Development of a Computing Code Accurate Prediction of Output and Life of Hot Dry Rock Power Generation

研究人员基本完成了对干热岩发电出力和寿命进行准确预测的计算系统的主体框架。计算系统结合子系统进行分析：(1)热边界条件下无限大介质中的非稳态热传导和温度梯度引起的热弹性；(2)力学边界条件下水力压裂形成的裂缝孔径分布和裂缝周围岩石的变形；(3)岩石应力、裂缝内流体压力和热弹性共同作用引起的裂缝孔径扩张导致的裂缝尖端应力强度因子和裂缝延伸；(4)裂隙内非定常流体流动速度分布及岩石向流体的传热。他们已经完成了(1)~(3)子系统，(1)和(2)的成果已经在期刊上发表。(3)的结果将在2000年举行的两次国际会议上报告。(4)的一部分，即传热计算子系统的开发尚未完成，但其基础将很快完成。1999财年的研究结果如下：1)过去不允许将边界划分为单元，使某个单元的重心位于其他三角形单元的三边延伸上。在本研究中开发的程序中，可以对这种情况进行严格的分析积分。此外，解析积分的表达式变得简单，计算速度快，精度高。2)对位移不连续分布为平方根形的裂纹尖端单元进行了严格的解析积分，从而可以精确地计算裂纹尖端的应力强度因子。

The investigators almost have completed main frame of the computing system for accurate prediction of output and life of Hot Dry Rock power generation. The computing system combine the sub-systems which are to analyze : (1) non-steady heat conduction in the infinite medium under thermal boundary condition and thermal elasticity induced by temperature gradient, (2) aperture distribution of the fracture created by hydrofracturing and deformation of rock around the fracture under mechanical boundary condition, (3) stress intensity factor at fracture tip and fracture extension due to aperture expansion induced by interaction of rock stress, fluid pressure in the fracture and thermal elasticity, and (4) velocity distribution of non-steady fluid flow in the fracture and heat transfer from rock to fluid flow.They already completed the sub-systems, (1)〜(3) and the fruits with respect to (1) and (2) were already reported in the journals. The results of (3) will be reported at two international congress held in 2000. A part of (4), that is, development of the sub-system to calculate heat transfer is not completed but the basis of it will soon be completed.The research results obtained in FY 1999 are as follows :1) In the past, division of the boundary into elements such that the center of gravity of some element lay on the prolongations of three sides of any other triangular element, was not permitted. In the procedure developed in this study, strict analytical integration for such case can be done. Furthermore, the expressions of analytical integrals become simple and so, computation can be fast and accurate.2) Strict analytical integration for crack-tip element whose displacement discontinuity distribution is square root shape, was put into operation and so, precise calculation of stress intensity factor at fracture tip can be done.