Measuring velocity without a laser will be pretty tricky. You can't use a pitot tube because of the solids. If a laser won't do, you can try using a high speed, high resolution camera. If you measure the distance travelled by solid particles between frames and divide by the frame time interval, that will give a good particle velocity. If you want air speed, you may need to correct for the relative velocity of the particle with the fluid created by gravity. It's a centrifugal separator, so that should be a small component.

For visualization, try using coloured smoke if the particles themselves are not good enough to do the job. If you feed it in through a tube, you can briefly highlight the vortices individually. Alternately, use a lower solid load and pick a colourful powder. The vortices should stand out

Mohamed,

Two other methods are applicable: ultrasonic velocimetry and heat-pulse anenometry.

Sensors for these methods are listed below.

http://www.hoskin.ca/catalog/index.php?main_page=index&manufacturers_id=4

hot-wire anenometry

http://www.dakotainstruments.com/hot-wire-thermoanemometer-with-nist?gclid=CjwKEAjw3Nq9BRCw8OD6s4eI5HASJABsfCIamgptcROQwLqe-Ge0Y8Q5_lwyjf2tod6ekWClRZL5jRoCWUrw_wcB

The hot wire anenometers can be made *very* small. I have four on my desk, made by MEMS methods, and they are 4mm x 4mm in size for the active head.

For visualization, I'd be inclined to find a line laser, shine it through an appropriate part of the 'storm' and video the resulting light show - that will at least get particle density per unit volume. This only works for low dust/grain loads in the absence of shadowing.

Thanks Alex & James!

James, I know you said no lasers...but PIV (Particle Image Velocimetry) is really the way to do this. If you add a tracer vapor (like Acetone) you could do PLIF. But PIV seems to be exactly what you need. The extreme fluids group here at LANL has done a lot of work with PIV. Is there a reason a laser cannot be employed? http://www.lanl.gov/projects/shocktube/research/research.html

Kirk, I think I mentioned a line laser (purely to illuminate a sheet of particles and then do 'dumb' spot counting to get the local volumetric density.

Me? Give me coherent radiation and I'm happy.

Always.

My bad James, it was Mohamed (who required no laser) and Alex who said it was tricky...so the question was supposed to be directed to Mohamed, why no laser?