scholarly journals On the stability of von Kármán rotating-disk boundary layers with radial anisotropic surface roughness

2016 ◽  
Vol 28 (1) ◽  
pp. 014104 ◽  
Author(s):  
S. J. Garrett ◽  
A. J. Cooper ◽  
J. H. Harris ◽  
M. Özkan ◽  
A. Segalini ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Boundary Layers ◽  
Rotating Disk ◽  
Anisotropic Surface ◽  
Von Karman ◽  
The Stability ◽  
Von Kármán

scholarly journals The two-dimensional hydrodynamical theory of moving aerofoils. IV

1947 ◽  
Vol 188 (1015) ◽  
pp. 439-463
Keyword(s):  
Stability Problem ◽  
Two Dimensional ◽  
Centre Of Gravity ◽  
First Approximation ◽  
Von Karman ◽  
Moving Cylinder ◽  
Period Equation ◽  
The Stability ◽  
Von Kármán ◽  
Hydrodynamical Theory

In the first part of this paper opportunity has been taken to make some adjustments in certain general formulae of previous papers, the necessity for which appeared in discussions with other workers on this subject. The general results thus amended are then applied to a general discussion of the stability problem including the effect of the trailing wake which was deliberately excluded in the previous paper. The general conclusion is that to a first approximation the wake, as usually assumed, has little or no effect on the reality of the roots of the period equation, but that it may introduce instability of the oscillations, if the centre of gravity of the element is not sufficiently far forward. During the discussion contact is made with certain partial results recently obtained by von Karman and Sears, which are shown to be particular cases of the general formulae. An Appendix is also added containing certain results on the motion of a vortex behind a moving cylinder, which were obtained to justify certain of the assumptions underlying the trail theory.

Instabilities of the von Kármán Boundary Layer

2015 ◽  
Vol 67 (3) ◽  
Author(s):  
R. J. Lingwood ◽  
P. Henrik Alfredsson
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Direct Numerical Simulations ◽  
Layer Model ◽  
Complex Flow ◽  
Von Karman ◽  
Dimensional Boundary ◽  
Flow Configurations ◽  
Von Kármán

Research on the von Kármán boundary layer extends back almost 100 years but remains a topic of active study, which continues to reveal new results; it is only now that fully nonlinear direct numerical simulations (DNS) have been conducted of the flow to compare with theoretical and experimental results. The von Kármán boundary layer, or rotating-disk boundary layer, provides, in some senses, a simple three-dimensional boundary-layer model with which to compare other more complex flow configurations but we will show that in fact the rotating-disk boundary layer itself exhibits a wealth of complex instability behaviors that are not yet fully understood.

scholarly journals On the action of viscosity in increasing the spacing ratio of a vortex street

1936 ◽  
Vol 154 (881) ◽  
pp. 67-89 ◽  
Keyword(s):  
Viscous Fluid ◽  
Point Vortices ◽  
Vortex Street ◽  
Von Karman ◽  
Spacing Ratio ◽  
The Subject ◽  
The Stability ◽  
Von Kármán ◽  
The Ideal ◽  
Stable Vortex

1—von Kármán, by considering two parallel rows (of indefinite extent) of isolated, equal, point-vortices existing in a non-viscous fluid, has shown that the only stable vortex arrangement is the asymmetrical staggered one; and then only provided that the geometry of the system is such that h / a = 0·281, where h = width between the rows, and a = distance between consecutive vortices in one row. Since von Kármán’s investigation was published, writers on the subject have attempted to connect up the street with an obstacle producing it; and to investigate the effect of channel walls upon the stability and spacing ratio of the ideal street. At the same time efforts have been made to verify von Kármán’s spacing prediction by experiment, and to check the theoretical conclusions concerning the effect of parallel walls ;§ but the results have been far from satisfactory.

Symmetric Turbulent Mixing of Two Parallel Streams

1953 ◽  
Vol 20 (1) ◽  
pp. 63-71
Author(s):  
T. P. Torda ◽  
W. O. Ackermann ◽  
H. R. Burnett
Keyword(s):  
Experimental Data ◽  
Velocity Distribution ◽  
Boundary Layers ◽  
Turbulent Mixing ◽  
Energy Equation ◽  
Mixing Process ◽  
Analytical Results ◽  
Von Karman ◽  
Parallel Streams ◽  
Von Kármán

Abstract The analysis of turbulent, incompressible, symmetric mixing of two parallel streams is presented. The influence of the upstream boundary layers on the mixing process is taken into account. The von Kármán integral concept is applied to a momentum and energy equation. These equations are used to evaluate the thickness of the mixing region and the velocity distribution in it. The results are presented in nondimensional form. A numerical illustrative example is given. Comparison with Tollmien’s analytical results and with experimental data of Liepmann and Laufer is made.

Numerical Solutions for Radiative Heat Transfer in Ferrofluid Flow due to a Rotating Disk: Tiwari and Das Model

2018 ◽  
Vol 19 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. Mustafa ◽  
Junaid Ahmad Khan ◽  
T. Hayat ◽  
A. Alsaedi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Radiative Heat Transfer ◽  
Transfer Rate ◽  
Radiative Heat ◽  
Numerical Solutions ◽  
Rotating Disk ◽  
Von Karman ◽  
Von Kármán ◽  
Ferromagnetic Particles

AbstractIn this paper, we explore the von-Kármán infinite disk problem for the situation where ferrofluid resides in the space above the rotating disk. Furthermore, flow field is influenced by axial magnetic field. In this study, we treat water as the base fluid which consists of homogeneous suspensions of ${\rm{F}}{{\rm{e}}_{\rm{3}}}{{\rm{O}}_{\rm{4}}}$ ferromagnetic particles. The main motivation here is to resolve heat transfer problem in the existence of non-linear radiative heat transfer. With the aid of von-Kármán relations, the equations of fluid motion and heat transfer are changed into a set of self-similar differential equations. These equations are dealt by an implicit finite-difference method with high precision. The results reveal that wall heat transfer rate can be improved by increasing solid volume fraction of ferromagnetic particles. Drag coefficient at the disk and heat transfer rate are increased as the strength of Lorentz force is enhanced. Viscous dissipation effect has an important part in improving heart transfer process which is vital in some applications. The results demonstrate that cooling capability of magnetite–water nanofluid is much superior to the conventional coolants. An excellent correlation of present results with the previous published articles is found in the all the cases.

Double Row of Vortices with Arbitrary Stagger

1929 ◽  
Vol 25 (2) ◽  
pp. 132-138 ◽  
Author(s):  
L. Rosenhead
Keyword(s):  
Detailed Account ◽  
Double Row ◽  
Von Karman ◽  
Karman Street ◽  
The Stability ◽  
Von Kármán

The investigations of von Karman dealing with the unsymmetrical double row of vortices in an infinite sea of liquid are well known. He found that the unsymmetrical double row is stable when, and only when, cosh2πa/b = 2, where 2a is the distance between the two rows and 2b is the distance between consecutive vortices on the same row. A detailed account of the stability of the Karman street and of the symmetrical double row has been given by Lamb, and it has been shown that the symmetrical double row is unstable for all values of the ratio a/b. The object of this paper is to investigate the stability of a double row of vortices of arbitrary stagger. We define a double row of stagger 2l to be the system formed by positive vortices at the points (2nb + l, a) and negative vortices at (2mb − l, − a), where m and n assume all integral values from − ∞ to + ∞. The vortices are thus neither exactly “in step” nor exactly “out of step.” When l = 0 the system reduces to the symmetrical double row and when the system is the unsymmetrical double row.

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