Relevant bibliographies by topics / Void coefficient

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers
  5. Reports

Academic literature on the topic 'Void coefficient'

Author: Grafiati
Published: 4 June 2021
Last updated: 13 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Void coefficient.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Void coefficient"

1

Hayashi, Takahiro, Takayuki Kobayashi, and Jun Takahashi. "Quantification of the void content of composite materials using soft X-ray transmittance." Journal of Thermoplastic Composite Materials 30, no. 11 (April 24, 2016): 1522–40. http://dx.doi.org/10.1177/0892705716644670.

Full text
Abstract:
Carbon fiber reinforced thermoplastics (CFRTPs) have high potential in high-cycle (1 min) molding as a weight-reducing material for the mass production of automobile components. However, residual voids in CFRTPs lead to diminished and unstable mechanical properties; therefore, the effective quantification of the void content in CFRTP products is necessary for developing an affordable system for mass production. In a previous study, we demonstrated that the X-ray attenuation coefficient decreases with increasing void content; thus, measurements of X-ray attenuation coefficients can be used to estimate the void contents of CFRTPs. In this study, we first investigated in detail the soft X-ray attenuation coefficients of completely impregnated composite materials with three different thicknesses; we observed that the attenuation coefficients decreased with increasing composite thickness, even though they should be independent of the thickness according to the Beer–Lambert law. We next demonstrated that although no correlation exists between the X-ray transmittance and the apparent attenuation coefficient of six composites with various void contents, the true attenuation coefficient modified to account for void content exhibits a good linear relationship with the X-ray transmittance, same as fully impregnated composites. Using the approximation line between the X-ray transmittance and the modified attenuation coefficient of CFRTP, we estimated the void content on the basis of the difference between the apparent and true X-ray attenuation coefficients. The average difference in void content determined by conventional hydrostatic weighing and that determined by the proposed X-ray transmittance method was 0.43%. We therefore concluded that the void content of CFRTPs of any thickness can be estimated nondestructively using soft X-rays.
APA, Harvard, Vancouver, ISO, and other styles
2

Zhang, Yu, Tielin Chen, Yujun Zhang, and Weizhong Ren. "Calculation Methods of Seepage Coefficient for Clay Based on the Permeation Mechanism." Advances in Civil Engineering 2019 (March 3, 2019): 1–9. http://dx.doi.org/10.1155/2019/6034526.

Full text
Abstract:
The existing empirical methods of the seepage coefficient for clay have difficulty in parameter acquisition and are poor in calculation accuracy, and it is possible to find reasonable ones based on the mature empirical methods of coarse-grained soil. Firstly, the permeation mechanism of clay was analysed including influencing factors, spatial process, and parameter calculation, and the ineffective and effective voids were defined; then the empirical methods of clay and coarse-grained soil were summarised and listed. Secondly, clay was put equivalent to coarse-grained soil according to bound-water consolidation, and the parameter “equivalent void ratio” was introduced to establish the equivalent calculation methods. Finally, the liquid-plastic limit method determining the volume of ineffective voids was explained, and the feasibility of equivalent calculation methods was evaluated by three examples. The results show that seepage, permeation, and effective permeation are three different concepts; groundwater permeates in clay via the effective void. For certain soil, the increasing sequence of permeability coefficients is the seepage coefficient, permeation coefficient, and effective permeation coefficient. Introduction of the “equivalent void ratio” unifies the calculation of the seepage coefficient for clay and coarse-grained soil. The maximum of the bound-water content is about 0.9 time the size of liquid limit. The Mesri equation and the equivalent calculation method of Terzaghi or Curson–Karman are suitable for calculating the seepage coefficient of clay for the closest results to experimental values.
APA, Harvard, Vancouver, ISO, and other styles
3

Mikheev, Alexander, Andrei Nazarov, Irina Ershova, and Alexander Zaluzhnyi. "Kinetics of Void Growth in Cubic Metals: Theory and Simulation." Defect and Diffusion Forum 363 (May 2015): 91–98. http://dx.doi.org/10.4028/www.scientific.net/ddf.363.91.

Full text
Abstract:
We examine the effect of elastic stresses induced by growing voids on the diffusion vacancy fluxes using newly derived equations. One of the main goals of our work is to obtain a kinetic equation for the growth rate of voids in cubic metals. The diffusion equation for vacancies, in which the influence of elastic stress near the void on the flux is taken into account, is linearized and solved. Then after mathematical transformations that are similar to Lifshitz - Slyozov theory, kinetic equations for the growth rate of the voids in fcc and bcc metals are obtained. The kinetic equations contain additional terms due to developed strain. This feature distinguishes the present equation from known ones and changes the kinetic of void growth. The functional dependence on strain is determined by coefficients, which characterize the strain influence on diffusion (SID coefficients). These coefficients are very sensitive to the atomic structure in the nearest vicinity of the saddle-point configuration. We have built an advanced model to evaluate them. SID coefficient simulation is the next step of this work. Using the kinetic equations and the SID coefficients, we calculate the void growth rate in cubic metals under different conditions.
APA, Harvard, Vancouver, ISO, and other styles
4

Lin, Li, Xiang Zhang, Jun Chen, and Xi Meng Li. "Numerical Investigations of Ultrasonic Scattering from Voids in Composite Materials Based on Random Void Model." Advanced Materials Research 346 (September 2011): 639–43. http://dx.doi.org/10.4028/www.scientific.net/amr.346.639.

