EAGER: Towards a Universal Roughness Model

在许多科学和工程学科中都会出现跨越粗糙边界的流动，包括城市和植被树冠、海洋生物污垢、流动通道的添加制造、管道运输等。这项研究探索了一种新的、准确的、通用的、包含物理的、计算效率高的建模框架，该框架基于空间/时间平均和伴随的Navier-Stokes控制方程建模。这项研究是通过对这些粗糙墙系统的大规模直接数值模拟实现的，该模拟提供了模型项的近准确的空间/时间分布，从而使模型精度的不确定性量化成为可能。这里提出的一个广泛适用的分布式元素粗糙度模型将对涉及广泛学科的流体动力学社区做出颠覆性的贡献，包括空气/流体动力学、大气科学、生物流体动力学和能源科学。此外，考虑到机器学习的进步对大数据集的重视程度越来越高，拟议的直接数值模拟数据库将为流体工程和科学界带来新的物理发现、新的湍流模型和重要的验证数据的显著增加。此外，拟议的研究活动将培养具有高性能计算、计算流体力学和湍流建模经验的新一代研究生。该项目的目标是探索双平均Navier-Stokes闭合作为通用粗糙度建模范例。现有的粗糙壁模型对表面几何/结构进行了参数化，并且这些参数与流体动力/气动特性之间是经验相关的。在那里，负责动量损失和传输的物理过程没有明确地建模，所以这些模型不能很好地推广到它们相关基础之外的粗糙几何图形。相比之下，水平和时间平均的控制方程包括表示存在于粗糙度占据层中的所有物理过程的项，并且这些项中的每一个都可以被显式建模。这种方法，即分布式单元粗糙度模型，是开发普遍适用的粗糙度模型的必要和充分的框架。在这种方法中，需要雷诺应力、色散应力和流体-材料界面上的力的模型。在拟议的研究中，PI将探索开发这样一个完整的粗糙度模式，基于对双平均Navier-Stokes方程中的这些闭合项进行建模。这项拟议研究的最终目标是一个通用的建模范例和一个通用的粗糙墙模型。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Flows over rough boundaries arise in many scientific and engineering disciplines including urban and vegetation canopies, maritime biofouling, additive manufacturing of flow passages, pipe transport and others. This research explores a new, accurate, general, physics-inclusive, and computationally efficient modeling framework for these flows, based on space/time averaging and attendant modeling of the Navier-Stokes governing equations. This research is enabled by proposed large scale Direct Numerical Simulations of these rough wall systems, which provide near-exact space/time distributions of model terms, thereby enabling uncertainty quantification of model accuracy. A broadly applicable Distributed Element Roughness Model, as proposed here, would be a disruptive contribution to fluid dynamics communities involved in a wide range of disciplines, including aero/hydrodynamics, atmospheric science, bio-fluid dynamics, and energy science. Also, considering that progress in machine learning has placed an ever-increasing premium on large data sets, the proposed database of Direct Numerical Simulations will enable new physics discoveries, new turbulence models, and, importantly, a significant increase in validation data, for the fluids engineering and science communities. Also, the proposed research activities will train a new generation of graduate students with experience in high performance computing, computational fluid dynamics, and turbulence modeling.The goal of the project to explore Double-Averaged Navier-Stokes closure as a universal roughness modeling paradigm. Existing rough-wall models parameterize surface geometry/structure and are empirical correlations between these parameters and hydrodynamic/aerodynamic properties. There, physical processes responsible for the momentum loss and transport are not explicitly modeled, so these models do not generalize well to roughness geometries outside of their correlation basis. By contrast, the horizontally and temporally averaged governing equations include terms representing all physical processes present in the roughness-occupied layer, and these can each be explicitly modeled. This approach, a Distributed Element Roughness Model, is a necessary and sufficient framework for the development of a universally applicable roughness model. In this approach, models are required for the Reynolds stress, the dispersive stress, and the forces at fluid-material interfaces. In the proposed research, the PIs will explore development of such a complete roughness model, based on modeling these closure terms in the Double-Averaged Navier-Stokes equations. The ultimate goal of the proposed research is a universal modeling paradigm, and a universal rough wall model.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.