Flow field diagnostics by spectrally filtered Rayleigh scattering Conference Paper uri icon


  • We report here preliminary results for a new technique which uses spectrally Filtered Rayleigh Scattering (FRS) to determine flow field parameters including density, temperature, and velocity. In addition, it may be used to suppress background scattering from windows and walls while simultaneously giving two-dimensional images of Rayleigh scattering which show flow field structure. Narrow linewidth laser light scattered from a high-speed gas flow is frequency shifted by an amount which is directly proportional to the velocity of the flow due to the Doppler effect. The spectral width of the scattered light is related to the temperature of the flow due to thermal broadening, and the scattering intensity is proportional to the gas density. A cell containing a gaseous atomic or molecular species is placed in front of a camera which observes the Rayleigh scattered light from the flow. If the illuminating laser is tuned through an absorption line of the gas in the cell, then the recorded intensity versus frequency of each resolvable portion of the flow will be related to its density, velocity, and temperature. By using a broad bandwidth, sharp cutoff spectral feature of the gas in the cell, scattering from the windows and walls can be simultaneously eliminated. If the scattering is predominately from particles in the flow rather than from air molecules, then the velocity can be measured, but temperature and density cannot.

name of conference

  • ICALEO 90: Proceedings of the Optical Methods in Flow & Partial Diagnostics Conference

published proceedings

  • International Congress on Applications of Lasers & Electro-Optics

author list (cited authors)

  • Forkey, J., Lempert, W. R., & Miles, R. B.

publication date

  • January 1, 1990 11:11 AM