118,146 research outputs found
Report on the open meeting of restricted ECFA held at the University of Athens 10 February 1983
No full textThis report summarizes the opening presentation by J. Mulvey, L. Resvanis and T. Filippas, and the main points raised during the following discussion on the situation of high-energy physics in Greece
Modelling Risers With Partial Strake Coverage
No full textThis paper compares model test data for risers with partial strake coverage to predictions made with the Vortex-Induced Vibration (VIV) prediction program SHEAR7 Versions 4.5 and 4.6. It is shown that new features in Version 4.6 substantially enhance the capability for predicting the VIV response of risers with partial coverage. Experimental data is taken from two large L/D tests: the NDP 38 m long riser tests and the Deepstar-Miami, 500 foot long riser. New methods are described for modeling risers partially covered with helical strakes. Key SHEAR7 parameters are recommended, based on parametric investigations to calibrate the model against the available experimental data. Recommended modeling procedures are described so as to facilitate implementation by SHEAR7 users in their VIV modeling tasks.SHEAR7 JI
Response Variability in Flexible Cylinder VIV Model Test Data
No full textThis paper presents some results from the 2011 SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented 38m long flexible cylinders at Reynolds numbers up to 220,000. The main objective it to present the experimental results in a manner that describes the response variability that exists in the measured response data. Despite the fact that VIV is known to be a stochastic process, this is rarely addressed in the literature and currently there is no framework or 'best-practice' in the VIV community that can address statistically non-stationary data. In this paper, the experimental measurements are treated like non-stationary time-series and all statistical quantities which are typically of interest are computed with the use of short duration moving windows (or time-gates). A novel way of plotting and presenting VIV response data for flexible cylinders is introduced that is capable of revealing the inherent variability that exists in the cylinder's response.SHEAR7 Joint Industry Projec
Effects of Strake Coverage and Marine Growth on Flexible Cylinder VIV
No full textIn this paper we present some results from the recent SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 220,000. The main objective is to present the experimental results describing the effectiveness of different amounts of strake coverage and to explore the influence of simulated marine growth. The data is presented in terms of CF response amplitudes and rainflow-counted damage rates due to the combined CF and IL bending stresses. All results are compared with the bare cylinder cases which will be used as a reference to determine how effective the strakes are in suppressing VIV and how this effectiveness can be affected by marine growth. The results show that even small bare sections (missing strakes) can lead to significant VIV response. We also observe that moderate amounts of marine growth can quickly negate any suppression coming from the strakes.SHEAR7 JI
The Identification of Power-In Region in Vortex-Induced Vibration of Flexible Cylinders
No full textThis paper proposes a novel method to identify the power-in regions of long flexible cylinders subjected to vortex-induced vibration (VIV). It also attempts to address a practical problem: “Will a secondary power-in region appear after the primary power-in region is covered with suppression devices?” The source of data is a recent model test on a 38 meter long flexible cylinder, densely instrumented with fiber optic strain gauges and accelerometers. For pipes with partial coverage of suppression devices in uniform flow, the bare region would be expected to be a power-in region and the section with suppression devices is expected to be a power-out region. Experimental data from these types of tests are used to benchmark the proposed power-in zone identification method. The method is then used to identify the power-in zones on a bare cylinder in a sheared flow. This paper also explores the occurrence of secondary power-in regions that may exist, when suppression devices are placed in the primary power-in zone. Secondary power-in regions were observed. Lessons learned from the power-in region identification in sheared flows will be a useful tool for designer/engineers choosing where to place suppression devices.DeepStar (Consortium)SHEAR7 JI
Ramp Tests: A Novel Approach to VIV Model Testing of Flexible Cylinders Using Continuously Varying Towing Speeds
No full textIn this paper we present a small portion of the results from the 2011 SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 150,000 in order to study the Vortex-Induced Vibration (VIV) response in uniform current profiles. This paper presents the experimental results collected from a series of tests where the towing speed was continuously varied while the cylinder and carriage traversed the basin. As the cylinder is accelerated (or decelerated) the incident current speed is continuously changing which means that multiple modes can be excited consecutively in a single tow through the basin. These varying towing speed tests are collectively referred to as ‘ramp tests’. The response data collected in these ‘ramp tests’ are presented in terms of CF response amplitudes and strains and are carefully compared with the response data collected during conventional steady towing speed tests. The data shows that when the acceleration of the carriage is kept below a critical value the ‘ramp tests’ are then able to provide VIV response information which is equivalent to that obtained from many constant speed tests. One ramp test provides the equivalent response data of (up to) 10 constant speed tests in a single run. This paper also introduces a dimensionless parameter γ, which determines if the proposed acceleration for a ramp test is within acceptable limits and may be used as a substitute for many constant speed tests. The parameter can be used to determine the appropriate acceleration or deceleration rate in order to ensure that a ramp test will yield suitable VIV response data. The parameter also allows one to know quickly whether or not fully developed VIV is possible in a given set of unsteady flow conditions.SHEAR7 JIPSHELL International Exploration and Production Co
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effects of Strake Coverage and Marine Growth on Flexible Cylinder Vortex-Induced Vibrations
No full textThis paper presents some results from the recent SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 220,000. The main objective is to present the experimental results describing the effectiveness of different amounts of strake coverage and to explore the influence of simulated marine growth. The data are presented in terms of cross-flow (CF) response amplitudes and rainflow-counted damage rates due to the combined CF and in-line (IL) bending stresses. All the results are compared with the bare cylinder cases which will be used as a reference to determine how effective the strakes are in suppressing vortex-induced vibrations (VIV) and how this effectiveness can be affected by marine growth. The results show that even small bare sections (missing strakes) can lead to significant VIV response. Finally, the tests revealed that even moderate amounts of marine growth can quickly negate any suppression coming from the strakes.SHEAR7 JI
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
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