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Статті в журналах з теми "Viscous effects accounting"
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Liang, Hui, and Xiaobo Chen. "Viscous effects on the fundamental solution to ship waves." Journal of Fluid Mechanics 879 (October 1, 2019): 744–74. http://dx.doi.org/10.1017/jfm.2019.698.
Повний текст джерелаАнотація:
The fundamental solution to steady ship waves accounting for viscous effects (the viscous-ship-wave Green function) is investigated within the framework of the weakly damped free-surface flow theory. An explicit expression of the viscous-ship-wave Green function is firstly derived, and an accurate and efficient technique is described to evaluate the Green function via decomposing the free-surface term into the local-flow component and wave component. To delve into the physical features of the viscous-ship-wave Green function, the asymptotic approximations in the far field due to Kelvin, Havelock and Peters are presented for the flow-field point located inside, at and outside the Kelvin wedge. In addition, uniform approximations to the wave component based on the Chester–Friedman–Ursell (CFU) approximation and the Kelvin–Havelock–Peters (KHP) approximation are carried out. Both numerical evaluation and asymptotic approximations show that the singular behaviour is eliminated and the divergent waves associated with large wavenumbers leading to rapid oscillations are severely damped when viscous effects are accounted for. In addition, viscous effects also alter the apparent wake angle associated with the wave pattern created by a high-speed translating source, and the apparent wake angle is dependent on both $\mathscr{U}^{-1}$ and $\mathscr{U}^{-2}$, where $\mathscr{U}$ is the translating speed of the source.
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Fang, Chung, and Cheng-Hsien Lee. "Unsteady Parallel Flows of an Elasto-Visco-Hypoplastic Fluid with Oscillating Boundary." Applied Rheology 18, no. 4 (August 1, 2008): 45001–1. http://dx.doi.org/10.1515/arh-2008-0014.
Повний текст джерелаАнотація:
Abstract In the present study, an evolution equation for the Cauchy stress tensor is proposed to take elastic, viscous and plastic characteristics of complex fluids simultaneously into account. In particular, hypoplasticity is incorporated to account for the plastic features. The stress model is applied to investigate time-dependent flows of an elasto-visco-plastic fluid driven by an oscillating boundary with/without an additional stationary boundary to study the cyclic responses and the model performance. Numerical simulations show that while different degrees of elastic and viscous effects can be captured by varying the model parameters, plastic deformation plays a significant role in the velocity distribution, and can be simulated appropriately by use of hypoplasticity. The stress model is capable of accounting for the combined elastic, viscous and plastic features of complex materials in transient motions, and applications may be found in geomorphic fluid motions like granular and debris flows, and flows involving polymers.
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McMahon, Charles W., Joseph J. Kuehl, and Vitalii A. Sheremet. "A Viscous, Two-Layer Western Boundary Current Structure Function." Fluids 5, no. 2 (April 28, 2020): 63. http://dx.doi.org/10.3390/fluids5020063.
Повний текст джерелаАнотація:
The classic oceanographic problem of a 1.5-layer western boundary current evolving along a straight wall is considered. Here, building upon the previous work of Charney, Huang and Kamenkovich, we have derived, solved and validated a new numerical formulation for accounting for viscous effects in such systems. The numerical formulation is validated against rotating table experimental results.
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Carlone, Pierpaolo, and Gaetano S. Palazzo. "Computational Modeling of the Pulling Force in a Conventional Pultrusion Process." Advanced Materials Research 772 (September 2013): 399–406. http://dx.doi.org/10.4028/www.scientific.net/amr.772.399.
Повний текст джерелаАнотація:
Pultrusion process is gaining increasing attention in several sectors, due to the high productivity and quality achievable. Recent researches highlighted the influence of the pulling force on the quality of pultruded products. In this paper a pulling force model, accounting for compacting, viscous, and frictional effects in a conventional pultrusion process has been implemented. The model is based on the combination of an impregnation, a thermochemical, and a frictional sub-models. Obtained outcomes evidenced, for the considered case,adominant role of the viscous drag.
