Experimental Study on Depositing Arch Jamming of Elliptical Disks in a Two-Dimensional Static Hopper

2016 ◽  
Vol 32 (6) ◽  
pp. 709-716 ◽  
Author(s):  
Y.-J. Lin ◽  
C. Fang
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Physical Mechanism ◽  
Force Chains ◽  
Two Dimensional ◽  
Strong Force ◽  
Aspect Ratios ◽  
Reverse Tendency ◽  
Opening Width

AbstractDepositing arch jamming of elliptical disks at the opening of a two-dimensional static hopper is studied experimentally. The hopper slope and opening width, and the aspect ratio of elliptical disks, are varied to determine their influence on the jamming probability. The jamming probability increases as the aspect ratio increases for gentle hopper slopes, while fluctuations of jamming probability appear for more steeper hopper slopes. Increasing hopper slope decreases the jamming probability in most cases. Most jamming arches result from the strong force chains along the shorter axes of elliptical disks. The disk number consisting of jamming arches decreases as the hopper slope increases. For smaller hopper openings, it decreases as the aspect ratio increases, whilst a nearly reverse tendency appears for elliptical disks with smaller aspect ratios. The study delivers a physical mechanism of jamming phenomena in depositing elliptical disks in a two- dimensional static hopper.

Yacht Keels - An Experimental Study

1975 ◽  
Author(s):  
Pierre DeSaix
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Center Of Gravity ◽  
Full Scale ◽  
Optimum Size ◽  
Hull Form ◽  
Size And Shape ◽  
Aspect Ratios ◽  
Current Design ◽  
Lateral Area

Model tests are presented for a series of nine keels; three aspect ratios, three sweep angles; all at constant lateral area, taper ratio and thickness ratio. The series is shown to bracket current design trends. These keels are all tested on the same canoe body, over a range of heel angles, lee-ways, and speeds. The results are presented in terms of full-scale sailing performance with due allowance for a reasonable ballast ratio and resulting vertical center of gravity for each keel. Optimum sweep angles for each aspect ratio are found. A second series of three keels, geometrically similar but varying in lateral area, is provided. Predictions of windward performance demonstrate the effect of keel size. An optimum size is found for three wind strengths. The results are for one hull form only. However, a method is suggested for estimating the effect of keel size and shape for any proposed design.

scholarly journals Linear biglobal analysis of Rayleigh–Bénard instabilities in binary fluids with and without throughflow

2012 ◽  
Vol 713 ◽  
pp. 216-242 ◽  
Author(s):  
Jun Hu ◽  
Daniel Henry ◽  
Xie-Yuan Yin ◽  
Hamda BenHadid
Keyword(s):  
Reynolds Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Critical Rayleigh Number ◽  
Two Dimensional ◽  
Binary Fluids ◽  
Transverse Modes ◽  
Aspect Ratios ◽  
Rayleigh Benard ◽  
Mode A

AbstractThree-dimensional Rayleigh–Bénard instabilities in binary fluids with Soret effect are studied by linear biglobal stability analysis. The fluid is confined transversally in a duct and a longitudinal throughflow may exist or not. A negative separation factor $\psi = \ensuremath{-} 0. 01$, giving rise to oscillatory transitions, has been considered. The numerical dispersion relation associated with this stability problem is obtained with a two-dimensional Chebyshev collocation method. Symmetry considerations are used in the analysis of the results, which allow the classification of the perturbation modes as ${S}_{l} $ modes (those which keep the left–right symmetry) or ${R}_{x} $ modes (those which keep the symmetry of rotation of $\lrm{\pi} $ about the longitudinal mid-axis). Without throughflow, four dominant pairs of travelling transverse modes with finite wavenumbers $k$ have been found. Each pair corresponds to two symmetry degenerate left and right travelling modes which have the same critical Rayleigh number ${\mathit{Ra}}_{c} $. With the increase of the duct aspect ratio $A$, the critical Rayleigh numbers for these four pairs of modes decrease and closely approach the critical value ${\mathit{Ra}}_{c} = 1743. 894$ obtained in a two-dimensional situation, one of the mode (a ${S}_{l} $ mode called mode A) always remaining the dominant mode. Oscillatory longitudinal instabilities ($k\approx 0$) corresponding to either ${S}_{l} $ or ${R}_{x} $ modes have also been found. Their critical curves, globally decreasing, present oscillatory variations when the duct aspect ratio $A$ is increased, associated with an increasing number of longitudinal rolls. When a throughflow is applied, the symmetry degeneracy of the pairs of travelling transverse modes is broken, giving distinct upstream and downstream modes. For small and moderate aspect ratios $A$, the overall critical Rayleigh number in the small Reynolds number range studied is only determined by the upstream transverse mode A. In contrast, for larger aspect ratios as $A= 7$, different modes are successively dominant as the Reynolds number is increased, involving both upstream and downstream transverse modes A and even the longitudinal mode.

