Multiphase pipe flows are represented by gas–solid pneumatic transport and solid–liquid slurry transport in pipes, and gas–liquid pipe flows with either gas or liquid as the continuous phase. Fully developed multiphase pipe flows can be characterized by several transport regimes with distinctively different flow patterns and phase interactions dominated by factors such as mass flow ratio of phases, density ratio of phases, pipe orientation relative to gravity direction, transport velocity of continuum phase, and sizes of pipe and particles. Basic topics include the regime classification and flow characteristics in each regime for gas–solid pneumatic transport, solid–liquid slurry transport, and gas–liquid pipe flows, critical transport conditions such as saltation and pickup velocities, mechanisms dominating the pressure drop, suspended flow characteristics in straight pipes and effects of particle loading, electrostatic charges and pipe orientation, characteristics of flow over a bend, such as roping phenomena and bend erosion, and stratified multiphase pipe flow with wavy interfaces.

Chapter 8 introduces the principles of experimental methods to determine various transport properties in multiphase flows. Typical properties include geometric characteristics of dispersed phase, phase volume fractions, mass fluxes or flow rates, velocities, and electrostatic charges. Specifically, the particle size and morphology are measured via the optical image, sieving, sedimentation, cascade impaction, and laser-scattering method. The volume fraction can be determined by the beam-attenuation, permittivity, and tomography principles. The mass flow rate can be determined from the isokinetic sampling and ball probe method. Phase velocities can be measured using the cross-correlation, LDV, and PIV methods. The electrostatic charge is typically measured by Faraday cup and induction probe. The introduction is focused on the basic mechanisms and applicability of the measurement techniques. The chapter also discusses the data analysis methods describing the particle size distribution from overlapped size sampling, such as the deconvolution method.It is also important to identify the equivalent diameter of nonspherical particles that a size measurement reveals.