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Статті в журналах з теми "Swell coefficient"
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Potter, Henry. "Swell and the drag coefficient." Ocean Dynamics 65, no. 3 (February 21, 2015): 375–84. http://dx.doi.org/10.1007/s10236-015-0811-4.
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Rindraharisaona, E. J., E. Cordier, G. Barruol, F. R. Fontaine, and M. Singh. "Assessing swells in La Réunion Island from terrestrial seismic observations, oceanographic records and offshore wave models." Geophysical Journal International 221, no. 3 (March 13, 2020): 1883–95. http://dx.doi.org/10.1093/gji/ggaa117.
Повний текст джерелаАнотація:
SUMMARY La Réunion Island in the southwest Indian Ocean is seasonally affected by austral swells among which some extreme events may have strong impacts on coastal infrastructures. The very limited number of sensors available on and around the island and in the whole SW Indian Ocean impedes any direct monitoring of the swell activity. In this study, we analyse direct observations of the ocean swell by combining terrestrial measurements of the microseismic noise with in situ oceanographic observations issued from two pressure gauges and an Acoustic Doppler Current Profiler (ADCP), together with swell numerical modelling. The reliability of the terrestrial seismic station to characterize the ocean activity in both the primary and secondary microseisms peaks (PM and SM, respectively), and also in the long period secondary microseismic peak (LPSM) for the case of La Réunion Island is presented and discussed here. By computing the hourly RMS of the PM and LP(SM) amplitudes, we establish a transfer function between the PM and (LP)SM amplitude and the maximum wave height, which appears to be valid for any PM and LPSM amplitudes >0.15 μm and >1.0 μm, respectively. The correlation coefficient between the PM amplitude and the wave height is >0.92. It suggests that the PM amplitude can be used as a robust proxy for the swell height and may help calibrating the wave heights from other independent observable. For some swell events, we observe LPSM that correlate well (>0.91) with the local wave height suggesting a generation by coastal swell reflection. From polarization and spectral analyses, directions and periods of swells are also well retrieved from seismic data. Finally, continuous measure of the SM amplitude shows that it can be used as precursor information for distant swells that may hit La Réunion Island a few days after their generation in the southern Indian Ocean.
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Mitsoulis, Evan. "Annular Extrudate Swell of Newtonian Fluids: Effects of Compressibility and Slip at the Wall." Journal of Fluids Engineering 129, no. 11 (June 5, 2007): 1384–93. http://dx.doi.org/10.1115/1.2786491.
Повний текст джерелаАнотація:
Numerical simulations have been undertaken for the benchmark problem of annular extrudate swell present in pipe extrusion and parison formation in blow molding. The effects of weak compressibility and slip at the wall are studied through simple linear laws. The finite element method is used to provide numerical results for different inner/outer diameter ratios κ under steady-state conditions for Newtonian fluids. The present results provide the shape of the extrudate, and, in particular, the thickness and diameter swells, as a function of the dimensionless compressibility and slip coefficients, B and Bsl, respectively. The pressures from the simulations have been used to compute the excess pressure losses in the flow field (exit correction). Weak compressibility slightly affects the thickness swell (about 1% in the range of simulations 0⩽B⩽0.02) mainly by a swell reduction, while slip drastically reduces the swelling to 1–2% for obvious slip (Bsl≈1) and to 0 for perfect slip (Bsl>10). The exit correction increases with increasing compressibility levels and is highest for the tube (κ=0) and lowest for the slit (κ=1). It decreases monotonically to 0 as the dimensionless slip coefficient reaches its asymptotic limit of perfect slip. All results are ordered with the diameter ratio κ, between the limits of tube (κ=0) and slit (κ=1).
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Wu, Lichuan, Anna Rutgersson, and Erik Nilsson. "Atmospheric Boundary Layer Turbulence Closure Scheme for Wind-Following Swell Conditions." Journal of the Atmospheric Sciences 74, no. 7 (July 1, 2017): 2363–82. http://dx.doi.org/10.1175/jas-d-16-0308.1.
Повний текст джерелаАнотація:
Abstract Over the ocean, atmospheric boundary layer turbulence can be altered by underlying waves. Under swell conditions, the impact of waves on the atmosphere is more complicated compared to that under wind-wave conditions. Based on large-eddy simulation (LES), the wind-following swell impact on the atmospheric boundary layer is investigated through three terms: swell-induced surface momentum flux, the vertical profile of swell-induced momentum flux, and the swell impact on atmospheric mixing. The swell-induced surface momentum flux displays a decreasing trend with increasing atmospheric convection. The swell-induced momentum flux decays approximately exponentially with height. Compared with atmospheric convection, the decay coefficient is more sensitive to wave age. Atmospheric mixing is enhanced under swell conditions relative to a flat stationary surface. The swell impact on the atmospheric boundary layer is incorporated into a turbulence closure parameterization through the three terms. The modified turbulence closure parameterization is introduced into a single-column atmospheric model to simulate LES cases. Adding only the swell impact on the atmospheric mixing has a limited influence on wind profiles. Adding both the impact of swell on the atmospheric mixing and the profile of swell-induced momentum flux significantly improves the agreement between the 1D atmospheric simulation results and the LES results, to some extent simulating the wave-induced low-level wind jet. It is concluded that the swell impact should be included in atmospheric numerical models.
