Relevant bibliographies by topics / Spherical collapse model

Academic literature on the topic 'Spherical collapse model'

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Published: 11 March 2023

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Journal articles on the topic "Spherical collapse model"

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DEL POPOLO, ANTONINO. "IMPROVEMENTS TO THE SPHERICAL COLLAPSE MODEL." International Journal of Modern Physics D 15, no. 07 (July 2006): 1067–88. http://dx.doi.org/10.1142/s0218271806008553.

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We study the joint effect of dynamical friction, tidal torques and cosmological constant on clusters of galaxy formation. We show that within high-density environments, such as rich clusters of galaxies, both dynamical friction and tidal torques slow down the collapse of low-ν peaks producing an observable variation in the time of collapse of the perturbation and, as a consequence, a reduction in the mass bound to the collapsed perturbation. Moreover, the delay of the collapse produces a tendency for less dense regions to accrete less mass, with respect to a classical spherical model, inducing a biasing of over-dense regions toward higher mass. We show how the threshold of collapse is modified if dynamical friction, tidal torques and a non-zero cosmological constant are taken into account and we use the Extended Press–Schecter (EPS) approach to calculate the effects on the mass function. Then, we compare the numerical mass function given in D. Reed, Mon. Not. R. Astron. Soc.346, 565 (2003) with the theoretical mass function obtained in the present paper. We show that the barrier obtained in the present paper gives rise to a better description of the mass function evolution with respect to other previous models, R. K. Sheth and G. Tormen, Mon. Not. R. Astron. Soc.308, 119 (1999) and R. K. Sheth and G. Tormen, Mon. Not. R. Astron. Soc.329, 61 (2002).
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Taddei, Laura. "Spherical Collapse in the Symmetron Model." Journal of Physics: Conference Series 470 (December 6, 2013): 012006. http://dx.doi.org/10.1088/1742-6596/470/1/012006.

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GOVENDER, M., K. S. GOVINDER, S. D. MAHARAJ, R. SHARMA, S. MUKHERJEE, and T. K. DEY. "RADIATING SPHERICAL COLLAPSE WITH HEAT FLOW." International Journal of Modern Physics D 12, no. 04 (April 2003): 667–76. http://dx.doi.org/10.1142/s0218271803003086.

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We present here a simple model of radiative gravitational collapse with radial heat flux which describes qualitatively the stages close to the formation of a superdense cold star. Starting with a static general solution for a cold star, the model can generate solutions for the earlier evolutionary stages. The temporal evolution of the model is specified by solving the junction conditions appropriate for radiating gravitational collapse. The results will be useful in constructing models for the evolution of X-ray pulsars, like Her X-1.
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Del Popolo, Antonino, and Morgan Le Delliou. "Splashback Radius in a Spherical Collapse Model." Universe 8, no. 9 (September 6, 2022): 462. http://dx.doi.org/10.3390/universe8090462.

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It was shown several years ago that dark matter halo outskirts are characterized by very steep density profiles in a very small radial range. This feature has been interpreted as a pile-up of different particle orbits at a similar location, namely, splashback material at half an orbit after collapse. Adhikari et al. (2014) obtained the location of the splashback radius through a very simple model by calculating a dark matter shell trajectory in the secondary infall model while it crosses a growing NFW profile-shaped dark matter halo. Because they imposed a halo profile instead of calculating it from the trajectories of the shells of dark matter, they were not able to find the dark matter profile around the splashback radius. In the present paper, we use an improved spherical infall model taking into account shell crossing as well as several physical effects such as ordered and random angular momentum, dynamical friction, adiabatic contraction, etc. This allows us to determine the density profile from the inner to the outer region and to study the behavior of the outer density profile. We compare the density profiles and their logarithmic slope of with the simulation results of Diemer and Kravtsov (2014), finding a good agreement between the prediction of the model and the simulations.
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Del Popolo, A. "Some improvements to the spherical collapse model." Astronomy & Astrophysics 454, no. 1 (July 2006): 17–26. http://dx.doi.org/10.1051/0004-6361:20054441.