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Tafili, Merita, and Theodoros Triantafyllidis. "A simple hypoplastic model with loading surface accounting for viscous and fabric effects of clays." International Journal for Numerical and Analytical Methods in Geomechanics 44, no. 16 (August 11, 2020): 2189–215. http://dx.doi.org/10.1002/nag.3122.
Повний текст джерела
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Yoshimoto, S., Y. Ito, and A. Takahashi. "Pumping Characteristics of a Herringbone-Grooved Journal Bearing Functioning as a Viscous Vacuum Pump." Journal of Tribology 122, no. 1 (June 23, 1999): 131–36. http://dx.doi.org/10.1115/1.555371.
Повний текст джерелаАнотація:
A laser scanner motor with low power and high speed has been developed. This scanner motor uses a herringbone-grooved journal bearing which functions as a viscous vacuum pump. The windage power loss of a polygon mirror is reduced, since the air inside the pump housing is pumped out by herringbone-grooved viscous vacuum action. In this paper, the theoretical pumping characteristic of this bearing is investigated, using the narrow-groove theory and accounting for first-order slip flow. The effects of various design parameters on the pumping characteristics are discussed. Optimum geometric design parameters were found to obtain the minimum inner chamber pressure of the housing. The theoretical predictions considering slip flow effects are in good agreement with experimental measurements. [S0742-4787(00)01801-4]
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Saxena, Nishank, and Gary Mavko. "Effects of fluid-shear resistance and squirt flow on velocity dispersion in rocks." GEOPHYSICS 80, no. 2 (March 1, 2015): D99—D110. http://dx.doi.org/10.1190/geo2014-0304.1.
Повний текст джерелаАнотація:
Laboratory measurements of rocks saturated with high-viscosity fluids (such as heavy-oil, bitumen, magma, kerogen, etc.) often exhibit considerable seismic velocity dispersion, which is usually underestimated by the Biot theory. Over the years, grain-scale dispersion mechanisms such as squirt (local-flow) and shear relaxation (nonzero shear stress in the pore fluid) have been more successful in explaining the measured dispersion. We developed a new method to quantify the combined high-frequency effects of squirt and shear dispersion on the effective moduli of rocks saturated with viscous fluids. Viscous fluid at high frequencies was idealized as an elastic solid of finite shear modulus, hydraulically locked in stiff and soft pores. This method entailed performing solid substitution in stiff pores of a dry rock frame, which itself was unrelaxed due to solid-filled soft pores. The unrelaxed frame stiffness solutions required information on the pressure dependency of the rock stiffness and porosity. This method did not have any adjustable parameters, and all required inputs can be directly measured. With various laboratory and numerical examples, we noted that accounting for combined effects of squirt and shear relaxation was necessary to explain laboratory-measured velocities of rocks saturated with fluids of high viscosity. Predictions of the new method were in good agreement with the laboratory data.
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Li, Xu, Jun Li, Xiaoyi Zhang, Jianfeng Gao, and Chao Zhang. "Simplified analysis of cable-stayed bridges with longitudinal viscous dampers." Engineering, Construction and Architectural Management 27, no. 8 (July 30, 2020): 1993–2022. http://dx.doi.org/10.1108/ecam-07-2019-0400.
Повний текст джерелаАнотація:
PurposeViscous dampers are commonly used in large span cable-stayed bridges to mitigate seismic effects and have achieved great success.Design/methodology/approachHowever, the nonlinear analysis on damper parameters is usually computational intensive and nonobjective. To address these issues, this paper proposes a simplified method to determine the viscous damper parameters for double-tower cable-stayed bridges. An empirical formula of the equivalent damping ratio of viscous dampers is established through decoupling nonclassical damping structures and linearization of nonlinear viscous dampers. Shaking table tests are conducted to verify the feasibility of the proposed method. Moreover, this simplified method has been proved in long-span cable-stayed bridges.FindingsThe feasibility of this method is verified by the simplified model shaking table test. This simplified method for determining the parameters of viscous dampers is verified in cable-stayed bridges with different spans.Originality/valueThis simplified method has been validated in cable-stayed bridges with various spans.