An Experimental Study of Convective Heat Transfer in Radially Rotating Rectangular Ducts

1991 ◽  
Vol 113 (3) ◽  
pp. 604-611 ◽  
Author(s):  
C. Y. Soong ◽  
S. T. Lin ◽  
G. J. Hwang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotational Speed ◽  
Main Flow ◽  
Buoyancy Flow ◽  
Aspect Ratios

The paper presents an experimental study of convective heat transfer in radially rotating isothermal rectangular ducts with various height and width aspect ratios. The convective heat transfer is affected by secondary flows resulting from Coriolis force and the buoyancy flow, which is in turn due to the centrifugal force in the duct. The growth and strength of the secondary flow depend on the rotational Reynolds number; the effect of the buoyancy flow is characterized by the rotational Rayleigh number. The aspect ratio of the duct may affect the secondary flow and the buoyancy flow, and therefore is also a critical parameter in the heat transfer mechanism. In the present work the effects of the main flow, the rotational speed, and the aspect ratio γ on heat transfer are subjects of major interest. Ducts of aspect ratios γ=5, 2, 1, 0.5, and 0.2 at rotational speed up to 3000 rpm are studied. The main flow Reynolds number ranges from 700 to 20,000 to cover the laminar, transitional, and turbulent flow regimes in the duct flow. Test data and discussion are presented.

Out-of-plane behavior of confined masonry walls with aspect ratios greater than one

2021 ◽  
Vol 48 (1) ◽  
pp. 89-97
Author(s):  
Jorge Varela-Rivera ◽  
Joel Moreno-Herrera ◽  
Luis Fernandez-Baqueiro ◽  
Juan Cacep-Rodriguez ◽  
Cesar Freyre-Pinto
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Compressive Stress ◽  
Masonry Walls ◽  
Confined Masonry ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Axial Compressive Stress ◽  
Compressive Strut ◽  
Failure Line

An experimental study on the out-of-plane behavior of confined masonry walls is presented. Four confined walls with aspect ratios greater than one were tested in the laboratory. Walls were subjected to combined axial and out-of-plane uniform loads. The variables studied were the aspect ratio and the axial compressive stress of walls. It was observed that the out-of-plane strength of walls increased as the aspect ratio or the axial compressive stress increased. Failure of walls was associated with crushing of masonry. Analytical out-of-plane strength of walls was determined using the yielding line, failure line, modified yielding line, compressive strut and bidirectional strut methods. It was concluded that the experimental out-of-plane strength of walls was best predicted with the bidirectional strut method.