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Cupani, Guido, Marino Mezzetti, and Fabio Mardirossian. "Angular momentum in cluster Spherical Collapse Model." Monthly Notices of the Royal Astronomical Society 417, no. 4 (October 6, 2011): 2554–61. http://dx.doi.org/10.1111/j.1365-2966.2011.19419.x.

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Lee, Seokcheon. "Spherical collapse model with and without curvature." Physics Letters B 685, no. 2-3 (March 2010): 110–14. http://dx.doi.org/10.1016/j.physletb.2010.01.058.

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Sanchez-Conde, M. A., J. Betancort-Rijo, and F. Prada. "The spherical collapse model with shell-crossing." Monthly Notices of the Royal Astronomical Society 378, no. 1 (June 11, 2007): 339–52. http://dx.doi.org/10.1111/j.1365-2966.2007.11798.x.

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DEL POPOLO, A., F. PACE, and J. A. S. LIMA. "EXTENDED SPHERICAL COLLAPSE AND THE ACCELERATING UNIVERSE." International Journal of Modern Physics D 22, no. 08 (June 21, 2013): 1350038. http://dx.doi.org/10.1142/s0218271813500387.

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The influence of the shear stress and angular momentum on the nonlinear spherical collapse model is discussed in the framework of the Einstein–de Sitter and ΛCDM models. By assuming that the vacuum component is not clustering within the homogeneous nonspherical overdensities, we show how the local rotation and shear affect the linear density threshold for collapse of the nonrelativistic component (δc) and its virial overdensity (ΔV). It is also found that the net effect of shear and rotation in galactic scale is responsible for higher values of the linear overdensity parameter as compared with the standard spherical collapse model (no shear and rotation).
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Mohanty, Sujata, and Rajesh Gopal. "Analysis of cosmological bias within spherical collapse model." EUREKA: Physics and Engineering, no. 5 (September 30, 2022): 3–11. http://dx.doi.org/10.21303/2461-4262.2022.002429.

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The goal of our research work is to analyze cosmological bias parameter. Parametric equations of spherical collapse model are used to calculate the values of spherical collapse over density and mass variance, which is further used in bias formulae to find the values of cosmological bias. Spherical collapse over density has been calculated in the range of redshift 0 to 1. Also, it is compared with the value according to the spherical collapse model. Bias is one of the parameters which are utilized to infer cosmological parameters. Extracting the cosmological parameters is very much useful to know and understand about the birth and evolution of our universe. As there is no direct probe to get the idea about the existence of dark matter. Bias factor helps to analyze about dark matter. The bias coefficient of higher order terms in Taylor series expansion are found to be in ascending order. Increasing values of bias indicate the large-scale structure formation at current epoch is more and more clustered. Values of bias are discussed in result. Also, bias values have been analyzed for redshift in the range 2 to 0. The graph has been plotted bias versus redshift. Let’s found bias decreases with decrease of redshift. That means bias evolves with redshift. Bias value less than one and negative value of bias implies that structure formation is in linear region and higher values of bias indicates the structure formation occurs in nonlinear region. Negative value of bias is also called as antibias. That means the structure formation has not started yet. It is still in linear region. The bias value nearly equal to one indicates that the structure formation has been transformed from linear region to nonlinear region. So, the result showing bias values greater than one indicates that evolution of structure formation occurs in nonlinear region.
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Dissertations / Theses on the topic "Spherical collapse model"

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Reyes, Juan Daniel Bojowald Martin. "Spherically symmetric loop quantum gravity connections to two-dimensional models and applications to gravitational collapse /." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4758/index.html.

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Cupani, Guido. "Non equilibrium dynamics of galaxy clusters." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3065.

