Ocean Wave And Current Probability And Return Period

Calculate ocean wave height, wave period and current velocity from return period data using the Weibull, Gumbel or Frechet probability distributions.

The three parameter distribution and Z offset is used to account for a minimum value, the smallest event which can occur in any sample period. The best fit line is calculated for the data points using the least squares linear regression method. The regression is calculated for return period versus amplitude (the X and Z values are swapped). Use the Data Plot option on the plot bar to display the data points and the calculated best fit. The regression data points and regression parameters are displayed in the output view at the bottom of the page.

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Ocean Current Probability And Return Period Calculation Module
Ocean Wave Probability And Return Period Calculation Module
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CALCULATOR : Ocean Extreme Event Encounter Probability [FREE] ±

Calculate ocean wave and current exceedance probability, cumulative probability, and encounter probability from the return period.

The exceedance probability is the probability of the return period wave or current occurring in any sample period (for example the probability of a 20 year wave or current occurring in any sample period). The cumulative probability is the probability of the return period wave or current not occurring in any sample period (for example the probability of a 20 year wave or current not occurring in any sample period). The encounter probability is the probability of the return period wave or current occurring in the design period (for example the probability of a 20 year wave or current occurring in a 30 year design period).

Tool Input

sptype : Sample Period Type
- su : User Defined Sample Period
R : Return Period
D : Design Period

Tool Output

Pc : Cumulative Probability
Pe : Encounter Probability
Px : Exceedance Probability
S : Sample Period
nd : No Of Samples In Design Period
nr : No Of Samples In Return Period

CALCULATOR : Ocean Extreme Event Amplitude From Return Period Data Weibull Gumbel And Frechet Distribution [FREE] ±

Calculate general ocean current and wave extreme event amplitude from return period data using the Weibull, Gumbel or Frechet distributions (for example current velocity, wave height, wave period etc).

Enter the return period (R) and extreme event amplitude (A) data values as pairs separated by a comma or tab (X, Z), with each data pair on a new line. The data pairs can also be copied and pasted from a spreadsheet. Use the Data Plot option to plot the data points with the calculated linear regression best fit. The regression output is displayed at the bottom of the page.

Tool Input

sptype : Sample Period Type
- Su : User Defined Sample Period
offtype : Parameter Type
- Aou : User Defined Amplitude Offset
rtype : Regression Probability Distribution Type
Rdata : Return Period Data
Adata : Amplitude Data
R : Return Period

Tool Output

A : Amplitude
Ao : Amplitude Offset
Md : Median Amplitude
Mn : Mean Amplitude
Mo : Mode Amplitude
S : Sample Period
r : Correlation Coefficient

CALCULATOR : Ocean Wave And Current Seabed Velocity From Return Period Data JONSWAP Seabed Spectrum [PLUS] ±

Calculate ocean wave and current seabed velocity and zero crossing period from return period data using the Weibull, Gumbel or Frechet distributions.

The seabed significant wave induced velocity and zero crossing period are calculated from significant wave height and peak wave period using the JONSWAP spectrum with an Airy wave transformation. The calculation is optimised for seabed conditions and should not be used for elevations greater than half the water depth. The current velocity is calculated at the design elevation for either the logarithmic profile or the 1/7th power law profile.

Enter data values as sets of four values separated by a comma or tab (R, H, T, Ur), with each data set on a new line. The regression output is displayed at the bottom of the page.

Tool Input

spwtype : Wave Sample Period Type
- Swu : User Defined Wave Sample Period
spctype : Current Sample Period Type
- Scu : User Defined Current Sample Period
offtype : Probability Function Parameter Type
- Hou : User Defined Minimum Wave Height
- Tou : User Defined Minimum Wave Period
- Uou : User Defined Minimum Current Velocity
rtype : Linear Regression Type
roughtype : Seabed Roughness Type
- zou : User Defined Seabed Roughness
uctype : Current Velocity Type
gatype : Gamma Factor Type
- γu : User Defined Gamma
Rdata : Return Period Data
Hdata : Wave Significant Height Data
Tdata : Wave Peak Period Data
Udata : Current Velocity Data
R : Design Return Period
d : Water Depth
Z : Design Elevation Above Seabed
Zr : Reference Elevation Above Seabed

Tool Output

γ : Gamma Peak Enhancement Factor
ωp : Wave Peak Frequency
Ho : Minimum Wave Height
Hs : Significant Wave Height
Hsm : Mean Significant Wave Height
L : Wave Length
M0 : 0th Spectral Moment
M2 : 2nd Spectral Moment
Sc : Current Sample Period
Sw : Wave Sample Period
To : Minimum Wave Period
Tp : Peak Wave Period
Tpm : Mean Wave Period
Tz : Zero Upcrossing Period At Design Elevation
Uc : Current Velocity At Design Elevation
Uc/Ut : Current Velocity Over Total Velocity Ratio
Ur : Current Velocity At Reference Elevation
Urm : Mean Current Velocity At Reference Elevation
Us : Significant Wave Velocity At Design Elevation
Ut : Total Wave And Current Velocity At Design Elevation
cvg : Convergence Factor
kw : Wave Number
ro : Seabed Roughness
uo : Minimum Current Velocity At Reference Elevation

