本文關(guān)鍵詞：大質(zhì)量恒星中的對流及其對恒星結(jié)構(gòu)演化的影響　出處：《中國科學(xué)院研究生院（云南天文臺）》2014年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 大質(zhì)量恒星 對流 擴(kuò)散 中心對流超射 半對流

【摘要】：大質(zhì)量恒星內(nèi)部對流特征與中小質(zhì)量恒星有很大不同。在中小質(zhì)量星的主序階段，恒星是由對流核、輻射平衡殼層以及處于它們中間的輻射平衡中間層組成，這個(gè)中間層的化學(xué)元素分布不均勻。然而在大質(zhì)量恒星主序階段，這個(gè)化學(xué)元素分布不均勻區(qū)域會出現(xiàn)“半對流”現(xiàn)象。在本文中，我們采用史瓦西（Schwarzchild）方法和勒都（Ledoux）方法這兩種不同的方法來分別處理15M⊙和30M⊙恒星的“半對流”和對流超射。這兩種方法的不同之處在于對流邊界以及熵梯度所采用的公式不同：當(dāng)采用史瓦西方法時(shí)，熵梯度sc r=pHp(ad)；當(dāng)采用勒都方法時(shí)，熵梯度s r=cpHp(adμ)。中心核對流超射與中間區(qū)域中的“半對流”被當(dāng)成一個(gè)整體進(jìn)行處理。通過計(jì)算，我們發(fā)現(xiàn)，中心核對流超射與“半對流”所呈現(xiàn)的發(fā)展趨勢幾乎相反，，當(dāng)中心核對流超射增強(qiáng)的時(shí)候，“半對流”將減弱，反之亦然。本文通過模型計(jì)算，分析了不同參數(shù)以及不同對流處理方法對中心核超射區(qū)以及“半對流”區(qū)的湍流特征的影響。增大湍流模型中混合長參數(shù)α導(dǎo)致中心對流核的湍動能增加，并且使中心對流超射距離增加，但是會抑制“半對流”的發(fā)展。采用勒都方法來處理湍對流將使超射距離增加并抑制“半對流”的出現(xiàn)和發(fā)展。同時(shí)，本文用擴(kuò)散過程模擬近似對流超射及“半對流”對元素分布的影響。本文引用一個(gè)擴(kuò)散參數(shù)D來控制對流超射以及“半對流”對元素分布的影響程度。這不同于別的研究者們采用不同參數(shù)來分別處理對流超射以及“半對流”區(qū)的元素?cái)U(kuò)散過程。湍流元素?cái)U(kuò)散混合對化學(xué)元素分布演化以及H-R圖的影響在本文中也得以體現(xiàn)。
[Abstract]:The convection characteristics of large mass stars are very different from those of medium and small mass stars. In the main sequence stage of medium and small mass stars, the stars are composed of convective nuclei, radiation equilibrium shells and radiation equilibrium intermediate layers in the middle of them. The distribution of chemical elements in this interlayer is not uniform. However, in the main sequence of massive stars, "semi-convection" occurs in this region. We use the Schwarzchilds method and Ledoux). Methods these two different methods are used to deal with the "semi-convection" and convection overshoot of 15m-and 30m-298 stars, respectively. The difference between these two methods is that the convection boundary and the entropy gradient are different. When using the Schwartz method. Entropy gradient sc rn. When the Ledu method is used, the entropy gradient s r n c pH p + + 渭 n. The central nucleus flow overshoot and the "semi-convection" in the middle region are treated as a whole. By calculation, we find that the central nucleus flow overshoot and the "semi-convection" in the middle region are treated as a whole. The development trend of the central nucleus stream overshoot and "semi-convection" is almost opposite. When the central nucleus stream overshoot increases, the "semi-convection" will weaken, and vice versa. The model calculation is carried out in this paper. The effects of different parameters and different convection processing methods on the turbulent characteristics of the central nucleus overshoot region and the "semi-convection" region are analyzed. Increasing the mixing long parameter 偽 in the turbulence model results in the increase of the turbulent kinetic energy of the central convection nucleus. Moreover, the overshoot distance of central convection is increased, but the development of "semi-convection" is restrained. Using the Ledu method to deal with the turbulent convection will increase the overshoot distance and restrain the appearance and development of "semi-convection". In this paper, the effect of approximate convection overshoot and "semi-convection" on element distribution is simulated by diffusion process. A diffusion parameter D is used to control convection overshoot and "semi-convection". The degree of influence on the distribution of elements. This is different from other researchers using different parameters to deal with convective overshoot and "semi-convection", respectively. The effects of turbulent element diffusion and mixing on the chemical element distribution evolution and H-R diagram are also reflected in this paper.
【學(xué)位授予單位】：中國科學(xué)院研究生院（云南天文臺）
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：P152

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 ;Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars[J];Research in Astronomy and Astrophysics;2011年11期

本文編號：1379539