Towing tank experiments on the vortex-induced vibrations of low mass ratio long flexible cylinders

2014 ◽  
Vol 48 ◽  
pp. 81-92 ◽  
Author(s):  
F.J. Huera-Huarte ◽  
Z.A. Bangash ◽  
L.M. González
Keyword(s):  
Mass Ratio ◽  
Towing Tank ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio

VIV Control and Drag Reduction Using the Guided Porosity Concept

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Fabio M. Coelho ◽  
Ricardo Franciss ◽  
Severino F. S. Neto
Keyword(s):  
Drag Reduction ◽  
Potential Theory ◽  
Experimental Tests ◽  
Experimental Results ◽  
Mass Ratio ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Moving Parts

This paper aims to discuss the effectiveness of a new passive kind of VIV (Vortex Induced Vibrations) suppression. Moreover, the proposed solutions leads to a significant drag reduction when compared with conventional proposals (strakes for instance). The concept of guided porosity is applied in experimental tests conducted with low mass ratio cylindrical models. The works also shows that the job (VIV control and drag reduction) is achieved without moving parts, in contrast with segmented fairings. It also advances in terms of the omnidirectional solution. Initially, the concept is discussed in terms of the potential theory. Then experimental results are presented in terms of displacements and forces.

Towing Tank Experiments on the Vortex-Induced Vibrations of a Long Flexible Cylinder in a Stepped Current

2013 ◽  
Author(s):  
Francisco J. Huera-Huarte ◽  
Zafar A. Bangash ◽  
Leo M. González
Keyword(s):  
Cross Flow ◽  
External Diameter ◽  
Flexible Cylinder ◽  
Towing Tank ◽  
Supporting Structure ◽  
Drag Forces ◽  
Vortex Induced Vibrations ◽  
Curvature Measurements ◽  
Low Mass ◽  
Low Mass Ratio

We describe recent results showing the dynamic response, excited by vortex shedding, of a long flexible cylinder subject to a stepped current. The experiments were conducted at the Naval Architecture Department towing tank of the Technical University of Madrid (UPM) during March 2012. The tank is 100 m long with a cross-section of 3.8 × 2.5 m, and it is able to deliver speeds over 4 m/s. A supporting structure was designed in order to provide support for a 3 m long cylinder with an external diameter of 19 mm. The cylinder was instrumented with strain gauges providing curvature measurements in the in-line and the cross-flow directions at 11 locations along its length. Tension and drag forces were also measured at both ends of the model. More than 50 runs were conducted with the cylinder being placed vertically having its lower 65% length under the water free surface, connected to the structure by means of universal joints. The supporting structure allowed to configure different top end conditions and to apply different top tensions. Tests were conducted for Reynolds numbers as high as 34000. The cylinder had a low flexural stiffness and very low mass ratio m* of 0.67. Fundamental natural frequencies were in the range from about 4 to 7.9 Hz, and the cylinder responded in modes up to the third cross-flow. In this article we will describe the experiments and the instrumentation used, the modal tests conducted and the results obtained during the experiments.

Numerical Simulation of the Multiple Branch Transverse Response of a Low Mass Ratio Elastically Supported Circular Cylinder

2006 ◽  
Author(s):  
Richard H. J. Willden
Keyword(s):  
Circular Cylinder ◽  
Maximum Amplitude ◽  
Mass Ratio ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Elastically Supported ◽  
High Degree

The paper presents the results of a numerical investigation of the transverse Vortex-Induced Vibrations of an undamped, low mass ratio elastically supported circular cylinder that was subjected to a uniform flow that resulted in a Reynolds number of 104. The numerical simulations were performed using a two-dimensional Large Eddy Simulation model. The computed cylinder response exhibits three branches; the initial, upper and lower branches. The computed initial and lower branches, which exhibit 2S and 2P modes of shedding respectively, show many similarities to those reported from experiments. However, the computed upper branch, on which a maximum amplitude of response of 0.83D was achieved, shows some dissimilarities to those reported from experiments. The failure to correctly simulate the upper branch response is thought to be due to the high degree of flow three-dimensionality that has been reported to exist on the upper branch.

Towing Tank Experiments on the Vortex-Induced Vibrations of a Flexible Cylinder With Wake Interference

2014 ◽  
Author(s):  
Francisco J. Huera-Huarte ◽  
Zafar A. Bangash ◽  
Leo M. Gonzalez
Keyword(s):  
Cross Flow ◽  
External Diameter ◽  
Flexible Cylinder ◽  
Towing Tank ◽  
Supporting Structure ◽  
Drag Forces ◽  
Vortex Induced Vibrations ◽  
Curvature Measurements ◽  
Low Mass ◽  
Low Mass Ratio

We describe recent results showing the dynamic response, excited by vortex shedding, of a long flexible cylinder subject to a stepped current immersed in the wake of another cylinder, placed upstream in tandem configuration. Experiments were conducted at the E.T.S.I. Navales towing tank of the Technical University of Madrid during March 2012. The tank is 80 m long with a cross-section of 4 × 2.5 m. A supporting structure was designed in order to provide support for a 3 m long cylinder with an external diameter of 16 mm. The cylinder was instrumented with strain gauges providing curvature measurements in the in-line and the cross-flow directions at 11 locations along its length. Tension and drag forces were also measured at both ends of the model. For these experiments, the upstream rigid cylinder was made stationary by fixing it at both ends, and it was located at different centre to centre distances. More than 200 runs were conducted, with its lower 65% length under the water free surface, connected to the structure by means of universal joints. The supporting structure allowed to configure different top end conditions and to apply different top tensions. Tests were conducted with speeds up to 1.4 m/s. The cylinder had a low flexural stiffness of 6.04 Nm2 and low mass ratio of 2.7. Fundamental natural frequencies were in the range from about 2.3 to 6.2 Hz, and the cylinder responded in modes up to the third cross-flow.

scholarly journals Photometric Analysis of Wide and Narrow Hα Band Observations of R Canis Majoris

1992 ◽  
Vol 151 ◽  
pp. 303-306
Author(s):  
M. Taghi Edalati ◽  
Timothy Banks ◽  
Edwin Budding
Keyword(s):  
Hot Spot ◽  
Optimal Estimate ◽  
Mass Ratio ◽  
Transfer Effects ◽  
Photometric Analysis ◽  
Index Variation ◽  
Algol System ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Optimisation Technique

Wide and narrow Hα lightcurves of R CMa were analysed using Wilson-Devinney (WD) and Information Limit Optimisation Technique (ILOT) approaches. A range of mass ratios, tested by both methods, led to an optimal estimate of around 0.45, at variance with the spectroscopic value. The distortion on the light curve affects the modelling, and so, in a second fitting, this was represented by a ‘hot spot’, associated with mass transfer effects. A semi-detached configuration was then derived. This is supported by the form of the Hα index variation, which has also been modelled. Although thus appearing as a ‘classical Algol’ system, R CMa retains its inherent peculiarity of low mass ratio with low period, which cannot be reconciled with conservative evolution scenarios.

scholarly journals Marginally low mass ratio close binary system V1191 Cyg

New Astronomy ◽  
2012 ◽  
Vol 17 (1) ◽  
pp. 46-49 ◽  
Author(s):  
B. Ulaş ◽  
B. Kalomeni ◽  
V. Keskin ◽  
O. Köse ◽  
K. Yakut
Keyword(s):  
Binary System ◽  
Close Binary System ◽  
Close Binary ◽  
Mass Ratio ◽  
Low Mass ◽  
Low Mass Ratio
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