CALCULATOR : Ocean Wave And Current Velocity From Return Period Data Airy Stokes And Cnoidal Wave [PLUS] ±

Calculate ocean wave and current velocity and acceleration from return period data using the Weibull, Gumbel or Frechet distributions.

The wave velocity and acceleration are calculated using either the Airy wave, Cnoidal wave or Stokes wave profile. Wave phase angle can be defined by angle, displacement (x distance), or time. The design elevation can be defined on the seabed, at the wave surface (calculated for the wave phase angle), the wave trough, or user defined design elevation. The current velocity is calculated at the design elevation for either the logarithmic profile or the 1/7th power law profile.

Enter data values as sets of four values separated by a comma (R, H, T, Vr), with each data set on a new line. The regression output is displayed at the bottom of the page. Use the Result Plot option to plot acceleration, velocity and wave profile versus phase angle.

Tool Input

spwtype : Wave Sample Period Type
- Swu : User Defined Wave Sample Period
spctype : Current Sample Period Type
- Scu : User Defined Current Sample Period
offtype : Probability Function Parameter Type
- Hou : User Defined Minimum Wave Height
- Tou : User Defined Minimum Wave Period
- Uou : User Defined Minimum Current Velocity
rtype : Linear Regression Type
roughtype : Seabed Roughness Type
- zou : User Defined Seabed Roughness
uctype : Current Velocity Type
wavetype : Wave Type
phasetype : Phase Angle Type
- Θu : User Defined Phase Angle
- x : User Defined Displacement
- t : User Defined Time
ztype : Design Elevation Above Seabed Type
- Zu : User Defined Elevation
Rdata : Return Period Data
Hdata : Wave Height Data
Tdata : Wave Period Data
Udata : Current Velocity Data
R : Design Return Period
d : Water Depth
Zr : Reference Elevation Above Seabed

Tool Output

Θ : Wave Phase Angle
η : Wave Surface Relative To Mean Sea Level
Ah : Wave Horizontal Acceleration At Design Elevation
Am : Wave Acceleration Magnitude At Design Elevation
Av : Wave Vertical Acceleration At Design Elevation
Ho : Minimum Wave Height
Hsm : Mean Wave Height
Hw : Wave Height
L : Wave Length
Sc : Current Sample Period
Sw : Wave Sample Period
To : Minimum Wave Period
Tpm : Mean Wave Period
Tw : Wave Period
Urm : Mean Current Velocity At Reference Elevation
Vc : Current Velocity At Design Elevation
Vc/Vht : Current Velocity Over Total Horizontal Velocity Ratio
Vh : Wave Horizontal Velocity At Design Elevation
Vht : Total Horizontal Velocity At Design Elevation
Vm : Wave Velocity Magnitude At Design Elevation
Vr : Current Velocity At Reference Elevation
Vv : Wave Vertical Velocity At Design Elevation
Z : Design Elevation Above Seabed
Zs : Wave Surface Height Above Seabed
Zw : Wave Trough Height Above Seabed
c : Wave Celerity
cvg : Convergence Factor
ro : Seabed Roughness
uo : Minimum Current Velocity At Reference Elevation

CALCULATOR : Ocean Wave Velocity Reduction Factor [FREE] ±

Calculate wave velocity reduction factor from relative heading and spreading factor.

The spreading factor accounts for wave 'choppiness', the tendency for intersecting waves from multiple directions. Smaller spreading factor indicates more choppiness. A relative heading of ninety degrees is perpendicular to the structure.

Tool Input

sfactype : Shape Factor Type
- su : User Defined Spreading Factor
rdtype : Velocity Reduction Factor Type
Φ : Relative Wave Heading

Tool Output

Rdw : Wave Velocity Reduction Factor
kw : Wave Shape kw Factor
sf : Wave Shape Factor

CALCULATOR : Ocean Current Velocity Reduction Factor [FREE] ±

Calculate ocean current velocity reduction factor from relative heading to a pipeline or structure.

A relative heading of zero degrees is parallel to the pipeline or structure, or ninety degrees is perpendicular to the pipeline or structure.

Tool Input

hctype : Current Heading Type
- Φcu : User Defined Current Relative Heading

Tool Output

Φrc : Relative Current Heading
Rdc : Current Velocity Reduction Factor