Coupled Wind-Induced Vibration Analysis of the Membrane Structure Based on Steady-State CFD

2011 ◽  
Vol 94-96 ◽  
pp. 598-605
Author(s):  
Xu Feng Sun ◽  
Shi Rong Li
Keyword(s):  
Steady State ◽  
Wind Velocity ◽  
Membrane Structure ◽  
Coupling Effect ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Reference Points ◽  
Response Distribution ◽  
The Mean ◽  
Wind Induced Vibration

Because of large flexibility and strong geometric nonlinearrity, the time domain method should be applied in the analysis of wind-induced vibration for the membrane structure, and the coupling effect between the structure and the fluid should also be considered. In this problem, it is hard now to solve it directly using the technique of three-dimensional transient FSI based on CFD. So in the article, a compromise schedule is proposed, i.e, for the mean wind part, the steady-state FSI technique is applied to solve the parameter such as the mean pressure coefficient, the mean wind velocity, etc, while for the fluctuating wind part, the time integral method is used based on the stochastic function of the wind velocity formed by auto regressive method. The aerodynamic damping is considered in the solving of fluctuating part and five computing schedule are compared, result shows that it is better to use positive mean wind damping for the nodes. It is also suggested that the stochastic wind velocity functuion can be revised based on the kinetic energy distribution of the reference points. A comparison between the computing and testing results show that it is greatly improved for the fluctuating response distribution of the structure.

Three-Dimensional, Steady-State Heat Conduction in Cylinders of General Anisotropic-Media

1979 ◽  
Vol 101 (3) ◽  
pp. 548-553 ◽  
Author(s):  
Y. P. Chang ◽  
K. C. Poon
Keyword(s):  
Heat Conduction ◽  
Steady State ◽  
Fourier Transforms ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Anisotropic Media ◽  
State Heat ◽  
Change Of Variables ◽  
Steady State Heat ◽  
Kummer's Equation

This paper provides the analytical solution of three-dimensional steady-state heat conduction in solid and hollow cylinders of general anisotropic-media. By the use of Fourier transforms and a change of variables the partial differential equation is reduced to Kummer’s equation. Some calculated results for a solid cylinder are shown and discussed. A parameter γ is found to represent the coupling effect of three-dimensional anisotropy. For small values of γ, an approximate solution is recommended. The inequality σ > 0 which was found in an earlier paper is further discussed.

scholarly journals TWO-PHASE MODELLING OF THERMAL DISSIPATION IN A NATURAL BASIN

2004 ◽  
Vol 12 (3) ◽  
pp. 103-107 ◽  
Author(s):  
Pranas Baltrenas ◽  
Petras Vaitiekūnas ◽  
Vladislovas Katinas ◽  
Antanas Markevičius
Keyword(s):  
Heat Transfer ◽  
Wind Velocity ◽  
Three Dimensional ◽  
Viscosity Coefficient ◽  
Thermal Dissipation ◽  
Stream Velocity ◽  
Mixing Rate ◽  
Two Phase ◽  
Transfer Processes ◽  
The Mean

The state of two‐phase flow ‘liquid‐gas’ has been modeled numerically by the three‐dimensional method of complex research of heat and mass transfer. This allows examining the interaction of some transfer processes in a natural cooling basin (the Drūkšiai lake): the wind power and direction, variable water density, the coefficient of heat conduction and heat transfer of the water‐air interface. Combined effect of these natural actions determines the heat amount that the basin is able to dissipate to the surrounding atmospheric media in thermal equilibrium (without changes in the mean water temperature). This paper presents a number of the most widely used expressions for the coefficients of vertical and horizontal heat transfer. On the basis of stream velocity and mean temperature profiles measured in the cooling pond as well as on that of their time variations suggestions are made that the mixing rate at the water surface is caused by natural space ‐ time variation of the wind, and can be described by the value of eddy viscosity coefficient ‐ 1 m2/s (numerical modeling with 0,9–1,3 m2/s). The wind influences the surface of the lake according to the experimental data, i e 1–3 % of the mean wind velocity. The model applies to the weakly wind, approximately 1–5 m/s of the mean wind velocity. Comparison of experimental and numerical results showed a qualitative agreement. For a better quantitative approximation, it is necessary to have more boundary conditions variable with time and to solve unsteady set equations for transfer processes.

