The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Myung Jo Jhung - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic effects on dynamic response of reactor vessel internals
International Journal of Pressure Vessels and Piping, 1996Co-Authors: Myung Jo JhungAbstract:Investigated in this paper is the effect on the dynamic responses of fluid/structure interaction between the components of reactor vessel internals due to their immersion in a confining fluid. A nonlinear mathematical model is developed for the dynamic analysis of the reactor vessel internals which includes lumped Masses, stiffnesses and Hydrodynamic couplings. The Hydrodynamic Mass matrix which characterizes the fluid/structure interaction is calculated. Also, the equations of motion containing the Hydrodynamic Mass matrix are presented. The responses of the reactor vessel internals due to seismic and pipe break excitations are obtained for the case with and without Hydrodynamic couplings and the different response characteristics are discussed.
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Hydrodynamic effects on dynamic response of reactor vessel internals
International Journal of Pressure Vessels and Piping, 1996Co-Authors: Myung Jo JhungAbstract:Investigated in this paper is the effect on the dynamic responses of fluid/structure interaction between the components of reactor vessel internals due to their immersion in a confining fluid. A nonlinear mathematical model is developed for the dynamic analysis of the reactor vessel internals which includes lumped Masses, stiffnesses and Hydrodynamic couplings. The hydr-odynamic Mass matrix which characterizes the fluid/structure interaction is calculated. Also, the equations of motion containing the Hydrodynamic Mass matrix are presented. The responses of the reactor vessel internals due to seismic and pipe break excitations are obtained for the case with and without Hydrodynamic couplings and the different response characteristics are discussed. Copyright © 1996 published by Elsevier Science Ltd.
Leopoldo De Oliveira - One of the best experts on this subject based on the ideXlab platform.
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updated results on Hydrodynamic Mass and damping estimations in tube bundles under two phase crossflow
International Journal of Multiphase Flow, 2017Co-Authors: Ricardo Alvarezbriceno, Fabio Toshio Kanizawa, Gherhardt Ribatski, Leopoldo De OliveiraAbstract:Abstract Flow-Induced Vibration (FIV) is the most critical dynamic issue in the design of shell-and-tube heat exchangers. This fluid-structure phenomenon may generate high amplitude vibration of tubes or structural parts, which leads to fretting wear between the tubes and supports, noise or even fatigue failure of internal components. The study of this phenomenon is more challenging if considered that two-phase crossflow exists in many shell-and-tube heat exchangers. In this framework, the analysis of the influence of void fraction and flow patterns on FIV is of particular interest. In fact, void fraction and flow patterns do affect the dynamic parameters involved in tube vibration and, hence, the current vibration mechanism. However, in spite of the importance of devices subjected to two-phase flow, FIV under these conditions have not been entirely understood. In this paper, the results of an extensive experimental campaign, aiming at validating the flow pattern maps found in open literature, are presented. For this purpose, a normal triangular (transversal pitch per diameter ratio of 1.26) tube bundle subjected to two-phase air - water vertical upward crossflow is used. Structural sensors are used to measure the tube dynamic responses and estimate parameters such as Hydrodynamic Mass and damping ratios, which are strongly dependent on flow conditions. Theoretical models and data previously published are compared with the present experimental results, showing good agreement.
M Abdelmaksoud - One of the best experts on this subject based on the ideXlab platform.
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computation of Hydrodynamic Mass and damping coefficients for a cavitating marine propeller flow using a panel method
Journal of Fluids and Structures, 2014Co-Authors: M Gaschler, M AbdelmaksoudAbstract:Abstract The present paper deals with the numerical calculation of Hydrodynamic Mass and damping coefficients under consideration of unsteady sheet cavitation on marine propeller flows. In the first part of the paper, the mathematical and numerical background behind the numerical method is introduced. The numerical calculations carried out in this work are based on a low-order panel method. Panel methods belong to the class of collocation techniques and are applied to obtain a numerical solution of a potential flow based system of boundary integral equations. They are suitable for the present application because of their short computation time which makes them applicable in the design process of marine propellers. Additionally, two different approaches for the determination of Hydrodynamic Masses and damping are introduced in this work. The Hydrodynamic Masses and damping are important in studies of the ship motion in seaway and in the analysis of vibrations of a vessel and its appendages. The developed approaches are applied on a propeller flow in heave motion. Hereby, the calculations are performed for a non-rotating and rotating propeller under non-cavitating and cavitating conditions. The results obtained from the simulations are discussed in detail and an outlook is given.
D F Strobel - One of the best experts on this subject based on the ideXlab platform.