Full text
Abstract:
Ultrasonic attenuation coefficient is firstly calculated utilizing the finite difference time domain method based on a novel 2-D RVM for carbon fiber reinforced plastic (CFRP) composite materials. The results show that the void morphology has detrimental effect on ultrasonic attenuation. Even at the fixed porosity, ultrasonic attenuation coefficient fluctuates due to the randomness of void morphology in CFRP composite materials. This work significantly helps to understand ultrasonic scattering mechanism of voids and formulation of CFRP composite material properties.
APA, Harvard, Vancouver, ISO, and other styles
5

Sun, Li Mei, Xia Liu, and Zhan Rong Zhang. "Correlation Analysis of Physical and Mechanical Soil Parameters in Coastal Plain Region." Applied Mechanics and Materials 438-439 (October 2013): 1181–84. http://dx.doi.org/10.4028/www.scientific.net/amm.438-439.1181.

Full text
Abstract:
According to the tested physical and mechanical soil parameters of the Coastal Railway in West Guangdong along the broad coastal plain region, the correlation relations between compression modulus, compression coefficient and void ratio, moisture content, density, standard penetration number are analyzed by the linear regression method. The results show that the compression modulus increases with the increase of water content and void ratio, with correlation coefficients being 0.6985 and 0.8147, respectively; the compression modulus decreases with the increase of density and standard penetration number, with correlation coefficients being 0.7827 and 0.4934, respectively; the compression coefficient decreases with the increase of water content and void ratio, with correlation coefficients being 0.9131 and 0.9412, respectively; the compression coefficient decreases with the increase of density and standard penetration number, with correlation coefficients being 0.8187 and 0.4985, respectively. The parameters which are hardly obtained from the test directly can be easily evaluated by using these formulas.
APA, Harvard, Vancouver, ISO, and other styles
6

Jones, M. K., M. F. Horstemeyer, and A. D. Belvin. "A Multiscale Analysis of Void Coalescence in Nickel." Journal of Engineering Materials and Technology 129, no. 1 (June 9, 2006): 94–104. http://dx.doi.org/10.1115/1.2400265.

Full text
Abstract:
An internal state variable void coalescence equation developed by Horstemeyer, Lathrop, Gokhale, and Dighe (2000, Theor. Appl. Fract. Mech., 33(1), pp. 31–47) that comprises void impingement and void sheet mechanisms is updated based on three-dimensional micromechanical simulations and novel experiments. This macroscale coalescence equation, developed originally from two-dimensional finite element simulations, was formulated to enhance void growth. In this study, three-dimensional micromechanical finite element simulations were employed using cylindrical and spherical void geometries in nickel that were validated by experiments. The number of voids, void orientation, and void spacing were all varied and tested and simulated under uniaxial loading conditions. The micromechanical results showed excellent agreement with experiments in terms of void volume fractions versus strain and local void geometry images. Perhaps more importantly, the macroscale internal state variable void coalescence equation did not require a functional form change but just a coefficient value modification.
APA, Harvard, Vancouver, ISO, and other styles
7

Gan, Deqing, Xi Yang, and Yunpeng Zhang. "Experimental Analysis on Permeability Characteristics of Iron Tailings." Mathematical Problems in Engineering 2019 (March 28, 2019): 1–11. http://dx.doi.org/10.1155/2019/6539846.

Full text
Abstract:
The permeability characteristics of iron tailings are one of the important factors affecting the stability of the tailings dam. The permeability properties of undisturbed iron tailings and disturbed iron tailings were analyzed from various aspects such as FC value, gradation, particle size, specific surface area, and interparticle void ratio with water head test in laboratory. The results show that the permeability coefficients of undisturbed iron tailings and disturbed iron tailings are affected by the fine particles content (FC). The threshold of fine content is about 40%. The traditional formulas for calculating the permeability coefficient are applied. But the results are inaccurate. The relationship between permeability coefficient of the iron tailings (undisturbed iron tailings and disturbed iron tailings) and the nonuniform coefficient (Cu), the curvature coefficient (Cc), the average particle size, the weighted average particle size, the specific surface area, and the skeleton void ratio (es) is nonlinear. It is difficult to characterize the change of permeability coefficient when the fine content is large. However, the relationship between permeability coefficient of the iron tailings (undisturbed iron tailings and disturbed iron tailings) and the effective particle size and silt particles void ratio (ef) is linear. A formula was developed for the determination of permeability coefficient of iron tailings by analyzing the effective particle size and silt particles void ratio. And it is more accurate. The permeability coefficients of disturbed samples are slightly larger than the permeability coefficients of undisturbed sample. This is due to the destruction of the sedimentary structure of the tailings and increasing e. Maybe the R in the new formula is affected by the structure of iron tailings. This requires further research.
APA, Harvard, Vancouver, ISO, and other styles
8

Slavickas, Andrius, Raimondas Pabarčius, Aurimas Tonkūnas, Gediminas Stankūnas, and Eugenijus Ušpuras. "Void Reactivity Coefficient Analysis during Void Fraction Changes in Innovative BWR Assemblies." Science and Technology of Nuclear Installations 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/757201.

