scholarly journals Detection of Isolated Vibration Spectrum Patterns Generated in Hull and Shafting Lines which Result Shipboard Faults

2018 ◽  
Vol 6 (2) ◽  
pp. 247-255
Author(s):  
Prasad Milinda Dasanayaka ◽  
Ranjan Perera
Keyword(s):  
Vibration Spectrum ◽  
Wind Condition ◽  
Channel Measurements ◽  
Sea State ◽  
Naval Vessel ◽  
Multiple Characteristics ◽  
Vibration Signature ◽  
Vibration Signatures ◽  
The Waves

The origin of shipboard hull vibrations is dominantly determined by vessels propulsion system, main machinery, auxiliary systems, pumps, breaking of the waves at the ship hull, etc. When the ships are classified on various sizes and limitations, they demonstrate multiple characteristics of vibration signatures mainly based on the functionality of main machinery and ships’ hull. The vibration signatures generated from hull is a clear representation of the ships health and crew habitability.  The paper is focused on to a case study that the hull of a naval vessel which had undergone a major repair was inspected for suitability for further use in terms of vibration and habitability. The transferred vibration signature of the vessel was analyzed using vibration spectra in machinery and hull aspects. The measuring was done simultaneously with multi-channel measurements of the vessels vibrations at few characteristic positions.  Sea trials at following variable conditions had been carried out onboard the selected vessel. Sea State : 2-3; Loading Condition : Half Load; Wind Condition : Moderate< 15 knots; Sea Direction : Ahead, Astern

Evaluating the Coupledness of the Aerodynamics and Hydrodynamics on the Estimation of Fatigue Damage Equivalent Load for a Floating Offshore Wind Platform

2018 ◽  
Author(s):  
Samuel Kanner ◽  
Bingbin Yu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Conditions ◽  
Offshore Wind ◽  
Coupled Analysis ◽  
Offshore Wind Turbine ◽  
Wave Conditions ◽  
Equivalent Load ◽  
The Waves

In this research, the estimation of the fatigue life of a semi-submersible floating offshore wind platform is considered. In order to accurately estimate the fatigue life of a platform, coupled aerodynamic-hydrodynamic simulations are performed to obtain dynamic stress values. The simulations are performed at a multitude of representative environmental states, or “bins,” which can mimic the conditions the structure may endure at a given site, per ABS Floating Offshore Wind Turbine Installation guidelines. To accurately represent the variety of wind and wave conditions, the number of environmental states can be of the order of 103. Unlike other offshore structures, both the wind and wave conditions must be accounted for, which are generally considered independent parameters, drastically increasing the number of states. The stress timeseries from these simulations can be used to estimate the damage at a particular location on the structure by using commonly accepted methods, such as the rainflow counting algorithm. The damage due to either the winds or the waves can be estimated by using a frequency decomposition of the stress timeseries. In this paper, a similar decoupled approach is used to attempt to recover the damages induced from these coupled simulations. Although it is well-known that a coupled, aero-hydro analysis is necessary in order to accurately simulate the nonlinear rigid-body motions of the platform, it is less clear if the same statement could be made about the fatigue properties of the platform. In one approach, the fatigue damage equivalent load is calculated independently from both scatter diagrams of the waves and a rose diagram of the wind. De-coupled simulations are performed to estimate the response at an all-encompassing range of environmental conditions. A database of responses based on these environmental conditions is constructed. The likelihood of occurrence at a case-study site is used to compare the damage equivalent from the coupled simulations. The OC5 platform in the Borssele wind farm zone is used as a case-study and the damage equivalent load from the de-coupled methods are compared to those from the coupled analysis in order to assess these methodologies.

Extreme waves and surges interaction with tides during storms in winter 2013/2014.

