Oh, I don't know what type of nozzles they are... but obviously not yours
The image was photoshopped simply to show how recessing the nozzle tip
would allow the cone to expand a little more before it was "folded over" by
airflow within the tube. I assume that even your nozzles have the water
leaving the pinhole as a solid stream which very quickly expands and breaks
up into small droplets.
My interpretation of this information is that the water leaving an exposed
nozzle would be more likely to be folded back against the wall of the tube
than the same nozzle recessed a few mm below the tube surface. However,
I'm sure that you have more than likely tested this theory in the lab. And
if experimentation shows that there is no benefit from recessing the nozzle
tip, then I'll just use the standard adapter and try and get the end of the
nozzle flush with the inner surface of the tube.
Cheers... jondee86