Modeling Transition in Separated and Attached Boundary Layers

2004 ◽  
Vol 127 (2) ◽  
pp. 402-411 ◽  
Author(s):  
Stephen K. Roberts ◽  
Metin I. Yaras
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Surface Roughness ◽  
Production Rate ◽  
Transition Zone ◽  
Boundary Layers ◽  
Shape Factor ◽  
Separated Flow ◽  
Flow Transition ◽  
Turbulent Spot

This paper presents a mathematical model for predicting the rate of turbulent spot production. In this model, attached- and separated-flow transition are treated in a unified manner, and the boundary layer shape factor is identified as the parameter with which the spot production rate correlates. The model is supplemented by several correlations to allow for its practical use in the prediction of the length of the transition zone. Second, the paper presents a model for the prediction of the location of transition inception in separation bubbles. The model improves on the accuracy of existing alternatives, and is the first to account for the effects of surface roughness.

Modeling of Boundary-Layer Transition

2004 ◽  
Author(s):  
S. K. Roberts ◽  
M. I. Yaras
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Surface Roughness ◽  
Production Rate ◽  
Shape Factor ◽  
Separated Flow ◽  
Boundary Layer Transition ◽  
Flow Transition ◽  
Turbulent Spot ◽  
Layer Transition

This paper presents a mathematical model for predicting the rate of turbulent spot production. In this model, attached- and separated-flow transition are treated in a unified manner, and the boundary layer shape factor is identified as the parameter with which the spot production rate correlates. The model is supplemented by several correlations to allow for its practical use in the prediction of the length of the transition zone. Secondly, the paper presents a model for the prediction of the location of transition inception in separation-bubbles. The model improves on the accuracy of existing alternatives, and is the first to account for the effects of surface roughness.

Evaluation of Turbulent Spot Production Rate in Boundary Layers Under Variable Pressure Gradients for Gas Turbine Applications

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
M. Dellacasagrande ◽  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino
Keyword(s):  
Production Rate ◽  
Boundary Layers ◽  
Turbulence Intensity ◽  
Separated Flow ◽  
Transition Process ◽  
Variable Pressure ◽  
Pressure Gradients ◽  
Turbulent Spot ◽  
Flow Parameters ◽  
Transition Length

Abstract The paper presents several results from an experimental data base on transitional boundary layers developing on a flat plate installed within a variable area opening endwall channel. Measurements have been carried out by means of time-resolved particle image velocimetry (PIV). The overall test matrix spans three Reynolds numbers, four freestream turbulence intensity levels, and four different flow pressure gradients. For each condition, 16,000 instantaneous flow fields have been acquired in order to obtain high statistical accuracy. The flow parameters have been varied in order to provide a gradual shift of the mode of transition from a by-pass process to separated flow transition. In order to quantify the influence of the flow parameter variation on the boundary layer transition process, the transition onset and end positions, and the turbulent spot production rate have been evaluated with a wavelet-based intermittency detection technique for every condition exhibiting a complete transition process. The by-pass transition mode has the longest transition length that decreases with increasing the Reynolds number. The transition length of the separated flow case is smaller than the by-pass one, and the variation of the flow parameters has a similar impact. The variation of the inlet turbulence intensity has a small influence on this parameter except for the condition at the highest turbulence intensity that always shows the lowest turbulent spot production rate because a by-pass type transition occurs. This large amount of data has been used to develop new correlations used to predict the spot production rate and the transition length in attached and separated flows.

Prediction of Turbulent Boundary Layer Development in Conical Diffusers

1966 ◽  
Vol 8 (4) ◽  
pp. 426-436 ◽  
Author(s):  
A. D. Carmichael ◽  
G. N. Pustintsev
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Boundary Layer ◽  
Boundary Layers ◽  
Shape Factor ◽  
Turbulent Boundary Layers ◽  
Energy Deficit ◽  
Momentum Thickness ◽  
Boundary Layer Development ◽  
Layer Development

Methods of predicting the growth of turbulent boundary layers in conical diffusers using the kinetic-energy deficit equation were developed. Three different forms of auxiliary equations were used. Comparison between the measured and predicted results showed that there was fair agreement although there was a tendency to underestimate the predicted momentum thickness and over-estimate the predicted shape factor.

