New publication proposing a CFD approach for automated trimming of multi-rotor UAVs

A new scientific article has been published in the journal Aerospace Science and Technology:

Numerical analysis of quad-rotor aerodynamic and aeroacoustic performance with automated trimming algorithm

Within the framework of the ENOLA project, this work introduces a computationally affordable numerical framework to assess the aerodynamic and aeroacoustic behavior of multi-rotor UAVs under balanced, physically representative flight conditions.

The proposed method combines:

steady-state CFD,
a Proportional-Integral trimming algorithm, and
actuator rotor modeling.

This allows the rotor system to be evaluated in a broad range of forward-flight and level-flight conditions while keeping computational cost relatively low.

Objectives of the research

Establish a novel CFD workflow to simulate multi-rotor aircraft in balanced, realistic flight states.
Keep the cost per simulation low enough for parametric studies and design exploration.
Evaluate quad-rotor performance in different trimmed conditions, including forward flight and side-slip.
Assess the acoustic footprint of the aircraft and compare it with configurations trimmed using conventional methods.

Figure 1. Functional block diagram of the trim routine and its coupling with the CFD simulation.

The approach is able to reproduce rotor loading and flow conditions consistent with realistic operating states, as shown in the time-averaged angle-of-attack field used in the simulations.

Figure 2. Time-averaged blade-element angle-of-attack distribution in forward flight at 16 m/s.

Figure 3A. Averaged power consumption of the fore and aft rotors as a function of airspeed.

Figure 3B. Comparison of SPL spectra between automatically and manually trimmed forward-flight cases.

Main findings of the research

The trimming algorithm successfully enabled automated simulation of trimmed flight states across different operating conditions.
The aerodynamic and aeroacoustic results are in close agreement with existing experimental and numerical data, while keeping the computational burden lower than more demanding transient approaches.
Airframe geometry and rotor placement have a non-negligible effect on steady-flight performance.
The steady-state simulations can be used as a robust starting point for transient aerodynamic and acoustic analyses.
Compared with manual trim estimation, the trimmed transient setup provides a better balance in forward flight and a more consistent acoustic prediction.

Contribution to the ENOLA project

This work provides ENOLA with a validated, low-cost numerical tool to assess multi-rotor aerodynamic and aeroacoustic performance under realistic trimmed conditions. By automating the trim process, it improves the project’s ability to study physically representative flight states and to support the design of efficient, quieter UAV configurations.