Heat Transfer Normal to Paired Arterioles and Venules Embedded in Perfused Tissue During Hyperthermia

1988 ◽  
Vol 110 (4) ◽  
pp. 277-282 ◽  
Author(s):  
C. K. Charny ◽  
R. L. Levin
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Three Dimensional ◽  
Numerical Data ◽  
Tissue Temperature ◽  
Three Dimensional Model ◽  
Sources And Sinks ◽  
The Mean ◽  
Krogh Cylinder ◽  
Subsequent Incorporation

A numerical model of the heat transer normal to an arteriole-venule pair embedded in muscle tissue has been constructed. Anatomical data describing the blood vessel size, spacing, and density have been incorporated into the model. This model computes temperatures along the vessel walls as well as the temperature throughout the tissue which comprises an infinitely long Krogh cylinder around the vessel pair. Tissue temperatures were computed in the steady-state under resting conditions, while transient calculations were made under hyperthermic conditions. Results show that for both large- (1st generation) and medium-sized (5th generation) vessel pairs, the mean tissue temperature within the tissue cylinder is not equal to the mean of the arteriole and venule blood temperatures under both steady-state and transient conditions. The numerical data were reduced so that a comparison could be made with the predictions of a simple two-dimensional superposition of line sources and sinks presented by Baish et al. [1]. This comparison reveals that the superposition model accurately describes the heat transfer effects during hyperthermia, permitting subsequent incorporation of this theory into a realistic three-dimensional model of heat transfer in a whole limb during hyperthermia.

scholarly journals Investigating the effect of bruxism on maxillary arch length and width in children using three-dimensional digital model analysis

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Ebru Hazar Bodrumlu ◽  
Fethiye Çakmak Özlü ◽  
Hakan Yılmaz ◽  
Levent Demiriz
Keyword(s):  
Three Dimensional ◽  
Study Groups ◽  
Model Analysis ◽  
Reference Points ◽  
Digital Model ◽  
Digital Models ◽  
Study Results ◽  
Insignificant Difference ◽  
The Mean ◽  
Maxillary Arch

Abstract Background Bruxism is defined as repetitive jaw-muscle activity characterized by the grinding and clenching of teeth. The prevalence of bruxism in children is extensive, and it can cause irregularities in dental arches. The study aimed to investigate the presence of any effects of bruxism on maxillary arch length and width in children using three-dimensional (3D) digital model analysis. Method This study evaluated 30 children with bruxism. For every child with bruxism, a case control without bruxism was selected and matched for gender, age, and dentition. Digital models of the patients’ maxilla were obtained with a 3D intraoral scanner, and width and length measurements between the reference points on the maxilla were obtained on the digital models. Results The mean age of the study group was 9.13 ± 1.27. Insıgnificance differences were found between females and males within and between groups in terms of maxillary width and length. Insignificant difference was found between the control and study groups when the lengths of 3R-3L, 4R-4L, 5R-5L, 6R-6L, and IP-M were compared (p > 0.05). Conclusion Based on the study results, there were no differences in the maxillary arch length and width in patients with bruxism and patients without bruxism.

scholarly journals Modeling combinations of antiretroviral agents in vitro with integration of pharmacokinetics: guidance in regimen choice for clinical trial evaluation.

1996 ◽  
Vol 40 (5) ◽  
pp. 1143-1147 ◽  
Author(s):  
G L Drusano ◽  
M Prichard ◽  
P A Bilello ◽  
J A Bilello
Keyword(s):  
Drug Interaction ◽  
Steady State ◽  
Continuous Infusion ◽  
Three Dimensional ◽  
Pharmacokinetic Profile ◽  
Maximal Effect ◽  
Direct Evaluation ◽  
Average Percentage ◽  
The Mean

We propose a method for the selection of doses and dosing schedule for drugs to be used in combination. This approach uses the simulation of steady-state concentrations of the drugs in the combination and overlays these concentrations onto a three-dimensional effect surface. The MacSynergy II program is used to construct the three-dimensional drug interaction surface from the direct evaluation of drug combination effect in vitro. The study examined the combination of an inhibitor of the human immunodeficiency virus protease, A-77003, and the nucleoside analog zidovudine. Zidovudine concentrations from a steady-state interval were simulated on the basis of the administration of 100 mg every 12 h by mouth, while for A-77003 simulation profiles were for intravenous administration of 800 mg every 4 h as well as a continuous infusion of 200 mg/h. The average percentage of the maximal effect was taken as a measure of regimen effectiveness. Three different schedules of administration were examined. If both drugs were to be administered simultaneously, the model predicts a mean maximal effect of a steady-state interval (12 h) of 67%. If the drug doses were offset by 2 h, the mean maximal effect predicted was 71%. If A-77003 was to be given by continuous infusion, the mean maximal effect predicted was 90%. This method holds promise as a way of quickly evaluating potential combinations of agents that takes into account the drug interaction in a mathematically robust way and that allows the evaluation of the effect of each drug's pharmacokinetic profile.