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Clemo, Henry F., and Clive M. Baumgarten. "Swelling-activated Gd3+-sensitive Cation Current and Cell Volume Regulation in Rabbit Ventricular Myocytes." Journal of General Physiology 110, no. 3 (September 1, 1997): 297–312. http://dx.doi.org/10.1085/jgp.110.3.297.
Повний текст джерелаАнотація:
The role of swelling-activated currents in cell volume regulation is unclear. Currents elicited by swelling rabbit ventricular myocytes in solutions with 0.6–0.9× normal osmolarity were studied using amphotericin perforated patch clamp techniques, and cell volume was examined concurrently by digital video microscopy. Graded swelling caused graded activation of an inwardly rectifying, time-independent cation current (ICir,swell) that was reversibly blocked by Gd3+, but ICir,swell was not detected in isotonic or hypertonic media. This current was not related to IK1 because it was insensitive to Ba2+. The PK/PNa ratio for ICir,swell was 5.9 ± 0.3, implying that inward current is largely Na+ under physiological conditions. Increasing bath K+ increased gCir,swell but decreased rectification. Gd3+ block was fitted with a K0.5 of 1.7 ± 0.3 μM and Hill coefficient, n, of 1.7 ± 0.4. Exposure to Gd3+ also reduced hypotonic swelling by up to ∼30%, and block of current preceded the volume change by ∼1 min. Gd3+-induced cell shrinkage was proportional to ICir,swell when ICir,swell was varied by graded swelling or Gd3+ concentration and was voltage dependent, reflecting the voltage dependence of ICir,swell. Integrating the blocked ion flux and calculating the resulting change in osmolarity suggested that ICir,swell was sufficient to explain the majority of the volume change at –80 mV. In addition, swelling activated an outwardly rectifying Cl− current, ICl,swell. This current was absent after Cl− replacement, reversed at ECl, and was blocked by 1 mM 9-anthracene carboxylic acid. Block of ICl,swell provoked a 28% increase in swelling in hypotonic media. Thus, both cation and anion swelling-activated currents modulated the volume of ventricular myocytes. Besides its effects on cell volume, ICir,swell is expected to cause diastolic depolarization. Activation of ICir,swell also is likely to affect contraction and other physiological processes in myocytes.
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Phanikumar, B. R. "Volume change behaviour of an expansive clay blended with lime and pond ash – controlling swell." Quarterly Journal of Engineering Geology and Hydrogeology 54, no. 1 (June 18, 2020): qjegh2020–046. http://dx.doi.org/10.1144/qjegh2020-046.
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This paper presents the influence of lime content on free swell index (FSI) of an expansive clay powder passing through a 425 µm sieve and on some significant swell-compressibility characteristics of oven-dry, expansive clay with grains of a size <4.75 mm. One-dimensional swell-consolidation tests were conducted on the expansive clay passing through a 4.75 mm sieve to which lime powder (CaOH2) was added at 0, 1, 2 and 4% by dry weight of the clay. Swell potential, swelling pressure, coefficient of compressibility (av), compression index (Cc) and linear shrinkage (LS) were evaluated. While av, Cc and LS decreased significantly with increasing lime content, swelling pressure increased. Heave and swell potential also decreased with increasing lime content but only up to 2% and were found to have increased at 4% lime content. The paper also compares the swell-compressibility behaviour of 2% lime-blended expansive clay lumps and powders. Heave and swell potential were higher for clay powder than for clay lumps at 2% lime. However, swelling pressure (ps) was found to be more for clay lumps than clay powder. Furthermore, the paper also presents the variation of FSI and swell-compressibility characteristics of another expansive clay powder (of different properties) blended with pond ash contents of 0, 5, 10, 15 and 20%. One-dimensional swell-consolidation tests were conducted on clay–pond ash blends in an oedometer. Swell potential and swelling pressure decreased up to 15% of pond ash content and increased thereafter, when pond ash content was increased to 20%. FSI of the ash-blended clay specimens was also determined. FSI continuously decreased with increase in pond ash content.
