Seeding particles are essential to all LDA and PIV measurements and in most applications liquid or solid particles must be added to obtain high quality measurements.
Selecting the right type of seeding
Selecting a seeding generator is the compromise between signal amplitude and the particles ability to follow the flow. Larger particles will increase signal quality, data rate or reduce demand for illumination, but will have a slip in accelerating flows, e.g. a high frequency turbulence.
Smaller particles will reduce signal amplitude and data rate or increase demand for illumination, but will follow the flow to higher frequencies.
- 3 µm oil droplets in air will follow flow fluctuations up to 1 kHz.
- 1 µm oil droplets in air will follow flow fluctuations up to 10 kHz.
- 1 µm powder particles in air will follow flow fluctuations up to 1 kHz.
- 0.4 µm powder particles in air will follow flow fluctuations up to 10 kHz.
For supersonic flows particles should not exceed 1 µm.
Detailed descriptions of Dantec Dynamics' seeding generators:
For further considerations on the selection of seeding particles, please consult litterature, e.g.
Durst et al.: Principles and Practice of Laser Doppler Anemometry.
Albrecht et al.: Laser Doppler and Phase Doppler Measurement Techniques. Springer Verlag, ISBN 3-540-67838-7.Kembali