Defining the Fluid Phases and VOF Waves

To define the fluid, you create the air and water phases. To define the waves, you create a fifth-order wave, which is modeled with a fifth-order approximation to the Stokes theory of waves. A fifth-order wave resembles a realistic wave. The wave profile and the wave phase velocity depend on the water depth, wave height, and current.

  1. Right-click the Multiphase > Phases node and select New.
    1. Repeat the previous step to create an additional phase.
    2. Rename Phase 1 to Water and Phase 2 to Air.
    3. Right-click the Water node and click Select Models...
    4. In the Water Model Selection dialog, select the following models:
      Group Box Model
      Material Liquid
      Equation of State Constant Density
    5. Click Close.
    6. For the Air phase. select the following models:
      Group Box Model
      Material Gas
      Equation of State Constant Density
To create a fifth-order wave:
  1. Right-click the Continua > Physics 1 > Models > VOF Waves > Waves node and select New > Fifth Order.
To link the fifth-order wave, you create a Linked VOF Wave 1. You apply Linked VOF Wave 1 associated field functions as boundary conditions. With this approach, when you change the VOF wave specifications later on, you do not need to update the field functions for all the relevant boundaries.
  1. Right-click the VOF Waves > Waves node and select New > Linked
  2. Define the fifther-order VOF wave settings:
    1. Expand the Fifth Order Vof Wave 1 node and set the following properties:
      Node Property Setting
      Fifth Order Vof Wave 1 Point On Water Level [210.0 m, 0.0 m, 0.0 m]

      When the simulation is initialized, this value defines the mean water level in the Z direction. In the wave advancing direction (-X), this values specifies the point, until which the wave is initialized with the wave. From the point, the free surface is initialized with a flat wave.
      Advancing Direction $${AdvancingDirection}

      Pre-defined vector parameter, which specifies the wave propagation direction (-X).
      Wave Height ${WaveAmplitude}*2.0

      The wave height is 20m—2 times of the wave amplitude.
      Water Depth 5000.0 m

      For fifth-order wave, the water depth influences the wave shape. To minimize the effect of the water depth on the wave shape, you set a significantly large value.
      Specification Type Wave Length
      Wave Length Specification Wave Length ${Wavelength}

      The wavelength is 400m.
      Linked Vof Wave 1 Referenced Vof Wave Fifth Order VOF Wave 1

      After solution initialization, the water free surface appears as follows:



The VOF Multiphase model uses the high-resolution interface capturing scheme to give an accurate approximation of the volume fraction at cell faces and improve the resolution of the interface.
  1. Expand the Volume of Fluid (VOF) node and set the following properties:
    Node Property Setting
    HRIC CFL_I 50.0
    CFL_U 100.0
    Angle Factor 0.15
    Adaptive Mesh Interpolation Option Sharp Reconstruction

    This combination of settings ensures that there is a second order HRIC scheme for large Courant Numbers. Setting an Angle Factor of 0.15 is the recommended best practice for simulating ocean waves.

  2. Expand the Physics 1 > Initial Conditions node, and set the following properties:
    Node Property Setting
    Pressure Method Field Function
    Scalar Function Vof Wave > Linked VOF Wave 1 > Hydrostatic Pressure of Heavy Fluid of Linked Vof Wave 1
    Turbulence Intensity Value 1.0E-5
    Turbulent Viscosity Ratio Value 1.0E-4
    Velocity Method Field Function
    Vector Function Vof Wave > Linked VOF Wave 1 > Velocity of Linked Vof Wave 1
    Volume Fraction Method Composite N-1
    Composite N-1 > Water Method Field Function
    Scalar Function Vof Wave > Linked VOF Wave 1 > Volume Fraction of Heavy Fluid of Linked Vof Wave 1
  3. Save the simulation.