Geophysical flow dynamics using pulsed Doppler radar

大规模流动在世界各地是一种重大的自然灾害，但我们预测其行为和计划其影响的能力受到限制，部分原因是我们缺乏对其流动动力学的了解。这项研究将通过在雪崩和火山试验场进行仔细控制的试验，调查地球物理物质运动流动过程(特别是雪崩和火山碎屑流)的动力学。这项研究将利用一种先进的新型多普勒雷达成像仪，能够形成各种地球物理事件的二维动画图像。在皇家学会的支持下，伦敦大学学院一直在开发这种雷达，通过穿透雪崩和火山碎屑流周围的悬浮物，可以对流动的密集部分(通常是风险分析的最重要组件)进行成像。先进的信号处理算法将被用来生成流动的结构和动力学的详细模型。目前，光电仪器可以在一个点上提供这种信息，现有的多普勒雷达可以提供流速的粗略图像，但平均速度超过50米，只能给出速度大小的总体测量(没有关于方向的信息)。我们的仪器将把平均距离减少到只有1米，这样就可以第一次获得关于流动中个别区块的信息，并根据它们对整体流动动力学的重要性进行评估。因此，我们可以评估为描述这种过程而提出的各种流动定律的有效性。这将改进这些流动过程的模型，将模型中的系数值限制在合理的值，并彻底拒绝一些提出的流动定律。这将导致对这些过程进行更准确的建模，进而改进风险分析和防御结构的设计。因此，这项研究将大大增加我们对水流运动的了解，并将英国在这一领域的研究地位提高到国际领先水平。

Mass movement flows are a significant natural hazard throughout the world and yet our ability to predict their behaviour and plan for their effects is limited, in part, by our lack of understanding of their flow dynamics. This research will investigate the dynamics of geophysical mass movement flow processes (specifically snow avalanches and pyroclastic flows) by means of carefully-controlled trials at avalanche and volcano test sites. This research will utilise a sophisticated and new Doppler radar imaging instrument, able to form two-dimensional animated images of a variety of geophysical events. This radar has been under development at University College London, supported by the Royal Society, and permits imaging of the dense parts of the flow (often the most important component for risk analyses) by penetrating the suspended matter surrounding snow avalanches and pyroclastic flows. Advanced signal processing algorithms will be used to generate detailed models of the structure and dynamics of the flow. At present, opto-electronic instruments can provide such information at a single point and existing Doppler radar can provide crude images of the flow speed, but averaged over 50 m and only giving an overall measure of the velocity magnitude (with no information on direction). Our instrument will reduce the averaging distance to just 1 m so that, for the first time, information on individual blocks in the flow can be obtained and assessed in relation to their significance for the overall flow dynamics. Thus, we can assess the validity of a variety of flow laws that have been proposed for describing such processes. This will lead to improved models for these flow processes by limiting the values of coefficient in the models to reasonable values and rejecting some proposed flow laws outright. This will lead to more accurate modelling of these processes, which in turn will improve risk analyses and the design of defensive structures. This study will therefore considerably increase our understanding of flow movement and raise the status of UK research in this area to internationally-leading standards.