# Dynamic meshing - UDF to determine rpm of turbine

Member

I am modelling a wind turbine blade. I want in FLUENT that I specify inlet velocity at its inlet and the FLUENT let itself rotate the blade due to this wind velocity.  I am stuck in UDF because all the UDFs I had searched up until now have used rpm inside the UDF. Help will be appreciated

• Member
edited October 2018

Hi,

Can you please give more details about your question? I did not see any variable that is the rotational speed in the UDF attached.

• Forum Coordinator
edited October 2018

Hi,

Can you please insert images here and describe your problem in detail.

Regards,

Keyur

• UKForum Coordinator
edited October 2018

You may want to re-think the approach slightly.  Think through the problem: why does a turbine rotate?  From there, what do you need to link in your code to mimic this?

• Member
edited October 2018

Hi,

The wind velocity causes the turbine to rotate. In boundary condition inlet velocity of air was defined. The purpose of writing UDF is to determine the rpm of turbine due to wind. The UDF determines the orientation of turbine in x,y and z direction with respect to each time step. The issue is that motion file generated after processing is showing zero rotation .

• Member
edited October 2018

Hi,

The objective is to determine rpm of wind turbine. The two possible techniques that could be used are sliding mesh method and dynamic meshing. The use of sliding mesh technique in Fluent requires rpm of turbine as input while in this case, I attend to calculate the rpm of turbine due to wind flow. The UDF is defined such that turbine is free to rotate about z - axis and moment of inertia and mass of turbine is defined. The flow of air in x direction is defined as inlet boundary condition. The issue is that code is giving 0 rpm or orientations. The motion file generated after the end of 3 time steps is attached

• Forum Coordinator
edited October 2018

You may need to use 6dof. Please check following video for some informatin.

Regards,

Keyur

• UKForum Coordinator
edited October 2018

It may also be possible to link the blade surface pressure to the rpm: which is why I wanted you to think through the problem.

Work out the force on the blade, and resistance to motion from gearbox etc.  Then set the rotation velocity using the UDF.  Linking to the inlet wind speed is valid, but only works for that turbine: linking to the blade force makes it a more transferable function.

• Member
edited October 2018

Hi,

Since it is a lift based turbine the lift force from the wind will produced torque on the blades. The rpm of turbine was then linked with torque such that,

T= I*a

where,a=angular acceleration.and based on the value of angular acceleration the function of rpm was written. Now i am having issues writing the UDF

• Member
edited October 2018

Hi,

I previously used 6dof technique and the udf code written was similar to tutorial where mass and moment of inertia is defined and the object is free to rotate about certain axis.

• Member
edited July 3

hey Irtaza  i am also doing a same problem in which i want to rotate a turbine with different wind speeds , but i am very confused how to do it , as i can see u already have done same problem i think u can help me in this, the problem is i want wind to rotate the turbine please help me in this i am new to ansys cfd .

thankyou

• Member

hi all

i have the same problem , how can calculate the rpm from dynamic mesh

• UKForum Coordinator

Read through the above, the change now is that Expressions are available to make this easier.