Transverse motion of an elastic sphere in a shear field

1973 ◽  
Vol 59 (1) ◽  
pp. 177-185 ◽  
Author(s):  
Christopher K. W. Tam ◽  
William A. Hyman
Keyword(s):  
Free Stream ◽  
Spherical Shape ◽  
Transverse Motion ◽  
Elastic Sphere ◽  
Shear Field ◽  
Elastic Particle ◽  
Small Deformations ◽  
Viscous Stresses ◽  
Stream Direction

The forces acting on an elastic particle suspended in a shear field, and moving relative to it, are found for the case in which there are small deformations from an initially spherical shape. The deformation is the result of the viscous stresses acting on the particle. Of principal interest is that there is a component of the force perpendicular to the free-stream direction, so that the particle will migrate across the undisturbed streamlines.

The Lift of Twisted and Cambered Wings in Supersonic Flow

1955 ◽  
Vol 6 (2) ◽  
pp. 149-163 ◽  
Author(s):  
G. N. Lance
Keyword(s):  
Integral Equation ◽  
Velocity Potential ◽  
Free Stream ◽  
Delta Wing ◽  
Complete Solution ◽  
Symmetric Potential ◽  
Leading Edges ◽  
Limiting Case ◽  
The Given ◽  
Stream Direction

SummaryA generalised conical flow theory is used to deduce an integral equation relating the velocity potential on a delta wing (with subsonic leading edges) to the given downwash distribution over the wing. The complete solution of this integral equation is derived. This complete solution is composed of two parts, one being symmetric and the other anti-symmetric with respect to the span wise co-ordinate; each part represents a velocity potential. For example, if y is the spanwise co-ordinate and x is measured in the free stream direction, then a downwash of the form w= - α11 Ux|y| is symmetric and will give rise to a symmetric potential, whereas w= - α11 Ux|y| sgn y is anti-symmetric and gives rise to an anti-symmetric potential. The velocity potentials of such flows are given in the form of Tables for all downwashes up to and including homogenous cubics in the spanwise and streamwise co-ordinates. Table III gives similar formulae in the limiting case when the leading edges become transonic; these are compared with results given elsewhere and serve as a check on the results of Tables I and II.

A numerical study of an inline oscillating cylinder in a free stream

2011 ◽  
Vol 688 ◽  
pp. 551-568 ◽  
Author(s):  
Justin S. Leontini ◽  
David Lo Jacono ◽  
Mark C. Thompson
Keyword(s):  
Vortex Shedding ◽  
Free Stream ◽  
Numerical Study ◽  
Dynamic Responses ◽  
Sinusoidal Oscillations ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Quasiperiodic Oscillations ◽  
Fixed Cylinder ◽  
Stream Direction

AbstractSimulations of a cylinder undergoing externally controlled sinusoidal oscillations in the free stream direction have been performed. The frequency of oscillation was kept equal to the vortex shedding frequency from a fixed cylinder, while the amplitude of oscillation was varied, and the response of the flow measured. With varying amplitude, a rich series of dynamic responses was recorded. With increasing amplitude, these states included wakes similar to the Kármán vortex street, quasiperiodic oscillations interleaved with regions of synchronized periodicity (periodic on multiple oscillation cycles), a period-doubled state and chaotic oscillations. It is hypothesized that, for low to moderate amplitudes, the wake dynamics are controlled by vortex shedding at a global frequency, modified by the oscillation. This vortex shedding is frequency modulated by the driven oscillation and amplitude modulated by vortex interaction. Data are presented to support this hypothesis.

