Collaborative Research: CSEDI--Integrating Numerical and Experimental Geodynamo Models

数值和实验的地球发电机模型提供了互补的见解地球的液态铁核的动力学。该研究项目的目标是利用这两种方法的优势，以获得对地球磁场起源和演变的重要见解。该实验产生了在液态金属流中的物理上真实的湍流，远远超出了直接数值模拟的空间分辨率。实验观测到的流体和磁场之间的高度非线性相互作用提供了关于核心重要过程复杂性的独特信息。计算的平行进步产生了越来越复杂的模型，无法解决（亚网格尺度）湍流。这些模型已在数值地球发电机计算中得到实施和测试，取得了显着的成功。然而，努力推动这些模型的地球一样的条件是目前阻碍了缺乏“已知”的解决方案来测试预测的亚网格规模的模型。使用精心选择的诊断实验，使更现实的测试的数值模型。反过来，模型，帮助解释的实验，这建立了一个基础，用于完善的假设，在建设的亚网格规模的模型。计算和实验之间的协同作用是最有效地实现通过一个合作的研究计划。在这项研究中使用的实验包括球形库埃特流和旋转热对流。在任一情况下，外部施加的磁场与液态金属流相互作用。实验装置是基于先前的经验，其明确的目标是产生对湍流存在敏感的独特的大规模流动。这些大规模的功能的实验观测被用来测试的数值模型的预测。球形库埃特流允许流和磁场之间的强（和现实的）相互作用。地球发电机问题中四个关键的亚网格尺度模型中的三个正在通过测量液态金属外部的感应磁场模式在快速旋转和强磁场的条件下进行测试。旋转对流实验，有和没有施加磁场，被用来测试第四次亚网格尺度模型。对流实验的主要观测结果包括总热流、大尺度速度和温度涨落的功率谱。该研究项目的预期成果是一个更现实的地球发电机模型，该模型结合了湍流的复杂参数化和实验结果数据库，以刺激其他研究小组使用不同的建模策略进行类似的比较。

Numerical and experimental geodynamo models offer complementary insights into the dynamics of the Earth's liquid iron core. The goal of this research project is to leverage the strengths of both approaches to gain significant insights into the origin and evolution of the Earth's magnetic field. The experiments produce geophysically realistic turbulence in liquid metal flows that are well beyond the spatial resolution of direct numerical simulations. Experimental observations of highly nonlinear interactions between the flow and the magnetic field provide unique information about the complexity of important processes in the core. Parallel advances in computation have produced increasingly sophisticated models for unresolved (subgrid-scale) turbulence. These models have been implemented and tested in numerical geodynamo calculations with remarkable success. However, the effort to push these models to Earth-like conditions is presently hampered by the lack of "known" solutions to test the predictions of the subgrid-scale models. Use of carefully chosen diagnostics from the experiments enables more realistic tests of the numerical models. The models, in turn, aid the interpretation of the experiments, which establishes a foundation for refining the assumptions used in the construction of the subgrid-scale models. This synergy between computations and experiments is most effectively realized through a collaborative research program.The experiments used in this study include spherical Couette flow and rotating thermal convection. In either case, an externally imposed magnetic field interacts with the liquid metal flow. The experimental setups are based on prior experience with the explicit goal of producing distinctive large-scale flows that are sensitive to the presence of turbulence. Experimental observations of these large-scale features are used to test the predictions of the numerical models. Spherical Couette flow permits strong (and realistic) interactions between the flow and the magnetic field. Three of the four key subgrid-scale models in the geodynamo problem are being tested under the conditions of rapid rotation and strong magnetic fields by measuring the pattern of induced magnetic field outside the liquid metal. Rotating convection experiments, with and without an imposed magnetic field, are being used to test the fourth subgrid-scale model. The primary observations in the convection experiments include the total heat flow, the large-scale velocity and the power spectra of temperature fluctuations. The expected outcome of this research project is a more realistic geodynamo model that incorporates sophisticated parameterizations for turbulence and a database of experimental results to stimulate other research groups to engage in similar comparisons using different modeling strategies.