坏。虽然我们对流体的流体力学已经有了较好的了解，但在工程设计中，如何以足够的精度模拟水面的剧烈运动和破裂仍然是一个主要的挑战。虽然自由地表高度和平均负荷通常通过分析技术预测得相对较好，但在这种极端条件下，观察到的瞬时峰值压力不能可靠地预测，即使在仔细控制的实验室实验中也常常不能重复。对于流体动力冲击载荷的详细物理，甚至对于固定结构和可能发生的极高压冲击，仍有许多深刻的基本问题有待解决。特别是，不确定性存在于对下列因素的影响的理解：水中空气的存在（包括被困的小袋和被困的气泡），因为水的声学特性发生变化，导致实验中测量到的波浪冲击压力的变异性；导致水弹性响应的结构柔韧性；入射波的陡度和三维度。本提案旨在通过一套紧密结合的实验室实验和最先进的数值模拟，直接解决这一根本困难和安全关键问题，最终目的是为近海、海洋和沿海固定和浮动结构的设计者提供改进的指导。

The FROTH project is a close collaboration between five universities with significant experience in research into wave interactions with fixed and floating structures working together to combine and apply their expertise to different aspects of the problem. The aim is to investigate the detailed physics of violent hydrodynamic impact loading on rigid and elastic structures through a carefully integrated programme of numerical modelling and physical experiments at large scale. Open source numerical code will be developed to simulate laboratory experiments to be carried out in the new national wave and current facility at the UoP [http://www.plymouth.ac.uk/pages/view.asp?page=34369]. It is well known that climate change will lead to sea level rise and increased storm activity (either more severe individual storms or more storms overall, or both) in the offshore marine environment around the UK and north-western Europe. This has critical implications for the safety of personnel on existing offshore structures and for the safe operation of existing and new classes of LNG carrier vessels whose structures are subject to large instantaneous loadings due to violent sloshing of transported liquids in severe seas. Some existing oil and gas offshore structures in UK waters are already up to 40 years old and these aging structures need to be re-assessed to ensure that they can withstand increased loading due to climate change, and to confirm that their life can be extended into the next 25 years. The cost of upgrading these existing structures and of ensuring the survivability and safe operation of new structures and vessels will depend critically on the reliability of hydrodynamic impact load predictions. These loadings cause severe damage to sea walls, tanks providing containment to sloshing liquids (such as in LNG carriers) and damage to FPSOs and other offshore marine floating structures such as wave energy converters.Whilst the hydrodynamics in the bulk of a fluid is relatively well understood, the violent motion and break-up of the water surface remains a major challenge to simulate with sufficient accuracy for engineering design. Although free surface elevations and average loadings are often predicted relatively well by analysis techniques, observed instantaneous peak pressures are not reliably predicted in such extreme conditions and are often not repeatable even in carefully controlled laboratory experiments. There remain a number of deeply fundamental open questions as to the detailed physics of hydrodynamic impact loading, even for fixed structures and the extremely high-pressure impulse that may occur. In particular, uncertainty exists in the understanding of the influence of: the presence of air in the water (both entrapped pockets and entrained bubbles) as the acoustic properties of the water change leading to variability of wave impact pressures measured in experiments; flexibility of the structure leading to hydroelastic response; steepness and three dimensionality of the incident wave.This proposal seeks to directly attack this fundamentally difficult and safety-critical problem with a tightly integrated set of laboratory experiments and state of the art numerical simulations with the ultimate aim of providing improved guidance to the designers of offshore, marine and coastal structures, both fixed and floating.