Student Name: Michelle Ku

Advisor: Dr. Lakshmi Sankar

Milestone: PhD Thesis Final Examination (Defense)

Degree Program: Aerospace Engineering

Title: Roughness Tolerant Airfoil Design for Rotor and Propeller Applications

Abstract: An inverse design methodology for airfoil was used to design roughness tolerant airfoil for subsonic applications in propeller and helicopter rotor. Methodologies for designing airfoils were first validated with known airfoils such as the NACA airfoils, and were subsequently used for designing a family of airfoils with various thickness to chord ratios from 10% to 22% for UAV propeller and helicopter main rotor improvement applications. While designing the roughness tolerant airfoils, pressure distribution shape on the airfoils was chosen so that the adverse pressure gradient was delayed as far back on the airfoil on the upper surface as possible to delay boundary layer transition and reduce boundary layer thickness. Drag polars of smooth and rough airfoils between designed and baseline airfoils were compared and shown better drag buckets for a range of useable lift coefficients prior to propeller and rotor applications. Icing simulation was also completed to demonstrate lower ice accumulation (a natural roughness phenomenon) for the newly designed airfoils. In-house blade element-momentum and CFD tools were used to analyze propeller and helicopter rotor performance in 3D applications. The current inverse design methodology was able to successfully demonstrate a few possible applications where the airfoils are more roughness tolerant than nominal airfoils. Applications that used designed airfoils showed slightly better performance at higher thrust and lift conditions compared to nominal propeller or helicopter rotor applications. An undesirable higher nose down pitching moment was introduced with the new airfoil design due to aft shifting of loads to delay transition and reduce drag. It was observed that the new airfoils are tolerant to lower surface roughness only. Upper surface roughness tolerance still requires more investigation.

Date and time: 2026-11-30, 10am-12pm

Location: MK317

Committee:
Dr. Lakshmi Sankar (advisor), School of Aerospace Engineering
Dr. Brian German, School of Aerospace Engineering
Dr. Suhas Jain, School of Mechanical Engineering
Dr. Graeme Kennedy, School of Aerospace Engineering
Dr. Juergen Rauleder, School of Aerospace Engineering