Law for constant flow rate


Dimensioning of an hydraulic system

for water bombing from an aircraft


Law for constant flow rate


Required flow rate

Our objective is to be able to maintain a constant flow of water out of the plane. We adapt our programm to be able to have a constant flow of water.

In this program, we impose a constant flow. We then calculate the outlet velocity corresponding to that flow and deduce, in the end, the outlet surface. 

We face a problem: in the Bernoulli state, the outlet surface has to increase to be able to maintain the constant flow. When the outlet surface is equal to the total surface of the doors, we can't maintain the flow constant.

To solve this problem, we impose the constant flow only while the outlet surface is smaller than the surface of the doors. During this phase, we impose the flow and calculate the corresponding outlet surface, and then the corresponding opening law of the doors. When the outlet surface has reached the total surface of the doors, we calculate the flow of water according to the total surface of the doors.

We manage to maintain a constant flow of $0.5 m^3  /s$ during 14seconds:

And we obtain the corresponding opening law:

Thanks to our program, we know how to open the doors to maintain a water flow.

Here are the results:

Outlet velocity

Inlet velocity

Water flow

Opening angle

Outlet surface

Height of water

Volume dropped


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