A bifurcation study of mixed-convection heat transfer in horizontal ducts

1991 ◽  
Vol 231 ◽  
pp. 157-187 ◽  
Author(s):  
K. Nandakumar ◽  
H. J. Weinitschke
Keyword(s):  
Aspect Ratio ◽  
Flow Structure ◽  
Solution Structure ◽  
Primary Branch ◽  
Two Dimensional ◽  
Solution Branch ◽  
Square Duct ◽  
Grashof Number ◽  
Aspect Ratios ◽  
Asymmetric Solution

The bifurcation structure of two-dimensional, pressure-driven flows through a horizontal, rectangular duet that is heated with a uniform flux in the axial direction and a uniform temperature around the periphery is examined. The solution structure of the flow in a square duct is determined for Grashof numbers (Gr) in the range of 0 to 106 using an arclength continuation scheme. The structure is much more complicated than reported earlier by Nandakumar, Masliyah & Law (1985). The primary branch with two limit points and a hysteresis behaviour between the two-and four-cell flow structure that was computed by Nandakumar et al. is confirmed. An additional symmetric solution branch, which is disconnected from the primary branch (or rather connected via an asymmetric solution branch), is found. This has a two-cell flow structure at one end, a four-cell flow structure at the other, and three limit points are located on the path. Two asymmetric solution branches emanating from symmetry-breaking bifurcation points are also found for a square duct. Thus a much richer solution structure is found with up to five solutions over certain ranges of Or. A determination of linear stability indicates that all two-dimensional solutions develop some form of unstable mode by the time Gr is increased to about 220000. In particular, the four-cell becomes unstable to asymmetric perturbations. The paths of the singular points are tracked with respect to variation in the aspect ratio using the fold-following algorithm. Transcritical points are found at aspect ratios of 1.408 and 1.456 respectively for Prandtl numbers Pr = 0.73 and 5. Above these aspect ratios the four-cell solution is no longer on the primary branch. Some of the fold curves are connected in such a way as to form a tilted cusp. When the channel cross-section is tilted even slightly (1°) with respect to the gravity vector, the bifurcation points unfold and the two-cell solution evolves smoothly as the Grashof number is increased. The four-cell solutions then become genuinely disconnected from the primary branch. The uniqueness range in Grashof number increases with increasing tilt, decreasing aspect ratio and decreasing Prandtl number.

Experimental Study on Vortex-Induced Vibration of Floating Circular Cylinders With Low Aspect Ratio

2014 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
André L. C. Fujarra
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Water Channel ◽  
Circular Cylinders ◽  
Structural Damping ◽  
End Effects ◽  
Vortex Induced Vibration ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Ratio Range

Experiments regarding vortex-induced vibration on floating circular cylinders with low aspect ratio were carried out in a recirculation water channel. The floating circular cylinders were elastic supported by a set of linear springs to provide low structural damping on the system. Eight different aspect ratios were tested, namely L/D = 0.2, 0.3, 0.4, 0.5, 0.75, 1.0, 1.5 and 2.0. These aspect ratios were selected to cover the aspect ratio range of the main offshore circular platforms, such as spar and monocolumn. The aims were understanding the VIM of such platforms; due to this, the cylinders were floating, or m* = 1. The range of Reynolds number covered 2,800 < Re < 55,400. The amplitude results showed a decrease in amplitude with decreasing aspect ratio in both directions. The frequency results confirm a different behavior for cylinders with L/D ≤ 0.5; in these cases, the cylinder free-end effects were predominant. The resonant behaviour was no longer observed for L/D ≤ 0.2. The decrease in Strouhal number with decreasing aspect ratio is also verified. All the results presented here complement the work presented previously for stationary circular cylinder with low aspect ratio presented by Gonçalves et al. (2013), Experimental Study on Flow around Circular Cylinders with Low Aspect Ratio, OMAE2013-10454.

