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Jahangir, S. (author), Wagner, E.C. (author), Mudde, R.F. (author), Poelma, C. (author)
Cavitation is a complicated multiphase phenomenon, where the production of vapor cavities leads to an opaque flow. Exploring the internal structures of the cavitating flows is one of the most significant challenges in this field of study. While it is not possible to visualize the interior of the cavity with visible light, we use X-ray...
journal article 2019
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Goyens, J. (author), Pourquie, M.J.B.M. (author), Poelma, C. (author), Westerweel, J. (author)
The vestibular system in the inner ear senses angular head manoeuvres by endolymph fluid which deforms a gelatinous sensory structure (the cupula). We constructed computer models that include both the endolymph flow (using CFD modelling), the cupula deformation (using FEM modelling), and the interaction between both (using fluid–structure...
journal article 2019
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Jahangir, S. (author), Ghahramani, Ebrahim (author), Neuhauser, Magdalena (author), Bourgeois, Sébastien (author), Bensow, Rickard E. (author), Poelma, C. (author)
The objective of this study is to investigate the collapsing behavior of cavitation, which leads to erosion. For this purpose, an experimental investigation was performed in a channel with a semi-circular cylinder obstacle at the Hydraulic Laboratory of ANDRITZ HYDRO in Vevey. Cavitation was achieved by employing a range of pressure differences...
conference paper 2019
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Rawat, Digvijay S. (author), Pourquie, M.J.B.M. (author), Poelma, C. (author)
Computational fluid dynamics (CFD) is a powerful method to investigate aneurysms. The primary focus of most investigations has been to compute various hemodynamic parameters to assess the risk posed by an aneurysm. Despite the occurrence of transitional flow in aneurysms, turbulence has not received much attention. In this article, we...
journal article 2019
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Hogendoorn, W.J. (author), Poelma, C. (author)
Using ultrasound in plane wave imaging mode, in combination with a proper processing strategy and the covariance function approach, we can not only better estimate the actual turbulence statistics, but we are also able to measure turbulent flows with much higher Reynolds numbers. Optimising the processing strategy by using a sliding correlation...
conference paper 2019
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Dash, A. (author), Anantharaman, Arjun (author), Greidanus, A.J. (author), Poelma, C. (author)
Ultrasound Imaging Velocimetry (UIV) is applied to a Taylor-Couette flow, for the case of pure inner cylinder rotation. By imaging a radial-azimuthal plane, two velocity components are obtained simultaneously in a two-dimensional plane. For the single-phase flow studies, Iriodin flakes (commonly used for visualizing flow structures) are used as ...
conference paper 2019
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Dash, A. (author), Jahangir, S. (author), Poelma, C. (author)
A quantitative analysis of two imaging modalities, shadowgraphy and x-ray imaging, is presented in the framework of void fraction determination. The need for this arises from the fact that shadowgraphs are sometimes utilized to quantify void fraction profiles, which is an unproven method. Time-averaged x-ray images are used to evaluate the...
journal article 2018
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Middelburg, L.M. (author), el Mansouri, B. (author), Poelma, R.H. (author), Zhang, G.Q. (author), van Zeijl, H.W. (author), Wei, J. (author)
This work describes the design, modelling and realisation of the mechanical part of a non-linear MEMS accelerometer intended for large displacement behaviour. For this, a mass/spring system was designed with an extremely low resonance frequency. In this work the mechanical behaviour was verified by measurements done using an optical setup,...
conference paper 2018
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Cornel, W.A. (author), Westerweel, J. (author), Poelma, C. (author)
The challenge presented in this research is to determine the local volumetric bubble concentration (or void fraction) in the center of a microbubble cloud with limited optical access and without disturbing the flow. By applying defocused volumetric shadowgraphy to an aerated water column we were able to measure the characteristics of single...
conference paper 2018
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Gotfredsen, Erik (author), Kunoy, Jens D. (author), Mayer, Stefan (author), Poelma, C. (author), Westerweel, J. (author), Meyer, Knud Erik (author)
The effect of pulsations in a catalyst converter is investigated with the aim of determining if a steady flow captures the same physical phenomena as the pulsating flow. For this specific case, guide vanes are mounted in the sudden expansion to obtain a uniform inlet flow to the catalytic layers. The test rig is successfully validated against...
