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991.
Richard P. Nelson John C. B. Papaloizou 《Monthly notices of the Royal Astronomical Society》1999,309(4):929-940
We present the results of a study of propagating warp or bending waves in accretion discs. Three-dimensional hydrodynamic simulations were performed using smoothed particle hydrodynamics (SPH), and the results are compared with calculations based on the linear theory of warped discs.
We examine the response of a gaseous disc to an initially imposed warping disturbance under a variety of physical conditions. We consider primarily the physical regime in which the dimensionless viscosity parameter α < H r , where H r is the disc aspect ratio, so that bending waves are expected to propagate. We also performed calculations for disc models in which α > H r , where the warps are expected to evolve diffusively. Small-amplitude (linear) perturbations are studied in both Keplerian and slightly non-Keplerian discs, and we find that the results of the SPH calculations can be reasonably well fitted by those of the linear theory. The main results of these calculations are: (i) the warp in Keplerian discs when α < H r propagates with little dispersion, and damps at a rate expected from estimates of the code viscosity; (ii) warps evolve diffusively when α > H r ; (iii) the slightly non-Keplerian discs lead to a substantially more dispersive behaviour of the warps, which damp at a similar rate to the Keplerian case, when α < H r .
Initially imposed higher amplitude, non-linear warping disturbances were studied in Keplerian discs. The results indicate that non-linear warps can lead to the formation of shocks, and that the evolution of the warp becomes less wave-like and more diffusive in character.
This work is relevant to the study of the warped accretion discs that may occur around Kerr black holes or in misaligned binary systems, and is mainly concerned with discs in which α < H r . The results indicate that SPH can model the hydrodynamics of warped discs, even when using rather modest numbers of particles. 相似文献
We examine the response of a gaseous disc to an initially imposed warping disturbance under a variety of physical conditions. We consider primarily the physical regime in which the dimensionless viscosity parameter α < H r , where H r is the disc aspect ratio, so that bending waves are expected to propagate. We also performed calculations for disc models in which α > H r , where the warps are expected to evolve diffusively. Small-amplitude (linear) perturbations are studied in both Keplerian and slightly non-Keplerian discs, and we find that the results of the SPH calculations can be reasonably well fitted by those of the linear theory. The main results of these calculations are: (i) the warp in Keplerian discs when α < H r propagates with little dispersion, and damps at a rate expected from estimates of the code viscosity; (ii) warps evolve diffusively when α > H r ; (iii) the slightly non-Keplerian discs lead to a substantially more dispersive behaviour of the warps, which damp at a similar rate to the Keplerian case, when α < H r .
Initially imposed higher amplitude, non-linear warping disturbances were studied in Keplerian discs. The results indicate that non-linear warps can lead to the formation of shocks, and that the evolution of the warp becomes less wave-like and more diffusive in character.
This work is relevant to the study of the warped accretion discs that may occur around Kerr black holes or in misaligned binary systems, and is mainly concerned with discs in which α < H r . The results indicate that SPH can model the hydrodynamics of warped discs, even when using rather modest numbers of particles. 相似文献
992.
Daniel Proga † James M. Stone Janet E. Drew 《Monthly notices of the Royal Astronomical Society》1999,310(2):476-482
We describe an efficient method of calculating the radiation pressure resulting from spectral lines, including all the terms in the velocity gradient tensor. We apply this method to calculate the two-dimensional, time-dependent structure of winds from luminous discs. Qualitative features of our new models are very similar to those we calculated including only the dominant terms in the tensor. In particular, we find that models which displayed unsteady behaviour in our earlier paper are also unsteady with the new method, and gross properties of the winds, such as mass-loss rate and characteristic velocity, are not changed by the more accurate approach. The largest change caused by the new method is in the disc-wind opening angle: winds driven only by the disc radiation are more polar with the new method, whilst winds driven by the disc and central object radiation are typically more equatorial. In the closing discussion, we provide further insight into the way the geometry of the radiation field and consequent flow determine the time properties of the flow. 相似文献
993.