Full text
Abstract:
The study of the void reactivity variation in innovative BWR fuel assemblies is presented in this paper. The innovative assemblies are loaded with high enrichment fresh UO2and MOX fuels. UO2fuel enrichment is increased above existing design limitations for LWR fuels (>5%). MOX fuel enrichment with fissile Pu content is established to achieve the same burnup level as that of high enrichment UO2fuel. For the numerical analysis, the TRITON functional module of SCALE 6.1 code with the 238-group ENDF/B-VI cross section data library was applied. The investigation of the void reactivity feedback is performed in the entire 0–100% void fraction range. Higher values of void reactivity coefficient for assembly loaded with MOX fuel are found in comparison with values for assembly loaded with UO2fuel. Moreover, coefficient values for MOX fuel are positive over 75% void fraction. The variation of the void reactivity coefficient is explained by the results of the decomposition analysis based on four-factor formula and neutron absorption reactions for main isotopes. Additionally, the impact of the moderation enhancement on the void reactivity coefficient was investigated for the innovative assembly with MOX fuel.
APA, Harvard, Vancouver, ISO, and other styles
9

Li, Wen Bo. "Study on the Permeability Characteristics of Coarse-Grained Soil and its Permeability Rule." Advanced Materials Research 904 (March 2014): 383–88. http://dx.doi.org/10.4028/www.scientific.net/amr.904.383.

Full text
Abstract:
The permeability of coarse-grained soil is influenced by many factors. The results of permeability tests in different conditions indicate the effects of coarse-grained soil dry density of , fines content P5,void ratio e and nonuniform coefficient Cu to the permeability coefficient. Analyzing the relationship between coarse-grained soil dry density , fines content P5, void ratio e, nonuniform coefficient Cu and permeability coefficient, thus there is a relational expression between coarse-grained soil dry density of soil , fines content P5, void ratio e, nonuniform coefficient Cu and permeability coefficient.
APA, Harvard, Vancouver, ISO, and other styles
10

Kim, Nam Ho, and Ho Sung Kim. "Statistical Characteristics of Inter-Particle/Void Distance for Particulate Composites." Key Engineering Materials 312 (June 2006): 105–10. http://dx.doi.org/10.4028/www.scientific.net/kem.312.105.

Full text
Abstract:
Two dimensional statistical characteristics of inter particle/void distance (ID) for various particle/void and dispersion types are studied in relation with toughening of plastics using computer generated three dimensional models. Particle/void size groups adopted were of log-normal distribution. Particles/voids were dispersed at uniform-random. It was found that IDs are (a) of approximately Gaussian distribution but; (b) not of Gaussian distribution for particle/void sizes of bimodal log-normal distribution (created by mixing of two groups of articles/voids). It was also found that the degree of ID uniformity, which can be represented by the inverse of the coefficient of variation, for a single group of log-normally sized particles/voids is not sensitive to standard deviation of particle/void size. Mixing effect on ID characteristics using two groups of log-normally distributed particles/voids with similar mean particle/void diameters was simulated. It was found that, when a significant amount (36 vol %) of particles/voids of a small mean and standard deviation of ID, was mixed with a group of particles/voids of a large mean and standard deviation of ID, mean and standard deviation of ID for the mixture were not substantially lower than those of the group of particles/voids of the large mean and standard deviation of ID. It was also found that the degree of ID uniformity for the mixture of the two groups were lower than those of individual groups, indicating that the mixing has deleterious effect on toughening.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "Void coefficient"

1

Kassem, Emad Abdel-Rahman. "Measurements of moisture suction in hot mix asphalt mixes." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4259.

Full text
Abstract:
The presence of moisture in hot mix asphalt (HMA) causes loss of strength and durability of the mix, which is referred to as moisture damage. This study deals with the development of experimental methods for measuring total suction in HMA, which can be defined as the free energy state of water in HMA mixes. The total suction is related to the ability of moisture to get into the mix under unsaturated conditions; it is also related to the ability of the mix to retain moisture. Soil suction has been studied extensively. However, suction in HMA as a porous material and its relationship to moisture damage have not been studied. The development of a procedure to measure the total suction in HMA mixes is the first objective of this research. The second objective is to relate suction measurements to physical and chemical properties of the mixtures. The objectives were achieved in two phases. In the first phase, the total suction was measured in HMA specimens with different types of aggregates (limestone and granite), and with different air void distributions and aggregate gradations. The results of this phase showed that the drying test using a 60 oC temperature-controlled room is the proper setup for measuring the total suction in HMA using thermocouple psychrometers. The characteristics of suction-moisture content curves were found to be related to the air void distribution in HMA. In the second phase, total suction was measured in sand asphalt specimens. These specimens had different combinations of aggregates and binders with different bond energies and exhibited different field performance in terms of resistance to moisture damage. The suction measurements in sand asphalt specimens were used to calculate the moisture diffusion coefficient. The results revealed that water diffused into sand asphalt specimens that are known to have poor resistance to moisture damage faster than those that are known to have good resistance to moisture damage
APA, Harvard, Vancouver, ISO, and other styles
2

