The Experts below are selected from a list of 441045 Experts worldwide ranked by ideXlab platform
Sara L. Moya - One of the best experts on this subject based on the ideXlab platform.
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rheological property measurement of drilling fluids used in geothermal wells
Applied Thermal Engineering, 2001Co-Authors: E Santoyo, G. Espinosa, S Santoyogutierrez, A. García, Sara L. MoyaAbstract:Abstract With the goal of increasing understanding of drilling fluid temperature Behaviour during geothermal well drilling operations, and for providing a database for a better development of numerical wellbore simulators, an experimental work based on a rheological evaluation of drilling fluids was carried out. High-temperature drilling fluid systems (HTDFS) which are most commonly used in the Mexican geothermal well drilling industry were selected and evaluated. Eleven water-based drilling fluids were formulated and chemically characterised in order to carry out the rheological evaluation. Dynamic experimental tests considering the Non-Newtonian Behaviour of such HTDFS were performed using a coaxial cylinder-type viscometer (Fann 50C). Drilling fluid viscosities in a programmed temperature range of 25–180°C (at a constant reservoir pressure and a shear rate of 3448.2 kPa and 170 s −1 , respectively) were measured. These dynamic viscosity measurements were then fitted to derive correlating equations for determining the drilling fluid viscosity as a function of temperature. Details of the experimental rheological tests including a complete description of the equipment and all the HTDFS used as well as the derived viscosity–temperature equations are presented.
Hubert Schwarze - One of the best experts on this subject based on the ideXlab platform.
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impact of high pressure and shear thinning on journal bearing friction
Tribology International, 2015Co-Authors: David Emanuel Sander, Hannes Allmaier, Hansherwig Priebsch, Franz Markus Reich, Mario Witt, T Fullenbach, Athanassios Skiadas, Ludwig Brouwer, Hubert SchwarzeAbstract:Abstract For the study of mixed lubrication in journal bearings, this paper employs a combined experimental and simulative approach. Extensive measurements on a journal bearing test rig with a low viscosity 0W20 multi-grade lubricant provide a solid basis which is complemented by experimental lubricant data that is measured under high pressure and high shear rates. In this paper, this data is used to investigate the impact of the piezoviscous effect and the Non-Newtonian lubricant properties on the friction power losses in journal bearings over a wide range of dynamic loads and shaft speeds. In particular, this work seeks to predict the friction power losses for journal bearings under both moderate (50 MPa peak load) and high dynamic loads (100 MPa peak load) using the recently presented accurate numerical method (Allmaier et al., 2011 [1] , Allmaier et al., 2013 [2] ). From the direct comparison to the experimental data a key finding is that the simulation conforms very closely to the measured data. To be more exact, the agreement lies within the measurement uncertainty. Following this result, the influence of the often neglected piezoviscous effect and the Non-Newtonian lubricant rheology is investigated. We conclude that both the piezoviscous effect and the Non-Newtonian Behaviour are essential to describe the lubrication with multi-grade lubricants in journal bearings. Only the consideration of both properties describes the experimental data very accurately over the entire range of operating conditions studied.
Andrea Baldini - One of the best experts on this subject based on the ideXlab platform.
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fluid film lubrication in the presence of cavitation a mass conserving two dimensional formulation for compressible piezoviscous and non newtonian fluids
Tribology International, 2013Co-Authors: Luca Bertocchi, Daniele Dini, Matteo Giacopini, Mark T Fowell, Andrea BaldiniAbstract:Abstract A mass-conserving formulation of the Reynolds equation has been recently proposed by some of the authors to deal with cavitation in lubricated contacts [1] . This formulation, based on the mathematical derivation of a linear complementarity problem (LCP), overcomes the drawbacks previously associated with the use of such complementarity formulations for the solution of cavitation problems in which reformation of the liquid film occurs. In the present paper, the methodology favoured in [1] , already successfully applied to solve textured bearing and squeeze problems in the presence of cavitation in a one dimensional domain for incompressible fluids, has been extended to include the effects of fluid compressibility, piezoviscosity and the Non-Newtonian fluid Behaviour and it has been also applied to the analysis of two dimensional problems. The evolution of the cavitated region and the contact pressure distribution are studied for a number of different configurations which can be considered as relevant benchmarks. In particular, some of the results obtained with the proposed scheme are critically analysed and compared with the predictions obtained using alternative formulations, including full CFD calculations. The stability of the proposed algorithm and its flexibility in terms of implementation of different models for compressibility, piezoviscosity and Non-Newtonian Behaviour are highlighted.
David Kilpatrick - One of the best experts on this subject based on the ideXlab platform.
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Non-Newtonian blood flow in human right coronary arteries: steady state simulations.
Journal of biomechanics, 2004Co-Authors: Barbara Mary Johnston, Peter Rex Johnston, Stuart Corney, David KilpatrickAbstract:This study looks at blood flow through four different right coronary arteries, which have been reconstructed from bi-plane angiograms. Five Non-Newtonian blood models, as well as the usual Newtonian model of blood viscosity, are used to study the wall shear stress in each of these arteries at a particular point in the cardiac cycle. It was found that in the case of steady flow in a given artery, the pattern of wall shear stress is consistent across all models. The magnitude of wall shear stress, however, is influenced by the model used and correlates with graphs of shear stress versus strain for each model. For mid-range velocities of around 0.2 m s(-1) the models are virtually indistinguishable. Local and global Non-Newtonian importance factors are introduced, in an attempt to quantify the types of flows where Non-Newtonian Behaviour is significant. It is concluded that, while the Newtonian model of blood viscosity is a good approximation in regions of mid-range to high shear, it is advisable to use the Generalised Power Law model (which tends to the Newtonian model in those shear ranges in any case) in order to achieve better approximation of wall shear stress at low shear.
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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effects of non newtonian Behaviour on the thermal performance of nanofluids in a horizontal channel with discrete regions of heating and cooling
Applied Thermal Engineering, 2016Co-Authors: Yanhai Lin, Liangliang Zhu, Wei ZhangAbstract:Abstract A numerical simulation is performed to investigate laminar forced convection nanofluid based Non-Newtonian flow in a horizontal parallel plate with discrete regions of heating and cooling. Water, pseudo-plastic and dilatant fluids are used as working base fluids. Power-law modelling is adopted to predict the effect of Non-Newtonian Behaviour on the thermal performance of nanofluids in a channel with heating (cooling) regions placed symmetrically on walls, and the remaining surfaces are considered adiabatic. The velocity and temperature fields, heat transfer coefficient ratio, and pressure drop are investigated, considering the influence of power-law index n , nanoparticle volume fraction ϕ , Reynolds number, and generalized Prandtl number. It is observed that the velocity and temperature of nanofluids may increase or decrease considerably by changing the base power-law fluids. The results reveal that nanofluids based on dilatant flow are more sensitive to the environmental heat flux than those based on pseudo-plastic fluid. Furthermore, the pressure drop increases as the power-law index rises. The findings demonstrate that the presence of Non-Newtonian effects in nanofluids can lead to improvement and optimization in the thermal performance of channels, which suggests the potential of nanofluid based power-law flow in industrial equipment heating and cooling applications.