Employment of Light Scattering Information to Lay out Optical Measuring Systems for Measurements of Particle Properties
Summary of Contents
The present paper provides a review of the employment of theoretical information on light scattering to lay out optical measuring systems for measurements of particle properties. Optical particle velocity, particle size and particle concentration measurements are considered and special instrumentation requirements are pointed out. It is shown that the most stringthend requirements exist for the measurements of the particle velocity. For this, laser-Doppler anemometry is employed resulting in high frequency signals yielding special requirements for photodetectors. These are explained in detail, since they define the final signal-to-noise ratio obtainable from measuring systems. It is shown that the employment of different photodetectors for particle velocity and particle size measurements yields an optimum for the lay out of the detection system. For laser-Doppler measurements, the special properties of lasers, e.g. the existence of discrete axial modes, do also need to be considered for high particle velocity measurements. They usually do not effect measurements at low particle velocities.
Using the above information, in conjunction with computations of light scattering intensity and phase permits an entire concept for the lay out of optical systems to be introduced for particle velocity, size and concentration measurements. The major considerations of this lay out concept are summarized and references that contain more details are provided. Various systems that were designed according to this concept are shown and examples of measurements presented. Indications of further improvements are given and suggestions for more detailed measurements are made.
KeywordsWind Tunnel Shot Noise Doppler Frequency High Frequency Response Boundary Layer Profile
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