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Chernukha, Anton, Andrii Chernukha, Pavlo Kovalov, and Alexander Savchenko. "Thermodynamic Study of Fire-Protective Material." Materials Science Forum 1038 (July 13, 2021): 486–91. http://dx.doi.org/10.4028/www.scientific.net/msf.1038.486.
Повний текст джерелаАнотація:
The paper considers the material for the protective coating of building structures made of wood. The possibility of chemical processes occurring in the material leading to its expansion has been studied. The coefficient of expansion of the material when heated is practically established. It has been established that the material can swell, both under the influence of flame and when the temperature rises at a low speed. Swelling coefficient at the same time it reaches 8. The temperature range of swelling is 150–250 С, which is confirmed by thermodynamic calculations and experimentally. The temperature at which the material begins to swell is lower than the temperature of thermal destruction of wood.
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Erzin, Yusuf. "Artificial neural networks approach for swell pressure versus soil suction behaviour." Canadian Geotechnical Journal 44, no. 10 (October 2007): 1215–23. http://dx.doi.org/10.1139/t07-052.
Повний текст джерелаАнотація:
In this study, the swell pressure versus soil suction behaviour was investigated using artificial neural networks (ANNs). To achieve this, the results of the total suction measurements using thermocouple psychrometer technique and constant-volume swell tests in oedometers performed on statically compacted specimens of Bentonite–Kaolinite clay mixtures with varying soil properties were used. Two different ANN models have been developed to predict the total suction and swell pressure. The ANNs results were compared with the experimental values and found close to the experimental results. Moreover, several performance indices such as correlation coefficient, variance account for (VAF), and root mean square error (RMSE) were calculated to check the prediction capacity of the ANN models developed. Both ANN models have shown a high prediction performance based on the performance indices. Therefore, it can be concluded that the initial soil suction is the most relevant state of suction that characterizes the potential swell pressures.
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Wang, Yingchao, Hongwen Jing, Lijun Han, Liyuan Yu, and Qiang Zhang. "Risk analysis on swell–shrink capacity of expansive soils with efficacy coefficient method and entropy coefficient method." Applied Clay Science 99 (September 2014): 275–81. http://dx.doi.org/10.1016/j.clay.2014.07.005.
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Lucian, Charles, Staffan Hintze, and Joseph J. Msambichaka. "A geotechnical Study on the Characteristics of Swell-Shrink Soils in Kibaha, Tanzania." Tanzania Journal of Engineering and Technology 30, no. 2 (December 31, 2007): 92–97. http://dx.doi.org/10.52339/tjet.v30i2.402.
Повний текст джерелаАнотація:
The properties of Swell-shrink of the soils in Kibaha were studied. Geotechnical and mineralogical tests were carried outon disturbed and undisturbed samples recovered from trial pits at different locations. Using empirical relationships, theswelling potential of the soil was established in correlation with the soil plasticity limits and grain size analysis (claycontents). The average values for the plastic, liquid and linear shrinkage limits for soils were 22.2%, 60.7% and 14.5%respectively. The plasticity Index (PI) which is the difference between liquid limits and plastic limits ranges from 27% to47.4% with an average of 38.5%. The natural water content is very small ranging from 7% to 11% with an average of9.6% which is smaller than the corresponding shrinkage limit.Furthermore, the samples were tested for percentage of volume change in free swell tests and swelling pressure in one-dimensional swell tests. The free swell and upward pressure were in the excess of 100% to 150% and 50 kParespectively. In addition, the coefficient of linear extensibility ranged from 0.09 to 0.14 signifying high to very high swell-shrink potential.Finally, the main clay mineral present in the sample was determined by running the X-ray diffraction (XRD) test. The x-ray diffraction scan indicated the presence of high proportion of clay minerals (smectite) in the soils.
Дисертації з теми "Swell coefficient"
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Carlsson, Björn. "Implementation and Analysis of Air-Sea Exchange Processes in Atmosphere and Ocean Modelling." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9520.
Повний текст джерелаАнотація:
To understand and to predict the weather and climate, numerical models are important tools and it is crucial that the controlling processes are described correctly. Since 70% of the global surface is covered with water the description how the ocean and atmosphere communicates has a considerable impact. The ocean–atmosphere exchange occurs through transport of momentum (friction) and heat, governed by turbulent eddies. The sea surface is also an important source of turbulence in both directions. The scales of the turbulent eddies cannot be resolved in ocean and climate models. Therefore, the turbulent exchanges have to be related to mean variables, such as wind speed and temperature differences. By using measurements, new methods to describe the air–sea exchange during two specific processes were developed. These processes are the so-called UVCN-regime (Unstable Very Close to Neutral stratification) and swell, i.e. waves which are not produced by the local wind. These processes were included in an ocean model and in a regional atmospheric climate model and the impact was investigated. The UVCN-regime enhances the heat transport significantly during the autumn and winter months in the ocean model. This results in a shallower well-mixed surface layer in the ocean. Wind-following swell reduces the surface friction, which is very important for the atmosphere. Some secondary effects in the climate model are reduced low-level cloud cover and reduced precipitation by more than 10% over sea areas. Locally and for short periods the impact is large. It is important to include the UVCN-regime and the swell impact in models, to make simulations more reliable.
