Pyroclastic density currents (PDCs) present significant hazards due to their high temperatures and dynamic pressures. Accurate estimation of dynamic pressure, vital for assessing potential damage, requires knowledge of the vertical variations of velocity and particle concentration within the PDC, particularly in the first few meters of the flow above the ground. Existing approaches to dynamic pressure calculations used in hazard assessment are often based on average values for velocity and particle volume fraction. These average values may misrepresent the flow dynamics, especially near the base of the flow where the gradients of flow variables are larger. Here, we present a new, physically based approach that allows for the calculation of the vertical profiles of velocity and concentration from a combination of depth-averaged values for these properties and non-dimensional flow parameters. Finally, we demonstrate the use of these profiles within an existing shallow-water model and show its potential applications toward probabilistic hazard assessment.

中文翻译：

---

超越平均值：稀火山碎屑密度流中垂直剖面的计算及其在浅水模型中的使用


火山碎屑密度流 （PDC） 由于其高温和动态压力而存在重大危险。准确估计动态压力对于评估潜在损害至关重要，需要了解 PDC 内速度和颗粒浓度的垂直变化，尤其是在离地面流的前几米。危害评估中使用的现有动态压力计算方法通常基于速度和颗粒体积分数的平均值。这些平均值可能会歪曲流动动力学，尤其是在流动底部附近，流动变量的梯度较大。在这里，我们提出了一种新的、基于物理的方法，该方法允许根据这些属性的深度平均值和非量纲流动参数的组合来计算速度和浓度的垂直剖面。最后，我们演示了在现有浅水模型中使用这些剖面，并展示了其在概率灾害评估中的潜在应用。