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Bico, J. "Cracks in bursting soap films." Journal of Fluid Mechanics 778 (July 30, 2015): 1–4. http://dx.doi.org/10.1017/jfm.2015.376.
Повний текст джерелаАнотація:
The rupture of soap films is traditionally described by a law accounting for a balance between momentum and surface tension forces, derived independently by Taylor and Culick in the 1960s. This law is highly relevant to the dynamics of thin liquid films of jets when viscous effects are negligible. However, the minute amounts of surfactant molecules present in soap films play a major role in interfacial rheology, and may result in complex behaviour. Petit et al. (J. Fluid Mech., vol. 774, 2015, R3) challenge standard thin film dynamics via intriguing experiments conducted with highly elastic surfactants. Unexpected structures reminiscent of faults are observed.
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Shankar, Usha, Neminath B. Naduvinamani, and Hussain Basha. "A generalized perspective of Fourier and Fick’s laws: Magnetized effects of Cattaneo-Christov models on transient nanofluid flow between two parallel plates with Brownian motion and thermophoresis." Nonlinear Engineering 9, no. 1 (April 23, 2020): 201–22. http://dx.doi.org/10.1515/nleng-2020-0009.
Повний текст джерелаАнотація:
AbstractPresent research article reports the magnetized impacts of Cattaneo-Christov double diffusion models on heat and mass transfer behaviour of viscous incompressible, time-dependent, two-dimensional Casson nanofluid flow through the channel with Joule heating and viscous dissipation effects numerically. The classical transport models such as Fourier and Fick’s laws of heat and mass diffusions are generalized in terms of Cattaneo-Christov double diffusion models by accounting the thermal and concentration relaxation times. The present physical problem is examined in the presence of Lorentz forces to investigate the effects of magnetic field on double diffusion process along with Joule heating. The non-Newtonian Casson nanofluid flow between two parallel plates gives the system of time-dependent, highly nonlinear, coupled partial differential equations and is solved by utilizing RK-SM and bvp4c schemes. Present results show that, the temperature and concentration distributions are fewer in case of Cattaneo-Christov heat and mass flux models when compared to the Fourier’s and Fick’s laws of heat and mass diffusions. The concentration field is a diminishing function of thermophoresis parameter and it is an increasing function of Brownian motion parameter. Finally, an excellent comparison between the present solutions and previously published results show the accuracy of the results and methods used to achieve the objective of the present work.
Дисертації з теми "Viscous effects accounting"
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Фесенко, Ксения Владимировна. "Метод расчетно-теоретического исследования структуры течения и характеристик ступеней центробежных нагнетателей". Thesis, Национальный аэрокосмический университет им. Н. Е. Жуковского "Харьковский авиационный институт", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/17150.
Повний текст джерелаАнотація:
Диссертация на соискание ученой степени кандидата технических наук по специальности 05.05.16 – турбомашины и турбоустановки. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2015 г.
