Hemispherical Turret Beam Directors

 

The Aero-Optics group has done a great deal of work studying the flow around a hemispherical turret and the effects it has on a laser beam. Hemispherical turrets are a popular beam director design due to their high field of regard, as they can move to look in any direction. However, sticking this turret into the flow disturbs the flow considerably, creating complex flow structures which in turn distort the laser beam. The effect is two-sided:

1) Flow structures create density variations which aero-optically distort a beam passing through.

2) Flow structures create pressure variations push on the turret causing it to shake, and as a result move the beam around on the target.  

The Aero-Optics group has done a significant amount of work characterizing these effects. Recent wind tunnel tests looked at how the flowfield changes as the turret is lowered into the wall, reducing its protrusion. Pressure sensitive paint measurements gave surface pressure on the turret and the wall in its wake. 

 

 

Processing the pressure data using optical flow allowed us to calculated a mean convective surface velocity field

 

 

Reviews on aero-optics of turrets

S. Gordeyev, E. Jumper, and M. Whiteley, "Aero-Optical Effects: Physics, Analysis and Mitigation”, 1st edition, John Wiley & Sons, 2023. Available on Amazon and Barnes&Noble.

DeLucca, N.; Gordeyev, S.; and Jumper, E.J., "In-flight aero-optics of turrets,” Journal of Optical Engineering, 52(7), 071405, 2013.

Gordeyev, S. and Jumper, E.J., "Fluid dynamics and aero-optics of turrets," Progress in Aerospace Sciences, 46, pp. 388-400, 2010.