The motion of a prolate ellipsoid in a rotating Stokes flow

2007 ◽  
Vol 583 ◽  
pp. 123-132 ◽  
Author(s):  
J. R. T. SEDDON ◽  
T. MULLIN
Keyword(s):  
Stokes Flow ◽  
Flow Model ◽  
Vertical Wall ◽  
Viscous Drag ◽  
Experimental Investigations ◽  
Radius Of Curvature ◽  
Fixed Position ◽  
Close Proximity ◽  
Limiting Case ◽  
Cylinder Rotation

Results are presented from experimental investigations into the motion of a heavy ellipsoid in a horizontal rotating cylinder, which has been completely filled with highly viscous fluid. The motion can be conveniently classified using the ratio between the maximum radius of curvature of the ellipsoid κmax and the radius of the drum Rd. If κmax < Rd the ellipsoid adopts a fixed position adjacent to the rising wall for a given cylinder rotation rate. The dependence of this position on wall speed is, surprisingly, independent of the ellipsoid's length, and a Stokes flow model has been developed which predicts both this independence and the speed for the limiting case of an ellipsoid adjacent to a vertical wall. If κ max < Rd the ellipsoid must tilt in order to maintain the maximum surface area in close proximity to the wall. Once tilted, a component of the viscous drag acts to laterally translate the ellipsoid from end to end of the drum. The ellipsoid with κmax = Rd adopts a series of fixed positions for most drum rotational rates but, between two regions of fixed-point behaviour, it undergoes a transition to oscillatory motion.

Instabilities and Transition to Chaos in Flows between Concentric Cylinders

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Aomar Ait Aider
Keyword(s):  
Visual Observation ◽  
Experimental Investigations ◽  
Flow Measurements ◽  
Dean Flow ◽  
Concentric Cylinders ◽  
Computational Fluid Dynamics Analysis ◽  
Long Time ◽  
Taylor Couette ◽  
Geometrical Effects ◽  
Cylinder Rotation

How does turbulence rise? For a long time, a century, the Taylor-Couette system was a paradigm for the researchers who tried to get answers to this question. Fascinating structures and patterns observed in the flow have attracted the interest of many researchers, both experimentalists and theorists. During the last century, many works were done on the closed Taylor-Couette systems. At the end of the seventies, after thousands of contributions, experiments performed in the Taylor-Couette system confirmed a theoretical analysis which concluded that a finite number of instabilities, two or three, are sufficient to lead to chaos or weak turbulence. Our own experiments were conducted at that time on a Taylor-Couette system with a moderate aspect ratio. They were analyzed from visual observation and fine local measurement with an electrochemical method. Scalar time series and data pointed out the frequencies characteristic of the flow. Many geometrical effects are considered by researchers. When the gap is horizontal and not completely filled, the flow obtained is called Taylor-Dean flow. We obtained similar flow in an azimuthally open Taylor-Couette system where a combination of the inner cylinder rotation and external fluid pumping, the Dean flow, produces the so called Taylor-Dean flow. Measurements and analysis were carried out by visualization and Laser Doppler Velocimetry. In addition to the experimental approach, we used Computational Fluid Dynamics analysis to complete the flow study. Numerical and experimental investigations reveal a class of instabilities of the Taylor-Dean flow not previously observed in the Taylor-Couette flow due to the cylinder rotation neither in the Dean flow due to the external pumping fluid.

Determination of Brinkman Model Parameters Using Stokes Flow Model

2019 ◽  
Vol 130 (2) ◽  
pp. 529-557 ◽  
Author(s):  
S. K. Zaripov ◽  
R. F. Mardanov ◽  
V. F. Sharafutdinov
Keyword(s):  
Stokes Flow ◽  
Flow Model ◽  
Model Parameters ◽  
Brinkman Model

The Effect of Heater Size, Location, Aspect Ratio, and Boundary Conditions on Two-Dimensional, Laminar, Natural Convection in Rectangular Channels

1976 ◽  
Vol 98 (2) ◽  
pp. 194-201 ◽  
Author(s):  
H. H.-S. Chu ◽  
S. W. Churchill ◽  
C. V. S. Patterson
Keyword(s):  
Vertical Wall ◽  
Alternating Direction Implicit ◽  
Aspect Ratios ◽  
Alternating Direction ◽  
Rectangular Channels ◽  
Wide Range ◽  
Localized Heating ◽  
Laminar Natural Convection ◽  
Lower Temperature ◽  
Limiting Case

The effect of localized heating in rectangular channels was studied by solving the partial differential equations for the conservation of mass, momentum, and energy numerically using an unsteady state formulation and the alternating-direction-implicit method. The heating element was a long, horizontal, isothermal strip located in one, otherwise-insulated vertical wall. The opposing wall was maintained at a lower uniform temperature and the upper and lower surfaces were insulated or maintained at the lower temperature. Computations were carried out for Pr = 0.7, 0 ≤ Ra ≤ 105, a complete range of heater widths and locations and a wide range of aspect ratios. Flow visualization studies and comparison with prior computed results for a limiting case confirm the validity of the computed values. The computed rates of heat transfer and circulation provide guidance for locating heaters or coolers.