В диссертации разработан метод расчетно-теоретического исследования структуры течения и характеристик ступеней центробежных нагнетателей с радиальными лопатками рабочих колес, который позволяет определять в широком диапазоне режимов работы суммарные характеристики и структуру осредненного в окружном направлении сжимаемого дозвукового течения в проточной части, включая межлопаточные каналы. Для учета вязких эффектов использованы обобщенные полуэмпирические зависимости, используемые при анализе течения в центробежных нагнетателях. Данный метод расчета позволяет учитывать геометрические особенности радиальных рабочих колес с лопатками, образованными цилиндрическими и коническими поверхностями, безлопаточных и лопаточных диффузоров, обратных направляющих аппаратов. На основе предложенного метода разработан программный комплекс AxCB, который позволяет проводить численный анализ двумерного дозвукового течения в ступенях центробежных нагнетателей, определять поля газотермодинамичних параметров потока газа и суммарные характеристики ступеней, а также их отдельных элементов. Верификация разработанного метода расчета показала удовлетворительную точность согласования результатов численных исследований течений в криволинейных каналах, рабочих колесах, отдельных элементах и ступенях в целом с данными экспериментальных исследований, а также с аналитическим решением. С помощью предложенного метода и ПК AxCB проведено исследование влияния различных геометрических параметров проточной части и лопаточных венцов на структуру течения и суммарные характеристики ступеней ЦБН, а именно формы средней линии и величины геометрического угла выхода лопатки РК, формы меридиональных обводов проточной части и величины геометрического угла лопатки на входе в ЛД, а также различных вариантов исполнения диффузора ступени. На основании выполненного детального анализа предложено усовершенствование геометрических параметров трех ступеней ЦБН с целью повышения их основных параметров. Ступень "А" усовершенствована путем изменения формы средней линии, а также величины конструктивного угла лопатки на выходе из РК, что привело к увеличению коэффициента политропического напора и расширении рабочей зоны характеристики нагнетателя. Модернизация ступени "Б" заключалась в коррекции формы меридиональных обводов проточной части и величины конструктивного угла лопатки на входе в ЛД, что привело к улучшению согласования работы РК и ЛД. После проведения расчетов ряда вариантов проточной части ступени "В", отличающихся используемым диффузором и шириной проточной части, были даны рекомендации по совершенствованию суммарных характеристик ступени, что при-вело к увеличению коэффициента политропического напора и КПД.Thesis for scientific degree of the Candidate of Sciences (Engineering) on the special-ty 05.05.16 – Turbomachinery and Turboplants. – National Technical University "Kharkiv Politechnical Institute", Kharkov, 2015. The calculation and theoretical studies method of flow structure and characteristics of centrifugal blowers stages with impellers radial vanes was created. It allows determining summary characteristics and 2D flow structure of flow path including blade-to-blade channels in wide range of working regimes. To account for viscous effects generalized semiempirical dependences for centrifugal blowers were used. The proposed method allows taking into account the geometric features of radial impeller with blades that formed by cylindrical and conical surfaces, vaneless and vaned diffusers, reverse guide vanes and gas-path curvilinear contours. The software package AxCB was developed, which allows carrying out the verification of the calculation method. It showed satisfactory accuracy of flow numerical investigation results in the stages with experimental and analytical data. With the proposed method and software package AxCB studies were undertook which dealt with influence of different geometric parameters of flow path and blade rows on the flow structure and stages summary characteristics. On the basis of a detailed analysis modernization of three centrifugal blower stages was proposed to improve their basic parameters or expand the characteristic working area.
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Фесенко, Ксенія Володимирівна. "Метод розрахунково-теоретичного дослідження структури течії та характеристик ступенів відцентрових нагнітачів". Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/17148.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за фахом 05.05.16 – турбомашини та турбоустановки. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2015 р.
В дисертації розроблено метод розрахунково-теоретичного дослідження структури течії та характеристик ступенів відцентрових нагнітачів з радіальними лопатками робочих коліс, який дозволяє визначати в широкому діапазоні режимів роботи сумарні характеристики та структуру осередненої у коловому напрямку стисливої дозвукової течії в проточній частині, включаючи міжлопаткові канали. Для врахування в'язких ефектів використані узагальнені напівемпіричні залежності, що використовуються для розрахунку відцентрових нагнітачів. Запропонований метод дозволяє врахувати геометричні особливості радіальних робочих коліс з лопатками, що образовані циліндричними або конічними поверхнями, лопаткових і безлопаткових дифузорів, зворотних направляючих апаратів та криволінійних обводів проточних частин, а також оцінювати узгодженість їх сумісної роботи. За допомогою розробленого програмного комплексу AxCB проведено верифікацію методу розрахунку, яка показала задовільну точність зіставлення результатів числових досліджень течій в ступенях ВЦН з даними експериментальних досліджень та з аналітичним рішенням. Проведено дослідження впливу геометричних параметрів проточної частини і лопаткових вінців на структуру течії і сумарні характеристики ступенів ВЦН. На підставі виконаного детального аналізу запропоновано удосконалення геометричних параметрів трьох ступенів ВЦН з метою підвищення їх напору, ККД або розширення робочої зони характеристики.Thesis for scientific degree of the Candidate of Sciences (Engineering) on the special-ty 05.05.16 – Turbomachinery and Turboplants. – National Technical University "Kharkiv Politechnical Institute", Kharkov, 2015. The calculation and theoretical studies method of flow structure and characteristics of centrifugal blowers stages with impellers radial vanes was created. It allows determining summary characteristics and 2D flow structure of flow path including blade-to-blade channels in wide range of working regimes. To account for viscous effects generalized semiempirical dependences for centrifugal blowers were used. The proposed method allows taking into account the geometric features of radial impeller with blades that formed by cylindrical and conical surfaces, vaneless and vaned diffusers, reverse guide vanes and gas-path curvilinear contours. The software package AxCB was developed, which allows carrying out the verification of the calculation method. It showed satisfactory accuracy of flow numerical investigation results in the stages with experimental and analytical data. With the proposed method and software package AxCB studies were undertook which dealt with influence of different geometric parameters of flow path and blade rows on the flow structure and stages summary characteristics. On the basis of a detailed analysis modernization of three centrifugal blower stages was proposed to improve their basic parameters or expand the characteristic working area.
