In this first part, the context of the project and its objectives will be explained to set the study.

Context of the study

Every year, thousands of forest's hectares go up in smoke because of wildfires wether they are criminal acts or not. In the framework of firefighting, airtankers (or water bombers) play a crucial role. The airtanker can release either pure water or water completed with retardant which delays the spreading of the fire by covering the vegetation with a thin fireproof layer. When the weather is not clement (often during summertime), the water bombers can practice air suveillance, with full tanks, as a precaution. 


Illustration : Airtanker (or water bomber) (source :

Airtankers are subject to important mechanical stress :

  • they have to release the water as close as possible to the fire, so they have to fly at low altitude, with turbulences caused by the fire, and often strong wind.
  • the release of water or retardant causes strong mechanical stress on the plane.


That is the second point hereabove which is the base of this study. Indeed, airtankers are subject to flying difficulties and to important stresses. This can explain the frequency of accidents, and especially rupture in flight. That is why limiting this mechanical stress is a real stake. This limitation can be realised by several ways, and one of them is to reduce the sloshing in the tanks of water bombers and this is the object of our study.







The objectives

In this study, we will be particularly interested in the using of the cargo plane CASA 235-295 A400M of Airbus. The global objective of this work is to develop a release system for firefighting. During the previous works on this subject, the former students focused on the numerical modelling of the print of released water on the ground, and on the ejection system. This year, we will particularly focus on the sloshing in the water (or retardant) tank in order to characterise it and then reduce it.

First of all, it was important to carry out a bibliographical work, to study the articles and thesis which can help us, give us directions to progress in the work to be done. After that, we set the study from the theoretical point of view, writing the preliminary calculations governing the problem. Then, we proceeded to the numerical modelling of the situation, thanks to the software FLUENT. This numerical study is divided in several parts : 

    - Creating of the geometry and mesh representing the tank containing water (or retardant)

    - Submiting the mesh to a "reference" situation and then run several simulations, making the following parameters vary : acceleration of the plane, viscosity of the fluid, fill rate of the tank.  Getting the oscillation frequency and the dissipation time function of these parameters.

    - Running more simulation with a new geometry : a compartmentalized the tank (with inserted walls in the tank) in order to reduce sloshing.

   - Simulating a complete flight with all the phases : take off acceleration, gaining of altitude, release of water (or retardant)