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2007/2008
The thesis is focused on the dynamics of galaxies in the outskirts of galaxy clusters, where the matter is affected by an overall infall motion towards the cluster centre. Starting from the classical results of the spherical collapse model, we determined new theoretical constraints for the mass profile of clusters as a function of the cosmological parameters. We investigated the importance of the turnaround radius (i.e. the radius where the infall motion counterbalances the Hubble expansion motion) as well as the possibility of directly extracting the mass profile from the infall velocity pattern of member galaxies. The theoretical results were applied to a sample of simulated clusters (Borgani et al. 2004, Biviano et al. 2006) to keep the 3-dimensional dynamics under control. We demonstrated that: (1) most clusters are compatible with a single mass profile in the external region (provided their size and mass are normalized to the turnaround scale); (2) it is possible to extract the individual mass profiles of clusters using a selected subset of galaxies identified on their redshift-position distribution; (3) the Jeans equation and the virial theorem must be corrected in the outskirts of clusters to take into account the overall infall motion of matter. Taking advantage of these results, we developed a new technique for estimating the mass profile in cluster outskirts which only relies on the observational properties of member galaxies. This technique turns out to be simpler and more reliable than the current methods and is suitable to be applied to observations.
La tesi è incentrata sulla dinamica delle galassie nelle periferie degli ammassi di galassie, dove la materia è interessata da un moto complessivo di caduta verso il centro dell'ammasso. A partire dai risultati classici del modello di collasso sferico, abbiamo determinato dei nuovi vincoli teorici al profilo di massa degli ammassi in funzione dei parametri cosmologici. Abbiamo analizzato l'importanza del raggio di "turnaround" (ossia il raggio dove il moto di caduta è controblanciato dal moto di espansione di Hubble) e la possibilità di estrarre il profilo di massa direttamente dalla velocità di caduta delle galassie. Abbiamo poi applicato questi risultati teorici a un campione di ammassi simulati (Borgani et al. 2004, Biviano et al. 2006) per tenere sotto controllo la dinamica in tre dimensioni. Con quest'analisi, siamo stati in grado di dimostrare che: (1) la quasi totalità degli ammassi è compatibile con un unico profilo di massa nelle regioni esterne (purché le loro dimensioni e masse siano riscalate rispetto al raggio di turnaround); (2) è possibile estrarre il profilo individuale di un ammasso utilizzando un ristretto sottoinsieme di galassie, identificate dalla distribuzione dei loro redshift e delle loro posizioni; (3) l'equazione di Jeans e il teorema del viriale devono essere corretti nelle periferie degli ammassi in modo da tener conto del moto di caduta della materia. Grazie a questi risultati, abbiamo sviluppato una nuova tecnica per stimare il profilo di massa nelle zone esterne, basata unicamente sulle proprietà osservative delle galassie. Questa tecnica risulta essere più semplice e affidabile degli altri metodi attualmente utilizzati ed è adatta ad essere applicata alle osservazioni.
XXI Ciclo
1981
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Jian, Jia-Hung, and 簡嘉宏. "Spherical Collapse Model( Cosmological N-Body Simulation with Cold Dark Matter and Hot Plasma Gas )." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/95183576032706860748.

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Waizmann, Jean-Claude [Verfasser]. "On finding galaxy clusters with Planck and the spherical collapse model in different Dark Energy cosmologies / put forward by Jean-Claude Waizmann." 2010. http://d-nb.info/1009399861/34.

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Chang, Chia-Chun, and 張嘉君. "Spherical Collapse Models with Clustered Dark Energy." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7m9222.

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博士
國立臺灣師範大學
物理學系
106
We use the spherical collapse model to investigate the clustering effect of dark energy (DE) in the structure formation of galaxy clusters. For the fully clustered DE, we treat the overdense region as an isolated system and the total energy of matter and DE conserves inside the spherical region. Under this circumstance, we introduce a parameter r to characterize the degree of DE clustering, defined by the nonlinear density contrast ratio of DE to matter at the turnaround epoch, and thus we are able to determine the process of the spherical collapse and obtain the virialized nonlinear overdensity ∆ vir by the virial theorem. The current observational data on galaxy clusters suggests 0.5 < r < 0.8 for the clustered DE with w < −0.9 at 1σ level. In addition, we utilize the linear perturbation theory to deal with the evolution of DE perturbation at the early time and calculate the related physical quantities. We compare the two methods and find both results consistent with each other while our method introducing a new parameter is simpler and more straightforward without considering the initial DE perturbation and its evolution at the early time.
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Books on the topic "Spherical collapse model"

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Deruelle, Nathalie, and Jean-Philippe Uzan. Newtonian cosmology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.003.0016.