Song, Kyle. "Development of a Fast X-ray Line Detector System for Two-Phase Flow Measurement." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/77503.

Full text
Abstract:
Measuring void fraction distribution in two-phase flow has been a challenging task for many decades because of its complex and fast-changing interfacial structure. In this study, a non-intrusive X-ray measurement system is developed and calibrated to mitigate this challenge. This approach has several advantages over the conventional methods such as the multi-sensor conductivity probe, wire-mesh sensor, impedance void meter, or direct optical imaging. The X-ray densitometry technique is non-intrusive, insensitive to flow regime changes, capable of measuring high temperature or high-pressure flows, and has reasonable penetration depth. With the advancement of detector technology, the system developed in this work can further achieve high spatial resolution (100 micron per pixel) and high temporal resolution (1000 frames per second). This work mainly focuses on the following aspects of the system development: establishing a geometrical model for the line detector system, conducting spectral analysis for X-ray attenuation in two-phase flow, and performing calibration tests. The geometrical model has considered the measurement plane, geometry of the test-section wall and flow channel, relative position of the X-ray source and detector pixels. By assuming axisymmetry, an algorithm has been developed to convert void fraction distribution along the detector pixels to the radial void profile in a circular pipe. The X-ray spectral analysis yielded a novel prediction model for non-chromatic X-rays and non-uniform structure materials such as the internal two-phase flow which contains gas, liquid and solid wall materials. A calibration experiment has been carried out to optimize the detector conversion factor for each detector pixels. Finally, the data measured by the developed X-ray system are compared with the double-sensor conductivity probe and gas flow meter for sample bubbly flow and slug flow conditions. The results show reasonable agreement between these different measuring techniques.
Master of Science
APA, Harvard, Vancouver, ISO, and other styles
3

Aloui, Fethi. "Étude des écoulements monophasiques et diphasiques dans les élargissements brusques axisymétrique et bidimensionnel." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL055N.

Full text
Abstract:
Ce travail traite d'une étude théorique et expérimentale sur les écoulements monophasiques et diphasiques (à bulles) dans les élargissements brusques. Deux configurations d'élargissement ont été étudiées: l'une est axisymétrique verticale et l'autre bidimensionnelle horizontale. À travers ces singularités, une approche globale qui détermine la chute de pression singulière a été développée, et une étude expérimentale a été réalisée sur la dynamique des phases liquide et gazeuse. Dans l'élargissement brusque vertical axisymétrique, l'écoulement est symétrique. Les grandeurs mesurées concernent la vitesse axiale du liquide en écoulement monophasique et le taux de vide, la vitesse axiale des bulles et la granulométrie des bulles en écoulement diphasique. Au voisinage immédiat de la singularité, ces résultats expérimentaux locaux ont permis de donner la tendance générale de la réorganisation de l'écoulement monophasique et diphasique. Pour l'élargissement brusque bidimensionnel horizontal, la visualisation de l'écoulement a joué un rôle important dans la compréhension des phénomènes de transition d'un écoulement complètement dissymétrique vers un écoulement symétrique. En écoulement monophasique, l'étude expérimentale a concerné la pression et la vitesse axiale du liquide mesurée par un film chaud. Dans cet écoulement, la dissymétrie de l'écoulement n'a pas de cote préférentiel pour son orientation. En écoulement diphasique, la transition vers un écoulement symétrique se fait par augmentation progressive du débit de gaz pour un débit de liquide fixe. Les résultats expérimentaux relatifs à ce type de singularité en écoulement à bulles concernent le taux de vide, les vitesses axiales de chacune des phases et la granulométrie des bulles. Ces grandeurs nous ont permis de décrire d'une part les structures locales de l'écoulement diphasique et d'autre part de vérifier ce qui a été obtenu par la visualisation
APA, Harvard, Vancouver, ISO, and other styles
4

Busset, Julie. "Inversion acoustique articulatoire à partir de coefficients cepstraux." Phd thesis, Université de Lorraine, 2013. http://tel.archives-ouvertes.fr/tel-00838913.

