# Currents

This part enables you to simulate currents, i.e. water particles moving at a constant velocity in time. It is possible to have a vertical variation of the currents velocity based on a shear power law (see the Currents of the theory manual).
It is also possible to import a current from file and use a user-defined vertical variation of the current velocity.

The word Currents (plural) is used so that it is not confused with the word 'current' in other situations

## General

### Principal angle

The angle of the currents relative to north (the y-axis). With the currents profile found with the power law, the angle cannot change with depth.

• Default value: 0
• Unit: $°$
• Range: -360 — 360

### Surface speed

The horizontal currents speed at the surface.

• Default value: 2
• Unit: ${\text{m}} \over {\text{s}}$
• Range: -∞ — ∞

### Ref. depth scheme

A reference depth is used to calculate the reduction in speed by depth. Either the actual depth is used or the user (you) sets the reference depth.
Note: The currents speed is always zero below the reference depth.

Options:

User defined:

The reference depth is set by the user (you). This option is used if a reference depth different from the actual depth should be used.

Actual depth (default):

The actual depth is used as the reference depth.

### Ref. depth

The reference depth used to calculate the currents speed.
Note: The currents speed is always zero below the reference depth.

• Default value: 50
• Unit: $\text{m}$
• Range: 0.001 — 1000

### Shape exponent

The exponent in the power law used to calculate currents speed. The exponent is minimum 0 and maximum 1. If 0, then the speed is constant (i.e. independent of depth). If 1 then the speed is decreasing linearly with depth (and is 0 at the reference depth).
Note: The currents speed is always zero below the reference depth.

• Default value: 1
• Unit:
• Range: 0 — 1

### Input file

The file that is imported to define the currents profile. If no file is chosen (i.e. if this parameter field is empty) then there is no currents (Note: By default this field is empty).

Note: this parameter is only accessible in the batch manager. In order to import a user-defined current in time simulation, use the Action buttons at the top of the parameter window.

the format of the currents input file is explained in the Currents file section.

• Default value:
• Unit: