[zineb elkhaldi]

I would like to ask about Transient Simulation for vertical Autorotation, how can simulate this case in ANSYS-CFX?

[ghorrocks]

Please start a new thread for a new question. I have moved this question to a new thread.

I assume you are talking about autorotation on helicopters or gyrocopters.

If so, it is likely the best approach will be to model the blades at a range of rotation speeds and air velocities covering the range you are likely to see in autorotation. These can probably be modelled as simple steady state/frozen rotor simulations.

This will give you the performance curve for the blades over a range of speeds and air velocities. You then do a simple ODE model of the blades in something like matlab or python to get the transient response of the blades.

[zineb elkhaldi]

yes Sir I am talking about autorotation of helicopters. I need to know how I can simulate a vertical autorotation case in CFX

[ghorrocks]

I explained how to do it in my previous post.

[zineb elkhaldi]

do you mean Sir that i can simulate it without need a 6 dof or moving mesh?

[ghorrocks]

It depends on what you are trying to achieve with the model. But the simple approach I described will allow you to model changes in airspeed and rotor speed without having to use 6DOF or moving mesh. But if you want very precise models you will need to use 6DOF - but be aware that the simulation will be MUCH harder to set up accurately and will be a very long simulation to perform. The simple one I described only uses basic simulation capability and each operating point simulation should be reasonably short and easy - so if it is close enough then it is recommended.

[zineb elkhaldi]

Ok Sir. I try to do it, but I have another question:
Can I change the RPM rotor speed in the same time with changing the airspeed?