A Method for the Calculation of 3D Boundary Layers on Practical Wing Configurations

1981 ◽  
Vol 103 (1) ◽  
pp. 104-111 ◽  
Author(s):  
J. P. F. Lindhout ◽  
G. Moek ◽  
E. De Boer ◽  
B. Van Den Berg
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Boundary Layer Flow ◽  
Eddy Viscosity ◽  
Separated Flow ◽  
Laminar Boundary Layers ◽  
Eddy Viscosity Model ◽  
Airplane Wing ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow

This paper gives a description of a calculation method for 3D turbulent and laminar boundary layers on nondevelopable surfaces. A simple eddy viscosity model is incorporated in the method. Special attention is given to the organization of the computations to circumvent as much as possible stepsize limitations. The method is also able to proceed the computation around separated flow regions. The method has been applied to the laminar boundary layer flow over a flat plate with attached cylinder, and to a turbulent boundary layer flow over an airplane wing.

An Approach to Three-Dimensional Turbulent Boundary Layers

1966 ◽  
Author(s):  
A. D. Carmichael
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shape Factor ◽  
Basic Assumption ◽  
Three Dimensional ◽  
Cross Flow ◽  
Turbulent Boundary Layers ◽  
Factor H ◽  
Simple Method ◽  
The Cross

A relatively simple method for predicting some of the characteristics of three-dimensional turbulent boundary layers is presented. The basic assumption of the method is that the cross-flow is small. An empirical correlation of a basic shape factor of the cross-flow boundary layer against the streamwise shape factor H is provided. This correlation, together with data for the streamwise boundary layer, is used to predict the cross flow. The solution is very sensitive to the accuracy of the streamwise boundary-layer data which is predicted by conventional two-dimensional methods.

Boundary layer development after a separated region

1998 ◽  
Vol 374 ◽  
pp. 91-116 ◽  
Author(s):  
IAN P. CASTRO ◽  
ELEANORA EPIK
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Free Stream ◽  
Turbulence Models ◽  
Separated Flow ◽  
Leading Edge ◽  
Turbulence Structure ◽  
Outer Flow ◽  
Free Stream Turbulence ◽  
Layer Region

Measurements obtained in boundary layers developing downstream of the highly turbulent, separated flow generated at the leading edge of a blunt flat plate are presented. Two cases are considered: first, when there is only very low (wind tunnel) turbulence present in the free-stream flow and, second, when roughly isotropic, homogeneous turbulence is introduced. With conditions adjusted to ensure that the separated region was of the same length in both cases, the flow around reattachment was significantly different and subsequent differences in the development rate of the two boundary layers are identified. The paper complements, but is much more extensive than, the earlier presentation of some of the basic data (Castro & Epik 1996), confirming not only that the development process is very slow, but also that it is non-monotonic. Turbulence stress levels fall below those typical of zero-pressure-gradient boundary layers and, in many ways, the boundary layer has features similar to those found in standard boundary layers perturbed by free-stream turbulence. It is argued that, at least as far as the turbulence structure is concerned, the inner layer region develops no more quickly than does the outer flow and it is the latter which essentially determines the overall rate of development of the whole flow. Some numerical computations are used to assess the extent to which current turbulence models are adequate for such flows.

scholarly journals On the identification of well-behaved turbulent boundary layers

2017 ◽  
Vol 822 ◽  
pp. 109-138 ◽  
Author(s):  
C. Sanmiguel Vila ◽  
R. Vinuesa ◽  
S. Discetti ◽  
A. Ianiro ◽  
P. Schlatter ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Skin Friction ◽  
Boundary Layers ◽  
Shape Factor ◽  
Outer Region ◽  
The Other ◽  
Diagnostic Plot ◽  
Other Hand

