Experimental Investigation of Invar Edge Effect in Membrane LNG Tanks

2010 ◽  
Author(s):  
Mateusz Graczyk ◽  
Kjetil Berget ◽  
Joachim Allers
Keyword(s):  
Fluid Motion ◽  
Structural Response ◽  
Time History ◽  
Pressure Profile ◽  
Pressure Effects ◽  
Local Pressure ◽  
Temporal And Spatial Distribution ◽  
Containment System ◽  
Pressure Time ◽  
Time Histories

Sloshing, a violent fluid motion in tanks is of current interest for many branches of the industry, among them gas shipping. Although different methods are commonly combined for analyzing sloshing in LNG carriers, time histories of the pressure in the tanks are most reliably obtained by experiments. Very localized pressures may be important for the structural response of the tank containment system. Moreover, the typical pressure time history duration is similar to the structural natural frequency. Therefore, pressure measurements need to be performed with due account for temporal and spatial distribution. This requires a high sampling resolution both in time and space. Fine spatial resolution becomes especially important when local pressure effects are of interest, such as pressure profile passing a membrane corrugation of Mark III containment or Invar edge of No.96 containment. In this paper experimental approach applied by MARIN-TEK for analyzing sloshing phenomenon is presented. The focus is put on investigating effects of Invar edges. A transverse 2D model of a typical LNG carrier is used. Local pressure effects are investigated based on low filling level tests with different wall surfaces: smooth and with horizontal protrusions representing the surface similar to the No.96 containment system.

Experimental Investigation of Invar Edge Effect in Membrane LNG Tanks

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Mateusz Graczyk ◽  
Kjetil Berget ◽  
Joachim Allers
Keyword(s):  
Fluid Motion ◽  
Structural Response ◽  
Time History ◽  
Pressure Profile ◽  
Pressure Effects ◽  
Local Pressure ◽  
Temporal And Spatial Distribution ◽  
Containment System ◽  
Time Histories ◽  
Liquid Natural Gas

Sloshing, a violent fluid motion in tanks is of current interest for many branches of the industry, among them gas shipping. Although different methods are commonly combined for analyzing sloshing in liquid natural gas (LNG) carriers, time histories of the pressure in the tanks are most reliably obtained by experiments. Very localized pressures may be important for the structural response of the tank containment system. Moreover, the typical pressure time history duration is similar to the structural natural frequency. Therefore, pressure measurements need to be performed with due account for temporal and spatial distribution. This requires a high sampling resolution both in time and space. Fine spatial resolution becomes especially important when local pressure effects are of interest, such as pressure profile passing a membrane corrugation of Mark III containment or Invar edge of No. 96 containment. In this paper experimental approach applied by MARINTEK for analyzing sloshing phenomenon is presented. The focus is put on investigating effects of Invar edges. A transverse 2D model of a typical LNG carrier is used. Local pressure effects are investigated based on low filling level tests with different wall surfaces: smooth and with horizontal protrusions representing the surface similar to the No. 96 containment system.

Liquid Pipeline Location Specific Cyclic Pressure Determination

2018 ◽  
Author(s):  
Vlado Semiga ◽  
Aaron Dinovitzer ◽  
Sanjay Tiku ◽  
Geoff Vignal
Keyword(s):  
Pressure Range ◽  
Time History ◽  
Pressure Profile ◽  
Integrity Assessment ◽  
Cyclic Pressure ◽  
Pump Station ◽  
Pressure Time ◽  
Pipeline Segment ◽  
Time Histories ◽  
Discharge Pressure

