<< Click to Display Table of Contents >> Navigation:  Flexcom > Data Inputs > $LOAD CASE >
*Current

Purpose

To specify current loading.

Theory

Refer to Current Loading for further information on this feature.

Keyword Format

A block of lines whose format depends on the current type.

Block of lines defining a current that is constant with depth:

TYPE=UNIFORM

Velocity[, Direction ]

Block of lines defining a piecewise linear current. The second line is repeated as often as necessary to define the current profile:

TYPE=PIECEWISE LINEAR [, OPTION=Specification Option] [, LEVEL=Level Option]

Elevation, Velocity[, Direction]

One line specifying a user defined subroutine:

TYPE=SUBROUTINE, USER=File Name

At least two points must be defined for a piecewise linear current. The user subroutine option is not relevant for frequency domain dynamic analysis. Direction defaults to 0. Specification Option can be either ASCEND (the default) or DESCEND, defining the current profile in terms of distance above the datum X=0 or distance below the MWL, respectively. Level Option can be either MWL or AMBIENT (the default) to specify current stretching, see Note (f) below. File Name should include the entire path of the user subroutine file with its extension. If a file name or any part of its path contains spaces then it should be enclosed in double quotation marks.

Uniform Current

Purpose

To specify a horizontal current velocity that is uniform with depth.

Table Input

Notes

(a)The specification of current is optional. By default, no current is included in the analysis.

(b)If a seabed is not included in the model then the current is applied only above the datum X=0.

Piecewise Linear Current

Purpose

To define a horizontal current velocity distribution that is varying in magnitude and direction with depth.

Table Input (Elevation Specification)

Table Input (Depth Specification)

Table Input (Water Surface)

Notes

(a)A minimum of two points is required to define a piecewise linear current distribution.

(b)The current can be specified at arbitrary depths below the datum in the case of a sloping or arbitrary seabed.  If a seabed is not included in the model then the current is applied only above the datum.

(c)Current velocity and direction at elevations intermediate to those specified here are found by linear interpolation.

(d)Below the lowest elevation specified, the current velocity and direction are assumed constant, with values equal to those at the lowest elevation.

(e)Above the highest elevation specified, the current velocity and direction are assumed constant with values equal to those at the highest elevation.

(f)Flexcom by default applies current based on the depth relative to the AMBIENT water surface. In this case, the current velocity distribution is “stretched” (or “compressed”) so that the velocity at the ambient water surface (rather than at the MWL) is constant throughout an analysis. With the alternative MWL option, the current velocity distribution remains unaltered throughout an analysis, regardless of the ambient water surface elevation.

(g)The specification of current is optional. By default, no current is included in the analysis.

User-Subroutine Current

Purpose

To specify the name of the DLL file containing the current user-subroutine.

Table Input

Notes

(a)This table is not relevant for frequency domain dynamic analysis.