Ph.D. Thesis Defense: Nana Obayashi

Event Details
  • Date/Time:
    • Monday November 14, 2016 - Tuesday November 15, 2016
      9:00 am - 10:59 am
  • Location: Montgomery Knight Building Room 317
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Summaries

Summary Sentence: “Assessment of Icing Characteristics for Single and Coaxial Rotors”

Full Summary: Nana Obayashi will present her defense for doctoral research in the “Assessment of Icing Characteristics for Single and Coaxial Rotors”

Master’s Thesis Defense by

Nana Obayashi

Advisor:  Prof. Lakshmi Sankar

Assessment of Icing Characteristics for Single and Coaxial Rotors

Monday, November 14 @ 9 a.m., Montgomery Knight 317

Abstract:

Icing on blade surfaces adversely affects the aerodynamic performance and safety of helicopters through loss of lift, loss of power, increase in drag, decrease in stall angle and dangerous ice shedding events. Equipping rotor blades against the effects of icing increases the helicopter cost and puts higher demand on the power plant. In the field of CFD, efforts have focused on modeling the effects of icing, including the resulting rotor performance degradation. Single rotor helicopters have been the primary focus of existing models for ice accretion, leaving an opportunity to expand modeling efforts to other types of helicopters, such as coaxial rotors. Although the coaxial rotor has a number of advantages attributed to its symmetric aerodynamic environment in any flight direction, additional work is needed using physics-based models, in order to analyze the complex flow interactions between the upper and lower blades.

An in-house ice accretion model was improved upon prior work by implementing a 3-D Eulerian approach integrated into the CFD flow solver, GT-Hybrid, in order to solve for water droplet collection efficiency on the surface of the rotor blade. This model implements an extended Messinger model with the Stefan condition at the ice/water interface in order to predict ice accretion based on droplet collection and establishment of a thermodynamic balance for phase shift. These improvements have allowed this model to reduce the limitations and empiricism inherent in existing models. The model has been validated based on a limited number of cases with promising predictive power compared to the industry standard ice accretion model by NASA, called LEWICE.

The present work contributes to the efforts behind the in-house ice accretion model in two ways. First, ice shape prediction using the in-house model is validated against existing experimental ice accretion data for a single rotor configuration in three different flight conditions. An analysis of the simulated and experimental results presented shows promising evidence of the model’s predictive power, especially at the inboard blade locations where the ice is predominantly rime. Second, the in-house model is adapted for application to a coaxial rotor configuration. In order to validate the flow solution, performance analysis is completed for a coaxial rotor in hover using GT-Hybrid and Star-CCM+ in the absence of ice accretion. Then, ice accretion is simulated for the same rotor for three collective pitch angles and the ice shapes are presented. Finally, the performance degradation of the coaxial rotor due to ice is estimated.

Committee Members:

Dr. Lakshmi N. Sankar, School of Aerospace Engineering (Advisor)

Dr. Jechiel I. Jagoda, School of Aerospace Engineering

Dr. Daniel P. Schrage, School of Aerospace Engineering

Additional Information

In Campus Calendar
Yes
Groups

School of Aerospace Engineering

Invited Audience
Faculty/Staff, Undergraduate students, Graduate students
Categories
Seminar/Lecture/Colloquium
Keywords
aerospace engineering
Status
  • Created By: Margaret Ojala
  • Workflow Status: Published
  • Created On: Nov 9, 2016 - 3:11pm
  • Last Updated: Apr 13, 2017 - 5:14pm