2021 ◽  
Author(s):  
Julia Rulent
Keyword(s):  
Tidal Cycle ◽  
Grid Point ◽  
High Tide ◽  
Water Levels ◽  
Extreme Waves ◽  
Near Shore ◽  
The Uk ◽  
The Waves ◽  
Tidal Stage

&lt;p&gt;The interaction between waves, surges and tides is one of the main drivers of coastal total water levels (TWL). &amp;#160;Understanding this interaction is crucial for studying high TWL formation near shore, and to do this it is important to not only evaluate how high the TWL is but also when and where it occurs.&lt;/p&gt;&lt;p&gt;In this study we use a high resolution (1.5 km) three-way coupled (waves-atmosphere-ocean) numerical model developed by the MetOffice (UKC4) to study coastal conditions at the UK coast during the extreme events of winter 2013, which was chosen as case study because of the amount of flooding that occurred in relation to storms and surges during this period.&lt;/p&gt;&lt;p&gt;For each coastal grid point the ten strongest storms of that winter, ranked by the significant wave height (Hs) magnitude, were selected. During these storm periods, the number of hours in which Hs and surges exceeded the 90&lt;sup&gt;th&lt;/sup&gt; percentile of winter 2013 were evaluated considering what tidal stage they occurred on. The same was done for instances where high Hs and surges occurred simultaneously. The aim is to understand if specific areas were predominantly affected by one of the TWL components and how Hs and surges interacted with the tide. What was the spatial distribution of the waves, surges, and tides during winter 2013? Did extreme Hs and Surges occur more often over specific stages of the tidal cycle? Did they occur simultaneously?&amp;#160;&lt;/p&gt;&lt;p&gt;In this study we show that during the winter 2013, Hs and surges above the 90&lt;sup&gt;th&lt;/sup&gt; percentile value did occur simultaneously at all stages of the tidal cycle. They more often occurred together over the rising tide with in average 8.7% and 8.6% of instances found two and three hours before high tide. In 7.7% of cases high wave and surges also concurred at high tide.&lt;/p&gt;

Enhancement of Turning Process Using Vibration Signature Analysis

2005 ◽  
Author(s):  
Marlon C. Batey ◽  
Hamid R. Hamidzadeh
Keyword(s):  
Manufacturing Process ◽  
Vibration Analysis ◽  
Manufacturing System ◽  
Cutting Tool ◽  
Operating Conditions ◽  
Turning Process ◽  
Analysis Problem ◽  
Frequency Domains ◽  
Vibration Signature ◽  
Vibration Signatures

Analytical and experimental vibration analyses are conducted for a lathe system to detect the possibility of faults and develop an accurate cutting process. The data acquisition system utilized for this purpose processes the analog input from the manufacturing system and displays the response in both the real time and frequency domains. The vibration signatures for different arrangements are recorded to determine the dynamic characteristics of the system which includes work pieces, tool, and lathe components. These vibration signatures were analyzed to determine cause of inaccuracy in the manufacturing process and the faulty components. In this study, two major problem causing sources were identified using vibration analysis for the system under different operating conditions. In addition to the identified problems, the phenomena of cutting tool chatter with various intensities was examined and recorded during testing. In this study the best possible operating conditions for a specific turning process were determined using vibration analysis. Problem causing components for several case studies (different speeds, feed rates, and tool lengths) were identified and guidelines for improving a typical manufacturing process were recommended.

Influence of Typical Subgrade Structures on Aerodynamic Characteristics of High Speed Trains in Cross Wind Conditions

2018 ◽  
Author(s):  
Zhenxu Sun ◽  
Guowei Yang
Keyword(s):  
High Speed ◽  
Aerodynamic Characteristics ◽  
Wind Condition ◽  
Safety Control ◽  
High Speed Trains ◽  
Flow Field Characteristics ◽  
Wind Velocities ◽  
The Cross ◽  
Train Safety

Due to geographical and environmental constraints, highspeed railways use a variety of subgrade structures such as ground, embankments with different height, viaducts, etc. When trains run on embankments and viaducts, the flow around the car body is more complex than the ground. Under the action of crosswind, there are obvious differences in the cross-wind aerodynamic characteristics of high-speed trains on different subgrade structures. The unreasonable subgrade structure will affect the cross-wind safety of the train. At the same time, the structure of the train is complex, the bogie and pantograph have an important role on the flow field characteristics of the train, and the over simplified profile of the short train cannot accurately reflect the true aerodynamic characteristics of the train. In the present paper, in order to study the influence of typical subgrade structure on the aerodynamic characteristics of high speed trains, a real high-speed train with 9 carriages at the speed of 200 km/h was taken for case study, and the details of windshields, bogies and pantographs were taken into consideration. The cross wind velocities were chosen as 20, 30, 35 and 40 m/s. The aerodynamics performance of the highspeed train under the four conditions of plane ground, 3m-embankment, 6m-embankment and viaduct were simulated and compared, and the differences and regularities in the aerodynamic characteristics under cross wind conditions on different subgrade were analyzed. The results provide a reference for train safety control on complex subgrade structures under cross wind condition.