Full text
Abstract:
L'inversion acoustique-articulatoire de la parole consiste à récupérer la forme du conduit vocal à partir d'un signal de parole. Ce problème est abordé à l'aide d'une méthode d'analyse par synthèse reposant sur un modèle physique de production de la parole contrôlé par un petit nombre de paramètres décrivant la forme du conduit vocal : l'ouverture de la mâchoire, la forme et la position de la langue et la position des lèvres et du larynx. Afin de s'approcher de la géométrie de notre locuteur, le modèle articulatoire est construit à l'aide de contours articulatoires issus d'images cinéradiographiques présentant une vue sagittale du conduit vocal. Ce synthétiseur articulatoire nous permet de créer une table formée de couples associant un vecteur articulatoire au vecteur acoustique correspondant. Nous n'utiliserons pas les formants (fréquences de résonance du conduit vocal) comme vecteur acoustique car leur extraction n'est pas toujours fiable provoquant des erreurs lors de l'inversion. Les coefficients cepstraux sont utilisés comme vecteur acoustique. De plus, l'effet de la source et les disparités entre le conduit vocal du locuteur et le modèle articulatoire sont pris en compte explicitement en comparant les spectres naturels à ceux produits par le synthétiseur car nous disposons des deux signaux.
APA, Harvard, Vancouver, ISO, and other styles
5

Hásová, Eva. "Využiti ozonu při čistění odpadních vod." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216450.

Full text
Abstract:
Diploma thesis will be dealt with the utilization of ozone wastewater treatment. Experimental part will be focused on study of ozone utilization in two different reactors (bubble column, jet loop reactor). Reactors will be compared by overall mass transfer coefficient and saturation concentration. Ozonization will be applied because of biological resistent and toxic compound 2-mercaptobenzothiazole disposal. Changes of biological decomposition will be measured and assessed by respirometric measurements.
APA, Harvard, Vancouver, ISO, and other styles
6

Sklar, Alexander Gabriel. "Channel Modeling Applied to Robust Automatic Speech Recognition." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_theses/87.

Full text
Abstract:
In automatic speech recognition systems (ASRs), training is a critical phase to the system?s success. Communication media, either analog (such as analog landline phones) or digital (VoIP) distort the speaker?s speech signal often in very complex ways: linear distortion occurs in all channels, either in the magnitude or phase spectrum. Non-linear but time-invariant distortion will always appear in all real systems. In digital systems we also have network effects which will produce packet losses and delays and repeated packets. Finally, one cannot really assert what path a signal will take, and so having error or distortion in between is almost a certainty. The channel introduces an acoustical mismatch between the speaker's signal and the trained data in the ASR, which results in poor recognition performance. The approach so far, has been to try to undo the havoc produced by the channels, i.e. compensate for the channel's behavior. In this thesis, we try to characterize the effects of different transmission media and use that as an inexpensive and repeatable way to train ASR systems.
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Void coefficient"

1

Kobranova, V. N. "Effective and Dynamic Porosity. Voids Ratio and Moisture Capacity Coefficient." In Petrophysics / ПЕТРОФИЗИКА, 45–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-662-09244-6_5.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Azimova, Tarana. "Challenges in Estimation of Beta." In Advances in Business Information Systems and Analytics, 79–98. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1086-5.ch005.

Full text
Abstract:
Capital asset pricing model (CAPM) brings deep intuitive understanding of the relationship between expected return and risk. Unfortunately, the empirical record of the CAPM has not been satisfactory since its commencement. The empirical testing of CAPM is void in most cases due to the use of an inefficient index as a proxy for market portfolio. Plausible tests require a well-diversified market portfolio which so far has been unfeasible to obtain. Lack of validity in empirical records has been caused by complexity in exerting valid estimations of the beta coefficient. This chapter judges which of the indices provides investors the best beta forecast and questions which time period should be selected for beta calculation. This chapter reveals that the choice of return intervals causes variations in beta estimation of the security. Applying higher frequency has an advantage in that it increases the number of observations, but a shortfall is that beta tends to have substantial bias with shorter return intervals used.
APA, Harvard, Vancouver, ISO, and other styles
3

