| 1. |
- Silva, R., et al.
(author)
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Validating dilute settling suspensions numerical data through MRI, UVP and EIT measurements
- 2016
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In: Flow Measurement and Instrumentation. - : Elsevier. - 0955-5986 .- 1873-6998. ; 50, s. 35-48
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Journal article (peer-reviewed)abstract
- The measurement of fluid dynamic quantities are of great interest both for extending the range of validity of current correlations to be used in equipment design and for verification of fundamental hydrodynamic models. Studies where comparisons are made between imaging techniques serve to provide confidence on the validity of each technique for the study of multiphase flow systems. The advantage of cross-validation is that it can help establish the limitations of each technique and the necessary steps towards improvement. A small amount of comparative studies are found in the literature and none of them reports the study of settling particles suspension flow using simultaneously Ultrasonic Velocity Profiling (UVP), Magnetic Resonance Imaging (MRI) and Electrical Impedance Tomography (EIT), at least not to the best of the authors knowledge. In the present paper the authors report efforts made on the characterization of dilute suspensions of glass particles in turbulent flow, with increasing flow velocities and particles concentrations, in a pilot rig at a laboratorial scale, using both MRI, EIT and UVP: direct comparisons of EIT, MRI and UVP measurements acquired and mixture model numerical simulations are presented and the level of agreement explored.
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| 2. |
- Faia, Pedro M., et al.
(author)
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A comparative study of magnetic resonance imaging, electrical impedance tomography and ultrasonic doppler velocimetry for semi-dilute fibre flow suspension characterisation
- 2016
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In: International Journal of Computational Methods & Experimental Measurements. - : WIT Press Ltd.. - 2046-0546 .- 2046-0554. ; 4:2, s. 165-175
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Journal article (peer-reviewed)abstract
- Experimental comparisons between imaging techniques serve to provide confidence in the validity of each technique for the study of multiphase flow systems. Such cross-validation can establish the limitations of each technique quantitatively. In the present paper, the authors report efforts made on the characterization of semi-dilute, mono-dispersed suspensions of rayon fibres in turbulent water flow using Magnetic Resonance Imaging (MRI), Ultrasound Velocity Profiling (UVP) and Electrical Impedance Tomography (EIT). Increasing flow velocities and fibre concentration were studied using these three experimental techniques. For lower fibre concentrations more uniform distributions were observed and as flow velocity increased fibre agglomerations were found in the centre region of the pipe.
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| 3. |
- Håkansson, Karl M. O., et al.
(author)
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Nanofibril Alignment in Flow Focusing : Measurements and Calculations
- 2016
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:27, s. 6674-6686
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Journal article (peer-reviewed)abstract
- Alignment of anisotropic supermolecular building blocks is crucial to control the properties of many novel materials. In this study, the alignment process of cellulose nanofibrils (CNFs) in a flow-focusing channel has been investigated using small-angle X-ray scattering (SAXS) and modeled using the Smoluchowski equation, which requires a known flow field as input. This flow field was investigated experimentally using microparticle-tracking velocimetry and by numerically applying the two-fluid level set method. A semidilute dispersion of CNFs was modeled as a continuous phase, with a higher viscosity as compared to that of water. Furthermore, implementation of the Smoluchowski equation also needed the rotational Brownian diffusion coefficient, which was experimentally determined in a shear viscosity measurement. The order of the nanofibrils was found to increase during extension in the flow-focusing channel, after which rotational diffusion acted on the orientation distribution, driving the orientation of the fibrils toward isotropy. The main features of the alignment and dealignment processes were well predicted by the numerical model, but the model overpredicted the alignment at higher rates of extension. The apparent rotational diffusion coefficient was seen to increase steeply as the degree of alignment increased. Thus, the combination of SAXS measurements and modeling provides the necessary framework for quantified studies of hydrodynamic alignment, followed by relaxation toward isotropy.
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| 4. |
- Mittal, Nitesh, et al.
(author)
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Ultrastrong and Bioactive Nanostructured Bio-Based Composites
- 2017
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 11:5, s. 5148-5159
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Journal article (peer-reviewed)abstract
- Nature’s design of functional materials relies on smart combinations of simple components to achieve desired properties. Silk and cellulose are two clever examples from nature–spider silk being tough due to high extensibility, whereas cellulose possesses unparalleled strength and stiffness among natural materials. Unfortunately, silk proteins cannot be obtained in large quantities from spiders, and recombinant production processes are so far rather expensive. We have therefore combined small amounts of functionalized recombinant spider silk proteins with the most abundant structural component on Earth (cellulose nanofibrils (CNFs)) to fabricate isotropic as well as anisotropic hierarchical structures. Our approach for the fabrication of bio-based anisotropic fibers results in previously unreached but highly desirable mechanical performance with a stiffness of ∼55 GPa, strength at break of ∼1015 MPa, and toughness of ∼55 MJ m–3. We also show that addition of small amounts of silk fusion proteins to CNF results in materials with advanced biofunctionalities, which cannot be anticipated for the wood-based CNF alone. These findings suggest that bio-based materials provide abundant opportunities to design composites with high strength and functionalities and bring down our dependence on fossil-based resources.
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