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Guibourg, Sandrine. "MModélisations numérique et expérimentale des houles bidimensionnelles en zone cotière." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10160.
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Une analyse theorique detaillee des equations de boussinesq et de serre a ete realisee. Les domaines de validite de chaque equation ont ete determines theoriquement. Ces equations d'ondes longues sont discretisees selon un schema aux differences finies pour des ondes de surface libre sur fond plat et fond variable. Par le biais d'une comparaison numerique avec des essais experimentaux d'ondes longues sur fond plat, les modeles numeriques ont ete etendus a la description des ondes courtes. Un terme dispersif correctif a ete introduit pour ameliorer les capacites dispersives des modeles. Des essais numeriques de propagation d'ondes longues sur un talus ont egalement ete compares aux experiences. Une etude de l'interaction d'une houle courte de haute frequence avec une onde solitaire nous a conduit a mesurer le dephasage que subit l'onde courte apres le passage du soliton. Nous nous sommes consacres a la validation experimentale d'une comparaison entre les modeles de boussinesq et de serre sur des plages peu inclinees, ainsi qu'a l'evolution du nombre d'ursell le long de la plage. L'etude experimentale a ensuite ete etendue aux phenomenes de run up, de run down et aux calculs des coefficients de reflexion des plages etudiees. Pour calculer numeriquement les run up, nous avons ameliore le modele de serre par des conditions de trait de cote variable
Частини книг з теми "Swell coefficient"
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Fakeye, Attah, Olusegun Ige, and Olufemi Ogunsanwo. "Multivariate Assessment of California Bearing Ratio with Contrasted Geotechnical Properties of Soils in Ilorin-Lokoja Highway." In Engineering Geology. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.93523.
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California Bearing Ratio (CBR) is an important parameter used in designing pavement layers in road construction but testing this parameter requires time, labor, and huge cost. The study therefore applies multivariate approach to evaluate CBR based on contrasted geotechnical parameters along Ilorin-Lokoja highway. The results obtained showed that the migmatite-gneiss-derived soils are slightly more fines (< 0.075 mm; 7.4–59.6%), more plastic (PI; 1.6–39%), and have low strength (MDD = 1.8 mg/m3; CBR = 29.0%) than the metasediments (11–57.7%, 2.0–30%, 1.6 mg/m3, 23.6%) and older granite soils (8.2–32.7%, 2.6–13.4%, 1.7 mg/m3, 27.8%), respectively. The principal component analysis (PCA) revealed three major components (eigenvalues >1) which accounted for 83.8% of the total variance at the rate of 33.4, 14.7, and 11.4%. Major contributing variables for the components were fines (R = 0.87), plasticity index (R = 0.7), and coarse sand (R = 0.67%). Spatial distribution of these groups established interplay of sediment-gradation and moisture-connection evident in hierarchical cluster analysis that revealed patterns of homogeneity and soil relationships. Regression analysis established five models from predictor variables such as fines, activity, free swell, liquid and plastic limits, weighted plasticity index, optimum moisture content, and maximum dry density with the coefficient of determination (R2 = 0.33) and root mean square error (RMSE) of 7.80.
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Zahid Qamar, Sayyad, Maaz Akhtar, and Tasneem Pervez. "Swelling Elastomers: Comparison of Material Models." In Swelling Elastomers in Petroleum Drilling and Development - Applications, Performance Analysis, and Material Modeling. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94726.
Повний текст джерелаАнотація:
Little data is available about the material properties and swelling response of the elsatomers used in swell packers. This information is necessary for modeling and simulation of these elastomers in different petroleum applications. An experimental setup was therefore designed and implemented at Sultan Qaboos University (SQU) to investigate the material behavior of these elastomers under tension and compression, so that these properties could be used for different simulations. Before developing a finite element model (FEM) of elastomer seal performance, it was felt that a thorough evaluation needs to be carried out to decide which of the currently available material models is most suitable for swelling elastomers. This comparison translates into the selection of the correct strain energy function for accurate determination of material coefficients. Different hyperelastic material models are compared here. Experimental investigations under tensile and compressive loads, along with their numerical analysis are presented in detail in this chapter.
Тези доповідей конференцій з теми "Swell coefficient"
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Madduri, Sushma, William Infantolino, Bahgat G. Sammakia, Seungbae Park, Haojun Zhang, and Satish C. Chaparala. "Moisture Concentration and Temperature Dependence of the Coefficient of Hygroscopic Swelling (CHS)." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12243.
