Modeling the ship white water wake in the midwave infrared

Area of Science:

• * Ocean optics and remote sensing.
• * Fluid dynamics and turbulence modeling.
• * Infrared radiative transfer in marine environments.

Background:

• * Ship wakes generate white water, a complex mixture of bubbles and spray on the sea surface.
• * Understanding the radiative properties of white water is crucial for remote sensing applications.
• * Previous models often simplify the complex geometry and optical properties of bubble layers.

Purpose of the Study:

• * To develop a physically-based model for the midwave infrared (MWIR) radiance of ship white water wakes.
• * To investigate the influence of bubble geometry and receiver position on wake radiance.
• * To compare model predictions with experimental measurements of ship wake radiance.

Main Methods:

• * Modeled white water as a single layer of bubbles on the sea surface, larger than MWIR wavelengths.
• * Meshed bubble hemispheres into facets, calculating slope probability density functions and accounting for shadowing.
• * Utilized the Sea Surface Radiance Simulator to compute MWIR emitted and reflected radiance under realistic conditions.

Main Results:

• * The range of visible facet slopes in white water wakes significantly exceeds that of the surrounding sea or turbulent wake.
• * This broad range of slopes leads to substantial variability in white water wake radiance.
• * Model predictions show good agreement with measured trends when assuming white water fraction decays quadratically with turbulence intensity.

Conclusions:

• * The geometrical complexity of bubble layers in ship wakes strongly influences their MWIR radiative properties.
• * The proposed model captures the significant radiance variability observed in white water wakes.
• * The findings support the use of turbulence intensity-dependent decay models for white water fraction in wake simulations.