"Main Characteristics of an Aquifer The main function of the aquifer is to provide underground storage for the retention and release of gravitational water. Aquifers can be characterized by indices that reflect their ability to recover moisture held in pores in the earth (only the large pores give up their water easily). These indices are related to the volume of exploitable water. Other aquifer characteristics include: • Effective porosity corresponds to the ratio of the volume of “gravitational” water at saturation, which is released under the effect of gravity, to the total volume of the medium containing this water. It generally varies between 0.1% and 30%. Effective porosity is a parameter determined in the laboratory or in the field. • Storage coefficient is the ratio of the water volume released or stored, per unit of area of the aquifer, to the corresponding variations in hydraulic head 'h. The storage coefficient is used to characterize the volume of useable water more precisely, and governs the storage of gravitational water in the reservoir voids. This coefficient is extremely low for confined groundwater; in fact, it represents the degree of the water compression. • Hydraulic conductivity at saturation relates to Darcy’s law and characterizes the effect of resistance to flow due to friction forces. These forces are a function of the characteristics of the soil matrix, and of the fluid viscosity. It is determined in the laboratory or directly in the field by a pumping test. • Transmissivity is the discharge of water that flows from an aquifer per unit width under the effect of a unit of hydraulic gradient. It is equal to the product of the saturation hydraulic conductivity and of the thickness (height) of the groundwater. • Diffusivity characterizes the speed of the aquifer response to a disturbance: (variations in the water level of a river or the groundwater, pumping). It is expressed by the ratio between the transmissivity and the storage coefficient. Effective and Fictitious Flow Velocity: Groundwater Discharge As we saw earlier in this chapter, water flow through permeable layers in saturated zones is governed by Darcy’s Law. The flow velocity is in reality the fictitious velocity of the water flowing through the total flow section. Bearing in mind that a section is not necessarily representative of the entire soil mass, Figure 7.7 illustrates how flow does not follow a straight path through a section; in fact, the water flows much more rapidly through the available pathways (the tortuosity effect). The groundwater discharge Q is the volume of water per unit of time that flows through a cross-section of aquifer under the effect of a given hydraulic gradient. The discharge of a groundwater aquifer through a specified soil section can be expressed by the equation:." In Hydrology, 229–30. CRC Press, 2010. http://dx.doi.org/10.1201/b10426-57.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Void coefficient"

1

Li, Dan, Changhong Peng, and Yun Guo. "Numerical Analysis of Heat Transfer Characteristics of External Cooling Channel of the Lower Head." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81410.

Full text
Abstract:
The heat transfer coefficient of the curved surface reflects the external cooling capacity of the reactor pressure vessel under serious accident. This topic used Ansys fluent software 14.5 as simulation tool, mesh generation of the flow area is carried out after the geometric model of the lower head, and then the heat transfer coefficient of the curved surface is numerically simulated. In this paper, the heat transfer coefficient formulas are fitted according to the laminar and turbulent flow, and the influence of the cavity on the heat transfer coefficient is discussed. Calculation results show that, for single-phase flow both laminar and turbulent flow, the heat transfer coefficients increase with the increase of Re, and increase with the increase of Pr, decrease with the increase of theta; According to the comparison of the heat transfer coefficients under different radii of curved surfaces, reducing the radius is beneficial to increase the heat transfer capability; In subcooled boiling flow, the void fraction is less than 21%, the heat transfer coefficient increases with the increases of the void fraction, the void fraction is conducive to heat transfer; but when the void fraction is higher than 21%, it is opposite.
APA, Harvard, Vancouver, ISO, and other styles
2

Ghanbarzadeh, S., P. Hanafizadeh, and M. H. Saidi. "Time-Average Drag Coefficient and Void Fraction in Gas-Liquid Two Phase Flow." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78220.

Full text
Abstract:
Two-phase flow simulations around a body were not studied before and considering these flows can play a significant role in long-term reliability and safety of industrial systems. In this paper, flow regimes, drag coefficient and void fraction around different cross-section prisms were considered. To achieve this aim, main equations of flow have been developed for investigation of drag coefficient in air-water two phase. Our numerical analyses were performed by a designed and written CFD package which is based on Eulerian-Eulerian approach. Geometries, which have been studied in this article, are: circle, rectangle and triangle, for different aspect ratio (length over width) and leading edge angle, respectively. Other parameters such as two phase Reynolds number, free stream void fraction and bubble size were considered, too. Drag coefficient is closely related to the turbulence and the bubble motion. Since these mechanisms vary over time, we used the time-average value of drag coefficient. Furthermore, some attempts were done to investigate flow field, void fraction distribution and especially wake region around the cylinders by an image processing scheme in an upward air-water bubbly flow. The results showed that drag coefficient strongly dependent upon Reynolds number. Numerical results were compared with available empirical correlations and experimental works of Yokosawa et al [1].
APA, Harvard, Vancouver, ISO, and other styles
3

Miyazaki, Takeru, Misaki Baba, Hideki Murakawa, Hitoshi Asano, Katsumi Sugimoto, and Daisuke Ito. "Two-Phase Flow Behavior and Heat Transfer Characteristics in Kettle Reboiler." In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3293.

Full text
Abstract:
Effects of the tube array, such as in-line and staggered, on void-fraction distribution and heat transfer coefficient around a tube were experimentally investigated. The test section was vertical duct with inner size of 90 × 90 mm2. Diameter of the tubes was 15 mm, and the pitch-to-diameter ratio was 1.5 for both tube bundles. Working fluids were air and water. Experiments were carried out at superficial gas velocity defined at minimum area section, Jg, of 0.10 to 0.89 m/s, superficial liquid velocity, Jl, of 0.1 to 0.3 m/s, under the atmospheric condition. Measurements of void-fraction distribution were carried out using X-ray radiography. In addition, heat transfer coefficient around a tube was measured and the heat transfer coefficients in association with the flow regime and the void-fraction distribution were evaluated. Time-average void-fraction was higher around upstream of a tube than that of downstream at bubbly flow condition for both bundles. Under intermittent flow condition, time-average void fraction at the maximum gap were higher than that around the other points in both tube bundles. For in-line tube bundle, enhancement of the heat transfer clearly appeared between ±90 to 180°. For staggered tube bundle, the heat transfer increased all over the pipe.
APA, Harvard, Vancouver, ISO, and other styles
4

Sim, W. G., and W. Mureithi Njuki. "Drag Coefficient and Two-Phase Friction Multiplier on Tube Bundles Subjected to Two-Phase Cross-Flow." In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25073.

