Dynamic analysis of a Rayleigh scattering setup using synthetic light signals from a modulated LED

Rayleigh scattering of a laser beam can be used for time-resolved local measurements of density in flows. A key-point of the approach lies in extracting flow density statistics from the measurement of the scattered-light power. Complex hardware equipment and software procedures are involved in this process. The present paper offers a method to assess the entire chain of acquisition of a typical setup in realistic conditions, and an analysis of its dynamic performances with respect to the theoretical expectations. This is achieved by simulating the light intensity fluctuations typically observed with a Rayleigh scattering setup, by use of a known light intensity fluctuation signal generated using a light-emitting diode modulated in output power. The tested Rayleigh scattering setup is shown to perfectly satisfy the theoretical predictions, meaning that it allows us to measure the spectrum of light intensity variations with an outstanding linearity within a dynamic range proportional to the square-root of the measurement time.