Velocity Estimate from Schlieren Flow Visualization

AI Thread Summary
The discussion focuses on using schlieren flow visualization to estimate air velocity from a hair dryer setup. The user replicated a blog's method using a convex lens, LED light source, and smartphone camera. Suggestions for estimating airflow velocity include suspending lightweight particles and using frame-to-frame comparisons to analyze moving features. While schlieren visualization primarily measures variations in the index of refraction, it can provide velocity information with careful technical considerations. However, particle image velocimetry is noted as a more reliable method for measuring flow velocities.
jagadeeshr
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Hi,

I recently came across a blog on schlieren visualization (http://ottobelden.blogspot.in/2010/07/homemade-schlieren-photography-setup.html).

I replicated it with the following: Convex lens (130 mm dia and 350 mm focal length), LED light source (5 mm white LED) and smartphone camera (Moto G4 Plus).

Below is the flow visualization of a hair dryer:



Can anyone suggest how to estimate the velocity of the air flow?

Thank you
Jagadeesh R
 
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jagadeeshr said:
Can anyone suggest how to estimate the velocity of the air flow?
With suspended particles and hi-speed camera?
 
A.T. said:
With suspended particles and hi-speed camera?
Hi,

Thanks for the reply.

I'll try to suspend aluminium foil or other light weight objects in front of the dryer. For calculations, should I be familiar with any equations?
 
jagadeeshr said:
Hi,

I recently came across a blog on schlieren visualization (http://ottobelden.blogspot.in/2010/07/homemade-schlieren-photography-setup.html).

That's clever! Schlieren isn't really set up to measure velocities, it's more to measure variations in the index of refraction (often be due to temperature and/or pressure variations). To get velocity information, you could simply do a frame-to-frame comparison of the moving features and generate a velocity field from that- but there are a lot of technical issues I've skipped that you must address before claiming that you are actually measuring a velocity.
 
Schlieren velocimetry does exist, but usually for turbulent flows so that you can track the movement of small flow structures. Even then it's not very commonly used because particle image velocimetry is much more reliable.
 

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