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This chapter discusses the construction of models of the universe, which is ambiguous in Newtonian theory. It presents some results recovered within the framework of general relativity, which in addition makes it possible to lay the foundation of the theory of the formation of large-scale structures in the universe such as galaxies and galactic clusters. The chapter first constructs models of an expanding sphere. If galaxies are treated as the particles of a uniform cloud which is spherically symmetric about the origin of an inertial frame, then these models describe a universe which expands and eventually collapses on itself. The chapter then turns to the pitfalls of the infinite Newtonian universe, the ‘Friedmann’ equation, the evolution of perturbations, and Olbers’s paradox.
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Book chapters on the topic "Spherical collapse model"

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Umeda, Hideyuki, and Takashi Yoshida. "Nucleosynthesis in Spherical Explosion Models of Core Collapse Supernovae." In Handbook of Supernovae, 1–18. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-20794-0_76-1.

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Umeda, Hideyuki, and Takashi Yoshida. "Nucleosynthesis in Spherical Explosion Models of Core-Collapse Supernovae." In Handbook of Supernovae, 1753–70. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-21846-5_76.

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Abbasi, Afaq Ahmed, Michele Viviani, Daniele Bertetta, Marina Delucchi, Rico Ricotti, and Giorgio Tani. "Experimental Analysis of Cavitation Erosion on Blade Root of Controllable Pitch Propeller." In Progress in Marine Science and Technology. IOS Press, 2022. http://dx.doi.org/10.3233/pmst220032.

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The aim of this study is to experimentally investigate the cavitation erosion on the blade root of a model scale controllable pitch propeller. Tests are carried out in a cavitation tunnel, using the soft paint technique to study cavitation erosion, exploiting also two standard cameras and one high speed camera to study the damage patterns and cavitation dynamics, respectively. Standard cameras are placed on the top of test section in order to periodically monitor the occurrence of damages on the layer of paint. The high-speed camera has been used instead to analyse bubble dynamics and identify potentially erosive phenomena. Three different cavitation bubble structures on the blade root have been identified in the present study: streak cavitation, spherical bubble cavitation, and twisting bubble cavitation. The paint tests results have been analysed together with high-speed videos, showing a remarkable agreement between the occurrence of damage and cavitation collapse phenomena. The results demonstrated two regions on the propeller blade root with high risk of erosion: (1) suction side blade root showed significant damage pattern due to single bubble as well as bubble assembly collapse, and (2) pressure side blade root showed slight damage pattern due to spherical bubble collapse.
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Zhao, T., G. T. Houlsby, and S. Utili. "Numerical Simulation of the Collapse of Granular Columns Using DEM." In Discrete Element Modelling of Particulate Media, 133–40. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00133.

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In this paper, the collapse of plain strain dry granular columns was investigated by means of 3D DEM (Discrete Element Method) simulations. In the literature, 2D DEM analyses have been previously performed and showed to be unable to replicate the experimentally observed mass flow and final run-out distances. This is mainly due to the inability of 2D simulations to replicate the three dimensional motion of real particles. Spherical particles and a simple contact model based on linear springs, dashpots and frictional sliders were employed in the presented simulations. A rolling resistance model governed by two micromechanical parameters was added in order to indirectly account for the effect of particle non-sphericity on the angular moment equilibrium of the granular assembly. Calibration of the rolling resistance model leads to predictions of run-out distances in quantitative agreement with the available experimental data.
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Conference papers on the topic "Spherical collapse model"

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LOKAS, E. L., and y. HOFFMAN. "THE SPHERICAL COLLAPSE MODEL IN A UNIVERSE WITH COSMOLOGICAL CONSTANT." In Proceedings of the Third International Workshop. WORLD SCIENTIFIC, 2001. http://dx.doi.org/10.1142/9789812811363_0012.

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Hasan, Mainul. "Dynamics of a Micro-Bubble Between Two Spherical Particles." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37053.

