EFDC+ has now fully incorporated the Marine Hydrokinetic (MHK) module to simulate placement and potential effects of installation and operation of  turbines and wave energy converters in rivers, tidal channels, ocean currents, and other waterbodies. The code is implemented based on Sandia National Laboratories modified Environmental Fluid Dynamics Code (SNL-EFDC) (James, 2010).

As shown in Figure 1 the MHK Devices sub tab may be accessed from the Domain tab on the main form. Here the user is informed how many devices have been defined and how many cells contain devices. Select the Define/Modify button to setup the MHK devices.

Figure 1  Domain Tab – MHK Devices settings

1.1         MHK Devices – General Tab

In Marine Hydrokinetics Device Options form, the General tab is where the user specifies whether MHK calculations will be used in EE or not by checking the Use MHK Devices in the EFDC Simulation checkbox as shown in Figure 2.

For MHK devices, it is important to specify the power extracted from the flow. There are different methods for computing power extracted from flow, though currently only one method is enabled. The method is to use the specified thrust coefficient that is multiplied by velocity cubed. The user may specify the Velocity Source for Power Calculations required for computation of power. The available options are: local cell velocity and the upstream velocity.

The MHK Output Option frame provides options for text based reporting of the output. These options include:

• Energy fluxes access a transverse section upstream and downstream of the device
• Average velocity and the Z-profile for the tidal reference model at throat
• Average velocity and surface velocity for the reference model
• Outputs for straight-channel calibration model of the wake structure.

Figure 2  MHK Device Options – General tab.

The 3D Object (COLLADA) of MHK from provides the option to browse COLLADA files that can be viewed from View3D.  By default these files are saved here:

C:\Program Files (x86)\DSI\EFDC_Explorer8.2\Resources

An example of the default turbine is shown in Figure 3 . The user can adjust the settings for the MHK device display by selecting Option in the General tab or with CTRL K in View3D with the options shown in Figure 4.

Figure 3  MHK device in View3D.

Figure 4  MHK device viewing options in View3D.

1.2         Device Definitions Tab

The Device Definitions tab is shown in Figure 5. Here the user specifies the number of MHK devices in the model and the number will be reflected in the MHK Device Definitions dropdown box. The device names can be specified by the user, and for each device the user must specify the device dimensions and a range of coefficients (Figure 11). Guidance on how to determine these definitions can be found in the SNL user guide (James, 2010).

Figure 5  MHK Device Options – Device Definitions tab.

1.3         Device Cell Assignments

The Device Cell Assignments tab is where the user should specify the location for the devices. The user can enter either Easting and Northing or I, J index for the cell to specify locations. The user can type or copy and paste the device number which correspond to that cell as shown in Figure 6.

The Export List button will export the Easting, Northing and MHK Device number as a .DAT file for use by the user externally to EE. 

Figure 6  MHK Device Options – Device Cell Assignments tab.

1.4         Device Cell Initialization Tab

The Device Cell Initialization tab allows the user to set the MHK devices from an external file which is based on XY data as shown in Figure 7.  Two options are provided, Read XY Pairs from a File for Discrete Cell Assignments, and Assign MHK Devices using Polygons with MHK IDs. This latter file is in the P2D format (native EE file).

Figure 7  MHK Device Options – Device Cell Initialization tab.