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Spanwise bifurcation in plane-symmetric sudden-expansion flows
T P Chiang1, Tony W H Sheu, Robert R Hwang
1Department of Naval Architecture and Ocean Engineering, National Taiwan University, Taipei, Taiwan, Republic of China.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|January 22, 2002
Summary
This study reveals how 3D fluid flow in a sudden expansion channel exhibits complex bifurcation behaviors. Spanwise bifurcation is challenging to achieve, unlike step height bifurcation, due to flow instabilities.
Area of Science:
- Fluid dynamics
- Computational fluid dynamics (CFD)
- Nonlinear dynamics
Background:
- Sudden expansion flows are fundamental in fluid mechanics.
- Bifurcation phenomena indicate transitions to complex flow patterns.
- Understanding these transitions is crucial for engineering applications.
Purpose of the Study:
- To computationally investigate steady bifurcation phenomena in 3D plane-symmetric sudden expansion flows.
- To analyze the conditions leading to spanwise and step height bifurcations.
- To explore the stability and characteristics of different bifurcation types.
Main Methods:
- Numerical simulation of three-dimensional, plane-symmetric sudden expansion flows.
- Analysis of flow behavior across varying channel aspect ratios and Reynolds numbers.
- Identification and characterization of steady bifurcation points.
Main Results:
- A critical channel aspect ratio determines the type of bifurcation observed.
- Above the critical ratio, step height bifurcation exhibits asymmetric behavior and spanwise divergence.
- Below the critical ratio, spanwise bifurcation is unstable and transitions to step height bifurcation.
- Spanwise bifurcation is more difficult to attain due to 2D instability on the symmetry plane.
Conclusions:
- The study elucidates the complex interplay between channel geometry and flow stability in sudden expansions.
- Spanwise bifurcation presents a distinct and less stable flow regime compared to step height bifurcation.
- Findings provide insights into predicting and controlling flow behavior in such systems.