Visualizing hydraulic zones of a vertical circulation well in presence of ambient flow

Abstract

a b s t r a c tAlthough vertical circulation well (VCW) has been widely applied for aquifer remediation and hydrogeological parameter estimation for three decades, few studies have focused on the hydraulic zone visualization, and the spatial scale of hydraulic zones as functions of VCW parameters. This study provided a numerical method to visualize 3D steady-state flow field induced by VCW in a confined aquifer in presence of an ambient flow. Mathematical model for velocity field is established based on the superposition principle, and the fourth-order Runge-Kutta method is adopted to perform particle tracking. Visualization results illustrate that 3D flow regime can be divided into Recirculation, Capture, and Discharge zones. An integrated dimensionless parameter Q D is introduced to account for the relative strength of VCW flow against ambient flow. Comparison is performed through simulations by different Q D -d D combinations, where d D is the dimensionless distance between injection and extraction screens. Results demonstrate that: (1) a Q D -d D breakthrough line can be established to mark the occurrence of circulatory flow; (2) the effect of Q D on the size of recirculation zone is significant when Q D is smaller than 3.5, while d D becomes more influential if Q D is larger; (3) the extent of capture and discharge zone enlarges as Q D and/or d D increases.

Optimization Strategies for in Situ Groundwater Remediation by a Vertical Circulation Well Based on Particle‐Tracking and Node‐Dependent Finite Difference Methods

“…The conceptual model of groundwater flow associated with a VCW system is shown in Figure 1. The assumptions are similar to those in the studies of Philip and Walter (1992) and Xia et al (2019) Equations 1-5 have analytical solutions of drawdown distribution as demonstrated in previous studies (e.g., Chen et al, 2010Chen et al, , 2011Sutton et al, 2000;Zlotnik & Ledder, 1996), where the specific discharge (or Darcy velocity) distribution can be calculated based on Darcy's law, and the following expressions;…”

“…The conceptual model of groundwater flow associated with a VCW system is shown in Figure 1. The assumptions are similar to those in the studies of Philip and Walter (1992) and Xia et al (2019) as follows. (1) The aquifer is confined, homogeneous, vertically anisotropic and horizontally isotropic, and radially infinite with a finite constant thickness.…”

“…The work by Philip and Walter (1992) and Xia et al (2019) traced particle paths to characterize the capture zone in a VCW flow field while Cirpka and Kitanidis (2001) placed emphasis on the description of travel time‐based concentration during reactive transport through tandem VCWs. Visualization of VCW flow field alone by Philip and Walter (1992) and Xia et al (2019) still has limitations in optimizing design parameters, because the area of capture zone is merely a qualitative representation, which indicates that a more quantitative and user‐friendly index is needed. In terms of computational efficiency, the time step Δ t in the fourth‐order Runge‐Kutta algorithm must be adjusted as local velocity changes, otherwise the algorithm becomes computationally too expensive for practical use (Xia et al, 2019).…”

“…The other is the semianalytical method of Pollock (1988), as applied in the study of Cirpka and Kitanidis (2001). The work by Philip and Walter (1992) and Xia et al (2019) traced particle paths to characterize the capture zone in a VCW flow field while Cirpka and Kitanidis (2001) placed emphasis on the description of travel time-based concentration during reactive transport through tandem VCWs. Visualization of VCW flow field alone by Philip and Walter (1992) and Xia et al (2019) still has limitations in optimizing design parameters, because the area of capture zone is merely a qualitative representation, which indicates that a more quantitative and user-friendly index is needed.…”

Comment on “Tu et al., An Analytical Solution of Groundwater Flow in a Confined Aquifer With a Single Well Circulation System, Water Resources Research, First Published: 12 June 2020.”

“…This report describes a number of contributions by the late B. Herrling and J. Stamm, inventors and patent holders for a vertical circulation well remediation technology for groundwater as well as by other researchers, for example, Herrling and Stamm (1992), Philip and Walter (1992), Chen and Knox (1997), Knox et al (1997), and many others. Tu et al (2020), along with Tu et al (2019) and Ni et al (2011), failed to acknowledge relevant post-1998 literature, including publications by Xia et al (2019), Kahler and Kabala (2018), Jin et al (2016), Chen et al (2010), Johnson and Simon (2007), and many others. Tu et al (2020), along with Tu et al (2019) and Ni et al (2011), missed applications of vertical circulation wells for aquifer characterization, and, in particular, contributions from this author, including Kabala and Xiang (1992), Kabala (1993), and others, as well as those from V. Zlotnik and co-workers, including Zlotnik and Ledder (1996), Peursem et al (1999), and others.…”