Particle Image Shadowgraph Research Articles

Terminal velocity and drag coefficient of a smooth steel sphere moving in the water-filled vertical and inclined glass pipe (Newton regime)

This paper aimed to determine new data on terminal velocities and drag coefficients of single spheres moving inside a vertical and inclined glass pipe filled with water using the Particle Image Shadowgraph technique in the range of Reynolds numbers from 1420 to 12,740. The inclination angle α of the pipe varied from 0° to 30° relative to the vertical position. In the experiment, smooth steel spheres with diameters ranging from 3 to 9.5 mm were used, and the pipe had a fixed inner diameter of 40 mm. For verification, the experimental results of the drag coefficients were compared with known data from other authors for a free-settling sphere and a sphere rolling down a pipe wall or plane. Finally, the paper presents a new regression model describing the relationship between the sphere drag coefficient and Reynolds number when the cosine of the pipe inclination angle is varied.

Experimental investigation of the settling velocity of spherical particles in Power-law fluids using particle image shadowgraph technique

In this study, a new experimental technique, particle image shadowgraphy, is used to measure the settling velocities of spherical particles (0.5mm–2.0mm) in Power-law fluids of variable viscosity and density. Different concentrations of CMC-water mixtures (0.14–0.28wt%) are used as test fluids for the experiments. A new empirical equation, which is an improved version of the Shah et al. (2007) model, for predicting the settling velocity of a spherical particle in Power-law fluid is proposed. The new empirical model is found to give an average error of 10% in predicting the settling velocity.

An experimental investigation of settling velocity of natural sands in water using Particle Image Shadowgraph

Considering the extensive industrial usage of sands and the benefits of improving the effectiveness of such applications, a detailed experimental study on settling of quartz sands in water is conducted. In this study, 980 quartz sand particles under four sieve sizes in the range of 0.35mm–1.18mm are used. Particle Image Shadowgraph (PIS), an accurate and efficient technique, is employed to determine the settling velocity of the particles. Using PIS in this novel application, the particle dimensions are characterized in terms of centricity, major/minor axes, and equivalent circular diameter. Using the shadowgraph results, an empirical model for settling velocity is developed based on a dimensionless diameter and Reynolds number. The dimensionless diameter is calculated from the equivalent circular diameter (Dc) for the actual projected area of the particle. Furthermore, a simplistic empirical model based on equivalent circular radius (Rce) is proposed in which the particles are considered to be elliptical. Both models require only two-dimensional size parameters that can be easily measured. In this work, drag coefficient (Cd) versus Reynolds number curve for sand particles in the intermediate regime is also presented. It is observed that Cd attains an approximate value of 0.95 at Rep>160. Also, for particles within a particular sieve diameter range, a large variance (16.35% to 92.35%) in settling velocity is observed. Based on the experimental measurement, a correlation between mean sieve diameter and equivalent circular diameter (Dc) is developed which assists in more accurately predicting settling velocity. The new empirical models when compared with data in the literature predict the settling velocity with an average absolute error of 4.1% and 6.5%, respectively, for sieve sizes of 0.35mm–1.18mm.