In the majority of liquid pipelines, the pump station discharge pressure ranges are much greater than the pressure ranges experienced at the suction end of the downstream pump station. Consequently, the cyclic pressure induced fatigue damage accumulation rate is greater at the discharge end than at the suction end of a given pipeline segment. In completing an integrity assessment of a fatigue susceptible feature, assuming that the pump station discharge cyclic pressure profile applies to all features in the line segment is conservative. This conservative assumption can lead to un-necessary repairs, unintentional damage from over-prescribed maintenance, or inefficient decisions regarding maintenance action prioritization. The following paper presents the results of a Canadian Energy Pipeline Association (CEPA) initiative to develop a simple approach to define the cyclic pressure history at any point in a liquid pipeline segment based on the bounding discharge and suction pump station Supervisory Control and Data Acquisition (SCADA) pressure time history data. The approach was developed based on collected operating pipeline SCADA pressure time history data for line segments with intermediate measurement points which could be used to validate the developed model. The pressure time histories for all the locations were analyzed using a Rainflow cycle counting technique to develop pressure range spectra (i.e. histograms of pressure range events) and the cyclic pressure severity of each of the time histories was characterized by the Spectrum Severity Indicator (SSI). The SSI represents the number of annual 90MPa hoop stress cycles required to accumulate the same fatigue damage as the actual pressure spectrums. The technique presented in this paper illustrates how to infer the pressure range spectra or SSI at intermediate locations. The technique is shown to be a significant improvement (i.e. higher location specific accuracy) than either applying the discharge pressure spectrum or applying a linear interpolation between discharge and suction conditions in fatigue life assessments. The liquid pipeline cyclic pressure characterization technique presented in this paper will permit integrity assessment or severity ranking of features along a pipeline to be based on an accurate local pressure profile rather than an upper bound. This understanding will help to improve the accuracy of defect loading, one of the three main pillars in integrity assessment (i.e., loading, geometry, materials) for defects susceptible to cyclic loading (e.g., cracking, mechanical damage).

Toward Limit State Design of Ships and Offshore Structures Under Impact Pressure Actions: A State-of-the-Art Review

2006 ◽  
Vol 43 (03) ◽  
pp. 135-145
Author(s):  
Jeom Kee Paik
Keyword(s):  
Limit State ◽  
Structural Response ◽  
Time History ◽  
Rate Sensitivity ◽  
Offshore Structures ◽  
Impact Pressure ◽  
Green Water ◽  
Limit State Design ◽  
Structural Capacity ◽  
Pressure Time

In design of ships and ship-shaped offshore units, issues related to impact pressure actions arising from sloshing, slamming, green water, or explosion are of particular concern. The structural response under impact pressure actions is quite different from that under static or quasistatic actions. It has been recognized that the limit state approach is a more rational basis for structural design and safety assessment where both "demand" (loads) and "capacity" (strength) must be accurately defined. For impact pressure action cases, the demand is associated with hydrodynamics areas, taking into account the characteristics of impact pressure-time history, and the structural capacity is associated with structural mechanics areas, considering geometric and material nonlinearities together with strain rate sensitivity. This paper reviews recent advances and trends toward future limit state design of ships and offshore structures under impact pressure actions.

Numerical Prediction of Sloshing Loads in Ship Tanks

2008 ◽  
Author(s):  
Sanjay P. Singh ◽  
Anant Lal ◽  
Sharad S. Dhavalikar
Keyword(s):  
Structural Response ◽  
Time History ◽  
Ship Motions ◽  
Flow Solver ◽  
Structural Rules ◽  
Ansys Cfx ◽  
Pressure Time ◽  
Fill Level ◽  
Common Structural Rules ◽  
Oil Tankers

The present work is about the estimation of sloshing loads in partially filled tanks of a ship for design purpose. Two oil tankers of different dimensions were taken for this study. Ship motions for several wave-heading angles were computed using potential flow solver. Relevant period for sloshing was determined based on the seakeeping analysis. Critical fill levels of the tanks (with respect to sloshing) were identified from all possible set of motions. The numerical simulation of tank fluid motions for critical fill level was performed, using general fluid flow solver, ANSYS CFX. Prior to applying the method to ship tanks a validation study was carried out. The method was validated against the experimental results obtained by Hinatsu et al. (2001). Pressures at various locations of the tank were computed and were compared with the Common Structural Rules for Oil Tankers (CSR). Pressure time history obtained from computational fluid dynamics (CFD) simulations was applied on the tank bulkhead to get the structural response, using ANSYS Mechanical.

