Airplane Washing by Water Jet

Airplane Washing Using Water Jet, CFD Simulation ANSYS Fluent Training

Description

Airplane fuselages accumulate contamination over time due to their high-velocity motion through the air, picking up insect residue and bird droppings that combine with engine exhaust to form a carcinogenic contaminant layer on the fuselage surface. To address this, airplanes undergo washing several times per year, with sensitive components such as windows typically covered beforehand to prevent scratching during the process.

This project simulates the aircraft washing process using ANSYS Fluent. The computational domain consists of a 46×8.5×17 m cube, with a separate sub-domain modeling the aircraft's motion through this space using a sliding mesh approach. Water enters the domain through holes positioned at the bottom of a sloped inlet at 15 m/s, while air enters from the opposite side, moving against the direction of the aircraft's travel at 2 m/s, together representing more realistic washing conditions.

Geometry & Mesh

The computational domain was built in Design Modeler as a 46×8.5×17 m cube, with the moving aircraft sub-domain represented as a smaller cube measuring 13.5×3 m in cross-section. The domain was meshed in ANSYS Meshing using an unstructured grid, totaling approximately 4,560,000 elements.

Methodology

Several assumptions were applied to the simulation: a pressure-based solver was used, the problem was solved as transient, and gravitational effects were included.

Key simulation settings included:

• Material properties: Water (density 998.2 kg/m³), air (density 1.225 kg/m³)

• Multiphase model: VOF (Volume of Fluid), with two Eulerian phases (water and air), sharp interface modeling, explicit formulation, and an air-water surface tension coefficient of 0.072 N/m

• Boundary conditions: Velocity inlets for water (15 m/s) and air (2 m/s); pressure outlet at 0 Pa gauge pressure

• Cell zone conditions: Mixture fluid throughout the domain

• Mesh motion: Moving zone with a translational velocity of 1 m/s, representing the aircraft's motion through the wash sequence

• Turbulence model: Realizable k-epsilon with standard wall functions

• Solution methods: SIMPLE pressure-velocity coupling, PRESTO! for pressure discretization, second-order upwind for momentum, Modified HRIC for volume fraction, and first-order upwind for turbulent kinetic energy and dissipation rate

• Initialization: Hybrid method

Conclusion

Results include volume fraction and velocity contours extracted along a longitudinal section of the computational domain. These results clearly show air injection into the domain increasing progressively over time, with the washing process itself occurring as the aircraft's moving sub-domain reaches the corresponding section of the domain — capturing how the combined water jet and airflow interact with the fuselage surface as it travels through the wash sequence.