Aerodynamics of oscillating disks and a right-circular cylinder

1967 ◽  
Vol 27 (1) ◽  
pp. 177-207 ◽  
Author(s):  
W. W. Willmarth ◽  
N. E. Hawk ◽  
A. J. Galloway ◽  
F. W. Roos
Keyword(s):  
Circular Cylinder ◽  
Unsteady Flow ◽  
Free Stream ◽  
Forced Oscillation ◽  
Random Excitation ◽  
The Body ◽  
Analogue Computer ◽  
Splitter Plates ◽  
Stream Direction ◽  
Axis Passing

Detailed studies are reported of the free and forced oscillation of disks and a right-circular cylinder constrained to rotate about a fixed diametrical axis passing through the centre of the body and normal to the free-stream direction. When a disk is free to rotate, it oscillates at a definite frequency with slowly varying amplitude and phase. A right-circular cylinder also oscillates at a definite frequency but with rapidly increasing amplitude. When the amplitude becomes large, after a few cycles of oscillation, the cylinder rotates steadily in one direction.Analogue computer elements, position sensors and a dynamic moment balance were used to study the static restoring moment, dynamic restoring moment, average damping moment, statistical properties of the disk motion and power spectrum of the turbulent moment. The behaviour of the disk and cylinder are explained using the measurements and the theory for random excitation of a linear system. The turbulent exciting moment is caused by the unsteady flow in the wake and can be changed by placing disks and splitter plates in the wake. A model is proposed for the unsteady flow field in the wake behind the disk. The model relates the turbulent moment to the vortex shedding process in the wake.

Dynamics of a deformable, transversely rotating droplet released into a uniform flow

2011 ◽  
Vol 684 ◽  
pp. 227-250 ◽  
Author(s):  
Eric K. W. Poon ◽  
Shaoping Quan ◽  
Jing Lou ◽  
Matteo Giacobello ◽  
Andrew S. H. Ooi
Keyword(s):  
Free Stream ◽  
Viscosity Ratio ◽  
Density Ratio ◽  
Spherical Shape ◽  
Droplet Deformation ◽  
Droplet Dynamics ◽  
Drag Coefficients ◽  
Rotational Rate ◽  
The Difference ◽  
Transverse Rotation

AbstractThe effects of transverse rotation on the dynamics of a droplet released into a uniform free stream are numerically investigated. The range of the dimensionless rotation rate is limited to $0\leq {\Omega }^{\ensuremath{\ast} } \leq 1$, to avoid any possibility of the droplet breaking up. Droplet dynamics and deformations undergo distinct changes when the dimensionless rotational rate $({\Omega }^{\ensuremath{\ast} } )$ reaches a critical value. The critical rotational rate ${{\Omega }_{crit} }^{\ensuremath{\ast} } $ is sensitive to the change in the density ratio, but less dependent on the viscosity ratio and interfacial tension. Below ${{\Omega }_{crit} }^{\ensuremath{\ast} } $, the droplet drag coefficients are reduced marginally as the effect of the rotation is quickly suppressed by the free stream. Above ${{\Omega }_{crit} }^{\ensuremath{\ast} } $, the drag coefficients decrease initially as the rotation effect dominates at earlier times, resulting in a global minimum. The drag coefficients increase monotonically at later times, when the rotation effects decrease and the free-stream effects become dominant. The only exception is with the increase in the viscosity ratio and the surface tension, which either inhibits droplet deformation or restores the droplet to a more spherical shape in the late stages of droplet evolution. The droplet also experiences lift due to the effects of the transverse rotation. It is observed that the lift coefficients are less dependent on the droplet frontal area as the lift is generated by the velocity difference between the upper and lower interface. In general, the lift coefficients increase with ${\Omega }^{\ensuremath{\ast} } $ at earlier times and decrease at later times as the difference in the velocity between the upper and lower interface decreases. In some extreme cases, the lift coefficients even become negative.

