含裂隙煤体瓦斯渗流规律的LBM数值模拟

Numerical simulation of coalgas seepage in fractured coal by LBM

通过模拟外力驱动渗流以及部分填充多孔介质的剪切渗流,验证了广义LBM模型可以对含有裂隙的煤体内瓦斯渗流规律进行模拟研究;裂隙内的流速明显高于在煤基质内的流速,定量研究了渗流速度和流量随着裂隙宽度增加的变化规律;而在裂隙宽度相等的条件下,煤体渗透率越低则流速和流量的提高越显著;与顺流向的裂隙相比,垂直流向裂隙的存在对提高渗流速度及流量的影响相对较为有限。模拟结果表明:裂隙的存在,尤其是在渗透性较差的煤层中,对提高瓦斯抽放的效果更为明显;而对于不同方向的裂隙,则应该重点关注与瓦斯流动方向相同或大体相同的裂隙分布。

With the numerical tests of the modified Couette flow partly filled with porous medium, it shows that the generalized LBM model is suitable for simulating gas seepage in fractured coal. Compared to the seepage velocity in coal matrix, the velocity is much higher in coal fracture. The velocity, flow flux and their variation were also studied quantitatively with different fracture widths. In cases where the fracture widths are the same, the variation of velocity and flow flux becomes much more obvious with the lower permeability. Compared with cases where the fracture is along the flow direction, the improvements in velocity and flow flux are relatively limited in the case of the fracture and flow direction are vertical. The numerical results show that the influence of fracture is more obvious, especially in low permeable coalheds. For fractures with different directions, those along flow direction or close to it should be given more attention in simulations.