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This paper presents an experimental and computational study done on an epoxy to determine the effect of moisture level and temperature on the Coefficient of Hygroscopic Swelling (CHS). When a non-hermetic package is exposed to a humid environment, the adhesives used in the package absorb moisture and swell. This can induce stresses in the package that can lead to failure. The Coefficient of Hygroscopic Swelling is defined as the ratio of hygroscopic strain to the moisture concentration in the material. It has been found from prior literature that hygroscopic strains are significant and have to be accounted for in reliability modeling [1]. Prior research investigated the measurement of CHS experimentally using techniques such as thermo mechanical analysis (TMA) [1] [2], moire´ interferometry [3], and digital image correlation (DIC) [4]. An experimental method using the TMA technique was used to measure the CHS [1], but further analysis using improved techniques was recommended to get a more precise measurement. One of the goals of this paper was to investigate experimental and numerical techniques that would help better understand various factors that affect the measurement. This paper focuses on measurement of CHS for an epoxy used in optoelectronic packaging. The DIC technique was chosen for measurement of CHS. Moisture loss during the test leads to a change in the moisture concentration in the sample. While it may be thought that the moisture loss during the DIC scan can be assumed negligible due to the short test time compared to other methods, this assumption did not hold well for the epoxy material tested. The ramp rate chosen for the measurement will affect the amount of moisture lost from the sample. This has to be carefully chosen to minimize the moisture loss. These effects have to be accounted for in the CHS computation. The CHS value calculated will be significantly affected if these factors are high within the range of the measurement. This paper describes the investigation to minimize such effects in the measurement of CHS and attempts to account for them using computational methods. The CHS of an epoxy material was measured and its dependence on temperature and moisture concentration was determined.
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Xu, Fumin, and Will Perrie. "Spectral Properties of Cyclone-Generated Waves in Deep and Shallow Water." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57824.
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Juan is recorded as one of the most damaging storms in the modern history of Nova Scotia, Canada. In this paper, the spectral evolution characteristics of waves generated by hurricane Juan are studied, based on the observed 1D wave spectra along Juan’s track in deep open ocean waters (buoy 44137) and the 2D wave spectra in shallow coastal waters at the directional waverider (DWR) location. Valuable results are obtained for cyclone-generated wave spectral properties, in both deep and shallow waters. In deep water, as illustrated at buoy 44137, the spectral variation, spectra pattern development, spectral peak frequency, cut-off frequency coefficient and high frequency spectral tail of the wave spectra are analyzed, before, during and after the cyclone’s passing. Thus, the spectral variation characteristics during the entire cyclone processe are obtained. Properties of the high frequency spectral tail are discussed, using average frequency and peak frequency as the cut-off frequency parameters under different cut-off coefficient conditions, respectively. We suggest reasonable values for the cut-off frequency parameter. Cyclone-generated 2D wave spectra in shallow water (at DWR location) are investigated, shoaling effects, 2D spectral pattern variations, swell and wind waves spectral evolution. Our study shows the invalidity of presently accepted spectral formulae, in describing cyclone-generated waves.
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Kinoshita, Ikuo, Toshihide Torige, and Minoru Yamada. "Uncertainty Quantification of the RELAP5 Interfacial Friction Model in the Rod Bundle Geometry." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-38114.
Повний текст джерелаАнотація:
An application of the Best Estimate Plus Uncertainty (BEPU) method is made to an analysis of the “Intentional depressurizaion of steam generator secondary side” which is an accident management procedure in a small-break loss-of-coolant accident (SBLOCA) with high pressure injection (HPI) system failure. RELAP5/MOD3.2 is used as the system analysis code. Interfacial friction in the core affects the two-phase mixture level and the distribution of the dispersed gas phase. This phenomenon is very important in terms of the influence its uncertainty has on the peak cladding temperature. The RELAP5/MOD3.2 code uses drift-velocity to describe the interfacial friction coefficients in vertical dispersed flow. The Chexal-Lellouche drift-flux correlation is used for the rod bundle geometry. In the present study, the RELAP5 model uncertainty was quantified regarding the interfacial friction coefficients in the rod bundle geometry by conducting numerical analyses of separate effect tests. As the separate effect tests, two-phase mixture level swell tests in the Thermal Hydraulic Test Facility (THTF) of the Oak Ridge National Laboratory (ORNL) were used. After considering applicability to the SBLOCA, tests were selected for which conditions of pressures and rod powers were similar to PWR plant conditions. A total of 55 data were used. The model uncertainty parameter was defined as a multiplier for the interfacial friction coefficient. Numerical analyses were performed by adjusting the multiplier so that the predicted void fractions agreed with the experimental measured data. The resultant distribution of the multipliers represented the model uncertainty. The mean, standard deviation, minimum and maximum values of this uncertainty distribution were 0.88, 0.55, 0.13 and 3.0, respectively.