Gaseous Deflagration in Piping: Part 1 — Experimental Observations

2017 ◽  
Author(s):  
Thomas C. Ligon ◽  
David J. Gross ◽  
John C. Minichiello
Keyword(s):  
High Speed ◽  
Structural Response ◽  
Analysis And Design ◽  
Flame Acceleration ◽  
Pressure Time ◽  
Piping Systems ◽  
Time Histories ◽  
Short Test ◽  
Semi Empirical ◽  
Measured Pressure

The focus of this paper is on gaseous deflagration in piping systems and the corresponding implications on piping analysis and design. Unlike stable detonations that propagate at a constant speed and whose pressure-time histories can in some cases be predicted analytically, deflagration flame speeds and pressure-time histories are transient and depend on both the gas mixture and geometry of the pipe. This paper presents pressure and pipe strain data from gaseous deflagration experiments in long and short test apparatuses fabricated from either 2-inch or 4-inch diameter pipes. These data are used to demonstrate a spectrum of measured pressure-time histories and corresponding pipe response. It is concluded that deflagrations can be categorized as either “high” or “slow” speed with respect to pipe response. Slow deflagrations can be treated as quasi-static pressurizations, but high speed deflagrations can generate shock waves that dynamically excite the pipe. The existence of a transition from quasi-static to dynamic response has ramifications in regards to piping structural analysis and design, and a method for predicting the expected deflagration structural response using a semi-empirical flame acceleration model is proposed.

Use of RVT for Computation of In-Structure Response Spectra and Peak Responses and Comparison to Time History and Response Spectrum Analysis

2018 ◽  
Vol 34 (4) ◽  
pp. 1913-1930 ◽  
Author(s):  
Irmela Zentner
Keyword(s):  
Response Spectrum ◽  
Structural Response ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Combination Rules ◽  
Floor Response Spectra ◽  
Power Spectral ◽  
Time Histories ◽  
Definition Of

The random vibration theory offers a framework for the conversion of response spectra into power spectral densities (PSDs) and vice versa. The PSD is a mathematically more suitable quantity for structural dynamics analysis and can be straightforwardly used to compute structural response in the frequency domain. This allows for the computation of in-structure floor response spectra and peak responses by conducting only one structural analysis. In particular, there is no need to select or generate spectrum-compatible time histories to conduct the analysis. Peak response quantities and confidence intervals can be computed without any further simplifications such as currently used in the response spectrum method, where modal combination rules have to be derived. In contrast to many former studies, the Arias intensity-based definition of strong-motion duration is adopted here. This paper shows that, if the same definitions of strong-motion duration and modeling assumptions are used for time history and RVT computations, then the same result can be expected. This is illustrated by application to a simplified model of a reactor building.

Fuel-Air Ratio Determination From Cylinder Pressure Time Histories

1985 ◽  
Vol 107 (4) ◽  
pp. 252-257 ◽  
Author(s):  
J. C. Gilkey ◽  
J. D. Powell
Keyword(s):  
Time History ◽  
Operating Conditions ◽  
Cylinder Pressure ◽  
Pressure Time ◽  
Wide Range ◽  
Pressure Trace ◽  
Time Histories ◽  
High Bandwidth ◽  
Ratio Determination ◽  
Microprocessor Technology

Determining fuel-air ratio quickly over a wide range of engine operating conditions is desirable for better transient engine control. This paper describes a method based on cylinder pressure time history pattern recognition which has potential for providing such a high bandwidth measurement. The fact that fuel-air ratio has an effect on the shape of the cylinder pressure trace is well-known. It should therefore be possible to obtain the fuel-air ratio of an engine by examining the pressure trace if the engine speed, load, and EGR are known. The difficulty lies in separating the effects of unknown engine load, speed, and EGR from the fuel-air ratio effects. An algorithm was developed using a wide range of steady state experimental data from a single cylinder engine. Application of the algorithm requires the calculation of first, second and third moments of the cylinder pressure time history. Verification of the algorithm showed that the root mean square error in estimates were about 5 percent for fuel-air ratio and 3 percent for a combination of fuel-air and EGR. These results were obtained using a single pressure trace which yields a response time of 1.5 engine revolutions. The algorithm was also found to be relatively insensitive to the use of different fuels, errors in spark advance, and variations in relative humidity. Research is continuing to verify the accuracy under transient engine conditions. An operational count shows that this algorithm should be well within the limits of present microprocessor technology.

