Boundary Layers and Skin Friction in High-Speed Flow

1951 ◽  
Vol 55 (485) ◽  
pp. 285-302 ◽  
Author(s):  
A. D. Young
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
High Speed ◽  
Scale Effects ◽  
Practical Interest ◽  
High Speed Flow ◽  
High Speeds ◽  
Speed Flow ◽  
The Subject ◽  
Small Disturbances

SummaryIn this paper an attempt is made to review present knowledge of the subject of boundary layers at high speeds, without delving too deeply into the theory, and to draw attention to the results of practical interest. The introductory remarks describe broadly the special features of boundary layers in compressible flow, namely the existence of both thermal and velocity layers and their interdependence, the sensitivity of the external flow to the layers, and their inter-action with shock waves. The results of importance arising from the theory of the laminar boundary layer and of its stability to small disturbances are then discussed, followed by a summary of the present inadequate state of knowledge of turbulent boundary layer characteristics. It is noted that progress in the latter must await the production of more experimental data. The paper concludes with a discussion of scale effects and the allied problem of boundary layer—shock wave inter-action.

scholarly journals Counter-hairpin vortices in the turbulent wake of a sharp trailing edge

2011 ◽  
Vol 689 ◽  
pp. 317-356 ◽  
Author(s):  
Sina Ghaemi ◽  
Fulvio Scarano
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Coherent Structures ◽  
High Speed ◽  
High Speed Flow ◽  
Trailing Edge ◽  
Hairpin Vortices ◽  
Low Speed ◽  
Speed Flow ◽  
Low Speed Streaks

AbstractThe unsteady organization and evolution of coherent structures within the turbulent boundary layer and subsequent wake of the sharp symmetric trailing edge of a NACA0012 aerofoil are investigated. The experiments are conducted in an open test-section wind tunnel at ${\mathit{Re}}_{c} = \text{386\hspace{0.167em}000} $ based on the aerofoil chord and ${\mathit{Re}}_{\theta } = 1300$ based on the boundary layer momentum thickness. An initial characterization of the flow field using two-component particle image velocimetry (PIV) is followed by the investigation of the unsteady organization and evolution of coherent structures by time-resolved three-dimensional PIV based on a tomographic approach (Tomo-PIV). The inspection of the turbulent boundary layer prior to the trailing edge in the region between 0.15 and $0. 8\hspace{0.167em} {\delta }_{99} $ demonstrated streaks of low- and high-speed flow, while the low-speed streaks are observed to be more coherent along with strong interaction with hairpin-type vortical structures similar to a turbulent boundary layer at zero pressure gradient. The wake region demonstrated gradual deterioration of both the low- and the high-speed streaks with downstream progress. However, the low-speed streaks are observed to lose their coherence at a faster rate relative to the high-speed streaks as the turbulent flow develops towards the far wake. The weakening of the low-speed streaks is due to the disappearance of the viscous sublayer after the trailing edge and gradual mixing through the transport of the remaining low-speed flow towards the free stream. This transport of low-speed flow is performed by the ejection events induced by the hairpin vortices as they also persist into the developing wake. The higher persistence of the high-speed streaks is associated with counter-hairpin vortical activities as they oppose the deterioration of the high-speed streaks by frequently sweeping the high-speed flow towards the wake centreline. These vortical structures are regarded as counter-hairpin vortices as they exhibit opposite characteristics relative to the hairpin vortices of a turbulent boundary layer. They are topologically similar to the hairpins as they appear to be U-shaped but with inverted orientation, as the spanwise portion is in the vicinity of the wake centreline and the legs are inclined at an approximately $6{0}^{\ensuremath{\circ} } $ to the wake axis in the downstream direction demonstrating a strain-dominated topology. The counter-hairpin vortices are partially wrapped around the high-speed streaks and contribute to the wake development by transporting high-speed flow towards the wake centreline. Similar to the hairpin vortices of a turbulent boundary layer, the occurrence of a complete counter-hairpin vortex is occasional while its derivatives (portions of spanwise or quasi-streamwise vortices) are more frequently observed. Therefore, a pattern recognition algorithm is applied to establish characterization based on an ensemble-averaged counter-hairpin vortex. The formation of the counter-hairpin vortices is due to an additional degree of interaction between the low- and high-speed streaks after the trailing edge across the wake centreline. The shear layer produced along the wake centreline by neighbouring low- and high-speed streaks promotes the formation of spanwise vortices that form the counter-hairpin vortices by connection to quasi-streamwise vortices. Finally, a conceptual model is proposed to depict the three-dimensional unsteady organization and evolution of coherent structures in the wake region based on the hairpin and counter-hairpin vortex signatures.

scholarly journals Features of high-speed aircraft numerical simulation

2020 ◽  
Author(s):  
M.M. Alekseeva ◽  
N.A. Brykov ◽  
I.A. Vikhrova
Keyword(s):  
Numerical Simulation ◽  
Gas Dynamics ◽  
High Speed ◽  
Simulation Method ◽  
High Speed Flow ◽  
Flight Tests ◽  
High Speeds ◽  
Physical Experiments ◽  
Speed Flow ◽  
Flow Around A Body

Currently, the creation of new high-speed aircraft is of great interest. The development of such aircraft is associated with the need for experiments and flight tests. The organization of real physical experiments in the field of high speeds is fraught with significant difficulties that can be solved using the numerical simulation method, which makes it possible to significantly simplify the process of creating new products. When developing a high-speed aircraft, it is necessary to take into account the specific aerodynamic and thermophysical features of the processes occurring on the surface of the aircraft and in the shock layer. In this paper, the features of the processes at high speeds are considered on the example of solving the external and internal problems of the gas dynamics of an aircraft. Based on the specifics of these processes, we built a mathematical model that allows us to study the aerodynamics of a high-speed flow around a body in dense layers of the atmosphere and the processes that occur in the combustion chamber.