D. G. Korycansky 《Monthly notices of the Royal Astronomical Society》1999,310(1):110-116
A boundary integral formulation for the dynamics of incompressible, inviscid, self-gravitating bodies is described. The method is applied to several problems of astrophysical interest: spheroidal equilibria (Maclaurin and Jeans), oscillations, and a simple version of tidal encounter and breakup. 相似文献
994.
本文用日本山梨大学片谷教孝等人建立的3维欧拉型污染物远距离输送模式,分别输入1988年6月月平均和逐时气象资料(风场、气压场、密度场、降水等),对夏季东亚地区SOx的远距离输送进行了数值模拟。所有实验均积分1个月,对SO2、SO2-4的地面浓度及沉降量进行了分析,实验结果表明:如果仅仅考虑SO2的远距离输送模拟,可以月平均场气象资料代替模式中需要的逐时场气象资料;而将逐时场的风、降水资料和月平均场的气压、密度资料共同使用则与输入逐时场气象资料对SO2及SO2-4模拟结果完全相当。由于实验中只使用了1988年6月的资料,故下一步的研究应对不同年、季的气象资料及不同污染物的远距离输送模拟进行比较,从而考察月平均场气象资料在污染物远距离输送的模拟中能否完全或部分代替逐时场气象资料。 相似文献
995.
东亚夏季大气环流和气候对冬季海温异常的邻响应和遥响应 总被引:1,自引:1,他引:0
本文通过IAP-GCM的数值模拟,研究了全球大气环流对黑潮海域和赤道东太平洋冬季SST异常的响应,并着重比较东亚大气环流和气候对黑潮区SSTA的响应(邻响应)和对赤道东太平洋SSTA的响应(遥响应)。首先,无论是黑潮区SSTA引起的邻响应还是赤道东太平洋SSTA所引起的遥响应对东亚大气环流和气候变化的影响都是明显而重要的。由于在大气中低频振荡被激发出来,其响应将持续较长时间。进一步分析表明,东亚大气环流对黑潮区或赤道东太平洋冬季正SSTA的响应都将造成华北地区夏季的多雨,其数值模拟结果与观测相一致。另外,赤道西太平洋地区大气的异常(尤其是对流活动)对于东亚地区大气环流和气候变化有重要作用 相似文献
996.
本文回顾了80年代以来国际上关于岩浆结晶及成矿作用过程的计算机模拟这一领域的研究进展,主要包括镁铁质干岩浆体系、长英质湿岩浆体系的岩浆结晶作用模拟,以及有关的岩浆矿床成矿作用、岩浆热液成矿作用的模拟。基于对这一领域研究现状和发展趋势的分析,笔者首次提出了模拟岩石学的概念。预测在今后5~10年内,模拟岩石学将得到突飞猛进的发展,并将对现代岩石成因理论、实验岩石学与矿物学、实验地球化学、矿床成因理论和矿产预测及勘察理论产生重要影响。 相似文献
997.
针对用均匀高阻介质中的低阻体来模拟含水岩溶构造的缺陷,用积分方程法对两层介质中的岩溶构造进行了数值模拟,并分析了计算曲线的特征,以及表层、岩溶与围岩的电阻率差异对探测结果的影响。计算结果对野外施工和资料解释具有指导意义。 相似文献
998.
本文采用先进的LAGFD风、浪数值模式和POM(PrincetonOceanModel)三维海流模式对自1945~1995年间发生并影响南海东部海域的299个历史最强热带气旋过程进行数值后报,给出了南海东部部分海域(19°~23°N,113°~118°E)中1000m等深线内60个点的多年一遇风、浪、流和水位极值,并简要分析了南海东部(15°~27°N,108°~122°E)的气候特征,为该海域区域性海洋环境研究与工程开发提供了基础参考数据。 相似文献
999.
AnumericalpredictionmodelofstrongthermoclineintheBohaiandtheHuanghaiSeasWangZongshan,XuBochang,JinMeibing,ZouEmei,LiFanhua(Re... 相似文献
1000.
Numerical sea ice prediction in China 总被引:5,自引:2,他引:3
NumericalseaicepredictioninChinaWuHuiding,BaiShan,ZhangZhanhai1(ReceivedSeptember12,1996;acceptedJune5,1997)Abstract──Adynami... 相似文献