The purpose of the paper is to describe a novel technique for simulating propellant flow in spinning motors, in order to find the distribution of particles that may remain inside the motor thus degrading its performance. An experimental installation built for this purpose is described in detail. It is based on modified laser Doppler anemometry, which allows to measure both the three components of the velocity of the carrier gas and the particles and the particles size distribution. The particles are simulated by paraffin droplets of an average 20 millimeters diameter, while small paraffin droplets allow to measure gas velocity. A special droplet generator was designed and built; the test chamber is formed by two cylindrical pyrex tubes with a sudden contraction in diameter, which can be rotated up to 400 rpm. The optical arrangement is described as well as the electronic set-up required for data acquisition. Results validating the concept are presented.