Scatter data

Scatter diagrams are often based on the hindcast data. They can be prepared directly from the hindcast data or be based on statistical long-term term distributions fitted to the hindcast data.

There are two types of scatter data in the Metocean Task

  • Omnidirectional Scatter Data

    • Contains compounded occurrences for all directions

  • Direction Dependent Scatter Data

    • Separates the occurences into wave sectors to enable directional spreading.

1. Scatter data editor

The scatter data has three sections

  • Wave

    • The wave data is the main section, with wave occurrences collected in Hs/Tp bins.

  • Wind

    • Split into several levels, giving possibility to define wind speed and direction for several heights.

    • The diagram size is governed by the wave diagram size, to ensure the same bins are defined for all data.

  • Current

    • Split into several levels, giving possibility to define current speed and direction for several depths.

    • The diagram size is governed by the wave diagram size, to ensure the same bins are defined for all data.

2. How to import scatter data from file

Using a tool like SIMAPy you can generate metocean data for import. You can find examples of this here

If you have a file containing metocean data you can

  • Right-click Metocean Task → Import metocean data

  • Locate the file to import and press Finish

3. How to create new scatter data

  • Scatter data is generated using the metocean task

    • Set up the the type of scatter data

    • Specify the scatter data calculation

    • Make a and run the condition


3.1. Generate a metocean task

Right click and choose new

  • Metocean Task

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  • Give the metocean task a name

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3.2. Choose Scatter Data

  • Choose the type of scatter data you want to model

    1. Omnidirectional Scatter Data

    2. Direction dependent Scatter Data

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3.3. Example: Choose omnidirectional data

  • Specify the input in the cells

    • Start values for significant wave height, Hs, and peak period, Tp

    • Stepping (=Delta)

    • Number of values you want

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  • Add data to the cells

    • This can be entered manually

    • or imported from the clipboard

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3.4. Enter data

  • Import from clipboard

  • If you have the data in excel, you may copy these cell and choose Import from clipboard Add data to the cells

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  • Enter data by typing in the cells

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3.5. Scatter data calculation

  • Set up scatter data calculation by right click New

    • Choose Scatter Data Calculation

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  • In the Scatter Data Calculation

    • Choose the Scatter Data: omni

    • Set wave directions: 0 deg

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3.6. Make a condition

  • Make a new metocean condition

  • Give it a name MyCondition

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  • In the condition

    • Choose ScatterDataCalculation in the drop down list

    • Run by clicking on the green icon

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3.7. Study the results

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Relation between the sea states and selected wind and current data

Procedure

  • For each sea state, \(H_{s}\),\(T_{p}\) and \(\theta_{}\)

    • for all wind speed levels

      • interpolate to find wind speed and direction using \(H_{s}\) and \(T_{p}\)

    • for all current speed levels

      • interpolate to find current speed and direction using \(H_{s}\) and \(T_{p}\)


Use of profiles to find the current speed

The current levels for different water depth can be calculated using the option From wind velocity for Scatter Data and Hind Cast Calculation.

The current speed is estimated using the wind speed in a given Wind reference level combined with two profile.

  • Wind Current Profile, \(f_{w2c}(z)\)

  • Base Current Profile, \(f_{cbase}(z)\)

    • The Base Current Profile is multiplied with the Base Current Speed, \(u_{mean}\)

\[U_{current}(Z)=u_{wind}(z_{ref})\cdot f_{w2c}(z) + u_{mean}\cdot f_{cbase}(z)\]

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