Metacomp at the 7th AIAA Propulsion Aerodynamics Workshop 2026

In 2026, Metacomp participated in the 7th AIAA Propulsion Aerodynamics Workshop at the AIAA SciTech Forum and Exposition in Orlando, Florida. The workshop focused on evaluating the accuracy of CFD modeling techniques for the NIFTI-LLF coupled fan–intake configuration operating under crosswind conditions. A defining feature of this setup is the ingestion of a ground vortex. Of particular interest here was the accurate prediction of the flow behavior around the intake lip – especially around the onset of flow separation and the formation of the inlet vortex. The operating conditions included a steady 12.5 knot crosswind and two fan operating points defined by rotational speed and measured mass flow rate. All simulations incorporated a ground plane to replicate the experimental oncoming ground boundary layer environment and enable realistic assessment of vortex ingestion and intake aerodynamics. 

Case ID	V∞ (kts)	Pt∞ (Pa)	Tt∞ (K)	RPM	mdot (kg/s)
2	12.5	102,029	296.35	26,900	7.99
3	12.5	101,862	296.55	13,800	4.07

Table 1: Test conditions for PAW-7 simulations

Simulations were performed with hybrid RANS/LES (DDES) and RANS using several turbulence models, including SA, realizable k-ε, and SST models, on both the coarse (220M) and fine (888M) workshop-provided meshes. The target mass-flow rate for each case was achieved by adjusting the back-pressure boundary condition in an iterative process. For the RANS cases, the fan was modeled using an MRF approach, which introduces rotational acceleration source terms to represent blade motion in a steady-state framework. 

For the hybrid RANS/LES effort, an SA-based DDES simulation was performed for Case 2, employing fully transient rotating blades. Traditional scale-resolving simulations typically require a convective CFL near unity, which becomes computationally expensive when long physical time scales (e.g., multiple full rotor revolutions) must also be resolved. To address this, a large time-step DDES method was used, providing a more affordable alternative while still capturing the essential unsteady flow physics. The time-step was selected to achieve approximately 60 time steps per blade passage. 

Table 2: Fan-face total pressure predictions

Fig. 3: RANS SA-QCR fine grid, intake vortex visualization etc.

Fig. 4: Transient history mass flux and total pressure (Case 2, DDES)