**2. Experimental work**

 The experiments were carried out in a laboratory loop at the Institute of Hydrodynamics in Prague.

### **2.1 Experimental setup and measuring techniques**

 The loop is composed of horizontal and vertical pipe sections, each with an internal diameter of 100 mm ( **Figure 1** ). The geometry of the loop, its measuring equipment, measuring techniques, and experimental procedures for slurry flow tests are described in detail in [ 15 ]. During tests, experimental data are collected from both the pipeline and the pump of the loop. Pipe measurements include the mean velocity of slurry *V* m (defined as the ratio of the total volumetric discharge of slurry divided by the cross-sectional area of the pipe) by a magnetic flowmeter, the differential pressure over several measuring sections of a pipeline measured by a differential pressure transducer (DPT), and the chord-averaged vertical distributions of local volumetric concentration *c* by gamma-ray radiometric profilers mounted to some of the


*Settling Slurry Transport: Effects of Solids Grading and Pipe Inclination DOI: http://dx.doi.org/10.5772/intechopen.108436*

#### **Table 1.**

*Properties of tested sand fractions.*

pressure-drop measuring sections. The delivered concentration *C*vd (defined as the ratio of the solids discharge and the total discharge) is obtained from the differential pressures measured either in the invert U-tube if it is set to the vertical position, or in the vertical pipe section below the flowmeter (**Figure 1**).

For horizontal-flow tests, local velocities of individual particles are measured at the bottom of the transparent pipe section (No. 7 in **Figure 1**) in the horizontal pipe section. The instantaneous velocities are obtained from images collected by a highspeed camera. The particle image velocimetry (PIV) method is used to analyze the motion of coarse particles in one-species-slurry flow and the motion of fine particles in bimodal slurry flow. The particle tracking velocimetry (PTV) method is used to determine the motion of coarse particles in the flow of bimodal slurry. More details on the velocity measuring techniques used are given in [15].

#### **2.2 Solids fractions used in experiments**

Five narrowly graded fractions of sand from fine-to-medium to very coarse (**Table 1**) were used to produce one-species (narrowly graded), bimodal, or multispecies (broadly graded) slurries for laboratory experiments.
