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Volume fraction
About: Volume fraction is a research topic. Over the lifetime, 16312 publications have been published within this topic receiving 374181 citations.
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TL;DR: In this article, a phenomenological constitutive equation for homogeneous suspensions of macrosized fibres is proposed, where the local averaged orientation of the fibres are represented by a director field, which evolves in time in a manner similar to the rotation of a prolate spheroid.
Abstract: A new phenomenological constitutive equation for homogeneous suspensions of macrosized fibres is proposed. In the model, the local averaged orientation of the fibres is represented by a director field, which evolves in time in a manner similar to the rotation of a prolate spheroid. The stress is linear in the strain rate, but the viscosity is a fourth-order tensor that is directly related to the director field. In the limit of low-volume fractions of fibres, the model reduces properly to the leading terms of the constitutive equation for dilute suspensions of spheroids. The model has three parameters: the aspect ratio R of the fibres, the volume fraction Φ, and A, which plays the role of the maximum-volume fraction of the fibres. Experimental shear data are used to estimate the parameter A, and the resulting model is used in a boundary-element program to study the flow past a sphere placed at the centre line of a cylinder for the whole range of volume fractions from 0.01 to near maximum volume fraction. The agreement with experimental data from Milliken et al. [1] is good.
94 citations
TL;DR: In this paper, a numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles, and the results were presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux.
Abstract: A comprehensive numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles. A paraffin-based nanofluid containing various volume fractions of Cu was applied. The governing equations were solved on a non-uniform mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid-liquid interface. The effects of nanoparticle dispersion in a pure fluid and of some significant parameters, namely nanoparticle volume fraction, cavity size and hot wall temperature, on the fluid flow, heat transfer features and melting time were studied. The results are presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux. The suspended nanoparticles caused an increase in thermal conductivity of nano-enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. In addition, the nanofluid heat transfer rate increased and the melting time decreased as the volume fraction of nanoparticles increased. The higher temperature difference between the melting temperature and the hot wall temperature expedited the melting process of NEPCM.
94 citations
TL;DR: In this article, the effects of nano-particles volume fraction, the type of nanoparticles and permeability parameter on skin friction and convection heat transfer coefficient are studied and discussed.
94 citations
TL;DR: In this article, a camphene-based freeze-casting method was adopted to create ceramics with aligned, equiaxed pores applied so far exclusively for poramics, and the porosity decreased from 82.5 to 65.5 % when the solid loading was increased from 10 to 20 %.
Abstract: A camphene-based freeze-casting method was adopted to create ceramics with aligned, equiaxed pores applied so far exclusively for ceramics—is demonstrated for ZrO 2 porous ceramics. The pore volume fraction, channel size and pore shape were controlled by varying the freezing temperature, solid content and sintering condition. After sublimation of camphene, the samples were sintered for 2 h at elevated temperatures ranging from 1400 to 1550 °C. The initial level of solid loading played a primary role in the resulting porosity of the product. The porosity decreased from 82.5 to 65.5 vol.% when the solid loading was increased from 10 to 20 vol.%. The relationship of the compressive strength versus initial solid loading and sintering temperature was discussed. This technique is considered potentially useful in fabricating novel porous ceramics with special structure, and introduces a new application field of freeze-casting.
94 citations
TL;DR: The flow properties of aqueous suspensions of silica particles with diameters ranging from 117 to 780 nm were measured as a function of volume fraction, ionic strength, and continuous phase composition.
Abstract: The flow properties of aqueous suspensions of silica particles with diameters ranging from 117 to 780 nm were measured as a function of volume fraction, ionic strength, and continuous phase composition. Dense, aqueous suspensions of all sizes displayed similar behavior with a yield stress in the limit of low shear rate, shear thinning as the stress was raised and, above a critical volume fraction, shear thickening. Master flow curves which are weakly dependent on particle size, volume fraction, surface potential, magnitude of the decay length for the electrostatic forces, or particle size distribution are produced when stress is scaled on the suspension’s elastic modulus, G, and shear rate on G/ηc. Here ηc is the continuous phase viscosity. For suspensions which ordered at rest and of sufficiently high volume faction, shear thickening occurred as a discontinuous decrease in shear rate as the stress increased. This behavior was not observed in suspensions altered so that no order occurred at rest. When the...
94 citations