HR: 08:45h
AN: H21H-04    [Abstracts]
TI: Pore-scale Analysis of Residual NAPL Blob Mobilization and Solubilization in Porous Media
AU: * Yoon, S
EM: sunnydream@neo.tamu.edu
AF: Texas A&M Univeristy, Department of Civil Engineering, 3136 TAMU, College Station, TX 77843-3136 United States
AU: Corapcioglu, Y
EM: yavuz@neo.tamu.edu
AF: Texas A&M Univeristy, Department of Civil Engineering, 3136 TAMU, College Station, TX 77843-3136 United States
AB: As a NAPL moves downward in a porous medium under gravitational forces, it leaves behind a discontinuous residual blob trapped by soil capillarity, causing a long-term source of contamination in subsurface environments. In this study we investigate solubilization and mobilization of trapped NAPL blobs by pore-scale mass and force balance analysis. Previous studies considered these two mechanisms separately in their analyses. Generally, mobilization of NAPL blobs was determined by using a trapping number, N_T, which is obtained by a combination of Capillary (Ca) and Bond (Bo) numbers. However blob solubilization is expressed in terms of dimensionless numbers such as Damkohler number, (Da), Peclet number (Pe), and Reynolds number (Re). Most previous studies were limited to describe the motion of NAPL blobs initiated when a balance of viscous, buoyancy and capillary forces expressed in terms of Ca, Bo and N_T is satisfied. In addition, solubilization prior to mobilization was not considered at the onset of NAPL blob movement assuming that mobilization occurs when solubilization is at or near equilibrium. In this study, we focus on simultaneous interaction between mobilization and solubilization of NAPL blobs, determining that solubilization induces smaller blob size and contributes to mobilization of NAPL blobs. Furthermore, N_T, an indicator of displacement performance, is evaluated by incorporating various dimensionless numbers such as Da, Ca, and Bo in the analysis. We compared our work with other studies focusing solely on mobilization of NAPL blobs. Simultaneous consideration of solubilization and mobilization provide a better understanding of flow behavior of blobs at the pores. Of particular interest, while the value of N_T was determined by others under equilibrium conditions, the newly developed N_T could be evaluated at nonequilibrium incorporating the rate-limited dissolution related to change in blob size. Investigation of morphological characteristics of the blobs factoring surface interfacial area and blob size distribution contribute further to our understanding of critical conditions of NAPL blob mobilization and determining the NAPL fate during transition from dissolution to mobilization.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: Fall Meeting 2005