Searched for: faculty%3A%22Mechanical%255C%252BMaritime%255C%252Band%255C%252BMaterials%255C%252BEngineering%22
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Pennings, P.C. (author), Westerweel, J. (author), Van Terwisga, T.J.C. (author)
The goal of this study is to test the hypothesis that the resonance of a tip vortex cavity is responsible for high-amplitude broadband pressure-fluctuations, typically between 40 and 70 Hz,Hz, for a full scale propeller. This is achieved with a model propeller in a cavitation tunnel. Simultaneous high-speed video shadowgraphy and sound...
journal article 2016
document
Pennings, P.C. (author), Westerweel, J. (author), Van Terwisga, T.J.C. (author)
The design of an efficient propeller is limited by the harmful effects of cavitation. The insuffcient understanding of the role of vortex cavitation in noise and vibration reduces the maximum effciency by a necessary safety margin. The aim in the present study is to directly relate propeller cavitation sound to tip vortex cavity dynamics. This...
conference paper 2015
document
Costa, P. (author), Boersma, B.J. (author), Westerweel, J. (author), Breugem, W.P. (author)
We present a collision model for particle-particle and particle-wall interactions in interface-resolved simulations of particle-laden flows. Three types of interparticle interactions are taken into account: (1) long- and (2) short-range hydrodynamic interactions, and (3) solid-solid contact. Long-range interactions are incorporated through an...
journal article 2015
document
Pennings, P.C. (author), Westerweel, J. (author), Van Terwisga, T.J.C. (author)
Models for the center frequency of cavitating-vortex induced pressure-fluctuations, in a flow around propellers, require knowledge of the vortex strength and vapor cavity size. For this purpose, stereoscopic particle image velocimetry (PIV) measurements were taken downstream of a fixed half-wing model. A high spatial resolution is required and...
journal article 2015
document
Alidai, A. (author), Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author)
The transition from the laminar to the turbulent regime in linearly stable shear flows, for example, pipe and plane Couette flows, occurs abruptly with no precursor. The evolution of turbulent spots has been studied to better understand the dynamics of this transition and the onset of turbulence. These studies have mostly focused on pipe flows...
journal article 2015
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Eisma, J. (author), Westerweel, J. (author), Elsinga, G.E. (author)
Experimental research is presented on the characteristics of interfaces and internal layers that are present in a turbulent boundary layer (TBL). Both the turbulent non-turbulent interface (T/NT) and internal shear layers are detected in snapshots of the stereo-PIV data. It turns out that the internal layers exhibit similar characteristics...
conference paper 2015
document
Van Eckeveld, A.C. (author), Pancham, A.K. (author), Westerweel, J. (author), Poelma, C. (author)
Experiments have been carried out to investigate the effect of liquid cavity filling on the behavior of the gas flow over a flat plate cavity. PIV measurements in the gas phase reveal that cavity filling can affect vortex shedding in the cavity mouth. Shear layer vortices can break-up into smaller vortices, thereby losing their periodic...
conference paper 2015
document
Greidanus, A. (author), Delfos, R. (author), Tokgoz, S. (author), Westerweel, J. (author)
Friction measurements were performed in a Taylor-Couette setup. Drag reduction was obtained with a riblet surface and indicated a drag reduction for a wide range of shear Reynolds numbers, with a maximum of 5.3% at Re_s=47000 (s+=14). Tomographic PIV verified that the friction coefficients are strongly related to the flow regimes and structures....
conference paper 2015
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Benschop, H.O.G. (author), Westerweel, J. (author), Breugem, W.P. (author)
The use of drag reducing surface textures is a promising passive method to reduce fuel consumption. Probably most wellknown is the utilisation of shark-skin inspired ridges or riblets parallel to the mean flow. They can reduce drag up to 10%. Recently another bio-inspired texture based on bird flight feather riblets has been proposed. It differs...
conference paper 2015
document
Gul, M. (author), Elsinga, G.E. (author), Westerweel, J. (author)
This study investigates the effect of the Taylor-Couette geometry, namely the aspect ratio, ?, and the gap width ratio, ?, on the torque hysteresis reported by [1]. Measurements were taken at two shear Reynolds numbers, Re s, of 5.5x10? and 9x10?.The torque was recorded while decreasing or increasing the rotation frequency ratio a=-fo/fi,...
