Collaborative Research: Elements: Software: NSCI: Chrono-An open-source simulation platform for computational dynamics problems

该项目旨在增强Chrono所采用的建模和解决方法，Chrono是一个用于多体动力学（MBD）和流固耦合（FSI）问题的开源计算机仿真平台。Chrono将能够捕捉各种大小和时间尺度的动态，从毫秒（撞击现象）到几十年（天体物理学）。这些性能水平在几个领域开辟了新的研究方向。Chrono被其他用户广泛使用和进一步开发，目前拥有超过250名注册用户的活跃论坛。该项目将增强Chrono的建模功能的丰富性，健全的数值解决方案基础，并利用新兴的硬件架构，将这种模拟能力提升到即用型，开源，一流的计算动力学平台的地位。Chrono已被大学、国家实验室和工业界使用。在过去的两年中，各个小组已经将Chrono用于外星应用，机器人中的机器学习，图像处理，模式识别和计算机视觉，机械手表设计，建筑研究，自动驾驶汽车，流体-固体相互作用应用，风力涡轮机动力学，下一代太空服设计，石油开采和事故缓解，硬件在环仿真等。该项目将吸引来自代表性不足群体的高中生参加为期六天的住宿营活动（现在是第12版），并将通过一个新的住宿计划培训一批来自威斯康星大学麦迪逊分校的加州州立大学的本科生，该计划将向他们介绍在模拟中使用Chrono-该项目旨在增强Chrono所采用的建模和解决方法，Chrono是一个用于多体动力学（MBD）和流固耦合（FSI）问题的BSD 3开源仿真平台。该项目中的软件基础设施增强旨在维持MBD和FSI系统的万亿次浮点级仿真，具有超过一百亿个自由度;即，两到三个数量级，超出了今天的传统模拟。为了提高采用率和影响力，目标性能水平将在利用GPU计算的预算/负担得起的硬件上实现。Chrono将能够捕捉从毫秒（撞击现象）到几十年（天体物理学）的时间尺度上的微观、中观和宏观尺度动态。该项目的智力价值源于以下关键思想：（i）着眼于摩尔定律的日落，软件设计解决方案采用可扩展的多GPU硬件布局，以有效解决大型多物理问题;（ii）硬件感知软件设计范例，其积极地减少数据存储和移动，将允许有意识的硬件系统运行十亿自由度的模型，或者，对于类似大小的模型，当与现有技术相比时，实现两个数量级的加速; ㈢在一个软件平台中实现固体和流体动力学的统一拉格朗日公式，该平台可模拟复杂的多物理场（耦合）问题;和（四）Chrono提出了一种处理摩擦和接触的替代方法，这种方法围绕着微分变分不等式的概念，从而避免了小的积分时间步长和数值不稳定性问题，阻碍了大多数现有的多体动力学模拟器。关于其教育和推广活动，该项目：（a）将有助于设立一个新的威斯康星大学麦迪逊分校本科课程，向学生介绍计算机概念，随后在研究生高级计算机课程中加以完善;（B）将通过每年两次的暑期住宿计划，在高中和本科阶段促进计算科学和计算动力学学科的发展，（c）将扩大一个先进的计算论坛，促进技术转让给工业界，并促进Chrono的采用;（d）将加强目前在机器人技术、地质力学和软物质物理学方面严重依赖Chrono的合作。Chrono目前平均每天被克隆10次，已经有超过150个团体从其公共存储库中分叉，并拥有一个拥有250多个注册用户的活跃论坛。该项目将增强Chrono建模功能的丰富性，改善其数值解基础，并利用新兴的硬件架构将这种模拟能力提升到即用型、开源、一流的计算动力学平台的地位。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project seeks to augment modeling and solution methods employed by Chrono, an open-source computer simulation platform for multi-body dynamics (MBD) and fluid-solid interaction (FSI) problems. Chrono will be able to capture dynamics at various size and time scales spanning from millisecond (impact phenomena) to decades (geophysics). These performance levels open up new directions of research in several fields. Chrono is widely used and further developed by other users and has an active forum with more than 250 registered users currently. This project will enhance the richness of Chrono's modeling features, sound numerical solution foundation, and leverage of emerging hardware architectures to elevate this simulation capability to the status of ready-to-use, open-source, best-in-class computational dynamics platform. Chrono has been used by universities, national labs, and industry. Over the past two years, various groups have used Chrono in extraterrestrial applications, machine learning in robotics, image processing, pattern recognition and computer vision, mechanical watch design, architectural studies, autonomous vehicles, fluid-solid interaction applications, wind turbine dynamics, next generation space suit design, oil extraction and accident mitigation, hardware-in-the-loop simulation, etc. Finally, this project will engage high-school students from under-represented groups in a six-day residential camp run (now at its 12th edition) and will train a group of undergraduate students from California State University at University of Wisconsin-Madison through a new residential program that will introduce them to the use of Chrono in simulation-based robotics design.This project seeks to augment modeling and solution methods employed by Chrono, a BSD3 open-source simulation platform for multi-body dynamics (MBD) and fluid-solid interaction (FSI) problems. The software infrastructure enhancements in this project aim at sustaining teraflops-grade simulation of MBD and FSI systems with more than ten billion degrees of freedom; i.e., two to three orders of magnitude beyond conventional simulations today. In order to increase adoption and impact, the performance levels aimed at will be reached on budget/affordable hardware that leverages GPU computing. Chrono will be able to capture micro-, meso- and macro-scale dynamics on time scales spanning from millisecond (impact phenomena) to decades (geophysics). The intellectual merit of this project stems from the following key ideas: (i) with an eye towards the sunsetting of Moore's law, the software design solution embraces a scalable multi-GPU hardware layout poised to solve effectively large multi-physics problems; (ii) a hardware-aware software design paradigm, which aggressively reduces data storage and movement, will allow budget-conscious hardware systems to run billion-degree-of-freedom models, or, for models of similar size, accomplish a two orders of magnitude speedup when compared to the state of the art; (iii) a unified Lagrangian formulation for both solid and fluid dynamics is implemented in one software platform that can simulate complex multi-physics (coupled) problems; and (iv) Chrono promotes an alternative approach for handling friction and contact that revolves around the concept of differential variational inequality and thus avoids the small integration time step and numerical instability issues that hinder most of the existing many-body dynamics simulators. In relation to its educational and outreach initiatives, this project: (a) will be instrumental in establishing a new University of Wisconsin-Madison undergraduate course that introduces students to computing concepts subsequently refined in a graduate advanced computing class; (b) will promote the discipline of Computational Science and Computational Dynamics at high-school and undergraduate levels via two yearly residential summer programs for under-represented students; (c) will expand an advanced computing forum that facilitates technology transfer to industry and promotes Chrono adoption; and, (d) will strengthen ongoing collaborations that critically depend on Chrono in robotics, geomechanics, and soft-matter physics. Chrono is presently cloned on average 10 times every day, has been forked from its public repository by more than 150 parties, and has an active forum with more than 250 registered users. This project will enhance the richness of Chrono modeling features, improve its numerical solution foundation, and leverage emerging hardware architectures to elevate this simulation capability to the status of ready-to-use, open-source, best-in-class computational dynamics platform.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.