scholarly journals Shear flows and their suppression at large aspect ratio: Two-dimensional simulations of a growing convection zone

2021 ◽  
Vol 6 (7) ◽  
Author(s):  
J. R. Fuentes ◽  
A. Cumming
Keyword(s):  
Aspect Ratio ◽  
Shear Flows ◽  
Convection Zone ◽  
Two Dimensional ◽  
Large Aspect Ratio

Mixed Convection in an Annulus of Large Aspect Ratio

1989 ◽  
Vol 111 (3) ◽  
pp. 683-689 ◽  
Author(s):  
L. S. Yao ◽  
B. B. Rogers
Keyword(s):  
Aspect Ratio ◽  
Mixed Convection ◽  
Channel Flow ◽  
Practical Interest ◽  
Base Flow ◽  
Two Dimensional ◽  
Large Aspect Ratio ◽  
Fully Developed Flow ◽  
The Stability ◽  
Stability Results

Mixed convection in an annulus of large aspect ratio is studied. At an aspect ratio of 100, the effect of wall curvature is minimal, and both the base flow and the stability characteristics approach those of a two-dimensional channel flow. The linear-stability results demonstrate that the fully developed flow is unstable in regions of practical interest in an appropriate parameter space. Consequently, commonly assumed steady parallel countercurrent flows in many idealized numerical and analytical studies are unlikely to be observed experimentally.

scholarly journals Aeroelastic instability of cantilevered flexible plates in uniform flow

2008 ◽  
Vol 611 ◽  
pp. 97-106 ◽  
Author(s):  
CHRISTOPHE ELOY ◽  
ROMAIN LAGRANGE ◽  
CLAIRE SOUILLIEZ ◽  
LIONEL SCHOUVEILER
Keyword(s):  
Aspect Ratio ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flexible Plate ◽  
Two Dimensional ◽  
Large Aspect Ratio ◽  
Flutter Instability ◽  
Flexible Plates ◽  
Plate Aspect Ratio

We address the flutter instability of a flexible plate immersed in an axial flow. This instability is similar to flag flutter and results from the competition between destabilizing pressure forces and stabilizing bending stiffness. In previous experimental studies, the plates have always appeared much more stable than the predictions of two-dimensional models. This discrepancy is discussed and clarified in this paper by examining experimentally and theoretically the effect of the plate aspect ratio on the instability threshold. We show that the two-dimensional limit cannot be achieved experimentally because hysteretical behaviour and three-dimensional effects appear for plates of large aspect ratio. The nature of the instability bifurcation (sub- or supercritical) is also discussed in the light of recent numerical results.

Shear damping of two-dimensional drift waves in a large-aspect-ratio tokamak

1979 ◽  
Vol 19 (9) ◽  
pp. 1223-1233 ◽  
Author(s):  
R.J. Hastie ◽  
K.W. Hesketh ◽  
J.B. Taylor
Keyword(s):  
Aspect Ratio ◽  
Drift Waves ◽  
Two Dimensional ◽  
Large Aspect Ratio ◽  
Shear Damping

Steady flow through distorted rectangular tubes of large aspect ratio

1983 ◽  
Vol 385 (1788) ◽  
pp. 107-127 ◽  
Keyword(s):  
Aspect Ratio ◽  
Boundary Layers ◽  
Rectangular Cross Section ◽  
Two Dimensional ◽  
Large Aspect Ratio ◽  
Dimensional Solution ◽  
Method Of Solution ◽  
Flow Through ◽  
High Reynolds ◽  
Sharp Corners

High Reynolds number ( Re ) flows through large aspect ratio ( λμ ) tubes of rectangular cross section are studied. One wall of the tube is slightly deformed to produce a two-dimensional distortion of length λ . We determine conditions for the flow at the centre of the tube and near the distortion to approximate the appropriate two-dimensional solution: namely, λμ ≫ ( λ -1 Re ) 1/6 if Re 1/7 ≲ λ and μ ≫ 1 if Re 1/7 ≳ λ . However, the latter condition needs to be strengthened to λμ ≫ Re 1/7 if the flow is additionally to be approximately two-dimensional far up- and down-stream. The method of solution includes a numerical calculation for the flow in the sharp corners of the tube. We deduce that for sufficiently short distortions ( λ ≪ Re 1/9 (ln Re ) 11/9 ), the sharp corners can effectively isolate disturbances in the wall boundary layers from each other. However, for larger distortions the disturbances in the boundary layers are all of comparable magnitude owing to interactions at the corners. Our examination of the corner regions also enables us to confirm a hypothesis, due to Hocking (1977) and others, that to leading order the pressure is constant in approximately square regions at the sides of the tube.

Large aspect ratio cells in two-dimensional thermal convection

1980 ◽  
Vol 51 (2) ◽  
pp. 370-380 ◽  
Author(s):  
J.M. Hewitt ◽  
D.P. McKenzie ◽  
N.O. Weiss
Keyword(s):  
Aspect Ratio ◽  
Thermal Convection ◽  
Two Dimensional ◽  
Large Aspect Ratio

Straight-Walled, Two-Dimensional Diffusers—Transitory Stall and Peak Pressure Recovery

1980 ◽  
Vol 102 (3) ◽  
pp. 275-282 ◽  
Author(s):  
J. Ashjaee ◽  
J. P. Johnston
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Mach Number ◽  
Aspect Ratio ◽  
Peak Pressure ◽  
Flow Direction ◽  
Prediction Method ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Large Aspect Ratio

Straight-walled, two-dimensional diffusers of large aspect ratio were investigated experimentally for the purpose of studying the regime of incipient transitory stall, the location of the geometry of peak diffuser pressure recovery. Twelve symmetric diffusers of constant nondimensional length (L/W1 = 15) with total included angles ranging from 4 to 24 degrees, covering attached, intermittently detaching, and unsteady detached flows were examined. Tests were run at one inlet blockage, 2δ1 / W1 = 0.027, and at an inlet Reynolds number of U1 W1/ν = 2.2 × 105 with air flow at low inlet Mach number. Pressure recovery and flow direction intermittency were obtained along the diffuser walls. An objective comparison of the UIM method of Ghose and Kline and an improved prediction method [Appendix] was performed with respect to these new experimental data. Some new conclusions are drawn concerning the nature of the flow in the vicinity of peak pressure recovery.

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