Modified Building Shapes for Reducing Vibrations of Tall Building

2013 ◽  
Vol 871 ◽  
pp. 3-8
Author(s):  
Ki Pyo You ◽  
Young Moon Kim ◽  
Jang Youl You
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Damping Ratio ◽  
Tall Building ◽  
The Other ◽  
Torsional Vibrations ◽  
Side Ratio ◽  
Building Models

To investigate the aerodynamic method for reducing motion induced vortex excitation as well as the galloping and torsional flutter of a tall building, We conducted wind tunnel tests on a tall building having a rectangular cross-section with a side ratio, D/B of 4.0 and aspect ratio of 10.0. Three aeroelastic building models were constructed to assess the effect of modified building shapes on the reduction of these vibrations. One is a plain model and the others are the shape-modified versions of the plain model, in which one has chamfered corners and the other has two openings at the top level. Experimental results showed that the chamfered model was more effective than model with the opening in reducing the above-mentioned types of vibrations, especially in motion induced vortex excitation, but not in reducing torsional vibration when the reduced velocity is high. Increasing the damping ratio might not be effective in reducing the bending and torsional vibrations of both the chamfered model and the model with openings when the reduced velocity is high.

Dependence of AC losses on aspect ratio in superconducting wires with rectangular cross section

2004 ◽  
Vol 412-414 ◽  
pp. 1045-1049 ◽  
Author(s):  
K. Kajikawa ◽  
T. Hayashi ◽  
K. Funaki ◽  
E.S. Otabe ◽  
T. Matsushita
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Ac Losses ◽  
Superconducting Wires

scholarly journals Behavior of reinforced concrete columns strenghtened by partial jacketing

2016 ◽  
Vol 9 (1) ◽  
pp. 1-21 ◽  
Author(s):  
D. B. FERREIRA ◽  
R. B. GOMES ◽  
A. L. CARVALHO ◽  
G. N. GUIMARÃES
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Concrete Columns ◽  
The Other ◽  
Self Compacting Concrete ◽  
Reinforced Concrete Columns ◽  
Compressive Stresses ◽  
Concrete Layer ◽  
Ultimate Resistance

This article presents the study of reinforced concrete columns strengthened using a partial jacket consisting of a 35mm self-compacting concrete layer added to its most compressed face and tested in combined compression and uniaxial bending until rupture. Wedge bolt connectors were used to increase bond at the interface between the two concrete layers of different ages. Seven 2000 mm long columns were tested. Two columns were cast monolithically and named PO (original column) e PR (reference column). The other five columns were strengthened using a new 35 mm thick self-compacting concrete layer attached to the column face subjected to highest compressive stresses. Column PO had a 120mm by 250 mm rectangular cross section and other columns had a 155 mm by 250mm cross section after the strengthening procedure. Results show that the ultimate resistance of the strengthened columns was more than three times the ultimate resistance of the original column PO, indicating the effectiveness of the strengthening procedure. Detachment of the new concrete layer with concrete crushing and steel yielding occurred in the strengthened columns.

scholarly journals Flow through a helical pipe with rectangular cross-section

1970 ◽  
Vol 4 (2) ◽  
pp. 99-110
Author(s):  
Md Mahmud Alam ◽  
Delowara Begum ◽  
K Yamamoto
Keyword(s):  
Aspect Ratio ◽  
Iterative Method ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Main Tool ◽  
Numerical Approach ◽  
Dean Number ◽  
Helical Pipe ◽  
Flow Through ◽  
Marine Engineering

The effects of torsion, aspect ratio and curvature on the flow in a helical pipe of rectangular cross- section are studied by introducing a non-orthogonal helical coordinate system. Spectral method is applied as main tool for numerical approach where Chebyshev polynomial is used. The numerical calculations are obtained by the iterative method. The calculations are carried out for 0≤ δ ≤0.02, 1≤ λ ≤ 2.85, 1≤ γ ≤2.4, at Dn = 50 & 100 respectively, where d is the non-dimensional curvature, l the torsion parameter, g the aspect ratio and  Dn the pressure driven parameter (Dean number).DOI: http://dx.doi.org/10.3329/jname.v4i2.991 Journal of Naval Architecture and Marine Engineering Vol.4(2) 2007 p.99-110

Influence of the 180° Bend Geometry on the Pressure Loss and Heat Transfer in a High Aspect Ratio Rectangular Smooth Channel

2004 ◽  
Author(s):  
Detlef Pape ◽  
Herve´ Jeanmart ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Flow Structures ◽  
Cooling Channel ◽  
Smooth Channel

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

The shape of a Möbius band

1993 ◽  
Vol 440 (1908) ◽  
pp. 149-162 ◽  
Keyword(s):  
Aspect Ratio ◽  
Asymptotic Solution ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Elastic Rods ◽  
Large Deflections ◽  
Mechanical Equilibrium ◽  
Elastic Rod ◽  
Flexible Material ◽  
Möbius Band

The shape of a Möbius band made of a flexible material, such as paper, is determined. The band is represented as a bent, twisted elastic rod with a rectangular cross-section. Its mechanical equilibrium is governed by the Kirchhoff–Love equations for the large deflections of elastic rods. These are solved numerically for various values of the aspect ratio of the cross-section, and an asymptotic solution is found for large values of this ratio. The resulting shape is shown to agree well with that of a band made from a strip of plastic.

