Quadratic Wind Coefficients

The Quadratic Wind Coefficient editor allows you to define wind force coefficients for a body. Wind forces are calculated based on the wind velocity and the specified coefficients.

1. Type

Two types of wind coefficients are available:

1.1. Classic

Classic wind coefficients are given as a function of the relative wind direction only.

When Classic type is selected, the following parameters are available:

1.1.1. Wind Area

  • Wind Area: Characteristic area for admittance function, \(m^2\)

  • Default value: 2000.0

See the Theory Manual for details on the admittance function.

1.1.2. Reference Height

  • Reference Height: Height referred to still water level for which wind velocity will be calculated, \(m\)

  • Default value: 10.0

1.1.3. Symmetry

The symmetry option determines how wind coefficients are specified across different directions:

  • No symmetry: Coefficients must be specified for the full range [0, 360] degrees. Coefficients at 0 and 360 degrees must be equal.

  • Symmetry about Y=0: Coefficients are specified for [0, 180] degrees. Both 0 and 180 degrees must be included. This represents single symmetry about the x-z plane.

  • Double symmetry: Coefficients are specified for [0, 90] degrees. Both 0 and 90 degrees must be included. This represents double symmetry about both x-z and y-z planes.

1.1.4. Coefficient Table

The coefficient table displays the wind force coefficients for each direction. Each row contains:

  • Direction: Wind direction, [deg]

  • C1 through C6: Wind force coefficients for degrees of freedom 1-3 \(N \cdot s^2/m^2\), and 4-6 \(N \cdot s^2/m\)

1.2. Position dependent

Position dependent wind coefficients are given as a function of:

  • Relative wind direction

  • Body vertical position

  • Body roll angle

  • Body pitch angle

When Position dependent type is selected, the following parameters are available:

1.2.1. Wind Area

  • Wind Area: Characteristic area for admittance function, \(m^2\)

  • Default value: 2000.0

1.2.2. Reference Height

  • Reference Height: Height referred to still water level for which wind velocity will be calculated, \(m\)

  • Default value: 10.0

1.2.3. File Name

  • File Name: Path to the external file containing the position dependent wind coefficients

The force coefficients in the file must be specified in \(\frac{kN}{\frac{m}{s}}\) for translational degrees of freedom and \(\frac{kN}{s}\) for rotational degrees of freedom.

See description of the external file format here.