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Herschel–Bulkley fluid

About: Herschel–Bulkley fluid is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 49318 citations.


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TL;DR: This investigation provides detailed information with regard to shear-stress distribution at the plate as well as secondary flow and shows that there is a region on the plate where shear stress is almost constant and an analytical approach can be applied with high accuracy.
Abstract: Endothelial cells, covering the inner surface of vessels and the heart, are permanently exposed to fluid flow, which affects the endothelial structure and the function. The response of endothelial cells to fluid shear stress is frequently investigated in cone-plate systems. For this type of device, we performed an analytical and numerical analysis of the steady, laminar, three-dimensional flow of a Newtonian fluid at low Reynolds numbers. Unsteady oscillating and pulsating flow was studied numerically by taking the geometry of a corresponding experimental setup into account. Our investigation provides detailed information with regard to shear-stress distribution at the plate as well as secondary flow. We show that: (i) there is a region on the plate where shear stress is almost constant and an analytical approach can be applied with high accuracy; (ii) detailed information about the flow in a real cone-plate device can only be obtained by numerical simulations; (iii) the pulsating flow is quasi-stationary; and (iv) there is a time lag on the order of 10(-3) s between cone rotation and shear stress generated on the plate.

80 citations

Journal ArticleDOI
TL;DR: The analysis of grease-lubricated rolling element bearings is presented in this article, where a theory for predicting roller film thickness based on the assumed flow model is derived, and the results show that grease will develop a larger film thickness than the base oil at first but the film thickness falls during rolling until it reaches a steady thickness usually lower than that of its base oil.
Abstract: The analysis of grease-lubricated rolling element bearings is presented. Experimentally determined flow curves for grease are found to be well correlated by the Herschel-Bulkley model flow equation. A theory for predicting roller film thickness based on the assumed flow model is derived. Experimental results show that grease will develop a larger film thickness than the grease base oil at first, but the film thickness falls during rolling until it reaches a steady thickness usually lower than that of its base oil. This effect is shown to depend on the degree of shear degradation of the grease, its resulting flow curve, and the temperature rise due to shear in the inlet. The grease yield stress is found to have a negligible effect on EHL performance. Presented at the 27th ASLE Annual Meeting in Houston, Texas, May 1–4, 1972

79 citations

Journal ArticleDOI
TL;DR: In this paper, the development of thermal convection is studied for a viscoplastic fluid, and the critical Rayleigh number for linear instability is shown to be infinite for an infinite viscosity at zero shear rate, or a yield-stress.
Abstract: The development of thermal convection is studied for a viscoplastic fluid. If the viscosity is finite at zero shear rate, the critical Rayleigh number for linear instability takes the value given by a Newtonian fluid with that viscosity. The subsequent weakly nonlinear behaviour depends on the degree of shear thinning: with moderate shear thinning, convective overturning for a given temperature difference is amplified relative to the Newtonian case. If the reduction in viscosity is sufficiently sharp the transition becomes subcritical (the relevant situation for many regularized constitutive laws). For an infinite viscosity at zero shear rate, or a yield-stress, the critical Rayleigh number for linear instability is infinite. Nonlinear convective overturning, however, is still possible; we trace out how the finite-amplitude solution branches develop from their Newtonian counterparts as the yield stress is increased from zero for the Bingham fluid. Laboratory experiments with a layer of Carbopol fluid heated from below confirm that yield strength inhibits convection but a sufficiently strong perturbation can initiate overturning.

79 citations

Journal ArticleDOI
TL;DR: In this article, the peristaltic mechanism of Jeffrey fluid in a circular tube is investigated and the modeled equations are solved using perturbation technique when the ratio of the wave amplitude to the radius of the pore is small.
Abstract: The peristaltic mechanism of a Jeffrey fluid in a circular tube is investigated. The rheological effects and compressibility of the fluid are taken into account. The modeled equations are solved using perturbation technique when the ratio of the wave amplitude to the radius of the pore is small. In the second order approximation, a net flow due to a travelling wave is obtained and effects of Reynolds number, relaxation and retardation times, compressibility of the fluid and tube radius are studied. It is noticed that for the Jeffrey fluid the back flow only occurs for large values of the relaxation time and small values of the retardation time (less than 10 in the present analysis). Another interesting observation is that oscillatory behavior of the net flow rate in the Jeffrey fluid is less than that of a Maxwell fluid. Several results of other fluid models can be deduced as the limiting cases of our situation.

78 citations

Journal ArticleDOI
TL;DR: In this article, the local flow properties of various materials in a vane-in-cup geometry were studied, and they used magnetic resonance imaging techniques to measure velocities and particle concentrations in flowing Newtonian fluid, yield stress fluid, and in a concentrated suspension of noncolloidal particles in a yield-stressed fluid.
Abstract: We study the local flow properties of various materials in a vane-in-cup geometry. We use magnetic resonance imaging techniques to measure velocities and particle concentrations in flowing Newtonian fluid, yield stress fluid, and in a concentrated suspension of noncolloidal particles in a yield stress fluid. In the Newtonian fluid, we observe that the θ-averaged strain rate component drθ decreases as the inverse squared radius in the gap, in agreement with a Couette analogy. This allows direct comparison (without end-effect corrections) of the resistances to shear in vane and Couette geometries. Here, the mean shear stress in the vane-in-cup geometry is slightly lower than in a Couette cell of same dimensions, and a little higher than when the vane is embedded in an infinite medium. We also observe that the flow enters deeply the region between the blades, leading to significant extensional flow. In the yield stress fluid, in contrast with the usually accepted picture based on simulation results from the ...

78 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202341
202295
202117
202022
201920
201836