Velocity Estimate from Schlieren Flow Visualization

In summary, the conversation discusses using schlieren visualization for flow visualization and estimating air flow velocity with suspended particles and a hi-speed camera. The speaker suggests using frame-to-frame comparison to generate a velocity field, but notes that there are technical issues to consider. They also mention that schlieren velocimetry exists but is not commonly used for velocity measurement compared to other methods.
  • #1
jagadeeshr
11
0
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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  • #2
jagadeeshr said:
Can anyone suggest how to estimate the velocity of the air flow?
With suspended particles and hi-speed camera?
 
  • #3
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?
 
  • #4
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.
 
  • #5
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.
 

1. What is schlieren flow visualization?

Schlieren flow visualization is a technique used to visualize and measure the flow of gases or liquids. It involves using a specialized optical system to detect changes in the refractive index of the fluid, which can then be used to create images or videos of the flow patterns.

2. How is velocity estimated from schlieren flow visualization?

Velocity can be estimated from schlieren flow visualization by using the observed changes in the refractive index to calculate the density gradients in the fluid. These density gradients can then be converted into velocity values using mathematical models or equations.

3. What are the advantages of using schlieren flow visualization for velocity estimation?

Schlieren flow visualization offers several advantages for velocity estimation, including non-intrusive measurement, high spatial resolution, and the ability to capture flow patterns in real-time. It also allows for the visualization of flows that are usually invisible to the naked eye, such as supersonic or hypersonic flows.

4. Are there any limitations to using schlieren flow visualization for velocity estimation?

Yes, there are some limitations to using schlieren flow visualization for velocity estimation. For example, it may not be suitable for measuring flows with high turbulence or complex three-dimensional flows. Additionally, accurate calibration and alignment of the optical system are crucial for obtaining accurate velocity estimates.

5. How is schlieren flow visualization used in scientific research?

Schlieren flow visualization is widely used in scientific research for studying various fluid dynamics phenomena, such as shock waves, boundary layers, and vortices. It is also commonly used in aerospace engineering, meteorology, and other fields where understanding and measuring fluid flow is essential.

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