Some observations of the transition process on the windward face of a long yawed cylinder

1985 ◽  
Vol 150 ◽  
pp. 329-356 ◽  
Author(s):  
D. I. A. Poll
Keyword(s):  
Boundary Layer ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Transition Process ◽  
Theoretical Models ◽  
Boundary Layer Flows ◽  
Sufficient Detail ◽  
Oil Flow ◽  
Dimensional Boundary

An experiment has been performed to determine the effect of yaw upon transition in the boundary layer formed on the windward face of a long cylinder. The china-clay-evaporation and surface-oil-flow techniques have been used to study the development of the fixed-wavelength stationary disturbances which are characteristic of cross-flow instability. It has been found that the boundary layer is also susceptible to time-dependent disturbances which grow to very large amplitudes prior to the onset of transition. These disturbances have been studied with a hot-wire anemometer. The conditions necessary for the onset and completion of transition have been determined by the use of surface Pitot tubes. Data from the experiment have been compared with the simple criteria for instability and transition which were proposed by Owen & Randall over thirty years ago. In general it has been found that these criteria are inadequate, and, where possible, improvements have been proposed. The raw data are presented in sufficient detail for them to be used to test, or calibrate, future theoretical models of the transition process in three-dimensional boundary-layer flows.

scholarly journals Transition control in a three-dimensional boundary layer at elevated free stream turbulence using dielectric barrier discharge

2019 ◽  
Vol 486 (6) ◽  
pp. 668-672
Author(s):  
S. A. Baranov ◽  
A. Ph. Kiselev ◽  
I. A. Moralev ◽  
D. S. Sboev ◽  
S. N. Tolkachev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Dielectric Barrier Discharge ◽  
Free Stream ◽  
Barrier Discharge ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Dielectric Barrier ◽  
Free Stream Turbulence ◽  
Dimensional Boundary

The results of an experimental study of the effect of dielectric barrier discharge (DBR) actuator on laminar-turbulent transition in a three-dimensional boundary layer under influence of elevated free-stream turbulence are presented. The travelling cross-flow instability modes are dominated in transition in a base configuration. Their characteristics do not depend on a spanwise position. The DBD-actuator that generated stationary cross-flow vortices with the predefined spanwise wavelength when turned on was capable to reduce a turbulent spots production rate in comparison to the base regime.

Attenuation of Cross-Flow Instability in a Three-Dimensional Boundary Layer by Means of a Multidischarge Actuator System

2019 ◽  
Vol 64 (9) ◽  
pp. 365-369
Author(s):  
S. A. Baranov ◽  
M. D. Gamirullin ◽  
A. Ph. Kiselev ◽  
A. P. Kuryachii ◽  
D. S. Sboev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Dimensional Boundary ◽  
Actuator System

scholarly journals Attenuation of cross-flow instability in three-dimensional boundary layer by means of multi-discharge actuator system

2019 ◽  
Vol 488 (2) ◽  
pp. 147-152
Author(s):  
S. A. Baranov ◽  
M. D. Gamirullin ◽  
A. Ph. Kiselev ◽  
A. P. Kuryachii ◽  
D. S. Sboev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Body Force ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
The Body ◽  
Subsonic Wind Tunnel ◽  
Significant Area ◽  
Dimensional Boundary ◽  
Force Impact

Results of experiments in low-turbulence subsonic wind tunnel sustaining the possibility of significant attenuation of the cross-flow velocity and the intensity of stationary instability vortices due to the body force impact on three-dimensional boundary layer are presented. The unidirectional body force over a significant area of the streamlined surface has been created with the help of dielectric barrier discharge actuator.

Non-stationary cross-flow vortices in three-dimensional boundary-layer flows

1988 ◽  
Vol 417 (1852) ◽  
pp. 179-212 ◽  
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Cross Flow ◽  
Neutral Stability ◽  
Two Dimensional ◽  
Boundary Layer Flows ◽  
Rotating Disc ◽  
Dimensional Boundary ◽  
Flow Vortex ◽  
The Waves

The upper-branch neutral stability of three-dimensional disturbances imposed on a three-dimensional boundary-layer profile is considered and in particular we investigate non-stationary cross-flow vortices. The wave speed is taken to be small initially and with a disturbance structure analogous to that occurring in two-dimensional boundary-layer stability the linear and nonlinear eigenrelations are derived for profiles with more than one critical layer. For the flow due to a rotating disc we show that linear viscous neutral modes exist for all wave angles between 10.6° and 39.6°. As the extremes of this range are approached the flow structure evolves to another, either the viscous mode of Hall ( Proc. R. Soc. Lond . A 406, 93(1986)) or the non-stationary inviscid modes considered by Stuart in Gregory et al . ( Phil. Trans. R. Soc. Lond . A 248, 155 (1955)). In the former case, corresponding to wave angles of 39.6°, the waves become almost stationary and in the latter case, with wave angles of 10.6° the waves are travelling much faster with a disturbance structure based on the Rayleigh scalings. The analysis is extended to include O (1) wavespeeds and we show that as the wavespeed of the cross-flow vortex approaches the tree-stream value, the corresponding disturbance amplitude increases, the growth here being slower than that for two-dimensional boundary layers.

scholarly journals Continua of states in boundary-layer flows

2002 ◽  
Vol 468 ◽  
pp. 121-152 ◽  
Author(s):  
R. E. HEWITT ◽  
P. W. DUCK ◽  
S. R. STOW
Keyword(s):  
Boundary Layer ◽  
Velocity Component ◽  
Three Dimensional ◽  
Cross Flow ◽  
Critical Value ◽  
Far Field ◽  
Boundary Layer Flows ◽  
Dimensional Boundary ◽  
Cross Flow Velocity ◽  
The Continuum