The Use of Plastic Cold Flow in the Development of an Externally Connected Transducer for Recording Pressure-Time Histories of Diesel Fuel Injection Phenomena and Its Application in Fault Diagnosis

1977 ◽  
Vol 99 (2) ◽  
pp. 274-278
Author(s):  
W. S. Heggie
Keyword(s):  
Diesel Fuel ◽  
Fuel Injection ◽  
Dynamic Pressure ◽  
Time History ◽  
Diagnostic Techniques ◽  
Field Application ◽  
Cold Flow ◽  
Pressure Time ◽  
Time Histories ◽  
Diesel Fuel Injection

An investigation of possible methods for obtaining a pressure-time history of the diesel fuel injection cycle was conducted, with the object of producing a rugged externally connected pressure transducer. A resistance technique that discriminates against characteristics not directly associated with dynamic pressure was developed and the resulting principles incorporated into the design of a compact transducer [1]. In order to eliminate the necessity of cementing a resistance element directly to the high-pressure line, a technique using the cold flow of cured resin held captive in a steel enclosure was developed. This has resulted in an instrument of equal sensitivity and fidelity which may be installed in the field by personnel without specialized training. Diagnostic techniques applied to the analysis of diesel fuel injection health are described that are considered to have practical field application, using an externally connected transducer. No numerical measure is required, the method being based on comparison of fault signatures with a healthy master. The signature is considered to contain a definite quantity of criteria evaluated by a defined series of qualities resulting in a less nebulous approach than that of random comparison by superimposure. Nine of the most common diesel fuel injection faults are induced, checked for repeatability, and used as representative examples to illustrate the method.

scholarly journals Investigation of the Impact of Seed Record Selection on Structural Response

2010 ◽  
Author(s):  
Thomas W. Houston ◽  
Greg E. Mertz ◽  
Michael C. Costantino ◽  
Carl J. Costantino
Keyword(s):  
Transfer Functions ◽  
Structural Response ◽  
Time History ◽  
Response Spectra ◽  
Recent Experience ◽  
Target Response ◽  
Target Spectrum ◽  
Time Histories ◽  
Record Selection ◽  
The Impact

Time history records are typically used to define the seismic demand for critical structures for which soil structure interaction (SSI) analyses are often required. Criteria for the development of time histories is provided in ASCE 43-05. The time histories are based on a close fit of 5% damped target response spectra. Recent experience has demonstrated that for cases where the transfer functions associated with the structural response are narrow, the ASCE 43-05 criteria can under-predict peak spectral responses in the structure by as much as 70% in some frequency ranges. One potential solution for this issue is to reinstate requirements for matching target response spectra for multiple damping levels to ASCE 43-05 criteria. However, recent probabilistic seismic hazard analyses (PSHA) do not generally contain spectra for multiple damping levels. This paper proposes an approach to generate target spectra at multiple damping levels, given the 5% damped target spectrum provided by the PSHA, utilizing catalogs of recorded earthquakes. The process of fitting time histories to multiple damped spectra is effective in correcting defficiencies observed in the computed structural response when time histories meeting the ASCE 43-05 fitting criteria are used.

Analysis of RMS Acceleration Response Spectrum for Random Pedestrian Loads

2011 ◽  
Vol 261-263 ◽  
pp. 292-298 ◽  
Author(s):  
Jie Song ◽  
Zhi Gang Song ◽  
Yi Jie Shen
Keyword(s):  
Response Spectrum ◽  
Damping Ratio ◽  
Uniform Design ◽  
Structural Response ◽  
Time History ◽  
Step Length ◽  
Acceleration Response ◽  
Step Frequency ◽  
Time Histories ◽  
Dynamic Time

Pedestrian loads are affected by such uncertain parameters as walking step frequency, step length, dynamic load factors and phases of harmonic components, which lead to the uncertainties of structural response. A new method for calculation random response spectrum based on uniform design is introduced to reduce calculation work. A few representative samples of loads time histories are simulated using uniform design, and then the RMS acceleration response spectrums are obtained by dynamic time-history analysis of beam structures with different spans and damping ratios. The RMS acceleration response spectrums which have certain percentiles are obtained by reliability analysis based on response surface. Ultimately the general forms of RMS acceleration response spectrums are deduced from the analyses of sensitivities for damping ratio and span.

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