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The additivity assumption underlying Giddings' coupling model for the eddydispersion in laminar flows through heterogeneous media is critically analyzed and a potential solution for its nonadditivity in the high velocity limit is presented. Whereas the unit cell in Giddings' model only consists of a single velocity bias step, the unit dispersion cell of the newly proposed model comprises two consecutive velocity bias steps. Consequently, the unit cell of this new model allows to account for the occurrence of an internal velocity bias rectification at high reduced velocities and is therefore additive in both the low and high velocity limit.
First, a mathematical expression for the velocity and diffusiondependency of the model's dispersion characteristics has been established. Subsequently, the physical behavior of the model is discussed. It is shown the relation between the eddydispersion plate height h and the reduced velocity ν can be expected to display a local maximum in systems where the transversal dispersion purely occurs by molecular diffusion, as is the case in perfectly ordered flowthrough media. In disordered media, where the transversal dispersion also contains a significant advective component, the model predicts a velocitydependency that is qualitatively similar to that described by Giddings' coupling model but, all other conditions being equal, converges to a significantly smaller horizontal asymptote at high reduced velocity. The latter might shed new light on earlier eddydispersion studies pursuing a quantitative agreement between experimental data and the Giddings model.
First, a mathematical expression for the velocity and diffusiondependency of the model's dispersion characteristics has been established. Subsequently, the physical behavior of the model is discussed. It is shown the relation between the eddydispersion plate height h and the reduced velocity ν can be expected to display a local maximum in systems where the transversal dispersion purely occurs by molecular diffusion, as is the case in perfectly ordered flowthrough media. In disordered media, where the transversal dispersion also contains a significant advective component, the model predicts a velocitydependency that is qualitatively similar to that described by Giddings' coupling model but, all other conditions being equal, converges to a significantly smaller horizontal asymptote at high reduced velocity. The latter might shed new light on earlier eddydispersion studies pursuing a quantitative agreement between experimental data and the Giddings model.
Originele taal2  English 

Artikelnummer  461195 
Aantal pagina's  10 
Tijdschrift  Journal of Chromatography. A 
Volume  1624 
Status  Published  2 aug 2020 
Vingerafdruk
Duik in de onderzoeksthema's van 'The checkerboard model for the eddydispersion in laminar flows through porous media. Part I: Theory and velocity field properties'. Samen vormen ze een unieke vingerafdruk.Projecten
 1 Actief

SRP6: SRP (Zwaartepunt): exploitatie van de voordelen van de Orde in Opsluiting voor een groenere chemie
Desmet, G., Denayer, J., Denayer, J., Desmet, G. & Denayer, J.
1/11/12 → 31/10/22
Project: Fundamenteel