New publication assessing the MRF model for UAV CFD simulations

February 18, 2026

2026   ·   Publications

Within the framework of the ENOLA project, a new scientific article has been published in the journal Aerospace entitled:

“Assessing the Fidelity of Steady-State MRF Modeling for UAV Propeller Performance in Non-Axial Inflow”

The study examines the validity of the Moving Reference Frame (MRF) CFD model for simulating UAV propellers under non-axial inflow conditions—specifically, in forward-flight regimes where aerodynamic loads become highly asymmetrical.

Objective of the Research

A primary challenge in UAV design is balancing accuracy with computational cost. While MRF models are widely used due to their efficiency, their validity limits in non-axial flight have not been clearly defined.

This research:

  • Systematically compares steady-state RANS-MRF simulations against transient URANS simulations.

  • Develops a quantitative error map across the rotor’s operational range. As shown in Figure 1, this map delineates the specific thresholds where the steady-state approximation remains robust (errors <10%) and where it begins to diverge from physical reality.

Figure 1. Validity map of the steady-state approximation. Contour plots showing the relative difference between RANS and time-averaged URANS prediction for thrust (left) and power (right).
  • Identifies the applicability limits of the MRF model, particularly in high-speed edgewise flight where aerodynamic asymmetry becomes extreme. Figure 2 illustrates this phenomenon through polar maps, highlighting the expansion of negative thrust regions and the shift in the Center of Pressure (CoP) as the advance ratio increases.
Figure 2. Polar maps of aerodynamic asymmetry.
  • Evaluates the impact of these approximations on cyclic loads and preliminary aeroacoustic predictions.

Contribution to the ENOLA Project

These results establish clear criteria for determining when low-cost computational models are sufficient and when high-fidelity transient simulations are required. This is particularly relevant for ENOLA, where accurate aerodynamic prediction is essential for improving the estimation and reduction of UAV-generated noise.

Furthermore, the work incorporates an aeroacoustic evaluation based on the Ffowcs Williams–Hawkings analogy. Figure 3 compares the predicted Sound Pressure Level (SPL) spectra, demonstrating that while both methods capture dominant tonal peaks at low advance ratios, the MRF approach can introduce specific artifacts due to interface pressure non-uniformity.

Figure 3. Comparison of predicted Sound Pressure Level (SPL) spectra between RANS-MRF and URANS.

This advancement helps optimize the numerical tools used in the project, reinforcing the development of more efficient methodologies to mitigate noise pollution associated with UAV propulsion systems.

Read the full article here.