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Mabuchi, Takuya, and Takashi Tokumasu. "Molecular Dynamics Study of Proton and Water Transport in Nafion Membrane." In ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icnmm2013-73084.
Повний текст джерелаАнотація:
Polymer electrolyte fuel cells (PEFCs) are highly expected as a next-generation power supply system due to the purity of its exhaust gas, its high power density and high efficiency. The polymer electrolyte membrane is a critical component for the performance of the PEFCs and it is important to understand the nanostructure in the membrane to enhance proton transport. We have performed an atomistic analysis of the vehicular transport of hydronium ions and water molecules in the nanostructure of hydrated Nafion membrane by systematically changing the hydration level which provides insights into a connection between the nanoscopic and mesoscopic structure of ion clusters and the dynamics of hydronium ions and water molecules in the hydrated Nafion membrane. In this study, classical molecular dynamics simulations are implemented using a model of Nafion membrane which is based on DREIDING force field and newly modified and validated by comparing the density, water diffusivity, and Nafion morphology with experimental data. The simulated final density after the annealing procedure agrees with experiment within 1.3 % for various water contents and the trends that density decreases with increasing hydration level are reproduced. In addition to determination of diffusion coefficients of solvent molecules as a function of hydration level (from λ = 1 up to λ = 18), we have also calculated radial distribution functions and static structure factors not only to clarify the structure of water molecules and hydronium ions around the first solvation shell of sulfonate groups but also to validate the mesoscopic periodic structure among water clusters. The diffusion coefficient of water molecules increases with increasing hydration level and is found to be in good agreement with experimental data. The diffusion coefficient of hydronium ions has showed that general trends in the experimental data are reproduced by the simulations although the classical models have the limitation of probing hydronium dynamics. The static structure factors of liquid molecules at low wave length provide insights into the periodic structure of the inter-water clusters. These results are consistent with the Gebel’s model based on small-angle X-ray scattering that considers the dry membrane to be made of isolated spherical ionic clusters of radius ∼7.5 Å that swell with increasing hydration.
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Stellrecht, Eric, Bongtae Han, and Michael Pecht. "Measurement of Hygroscopic Swelling in Mold Compounds and Its Effect on PEM Reliability." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35252.
Повний текст джерелаАнотація:
Hygroscopic stresses arise in a plastic encapsulated microcircuit (PEM) when the mold compound swells upon absorbing moisture and the lead frame, die paddle, and silicon die, do not experience swelling. Similar to the thermal stress produced by the mismatch of coefficients of thermal expansion between adjacent materials, the hygroscopic stress increases as the hygroscopic swelling coefficient of the mold compound increases. Accurate measurement of hygroscopic swelling is essential in assessing the effect of hygroscopic stresses on package reliability. In this paper, a whole-field experimental method to characterize the hygroscopic swelling of mold compounds is proposed. The method is implemented to determine the hygroscopic swelling and the corresponding coefficient of hygroscopic contraction of five commercial molding compounds. A comparison between the hygroscopic and thermally induced mismatch strains in PEMs is presented and its implication on PEMs reliability is discussed.
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Sadek, Samir Hassan, and Mehmet Yildiz. "Numerical Simulation of Die Swell of Second-Order Fluids Using Smoothed Particle Hydrodynamics." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39215.
Повний текст джерелаАнотація:
This work presents the development of both weakly compressible and incompressible Smoothed Particle Hydrodynamics (SPH) models for simulating two-dimensional transient viscoelastic free surface flow which has extensive applications in polymer processing industries. As an illustration with industrial significance, we have chosen to model the extrudate swell of a second-order polymeric fluid. The extrudate or die swell is a phenomenon that takes place during the extrusion of polymeric fluids. When a polymeric fluid is forced through a die to give a polymer its desired shape, due to its viscoelastic non-Newtonian nature, it shows a tendency to swell or contract at the die exit depending on its rheological parameters. The die swell phenomenon is a typical example of a free surface problem where the free surface is formed at the die exit after the polymeric fluid has been extruded. The swelling process leads to an undesired increase in the dimensions of the extrudate. To be able to obtain a near-net shape product, the flow in the extrusion process should be well-understood to shed some light on the important process parameters behind the swelling phenomenon. To this end, a systematic study has been carried out to compare constitutive models proposed in literature for second-order fluids in terms of their ability to capture the physics behind the swelling phenomenon. The effect of various process and rheological parameters on the die swell such as the extrusion velocity, normal stress coefficients, and Reynolds and Deborah numbers have also been investigated. The models developed here can predict both swelling and contraction of the extrudate successfully. The die swell problem was solved for a wide range of Deborah numbers and for two different Re numbers. The numerical model was validated through the solution of fully developed Newtonian and Non-Newtonian viscoelastic flows in a two-dimensional channel, and the results of these two benchmark problems were compared with analytic solutions, and good agreements were obtained.