We consider a class of three-dimensional boundary-layer flows, which may be viewed as an extension of the Falkner–Skan similarity form, to include a cross-flow velocity component, about a plane of symmetry. In general, this provides a range of three- dimensional boundary-layer solutions, parameterized by a Falkner–Skan similarity parameter, n, together with a further parameter, Ψ∞, which is associated with a cross-flow velocity component in the external flow. In this work two particular cases are of special interest: for n = 0 the similarity equations possess a family of solutions related to the Blasius boundary layer; for n = 1 the similarity solution provides an exact reduction of the Navier–Stokes equations corresponding to the flow near a saddle point of attachment. It is known from the work of Davey (1961) that in this latter class of flow, a continuum of solutions can be found. The continuum arises (in general) because it is possible to find states with an algebraic, rather than exponential, behaviour in the far field. In this work we provide a detailed overview of the continuum states, and show that a discrete infinity of ‘exponential modes’ are smoothly embedded within the ‘algebraic modes’ of the continuum. At a critical value of the cross-flow, these exponential modes appear as a cascade of eigensolutions to the far-field equations, which arise in a manner analogous to the energy eigenstates found in quantum mechanical problems described by the Schrödinger equation.The presence of a discrete infinity of exponential modes is shown to be a generic property of the similarity equations derived for a general n. Furthermore, we show that there may also exist non-uniqueness of the continuum; that is, more than one continuum of states can exist, that are isolated for fixed n and Ψ∞, but which are connected through an unfolded transcritical bifurcation at a critical value of the cross-flow parameter, Ψ∞.The multiplicity of states raises the question of solution selection, which is addressed using two stability analyses that assume the same basic symmetry properties as the base flow. In one case we consider a steady, algebraic form in the ‘streamwise’ direction, whilst in the other a temporal form is assumed. In both cases it is possible to extend the analysis to consider a continuous spectrum of disturbances that decay algebraically in the wall-normal direction. We note some obvious parallels that exist between such stability analyses and the approach to the continua of states described earlier in the paper.We also discuss the appearance of analogous non-unique states to the Falkner–Skan equation in the presence of an adverse pressure gradient (i.e. n < 0) in an appendix.

An Assessment of Three-Dimensional Turbulent Boundary Layer Prediction Methods

1973 ◽  
Vol 95 (3) ◽  
pp. 415-421 ◽  
Author(s):  
A. J. Wheeler ◽  
J. P. Johnston
Keyword(s):  
Boundary Layer ◽  
Eddy Viscosity ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Boundary Layer Flows ◽  
Mean Velocity ◽  
Eddy Viscosity Model ◽  
Separating Flow ◽  
Dimensional Boundary ◽  
Stress Models

Predictions have been made for a variety of experimental three-dimensional boundary layer flows with a single finite difference method which was used with three different turbulent stress models: (i) an eddy viscosity model, (ii) the “Nash” model, and (iii) the “Bradshaw” model. For many purposes, even the simplest stress model (eddy viscosity) was adequate to predict the mean velocity field. On the other hand, the profile of shear stress direction was not correctly predicted in one case by any model tested. The high sensitivity of the predicted results to free stream pressure gradient in separating flow cases is demonstrated.

Boundary layer at a swept stagnation line of semi-infinite extent

1970 ◽  
Vol 41 (4) ◽  
pp. 737-750 ◽  
Author(s):  
Paul A. Libby ◽  
Karl K. Chen
Keyword(s):  
Boundary Layer ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Cross Flow ◽  
Differential Analysis ◽  
Eigenvalues And Eigenfunctions ◽  
Stagnation Line ◽  
Infinite Extent ◽  
Dimensional Boundary ◽  
Upstream Flow

A three-dimensional boundary layer developing along a semi-infinite swept stagnation line from a starting edge and evolving into that associated with such a line of infinite extent is calculated. A series solution useful for assessing the counteracting effects of cross-flow and mass transfer near the starting edge and for providing initial data for a subsequent streamwise, numerical solution is developed. The asymptotic behaviour far from the starting edge is examined and shown to involve only eigenfunction contributions associated with the far upstream flow. However, it is not presently possible to determine the relevant eigenvalues and eigenfunctions. Numerical solutions based on a difference-differential analysis yield the entire development of the boundary layer and indicate the streamwise length required for the case of the boundary layer at an infinite stagnation line to be obtained.

Three-Dimensional Calculation of Wall Boundary Layer Flows in Turbomachines

1987 ◽  
Author(s):  
W. L. Lindsay ◽  
H. B. Carrick ◽  
J. H. Horlock
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Cross Flow ◽  
Flow Profile ◽  
Boundary Layer Flows ◽  
Wall Boundary Layer ◽  
Boundary Layer Development ◽  
Flow Through ◽  
The Cross

An integral method of calculating the three-dimensional turbulent boundary layer development through the blade rows of turbomachines is described. It is based on the solution of simultaneous equations for (i) & (ii) the growth of streamwise and cross-flow momentum thicknesses; (iii) entrainment; (iv) the wall shear stress; (v) the position of maximum cross-flow. The velocity profile of the streamwise boundary layer is assumed to be that described by Coles. The cross-flow profile is assumed to be the simple form suggested by Johnston, but modified by the effect of bounding blade surfaces, which restrict the cross-flow. The momentum equations include expressions for “force-defect” terms which are also based on secondary flow analysis. Calculations of the flow through a set of guide vanes of low deflection show good agreement with experimental results; however, attempts to calculate flows of higher deflection are found to be less successful.

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