中文摘要：

基于流体力学理论对黑洞吸积构建了一个线性扩散模型,为了简化模型,假设粘滞系数ν与面密度Σ是独立的。对吸积黑洞光变建立了一个随机模型（OU过程）,并证明得到这个多维OU过程是存在扰动场的扩散模型的解。将OU过程应用于光变曲线拟合,结果表明：OU过程能很好地拟合光变曲线,有助于进一步了解吸积系统中心结构以及研究光变特性。

英文摘要：

In this work we present a linear diffusion model for accreting black holes based on fluid mechanics theory. We demonstrate the detailed mathematical analysis of the model,moreover, the boundary conditions of the model are described according to the accretion disk. For simplicity, the viscosity ν is assumed to be independent of surface density Σ.We have developed a Ornstein Uhlenbeck（OU） process for the fluctuations in light curves of accreting black holes and demonstrated that it is a general consequence of the diffusion processes perturbed by a spatially correlated noise field. In addition, in order to verify the simulated performance of the OU process, we apply our method to fitting optical light curves which are derived from AGN Watch Website. The results confirm that： the OU process takes a good approximation to light curves, which contribute to increasing our understanding of the structure of quasar accretion system and study the light curves features.