Velocity Of Non-spherical Particles Research Articles

Free falling of nonspherical particles in Newtonian fluids, B: Acceleration

The acceleration length of nonspherical particles is required for various aspects of system design. However, no simple or usable equations can be found in literature. Therefore, this study is designed to show that the force balance developed earlier for spherical particles, including the new exponential function for the history force, is also valid for nonspherical particles. To achieve this, a new history force parameter definition considering sphericity has been developed based on numerous experiments. The experimental results confirm the definitions of particle acceleration and velocity of nonspherical particles. The acceleration length can be described as a function of the Archimedes number, density ratio, and particle diameter by analogy to spherical particles, considering the terminal Reynolds number, drag coefficient, and history force parameter as functions of the sphericity. In most cases, the acceleration length describes the experiments well, but it is less accurate for cases of orientation change during acceleration.

A Flow Model for the Settling Velocities of Non Spherical Particles in Creeping Motion. Part III. Slender Bodies, the Stream Functions, the Flow and the Momentum Equation

This paper follows previous work regarding the settling velocity of non spherical particles in creeping motion. In this paper, we summarize the flow model, present solutions for the slender plate and the cylinder (Stoke’s paradox), demonstrate the application for euhedral pseudo hexagonal plates (KGa-1) and show the match to the experimental data. In addition, we derive the stream function for the sphere, the slender cylinder and the plate, develop the relationships to compute the flow about a settling particle, back calculate the momentum equation and examine the result

A Flow Model for the Settling Velocities of non Spherical Particles in Creeping Motion, Part II

This paper undertakes a critical examination of Stokes’ law in its final form. The examination and insights of the viscosity principle substantiate grounds to suspect that the controlling dynamics are viscous shear rates across a geometry set by solid boundaries only. The examination sets grounds to conduct an analysis of the dynamics based on the viscosity principle alone and a flow model is derived. Based on the relationship between the pressure gradient and the shear forces as mandated by the viscosity principle the analysis suggests that the pressure gradient surrounding settling particles can be computed, is a single value and expands as required to mobilize a force equal to the driving force. In this context, the pressure gradient arises as a consequence of the contest between body forces in the fluid and the shear forces promoted by shear rates. The flow model suggests that Stokes’ law may be missing important information. An analysis is conducted for the settling velocity of non spherical particles based on the same dynamics and a mathematical solution is reached. The solution is in good agreement with published measured values and defines the influence of particle shape in settling phenomena.

Stereoimaging Measurement of Size and Velocity of Nonspherical Particles.

A stereoimaging technique was applied to the measurement of size and velocity of nonspherical fine particles. This technique was previously developed by us and verified by the measurement of transparent glass beads falling in a pipe. In the present study, several transparent/opaque and spherical/nonspherical particles, each approximately 100 μm in mean diameter, were measured to demonstrate the applicability of this technique to a wide range of particle shapes and particle materials. The measured size distributions were in reasonable agreement with those measured separately by a microscopy. The three-dimensional velocity measurement was also shown to give reasonably good results. Furthermore, the measured characteristics of the particle shape such as the maximum length, the width and the aspect ratio were compared with those obtained by the microscopy. Some statistical features of the attitude of falling particles were also discussed.

Simultaneous Measurements of Velocity and Equivalent Diameter of Nonspherical Particles Using Light Scattering Method.

A new instrument for evaluating the equivalent diameter and velocity of nonspherical particles was developed. The technique is based on the diffraction light intensity method where the light scattered in the forward direction is insensitive to the particle shape but is related to the projected area of the scatterer. A calibration curve between diameter and scattered intensity was determined by a computer simulation using Fraunhofer diffraction theory and the geometrical optics method. Signal processing had been performed with transient recorders and a digital signal processor, working with a personal computer. Various types of irregularly shaped particles, such as cooper, aluminum oxide, glass, polyethylene and stainless steal with diameters ranging from 20 to 200 μm have been examined. The reference diameter of these particles was evaluated by a microscope with an image processing system. Measured size distribution coincided significantly with the reference data, with uncertainty bands of + 10 μm, -0 μm in average diameter.

Discussion of “ Drag Coefficient and Fall Velocity of Nonspherical Particles ” by Prabhata K. Swamee and Chandra Shekhar P. Ojha (May, 1991, Vol. 117, No. 5)

Discussion of “ <i>Drag Coefficient and Fall Velocity of Nonspherical Particles</i> ” by Prabhata K. Swamee and Chandra Shekhar P. Ojha (May, 1991, Vol. 117, No. 5)