This paper introduces a new method based on the diagnostic plot (Alfredsson et al., Phys. Fluids, vol. 23, 2011, 041702) to assess the convergence towards a well-behaved zero-pressure-gradient (ZPG) turbulent boundary layer (TBL). The most popular and well-understood methods to assess the convergence towards a well-behaved state rely on empirical skin-friction curves (requiring accurate skin-friction measurements), shape-factor curves (requiring full velocity profile measurements with an accurate wall position determination) or wake-parameter curves (requiring both of the previous quantities). On the other hand, the proposed diagnostic-plot method only needs measurements of mean and fluctuating velocities in the outer region of the boundary layer at arbitrary wall-normal positions. To test the method, six tripping configurations, including optimal set-ups as well as both under- and overtripped cases, are used to quantify the convergence of ZPG TBLs towards well-behaved conditions in the Reynolds-number range covered by recent high-fidelity direct numerical simulation data up to a Reynolds number based on the momentum thickness and free-stream velocity $Re_{\unicode[STIX]{x1D703}}$ of approximately 4000 (corresponding to 2.5 m from the leading edge) in a wind-tunnel experiment. Additionally, recent high-Reynolds-number data sets have been employed to validate the method. The results show that weak tripping configurations lead to deviations in the mean flow and the velocity fluctuations within the logarithmic region with respect to optimally tripped boundary layers. On the other hand, a strong trip leads to a more energized outer region, manifested in the emergence of an outer peak in the velocity-fluctuation profile and in a more prominent wake region. While established criteria based on skin-friction and shape-factor correlations yield generally equivalent results with the diagnostic-plot method in terms of convergence towards a well-behaved state, the proposed method has the advantage of being a practical surrogate that is a more efficient tool when designing the set-up for TBL experiments, since it diagnoses the state of the boundary layer without the need to perform extensive velocity profile measurements.

Predicting Transitional Separation Bubbles

2004 ◽  
Vol 127 (3) ◽  
pp. 497-501
Author(s):  
John A. Redford ◽  
Mark W. Johnson
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Transition Process ◽  
Test Cases ◽  
Transition Model ◽  
Flow Transition ◽  
Free Stream Turbulence ◽  
Attached Flow

This paper describes the modifications made to a successful attached flow transition model to produce a model capable of predicting both attached and separated flow transition. This transition model is used in combination with the Fluent CFD software, which is used to compute the flow around the blade assuming that it remains entirely laminar. The transition model then determines the start of transition location and the development of the intermittency. These intermittency values weight the laminar and turbulent boundary layer profiles to obtain the resulting transitional boundary layer parameters. The ERCOFTAC T3L test cases are used to validate the predictions. The T3L blade is a flat plate with a semi-circular leading edge, which results in the formation of a separation bubble the length of which is strongly dependent on the transition process. Predictions were performed for five T3L test cases for differing free-stream turbulence levels and Reynolds numbers. For the majority of these test cases the measurements were accurately predicted.

The Shape-Factor Relationship for Turbulent Boundary Layers

1983 ◽  
Vol 34 (2) ◽  
pp. 147-161 ◽  
Author(s):  
M.M.M. El Telbany ◽  
J. Niknejad ◽  
A.J. Reynolds
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shape Factor ◽  
Factor H ◽  
Boundary Layer Development ◽  
The Common ◽  
Modified Formula ◽  
The Relationship ◽  
Layer Development ◽  
Common Shape

SummaryConsideration is given to the relationship H1 = f(H) linking the common shape factor H and the mass-flow shape parameter H1 which is used in entrainment models of boundary-layer development. A formula suggested by Green et al is found to be most nearly consistent with the measurements presented. However, a more exact prediction of H1 is obtained by introducing a factor involving the Reynolds number based on the local momentum thickness θ; thus H1 = f(H, Reθ). Predictions obtained by incorporating the appropriately modified entrainment equation into the well-known method of Green et al prove not to give an improved representation of the development of boundary layers studied experimentally by the authors and others. It is concluded that the modified formula for H1 is primarily useful in giving an improved specification of the overall boundary layer thickness δ = θ(H1 + H), and hence of other features of the developing profile.

scholarly journals A Theory for Predicting the Turbulent-Spot Production Rate

1998 ◽  
Author(s):  
R. E. Mayle
Keyword(s):  
Boundary Layer ◽  
Production Rate ◽  
Free Stream ◽  
Length Scale ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Turbulent Spot ◽  
Boundary Layer Flows ◽  
Free Stream Turbulence ◽  
New Correlation

A theory is presented for predicting the production rate of turbulent spots. The theory, based on that by Mayle-Schulz for bypass transition, leads to a new correlation for the spot production rate in boundary layer flows with a zero pressure gradient. The correlation, which agrees reasonably well with data, clearly shows the effects of both free-stream turbulence level and length scale. In addition, the theory provides an estimate for the lowest level of free-stream turbulence causing bypass transition.

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