Comparative Study of Slamming Loads on Cylindrical Structures

2011 ◽  
Author(s):  
Kameswara S. Vepa ◽  
Diederik Van Nuffel ◽  
Wim Van Paepegem ◽  
Joris Degroote ◽  
Jan Vierendeels
Keyword(s):  
Composite Structures ◽  
Peak Pressure ◽  
The Other ◽  
Two Dimensional ◽  
Shell Elements ◽  
Cylindrical Structures ◽  
Deformable Cylinder ◽  
Implicit Solver ◽  
Explicit Solver ◽  
The Continuum

Wave impact or slamming is a phenomenon characterized by large local pressures (10 bar or more) for very short durations (order of milliseconds). Slamming loads can cause severe damage to the structure [1]. Different numerical approximation methods are available for simulating the fluid structure interaction problems. Traditional mesh techniques use nodes and elements for approximating the continuum equations whereas particle methods like smoothed particle hydrodynamics (SPH) approximates the continuum equations using the kernel approximation technique and hence can be used for a wide range of fluid dynamics problems [2]. Since composite materials are finding increased application in the ship building industry because of their low weight and high strength properties, it is important to understand the effect of slamming loads on composite structures [3]. Normally, composite structures are made quasi-rigid to resist slamming loads, but inducing some deformability helps in reducing the incident pressures and at the same time reduces the overall weight of the structure and in turn the material cost. On the other side, inducing deformability effects the durability of the structure. In this paper, the effect of slamming on two-dimensional cylindrical structures is studied using three solvers i.e., 1) SPH solver, 2) Explicit solver and 3) Implicit solver. In the case of SPH solver, water is modelled using SPH particles and cylinder is modelled using finite elements (FE), in this case shell elements. A coupling between the SPH and FE solvers is made to simulate the fluid-structure interactions. Contact is modelled using the contact algorithms. In the case of the explicit solver, water is modelled using hexahedron or brick elements with one element in the thickness direction since symmetry is applicable along the thickness of the cylinder. Shell elements are used for modelling the cylinder and contact is handled using node to surface contact algorithm. In the case of the implicit solver, water is represented by pure two-dimensional elements. Quadratic elements are used to represent the continuum around the cylinder and triangular elements are used to represent the far off field and also to control the mesh movement. Line elements are used to represent the cylinder in this case. Two models are tested in all the three solvers: 1) rigid cylinder and 2) deformable cylinder. A comparative study of these three solvers shows that the implicit solver needed more calculation time compared to other solvers. The SPH method required less particles than the number of nodes in the other two methods to converge on the peak pressure. All three solvers show reduction of peak pressure in case of the deformable cylinder.

scholarly journals Two-scale mathematics and fractional calculus for thermodynamics

2019 ◽  
Vol 23 (4) ◽  
pp. 2131-2133 ◽  
Author(s):  
Ji-Huan He ◽  
Fei-Yu Ji
Keyword(s):  
Fractional Calculus ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Dimensional Approach ◽  
One Dimensional ◽  
Fractal Calculus ◽  
Lower Dimensional ◽  
The Continuum

A three dimensional problem can be approximated by either a two-dimensional or one-dimensional case, but some information will be lost. To reveal the lost information due to the lower dimensional approach, two-scale mathematics is needed. Generally one scale is established by usage where traditional calculus works, and the other scale is for revealing the lost information where the continuum assumption might be forbidden, and fractional calculus or fractal calculus has to be used. The two-scale transform can approximately convert the fractional calculus into its traditional partner, making the two-scale thermodynamics much promising.

scholarly journals The exact analytical solution for the gas lubricated bearing in the slip and continuum flow regime

2012 ◽  
Vol 91 (105) ◽  
pp. 83-93 ◽  
Author(s):  
Nevena Stevanovic ◽  
Vladan Djordjevic
Keyword(s):  
Analytical Solution ◽  
Flow Rate ◽  
Gas Flow ◽  
Exact Analytical Solution ◽  
The Other ◽  
Two Dimensional ◽  
Lubrication Equation ◽  
Continuum Flow ◽  
Independent Variable ◽  
The Continuum

The exact analytical solution for the compressible two-dimensional gas flow in the microbearing is presented. The general slip-corrected Reynolds lubrication equation is derived and it is shown that it possesses an exact analytical solution. It is obtained by a suitable transformation of the independent variable, and it provides the pressure distribution in the bearing as well as the mass flow rate through it. By neglecting the rarefaction effect, this solution is also applicable to the continuum gas flow in the bearing, which also does not exist in the open literature. The obtained analytical solution can be usefully applied for testing the other, experimental or numerical results.

