标题: | 双区受压含水层污染传输之半解析解与近似解 Semi-Analytical and Approximate Solutions for Contaminant Transport from an Injection Well in a Two-Zone Confined Aquifer System |
作者: | 谢秉峰 Hsieh, Ping-Feng 叶弘德 Yeh, Hund-Der 环境工程系所 |
关键字: | 径向传输;第三类 (Robin) 边界条件;肤层;拉普拉斯转换;地下水污染;radial transport;Robin boundary condition;skin zone;Laplace transform;roundwater pollution |
公开日期: | 2014 |
摘要: | 本研究发展一个数学模式用来描述径向双区受压含水层系统中污染物的浓度分布,含水层系统由肤层及主要含水层两区域所构成。此模式包含两个描述污染物浓度分布之暂态控制方程式,一个用来描述肤层而另一个用来描述主要含水层。当污染物被连续定量的注入井中时,由于延散及流传通量而在井壁处考虑为第三类 (Robin) 边界条件。应用拉普拉斯转换求得此模型的半解析解,并且当忽略肤层部分时可成功转回单区的半解析解。此外,我们也根据相同的模型考虑污染物在离井一段距离后因为延散机制的影响变的很小的将其忽略的假设下发展出一个在时间域下的近似解。研究结果发现肤层的影响会随着时间的增加而减少,此外由于井壁上的浓度在初期明显地下降,所以若采用第一类 (Dirichlet) 边界条件来描述浓度分布会高估其在井壁上的浓度。由于近似解有着相较半解析解容易计算的优点,而且当 时浓度预测能够有着相当好的准确性,因此是一个用来进行风险评估时的良好工具。 This study develops a mathematical model for contaminant transport due to well injection in a radial two-zone confined aquifer system, which is composed of a wellbore skin zone and a formation zone. The model contains two transient equations describing the contaminant concentration distributions; one is for contaminant transport in the skin zone while the other is for transport in the formation zone. The contaminants are injected into the well with given dispersive and advective fluxes; therefore, the well boundary is treated as a third-type (Robin) condition. The solution of the model derived by the method of Laplace transforms can reduce to a single-zone solution in the absence of the skin zone. In addition, an approximate solution in the time domain is also developed by neglecting dispersion for the case that the contaminants move away from the injection well. Analysis of the semi-analytical solution showed that the influence of the skin zone on the concentration distribution decreases as time elapses. The distribution will be over-estimated near the wellbore if the constant concentration (Dirichlet) condition is adopted at the well boundary. The approximate solution has advantages of easy computing and yield reasonable predictions for Peclet numbers larger than 50, and thus is a practical extension to existing methods for designing aquifer remediation systems or performing risk assessments. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT070151711 http://hdl.handle.net/11536/76050 |
显示于类别: | Thesis |