Executive Summary
While phenomena involving fine particles are the subject of considerable interest, the methods employed to observe these phenomena do not always receive equal attention. Because measurements in dense solid suspensions are challenging, it is common to ignore the detailed behavior of instruments and, by focusing on the suspension, to misinterpret their signals.
To address this issue, the present report reviews measurement techniques employed in relatively dense flows of gas and solids, with equal emphasis on successes and difficulties involved in their use. In particular, methods to record the following parameters are discussed: pressure, solid volume fraction (capacitance and optical probes, densitometry, tomography), solid flux, particle velocity (cross-correlation, laser-doppler-anemometry), convective and radiative heat fluxes, and diffusion and mixing (sampling probes and tracers).