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The effects of high intensity ultrasound field in water and the resulting volume oscillations of one underwater micron-sized gas bubble initially resting between two larger but micron-sized solid particles are numerically studied. The model assumes that the two particles remain at rest while the bubble changes its shape in the presence of the particles. Specifically, this study predicts the bubble’s expansion, collapse, and interaction effects with the adjacent two solid spherical particles which are not necessarily of equal size. The model assumes that the flow surrounding the bubble and two particles is incompressible. A 2-D Finite Element method which is capable of tracking the ultra fast moving boundary of the bubble is developed and an associated computer program is written to solve the modeled equations and boundary conditions. In the absence of a similar study in the literature, the validation (although not shown here) of the numerical method is carried out by solving the expansion and collapse of a single bubble initially resting in an infinite extent of fluid for which theoretical results are well-known in the literature. A good agreement is obtained between the numerical and theoretical results [18]. Numerical results for the temporal shapes of the bubble, its lifetimes for various parametric cases are provided and discussed. The variations of the pressure and the velocity fields in the liquid surrounding the bubble and two particles are also analyzed and discussed.
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Chahine, Georges. "A Numerical Model for Three-Dimensional Bubble Dynamics in Complex Flow Configurations." In SNAME 22nd American Towing Tank Conference. SNAME, 1989. http://dx.doi.org/10.5957/attc-1989-008.

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In most practical configurations where cavitation occurs, bubbles are not in a uniform or axisymmetric flow field and existing bubble dynamics models, either spherical or axisymmetric, are only more or less appropriate approximations. In this paper we will describe on-going studies which consider the fully three-dimensional bubble dynamics problem. The interaction between a growing, deforming and collapsing bubble near a boundary and/or in a non-uniform flow field is simulated numerically using a Boundary Integral Method. The collapse of a large bubble near a solid flat plate in a gravity field is considered as a first example. The plate orientation relative to the gravity field significantly influences the three-dimensional bubble shape and behavior. Another not previously solved case considered here is the growth and collapse of a bubble in a vortex line flow. The paper presents the method and shows on examples the influence of the various geometric or flow parameters on the bubble dynamics.
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Krishnan, Gopi, and Kamran Mohseni. "On the Modelling of a Synthetic Jet as a Spherical Jet." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37306.

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The properties of a flow field of a synthetic jet are studied using hot wire anemometry. The experimental results are compared with an analytical model of a continuous jet derived in spherical coordinates. The radial velocity profiles at various radial distances from the synthetic jet orifice, when scaled appropriately collapse into a single self similar profile. The time averaged flow field can be modeled as an axially symmetric jet, with the replacement of empirical constants obtained from the measurement of the synthetic jet. It is shown that the synthetic jet has a higher spreading rate, and effective viscosity than that of an equivalent turbulent jet with constant mass flow rate. The analytical model in spherical coordinates is shown in this case, to better represent the experimental data than a model derived in cylindrical coordinates.
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Alhelfi, Ali, and Bengt Sunden. "The Boundary Integral Method Applied to Non-Spherical Cavitation Bubble Growth and Collapse Close to a Rigid Boundary." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51687.

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Recently much attention has been paid to studies concerning bubble dynamics in the cavitation phenomena and this topic has been the subject of many research works. In fact, the simulation of non-spherical bubble dynamics and its interaction with solid boundaries have received much less attention due to the complexity of the problem. One of the main reasons of the structural damages in the cavitation phenomenon is due to the formation of micro jets generated due to the bubble collapse and impinging on the solid surfaces or boundaries. The boundary integral method (BIM) based on Green’s function is used to model the oscillation and collapse of a cavitation bubble close to a rigid boundary. The liquid is considered to be incompressible, inviscid, and irrational around the bubble. These assumptions satisfy the conditions for the Laplacian equation. The theory permits one to predict correctly the interaction between the bubble and the rigid boundary, which is of great importance in the study of cavitation damage due to a bubble collapsing close to the boundaries. The results reveal that the amplitude of bubble oscillation depends on the bubble location away from a rigid surface. Also, the theory for the cavitation bubble dynamics presented in this study has many advantages in various situations and might be helpful to understand effects of the cavitation phenomenon such as generation of excessive vibration, surface erosion and undesirable acoustic emission.
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Ma, Jingsen, Chao-Tsung Hsiao, and Georges L. Chahine. "Euler-Lagrange Simulations of Bubble Cloud Dynamics Near a Wall." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65191.

