Doctoral research (Fall 2004-present)

Effect of Wall Motion on a Two-dimensional Boundary Layer

Adviser: Prof. R. J. Goldstein

            Professor, Mechanical Engineering Department

            University of Minnesota, Minneapolis

The present study attempts to investigate the aerodynamics and thermal effects of a:

1. streamwise;

2. opposite; and

3. transverse

wall motion imposed on an inherent  two-dimensional turbulent flow.

The primary idea of this study is to obtain a better understanding of the flow physics and related heat transfer in fundamental situations with a motivation to model the relative motion between rotor and stator blades in a gas turbine during the later stages of this project.

The most important parameter is the ratio of the wall-to-freestream velocity.

Outcome:

• Study of similarity profiles of turbulent kinetic energy
• Variation of mass transfer on endwall

Mean velocity measurements downstream of the moving surface gives an estimate of the turning of the flow due to skewing.
Results from these studies would be used to analyze mass transfer results on the endwall of a first stage turbine cascade. 

Techniques being used:

• Flow measurements
  • Hot-wire anemometry - IFA 100
  • Stationary boundary layer probe and rotating 45^o probe
• Heat/mass transfer measurements using naphthalene sublimation technique
• Modeling of flow and heat transfer using Gambit(grid)/Fluent(solver)
• Design of gas-turbine endwall geometry using PROE

More details:

An IFA 100 hot wire anemometry system is used to measure the turbulent boundary layer on the surface of the moving section. The probe holder is traversed in the x-y-z-q using a five axis mechanism as shown in Fig 3. The effect of the moving section on the velocity boundary layer is being investigated.

Mass transfer measurements

A Schaevitz LVDT probe is used in conjunction with a Schaevitz signal conditioner to scan the naphthalene coated sublimation plate. The voltage readings are acquired using a Keithley 7000 multimeter through a IEEE-488 (GPIB) interface. The difference between the voltage readings before and after a run in the wind tunnel is representative of the local mass transfer coefficients on the sublimation plate along the flow. The effect of a moving wall on an incoming two-dimensional flow is being investigated.

Related links

for Masters research click here