Jet Sprays

High speed photography of three types of interactions of a liquid jet with a moving surface.

a) Deposition - green

b) Spatter - pink

c) Lamella Lift-off - red

Tests with water: surface velocity vs jet velocity. Each plot uses a different geometric angle of the jet relative to the surface.

Red = Liftoff

Pink = Spatter

Green = Deposition

Conclusion: Shallower angles enhance the probability of deposition.

Tests with water: surface velocity vs jet velocity. Each plot uses a different nozzle diameter.

Red = Liftoff

Pink = Spatter

Green = Deposition

Conclusion: Jets with smaller diameters are more likely to deposit.

High speed photography showing two angles of a jet impinging on a surface moving 350kph

High speed photography showing two angles of the phenomena of recovery, when lamella lift-off transitions back to deposition.

Many experiments were repeated for identical conditions leading to recovery. The track distance required for recovery to occur is found to follow a poisson distribution.

Hundreds of tests were performed for jet impingement with various values of jet viscosity, geometric impingement angle, jet diameter, jet speeds and surface speeds.

The radius and widths were measured for each test and all the dimensionless results are plotted here.

Photograph of the business end of the apparatus.

This section is where the jet issues from a nozzle, hits a flow interrupter, waits for jet stability then impinges on the polished disk.

To completely automate the setup, the nozzle back pressure behind the jets needed to be automatically controlled. This was achieved by customizing a regular baffle type pressure regulator with a geared motor, pressure transducer, and solenoid valve. A single input multiple out control algorithm allowed the pressure to be repeatably set to within 0.1 PSI.

A photograph showing the two separate camera mounts designed. The side angle made use of a sliding acetate sheet to clear the screen between experiments. Each camera mount allowed for course and fine adjustments of X, Y, and Z coordinates.

The nozzles are precision pinholes from Edmund optics which are typically used as spatial filters. The pinholes required a custom mount and sealants to withstand the back pressures.

Screenshot of the Labview software created to automate the entire experimental setup. A numeric entry of surface speed and jet speed and a single button press are all that is required for a sequence of nine events to occur.

Schematic diagrams of the entire setup, impingement of a jet, step discontinuities, and geometric definitions of lamella width and radius.