Author: Albert H. Jeans
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 176
Book Description
Concave curvature has a relatively large, unpredictable effect on turbulent boundary layers. Some, but not all previous studies suggest that a large-scale, stationary array of counter-rotating vortices exists within the turbulent boundary layer on a concave wall. The objective of the present study was to obtain a qualitative model of the flow field in order to increase our understanding of the underlying physics. A large free-surface water channel was constructed in order to perform a visual study of the flow. Streamwise components of mean velocity and turbulence intensity were measured using a hot film anemometer. The upstream boundary was spanwise uniform with a momentum thickness to radius of curvature of 0.05. Compared to flat wall flow, large-scale, randomly distributed sweeps and ejections were seen in the boundary layer on the concave wall. The sweeps appear to suppress the normal mechanism for turbulence production near the wall by inhibiting the bursting process. The ejections appear to enhance turbulence production in the outer layers as the low speed fluid convected from regions near the wall interacts with the higher speed fluid farther out. The large-scale structures did not occur at fixed spanwise locations, and could not be called roll cells or vortices. (Author).
The Effects of Streamwise Concave Curvature on Turbulent Boundary Layer Structure
Author: Albert H. Jeans
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 176
Book Description
Concave curvature has a relatively large, unpredictable effect on turbulent boundary layers. Some, but not all previous studies suggest that a large-scale, stationary array of counter-rotating vortices exists within the turbulent boundary layer on a concave wall. The objective of the present study was to obtain a qualitative model of the flow field in order to increase our understanding of the underlying physics. A large free-surface water channel was constructed in order to perform a visual study of the flow. Streamwise components of mean velocity and turbulence intensity were measured using a hot film anemometer. The upstream boundary was spanwise uniform with a momentum thickness to radius of curvature of 0.05. Compared to flat wall flow, large-scale, randomly distributed sweeps and ejections were seen in the boundary layer on the concave wall. The sweeps appear to suppress the normal mechanism for turbulence production near the wall by inhibiting the bursting process. The ejections appear to enhance turbulence production in the outer layers as the low speed fluid convected from regions near the wall interacts with the higher speed fluid farther out. The large-scale structures did not occur at fixed spanwise locations, and could not be called roll cells or vortices. (Author).
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 176
Book Description
Concave curvature has a relatively large, unpredictable effect on turbulent boundary layers. Some, but not all previous studies suggest that a large-scale, stationary array of counter-rotating vortices exists within the turbulent boundary layer on a concave wall. The objective of the present study was to obtain a qualitative model of the flow field in order to increase our understanding of the underlying physics. A large free-surface water channel was constructed in order to perform a visual study of the flow. Streamwise components of mean velocity and turbulence intensity were measured using a hot film anemometer. The upstream boundary was spanwise uniform with a momentum thickness to radius of curvature of 0.05. Compared to flat wall flow, large-scale, randomly distributed sweeps and ejections were seen in the boundary layer on the concave wall. The sweeps appear to suppress the normal mechanism for turbulence production near the wall by inhibiting the bursting process. The ejections appear to enhance turbulence production in the outer layers as the low speed fluid convected from regions near the wall interacts with the higher speed fluid farther out. The large-scale structures did not occur at fixed spanwise locations, and could not be called roll cells or vortices. (Author).
The Effects of Streamwise Concave Curvature on Turbalent Boundary Layer Structure
The Effects of Concave Curvature on Turbulent Boundary Layer Structure
Author: Albert Hua Jeans
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 316
Book Description
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 316
Book Description
Structure of Turbulent Boundary Layers on a Concave Surface
Author: Robert S. Barlow
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 276
Book Description
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 276
Book Description
Free-stream Turbulence and Concave Curvature Effects on Heated, Transitional Boundary Layers
The Heat Transfer and Fluid Dynamics of Concave Surface Curvature
Observations of the Effects of High Free-stream Turbulence Levels on the Heat Transfer to a Concavely Curved Turbulent Boundary Layer
Author: Stanford University. Thermosciences Division. Thermosciences Division
Publisher:
ISBN:
Category :
Languages : en
Pages : 62
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 62
Book Description
A DNS Study on the Effects of Streamwise Convex Surface Curvature on Coherent Structures in Turbulent Boundary Layers
Author: Nikunj Harish Dave
Publisher:
ISBN:
Category : Aerospace engineering
Languages : en
Pages : 268
Book Description
Publisher:
ISBN:
Category : Aerospace engineering
Languages : en
Pages : 268
Book Description
Effects of Streamline Curvature on Turbulent Flow
Author: Peter Bradshaw
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 146
Book Description
Streamline curvature in the plane of the mean shear produces large changes in the turbulence structure of shear layers, usually an order of magnitude more important than normal pressure gradients and other terms in the mean-motion equations for curved flows. The effects on momentum and heat transfer in boundary layers are noticeable on typical wing sections and are very important on highly-cambered turbomachine blades: turbulence may be nearly eliminated on highly-convex surfaces, while on highly-concave surfaces momentum transfer by quasi-steady longitudinal vortices dominates the ordinary turbulence processes. The greatly enhanced mixing rates of swirling jets and the characteristic non-turbulent cores of trailing vortices are also consequences of the effects of streamline curvature on the turbulence structure. A progress report, comprises a review of current knowledge, a discussion of methods of predicting curvature effects, and a presentation of principles for the guidance of future workers.
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 146
Book Description
Streamline curvature in the plane of the mean shear produces large changes in the turbulence structure of shear layers, usually an order of magnitude more important than normal pressure gradients and other terms in the mean-motion equations for curved flows. The effects on momentum and heat transfer in boundary layers are noticeable on typical wing sections and are very important on highly-cambered turbomachine blades: turbulence may be nearly eliminated on highly-convex surfaces, while on highly-concave surfaces momentum transfer by quasi-steady longitudinal vortices dominates the ordinary turbulence processes. The greatly enhanced mixing rates of swirling jets and the characteristic non-turbulent cores of trailing vortices are also consequences of the effects of streamline curvature on the turbulence structure. A progress report, comprises a review of current knowledge, a discussion of methods of predicting curvature effects, and a presentation of principles for the guidance of future workers.
Structure of Turbulent Boundary Layers on a Concave Surface
Author: R. S. Barlow (Johnston, J. P.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The effects of strong, concave curvature on the structure of turbulent boundary layers are investigated using flow visualization and two-component laser-doppler anemometry.
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The effects of strong, concave curvature on the structure of turbulent boundary layers are investigated using flow visualization and two-component laser-doppler anemometry.