A FLOW MODEL AND ANALYSIS OF A ROCKET PAIR IN CLOSE PROXIMITY

1965 ◽  
Author(s):  
Hugh A. Thompson ◽  
Henry F. Hrubecky
Keyword(s):  
Flow Model ◽  
Close Proximity

Numerical and Experimental Investigations of Momentum and Heat Transfer in Microchannels

2008 ◽  
Author(s):  
M. Favre-Marinet ◽  
S. Drobniak ◽  
D. Asendrych ◽  
G. Gamrat ◽  
M. Niklas
Keyword(s):  
Heat Transfer ◽  
Hydraulic Properties ◽  
Flow Model ◽  
Experimental Investigations ◽  
Microchannel Flow ◽  
The Third ◽  
Numerical Studies ◽  
Continuum Flow ◽  
Momentum And Heat Transfer

The paper presents the results of a research performed during recent years at LEGI Grenoble with joint participation of CzUT researchers. The special attention is devoted to experimental and numerical studies devoted to three cases involving various aspects of microchannel flow physics (range of microchannel sizes corresponds to the classification of Kandlikar [19]). The first aspect is related to hydraulic properties of a network of parallel triangular microchannels, where experimental investigations revealed the rapid increase of pressure drop for Re exceeding value of 10. The second aspect of the research was the influence of surface roughness, which was investigated both experimentally and numerically for periodically and randomly distributed surface elements. The third research case was devoted to the numerical modelling of heat transfer. As a result, experimental and numerical analyses showed that there was no scale effect for the microchannels considered, i.e. the relevance of the classical continuum flow model was confirmed.

Experimental investigation of porous materials for trailing-edge noise reduction

2020 ◽  
Vol 19 (6-8) ◽  
pp. 365-384
Author(s):  
K-S Rossignol ◽  
A Suryadi ◽  
M Herr ◽  
J Schmidt ◽  
J Tychsen
Keyword(s):  
Wind Tunnel ◽  
Noise Reduction ◽  
Porous Materials ◽  
Active Flow Control ◽  
Acoustic Emissions ◽  
Experimental Investigations ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Tunnel Model ◽  
Close Proximity

The introduction of quiet short take-off and landing for civil aircraft operations in close proximity to the population poses important technological challenges. One critical aspect is the realization of extreme lift augmentation at low acoustic emissions. The aircraft concept selected to achieve this goal is a high-lift system equipped with an active flow-control non-slotted flap and a droop nose. For this specific configuration, trailing edge noise becomes a dominant noise source. Porous materials as a passive means for trailing-edge noise reduction are selected and characterized. Results of extensive experimental investigations in the acoustic wind tunnel Braunschweig are presented and discussed to point out the potential and limitations of the selected porous devices. Practical issues related to material manufacturing and integration into the wind tunnel model are addressed. The noise reduction potential of passive porous trailing-edge devices is found to strongly depend on both these aspects. Issues related to the characterization of the porous materials properties are described. Although porous materials are found to be successful at reducing trailing-edge noise emissions, the results indicate that there is still a need for more generic investigations to further clarify the parametric dependencies between noise reduction and material properties.

scholarly journals Characterization of Overtopping Waves on Sea Dikes with Gentle and Shallow Foreshores

2020 ◽  
Vol 8 (10) ◽  
pp. 752 ◽  
Author(s):  
Tomohiro Suzuki ◽  
Corrado Altomare ◽  
Tomohiro Yasuda ◽  
Toon Verwaest
Keyword(s):  
Climate Change ◽  
Flow Velocity ◽  
Flow Model ◽  
Vertical Wall ◽  
Time Dependent ◽  
Physical Model Test ◽  
Wave Flow ◽  
Flow Depth ◽  
Sea Dikes

Due to ongoing climate change, overtopping risk is increasing. In order to have effective countermeasures, it is useful to understand overtopping processes in details. In this study overtopping flow on a dike with gentle and shallow foreshores are investigated using a non-hydrostatic wave-flow model, SWASH (an acronym of Simulating WAves till SHore). The SWASH model in 2DV (i.e., flume like configuration) is first validated using the data of long crested wave cases with second order wave generation in the physical model test conducted. After that it is used to produce overtopping flow in different wave conditions and bathymetries. The results indicated that the overtopping risk is better characterized by the time dependent h (overtopping flow depth) and u (overtopping flow velocity) instead of hmax (maximum overtopping flow depth) and umax (maximum overtopping flow velocity), which led to overestimation of the risk. The time dependent u and h are strongly influenced by the dike configuration, namely by the promenade width and the existence of a vertical wall on the promenade: the simulation shows that the vertical wall induces seaward velocity on the dike which might be an extra risk during extreme events.

Axisymmetric Stokes Flow Past Cones Including the Case of the Needle

1975 ◽  
Vol 42 (3) ◽  
pp. 569-574
Author(s):  
K. N. Ghia ◽  
A. G. Mikhail
Keyword(s):  
Coordinate System ◽  
Skin Friction ◽  
Stokes Flow ◽  
Small Neighborhood ◽  
Legendre Functions ◽  
Spherical Coordinate ◽  
Associated Legendre Functions ◽  
First Order ◽  
Flow Past ◽  
Limiting Case

The Stokes flow past sharp axisymmetric cones of acute semivertex angle has been studied using an axisymmetric spherical coordinate system. The Stokes solution consists of associated Legendre functions, of the first kind, of the first-order and fractional degree related to the eigenvalues of the problem. These Legendre functions as well as the lowest eigenvalues of the Stokes solution have been accurately evaluated using two different approaches. The present results for the eigenvalues appear to be more accurate than those obtained earlier by Schwiderski, Lugt and Ugincius [3]. An important limiting case with semivertex angle δ → 0, i.e., the needle has been correctly analyzed and the results show that, as δ → 0, the Stokes flow is valid in a vanishingly small neighborhood of the needle with the skin friction being infinite at the “surface” of the needle.

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