Тези доповідей конференцій з теми "Viscous effects accounting"
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Ommani, Babak, Nuno Fonseca, and Carl Trygve Stansberg. "Simulation of Low Frequency Motions in Severe Seastates Accounting for Wave-Current Interaction Effects." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62550.
Повний текст джерелаАнотація:
Today’s industry practice assumes wave drift forces on floating structures can be computed from zero current wave drift force coefficients for the stationary floater, while simplified correction models introduce current effects and slow drift velocity effects. The paper presents an alternative approach which overcomes some of the limitations of today’s procedures. The method, to be applied together with a time domain solution of the low frequency motions, is based on pre-calculation of mean wave drift force coefficients for a range of current velocities. During the low frequency motions simulation, the wave drift forces induced by the irregular waves are computed from the mean drift coefficients corresponding to instantaneous relative velocity resulting from the current and the low frequency velocities. A simple interpolation model, based on a quasi-steady assumption, is applied to obtain the drift forces in time-domain. Since calculation of the wave drift forces on Semi-submersibles in severe sea states with fully consistent methods is out of reach, a semi-empirical model is applied to correct the potential flow wave drift force coefficients. This model takes into account viscous effects, that are important in high seastates, and wave-current interaction effects. The paper compares the wave drift forces and the related low frequency motions computed by the proposed method, with results applying “standard” methods and with model test data. The test data was obtained in the scope of the EXWAVE JIP, with model tests designed to investigate wave drift forces in severe seastates and assess the wave-current interaction effects.
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Natali, Arturo N., Emanuele L. Carniel, Piero G. Pavan, Alessio Gasparetto, Franz G. Sander, Christina Dorow, and Martin Geiger. "Constitutive Formulation for Numerical Analysis of Visco-Hyperelastic Damage Phenomena in Soft Biological Tissues." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95254.
Повний текст джерелаАнотація:
Soft biological tissues show a strongly non linear and time-dependent mechanical response and undergo large strains under physiological loads. The microstructural arrangement determines specific anisotropic macroscopic properties that must be considered within a constitutive formulation. The characterization of the mechanical behaviour of soft tissues entails the definition of constitutive models capable of accounting for geometric and material non linearity. In the model presented here a hyperelastic anisotropic formulation is adopted as the basis for the development of constitutive models for soft tissues and can be properly arranged for the investigation of viscous and damage phenomena as well to interpret significant aspects pertaining to ordinary and degenerative conditions. Visco-hyperelastic models are used to analyze the time-dependent mechanical response, while elasto-damage models account for the stiffness and strength decrease that can develop under significant loading or degenerative conditions. Experimental testing points out that damage response is affected by the strain rate associated with loading, showing a decrease in the damage limits as the strain rate increases. This phenomena can be investigated by means of a model capable of accounting for damage phenomena in relation to viscous effects. The visco-hyperelastic damage model developed is defined on the basis of a Helmholtz free energy function depending on the strain-damage history. In particular, a specific damage criterion is formulated in order to evaluate the influence of the strain rate on damage. The model can be implemented in a general purpose finite element code. This makes it possible to perform numerical analyses of the mechanical response considering time-dependent effects and damage phenomena. The experimental tests develop investigated tissue response for different strain rate conditions, accounting for stretch situations capable of inducing damage phenomena. The reliability of the formulation is evaluated by a comparison with the results of experimental tests performed on pig periodontal ligament.
