PhD Defense by Feyyaz Guner

Event Details
  • Date/Time:
    • Friday March 19, 2021 - Saturday March 20, 2021
      1:00 pm - 2:59 pm
  • Location: Atlanta, GA
  • Phone:
  • URL: Bluejeans
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Summary Sentence: Development and Analysis of Finite State Multi-Rotor Dynamic Inflow Models

Full Summary: No summary paragraph submitted.

Feyyaz Guner
(Advisor: Prof. J. V. R. Prasad)

will defend a doctoral thesis entitled,

Development and Analysis of Finite State Multi-Rotor Dynamic Inflow Models


Friday, March 19 at 1:00 p.m.

Inflow modeling is necessary for accurate performance predictions, aeromechanics analyses, control law development, handling qualities analyses, and flight simulations of single and multi-rotor configurations. Although there are complete inflow theories such as Pitt-Peters and finite state dynamic wake theory (Peters-He) for single rotor configurations, inflow models of multi-rotor configurations still depend on either empirical corrections or data obtained from higher-order wake models to account for the mutual interference effects among the rotors. In this thesis, an analytical finite state multi-rotor dynamic inflow model known as Velocity Potential Superposition Inflow Model (VPSIM) is formulated from first principles. VPSIM superimposes the velocity potentials of each rotor to account for aerodynamic interactions among the rotors. Along with the recently developed Pressure Potential Superposition Inflow Model (PPSIM), inflow predictions of the VPSIM and PPSIM are compared against a high-fidelity numerical model known as Viscous Vortex Particle Method (VVPM) for various multi-rotor configurations. Inflow predictions show that VPSIM and PPSIM can capture fundamental interference effects with some differences. These differences are attributed to real flow effects such as wake contraction, diffusion, and distortion, which are not included in the analytical rigid wake models, i.e., VPSIM and PPSIM.

To improve correlation with the VVPM, VPSIM and PPSIM must be augmented to include real flow effects. A new system identification methodology is developed to improve VPSIM predictions using the changes in the steady-state inflow components. The developed methodology effectively improves the correlation between VPSIM and VVPM for all flight conditions. Besides, unsteady inflow predictions of the VPSIM are generally improved with the inclusion of real flow effects, especially for the swirl velocity coupling.

Lastly, two quasi-steady approximations are proposed to remove the backward time marching solution of the co-states. With approximate methods, interference inflow predictions become much more efficient and straightforward to acquire. These approximate methods have good agreement with the backward time marching solution at the low-frequency range but start to deviate at higher frequencies. In addition to the quasi-steady approximations, co-state equation is represented by a convolution integral to remove backward time marching. The convolution integral is much faster to perform than the backward time marching solution; however, it is only applicable to the linear case.

Finite state multi-rotor dynamic inflow models, VPSIM and PPSIM, capture fundamental rotor-on-rotor inflow interference effects for different configurations. Based on the model fidelity requirement, both models can be enhanced using either a higher order wake model or experimental data. These models can be used in vehicle sizing and performance predictions, aeromechanics analyses, control law development, flight simulations, and handling quality analyses of multi-rotor configurations.



  • Prof. J. V. R. Prasad – School of Aerospace Engineering (advisor)
  • Prof. Lakshmi N. Sankar – School of Aerospace Engineering
  • Prof. Daniel P. Schrage – School of Aerospace Engineering
  • Prof. David A. Peters – Mechanical Engineering and Material Science, Washington University in St. Louis
  • Dr. Chengjian He – Vice President of Research and Development, Advanced Rotorcraft Technology

Additional Information

In Campus Calendar

Graduate Studies

Invited Audience
Faculty/Staff, Public, Graduate students, Undergraduate students
Phd Defense
  • Created By: Tatianna Richardson
  • Workflow Status: Published
  • Created On: Feb 26, 2021 - 10:01am
  • Last Updated: Feb 26, 2021 - 10:01am