Spring 2012

 Laboratory #5: Unsteady Velocity Measurements in a Jet Using a Laser Doppler Velocimeter

A formal report  is required for this laboratory. Please follow the instructions for formal report formats carefully, and include the items listing in the Additional Instructions.


Additional Instructions AND Information
While taking your basic data (step 21 in the procedure), you are encouraged to take repeated measurements at a few selected locations if you would like to get more information to help determine the uncertainty of your measurements.

After you are done acquiring axial velocity data, rotate the transceiver by 90 degrees and attempt to acquire vertical velocity component data (at least) somewhere in the shear layer of the jet. Note, you will need to adjust the Bandpass Filter and Downmix settings to account for the fact that: 1) the vertical velocities are less than the axial velocities and 2) the vertical velocity can be both upward and downward.

In preparing your "Error Analysis" section, you may assume that the beam spacing accuracy is +/- 0.25 mm and the lens focal length accuracy is +/- 1 mm. ALSO REMEMBER to include error bars where appropriate in your data plots.


Questions
Please include answers to the following questions in the  appropriate section in your report:

  1. Compare your measured mean and rms vertical velocity components.  How do you think they would change if the wind tunnel velocity was increased without changing the incoming jet velocity.
  2. Provide an explanation of the effects on the measured velocities (mean and rms) that occurred when you changed the relative seeding levels between the windtunnel and jet flows.