Full text
Abstract:
An approximate analytical model for upward two-phase cross-flow through horizontal bundles, to predict drag coefficient on a cylinder and two-phase Euler number, has been developed. To verify the model, two sets of experiments were performed for various pitch mass fluxes of air-water mixture with void fraction. The experiments were undertaken with rotated triangular array of cylinders. The pitch to diameter ratio is 1.5 and the cylinder diameter 38 mm. The void fraction model proposed by Feenstra et al. (2000) is utilized to estimate the void fraction for the cross-flow in the tube bundle. An important variable on the drag coefficient is the two-phase friction multiplier. An empirical formulation of non dimensional pressure drop (Euler number) for single phase flow in tube bundles was proposed by Zukauskas et al. (1988) and two-phase friction multiplier in duct flow was formulated by various researchers. Considering the formulations, the present model was developed. It is found that Marchaterre’s model (1961) for two-phase friction multiplier is applicable to air-water mixtures. The analytical results agree well with experimental drag coefficients and Euler numbers in air-water mixtures for a sufficiently wide range of pitch mass fluxes and qualities. This model will allow researcher to provide analytical estimates of the drag coefficient, which is related to two-phase damping.
APA, Harvard, Vancouver, ISO, and other styles
5

Hanafizadeh, Pedram, S. Alireza Hojati, Hamid Eslami, and Navid Latifian. "High Reynolds Gas-Liquid Two Phase Flow Around a Triangular Body." In ASME 2014 12th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/esda2014-20061.

Full text
Abstract:
In many industrial applications, some measurement instruments must be placed in a pipe in which fluid flows. Two phase cross flows around a body have seldom been studied until now and considering these flows can play a significant role in long-term reliability and safety of industrial systems. In this paper drag coefficient, pressure coefficient and void fraction around triangular bodies with different leading edge angles were considered. Also effect of Reynolds number and inlet void fraction on drag coefficient and pressure coefficient has been investigated and flow treatment behind the triangular obstacle has been examined. To achieve this aim, main equations of flow have been developed for investigation of drag coefficient in air-water two phase. Our numerical analyses were performed by a designed and written CFD package which is based on Eulerian-Eulerian approach. Geometries, which have been studied in this article, are triangle, with different leading edge angle. Other parameters such as two phase Reynolds number, free stream void fraction and bubble size were considered, too. Drag coefficient is closely relates to the turbulence and the bubble motion. Since these mechanisms vary over time, we used final value of drag coefficient after convergence. The results showed that drag coefficient is strongly depended of Reynolds number. In this simulation it can be seen that both the drag coefficient and pressure drag coefficient decrease whit increase in two phase Reynolds number and increase with decrease in inlet void fraction.
APA, Harvard, Vancouver, ISO, and other styles
6

Raghu Kumar, G., C. P. Reddy, and V. Sathyamoorthy. "Effect of Pin and Subassembly Heterogenity in Sodium Void Worth Calculations." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29547.

Full text
Abstract:
Metal fuelled sodium cooled fast reactors are known to have high breeding ratio and short doubling time. Due to these features they play a very important role in the energy scenario, where higher power growth is required. Large sodium cooled fast reactors have positive sodium void coefficient, which is considered to be undesirable feature even though reactor safety can be established for all design based accidents like loss of flow and transient over power accidents. These types of fast reactors, which have harder neutron spectra are having higher sodium void coefficient compared to ceramic fuelled fast reactors. In many of the safety analysis the total sodium void is calculated and it is used in the safely evaluation. However the sodium in the metal fuelled reactor has got three parts, namely bonding sodium, coolant sodium and the sodium in the inter space of subassembly hexagonal cans. In the reactor accident scenario the behavior of these three components of sodium will be different and will effect the sequence of the accident. The finer details, of the fuel sub assembly, are modeled in to Monte Carlo code and the sodium void coefficient is calculated for each of the component for the fuel zones. This study will be helpful in improving safety of the reactor and also reducing the conservatism in the safely features.
APA, Harvard, Vancouver, ISO, and other styles
7

Zhu, Longxiang, and Jianqiang Shan. "Interfacial Drag Force Improvement in Two-Fluid Model." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81070.