scholarly journals Mechanical interactions between adjacent airways in the lung

2014 ◽  
Vol 116 (6) ◽  
pp. 628-634 ◽  
Author(s):  
Baoshun Ma ◽  
Jason H. T. Bates
Keyword(s):  
Computational Model ◽  
Continuum Model ◽  
Network Models ◽  
The Other ◽  
Two Dimensional ◽  
Elastic Continuum ◽  
Spring Network Model ◽  
Triangular Network ◽  
One Airway ◽  
The Continuum

The forces of mechanical interdependence between the airways and the parenchyma in the lung are powerful modulators of airways responsiveness. Little is known, however, about the extent to which adjacent airways affect each other's ability to narrow due to distortional forces generated within the intervening parenchyma. We developed a two-dimensional computational model of two airways embedded in parenchyma. The parenchyma itself was modeled in three ways: 1) as a network of hexagonally arranged springs, 2) as a network of triangularly arranged springs, and 3) as an elastic continuum. In all cases, we determined how the narrowing of one airway was affected when the other airway was relaxed vs. when it narrowed to the same extent as the first airway. For the continuum and triangular network models, interactions between airways were negligible unless the airways lay within about two relaxed diameters of each other, but even at this distance the interactions were small. By contrast, the hexagonal spring network model predicted that airway-airway interactions mediated by the parenchyma can be substantial for any degree of airway separation at intermediate values of airway contraction forces. Evidence to date suggests that the parenchyma may be better represented by the continuum model, which suggests that the parenchyma does not mediate significant interactions between narrowing airways.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

1990 ◽  
Vol 48 (1) ◽  
pp. 258-259
Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Series Method ◽  
Three Dimensional Reconstruction ◽  
Structural Components ◽  
E Coli ◽  
Dimensional Reconstruction ◽  
Morphogenetic Factors ◽  
Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

The Continuum of Conscientiousness: The Antagonistic Interests among Obsessive and Antisocial Personalities

2014 ◽  
Vol 45 (2) ◽  
pp. 167-178 ◽  
Author(s):  
Steven C. Hertler
Keyword(s):  
Personality Disorder ◽  
Evolutionary Theory ◽  
Antisocial Personality Disorder ◽  
The Other ◽  
Antisocial Personality ◽  
Obsessive Compulsive ◽  
Demographic Differences ◽  
Other Hand ◽  
The Continuum

Abstract The five factor trait of conscientiousnessis a supertrait, denoting on one hand a pattern of excessive labor, rigidity, orderliness and compulsivity,and on the other hand a pattern of strict rectitude, scrupulosity, dutifulness and morality. In both respects the obsessive-compulsive personality is conscientious; indeed, it has been labeled a disorder of extreme conscientiousness (Widiger et al., 2009). Antisocial personality disorder, in the present paper, is described as occupying the opposite end of the conscientiousness continuum. The antisocial is impulsive rather than compulsive, illicit rather than licit, and furtive rather than forthright.After clinically comparing the obsessive and antisocial personalities, the present paper invokes evolutionary theory to explain their resultant behavioral, ideological, political and demographic differences.

On Commutation Properties of the Composition Relation of Convergent and Divergent Permutations (Part I)

2014 ◽  
Vol 58 (1) ◽  
pp. 13-22
Author(s):  
Roman Wituła ◽  
Edyta Hetmaniok ◽  
Damian Słota
Keyword(s):  
Finite Order ◽  
Convergent Series ◽  
The Other ◽  
Other Hand ◽  
The Family ◽  
Composition Relation ◽  
The Continuum

Abstract In the paper we present the selected properties of composition relation of the convergent and divergent permutations connected with commutation. We note that a permutation on ℕ is called the convergent permutation if for each convergent series ∑an of real terms, the p-rearranged series ∑ap(n) is also convergent. All the other permutations on ℕ are called the divergent permutations. We have proven, among others, that, for many permutations p on ℕ, the family of divergent permutations q on ℕ commuting with p possesses cardinality of the continuum. For example, the permutations p on ℕ having finite order possess this property. On the other hand, an example of a convergent permutation which commutes only with some convergent permutations is also presented.