scholarly journals An Integrated Approach to Analyze Sedimentary Stock and Coastal Erosion in Vulnerable Areas: Resilience Assessment of San Vicenzo’s Coast (Italy)

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 805
Author(s):  
Francesco Bianco ◽  
Paolo Conti ◽  
Salvador García-Ayllon ◽  
Enzo Pranzini
Keyword(s):  
Coastal Erosion ◽  
Integrated Approach ◽  
Coastal Communities ◽  
Sea State ◽  
Erosion Risk ◽  
Geomorphic Features ◽  
Active Processes ◽  
Resilience Assessment ◽  
Morphological Patterns

The assessment of coastal erosion risk is a major challenge, since environmental and geomorphic features, together with sea state parameters, can seriously change the configuration of coastal areas. In addition, the anthropic actions of the coastal communities may also drastically modify the configuration of the coast in vulnerable areas. In this study, a linkage between regional mapping guidelines and national geological cartography procedures is presented as a meaningful tool in the geomorphic trends analysis for the integrated mapping of the main morphological patterns of San Vincenzo’s coastal area, in the region of Tuscany (Italy). Comparing and joining different procedures—which have different scales and topics—requires adapting the fields and the information provided in maps and databases. In this case study, a GIS morpho-sedimentological approach is developed. This GIS approach enables us to cover several issues simultaneously, such as the representation of coastal active processes, the adaptation of regional and national cartography to coastal erosion assessment, and lastly the calculation of the sedimentary stock analysis, since it represents the first attribute of coasts to be preserved in a resilience-oriented integrated assessment.

Parametric Study of Operability for a Tourist Submarine

2004 ◽  
Author(s):  
R. T. Paein Koulaei ◽  
M. Rad ◽  
S. M. Mousaviraad ◽  
S. H. Sadathosseini
Keyword(s):  
Parametric Study ◽  
Point Of View ◽  
Hydrodynamic Problem ◽  
Sea State ◽  
Strip Theory ◽  
Speed Effect ◽  
Duration Of Operation

These days, tourist submarine industry has become of increasing interest and prosperity. A tourist submarine operating beneath a seaway suffers different undesired motions which may cause difficulty in operability for the vehicle and habitability of its passengers. From this point of view, this paper studies the hydrodynamic problem of submarine operability in waves. In this investigation strip theory has been used and effects of different parameters of sea state, sea direction, depth, speed and duration of operation have been considered. Results of presented case study indicate that speed effect is insignificant while the operating depth role seems more important.

Auxiliary Turbine Generator Set Isolation System Design for US Naval Vessel

2012 ◽  
Author(s):  
Paul G. Jones ◽  
Steven L. Carmichael
Keyword(s):  
Finite Element Models ◽  
Component Level ◽  
Sea State ◽  
Turbine Generator ◽  
Full System ◽  
Naval Vessel ◽  
Isolation System ◽  
Actual Performance ◽  
Detail Design ◽  
Machinery Space

The RR4500 Auxiliary Turbine Generator (ATG) incorporates an isolation system addressing four main design requirement environments. These environments include high-impact shock, structureborne vibration, sea state motion, and installation/integration into the machinery space. Multiple design iterations were performed, beginning with a simplified system representation and expanding to full system finite element models. Specific resilient isolation mounts were selected to satisfy the competing criteria from the different requirement sets. Design resolutions passed specific requirements down to the component level and were addressed during detail design. Structures, system components, and flexible ship connections were adapted to meet the requirements needed by the isolation system. Testing of the system indicates good correlation between system predictions and actual performance.

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