Critical mach numbers for swept-back wings

1950 ◽  
Vol 2 (2) ◽  
pp. 85-110 ◽  
Author(s):  
S. Neumark
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Fundamental Problem ◽  
Theoretical Work ◽  
High Speed Flow ◽  
High Speeds ◽  
Speed Flow ◽  
Low Incidence ◽  
The Many ◽  
Work Done

SummaryThe effect of yawing a wing in high-speed flow is to delay the onset of shock waves and to increase the critical Mach number. This is because shock waves can only develop along the isobars (running parallel to the edges of the wing, which is assumed untapered and infinitely long), and therefore only the velocity component normal to the edges is significant. To some extent the same is true for a finite sheared or swept-back wing, though the problem is made more complicated by the various additional factors, such as finite aspect ratio (tip effect), plan form (e.g. taper effect) and, what is perhaps the most important, the central kink effect. The experimental technique is extremely cumbersome because of the many shape parameters involved (see Figs. 1, 2, 3), and since analytical solutions present fundamental difficulties and pitfalls, designers tend to favour rule of thumb methods. The present paper contains a general review of the theoretical work done at The Royal Aircraft Establishment, which was limited to the case of zero incidence. This limitation is not a severe one, as flight at high speeds often implies low incidence. Incidences which are not negligible involve the solution of another fundamental problem (that of the lift distribution).

Flow about Cones at Very High Speeds

1957 ◽  
Vol 8 (4) ◽  
pp. 384-394 ◽  
Author(s):  
H. K. Zienkiewicz
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Analytic Solution ◽  
Vibrational Excitation ◽  
Circular Cone ◽  
Approximate Analytic Solution ◽  
High Speed Flow ◽  
High Speeds ◽  
Speed Flow ◽  
Very High

Summary:Effects of vibrational excitation and dissociation of air on inviscid high speed flow past a circular cone, at zero incidence, with an attached shock wave, are studied on the assumption of thermal equilibrium. A numerical solution of the problem is outlined and an approximate analytic solution for the flow between the surface of the cone and the shock wave is developed. Two numerical examples are given as an illustration and compared with the corresponding solutions assuming constant air properties.

A Critical Review of German Research on High-Speed Airflow

1946 ◽  
Vol 50 (432) ◽  
pp. 899-934 ◽  
Author(s):  
R. Smelt
Keyword(s):  
High Speed ◽  
Great Increase ◽  
National Physical Laboratory ◽  
High Speed Flow ◽  
Fundamental Study ◽  
Speed Flow ◽  
Physical Laboratory ◽  
Operational Problem ◽  
German Research ◽  
The Subject

Even before 1939 the problems of high-speed flow were receiving a great deal of attention in the German aeronautical world. Their leading aerodynamicists, Prandtl, Busemann and Schlichting among others, had contributed largely to the theory of compressible fluid flow, and basic experimental research in the high-speed field had begun both at Aachen and at Göttingen. The activity in Germany in this particular field before the war was, in fact, much greater than in Britain, where Mr. Lock and his co-workers at the National Physical Laboratory carried practically the entire responsibility for such work.The great increase in aircraft speeds during the war, and in particular the arrival of jet propulsion, completely changed our attitude to the subject in Britain. What had been an absorbing fundamental study became, quite suddenly, an important operational problem, looming large in every new fighter design.

A new approach for numerical-diffusion control of flux-vector-splitting schemes for viscous-compressible flows

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Paragmoni Kalita ◽  
Anoop K. Dass ◽  
Jongki Hazarika
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Scaling Function ◽  
High Speed Flow ◽  
Diffusion Term ◽  
New Approach ◽  
Numerical Diffusion ◽  
Content Type ◽  
Speed Flow ◽  
Flux Vector Splitting

Purpose The flux vector splitting (FVS) schemes are known for their higher resistance to shock instabilities and carbuncle phenomena in high-speed flow computations, which are generally accompanied by relatively large numerical diffusion. However, it is desirable to control the numerical diffusion of FVS schemes inside the boundary layer for improved accuracy in viscous flow computations. This study aims to develop a new methodology for controlling the numerical diffusion of FVS schemes for viscous flow computations with the help of a recently developed boundary layer sensor. Design/methodology/approach The governing equations are solved using a cell-centered finite volume approach and Euler time integration. The gradients in the viscous fluxes are evaluated by applying the Green’s theorem. For the inviscid fluxes, a new approach is introduced, where the original upwind formulation of an FVS scheme is first cast into an equivalent central discretization along with a numerical diffusion term. Subsequently, the numerical diffusion is scaled down by using a novel scaling function that operates based on a boundary layer sensor. The effectiveness of the approach is demonstrated by applying the same on van Leer’s FVS and AUSM schemes. The resulting schemes are named as Diffusion-Regulated van Leer’s FVS-Viscous (DRvLFV) and Diffusion-Regulated AUSM-Viscous (DRAUSMV) schemes. Findings The numerical tests show that the DRvLFV scheme shows significant improvement over its parent scheme in resolving the skin friction and wall heat flux profiles. The DRAUSMV scheme is also found marginally more accurate than its parent scheme. However, stability requirements limit the scaling down of only the numerical diffusion term corresponding to the acoustic part of the AUSM scheme. Originality/value To the best of the authors’ knowledge, this is the first successful attempt to regulate the numerical diffusion of FVS schemes inside boundary layers by applying a novel scaling function to their artificial viscosity forms. The new methodology can reduce the erroneous smearing of boundary layers by FVS schemes in high-speed flow applications.

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