Collaborative Research: CDS&E: 3-D Stellar Hydrodynamics of Convective Penetration and Convective Boundary Mixing in Massive Stars

合作研究：CDS

• 批准号: 2309101
• 负责人: Paul Woodward
• 金额: $ 31.12万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-12-01 至 2026-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309101&HistoricalAwards=false
• 关键词: Collaborative; Research; CDS& Stellar; Hydrodynamics

Convection is a ubiquitous feature in Nature and occurs whenever energy transport by radiation and conduction is insufficient. It can be found in the Earth's atmosphere (e.g., cumulus clouds) and mantle (continental drift), and inside stars, where it can impact the chemical enrichment of their outer envelopes as well their Main Sequence lifetime. Despite tremendous progress, convection within stars is still poorly understood in some important respects, and our current best physical theory (mixing length theory; MLT), is inadequate in many situations. The team of researchers will apply a new 1-D convection model to improve the treatment of convection, particularly convective penetration or overshooting due to convective boundary mixing (CBM). This approach promises improved estimates of Main Sequence lifetimes as well as a more correct understanding of how adjacent "burning" shells within the cores of massive stars exchange matter and energy through convection. The award will also support the development of instructional software and modules suitable for undergraduates and college-bound high school students as well as summer research by undergraduate students attending the participating institutions. Simulation data will also be made available to other researchers.The team will work to improve the understanding of stellar evolution by removing key uncertainties that arise in standard MLT. This will be done by applying a new 1-D model of convection developed in their previous award. This model employs a new constraint equation which enables an improved estimate of the extent of convective penetration for a given the kinetic energy of convective motions at the Schwarzschild boundary. This kinetic energy cannot be known from a 1-D stellar evolution computation but can be determined accurately and inexpensively through a short 3-D simulation. The team will advance 1-D stellar evolution simulations using this more accurate representation of convective overshooting, and hence of CBM, by using the kinetic energy estimates together with the new constraint equation implemented in 1-D MESA code, while occasionally recalibrating the kinetic energy estimates with short yet inexpensive 3-D simulations. Using these periodic recalibrations, this procedure eliminates ad hoc free parameters, including the mixing length, from the 1-D model of convection and CBM.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.

对流是自然界中无处不在的特征，每当辐射和传导不足时，就会发生。它可以在地球的大气中（例如积云云）和地幔（大陆漂移）以及内部恒星中找到，在那里它可以影响其外部信封的化学富集以及其主序列寿命。尽管取得了巨大进展，但在某些重要方面，恒星内的对流仍然很鲜为人知，在许多情况下，我们当前的最佳物理理论（混合长度理论； MLT）是不够的。研究人员团队将采用新的1D对流模型来改善对流的处理，尤其是由于对流边界混合（CBM）而引起的对流穿透或过冲。这种方法有望改善对主要序列寿命的估计，以及对大型恒星核心内“燃烧”贝壳如何通过对流如何交换物质和能量的“燃烧”壳的理解。该奖项还将支持适用于本科生和大学高中生的教学软件和模块的开发，以及参加参与机构的本科生的夏季研究。模拟数据还将提供给其他研究人员。该团队将通过消除标准MLT中出现的关键不确定性来提高对恒星进化的理解。这将通过应用以前的奖励中开发的新的1D对流模型来完成。该模型采用了一个新的约束方程，该方程式可以改善对施瓦茨柴尔德边界对流运动动力的对流渗透程度的估计。从1-D恒星演化计算中无法知道这种动能，但可以通过短的3D模拟准确，廉价地确定。该团队将使用这种更准确的对流过度旋转和CBM的更准确表示，通过使用动能估算以及1-D MESA代码中实现的新约束方程，同时偶尔重新校准了动能能量，将推进1D恒星进化模拟。估计值短但廉价的3-D模拟。使用这些定期重新校准，该程序从对流的1-D模型和CBM中消除了包括混合长度在内的临时参数，该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和智力优点来评估的。更广泛的影响审查标准。