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Stosic, Zoran V., and Vladimir D. Stevanovic. "Three-Dimensional Numerical Simulation of Burnout on Horizontal Surface in Pool Boiling." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45521.
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Prediction of nucleate boiling mechanisms and burnout conditions, when heat transfer coefficient sharply drops and the heating surface destruction could occur are one of the crucial topics in thermal design and safety analyses of various thermal equipment. Although these phenomena have been intensively investigated for decades, various influencing factors and complexity of coupled thermal and fluid dynamic processes have not yet been fully understood. The integral approach towards prediction of nucleate boiling and burnout conditions requires modelling and numerical simulation of micro level phenomena of bubble rise and departure at a numbers of nucleation sites, as well as macroscopic two-phase mixture behaviour on the heating surface. In this paper multidimensional numerical simulation of the atmospheric saturated pool boiling is performed under high heat fluxes, near to and at the occurrence of burnout conditions. Micro level phenomena on the heating surface are modelled with the key parameters of vapour generation on the heating wall, such as bubble nucleation site density, bubble residence time on the heating wall and certain level of randomness in the location of bubble nucleation. Heat flux is non-uniformly distributed on the heating surface with peaks at the nucleation sites. The nucleation sites are determined by a random function, while the mean number of nucleation sites is prescribed according to the material characteristics and roughness of the heating surface. The applied numerical grids are able to represent the nucleation sites on the heating wall for both fresh (polished) and aged (rough) heaters at the atmospheric pool boiling conditions. The macro level phenomena are modelled with two-fluid model of liquid-vapour flow. The interfacial drag is modelled with appropriate closure laws. The applied modelling and numerical methods enable full representation of the two-phase mixture behaviour on the heating surface with inclusion of the swell level prediction. In this way the integral conditions of nucleate pool boiling with the possibility of burnout are simulated and the critical heat flux conditions are predicted. The result of the three-dimensional numerical simulations and analyses are presented as the extension of the previously published two-dimensional numerical results. Here presented three-dimensional investigation is performed in order to take into account more realistically spatial effects of vapour generation and two-phase flow, such as phase dispersion within the two-phase mixture, than it was able with previously performed two-dimensional investigation. Results are presented for short time period after the initiation of heat supply and vapour generation on the heating surface, as well as for quasi steady-state conditions after several seconds from pool boiling initiation. A replenishment of the heating surface with water and partial surface wetting for lower heat fluxes is shown, while heating surface dry-out is observed for high heat fluxes. The influence of the density of nucleation sites and the bubble residence time on the wall on the pool boiling dynamics is investigated. Also, the influence of the heat flux intensity on the pool boiling dynamics is analysed. Numerical simulations show that decrease of the density of nucleation sites and increase of bubble residence time on the heating surface (characteristics pertinent to fresh-polished heaters) lead to the reduction of critical heat flux values. Obtained results are in excellent agreement with the recent experimental investigations of the upward facing burnout conditions on the horizontal heated plate. Details of the developed numerical procedure are presented. The introduced method of random spatial and temporal generation of the vapour at the heated wall is a new approach. It enables the macroscopic representation of the population of microscopic vapour bubbles, which are generated at nucleation sites on the heater wall, and which burst through liquid micro-layer in thermal-hydraulic conditions close to the burnout. The applied numerical and modelling method has shown robustness by allowing stable calculations for wide ranges of applied modelling boiling parameters (density of nucleation sites and bubble residence time).
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Lin, Yu, Ghassan El Chahal, and Yanlin Shao. "Caisson Breakwater for LNG and Bulk Terminals: A Study on Limiting Wave Conditions for Caisson Installation." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-19081.
