Hi everyone,
I would like to inspect the flow field around the blade of an oil pump. in the literature, high speed imaging is a well established technique for this kind of studies.
however, how does it work when working fluid is neither air nor water but an oil that appears black\brown?
see scheme attached.
thanks a lot for your cooperation
Giuseppe
To see through an oil with color, your best bets are:
1) Minimize the depth of oil you have to image through (i.e., minimize the clearance between the blade and the window).
2) Find what color of light passes through the oil with the least attenuation. Use that color of light!
3) If possible, put the lights (e.g., LEDs) inside housing. If you can't, try to mount the lights (preferably high-intensity LEDs) directly on the window to avoid glare.
4) Try to image at low frame rate with the blade static and in front of the window. If you can see the blade, start increasing the frame rate (with the blade still not moving) and see if you can image the static blade at the frame rate you desire. If so, you can get the imagery you seek. If not, then something needs to change (mostly likely, in this case, you will want more light or a less opaque oil).
Good luck!
Jim Bales
dear Dr Bales,
first of all thank you very much for your helpful advices!
however, I still have some questions. I'll formulate them according to the numbers in your answer.
1) I'll try it
2)how should I do that? as you may guess, for these kind of fluids it's quite difficult to find optical properties... should I move to trial and error?
3) I might do it but I have some concerns. if I put LEDs flush mounted on the pump housing, is it feasible to still see something considering that light would propagate in a dense and somehow dark medium? should I put lots of them to increase the light density?
4) I'll try it as well and keep you updated
thanks again
Giuseppe
1) Good luck!
2) Trial and error is a reasonable approach
3) The reason to flush mount the LEDs onto the window is to avoid glare. I am assuming that the light must enter through the same window the camera must look through. In that case, if the lamps are any distance behind the window, some of their light will be reflected from the window into the camera lens, causing glare.
If the oil is too dense and dark to allow the light to propagate, you won't see anything.
It won't hurt to try shining the light onto the window with the lights not flush against the glass. And, maybe you won't have a problem with light reflecting off of the window (i.e., glare). But, I suspect you will (and I'd be delighted to be proved wrong!)
Best
Jim Bales
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