Flexcom > Data Inputs > $LOAD CASE

Purpose

To specify a JONSWAP random sea wave spectrum or spectra.

Theory

Refer to Jonswap Wave for further information on this feature.

Keyword Format

Blocks of lines which define the wave loading parameters.

Block defining Jonswap spectra in the normal format with equal area discretisation. The second line can be repeated as often as necessary:

FREQUENCY=AREA [, SPEC=NORMAL]

Peak Frequency, Philips Constant, Peakedness, Max. Freq.

Increment, Cut-off Freq., No. of Harmonics, Wave Directions

[, Dominant Direction] [, Wave Spreading Exponent]

Block defining Jonswap spectra in the normal format with geometric progression discretisation. The second line can be repeated as often as necessary:

FREQUENCY=GP [, SPEC=NORMAL]

Peak Frequency, Philips Constant, Peakedness, Cut-off Freq.,

Geometric Progression Factor, Wave Directions [, Dominant

Direction] [, Wave Spreading Exponent]

Block defining Jonswap spectra in the Hs/Tz format with equal area discretisation. The second line can be repeated as often as necessary:

FREQUENCY=AREA, SPEC=HSTZ

Hs, Tz, Max. Freq. Increment, Cut-off Freq., No. of Harmonics, Wave Directions [, Dominant Direction] [, Wave Spreading

Exponent]

Block defining Jonswap spectra in the Hs/Tz format with geometric progression discretisation. The second line can be repeated as often as necessary:

FREQUENCY=GP, SPEC=HSTZ

Hs, Tz, Cut-off Freq., Geometric Progression Factor, Wave Directions [, Dominant Direction]

[, Wave Spreading Exponent]

Block defining Jonswap spectra in the Hs/Tp format with equal area discretisation. The second line can be repeated as often as necessary:

FREQUENCY=AREA, SPEC=HSTP

Hs, Tp, Max. Freq. Increment, Cut-off Freq., No. of Harmonics, Wave Directions [, Dominant Direction]

[, Wave Spreading Exponent]

Block defining Jonswap spectra in the Hs/Tp format with geometric progression discretisation. The second line can be repeated as often as necessary:

FREQUENCY=GP, SPEC=HSTP

Hs, Tp, Cut-off Freq., Geometric Progression Factor, Wave Directions [, Dominant Direction] [, Wave

Spreading Exponent]

Block defining Jonswap spectra in the Hs/Tp/Gamma format with equal area discretisation. The second line can be repeated as often as necessary:

FREQUENCY=AREA, SPEC=HSTPGAMMA

Hs, Tp, Peakedness, Max. Freq. Increment, Cut-off Freq., No. of Harmonics, Wave Directions

[, Dominant Direction] [, Wave Spreading Exponent]

Block defining Jonswap spectra in the Hs/Tp/Gamma format with geometric progression discretisation. The second line can be repeated as often as necessary:

FREQUENCY=GP, SPEC=HSTPGAMMA

Hs, Tp, Peakedness, Cut-off Freq., Geometric Progression Factor, Wave Directions [, Dominant Direction] [,

Wave Spreading Exponent]

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.

wave - jonswap - Standard - Equal Area

Purpose

To define a Jonswap random sea wave spectrum using the normal or standard format, to be discretised using equal areas.

Table Input

Input:	Description
Peak Frequency:	The spectrum peak frequency fp in Hz.
Phillips Constant:	Phillips constant α, typically 0.0081 (the default).
Peakedness Parameter:	The spectrum peakedness parameter γ.
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).

wave - jonswap - Standard - Geometric Progression

Purpose

To define a Jonswap random sea wave spectrum using the normal or standard format, to be discretised using a geometric progression of frequencies.

Table Input

Input:	Description
Peak Frequency:	The spectrum peak frequency fp in Hz.
Phillips Constant:	Phillips constant α, typically 0.0081 (the default).
Peakedness Parameter:	The spectrum peakedness parameter γ.
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).

wave - jonswap - HS/TZ - Equal Area

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs and Tz, to be discretised using equal area increments.

Table Input

Input:	Description
Wave Height:	The spectrum significant wave height Hs.
Up-Crossing Period:	The mean zero up-crossing period Tz 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).

wave - jonswap - HS/TZ - Geometric Progression

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs and Tz, to be discretised using a geometric progression of frequencies.

Table Input

Input:	Description
Wave Height:	The spectrum significant wave height Hs.
Up-Crossing Period:	The mean zero up-crossing period Tz 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).

wave - jonswap - HS/TP - Equal Area

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs and Tp, to be discretised using equal area increments.

Table Input

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).

HS/TP - Geometric Progression

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs and Tp, to be discretised using a geometric progression of frequencies.

Table Input

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).

HS/TP/Gamma - Equal Area

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs, Tp and γ, to be discretised using equal area increments.

Table Input

Input:	Description
Wave Height:	The spectrum significant wave height Hs.
Peak Period:	The spectrum peak period Tp in seconds.
Peakedness Parameter:	The spectrum peakedness parameter γ.
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).

HS/TP/Gamma - Geometric Progression

Purpose

To define a Jonswap random sea wave spectrum or spectra in terms of Hs, Tp and γ, to be discretised using a geometric progression of frequencies.

Table Input

Input:	Description
Wave Height:	The spectrum significant wave height Hs.
Peak Period:	The spectrum peak period Tp in seconds.
Peakedness Parameter:	The spectrum peakedness parameter γ.
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).

Notes

(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 on 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.