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Chaussonnet, G., R. Koch, H. J. Bauer, A. Sänger, T. Jakobs, and T. Kolb. "SPH Simulation of an Air-Assisted Atomizer Operating at High Pressure: Influence of Non-Newtonian Effects." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63033.
Повний текст джерелаАнотація:
A twin-fluid atomizer configuration is predicted by means of the 2D weakly-compressible Smooth Particle Hydrodynamics (SPH) method and compared to experiments. The setup consists of an axial liquid jet fragmented by a co-flowing high-speed air stream (Ug ≈ 60 m/s) in a pressurized atmosphere up to 11 bar (abs.). Two types of liquid are investigated: a viscous Newtonian liquid (μl = 200 mPas) obtained with a glycerol/water mixture and a viscous non-Newtonian liquid (μl, apparent. ≈ 150 mPas) obtained with a carboxymethyl cellulose (CMC) solution. 3D effects are taken into account in the 2D code by introducing (i) a surface tension term, (ii) a cylindrical viscosity operator and (iii) a modified velocity accounting for the divergence of the volume in the radial direction. The numerical results at high pressure show a good qualitative agreement with experiment, i.e. a correct transition of the atomization regimes with regard to the pressure, and similar dynamics and length scales of the generated ligaments. The predicted frequency of the Kelvin-Helmholtz instability needs a correction factor of 2 to be globally well recovered with the Newtonian liquid. The simulation of the non-Newtonian liquid at high pressure shows a similar breakup regime with finer droplets compared to Newtonian liquids while the simulation at atmospheric pressure shows an apparent viscosity similar to the experiment.
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Xiang, Xu, Erik Svangstu, Øyvind Nedrebø, Bernt Jakobsen, Mathias Egeland Eidem, Per Norum Larsen, and Bernt Sørby. "Viscous Damping Modelling of Floating Bridge Pontoons With Heaving Skirt and its Impact on Bridge Girder Bending Moments." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61041.
Повний текст джерелаАнотація:
The current floating bridge concepts of Norwegian Public Roads Administration (Statens vegvesen, NPRA) use a flange shape part at the bottom part of the pontoons. The flange is in principle similar to the damping plates used in the offshore industry for SPAR type of structures. The project group initiated the flange part based on the requirement of extra added mass for tuning the bridge system Eigen-modes. Thus, the important modes can be shifted out of the main wave energy zone. The current study will focus on the damping effects of such structure. The damping effects on weak axis bending moment prediction is studied. The modelling of such damping is first proposed according to relevant literature based on both numerical and experimental studies. Since the reference studies were mainly focused on cylindrical structures, it is difficult to obtain an accurate estimation of the damping coefficient for the current bridge pontoon design, which contains a rectangular part between two half-cylindrical parts. In addition, the estimation of pontoon motions needs the input of damping coefficient, which means that the evaluation of damping coefficient is an iteration process. In order to include the uncertainties, a conservative value was adopted to represent the damping effect. The comparison of accounting for the damping effects or not has been given for all the bridge pontoons. The results show that the damping effects are important at the peaks of the responses; in addition, the reduction of the predicted maximum bending moments can be expected around 10–15 percent along different positions of the bridge. However, a further investigation also shows that viscous excitation would increase the bending moments slightly. The comparison also indicates the value of further investigating the effects by CFD or model test methods.
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Bazargan, Majid, and Mahdi Mohseni. "Effect of Turbulent Prandtl Number on Convective Heat Transfer to Turbulent Upflow of Supercritical Carbon Dioxide." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88461.
