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*Wave-Torsethaugen |
 
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*Wave-Torsethaugen
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*Wave-Torsethaugen |
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To specify a Torsethaugen random sea wave spectrum or spectra.
Refer to Torsethaugen Wave for further information on this feature.
Blocks of lines which define the wave loading parameters.
Block defining Torsethaugen spectra with equal area discretisation. The second line can be repeated as often as necessary:
FREQUENCY=AREA
Hs, Tp, Max. Freq. Increment, Cut-off Freq., No. of
Harmonics, Wave Directions [, Dominant Direction] [, Wave
Spreading Exponent] [, Fetch Factor]
Block defining Torsethaugen spectra with geometric progression discretisation. The second line can be repeated as often as necessary:
FREQUENCY=GP
Hs, Tp, Cut-off Freq., Geometric Progression Factor, Wave
Directions [, Dominant Direction] [, Wave Spreading
Exponent] [, Fetch Factor]
The Wave Spreading Exponent for random sea analyses must be an even integer and defaults to 2. The Wave Spreading Exponent is omitted for frequency domain analyses and should not be specified for this type of analysis.
To define a Torsethaugen random sea wave spectrum or spectra, to be discretised using equal area increments.
Input: |
Description |
Wave Height: |
The spectrum significant wave height Hs. |
Peak Period: |
The spectrum peak period Tp in seconds. |
Max Frequency Increment: |
The maximum frequency increment in Hz. to be used in the spectral discretisation. See Note (b). This parameter defaults to a value of 0.05 Hz. |
Cut – off Frequency: |
The cut-off or Nyquist frequency in Hz. This parameter defaults to a value of 0.5 Hz. |
No. of Harmonics: |
The number of harmonics to be used in the spectral discretisation. |
Wave Directions: |
The number of wave directions. The default of 1 gives a uni-directional random sea, greater than 1 gives a multi-directional sea. See Note (c). |
Dominant Direction: |
The wave direction in a uni-directional sea, or the dominant wave direction in a multi-directional random sea, measured in degrees anticlockwise from the global Y direction. The default is 0°. |
Wave Spreading Exponent: |
The exponent used in distributing wave energy between directions in a multi-directional random sea. This entry defaults to 2. See Note (c). |
Fetch Factor |
Factor dependant on fetch. This entry defaults to 6.6. See Note (d). |
To define a Torsethaugen random sea wave spectrum or spectra, to be discretised using a geometric progression of frequencies.
Input: |
Description |
Wave Height: |
The spectrum significant wave height Hs. |
Peak Period: |
The spectrum peak period Tp in seconds. |
Cut – off Frequency: |
The cut-off or Nyquist frequency in Hz. This parameter defaults to a value of 0.5 Hz. |
Geometric Progression Factor: |
The geometric progression factor for the spectral discretisation. See Note (b). This parameter defaults to a value of 0.02. |
No. of Wave Directions: |
The number of wave directions. The default of 1 gives a uni-directional random sea, greater than 1 gives a multi-directional sea. See Note (c). |
Dominant Direction: |
The wave direction in a uni-directional sea, or the dominant wave direction in a multi-directional random sea, measured in degrees anticlockwise from the global Y direction. The default is 0°. |
Wave Spreading Exponent: |
The exponent used in distributing wave energy between directions in a multi-directional random sea. This entry defaults to 2. See Note (c). |
Fetch Factor |
Factor dependant on fetch. This entry defaults to 6.6. See Note (d). |
(a)A random sea analysis can consider combinations of wave spectra and/or regular waves. Refer to Wave Loading for a description of the available wave specification combinations.
(b)The wave spectrum may be discretised into segments based an equal area approach (which divides the area under the spectrum into segments of equal area) or a geometric progression approach (based on frequency increments that form a geometric progression). Refer to Spectrum Discretisation for a detailed discussion of this discretisation procedure.
(c)A multi-directional random sea is defined in terms of a dominant wave direction and the number of wave directions. Refer to Wave Energy Spreading for further information on this feature.
(d)The suggested value of 6.6 for fetch factor relates to the metric unit system, in which a factor of 6.6 m-1/3s is typically used. If you are using the imperial unit system, you should adjust the fetch factor accordingly.