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We present in this paper a two-way coupled Eulerian-Lagrangian model to study the dynamics of microbubble clouds exposed to incoming pressure waves and the resulting pressure loads on a nearby rigid wall. The model simulates the two-phase medium as a continuum and solves the N-S equations using Eulerian grids with a time and space varying density. The microbubbles are modeled as interacting spherical bubbles, which follow a modified Rayleigh-Plesset-Keller-Herring equation and are tracked in a Lagrangian fashion. A two-way coupling between the Euler and Lagrange components is realized through the local mixture density associated with the bubbles volume change and motion. Using this numerical framework, simulations involving a large number of bubbles were conducted under driving pressures of different frequencies. The results show that the frequency of the driving pressure is critical in determining the overall dynamics: either a collective strongly coupled cluster behavior or non-synchronized weaker multiple bubble oscillations. The former creates extremely high pressures with peak values orders of magnitudes higher than that of the excitation pressures. This occurs when the driving frequency matches the natural frequency of the bubble cloud. The initial distance between the bubble cloud and the wall is also critical on the resulting pressure loads. A bubble cloud collapsing very close to the wall exhibits a cascading collapse with the bubbles farthest from the wall collapsing first and the nearest ones collapsing last, thus the energy accumulates and then results in very violent pressure peaks at the wall. Farther from the wall, the bubble cloud collapses quasi spherically with the cloud center collapsing last.
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Ghosh, Koushik, Achintya Mukhopadhyay, Swarnendu Sen, and Dipankar Sanyal. "An Integral Approach for Predicting Vapour Film Collapse and Growth Around a Hot Sphere in Subcooled Water." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-16261.

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The phase-change heat transfer has attracted researchers for its wide range of industrial applications like solidification in liquid containers, cooling of phase change material storage, combustion of spherical droplets and vapour explosion with associated film boiling and film collapse around molten drop in a coolant liquid. Major features of phase-change processes are heat transfer among multiple phases, mass transfer caused by latent heat of phase change and movement of phase interface. In present work a sphericosymmetric numerical model is developed to predict very rapid collapse of a vapour film around a hot melt immersed in a pool of subcooled water. The governing equations for the vapour film and the liquid were transformed into a number of non-linear ordinary differential equations by an integral approach assuming a quadratic temperature profile in both vapour and liquid domain while the melt was modelled as lumped mass. The energy balance across liquid vapour interface was incorporated by an equilibrium phase change model. The contribution of radiation from melt to the interface was considered assuming the vapour film to be non-participating. The non-linear ODE-s was solved by a fourth order Runge-Kutta method. The model was validated against some of the available solutions of liquid-vapour system. The present model shows excellent agreement in predicting growth of a solidification front in a saturated liquid (Stefan problem). The growth of a bubble in a superheated liquid was also validated with the available analytical solution. The results obtained from developed model for film collapse and growth around a hot melt in subcooled liquid were compared with a more accurate numerical model based on Volume of fluid method (VOF). It is found that the present model is able to capture successfully the rapid collapse of film due to condensation with computational time of one order less as compared to VOF based model. The film shows a very fast rebound (~ ms) due to faster condensation around liquid-vapour interface, following which a slower growth of vapour film is observed for different subcooling level.
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Alnaimat, Fadi, Omar Alhammadi, and Bobby Mathew. "Condensation Heat Transfer Model: A Comparison Study of Condensation Rate Between a Single Bubble and Multiple Rising Bubbles." In ASME 2021 Heat Transfer Summer Conference collocated with the ASME 2021 15th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/ht2021-63593.

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Abstract The main objective of this work is to develop a numerical model to analyze heat transfer and condensation of a rising spherical bubble. The model included the bubble shrinkage during condensation, which can be utilized to analyze the bubble’s total energy loss, raising velocity, and condensation rate of a single bubble compared to multiple bubbles with the same total thermal energy. The equations of motion, heat, and mass transfer were developed. The model results were verified with the bubble condensation experiment data in the literature, in which they exhibited a good agreement. For the validation, the model results were compared with bubble condensation experiment data in the literature, which showed a good agreement with the experimental results. The dynamic term of the model is developed using the force balance on a gravity-driven bubble, including hydrodynamic drag force and gravity/buoyancy force, which acting with and against the bubble’s motion direction. For the thermal part of the model, a condensation correlation has been adapted to represent the Nusselt number as a function of Reynolds number (Re), Jakob number (Ja), and Prandtl number (Pr). A MATLAB code is developed in order to calculate the instantaneous velocity, the radius, and the mass loss of the vapor bubble in each time step. Moreover, the fundamental behavior for a single bubble and multiple bubbles was investigated in various initial conditions under the same total thermal energy. The effects of the initial bubble radius and the temperature difference between the liquid and vapor phases were analyzed for both scenarios in order to examine the condensation rate. It was found that the thermal behavior of the condensing bubble can be improved by forcing the bubble to collapse into sub bubbles, which will increase the total interfacial area and the rising velocity. Farther, due to generated sub bubbles, the resultant velocity increased the turbulency and the heat transfer rate accordingly. This study can lead to improve the heat transfer rate and allow for more intensive research to enhance the condensation rate.
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Mostafa, Khaled, and Ahmed Alian. "Level 3 Fitness for Service Assessment of Dented Pipes With Diameter Less Than 6.25 Inch." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84935.

