32. Wave models

The identification tag for this tutorial is PDS-AAW. Pregenerated input files for this tutorial are found in the folder named PDS-AAW in the provided tutorial input files.

32.1. Tutorial overview

This tutorial covers:

  • Wave models
  • Using the JONSWAP wave spectrum
  • Using the $WaveSeed property
  • The spreading function
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Fig. 32.1 Waves in PostPDS in rendered mode

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Fig. 32.2 Waves in PostPDS in engineering mode

32.2. Using advanced wave profiles

Note

  • Using advanced wave profiles.
  • ProteusDS allows the use of several types of wave profiles in simulation.
  • The most basic wave profile is the Airy wave (Stokes first order). The free surface elevation of one wave component is sinusoidal.
  • A Stokes second order wave is also available, which includes higher order terms to more accurately represent steeper waves.
  • The Pierson-Moskowitz wave spectrum represents a fully developed sea.
  • Finally, the JONSWAP spectrum is also available. The JONSWAP spectrum accounts for developing seas.

32.3. Applying a JONSWAP wave spectrum

  • Create a new project.
  • In the environment input file, use a JONSWAP wave spectrum by setting $WaveType 8.
  • When using a wave spectrum, certain follower properties are required. Use the following property declarations in the environment input file:
$WaveType 8
$WaveHeading 0
$WavePeriod 5
$WaveHeight 2
$WaveSegments 100
$WaveSeed 12345
$WaveSpreadingFunction 1
$SpreadingFunctionConstant 2

Note

  • The $WaveSegment property determines the number of discrete waves for the simulation to use. By taking the number of wave segments and wave period, the amount of time before the sea state repeats can be calculated. The formula used to determine the length of non-repeating waves is provided in the ProteusDS User Manual.
  • The $WaveSeed property is used as the seed for a random number generator. This property allows for consistent consecutive random numbers to be generated and therefore repeatable simulation conditions.
  • Run the simulation for 20 seconds and view the results. In PostPDS, change the display type to Engineering to better visualize the waves.

32.4. Using the wave seed property

Note

  • Changing the wave seed value will provide a new set of randomly generated waves.
  • Set $WaveSeed 54321.
  • Rerun the simulation and view the results.

32.5. Adding a spreading function

Note

  • When the wave spreading function is enabled, the waves are spread in headings between $WaveHeadingSpread around the mean wave heading.
  • Enable wave spreading by setting $WaveSpreadingFunction 1 in the environment input file.
  • The $SpreadingFunctionConstant is the exponent used to calculate the spreading. Set $SpreadingFunctionConstant 2.
  • Rerun the simulation and view the results.