Turbulence Dynamics in the Merging Process of Supersonic Streamwise Vortices

2018 ◽  
Author(s):  
Fabrizio Vergine ◽  
Davide Vigano ◽  
Luca Maddalena
Keyword(s):  
Streamwise Vortices ◽  
Merging Process

Interaction of large three-dimensional eddies and small streamwise vortices

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1330-1332
Author(s):  
Roy Y. Myose ◽  
Ron F. Blackwelder
Keyword(s):  
Three Dimensional ◽  
Streamwise Vortices

Visualization of Counter-rotating Streamwise Vortices in a Rectangular Channel with One-sided Wavy Surface

2013 ◽  
Author(s):  
Alexander C. Budiman ◽  
Hatsari Mitsudharmadi ◽  
Hong Tong Low ◽  
S. Winoto
Keyword(s):  
Rectangular Channel ◽  
Wavy Surface ◽  
Streamwise Vortices

Numerical Investigation of Passive Flow Control Using Wavy Blades in a Highly-Loaded Compressor Cascade

2018 ◽  
Author(s):  
Bo Wang ◽  
Yanhui Wu ◽  
Kai Liu
Keyword(s):  
Numerical Investigation ◽  
Flow Structure ◽  
Cross Flow ◽  
Leading Edge ◽  
Control Flow ◽  
Streamwise Vortices ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Highly Loaded

Driven by the need to control flow separations in highly loaded compressors, a numerical investigation is carried out to study the control effect of wavy blades in a linear compressor cascade. Two types of wavy blades are studied with wavy blade-A having a sinusoidal leading edge, while wavy blade-B having pitchwise sinusoidal variation in the stacking line. The influence of wavy blades on the cascade performance is evaluated at incidences from −1° to +9°. For the wavy blade-A with suitable waviness parameters, the cascade diffusion capacity is enhanced accompanied by the loss reduction under high incidence conditions where 2D separation is the dominant flow structure on the suction surface of the unmodified blade. For well-designed wavy blade-B, the improvement of cascade performance is achieved under low incidence conditions where 3D corner separation is the dominant flow structure on the suction surface of the baseline blade. The influence of waviness parameters on the control effect is also discussed by comparing the performance of cascades with different wavy blade configurations. Detailed analysis of the predicted flow field shows that both the wavy blade-A and wavy blade-B have capacity to control flow separation in the cascade but their control mechanism are different. For wavy blade-A, the wavy leading edge results in the formation of counter-rotating streamwise vortices downstream of trough. These streamwise vortices can not only enhance momentum exchange between the outer flow and blade boundary layer, but also act as the suction surface fence to hamper the upwash of low momentum fluid driven by cross flow. For wavy blade-B, the wavy surface on the blade leads to a reduction of the cross flow upwash by influencing the spanwise distribution of the suction surface static pressure and guiding the upwash flow.

Experiments on streamwise vortices in curved wall jet flow

1995 ◽  
Vol 7 (12) ◽  
pp. 2978-2988 ◽  
Author(s):  
O. John E. Matsson
Keyword(s):  
Jet Flow ◽  
Wall Jet ◽  
Streamwise Vortices ◽  
Wall Jet Flow

Flat plate drag reduction using plasma-generated streamwise vortices

2021 ◽  
Vol 918 ◽  
Author(s):  
X.Q. Cheng ◽  
C.W. Wong ◽  
F. Hussain ◽  
W. Schröder ◽  
Y. Zhou
Keyword(s):  
Drag Reduction ◽  
Flat Plate ◽  
Streamwise Vortices

Abstract

The flow over a backward-facing step under controlled perturbation: laminar separation

1992 ◽  
Vol 238 ◽  
pp. 73-96 ◽  
Author(s):  
M. A. Z. Hasan
Keyword(s):  
Shear Layer ◽  
Low Frequency ◽  
Layer Growth ◽  
Stream Velocity ◽  
Backward Facing Step ◽  
Laminar Separation ◽  
Vortex Merging ◽  
Layer Growth Rate ◽  
Merging Process ◽  
Layer Flow

The flow over a backward-facing step with laminar separation was investigated experimentally under controlled perturbation for a Reynolds number of 11000, based on a step height h and a free-stream velocity UO. The reattaching shear layer was found to have two distinct modes of instability: the ‘shear layer mode’ of instability at Stθ ≈ 0.012 (Stθ ≡ fθ/UO, θ being the momentum thickness at separation and f the natural roll-up frequency of the shear layer); and the ‘step mode’ of instability at Sth ≈ 0.185 (Sth ≡ fh/U0). The shear layer instability frequency reduced to the step mode one via one or more stages of a vortex merging process. The perturbation increased the shear layer growth rate and the turbulence intensity and decreased the reattachment length compared to the unperturbed flow. Cross-stream measurements of the amplitudes of the perturbed frequency and its harmonics suggested the splitting of the shear layer. Flow visualization confirmed the shear layer splitting and showed the existence of a low-frequency flapping of the shear layer.

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