conference paper 2015
document
Pennings, P.C. (author), Bosschers, J. (author), Westerweel, J. (author), Van Terwisga, T.J.C. (author)
The dynamic behaviour of vortex cavitation on marine propellers may cause inboard noise and vibration, but is not well understood. The main goal of the present study is to experimentally analyse the dynamics of an isolated tip vortex cavity generated at the tip of a wing of elliptical planform. Detailed high-speed video shadowgraphy was used to...
journal article 2015
document
Westerweel, J. (author), Van Terwisga, T.J.C. (author), Zverkhovskyi, O. (author)
The invention relates to a flat-bottomed vessel (1) for transporting persons or goods, the vessel comprising a drag reduction system attached to the bottom (2) of the vessel. The drag reduction system comprises: two or more turbulence members (3) extending perpendicular to the longitudinal direction of the vessel for generating an area with...
patent 2015
document
Eisma, H.E. (author), Westerweel, J. (author), Ooms, G. (author), Elsinga, G.E. (author)
New experimental research is presented on the characteristics of interfaces and internal shear layers that are present in a turbulent boundary layer (TBL). The turbulent/non-turbulent (T/NT) interface at the outer boundary of the TBL shows the presence of a finite jump in streamwise velocity and is characterised by a thin shear layer. It appears...
journal article 2015
document
Greidanus, A.J. (author), Delfos, R. (author), Tokgoz, S. (author), Westerweel, J. (author)
A Taylor–Couette facility was used to measure the drag reduction of a riblet surface on the inner cylinder. The drag on the surfaces of the inner and outer cylinders is determined from the measured torque when the cylinders are in exact counter-rotation. The three velocity components in the instantaneous flow field were obtained by tomographic...
journal article 2015
document
Greidanus, A.J. (author), Delfos, R. (author), Tokgoez, S. (author), Westerweel, J. (author)
Low drag surfaces are often desired in many industries with applications in open and closed channel flows, such as ship hulls and pipe flows. Drag reduction is a phenomenon that can have substantial energy savings, resulting in ecological and economical benefits. We use a Taylor-Couette facility as experimental instrument to measure the drag...
conference paper 2015
document
Fiscaletti, D. (author), Westerweel, J. (author), Elsinga, G.E. (author)
The investigation of flows at high Reynolds number is of great interest for the theory of turbulence, in that the large and the small scales of turbulence show a clear separation. But, as the Reynolds number of the flow increases, the size of the Kolmogorov length scale ( ? ) drops almost proportionally. Aiming at achieving the adequate spatial...
journal article 2014
document
Poelma, C. (author), Franken, M.J.Z. (author), Kim, H. (author), Westerweel, J. (author)
Contact lines are the locations where a gas, liquid and a solid meet. From everyday experience we know that such contact lines can be mobile, for example in the case of a water droplet sliding over a glass surface. However, the continuum description of the flow towards or away from a contact line implies that the forces diverge as one approaches...
conference paper 2014
document
Kloosterman, A. (author), Hierck, B. (author), Westerweel, J. (author), Poelma, C. (author)
Since fluid dynamics plays a critical role in vascular remodeling, quantification of the hemodynamics is crucial to gain more insight into this complex process. Better understanding of vascular development can improve prediction of the process, and may eventually even be used to influence the vascular structure. In this study, a methodology to...
journal article 2014
document
Beerens, J.C. (author), Ooms, G. (author), Pourquie, M.J.B.M. (author), Westerweel, J. (author)
high-viscosity liquid core surrounded by a laminar low-viscosity liquid annular layer through a vertical pipe. The numerical results are compared with theoretical results from linear stability calculations and with experimental data. The comparison is good and the general conclusion of our study is that it is very well possible to simulate...
journal article 2014
document
Franken, M.J.Z. (author), Poelma, C. (author), Westerweel, J. (author)
We describe a novel measurement method to study the contact line of a droplet at nanoscale level. The method is based on Total Internal Reflection Fluorescence Microscopy (TIRFM), which uses an evanescent excitation field produced by total internal reflection of light. The evanescent field depends on the angle of the incident light and has an...
journal article 2013
Searched for: faculty%3A%22Mechanical%255C%252BMaritime%255C%252Band%255C%252BMaterials%255C%252BEngineering%22
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