A Numerical Study of Dean Instability in Non-Newtonian Fluids

2005 ◽  
Vol 128 (1) ◽  
pp. 34-41 ◽  
Author(s):  
H. Fellouah ◽  
C. Castelain ◽  
A. Ould El Moctar ◽  
H. Peerhossaini
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Power Law ◽  
Numerical Study ◽  
Rectangular Cross Section ◽  
Newtonian Fluids ◽  
Dean Number ◽  
Bingham Number ◽  
Curved Channels ◽  
Power Law Index

We present a numerical study of Dean instability for non-Newtonian fluids in a laminar 180deg curved-channel flow of rectangular cross section. A methodology based on the Papanastasiou model (Papanastasiou, T. C., 1987, J. Rheol., 31(5), pp. 385–404) was developed to take into account the Bingham-type rheological behavior. After validation of the numerical methodology, simulations were carried out (using FLUENT CFD code) for Newtonian and non-Newtonian fluids in curved channels of square or rectangular cross section and for a large aspect and curvature ratios. A criterion based on the axial velocity gradient was defined to detect the instability threshold. This criterion was used to optimize the grid geometry. The effects of curvature and aspect ratio on the Dean instability are studied for all fluids, Newtonian and non-Newtonian. In particular, we show that the critical value of the Dean number decreases with increasing curvature ratio. The variation of the critical Dean number with aspect ratio is less regular. The results are compared to those for Newtonian fluids to emphasize the effect of the power-law index and the Bingham number. The onset of Dean instability is delayed with increasing power-law index. The same delay is observed in Bingham fluids when the Bingham number is increased.

scholarly journals 1-D Modelling and 3-D Simulation of Confined Bubble Formation and Pressure Fluctuations During Flow Boiling in a Microchannel With a Rectangular Cross-Section of High Aspect Ratio

2009 ◽  
Author(s):  
S. Gedupudi ◽  
Y. Q. Zu ◽  
T. G. Karayiannis ◽  
D. B. R. Kenning ◽  
Y. Y. Yan
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Transient Flow ◽  
Flow Boiling ◽  
Rectangular Cross Section ◽  
Computing Time ◽  
Pressure Fluctuations ◽  
Design Tool ◽  
D Model

A simple 1-D model with low requirements for computing time is required to investigate parametric influences on the potentially adverse effects of pressure fluctuations driven by confined vapour bubble growth in microchannel evaporative cooling systems operating at high heat fluxes. A model is developed in this paper for the particular conditions of a channel of rectangular cross-section with high aspect ratio with a constant inlet flow rate (zero upstream compressibility). (The model will later be extended to the conditions of finite upstream compressibility that lead to transient flow reversal). Some parametric trends predicted by the model are presented. The simplifying assumptions in the model are examined in the light of a 3-D simulation by a commercial CFD code, described in an accompanying paper by the same authors. The predictions of pressure changes are in reasonable agreement. It is suggested that the 1-D model will be a useful design tool.

scholarly journals The steady propagation of a semi-infinite bubble into a tube of elliptical or rectangular cross-section

2002 ◽  
Vol 470 ◽  
pp. 91-114 ◽  
Author(s):  
ANDREW L. HAZEL ◽  
MATTHIAS HEIL
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Capillary Number ◽  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Scaling Law ◽  
Propagation Speed ◽  
Cross Sectional ◽  
Steady Propagation ◽  
Rectangular Tubes

This paper investigates the propagation of an air finger into a fluid-filled, axially uniform tube of elliptical or rectangular cross-section with transverse length scale a and aspect ratio α. Gravity is assumed to act parallel to the tube's axis. The problem is studied numerically by a finite-element-based direct solution of the free-surface Stokes equations.In rectangular tubes, our results for the pressure drop across the bubble tip, Δp, are in good agreement with the asymptotic predictions of Wong et al. (1995b) at low values of the capillary number, Ca (ratio of viscous to surface-tension forces). At larger Ca, Wong et al.'s (1995b) predictions are found to underestimate Δp. In both elliptical and rectangular tubes, the ratio Δp(α)/Δp(α = 1) is approximately independent of Ca and thus equal to the ratio of the static meniscus curvatures.In non-axisymmetric tubes, the air-liquid interface develops a noticeable asymmetry near the bubble tip at all values of the capillary number. The tip asymmetry decays with increasing distance from the bubble tip, but the decay rate becomes very small as Ca increases. For example, in a rectangular tube with α = 1.5, when Ca = 10, the maximum and minimum finger radii still differ by more than 10% at a distance 100a behind the finger tip. At large Ca the air finger ultimately becomes axisymmetric with radius r∞. In this regime, we find that r∞ in elliptical and rectangular tubes is related to r∞ in circular and square tubes, respectively, by a simple, empirical scaling law. The scaling has the physical interpretation that for rectangular and elliptical tubes of a given cross-sectional area, the propagation speed of an air finger, which is driven by the injection of air at a constant volumetric rate, is independent of the tube's aspect ratio.For smaller Ca (Ca < Ca), the air finger is always non-axisymmetric and the persisting draining flows in the thin film regions far behind the bubble tip ultimately lead to dry regions on the tube wall. Ca increases with increasing α and for α > αˆ dry spots will develop on the tube walls at all values of Ca.

Secondary Flow and Hydraulic Losses Within Sinuous Conduits of Rectangular Cross Section

1992 ◽  
Vol 114 (4) ◽  
pp. 593-600 ◽  
Author(s):  
Yukimaru Shimizu ◽  
Yoshiki Futaki ◽  
C. Samuel Martin
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Patterns ◽  
Geometric Configuration ◽  
Hydraulic Losses ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Relationship

This paper describes the relationship between hydraulic losses and secondary flow within sinuous conduits with complicated bends. It has been found that the nature of secondary flow present in the bends is quite sensitive to the geometric configuration of the bend and the actual aspect ratio of the conduit section. Indeed, many different secondary flow patterns have been found to exist as the bend geometry is altered. A wide range of experiments has been conducted for various aspect ratios of a rectangular conduit with different curvatures.

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