Following is the appearance of the Diffusion tab of the Reservoir Coefficients dialog:
Following is a description of the parameters associated with Diffusion. Refer to the main Reservoir Coefficients page for information on other categories of coefficients. To save the changes made when closing this dialog, click OK. To ignore changes, click Cancel.
The reservoir may use the wind mixing method or the density gradient method, or the larger of the two. To use only the wind mixing method, set Max. Diffusion Coefficient in the density gradient coefficients to 0. To use only the density gradient method, set Max. Diffusion Coefficient in the wind mixing method to 0. When using both, it is best to set Min. Diffusion Coefficient to 0. All of these coefficients applies to each reservoir segment in a multiple segment simulation or to the whole reservoir in a single segment simulation.
Inflow Entrainment is percent of flow entrained from layers above when inflow enters reservoir and seeks a depth with the same density (0 – 10%).
Min. Neg. Density Gradient is the smallest density gradient which will not induce complete mixing. (<=0 kg / m4)
Wind Mixing:
Min. Diffusion Coefficient is the portion of the diffusion coefficient which is independent of wind speed. (1.0E-7 – 5.0E-5 m2 / s)
A1 is the proportionality parameter between wind speed and diffusion. (1.0E-4 – 5.0E-3)
A2 is the wind mixing depth penetration factor. (normally 4.6, unitless)
Max. Diffusion Coefficient is the maximum diffusion coefficient regardless of wind speed. (5.0E-4 m2 / s)
Density Gradient Mixing:
Critical Density Gradient is the density gradient above which diffusion is impeded. (1.0E-6 – 5.0E-6 / m)
Max. Diffusion Coefficient is the diffusion coefficient when the density gradient is less than the critical density gradient. (1.5E-4 – 1.0E-3 m2 / s)
Diffusion Attenuation Exponent is the attenuation exponent of density gradient used in calculating the diffusion coefficient. (-1.0 to -0.7, unitless)
When the Apply Changes To Selected button is checked, changes made to the coefficients of the reservoir segment being edited will be made to all selected reservoir segments. When the Apply Changes To All button is checked, changes made to the coefficients of the reservoir segment being edited will be made to all reservoir segments.