Pulsation evolution and hydrodynamics of rapidly rotating stars

随着高性能数字计算机的出现，我们对恒星结构和演化的了解大大增加了。到目前为止，我们已经了解恒星的基本生命周期大约40年了，但我们未能与日益精细的观测相匹配，这表明我们并不是什么都懂。例如，传统模型既没有预测必须在恒星内部深处产生并输送到表面的某些元素的表面丰度的增强，也没有预测比太阳质量略大的所有观测到的恒星振荡周期的正确值。传统模型中没有包括的自转被认为是造成这些差异的可能原因。这不仅可以通过自转力产生的恒星结构的改变来实现，也可以通过由自转引起的不稳定性产生的短时间和中等时间尺度的运动来实现。这些不稳定性产生的运动将物质和角动量输送到整个恒星。因此，本研究中提出的多维计算有望在给定的角动量分布下充分再现恒星结构。随着进一步的发展，由这些旋转不稳定性产生的成分和角动量分布的演化也有望被跟踪。这应该允许我们缩小恒星可能存在的角动量分布可能性。这种物质和角动量的重新分配在恒星生命早期就开始了。恒星演化的后期将受到影响，这可能也是了解后期观测和模型之间某些差异的关键。所用的计算方法在许多其他研究领域都有应用：气候研究、湍流研究和国防相关工作。

Our knowledge of the structure and evolution of stars has increased greatly with the advent of high powered digital computers. We have understood the basic life cycle for stars for about four decades now, but our failure to match increasingly refined observations demonstrates that we do not understand everything. For example, the traditional models predict neither the enhancement of the surface abundances of some elements which must be created deep inside the star and transported to the surface nor the correct values for all the observed oscillation periods of stars appreciably more massive than the sun.Rotation, not included in the traditional models,  has been identified as the possible reason for these discrepancies. This may come not only through the alteration of the stellar structure produced by the rotational force, but also through short and intermediate time scale motion produced by instabilities that rotation can cause. The motion produced by these instabilities transports material and angular momentum throughout the star.  The multi-dimensional calculations proposed in this research can be expected to reproduce the stellar structure adequately for a given angular momentum distribution. With some further development, it is expected that the evolution of the composition and angular momentum distributions produced through these rotational instabilities can be followed as well. This should allow us to narrow the possible angular momentum distribution possibilities that stars have. This redistribution of material and angular momentum begins early in the star's life. Later stages of stellar evolution will be affected by this and this may be the key to understanding some discrepancies between observation and models in these later phases as well.The computational methods utilized have application in many other areas of research: climate studies, turbulence research, and defense related work.