Dimensioning of an hydraulic system

for water bombing from an aircraft




Experimentation at IMFT

We realised our experiment at IMFT (The Institute of Fluid Mechanics in Toulouse), helped by to Gregory Ehses who set up the tank.


The parameters are :

  • $l=0.4  m$  the height, length and width of the tank
  • $a=0.04  m$  and $a=0.07  m$  the diameters of the two doors available for our experiment

We can switch from one door to the other thanks to screws.


The discharge is really quick : about 30 seconds for the small door and 12 seconds for the big one.


We carried out 4 different discharges in the laboratory :

  • Experiment 1 :  $a=0.04  m$,   $h_{initial}=0.23  m$,   fluid=water,   $\mu=10^{-3} Pa.s$
  • Experiment 2 :  $a=0.04  m$,   $h_{initial}=0.23  m$,   fluid=water+glycerol,   $\mu=6  10^{-3} Pa.s$
  • Experiment 3 :  $a=0.07  m$,   $h_{initial}=0.3  m$,   fluid=water$,    \mu=10^{-3} Pa.s$
  • Experiment 4 :  $a=0.07  m$,   $h_{initial}=0.3  m$,   fluid=water+glycerol,   $\mu=6  10^{-3} Pa.s$


Physical analysis

We film our experiences to be able to determine the height of water throughout the discharge and we compare the results with those obtained thanks to our Matlab program.

Here are the results for experiment 1:

We observe that our program gives a flow of water a little smaller than the experiment, hence a longer drop time than the experiments.

We can see that our program gives good results, with slight differences due to the approximations we made.

All the other comparisons between experiment and simulations :

Experiment 2:

Comparison of the height of water

Comparison of the flow of water of water

Experiment 3:

Comparison of the height of water

Comparison of the flow of water of water

Experiment 4:

Comparison of the height of water

Comparison of the flow of water of water



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