The speed of the wind is in the range of 1-9m/s and we are targeting an area of 3 by 3 cm or even smaller, say 1cm by 1cm. I was thinking about using a continuous 532nm laser with a high speed camera for that. People employed pulsed laser up to 5kHz as the light source, but the frame rate when capturing the image is set as 1kHz. I'm thinking if it gonna work if I use a 1kHz frame camera with a continuous laser. The seeding particles I'm thinking are atomized olive oil.
Dear Zhumei,
I assume here that "targeting area" is the full size of the region of flow you intend to study.
A 1kHz frame rate gives you 1000 images per second, one image per every 0.001 s. In 0.001 s your particles will move 9 mm (at you maximum velocity of 9 m/s). So, your particle will move about 30% of your domain (3 x 3 cm) or almost 100% for 1x1 cm. This implies that you will have a very low definition of the velocity field. You need a higher frame rate or aim for a larger targeting area or a lower velocity.
You also need to check the image resolution, shutter configuration and particle size.
Thanks, Joao.
Yes, relying on higher frame rate to capture this flow speed in a small area is not ideal. Seems the only solution is to use a dual cavity laser with micron second pulse separation and a synchronized double frame camera. But the price would be more expensive.
Dear Zhumei,
please also keep in mind that your particles will smear during the exposure time of the camera when applying a continuous laser. You won't have this problem with pulsed lasers, as they only illuminate your ROI for a very small fraction of the actual exposure time of the camera (nanoseconds laser pulse vs. milliseconds camera exposure).
I hope this helps.
Best regards,
Alexander
Actually, this sounds like a perfect application for Particle Shadow Velocimetry. The speed and FOV are just about right and you can use a pulsed LED for illumination (Much cheaper than the laser you're talking about).
You would likely have to use a different particle or you won't get the right Characteristic Response Time/Stokes number will be too large with Olive Oil.
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Fluid Mechanics