|Water Science and Engineering 2013, 6(2) 153-163 DOI: 10.3882/j.issn.1674-2370.2013.02.004 ISSN: 1674-2370 CN: 32-1785/TV|
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Anisotropic diffusion of volatile pollutants at air-water interface
Li-ping CHEN*1, Jing-tao CHENG1, Guang-fa DENG2
1. College of Urban Construction and Safety Engineering, Nanjing University of Technology, Nanjing 210009, P. R. China
The volatile pollutants that spill into natural waters cause water pollution. Air pollution arises from the water pollution because of volatilization. Mass exchange caused by turbulent fluctuation is stronger in the direction normal to the air-water interface than in other directions due to the large density difference between water and air. In order to explore the characteristics of anisotropic diffusion of the volatile pollutants at the air-water interface, the relationship between velocity gradient and mass transfer rate was established to calculate the turbulent mass diffusivity. A second-order accurate smooth transition differencing scheme (STDS) was proposed to guarantee the boundedness for the flow and mass transfer at the air-water interface. Simulations and experiments were performed to study the trichloroethylene (C2HCl3) release. By comparing the anisotropic coupling diffusion model, isotropic coupling diffusion model, and non-coupling diffusion model, the features of the transport of volatile pollutants at the air-water interface were determined. The results show that the anisotropic coupling diffusion model is more accurate than the isotropic coupling diffusion model and non-coupling diffusion model. Mass transfer significantly increases with the increase of the air-water relative velocity at a low relative velocity. However, at a higher relative velocity, an increase in the relative velocity has no effect on mass transfer.
|Keywords： volatile pollutant interfacial mass transfer anisotropic diffusion STDS anisotropic coupling diffusion model|
|Received 2012-02-14 Revised 2012-12-21 Online: 2013-04-05|
This work was supported by the National Natural Science Foundation of China (Grant No. 51109106) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 11KJB570001).
|Corresponding Authors: Li-ping CHEN|
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