Cavitation in the rotational structures of a turbulent wake

1995 ◽  
Vol 287 ◽  
pp. 383-403 ◽  
Author(s):  
B. Belahadji ◽  
J. P. Franc ◽  
J. M. Michel
Keyword(s):  
Pressure Coefficient ◽  
Three Dimensional ◽  
Turbulent Wake ◽  
Streamwise Vortices ◽  
Near Wake ◽  
Absolute Value ◽  
Cavitation Inception ◽  
Wake Vortices ◽  
Mean Pressure ◽  
The Mean

Experiments show that cavitation, if moderately developed, makes three kinds of vortical coherent structures visible inside the turbulent wake of a two-dimensional obstacle: Bénard–Kármán vortices, streamwise three-dimensional vortices and finally the vortices which appear on the borders of the very near wake. The latter, which are called here near-wake vortices, result by successive pairing in the first ones and there is some indication that they are also the origin of streamwise vortices. Cavitation is not a passive agent of visualization, as can be established on the basis of fundamental arguments, and it reacts with the flow as soon as it appears; when it is developed, it breaks the connection between the elongation rate and the vorticity rate of the vortex filaments. Then the subsequent evolution of a cavitating vortex and its final implosion are rather complicated. Despite its active character, cavitation in rotational structures, if properly interpreted, can give information of interest on the basic non-cavitating turbulent flow. By adapting a simple model due to Kermeen & Parkin (1957) and Arndt (1976), and counting near-wake vortices, it is possible to accurately predict the conditions of cavitation inception: consideration of coherent rotational structures is probably the best approach to explain, in an almost deterministic way, the large difference between the absolute value of the mean pressure coefficient at the obstacle base and the incipient cavitation number.

scholarly journals A three-dimensional model for rain-wind induced vibration of stay cables in cable-stayed bridges

2019 ◽  
Vol 14 (1) ◽  
pp. 89-102
Author(s):  
Truong Viet Hung ◽  
Vu Quang Viet ◽  
Vu Quoc Anh
Keyword(s):  
Wind Velocity ◽  
Three Dimensional ◽  
Stay Cable ◽  
Three Dimensional Model ◽  
Central Difference ◽  
Theoretical Formulation ◽  
Wind Speed Profile ◽  
Stay Cables ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

In this paper, the effects of wind velocity according to height above the ground on the rain-wind induced vibration (RWIV) of stay cables are investigated. RWIV of the cable is modeled using the linear theory of cable vibration and the central difference algorithm. The wind speed profile according to height above the ground, which affects both aerodynamic forces acting on the cable and the oscillation of the rivulet on the cable surface, is taken into account in the theoretical formulation. The fourth-order method Runge-Kutta is used for solving the system of differential equation of the cable oscillation. The proposed 3D model of the stay cable is then used to assess the effects of wind velocity distribution on cable RWIV. The results obtained in this study showed that in most current cable-stayed bridges, in which the height of pylons is lower than 200 m, the change of wind velocity according to the height above the ground should be included in RWIV analyses. Keywords: stay cable; rain - wind induced vibration; rivulet; analytical model; vibration.

Electron Holographic Nano-Characterization of Gold Catalyst at Interface

2002 ◽  
Vol 727 ◽  
Author(s):  
S. Ichikawa ◽  
T. Akita ◽  
M. Okumura ◽  
M. Haruta ◽  
K. Tanaka
Keyword(s):  
Contact Angle ◽  
Titanium Oxide ◽  
Gold Catalyst ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Electron Holography ◽  
Gold Particles ◽  
Oxide Support ◽  
The Mean ◽  
A Charge

AbstractThe catalytic properties of nanostructured gold catalyst are known to depend on the size of the gold particles and to be activated when the size decreases to a few nanometers. We investigated the size dependence of the three-dimensional nanostructure on the mean inner potential of gold catalysts supported on titanium oxide using electron holography and high-resolution electron microscopy (HREM). The contact angle of the gold particles on the titanium oxide tended to be over 90° for gold particles with a size of over 5 nm, and below 90° for a size of below 2 nm. This decreasing change in the contact angle (morphology) acts to increase the perimeter and hence the area of the interface between the gold and titanium oxide support, which is considered to be an active site for CO oxidation. The mean inner potential of the gold particles also changed as their size decreased. The value of the inner potential of gold, which is approximately 25 V in bulk state, rose to over 40 V when the size of the gold particles was less than 2 nm. This phenomenon indicates the existence of a charge transfer at the interface between gold and titanium oxide. The 3-D structure change and the inner potential change should be attributed to the specific electronic structure at the interface, owing to both the “nano size effect” and the “hetero-interface effect.”

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