Polymer-Graphene Nanoassemblies and their Applications in Cancer Theranostics

2020 ◽  
Vol 20 (11) ◽  
pp. 1340-1351 ◽  
Author(s):  
Ponnurengam M. Sivakumar ◽  
Matin Islami ◽  
Ali Zarrabi ◽  
Arezoo Khosravi ◽  
Shohreh Peimanfard
Keyword(s):  
Mechanical Stability ◽  
Chemical Properties ◽  
The Other ◽  
Hydrophilic Polymer ◽  
Two Dimensional ◽  
Normal Tissues ◽  
Physical Chemical ◽  
Anti Cancer ◽  
Good Biocompatibility ◽  
Cancer Theranostics

Background and objective: Graphene-based nanomaterials have received increasing attention due to their unique physical-chemical properties including two-dimensional planar structure, large surface area, chemical and mechanical stability, superconductivity and good biocompatibility. On the other hand, graphene-based nanomaterials have been explored as theranostics agents, the combination of therapeutics and diagnostics. In recent years, grafting hydrophilic polymer moieties have been introduced as an efficient approach to improve the properties of graphene-based nanomaterials and obtain new nanoassemblies for cancer therapy. Methods and results: This review would illustrate biodistribution, cellular uptake and toxicity of polymergraphene nanoassemblies and summarize part of successes achieved in cancer treatment using such nanoassemblies. Conclusion: The observations showed successful targeting functionality of the polymer-GO conjugations and demonstrated a reduction of the side effects of anti-cancer drugs for normal tissues.

scholarly journals On the Kirchhoff-Love Hypothesis (Revised and Vindicated)

2021 ◽  
Author(s):  
Olivier Ozenda ◽  
Epifanio G. Virga
Keyword(s):  
Free Energy ◽  
Dimension Reduction ◽  
Three Dimensional ◽  
Energy Functional ◽  
The Other ◽  
Variational Model ◽  
Two Dimensional ◽  
Elastic Plates ◽  
Kinematic Constraint ◽  
Free Energy Functional

AbstractThe Kirchhoff-Love hypothesis expresses a kinematic constraint that is assumed to be valid for the deformations of a three-dimensional body when one of its dimensions is much smaller than the other two, as is the case for plates. This hypothesis has a long history checkered with the vicissitudes of life: even its paternity has been questioned, and recent rigorous dimension-reduction tools (based on standard $\varGamma $ Γ -convergence) have proven to be incompatible with it. We find that an appropriately revised version of the Kirchhoff-Love hypothesis is a valuable means to derive a two-dimensional variational model for elastic plates from a three-dimensional nonlinear free-energy functional. The bending energies thus obtained for a number of materials also show to contain measures of stretching of the plate’s mid surface (alongside the expected measures of bending). The incompatibility with standard $\varGamma $ Γ -convergence also appears to be removed in the cases where contact with that method and ours can be made.

scholarly journals Long way to Ricci flatness

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Jin Chen ◽  
Chao-Hsiang Sheu ◽  
Mikhail Shifman ◽  
Gianni Tallarita ◽  
Alexei Yung
Keyword(s):  
Sigma Model ◽  
Ultra Violet ◽  
The Other ◽  
Target Space ◽  
Linear Sigma Model ◽  
Close Relative ◽  
Two Dimensional ◽  
World Sheet ◽  
Ricci Flat ◽  
The World

Abstract We study two-dimensional weighted $$ \mathcal{N} $$ N = (2) supersymmetric ℂℙ models with the goal of exploring their infrared (IR) limit. 𝕎ℂℙ(N,$$ \tilde{N} $$ N ˜ ) are simplified versions of world-sheet theories on non-Abelian strings in four-dimensional $$ \mathcal{N} $$ N = 2 QCD. In the gauged linear sigma model (GLSM) formulation, 𝕎ℂℙ(N,$$ \tilde{N} $$ N ˜ ) has N charges +1 and $$ \tilde{N} $$ N ˜ charges −1 fields. As well-known, at $$ \tilde{N} $$ N ˜ = N this GLSM is conformal. Its target space is believed to be a non-compact Calabi-Yau manifold. We mostly focus on the N = 2 case, then the Calabi-Yau space is a conifold. On the other hand, in the non-linear sigma model (NLSM) formulation the model has ultra-violet logarithms and does not look conformal. Moreover, its metric is not Ricci-flat. We address this puzzle by studying the renormalization group (RG) flow of the model. We show that the metric of NLSM becomes Ricci-flat in the IR. Moreover, it tends to the known metric of the resolved conifold. We also study a close relative of the 𝕎ℂℙ model — the so called zn model — which in actuality represents the world sheet theory on a non-Abelian semilocal string and show that this zn model has similar RG properties.

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