Influence of Mach Number and End Wall Cooling on Secondary Flows in a Straight Nozzle Cascade

1981 ◽  
Vol 103 (2) ◽  
pp. 257-263 ◽  
Author(s):  
C. H. Sieverding ◽  
Ph. Wilputte
Keyword(s):  
Experimental Study ◽  
Mach Number ◽  
Free Stream ◽  
Leading Edge ◽  
Main Flow ◽  
Secondary Flows ◽  
Blade Passage ◽  
Flow Pressure ◽  
End Wall ◽  
Stream Direction

This paper describes the results of an experimental study of the effect of Mach number and end wall cooling on the secondary flow in a straight nozzle cascade with an aspect ratio of h/c = 0.83. The tests were performed for the outlet Mach numbers M2 = 0.1, 0.6 and 0.8. The cooling tests are done for one specific cooling configuration consisting of three double rows of injection holes positioned at the leading edge, inside the blade passage and in the throat. The flow was injected into the direction of the free stream direction. The tests are carried out for two cooling mass flow ratios: m˙/m˙tot = 0.02 and 0.045. The corresponding injection to main flow pressure ratios are: 1.0, 1.16 for M2 = 0.6 and 1.0, 1.26 for M2 = 0.8. The flow surveys are made with three-directional pressure probes.

scholarly journals Influence of yaw on propeller aerodynamic characteristics

2018 ◽  
Vol 180 ◽  
pp. 02074
Author(s):  
Van Bang Nguyen ◽  
Dalibor Rozehnal ◽  
Jakub Hnidka ◽  
Vu Uy Pham
Keyword(s):  
Free Stream ◽  
Aerodynamic Characteristics ◽  
Yaw Angle ◽  
Thrust And Torque ◽  
Stream Direction ◽  
Propeller Thrust

Between the propeller axis and free stream direction, it can still be a non-zero yaw angle. This paper introduces some propeller experiments, in which the propeller aerodynamic characteristics have been determined in various yaw angle and different rotational speeds. The experimental aerodynamic characteristics are acquired dynamic values, from which the influence of yaw conditions on the frequency and the amplitude of propeller thrust and torque can be obtained.

Macrostructure and microphysics of Saturn's E-ring

1984 ◽  
Vol 75 ◽  
pp. 607-613 ◽  
Author(s):  
Kevin D. Pang ◽  
Charles C. Voge ◽  
Jack W. Rhoads
Keyword(s):  
Size Distribution ◽  
Spherical Shape ◽  
Mie Scattering ◽  
Narrow Size Distribution ◽  
Electrostatic Levitation ◽  
Volcanic Origin ◽  
Micron Diameter

Abstract.All observed optical and infrared properties of Saturn's E-ring can be explained in terms of Mie scattering by a narrow size distribution of ice spheres of 2 - 2.5 micron diameter. The spherical shape of the ring particles and their narrow size distribution imply a molten (possibly volcanic) origin on Enceladus. The E-ring consists of many layers, possibly stratified by electrostatic levitation.

On the Shape of Field-Ion Emitters

1976 ◽  
Vol 34 ◽  
pp. 520-521
Author(s):  
H.C. Eaton ◽  
B.N. Ranganathan ◽  
T.W. Burwinkle ◽  
R. J. Bayuzick ◽  
J.J. Hren
Keyword(s):  
Grain Boundary ◽  
Spherical Shape ◽  
Theoretical Strength ◽  
Evaporation Process ◽  
Field Evaporation ◽  
Geometric Information ◽  
Field Ion Microscopy ◽  
Considerable Error ◽  
True Shape ◽  
Ion Microscopy

The shape of the emitter is of cardinal importance to field-ion microscopy. First, the field evaporation process itself is closely related to the initial tip shape. Secondly, the imaging stress, which is near the theoretical strength of the material and intrinsic to the imaging process, cannot be characterized without knowledge of the emitter shape. Finally, the problem of obtaining quantitative geometric information from the micrograph cannot be solved without knowing the shape. Previously published grain-boundary topographies were obtained employing an assumption of a spherical shape (1). The present investigation shows that the true shape deviates as much as 100 Å from sphericity and boundary reconstructions contain considerable error as a result.Our present procedures for obtaining tip shape may be summarized as follows. An empirical projection, D=f(θ), is obtained by digitizing the positions of poles on a field-ion micrograph.

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