A Method to Predict Rudder Stall Inception from Two-dimensional Airfoil Data

2014 ◽  
Vol 58 (01) ◽  
pp. 1-19
Author(s):  
Michael J. Hughes ◽  
Young T. Shen
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Theoretical Formulation ◽  
Stall Inception ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Flow Similarity ◽  
Naca 0015 ◽  
Naca 0012

The behavior of the force on a rudder changes significantly after the inception of stall, requiring different mathematical formulae to compute rudder forces prior-and poststall. Determining the inception angle at which stall occurs is important for predicting the rudder force on a maneuvering ship. A method to compute the inception angle of stall on a rudder is presented in this article. The theoretical formulation is based on a flow similarity approach, which relates three-dimensional rudder stall inception with two-dimensional airfoil data. Rudders are low-aspect ratio wings, and the three-dimensional lift is based on the low-aspect ratio wing theory. The two-dimensional airfoil stall data are obtained from National Advisory Committee for Aeronautics (NACA) reports. The derived theory is first validated with wind tunnel data from foils with a NACA 0015 profile of aspect ratios 1, 2, and 3. The theory is also validated with data from foils with a NACA 0012 profile and an aspect ratio of 2, 3, and 6.

An Experimental Study of Surface-Mounted Bluff Bodies Immersed in Deep Turbulent Boundary Layers

2018 ◽  
Author(s):  
Helen A. Amorin ◽  
Xingjun Fang ◽  
Mark F. Tachie
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Aspect Ratio ◽  
Water Channel ◽  
Open Water ◽  
Step Height ◽  
Bluff Bodies ◽  
Reynolds Stresses ◽  
Reattachment Length ◽  
Aspect Ratios

This paper reports an experimental study conducted to investigate the effects of aspect ratio on the reattachment length and statistical properties in turbulent flow over three-dimensional surface-mounted bluff bodies. This study focuses on a surface-mounted body whose height is significantly smaller than the thickness of the approaching turbulent boundary layer. The studied aspect ratios of the step range from w/h = 0.5 to 20, where w and h denote the spanwise width and height of the step, respectively. All experiments were carried out in an open water channel, and the velocity measurements were performed using a time-resolved particle image velocimetry (TR-PIV) system. The Reynolds number, based on the freestream of the approach boundary layer and step height, is 12540, while the ratio of the boundary layer to step height is 4.83. Two distinct regions of separation are observed on top of the step and downstream of the step. In both separation regions, the reattachment length increases monotonically as aspect ratio increases from w/h = 0.5 to 8, and the reattachment length reaches an asymptotic value and does not vary significantly with aspect ratio larger than 8. The effects of aspect ratios on the mean velocities and Reynolds stresses were also examined.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

Granular column collapses: further experimental results

2007 ◽  
Vol 575 ◽  
pp. 177-186 ◽  
Author(s):  
ERICA L. THOMPSON ◽  
HERBERT E. HUPPERT
Keyword(s):  
Aspect Ratio ◽  
Two Dimensional ◽  
Saturated Sand ◽  
General Applicability ◽  
Initial Height ◽  
Aspect Ratios ◽  
Water Saturated ◽  
Vertical Height ◽  
Initial Geometry ◽  
Granular Column

Experimental observations of the collapse of initially static columns of sand in axisymmetric and two-dimensional geometries are presented. The experiments were carried out using cylinders and rectangular tanks 30 to 60 cm tall, and cover aspect ratios between 0.5 and 20, where the aspect ratio is defined as the ratio of the initial height to horizontal extent of the column. The final positions of sand grains from different points initially on the outer surface of the columns are mapped. For all axisymmetric columns the point of maximum runout is found to originate from a point at fractional height 0.74 ± 0.03 of the initial vertical height of the column, independent of the aspect ratio. For two-dimensional columns the corresponding point is 0.65 ± 0.07. Collapses of columns of water-saturated sand into water display a different form of flow, which leads to there being no such well-defined point. In this case, grains from all but the innermost, basal areas of the initial column can end up in the outermost region of the final deposit. For collapses in air and aspect ratios greater than 1, the detail of the initial geometry is relatively insignificant in determining the shape of the final deposit. The results of this and previous studies thus have general applicability, even to situations with less initial symmetry. Movies are available with the online version of the paper.

Sign in / Sign up

Export Citation Format

Share Document