Flow visualization of Dean vortices in a curved channel with 40 to 1 aspect ratio

1988 ◽  
Vol 31 (12) ◽  
pp. 3605 ◽  
Author(s):  
P. M. Ligrani ◽  
R. D. Niver
Keyword(s):  
Aspect Ratio ◽  
Flow Visualization ◽  
Curved Channel ◽  
Dean Vortices

Dean vortices in finite-aspect-ratio ducts

2013 ◽  
Vol 716 ◽  
Author(s):  
Philip E. Haines ◽  
James P. Denier ◽  
Andrew P. Bassom
Keyword(s):  
Aspect Ratio ◽  
Stokes Equations ◽  
Finite Amplitude ◽  
Navier Stokes ◽  
Curved Channel ◽  
Dean Number ◽  
Element Analysis ◽  
Navier Stokes Equations ◽  
New Class ◽  
Dean Vortices

AbstractWe consider the development of Dean vortices in a curved channel of finite aspect ratio. Solutions to the axisymmetric Navier–Stokes equations are obtained through a finite-element analysis, allowing us to explore the complex and rich bifurcation pattern of the flow as the aspect ratio and Dean number vary. We demonstrate a new class of finite-amplitude vortices and discuss their relationship to similar structures seen in finite-length Taylor–Couette flow.

On longitudinal vortices in curved channel flow

1993 ◽  
Vol 251 ◽  
pp. 627-660 ◽  
Author(s):  
Alessandro Bottaro
Keyword(s):  
High Speed ◽  
Curved Channel ◽  
Longitudinal Vortices ◽  
Dean Vortices ◽  
Vortex Pairs ◽  
Spatial Approach ◽  
Temporal Model ◽  
Inlet Conditions ◽  
Curved Channel Flow ◽  
Good Agreement

The laminar flow in a curved channel is studied numerically to analyse the initial formation, development and interaction phenomena of an array of centrifugally induced longitudinal vortices arranged across the span of the channel. Simulations employing streamwise periodic boundary conditions (temporal model) as well as inlet-outlet conditions (spatial model) are carried out. In the temporal approach the interactions (pairing of vortices and growth of new vortex pairs) of fully developed vortex pairs are time-dependent, whereas in the spatial approach these events are inherently steady and concern vortices not in their fully developed state. The initial spatial development of the vortices is in excellent agreement with results of a linear stability analysis up to fairly large disturbance amplitudes. In the nonlinear regime a good agreement with experimental results has also been found. The receptivity of the flow is very important in a convectively unstable situation such as the present one and different behaviour is found at fixed Reynolds number (equal to 2.43 times the critical value for the onset of Dean vortices): the flow can be either steady or undergo a continuous sequence of merging and splitting events, depending on the inlet conditions. In the latter situation decorrelated patterns of low- and high-speed streaks are produced in streamwise-spanwise planes and they bear several similarities to near-wall coherent structures of turbulent boundary layers.

Curvature- and rotation-induced instabilities in channel flow

1990 ◽  
Vol 210 ◽  
pp. 537-563 ◽  
Author(s):  
O. John E. Matsson ◽  
P. Henrik Alfredsson
Keyword(s):  
Reynolds Number ◽  
Linear Stability ◽  
Channel Flow ◽  
Stability Theory ◽  
Critical Reynolds Number ◽  
Secondary Instability ◽  
Linear Stability Theory ◽  
Curved Channel ◽  
Dean Vortices ◽  
Coriolis Effects

In a curved channel streamwise vortices, often called Dean vortices, may develop above a critical Reynolds number owing to centrifugal effects. Similar vortices can occur in a rotating plane channel due to Coriolis effects if the axis of rotation is normal to the mean flow velocity and parallel to the walls. In this paper the flow in a curved rotating channel is considered. It is shown from linear stability theory that there is a region for which centrifugal effects and Coriolis effects almost cancel each other, which increases the critical Reynolds number substantially. The flow visualization experiments carried out show that a complete cancellation of Dean vortices can be obtained for low Reynolds number. The rotation rate for which this occurs is in close agreement with predictions from linear stability theory. For curved channel flow a secondary instability of travelling wave type is found at a Reynolds number about three times higher than the critical one for the primary instability. It is shown that rotation can completely cancel the secondary instability.

scholarly journals The flow visualization on the rotary wing with low aspect ratio.

