Can SimScale compute the natural angular velocity (RPM) of a wind turbine rotor from aerodynamic forces?

Using SimScale Fluid Flow / CFD
1

Hi SimScale Team,

I am working on an academic CFD project involving an Archimedes Screw Wind Turbine (ASWT).

My objective is to determine the natural rotational speed (angular velocity/RPM) of the rotor generated by the incoming wind.

The workflow I am trying to achieve is:
Wind velocity (Inlet) → Aerodynamic forces on the rotor → Aerodynamic torque–> Angular acceleration → Angular velocity / RPM

In other words, the rotor initially starts from rest (0 RPM), and I would like the solver to calculate how the rotor accelerates and reaches its natural rotational speed due to the aerodynamic torque.

After obtaining this natural RPM, I plan to use the calculated RPM as the input for my final transient CFD simulations to evaluate the turbine performance (Cp, torque, pressure distribution, velocity field, etc.).

I have been reading several SimScale forum discussions and documentation regarding:

  • Rotating Zones
  • Rotating Motion
  • 1 DoF
  • 6 DoF

From my understanding:

  • Rotating Zones require the rotational speed (RPM) to be specified by the user.
  • Rotating Motion also appears to prescribe the motion through a rotation angle, function, or table.

However, my case is different because the RPM is initially unknown.
Therefore, I would like to ask:

  1. Does SimScale currently support fluid-driven free rotation of a rotor?

  2. Can SimScale automatically compute the rotor’s angular velocity (RPM) from the aerodynamic torque generated by the airflow?

  3. If yes, which simulation type or solver should I use?

  4. **If not, what would be the recommended workflow to obtain the natural RPM of a wind turbine rotor using SimScale?
    **
    My simulation setup is:

    • External aerodynamics
    • Single-phase air
    • Incompressible flow
    • Rotor with only one rotational degree of freedom (rotation about its shaft)
    • No prescribed rotational speed

    I am not looking for a prescribed rotating zone where the RPM is already known.

    Instead, I would like the solver to determine the rotor’s rotational speed naturally from the aerodynamic forces.

    Any suggestions, documentation, or recommended workflow would be greatly appreciated.

    Thank you very much!

3

SimScale does not currently support free fluid‑driven rotation where the solver computes the rotor RPM from aerodynamic torque.

In CFD, rotating machinery is simulated using prescribed rotation:

  • MRF rotating zone – steady-state performance sweep at a fixed RPM.
  • Sliding mesh (AMI) – transient simulation with a prescribed rotational speed.

Both approaches require the user to define the rotational velocity. The solver does not solve for RPM from aerodynamic torque.

Recommended workflow for your case:

  1. Run a series of CFD simulations at different RPM values.
  2. Use Result Control → Forces and Moments to extract aerodynamic torque.
  3. Plot torque vs RPM.
  4. The natural operating RPM is where aerodynamic torque ≈ load torque (or zero net torque for a free-running rotor).

This is the standard approach for wind turbines and similar rotors when the operating speed is unknown.

Also note: the Rotating Motion boundary condition exists only in structural analyses (Static, Dynamic, Thermomechanical), not in CFD.

So the practical method is a parametric RPM sweep, not a self-accelerating rotor simulation.

Here are a few SimScale resources that explain the workflow used for turbines and rotating machinery.

1. Wind turbine setup with rotating zones (MRF)

Shows how to prepare the CAD and define a rotating zone with a prescribed RPM.

2. Rotating machinery overview (MRF vs sliding mesh)

Explains the two CFD approaches used for turbines and similar rotors.

3. Parametric studies (useful for RPM sweeps)

Demonstrates how to vary parameters like rotational velocity across multiple simulations.

4. Turbine tutorial example

A step‑by‑step turbine simulation using rotating zones.

These resources cover the standard approach: run multiple simulations at different RPM values and extract torque to build a performance curve.