Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Spicer, Tom O. III

Committee Member

Havens, Jerry A.

Second Committee Member

Walker, Heather L.

Third Committee Member

Roe, Larry A.

Fourth Committee Member

Ford, David M.

Keywords

Along-wind dispersion; Atmosphere; Finite-duration releases; Modeling; Wind tunnel

Abstract

Along-wind dispersion, or stretching of the cloud in the direction of the wind, plays an important role in the concentration and modeling of contaminant releases in the atmosphere. Theoretical and empirical derivations were compared for appropriate parameterization of along-wind dispersion. Available field data were analyzed to evaluate and improve previous parameterizations of the along-wind dispersion coefficient, σ_x. An experimental test program was developed and executed in an ultra-low speed wind tunnel at the Chemical Hazards Research Center to determine the effects of the time distribution coefficient on true finite-duration releases from an original area source. Multiple wind speeds, release durations, and downwind distances were investigated with ensemble averages for improved quality of the cloud characteristics for each set of test conditions. An overall relationship between the time of peak arrival (TOPa) and the time distribution coefficient σ_t= 0.23*TOPa was demonstrated across all parameters. From this relationship, the along-wind dispersion coefficient can be accurately predicted and scaled appropriately. Additional relationships for the leading and trailing edges of the cloud are appropriately modeled.

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