Class LNGSloshingModel

java.lang.Object
neqsim.process.equipment.lng.LNGSloshingModel
All Implemented Interfaces:
Serializable
public class LNGSloshingModel extends Object implements Serializable
Models sloshing-induced mixing enhancement in LNG cargo tanks.

Ship motion causes the LNG liquid to slosh within the tank. The resulting turbulence enhances mixing between stratified layers and increases the surface renewal rate (BOG enhancement). Sloshing intensity depends on:

  • Significant wave height (Hs): Primary driver of ship motion amplitude
  • Fill level: Sloshing is most severe at 10-70% fill; minimal near full or empty
  • Tank geometry: Membrane tanks allow more free-surface movement than Moss
  • Ship heading: Beam seas produce more sloshing than head seas

The model produces two outputs:

  • Mixing factor: Enhancement to inter-layer mass transfer (diffusion coefficient multiplier)
  • BOG enhancement factor: Enhancement to surface evaporation rate
Version:
1.0
Author:
NeqSim
See Also:

  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      Serialization version UID.
      See Also:

    • logger

      private static final org.apache.logging.log4j.Logger logger
      Logger object.

    • referenceWaveHeight

      private double referenceWaveHeight
      Reference wave height for normalisation (m). Typical North Sea conditions.

    • sloshingCoefficient

      private double sloshingCoefficient
      Sloshing intensity coefficient. Empirical scaling factor.

    • containmentType

      private TankGeometry.ContainmentType containmentType
      Tank containment type (affects sloshing severity).

    • maxMixingFactor

      private double maxMixingFactor
      Maximum mixing enhancement factor (physical limit).

    • maxBOGEnhancement

      private double maxBOGEnhancement
      Maximum BOG enhancement factor.

  • Constructor Details

    • LNGSloshingModel

      public LNGSloshingModel()
      Default constructor.

    • LNGSloshingModel

      public LNGSloshingModel(TankGeometry.ContainmentType containmentType)
      Constructor with containment type.
      Parameters:
      containmentType - tank containment type

  • Method Details

    • setContainmentDefaults

      private void setContainmentDefaults(TankGeometry.ContainmentType type)
      Set default parameters based on containment type.
      Parameters:
      type - containment type

    • calculateMixingFactor

      public double calculateMixingFactor(double significantWaveHeight, double fillFraction)
      Calculate the mixing enhancement factor due to sloshing.

      The mixing factor enhances inter-layer diffusion and is applied as a multiplier to the effective diffusion coefficient. The factor depends on wave height and fill level: 

      factor = 1 + k * (Hs / Hs_ref) ^ 2 * f(fill)

      where f(fill) peaks at ~30-50% fill and drops to near zero at high fill levels.

      Parameters:
      significantWaveHeight - significant wave height Hs (m)
      fillFraction - tank fill fraction (0.0 to 1.0)
      Returns:
      mixing enhancement factor (1.0 = no enhancement)

    • calculateBOGEnhancement

      public double calculateBOGEnhancement(double significantWaveHeight, double fillFraction)
      Calculate the BOG enhancement factor due to surface renewal from sloshing.

      Sloshing increases the liquid surface renewal rate, which enhances evaporation. The effect is smaller than the mixing enhancement and primarily affects the surface layer.

      Parameters:
      significantWaveHeight - significant wave height Hs (m)
      fillFraction - tank fill fraction (0.0 to 1.0)
      Returns:
      BOG enhancement factor (1.0 = no enhancement)

    • calculateFillLevelEffect

      private double calculateFillLevelEffect(double fillFraction)
      Calculate the fill-level effect on sloshing intensity.

      Sloshing severity depends strongly on fill level:

      • < 10% fill: minimal liquid, low sloshing
      • 10-30% fill: increasing sloshing, free surface grows
      • 30-50% fill: maximum sloshing — resonance with tank natural frequency
      • 50-80% fill: decreasing sloshing, less room for motion
      • > 80% fill: minimal sloshing, liquid nearly static (deck cargo limit typically 98%)
      Parameters:
      fillFraction - fill level (0-1)
      Returns:
      fill-level effect factor (0-1, peaks at ~0.4)

    • getReferenceWaveHeight

      public double getReferenceWaveHeight()
      Get reference wave height.
      Returns:
      reference wave height (m)

    • setReferenceWaveHeight

      public void setReferenceWaveHeight(double referenceWaveHeight)
      Set reference wave height.
      Parameters:
      referenceWaveHeight - reference wave height (m)

    • getSloshingCoefficient

      public double getSloshingCoefficient()
      Get sloshing coefficient.
      Returns:
      sloshing coefficient

    • setSloshingCoefficient

      public void setSloshingCoefficient(double sloshingCoefficient)
      Set sloshing coefficient.
      Parameters:
      sloshingCoefficient - sloshing coefficient

    • getContainmentType

      public TankGeometry.ContainmentType getContainmentType()
      Get containment type.
      Returns:
      containment type

    • setContainmentType

      public void setContainmentType(TankGeometry.ContainmentType containmentType)
      Set containment type (also updates defaults).
      Parameters:
      containmentType - containment type

    • getMaxMixingFactor

      public double getMaxMixingFactor()
      Get max mixing factor.
      Returns:
      max mixing factor

    • setMaxMixingFactor

      public void setMaxMixingFactor(double maxMixingFactor)
      Set max mixing factor.
      Parameters:
      maxMixingFactor - max mixing factor

    • getMaxBOGEnhancement

      public double getMaxBOGEnhancement()
      Get max BOG enhancement factor.
      Returns:
      max BOG enhancement

    • setMaxBOGEnhancement

      public void setMaxBOGEnhancement(double maxBOGEnhancement)
      Set max BOG enhancement factor.
      Parameters:
      maxBOGEnhancement - max BOG enhancement