Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...

Hydrodynamic and heat transfer study of dispersed fluids with submicron metallic oxide particles

Matter is commonly found in the form of materials. Analytical mechanics turned its back upon this fact, creating the centrally useful but abstract concepts of the mass point and the rigid body, in which matter manifests itself only through its inertia, independent of its constitution; “modern” physics likewise turns its back, since it concerns solely the small particles of matter, declining to face the problem of how a specimen made up of such particles will behave in the typical circumstances in which we meet it. Materials, however, continue to furnish the masses of matter we see and use from day to day: air, water, earth, flesh, wood, stone, steel, concrete, glass, rubber, ... All are deformable. A theory aiming to describe their mechanical behavior must take heed of their deformability and represent the definite principles it obeys.

The non-linear field theories of mechanics

The effect of Brownian motion of particles in a statistically homogeneous suspension is to tend to make uniform the joint probability density functions for the relative positions of particles, in opposition to the tendency of a deforming motion of the suspension to make some particle configurations more common. This smoothing process of Brownian motion can be represented by the action of coupled or interactive steady ‘thermodynamic’ forces on the particles, which have two effects relevant to the bulk stress in the suspension. Firstly, the system of thermodynamic forces on particles makes a direct contribution to the bulk stress; and, secondly, thermodynamic forces change the statistical properties of the relative positions of particles and so affect the bulk stress indirectly. These two effects are analysed for a suspension of rigid spherical particles. In the case of a dilute suspension both the direct and indirect contributions to the bulk stress due to Brownian motion are of order o2, where o([Lt ] 1) is the volume fraction of the particles, and an explicit expression for this leading approximation is constructed in terms of hydrodynamic interactions between pairs of particles. The differential equation representing the effects of the bulk deforming motion and the Brownian motion on the probability density of the separation vector of particle pairs in a dilute suspension is also investigated, and is solved numerically for the case of relatively strong Brownian motion. The suspension has approximately isotropic structure in this case, regardless of the nature of the bulk flow, and the effective viscosity representing the stress system to order ϕ2 is found to be
 \[
 \mu^{*} = \mu(1+2.5\phi + 6.2\phi^2).
 \]
 The value of the coefficient of o2 for steady pure straining motion in the case of weak Brownian motion is known to be 7[sdot ]6, which indicates a small degree of ‘strain thickening’ in the o2-term.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/72B16FA20D2A14415CDED6A4F042809F/S0022112077001062a.pdf/div-class-title-the-effect-of-brownian-motion-on-the-bulk-stress-in-a-suspension-of-spherical-particles-div.pdf

The effect of Brownian motion on the bulk stress in a suspension of spherical particles

Chemical sensors respond to the presence of a specific analyte in a variety of ways. One of the most convenient is a change in optical properties, and in particular a visually perceptible colour change. Here we report the preparation of a material that changes colour in response to a chemical signal by means of a change in diffraction (rather than absorption) properties. Our material is a crystalline colloidal array of polymer spheres (roughly 100 nm diameter) polymerized within a hydrogel that swells and shrinks reversibly in the presence of certain analytes (here metal ions and glucose). The crystalline colloidal array diffracts light at (visible) wavelengths determined by the lattice spacing, which gives rise to an intense colour. The hydrogel contains either a molecular-recognition group that binds the analyte selectively (crown ethers for metal ions), or a molecular-recognition agent that reacts with the analyte selectively. These recognition events cause the gel to swell owing to an increased osmotic pressure, which increases the mean separation between the colloidal spheres and so shifts the Bragg peak of the diffracted light to longer wavelengths. We anticipate that this strategy can be used to prepare 'intelligent' materials responsive to a wide range of analytes, including viruses.

Polymerized colloidal crystal hydrogel films as intelligent chemical sensing materials

The colloidal structure of bitumen: Consequences on the rheology and on the mechanisms of bitumen modification

Rheology of monodisperse latices

Diffraction of light by ordered suspensions

Another method has been developed for obtaining the rate of shear vs shearing stress curves of non‐Newtonian fluids from concentric cylinder viscometer data. The mathematical expression developed is a rapidly converging power series in lns, where s is the cup to bob radius ratio. An estimate of error shows that under favorable conditions only two terms of the series are significant, and that terms past the third will hardly ever be needed.

Direct Determination of the Flow Curves of Non‐Newtonian Fluids. II. Shearing Rate in the Concentric Cylinder Viscometer

Diffraction of light by nonaqueous ordered suspensions

A method is proposed for the direct determination of the rate of shear‐shearing stress curve of a fluid from data obtained in concentric cylinder viscometers. The method involves the use of a viscometer in which the ratio of outer to inner cylinder radii can be varied. It is further shown that to a close approximation two such radius ratios are sufficient to define the flow curve.Data for two non‐Newtonian systems are presented to show that the proposed method is valid.

Irvin M. Krieger

Papers

Rheology of monodisperse latices

Diffraction of light by ordered suspensions

Direct Determination of the Flow Curves of Non‐Newtonian Fluids. II. Shearing Rate in the Concentric Cylinder Viscometer

Diffraction of light by nonaqueous ordered suspensions

Direct Determination of the Flow Curves of Non‐Newtonian Fluids