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Abstract The aim of this paper is to investigate the parameters affecting the structural integrity for piping with dents anomalies. As per the requirements to part 12 of the API 579-1/ASME FFS-1, 2016 [1], level 1 and 2 fitness for service (FFS) assessment procedures can’t be used for dented pipe with diameter less than 6.25 inch. Such small size pipes can only be assessed using level 3 assessment procedure. The pipe was indented in the FEA model with a rigid indenter. The indented pipe was then evaluated under general collapse and local failure criteria under different loading combinations using the elastic plastic analysis approach. The pipe material is defined using a multi-linear isotropic hardening model as per Annex 3-D of ASME BPVC, sec. VIII, div. 2 [2]. The effect of nominal pipe size, pipe schedule, and dent’s radius of curvature and depth on the plastic strain, and strain ratio are studied. Following Taguchi design of experiments methodology [5], a partial factorial design was adopted to allow the investigation of multiple levels value for each parameter. This analysis uses a real-life dent profile which was measured using automatic ultrasound inspection (AUT) and fitted to a spherical profile. The significance of each parameter on the different measured responses is evaluated.
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Wang, Ruimin, Fengde Zong, and Yang Yang. "Influence of Parametric Resonance on a Bubble Driven by Intensive Sound During Stable Cavitation." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68610.

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Ultrasonic cavitation is a well-known phenomenon that plays an important role in several physical systems and its applications are commonly utilized in different fields of physics and technology. The cavitation phenomena can be described by means of a field theory that should be able to predict the values of the macroscopic quantities, introducing physical parameters specifically for the bubbly liquid to be considered as a continuum; while on the other hand, the goal is to solve the problem of single bubble dynamics in an ultrasonic field as a starting point towards a multibubble theory. Usually the theory of single bubble dynamics in ultrasonic cavitation is constructed by primarily imposing the conditions of spherical symmetry on the bubble interface and a viscoelastic liquid, thus obtaining a significant simplification of the equations of motion and a single nonlinear equation for the interface. This approach can be satisfactory in several cases, but the situations in which the bubble deviates from its spherical shape (i.e. the collapse on a rigid boundary) and the problem of the stability of the interface motion, which turns out to be very important in sonoluminescence, cannot be treated by this theory. In the field of ultrasonic cavitation numerical analysis is a further means of investigation besides the analytical approach and experimental measurements, and it is necessary at least for two reasons. Specifically, an exact analytical treatment of the equations that model this phenomenon is substantially impossible due to their high nonlinearity; and furthermore the typical order of magnitude of the measurable quantities (object sizes in the range of microns, time intervals in the range of microseconds with nanosecond resolution) makes experiments difficult to perform. Hence we numerically analyze the relationships between amplitude and frequency by the use of SPECTRA PLUS software. The method is tested analyzing forced oscillations of cavitation bubbles excited by ultrasonic standing waves at different pressure amplitudes, showing characteristic behaviour of nonlinear dynamical systems; frequency spectra are obtained, stability analysis is performed. It is important to note that we observe subharmonic behaviour of the volume mode of the bubble prior to the instabilities due to shape modes. If one further increases the value of pressure amplitudes, one can clearly observe surface instabilities and deformations that lead to the destruction of the bubble. This evidence may suggest that the subharmonic behaviour leads to chaos in ultrasonic cavitation.
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