In the General tab, the Turbulence Options frame provides a number of options. When the user selects the Modify button form, three tabs will be displayed: Turbulent Diffusion, Turbulent Intensity, and Miscellaneous. These tabs are used to edit various hydrodynamic options such as Horizontal Viscosity, Vertical Viscosity, and the Standard Computational Scheme for vertical turbulence. These options are described in the following sub-sections for each tab.

Turbulent Diffusion

EFDC Hydrodynamic Options & Parameters#Figure 1  tab contains frame for 'Horizontal Kinematic Eddy Viscosity & Diffusivities Options,' Vertical Eddy Viscosities & Diffusivities,' and 'Subset Cells to Apply Horizontal Diffusivity.'

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The frame for Horizontal Kinematic Eddy Viscosity and Diffusivities Options provides options to enable/disable the Horizontal Momentum Diffusion (HMD) capability of EE.  If the Disable HMD option is selected (equivalent to flag ISHMD=0 in the EFDC.inp file), the Background/constant Horizontal Eddy Viscosity (AHO) is set by the user.

EEMS supports a spatially variable AHO option.  When the Spatially Vary checkbox is checked, EFDC+ computes a separate AHO for each cell using the expression ABS (AHO) * DX * DY. This approach reduces the numerical diffusion error when the models have a large range of cell sizes.

When using the Activate HMD with Smagorinsky option (equivalent to ISHMD=1), the user should set the Smagorinsky’s Coefficient (AHD), in the Eddy Diffusivity (Dimensionless) text box. When Activate HMD with Smagorinsky is selected then EE will apply the background HMD as well as Smagorinsky’s subgrid, if AHD>0. With this option, the contaminant diffusion is off and not accounted for.  If AHD=0 then the Viscosity (Constant) option will be used.

EEMS also supports a spatially variable AHD option. The user needs to check both of the Spatially Vary checkboxes, in which case the Assign button is also enabled.  Selecting the Assign button displays the form shown in Figure 2.  EE will create a new file called AHMAP.INP, which will store a cell-by-cell list of AHO and AHD.  If the AHO in the AHMAP file is a negative number, EFDC+ will use the cell area times the input value to compute the cell’s AHO according to the equation above.

Typically, a user wouldn’t have data for spatially interpolated AHO and AHD, rather it is expected to use this to assign constant values to certain regions. The AHO and AHD values can be assigned to the whole model domain using operators or constant values. They can also assign values of AHO and AHD to certain regions using polygon files.  To assign the AHO and AHD value using a polygon file, browse to the polygon file using the browse button on the form in Figure 2. Load the polygon file, select the value for AHO or AHD, and select Apply. When the user saves the project, EE creates an AHMAP.INP file.

Users can visualize AHO and AHD values in ViewPlan using the Fixed Params viewing option.

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When Activate HMD with Smagorinsky, Wall Drag and WC Diffusion is selected (equivalent to ISHMD=2), then full HMD is used as well as the wall effects. This option also applies diffusivities to all constituent transport, which includes salinity and temperature. This option should be used when simulating a very uniform flow system if constituent transport is needed. The resulting horizontal diffusivity from these options can be viewed from within ViewPlan, provided velocities are also available.  The vertical eddy viscosities and diffusivities (AV & AD arrays in EFDC, respectively) can also be viewed if the user configures the Internal Array Viewer (See Appendix A) to include these arrays.

The Vertical Eddy Viscosities & Diffusivities frame allows the user to set the Time Advance Filter and Vertical Eddy Viscosity as well as Vertical Molecular Diffusivity.  The Maximum Magnitude for Diffusivity Terms allows the user to set the Maximum Kinetic Eddy Viscosity as well as the Maximum Eddy Diffusivity.

Turbulent Intensity

Turbulence Intensity#Figure 3 tab shows tow frames. First frame has Vertical Turbulence Options and second frame has Turbulence Closure Constants. Generally, only the Vertical Turbulence Options are changed. At the current time, production runs should set the Advection Scheme to 1 and the Sub-Option to either Galerpin (Sub-option=1), Kantha and Clayson (Sub-option=2) or Kantha (Sub-option=3).

The Vertical Turbulence Limiting Options provide a drop down menu that allows the user to choose from three options: no length scale and RIQMAX limitation; to limit RIQMAX in the stability function only; and finally, to limit both the length scale and RIQMAX. When using multi-layer models and vertical turbulence is limiting, the Limit Length Scale and Limit RIQMAX option provides runs with less likelihood of model crashes.

The Wall Proximity Function also allows the user three options: no wall proximity effects on the turbulence, to be parabolic over depth wall proximity, and finally, open channel wall proximity.

The Turbulence Closure Constants may be changed after the Modify check box is selected. However, these constants should not be changed without good justification.

Miscellaneous

Further turbulence modification options are also available under the Miscellaneous tab shown below in EFDC Hydrodynamic Options & Parameters#Figure 4. These options allow various momentum corrections, which may be enabled with the Momentum Correction Flag. When the flag is set to zero, the momentum corrections are disabled; when set to 1, they are enabled.