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Currents

Currents occurring independently of wave and swell are entered as depth profiles, and can be treated as constant values or evolving over time in both magnitude and direction. A quasi-static evolution can also be considered (to 'ramp' the load at the start of the analysis).

In the general area of the properties window you can edit the name of the current and change the displayed colour in the 3D View window.

Quasi-static evolution :

  • Constant: the full static current is applied from the beginning of the static analysis.

  • Linear: the current velocity is linearly increased during the quasi-static steps of the analysis. This is advised for complex problems including contacts with friction, to ensure the analysis can converge easily.

  • User defined: by clicking this option you can create and edit a list to define the evolution of current magnitude with analysis time-steps.

  • Wake effect accounted at step: to take into account the wake flow generated by a cylinder in a current and its effect on other cylinders at steps greater than the value specified.

  • Dipole effect accounted at step: to take into account the dipole flow generated by a cylinder in a current and its effect on other cylinders at step greater than the value specified.

Dynamic evolution :

  • Constant: the current defined is considered constant during the dynamic analysis

  • Varying with time: the current is linearly interpolated during the dynamic steps from the current profile given at the given dynamic time. To use this option, first enter the data for t=0, then enter a time-step for the next current profile and click 'Define profile at new time'. You can then enter a new profile in the new tab that appears in the table. You can repeat this until you have finished defining the evolution.

Current profile :

  • Depth steps: This sets the number of Z positions at which the current velocity and direction are specified.

  • Water depth: This sets the Z positions at which the current velocity and direction are specified. Note that the values input there must be negative since they refer to the vertical Z position (and not to the actual depth).

  • Velocity: This sets the velocity of the current profile as a function of the Z position.

  • Heading: This sets the heading (flowing direction) of the current profile as a function of the Z position. Headings are defined for the "to" direction with respect to the global X-axis of the model).