Full text
Abstract:
Interfacial drag force, which indicates the momentum transfer between liquid phase and vapor phase, is a key constitutive equation in the two-fluid model. Based on the “drift-velocity approach” (utilized in RELAP5/MOD3) and the “drag coefficient approach” (utilized in RELAP5/MOD2 and CTF), three improvements are proposed, which are: 1) improved drag coefficient closure, 2) improved drag coefficient formulation approach, 3) improved bubble radius closure approach. The comparison among the two original approaches and the three improved approaches has been made with the ORNL experiment data in high pressure-low flow condition and the results have been discussed. Results indicates: 1) the EPRI correlation predicts the void fraction worse than the drag coefficient approaches; 2) the drag coefficient correlations in CTF predicts the void fraction better than improved drag coefficient formulation approach, which are the original equations in Ishii’s model; 3) the improved drag coefficient formulation approach predicts similarly with the original RELAP5/MOD2 correlations, though it gets rid of the dependence on interfacial area concentration; 4) improved bubble radius closure approach over-predicts the void fraction, however more experiment tests should be calculated before a conclusion is drawn.
APA, Harvard, Vancouver, ISO, and other styles
8

Olala, Stephen, Njuki W. Mureithi, Teguewinde Sawadogo, and Michel J. Pettigrew. "Streamwise Fluidelastic Forces in Tube Arrays Subjected to Two-Phase Flows." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28153.

Full text
Abstract:
Detailed unsteady fluid force and phase measurements for a single tube oscillating purely in the streamwise direction in a rotated triangular tube array subjected to air-water two-phase cross-flow have been conducted in this study for homogeneous void fractions between 0% and 90%. Additionally the streamwise steady forces were measured in two-phase flow at a Reynolds number (based on the pitch velocity), Re = 7.2 × 104. The results are compared to those previously obtained for transverse direction oscillations. The measurement results show that the magnitude of the force coefficients for both directions (drag and lift) is comparable both in trend and quantitatively. However, the phase in the drag direction is negative while that for the lift is positive. The range of variation of the phase is also significantly smaller for the drag direction. Noting that negative phase corresponds to positive damping and vice versa, this observation confirms previous findings of lack of instability in the drag direction for a single flexible tube in a rotated triangular tube array. The drag steady fluid force coefficients were found to increase with dimensionless displacement in the flow direction for the entire range of void fractions considered. The derivative of the measured steady fluid force coefficient, which is an important factor in fluidelastic instability study using the quasi-steady model, was found to remain positive in the drag direction. The effect of void fraction on the unsteady fluid force coefficient and other dynamic parameters such as hydrodynamic mass and damping are also discussed.
APA, Harvard, Vancouver, ISO, and other styles
9

Ren, Quan-yao, Zeng-ping Pu, Mei-yin Zheng, Min Su, Ping Chen, Liang-ming Pan, Hui He, and Qing-che He. "Experimental Study on the Sub-Channel Void Fraction Characteristics of Bubbly Flow in Rod Bundles." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16315.

Full text
Abstract:
Abstract The gas-liquid two-phase flow behaviors are always associated with its dynamic void fraction, such as flow resistance, heat transfer coefficient, phase distribution, critical heat flux etc. As regard to the commercial PWR and BWR, rod bundles are the typical geometry, which contains many sub-channels for coolant flowing. In present study, the sub-channel void fraction was measured in 5 × 5 rod bundles with the sub-channel impedance void meter consisting of 12 strip electrodes. Based on the measured void fraction in different sub-channels, the void fraction dynamics, PDF (probability distribution function) and CDF (cumulative distribution function) curves were analyzed to make clear the effect of superficial gas and liquid velocity, flow development and casing tube. The empirical correlation for PDF of dynamic sub-channel void fraction has been developed, which showed good fitness with PDF and CDF curves and satisfying accuracy of averaged void fraction.
APA, Harvard, Vancouver, ISO, and other styles
10

Béguin, C., É. Pelletier, and S. Étienne. "Void Fraction Effect on Added Mass in Bubbly Flow." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28460.

Full text
Abstract:
This paper proposes a relation for the added mass coefficient of spherical bubbles depending on void fraction based on results obtained by a semi-analytical method. This information is essential to completely characterize finely dispersed bubbly flows, where small spherical gas bubbles are present in a continuous liquid phase. Most of the closure relations for Euler-Euler or Euler-Lagrange models are obtained from experiments involving single bubbles. Their applicability to systems with high void fraction is therefore questionable. This paper uses solid harmonics to solve 3D potential flow around bubbles. Several configurations were calculated for different numbers of particles and spatial arrangements. Our results are compared with previous studies. Depending on the model proposed by previous authors, added mass forces could increase or decrease with the void fraction. This paper solves these discrepancies. The main purpose of this work is to develop simple formulas fitting our semi-analytical results. These simple formulas are suitable for further use, particularly as added mass models for multiphase flow averaged equations.
APA, Harvard, Vancouver, ISO, and other styles

Reports on the topic "Void coefficient"

1

Engle, W. W. Jr, and L. R. Williams. Temperature and void reactivity coefficient calculations for the high flux isotope reactor safety analysis report. Office of Scientific and Technical Information (OSTI), July 1994. http://dx.doi.org/10.2172/10169549.

Full text
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'Void coefficient' for particular source types:
Journal articles
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography