Stability of steady rotation of a rotor about its vertical axis on hydrodynamic bearings

1987 ◽  
Vol 23 (12) ◽  
pp. 1189-1195
Author(s):  
N. V. Derendyaev ◽  
V. A. Senyatkin ◽  
V. M. Sandalov
Keyword(s):  
Vertical Axis ◽  
Hydrodynamic Bearings ◽  
Steady Rotation

Analysis of a rotating flow at small Reynolds number

1964 ◽  
Vol 18 (4) ◽  
pp. 499-512 ◽  
Author(s):  
Michael Bentwich
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Solid Cylinder ◽  
Navier Stokes Equations ◽  
Linear Partial Differential Equations ◽  
Method Of Solution ◽  
Steady Rotation ◽  
Physical Quantities

A solution of the Navier-Stokes equations is obtained for the flow resulting from the steady rotation of a semi-infinite right circular (solid) cylinder about its vertical axis. Incompressible viscous fluid is assumed to fill the space outside the cylinder on one side of a horizontal solid plane. In the proposed method of solution the pertinent physical quantities are expressed as series in positive powers of the Reynolds numberRewith space-dependent coefficients. It is shown that the coefficients of (Re)Mcan be obtained by solving linear partial differential equations which depend on the coefficients of (Re)i, wherei<M. A truncated solution, which holds for smallRe, is obtained by solving for the first two coefficients. These results indicate that at the flat end of the cylinder the pressure distribution is nearly constant, yet along the adjacent bounding plane it rises with the radial direction.

Turbulent rotating convection: an experimental study

2002 ◽  
Vol 458 ◽  
pp. 191-218 ◽  
Author(s):  
PETER VOROBIEFF ◽  
ROBERT E. ECKE
Keyword(s):  
Circulation Pattern ◽  
Vertical Axis ◽  
Temperature Fields ◽  
Convection Cell ◽  
Vortex Sheets ◽  
Rotation Rates ◽  
Global Circulation ◽  
Steady Rotation ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We present experimental measurements of velocity and temperature fields in horizontal planes crossing a cylindrical Rayleigh–Bénard convection cell in steady rotation about its vertical axis. The range of dimensionless rotation rates Ω is from zero to 5×104 for a Rayleigh number R = 3.2×108. The corresponding range of convective Rossby numbers is ∞ > Ro > 0.06. The patterns of velocity and temperature and the flow statistics characterize three basic flow regimes. For Ro [Gt ] 1, the flow is dominated by vortex sheets (plumes) typical of turbulent convection without rotation. The flow patterns for Ro ∼ 1 are cyclone-dominated, with anticyclonic vortices rare. As the Rossby number continues to decrease, the number of anticyclonic vortex structures begins to grow but the vorticity PDF in the vicinity of the top boundary layer still shows skewness favouring cyclonic vorticity. Velocity-averaging near the top of the cell suggests the existence of a global circulation pattern for Ro [Gt ] 1.

scholarly journals Flow Structure in a Rayleigh-Be´nard Cell Upon Impulsive Spin-Up

1998 ◽  
Vol 120 (4) ◽  
pp. 672-675
Author(s):  
Peter Vorobieff ◽  
Robert E. Ecke
Keyword(s):  
Regular Structure ◽  
Field Measurements ◽  
Vertical Axis ◽  
Thermochromic Liquid Crystal ◽  
Rotation Rates ◽  
Irregular Pattern ◽  
Image Velocimetry ◽  
Azimuthal Shear ◽  
Transient Feature ◽  
Steady Rotation

We investigate convection in a cylindrical Rayleigh-Be´nard cell with radius-to-height ratio Γ = 1/2. The cell is subjected to impulsive spin-up about its vertical axis. We use TLC (thermochromic liquid crystal) imaging for temperature field measurements and PIV (particle image velocimetry) for velocity reconstruction of the transition in the range of Rayleigh numbers R from 5 × 107 to 5 × 108 and dimensionless rotation rates Ω from 0 up to 8 × 104. The initial (at rest) and the final (in steady rotation) states of the system are those of turbulent convection. The most persistent transient feature is a well-defined ring pattern characterized by a decrease in temperature, axial velocity directed downward and high azimuthal shear. The latter leads to formation of an azimuthally regular structure of Kelvin-Helmholz vortices. During the final stage of the transition, this vortical structure loses azimuthal regularity and an irregular pattern of vortices characteristic of turbulent rotating convection forms.

Turbulent rotating convection at high Rayleigh and Taylor numbers

2010 ◽  
Vol 649 ◽  
pp. 509-522 ◽  
Author(s):  
J. J. NIEMELA ◽  
S. BABUIN ◽  
K. R. SREENIVASAN
Keyword(s):  
Heat Transport ◽  
Vertical Axis ◽  
Working Fluid ◽  
Rossby Number ◽  
Sharp Transition ◽  
Cryogenic Helium ◽  
Helium Gas ◽  
Steady Rotation ◽  
Parameter Ranges ◽  
Peak Value

We report heat transport measurements in a cylindrical convection apparatus rotating about the vertical axis. The aspect ratio was 1/2. The working fluid was cryogenic helium gas and the following parameter ranges applied: the Rayleigh number, Ra, varied in the range 1011 < Ra < 4.3 × 1015, the Taylor number, Ta, varied in the range 1011 < Ta < 3 × 1015, the convective Rossby number, Ro, varied in the range 0.4 < Ro < 1.6 and the Prandtl number, Pr, varied in the range 0.7 < Pr < 5.9. Boussinesq conditions applied quite closely. The heat transport for steady rotation, under all conditions of the present experiments, was smaller than that for the non-rotating case. When the rotation rate varied periodically in time, a sharp transition to a state of significantly enhanced heat transport was observed for modulation Taylor numbers Ta* ≳ 1014, where Ta* is based on the peak value of the modulation angular velocity.

Spatial Representations as an Emergent Feature of Perceptual Processing

2010 ◽  
Vol 24 (3) ◽  
pp. 161-172 ◽  
Author(s):  
Edmund Wascher ◽  
C. Beste
Keyword(s):  
Common Ground ◽  
Event Related Potentials ◽  
Vertical Axis ◽  
Relevant Information ◽  
Sources Of Information ◽  
Integrated Network ◽  
Perceptual Maps ◽  
Emergent Feature ◽  
Related Potentials ◽  
Selection Of

Spatial selection of relevant information has been proposed to reflect an emergent feature of stimulus processing within an integrated network of perceptual areas. Stimulus-based and intention-based sources of information might converge in a common stage when spatial maps are generated. This approach appears to be inconsistent with the assumption of distinct mechanisms for stimulus-driven and top-down controlled attention. In two experiments, the common ground of stimulus-driven and intention-based attention was tested by means of event-related potentials (ERPs) in the human EEG. In both experiments, the processing of a single transient was compared to the selection of a physically comparable stimulus among distractors. While single transients evoked a spatially sensitive N1, the extraction of relevant information out of a more complex display was reflected in an N2pc. The high similarity of the spatial portion of these two components (Experiment 1), and the replication of this finding for the vertical axis (Experiment 2) indicate that these two ERP components might both reflect the spatial representation of relevant information as derived from the organization of perceptual maps, just at different points in time.

Calculating the aerodynamics of vertical axis wind turbines

2012 ◽  
Vol 34 (3) ◽  
pp. 169-184 ◽  
Author(s):  
Hoang Thi Bich Ngoc
Keyword(s):  
Wind Turbine ◽  
Incidence Angle ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Velocity Triangle ◽  
Relationship Of ◽  
The Relationship

Vertical axis wind turbine technology has been applied last years, very long after horizontal axis wind turbine technology. Aerodynamic problems of vertical axis wind machines are discussible. An important problem is the determination of the incidence law in the interaction between wind and rotor blades. The focus of the work is to establish equations of the incidence depending on the blade azimuth, and to solve them. From these results, aerodynamic torques and power can be calculated. The incidence angle is a parameter of velocity triangle, and both the factors depend not only on the blade azimuth but also on the ratio of rotational speed and horizontal speed. The built computational program allows theoretically selecting the relationship of geometric parameters of wind turbine in accordance with requirements on power, wind speed and installation conditions.

SLOW STEADY ROTATION OF A POROUS SPHERE IN A SPHERICAL CONTAINER

2012 ◽  
Vol 15 (12) ◽  
pp. 1105-1110 ◽  
Author(s):  
D. Srinivasacharya ◽  
M. Krishna Prasad
Keyword(s):  
Porous Sphere ◽  
Steady Rotation ◽  
Spherical Container

Selection of Airfoils for Vertical Axis Wind Turbines for Low Speed, Low Altitude Regions of Central India

2017 ◽  
Vol 7 (11) ◽  
pp. 113
Author(s):  
Abhineet Singh ◽  
Sonali Mitra ◽  
S.V.H. Nagendra ◽  
Pragyan Jain
Keyword(s):  
Numerical Analysis ◽  
Central India ◽  
Vertical Axis ◽  
College Campus ◽  
Low Speed ◽  
Vertical Axis Wind Turbines ◽  
Low Altitude ◽  
Naca 0015 ◽  
Naca 0012 ◽  
Selection Of

The present paper deals with the selection of airfoil profile for VAWTs which is to be installed in the college campus, located in Central India region. Both experimental and numerical analysis he been carried out for the three selected airfoils, NACA 0012, NACA 0015 & S2027. The results show a good correlation with the existing literature. Airfoil profile S2027 has been chosen which best suits our condition. 

Design and Analysis of Vertical Axis Wind Turbine

2017 ◽  
Author(s):  
Prof. R.K. Bhoyar ◽  
Prof. S.J. Bhadang ◽  
Prof. N.Z. Adakane ◽  
Prof. N.D. Pachkawade
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine
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