Повний текст джерелаАнотація:
A two-dimensional model is developed to simultaneously solve the momentum and energy equations and thus predict convection heat transfer to an upward flow of supercritical carbon dioxide in a round tube. The effect of the turbulent Prandtl number, Prt, on heat transfer coefficients has been extensively studied. A number of constant values of Prt, as well as a number of suggested equations accounting for variations of Prt with flow conditions, have been examined. The investigation has been carried out for both regimes of enhanced and deteriorated heat transfer. The results of this study show that the increase of Prt, even in the viscous sublayer, cause the heat transfer coefficients to decrease. The models of Prt leading to best agreement with experiments in either regimes of heat transfer were recognized. From the effect Prt has on heat transfer coefficients, it has been deduced that the buoyancy effects in upward flow of a supercritical fluid causes the Prt to decrease and hence the heat transfer coefficients to increase.
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Rezaeimoghaddam, Mohammad, Rasool Elahi, M. R. Modarres Razavi, and Mohammad B. Ayani. "Modeling of Non-Newtonian Fluid Flow Within Simplex Atomizers." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25266.
Повний текст джерелаАнотація:
In this paper the Volume-of-Fluid (VOF) method is used to simulate Newtonian and non-Newtonian fluid flow within simplex (pressure-swirl) atomizers. The two-dimensional axisymmetric swirl Navier-Stokes equations coupled with the VOF method is employed for accounting the formation mechanism of the liquid film inside the swirl chamber and the orifice hole of the pressure swirl atomizer. For verification of the code, the numerical results were compared with experimental data for large scale prototype injector with water (Newtonian fluid) as injection fluid in various constant inlet mass flow rate. By using power-law equation to calculate shear stress terms in the Navier-Stokes equations, the code is extended to compute Newtonian and non-Newtonian fluid flow inside the atomizer. The time-independent purely viscous power-law fluids flow in pressure-swirl atomizers is simulated. The effects of shear-thinning fluids (0.5 < n <1), viscous Newtonian (n = 1) fluids and shear thickening fluids (1< n < 1.5) on atomizers performance (discharge coefficient and spray cone angle) were investigated. Results were shown that with increasing the power-law index the spray cone angle decreases and the discharge coefficient increases.
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Baer, Thomas A., David R. Noble, Rekha R. Rao, and Anne M. Grillet. "A Level Set Approach to 3D Mold Filling of Newtonian Fluids." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45762.
Повний текст джерелаАнотація:
Filling operations, in which a viscous fluid displaces a gas in a complex geometry, occur with surprising frequency in many manufacturing processes. Difficulties in generating accurate models of these processes involve accurately capturing the interfacial boundary as it undergoes large motions and deformations, preventing dispersion and mass-loss during the computation, and robustly accounting for the effects of surface tension and wetting phenomena. This paper presents a numerical capturing algorithm using level set theory and finite element approximation. Important aspects of this work are addressing issues of mass-conservation and the presence of wetting effects. We have applied our methodology to a three-dimension model of a complicated filling problem. The simulated results are compared to experimental flow visualization data taken for filling of UCON oil in the identical geometry. Comparison of simulation and experiment indicates that the simulation conserved mass adequately and the simulated interface shape was in approximate agreement with experiment. Differences seen were largely attributed to inaccuracies in the wetting line model.
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Ferrant, Pierre, Lionel Gentaz, Bertrand Alessandrini, Romain Luquet, Charles Monroy, Guillaume Ducrozet, Erwan Jacquin, and Aure´lian Drouet. "Fully Nonlinear Potential/RANSE Simulation of Wave Interaction With Ships and Marine Structures." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57952.
Повний текст джерелаАнотація:
This paper documents recent advances of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach, a method for simulating fully nonlinear wave-body interactions including viscous effects. The methods efficiently combines a fully nonlinear potential flow description of undisturbed wave systems with a modified set of RANS with free surface equations accounting for the interaction with a ship or marine structure. Arbitrary incident wave systems may be described, including regular, irregular waves, multidirectional waves, focused wave events, etc. The model may be fixed or moving with arbitrary speed and 6 degrees of freedom motion. The extension of the SWENSE method to 6 DOF simulations in irregular waves as well as to manoeuvring simulations in waves are discussed in this paper. Different illlustative simulations are presented and discussed. Results of the present approach compare favorably with available reference results.
