Investigation of the Flux–Concentration Relation for Horizontal Flow in Soils
2019
George Kargas | Paraskevi Londra | Petros Kerkides
The objective of the present work is to investigate the flux&ndash:concentration (F(&Theta:)) relation, where &Theta: is the normalized soil volumetric water content for the case of one-dimensional horizontal flow, subject to constant concentration conditions. More specifically, the possibility of describing F(&Theta:) by an equation of the form F(&Theta:) = 1 &minus: (1 &minus: &Theta:)p+1 is examined. Parameter p is estimated from curve-fitting of the experimentally obtained &lambda:(&Theta:) data to an analytic expression of the form (1 &minus: &Theta:)p where &lambda: is the well-known Boltzmann transformation &lambda: = xt&minus:0.5 (x = distance, t = time). The results show that the equation of (1 &minus: &Theta:)p form can satisfactorily describe the &lambda:(&Theta:) relation for the four porous media tested. The proposed F(&Theta:) function was compared with the limiting F(&Theta:) function for linear and Green&ndash:Ampt soils and to the actual F(&Theta:) function. From the results, it was shown that the proposed F(&Theta:) function gave reasonably accurate results in all cases. Moreover, the analytical expression of the soil water diffusivity (D(&Theta:)) function, as it was obtained by using the equation for &lambda:(&Theta:) of the form (1 &minus: &Theta:)p, appears to be very close to the experimental D(&Theta:) data (root mean square error (RMSE) = 0.593 m2min&minus:1).
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