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titan s Hydrodynamically escaping atmosphere escape rates and the structure of the exobase region
Icarus, 2009Co-Authors: D F StrobelAbstract:Abstract In Strobel [Strobel, D.F., 2008. Icarus, 193, 588–594] a Mass loss rate from Titan's upper atmosphere, ∼ 4.5 × 10 28 amu s − 1 , was calculated for a single constituent, N2 atmosphere by Hydrodynamic escape as a high density, slow outward expansion driven principally by solar UV heating due to CH4 absorption. It was estimated, but not proven, that the Hydrodynamic Mass loss is essentially CH4 and H2 escape. Here the individual conservation of momentum equations for the three major components of the upper atmosphere (N2, CH4, H2) are solved in the low Mach number limit and compared with Cassini Ion Neutral Mass Spectrometer (INMS) measurements to demonstrate that light gases (CH4, H2) preferentially escape over the heavy gas (N2). The lightest gas (H2) escapes with a flux 99% of its limiting flux, whereas CH4 is restricted to ⩾75% of its limiting flux because there is insufficient solar power to support escape at the limiting rate. The respective calculated H2 and CH4 escape rates are 9.2 × 10 27 and 1.7 × 10 27 s − 1 , for a total of ∼ 4.6 × 10 28 amu s − 1 . From the calculated densities, mean free paths of N2, CH4, H2, and macroscopic length scales, an extended region above the classic exobase is inferred where frequent collisions are still occurring and thermal heat conduction can deliver power to lift the escaping gas out of the gravitational potential well. In this region rapid acceleration of CH4 outflow occurs. With the thermal structure of Titan's thermosphere inferred from INMS data by Muller–Wodarg et al. [Muller-Wodarg, I.C.F., Yelle, R.V., Cui, J., Waite Jr., J.H., 2008. J. Geophys. Res. 113, doi:10.1029/2007JE003033 . E10005], in combination with calculated temperature profiles that include sputter induced plasma heating at the exobase, it is concluded that on average that the integrated, globally average, orbit-averaged, plasma heating rate during the Cassini epoch does not exceed ∼ 5 × 10 8 eV cm − 2 s − 1 ( ∼ 0.0008 erg cm − 2 s − 1 ).
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titan s Hydrodynamically escaping atmosphere
Icarus, 2008Co-Authors: D F StrobelAbstract:Abstract The upper atmosphere of Titan is currently losing Mass at a rate ∼ ( 4 – 5 ) × 10 28 amu s −1 , by Hydrodynamic escape as a high density, slow outward expansion driven principally by solar UV heating by CH4 absorption. The Hydrodynamic Mass loss is essentially CH4 and H2 escape. Their combined escape rates are restricted by power limitations from attaining their limiting rates (and limiting fluxes). Hence they must exhibit gravitational diffusive separation in the upper atmosphere with increasing mixing ratios to eventually become major constituents in the exosphere. A theoretical model with solar EUV heating by N2 absorption balanced by HCN rotational line cooling in the upper thermosphere yields densities and temperatures consistent with the Huygens Atmospheric Science Investigation (HASI) data [Fulchignoni, M., and 42 colleagues, 2005. Nature 438, 785–791], with a peak temperature of ∼185–190 K between 3500–3550 km. This model implies Hydrodynamic escape rates of ∼ 2 × 10 27 CH 4 s −1 and 5 × 10 27 H 2 s −1 , or some other combination with a higher H2 escape flux, much closer to its limiting value, at the expense of a slightly lower CH4 escape rate. Nonthermal escape processes are not required to account for the loss rates of CH4 and H2, inferred by the Cassini Ion Neutral Mass Spectrometer (INMS) measurements [Yelle, R.V., Borggren, N., de la Haye, V., Kasprzak, W.T., Niemann, H.B., Muller-Wodarg, I., Waite Jr., J.H., 2006. Icarus 182, 567–576].
A. Jahanmiri - One of the best experts on this subject based on the ideXlab platform.
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Modelling of urea prilling process
2000Co-Authors: N. Rahmanian, Abdolmohammad Alamdari, A. JahanmiriAbstract:A mathematical model is proposed for the urea prilling process of a commercial plant. In this model the prilling process has been simulated by simultaneous solution of the continuity, Hydrodynamic, Mass and energy transfer equations. Particle trajectory, temperature and moisture distribution of the particles and of the cooling air along the height of the tower was calculated from the mathematical model. The air temperature profile resulted from the model was compared with the profile from the urea plant. The model predicted data were consistent with the plant data indicating the validity of the model. The result of this work showed that an increase in heat removed from the particles would improve the characteristics of the product urea.
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MATHEMATICAL MODELLING OF UREA PRILLING PROCESS
Chemical Engineering Communications, 2000Co-Authors: Abdolmohammad Alamdari, A. Jahanmiri, N. RahmaniyanAbstract:Abstract A mathematical model is proposed for the urea prilling process of a commercial plant. In this model the prilling process has been simulated by simultaneous solution of the continuity, Hydrodynamic, Mass and energy transfer equations. Particle trajectory, temperature and moisture distribution of the particles and of the cooling air along the height of the tower was calculated from the mathematical model. The air temperature profile resulted from the model was compared with the profile from the urea plant. The model predicted data were consistent with the plant data indicating the validity of the model. The result of this work showed that an increase in heal removed from the particles would improve the characteristics of the product urea.
