Orifice Diameter and Jet Decay

How the diameter of an orifice sets the speed of an air jet downstream.

Aim

Find out whether a smaller, faster orifice stays stronger downstream. Three diameters were measured at three distances.

Tools

Air jet rig with acrylic plenum and honeycomb
Pressure transducer calibrated against a manometer
Two-axis traverse with LVDT position sensing
Python and MATLAB data reduction

Skills

Experiment design
Instrument calibration
Uncertainty analysis
Dimensional analysis
Jet similarity theory
Technical writing in IEEE format

Outcome

At the same distance the three jets run at nearly the same speed. The small orifice leaves faster but does not stay faster, because exit momentum is about the same across sizes.

Measured centerline speed, then profiles at x/D = 15 scaled onto the Gaussian form. Mean of 3 trials, error bars 1 SD. Open marks are estimated exit speeds.

Why it matters

An orifice sets the exit speed and how far a stream stays useful. Matching jets at about the same Reynolds number shows that exit speed alone does not decide the reach.

Scope

Centerline decay and scaled profiles are reported. Jet spread rate is not.

Acrylic plenum with honeycomb sections on a lab bench, traverse in the foreground

Two-axis lead-screw traverse holding the pressure probe in front of the plenum

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