a specialized, highly curved 3D S-duct designed to simulate and analyze complex aerodynamic flow distortions typical of Unmanned Combat Air Systems (UCAS) and low-observable (stealth) military aircraft
Key Design & Development Objectives
Stealth Integration: Shields the engine face (AIP - Aerodynamic Interface Plane) from direct radar line-of-sight to minimize the aircraft's Radar Cross Section (RCS).
Flow Distortion Generation: Deliberately induces strong secondary flows, boundary layer separations, and total pressure distortions to test engine stability limits.
CFD Validation: Serves as an experimental benchmark to validate Computational Fluid Dynamics (CFD) codes and Reynolds-Averaged Navier-Stokes (RANS) turbulence models (such as k-ω SST).
Flow Control Optimization: Provides a testbed for active and passive flow control methods to eliminate or suppress compressor-face separation.
Aerodynamic & Geometrical Architecture
Duct Geometry: Features a non-axisymmetric cross-section transition (often starting with a kidney-shaped or offset intake and smoothly transitioning to a circular interface).
Centerline Curvature: Employs a strong S-bend configuration defined by specific length-to-offset (L/R or L/D) ratios.
Diffusion and Area Ratios: Functions as a subsonic diffuser to reduce incoming flow velocity to sub-Mach levels suitable for the engine compressor while managing adverse pressure gradients.
Distortion Metrics: Evaluated using total pressure recovery coefficients and circumferential/radial distortion descriptors like DC₆₀.
Methodology & Testing Framework
Parametric & Iterative CFD: Evaluating dozens of geometric variants (e.g., assessing multiple S-duct shapes using RANS solvers) to freeze the baseline contour.
Structural & FEM Analysis: Conducting static and dynamic structural finite element method (FEM) analyses to ensure mechanical integrity under aerodynamic loads.
Experimental Testing: Coupling the research duct with ground test facilities (such as modified turbofan engines like the Larzac 04 or dedicated jet engine test cells).
Instrumentation: Equipping the duct with high-frequency dynamic pressure transducers, steady-state static pressure taps, and boundary layer rakes at the AIP.