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Abstract As the worldwide oil and gas market continues to grow and environmental concerns with respect to in-port offloading of gas have increased, there has been a boom of interest in new liquefied natural gas LNG terminals in the past years. Loading - offloading operations at LNG and bulk terminals are generally protected by a breakwater to ensure high operability. For these terminals, caisson breakwaters are generally a preferred solution in water depth larger than 15 m due to its advantages compared to rubble mound breakwaters. The caisson installation is generally planned to be carried out in the period where sea conditions are relatively calm. However, many of these terminal locations are exposed to swell conditions, making the installation particularly challenging and subject to large downtime. There is no clear guidance on the caisson installation process rather than contractors’ experiences from different projects/sites. Therefore, studies are required in order to provide general guidance on the range of acceptable wave conditions for the installation operations and to have a better understanding of the influence of the caisson geometry. This paper presents a numerical study to determine the limiting wave conditions for caisson installing operations at larger water depth of 30–35 m for a confidential project along the African coast. Three caisson sizes/geometries are considered in order to assess and compare the wave-structure hydrodynamic interaction. The linear frequency-domain hydrodynamic analysis is performed for various seastates to determine the limiting wave conditions. Viscous effects due to flow separation at the sharp edges of the caisson are considered by using a stochastic linearization approach, where empirical drag coefficients are used as inputs. Parametric studies on caisson size and mooring stiffness are also presented, which can be used as a basis for future optimization. The uncertainty in the applied empirical viscous drag coefficients taken from the literature is examined by using a range of different drag coefficients. Further, the use of clearance-independent hydrodynamic coefficients (e.g. added mass and damping) may be questionable when the caisson is very close to the seabed, due to a possible strong interaction between caisson bottom and seabed. This effect is also checked quantitatively by a simplified approach. The findings of the study are presented in the form of curves and generalized to be used by designers and contractors for general guidance in future projects.
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Bachynski, Erin E., Yin L. Young, and Ronald W. Yeung. "Analysis and Dynamic Scaling of Tethered Wave Energy Converters in Irregular Waves." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49684.
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Wave energy converters (WECs) are a technically and economically promising option for renewable electricity generation. This paper investigates the hydrodynamic characteristics of a tethered cylindrical wave energy absorber using analytical methods and derives the scaling relations for laboratory testing. The effects of the cylinder geometry, mooring system, and mass distribution on the idealized power takeoff and the pitch motions of a tethered point wave energy absorber in irregular seas are summarized. Analytical solutions for the hydrodynamic coefficients and wave forcing are based on potential flow formulations and eigenfunction expansions. The results show that a relatively light mooring system has little effect on the power takeoff, but introduces a low-frequency coupled pitch-surge resonance that can cause system failure in long period swells. While analytical solutions provide first-order estimates of the system response, laboratory experiments are required to evaluate the nonlinear, coupled system response. In order to design and interpret such experiments, appropriate scaling relationships are determined and validated using numerical simulations. The added mass, radiation damping, wave radiation and diffraction excitation forces, and mooring system mass and stiffness are found to be self-consistent using geometric and Froude number similarity. The effects of incomplete geometric similarity with a shallow wave tank and viscous forces are also discussed.
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Auburtin, Erwan, Quentin Delivré, Jason McConochie, Jim Brown, and Yuriy Drobyshevski. "Numerical Towing Model for LNG Carrier Approach in Exposed Environment Calibrated With Full-Scale Measurements and Operability Criterion." In ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/omae2021-62279.
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Abstract The Prelude Floating Liquefied Natural Gas (FLNG) platform is designed to offload liquefied natural and petroleum gas products to carrier vessels moored in a Side-by-Side (SBS) configuration. Prior to the mooring operation, the carrier vessel is escorted and held alongside the FLNG with the assistance of tugs connected to her bow and stern to ensure sufficient control over the vessel in this critical phase. In order to better understand the impact of environmental conditions, to determine the optimum length, strength, material and configuration of the towline stretcher, and to estimate the maximum operable environments, coupled multi-body simulations have been performed in time domain. The numerical model, which considered both the LNG carrier and the forward tug, was calibrated using full-scale measurements of tug motions and tow line tension recorded during a real approach and berthing manoeuvre at Prelude FLNG. The measured environment effects were generated numerically and the model parameters were adjusted to reproduce the recorded behavior as accurately as possible. Since actions of the tug master are difficult to model numerically and only the statistical environment parameters are known, a simplified approach has been adopted for modelling the tug propulsion and steering using a combination of static forces, stiffness and linear and quadratic damping for relevant horizontal degrees of freedom. The calibrated numerical model was first subjected to several sensitivity assessments of the modelling level (single- or multi-body, inclusion of second-order wave loads, inclusion of forward speed). Then sensitivity studies were performed to help address operational requirements related to the wave height and direction, and the stretcher length and strength. The conclusions have been taken into consideration for the selection of the tow line configurations for future operations. Finally, the calibrated coupled LNG carrier and tug model was used to derive Prelude-specific tug operability criteria that may be used for decision-making based on weather forecasts, prior to the SBS offloading operations. A large matrix of swell and wind driven waves was simulated over a range of wave heights, periods, directions and static towing forces to allow a criterion to be developed based on a stochastic extreme tow line tension. Such criterion considers relevant wave parameters while remaining simplified enough for easy use in operations. This paper describes the assumptions and process to numerically model the towing configuration and calibrate the different coefficients, discusses the results obtained for the various sensitivities, and explains the operability criteria. Important conclusions and lessons learnt are also shared.