PhD Cifre Thesis - Advanced Physical and Numerical Modeling of icing phenomena in freezing drizzle and freezing rain conditions (H/F)

Job Description:

A PhD position about the “ Advanced Physical and Numerical Modeling of icing phenomena in freezing drizzle and freezing rain conditions (Supercooled Large Droplets)” is proposed in the Engineering Flight Physics Capabilities Team within Airbus Civil Aircraft in Toulouse.

Mission of the team

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The Mission of the Capability Operations domain (1GZ) is to support, develop and deliver

world-class customer-oriented computational simulation means and services in particular for

Aerodynamics, multi-phase flows, convective heat transfer, and icing disciplines, through

technical excellence, continuous innovation and realistic commitments.

The Role

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Icing environments gather various kinds of icing conditions. Among them, Supercooled Large Droplets (SLDs) are of particular interest as they have been recently included in the set of conditions against which aircraft have to be certified.

One of the specificities of supercooled large droplets including freezing drizzle and freezing rain comes from the size of the water droplets contained in these clouds. Indeed, their diameter can exceed 500 microns. As a result, complex phenomena take place when these particles impact aircraft surfaces among which splashing and bouncing. As a consequence, a part of the water contained in the droplets does not deposit on the surfaces and is re-emitted in the airflow.

In order to be able to properly size ice protection systems in SLD conditions, it is mandatory to evaluate the amount of ice which is likely to accrete on aircraft surfaces. As it is directly related to the quantity of water which deposits on the surfaces, an accurate understanding and modeling of the impact phenomena such as splashing and bouncing is mandatory.

Even though significant experimental and modeling research efforts have been carried out at national, european and international level on this topic, none of the state of the art SLD models is adequate nor general and contradictions between some of these models have even been highlighted.

The objective of the PhD, in collaboration with the french aerospace lab ONERA, is to perform a quantitative experimental characterization of the mass of water which deposits on a surface during an SLD impact. Using ONERA experimental capabilities (vertical icing wind tunnel) and scientific expertise, an experimental setup will be designed in order to allow the quantitative measurement of the quantities of interest in conditions representative of aircraft in-flight icing.

Sensitivities to different parameters involved in impact phenomena will be carried out. For example, the droplet diameter will be varied as well as the surface roughness of the test article. In particular, heated surfaces will be studied in order to simulate the activation of an anti-icing system as well as droplet impact on runback ice shapes which form when runback water freezes outside of the heated zones.

These experimental data will feed physical models in order to improve the icing numerical capabilities. The improved models will be implemented in the ONERA icing numerical simulation tools (IGLOO2D and IGLOO3D).

The following steps will have to be addressed:

• Literature review to gather already available experimental data, evaluate and down-select available experimental measurement techniques
  
• Design a dedicated experimental setup with the objective to measure the deposited mass of water during an SLD impact in representative aircraft in-flight icing conditions (altitude, speed,...)
  
• Perform experimental campaigns in the ONERA vertical icing wind tunnel and measure the necessary quantities
  

• Post-process the experimental data and improve SLD models
  
• Implement SLD models in ONERA 2D and 3D icing suites
  
• Validate the SLD models against experimental data available in the literature