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arXiv 0809.4637astro-ph
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光滑粒子流体动力学中辐射转移的一种混合方法

Introducing a Hybrid Method of Radiative Transfer in Smoothed Particle Hydrodynamics

Duncan Forgan, Ken Rice, Dimitris Stamatellos, Anthony Whitworth

摘要:

提出了一种将辐射转移引入光滑粒子流体动力学(SPH)的新方法。近来,人们对SPH中的辐射转移进行了许多尝试(Stamatellos等人2005年,2005年,Mayer等人2007年,Whitehouse和Bate 2006年),但是这些方法变得越来越复杂,有些方法需要绘制光球(通常是非平凡的几何形状),以及在那里应用的额外条件(如Cai等人(2008)中的匹配大气,或如Mayer等人(2007)中的指定光球冷却)。光球的识别方法通常是对整个模拟运行时间的一个重要补充,并且通常需要额外的自由参数,这些参数的变化将影响最终结果。我们的方法不受这些问题的影响,因为光球是由算法隐式构造的,而不需要额外的自由参数。所使用的算法是目前两种辐射效应形式的协同作用:a)Stamatellos等人(2007年)提出的多方冷却形式,以及b)通量限制扩散,许多作者用于模拟光学厚区域中的辐射传输(例如Mayer等人2007年)。我们对这种方法进行了几个检验:(1)0.07太阳质量的原行星盘围绕0.5太阳质量恒星的演化(Pickett et al 2003,Mejia et al 2005,Boley et al 2006,Cai et al 2008);(2)非旋转1太阳质量分子云的坍缩(Masunaga & Inutsuka 2000,Stamatellos等2007);(3)静态均匀球体中温度波动的热弛豫(Masunaga等1998,Spiegel 1957,Stamatellos等2007)

英文摘要:

We present a new method of incorporating radiative transfer into Smoothed Particle Hydrodynamics (SPH). There have been many recent attempts at radiative transfer in SPH (Stamatellos et al 2005, 2005, Mayer et al 2007, Whitehouse and Bate 2006), however these are becoming increasingly complex, with some methods requiring the photosphere to be mapped (which is often of non-trivial geometric shape), and extra conditions to be applied there (matching atmospheres as in Cai et al (2008), or specifying cooling at the photosphere as in Mayer et al (2007)). The method of identifying the photosphere is usually a significant addition to the total simulation runtime, and often requires extra free parameters, the changing of which will affect the final results. Our method is not affected by such concerns, as the photosphere is constructed implicitly by the algorithm without the need for extra free parameters. The algorithm used is a synergy of two current formalisms for radiative effects: a) the polytropic cooling formalism proposed by Stamatellos et al (2007), and b) flux-limited diffusion, used by many authors to simulate radiation transport in the optically thick regime (e.g. Mayer et al 2007). We present several tests of this method: (1) The evolution of a 0.07 solar mass protoplanetary disc around a 0.5 solarmass star (Pickett et al 2003, Mejia et al 2005, Boley et al 2006, Cai et al 2008); (2) The collapse of a non-rotating 1 solar mass molecular cloud (Masunaga & Inutsuka 2000, Stamatellos et al 2007); (3) The thermal relaxation of temperature fluctuations in an static homogeneous sphere (Masunaga et al 1998, Spiegel 1957, Stamatellos et al 2007)

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