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Kalabayev, Ruslan, Dmitriy Abdrazakov, Yeltay Juldugulov, Vladimir Stepanov, Denis Emelyanov, Rostislav Romanovskii, and Campbell Kinnear. "Advanced Fracturing Design Simulator-Assisted Modeling Coupled with Application of Enhanced Stimulation Fluids Raises Performance of Acid Fractured Wells." In SPE Europec featured at 82nd EAGE Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205139-ms.
Повний текст джерелаАнотація:
Abstract Important factors affecting acid fracturing efficiency include etched fracture geometry, cleanup, and optimum differential etching to retain open channels after fracture closure. A recently applied integrated approach combined improvements in all three factors: new fracture simulation techniques enabled fracture geometry optimization, single-phase retarded acid provided significant increase in half-length, and high retained permeability viscous fluids supported better fracture cleanup. The approach was successfully implemented in several carbonate oil fields and resulted in a substantial productivity index increase. The approach enables acid fracture optimization in three steps. First, the high retained permeability, low-pH pad fluids and polymer-free leakoff control acids are used in combination to enhance formation cleanup after a treatment and to reduce the concentration of polymers in fissures network of naturally fractured carbonate reservoirs. Second, a new single-phase retarded acid is used to achieve longer half-length due to retarded reaction with formation rock and favorable viscous fingering effects. Third, a new acid fracturing simulation model is used to optimize fracture geometry. The simulation technique employs an innovative transport model that includes the viscous fingering effect, advanced leakoff simulation, changing acid rheology upon spending, and a novel calculation approach to mixed fluids' rheology. This combined concept was applied during acid fracturing treatments in moderate permeability wells of carbonate reservoirs with target intervals up to 4,600 m TVD and temperatures up to 125°C. The treatments consisted of guar-free low-pH pad fluid, polymer-free leakoff control acid, and single-phase retarded acid. Treatment optimization was performed using an advanced acid fracturing simulator to properly address the transport processes within the fracture in a low-stress-contrast environment. After the treatments, the pressure transient analysis indicated a strong linear regime for more than 15 hours, indicating effective fracture half-length at least 25% higher than average half-length after acid fracturing in offset wells where the conventional approach had been applied. Post-treatment half-length calculations showed a good match with advanced simulator results and proved the importance of accounting for viscous fingering effects during acid fracture half-length calculations. Calculation of the productivity index from the production data showed at least 15% increase compared to conventional acid fracturing treatments. The post-fracturing production decline rate was at least 20% slower than that of the conventional treatment in offset wells, which can be explained by the longer conductive fracture.
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Achkinadze, Alexander S., Aage Berg, Vladimir I. Krasilnikov, and Ivan E. Stepanov. "Numerical Analysis of Podded and Steering Systems Using a Velocity Based Source Boundary Element Method with Modified Trailing Edge." In SNAME 10th Propeller and Shafting Symposium. SNAME, 2003. http://dx.doi.org/10.5957/pss-2003-12.
Повний текст джерелаАнотація:
This paper describes an improved velocity based source boundary element method (HEM) as applied to modeling of podded propellers and propeller/rudder systems. The distinctive feature of the present method consists in the direct satisfaction of the Kutta-Joukowski condition on the additional Kutta panel constructed behind the realistic blade trailing edge when defining the unknown doublet strength. This Modified Trailing Edge (MTE) is also used as a tool for the approximate accounting for viscous and related effects on circulation. The integrated propulsive/steering system is simulated within the potential frameworks using the velocity field iterations method and quasi-steady approach, which assumes the simulation of a propeller in a spatially varying flow field while pod and strut(/rudder) are considered in a circumferentially averaged flow field The developed method is applied for calculation of rudder behind the operating propeller and podded units of different arrangement tested at MARINTEK (Norwegian Marine Technology Research Institute). The results of the measurements and theory/experiment comparisons are discussed.