1987 ◽  
Vol 35 (402) ◽  
pp. 346-352
Author(s):  
Tadaharu WATANUKI ◽  
Masayoshi MATSUZAKA ◽  
Hirotoshi KUBOTA ◽  
Kojiro SUZUKI ◽  
Kouichi SAGAWA ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Flow Visualization ◽  
Low Aspect Ratio ◽  
Rotary Wing

Experimental Investigation of a Free Round Jet with Dean Vortices

2014 ◽  
Vol 9 (2) ◽  
pp. 128-135
Author(s):  
Maria Litvinenko ◽  
Yuriy Litvinenko ◽  
Grigory Kozlov ◽  
Valentin Vikhorev
Keyword(s):  
Experimental Investigation ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Acoustic Excitation ◽  
Hot Wire ◽  
Curved Channel ◽  
Mean Velocity ◽  
Round Jet ◽  
Smoke Visualization ◽  
Dean Vortices

Results of the experimental investigations of free round jet with Dean vortices formed in curved channel are presented. Hot-wire anemometry measurements of three-dimensional mean velocity profile were performed, smoke visualization pictures cross and longitudinal sections at nozzle exit and downstream were obtained. The features of jet development at acoustic excitation of 40 Hz are shown

Mixing Enhancement in Spiral Microchannels

2016 ◽  
Author(s):  
Lakshmi Balasubramaniam ◽  
Rerngchai Arayanarakool ◽  
Samuel D. Marshall ◽  
Bing Li ◽  
Poh Seng Lee ◽  
...  
Keyword(s):  
Industrial Applications ◽  
Secondary Flows ◽  
Experimental Investigations ◽  
Mixing Enhancement ◽  
Curved Channel ◽  
Cross Sectional ◽  
Mixing Performance ◽  
Dean Vortices ◽  
Potential Applications ◽  
Sectional Shape

Advancements in the field of microfluidics has led to an increasing interest to study laminar flow in microchannel and its potential applications. Understanding mixing at a microscale can be useful in various biological, heating and industrial applications due to the space and time reduction that micro mixing permits. This work aims to study mixing enhancement due to curved microchannel and the influence of varying microchannel cross sectional shape through numerical and experimental investigations. Unlike prior studies which use channel dimensions in the lower microscale range, this work has been conducted on channels with dimensions in the higher end of micrometer range. Using a cross sectional hydraulic diameter of 600 μm enables introduction of flow into the curved channel at a Reynolds Number ranging from 0.15 to 75, the findings of which show considerable improvement in the mixing performance as compared to that of equivalent straight channels, due to the development of secondary flows known as Dean Vortices.

Experimental Investigation of a Scaled-Up Passive Curved Channel Micromixer With Slanted Grooves

2011 ◽  
Author(s):  
Kristina J. Cook ◽  
Ibrahim G. Hassan
Keyword(s):  
Secondary Flow ◽  
Concentration Distribution ◽  
Rotational Flow ◽  
Curved Channel ◽  
Dean Vortices ◽  
Alternating Direction ◽  
Increased Strength ◽  
Pattern Information ◽  
Top View ◽  
Curved Interface

The flow patterns and concentration distribution in a passive scaled-up micromixer is investigated experimentally over 5 ≤ Re ≤ 100. Four meandering elements serve to enlarge species interface area through the formation of Dean vortices, while 36 slanted grooved structures enhance secondary flow by promoting helical flow. The alternating direction of the curved channel segments and slanted grooves alternated the direction of secondary flow, increasing mixing. Flow visualization provides flow pattern information as seen from the top view, while induced fluorescence provides concentration distribution information at the outlet along the center plane. At low Re (Re = 5), species appear nearly horizontally stacked at the outlet, with a curved interface. As the Reynolds number increases, the angle the species interface makes with the horizontal direction increases due to the increased strength in rotational flow. At higher Re, the formation of Dean vortices is apparent.

scholarly journals PIV-Measurements of Centrifugal Instabilities in a Rectangular Curved Duct with a Small Aspect Ratio

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 184
Author(s):  
Afshin Goharzadeh ◽  
Peter Rodgers
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Velocity Distribution ◽  
Channel Wall ◽  
Secondary Flows ◽  
Working Fluid ◽  
Measured Velocity ◽  
Outer Channel ◽  
Dean Vortices ◽  
Curved Duct

In this study, experimental measurements were undertaken using non-intrusive particle image velocimetry (PIV) to investigate fluid flow within a 180° rectangular, curved duct geometry of a height-to-width aspect ratio of 0.167 and a curvature of 0.54. The duct was constructed from Plexiglas to permit optical access to flow pattern observations and flow velocity field measurements. Silicone oil was used as working fluid because it has a similar refractive index to Plexiglas. The measured velocity fields within the Reynolds number ranged from 116 to 203 and were presented at the curved channel section inlet and outlet, as well as at the mid-channel height over the complete duct length. It was observed from spanwise measurements that the transition to unsteady secondary flows generated the creation of wavy structures linked with the formation of Dean vortices close to the outer channel wall. This flow structure became unsteady with increasing Reynolds number. Simultaneously, the presence of Dean vortices in the spanwise direction influenced the velocity distribution in the streamwise direction. Two distinct regions defined by a higher velocity distribution were observed. Fluid particles were accelerated near the inner wall of the channel bend and subsequently downstream near the outer channel wall.

Dean vortices with wall flux in a curved channel membrane system

1993 ◽  
Vol 81 (1-2) ◽  
pp. 127-137 ◽  
Author(s):  
Mary E. Brewster ◽  
Kun-Yong Chung ◽  
Georges Belfort
Keyword(s):  
Membrane System ◽  
Curved Channel ◽  
Dean Vortices
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