Date of Award

Winter 2017

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Joseph C Klewicki

Second Advisor

Christopher M White

Third Advisor

Gregory P Chini

Abstract

An experimental study of the wake of a turbulent boundary layer junction flow was performed using a 3:2 elliptical nose and NACA 0020 tail airfoil in the Flow Physics Facility at the University of New Hampshire. An eight-wire enstrophy hot-wire probe was used to measure all three components of velocity and vorticity at four downstream measurement planes from 1 cord length to 33 cord lengths behind the airfoil. In addition, a simple fairing was added to the airfoil, and the same experiments were repeated. The friction velocity was measured afterward by a Preston tube experiment at the same measurement locations. The incoming flow had a momentum thickness Reynolds number of Re_θ=19600.

It was found that the streamwise velocity statistics in the near measurement planes matched previous junction flow observations. The other velocity statistics supported the conclusions and knowledge in the near planes. The vorticity variance measurements showed little variation from the undisturbed boundary layer leading to the conclusion that large-scale motions are primarily responsible for the non-equilibrium aspects of the flow. The downstream measurements clarified the recovery process towards the undisturbed boundary layer. The final measurement plane showed that aspects of the flow had fully recovered, while others had not. The Reynold stress showed that the turbulent structure of the flow had not recovered but remained persistently different from the undisturbed case. The airfoil with the fairing supported the observations of the airfoil case. Differences were seen between the airfoil and the airfoil with the fairing, but due to the coarse measurement plane, no conclusions were made.

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