conference paper 2018
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van Eckeveld, A.C. (author), Gotfredsen, E. (author), Westerweel, J. (author), Poelma, C. (author)
Two-phase flow in ribbed or corrugated pipes is of interest in many industrial applications. Experiments are performed to assess the flow regime characteristics in upward annular flow through vertical smooth and corrugated pipes. From high speed recordings, the flow regime and temporal film characteristics are obtained. A novel implementation...
journal article 2018
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Hogendoorn, W.J. (author), Poelma, C. (author)
Using ultrasound imaging velocimetry, we are able to present unique insight in transitional particle-laden flows. Together with a Moody diagram of time-averaged properties, we demonstrate that the laminar-turbulent transition behavior at high volume fractions is distinct from the single-phase case and cases with low volume fractions. For low...
journal article 2018
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Schreier, S. (author), Poelma, C. (author)
Sloshing impacts are highly dynamic and localized events. One problem in the measurement of sloshing impact pressures is the limited spatial resolution that can be achieved with current sensors. To overcome this hurdle a project was started to develop new sensors that allow to increase the spatial resolution of pressure measurements by a factor...
conference paper 2018
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Huang, Z.Q. (author), Poelma, R.H. (author), Vollebregt, S. (author), Koelink, M.H. (author), Boschman, E. (author), Kropf, R. (author), Gallouch, M. (author), Zhang, G.Q. (author)
This article shows the fabrication process and packaging of through polymer optical vias (TPOV). The TPOV enables encapsulation and packaging of silicon photonic systems using film assisted molding (FAM) and the creation of micron-sized through polymer optical vias. The optical vias are lithographically defined in thick film photo-resist (∼ 300...
conference paper 2018
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Middelburg, L.M. (author), el Mansouri, B. (author), Poelma, R.H. (author), van Zeijl, H.W. (author), Wei, J. (author), Zhang, G.Q. (author), van Driel, W.D. (author)
The mechanical part of inertial sensors can be designed to have a large mechanical sensitivity, but also requires the transduction mechanism which translates this displacement. The overall system resolution in mechanical inertial sensors is dictated by the noise contribution of each stage and the magnitude of each sensitivity, see also Figure...
conference paper 2018
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van Meerkerk, M. (author), Poelma, C. (author), Westerweel, J. (author)
A quasi three-dimensional stereo-camera measurement technique has been devised that is able to measure liquid free surface profiles, by scanning a light sheet. The technique will be applied to study the variability of impact pressure observed during wave impact in a newly developed experimental set-up. The set-up imposes severe optical (single...
conference paper 2018
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Silvestri, C. (author), Riccio, Michele (author), Poelma, R.H. (author), Jovic, A. (author), Morana, B. (author), Vollebregt, S. (author), Irace, Andrea (author), Zhang, G.Q. (author), Sarro, P.M. (author)
The high aspect ratio and the porous nature of spatially oriented forest-like carbon nanotube (CNT) structures represent a unique opportunity to engineer a novel class of nanoscale assemblies. By combining CNTs and conformal coatings, a 3D lightweight scaffold with tailored behavior can be achieved. The effect of nanoscale coatings, aluminum...
journal article 2018
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Jahangir, S. (author), Hogendoorn, W.J. (author), Poelma, C. (author)
Partial cavitation dynamics in an axisymmetric converging-diverging nozzle are investigated experimentally. Shadowgraphy is used to visualize and analyze different cavitation regimes. These regimes are generated by changing the global static pressure and flow velocity independently. Cloud cavitation is the most interesting and complex regime,...
journal article 2018
document
Jahangir, S. (author), Wagner, E.C. (author), Mudde, R.F. (author), Poelma, C. (author)
Cavitation is a complex multiphase phenomenon, where the production of vapor bubbles leads to opaqueness of the flow. While it is nearly impossible to visualize the interior of the cavitation region with visible light, we show that with X-ray computed tomography it is possible to obtain the time-averaged void fraction distribution in an...
conference paper 2018
document
Middelburg, L.M. (author), el Mansouri, B. (author), van Zeijl, H.W. (author), Zhang, G.Q. (author), Poelma, R.H. (author)
In this work a method is described to investigate process variations across a wafer. Through wafer MEMS spiral resonators were designed, simulated, fabricated and characterized by measuring the eigenfrequency and corresponding mode shapes. Measuring the eigenfrequency and resulting spectral behavior of resonators on different locations on the...
conference paper 2017
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