Near-Field Effectiveness of the Sub-Boundary Layer Vortex Generators Deployed in a Supersonic Intake

2020 ◽  
pp. 383-393
Author(s):  
G. Humrutha ◽  
K. P. Sinhamahapatra ◽  
M. Kaushik
Keyword(s):  
Boundary Layer ◽  
Near Field ◽  
Vortex Generators

Mean-Flow Measurements in the Boundary Layer and Wake and Wave Field of a Series 60 CB = 0.6 Ship Model—Part 2: Scale Effects on Near-Field Wave Patterns and Comparisons with Inviscid Theory

1993 ◽  
Vol 37 (01) ◽  
pp. 16-24
Author(s):  
J. Longo ◽  
F. Stern ◽  
Y. Toda
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Scale Effects ◽  
Near Field ◽  
Wave Profile ◽  
Wave System ◽  
Mean Flow ◽  
Wave Elevation ◽  
Wave Patterns ◽  
Field Wave

Part 2 of this two-part paper presents additional results from a towing-tank experiment conducted in order to explicate the influence of wavemaking by a surface-piercing body on its boundary-layer and wake and provide detailed documentation of the complete flow field appropriate for validating computational methods. In Part 1 (Journal of Ship Research, Dec. 1992), wave profile, local and global wave-elevation, and mean-velocity and pressure field measurements for Froude numbers 0.16 and 0.316 for a 3.048 m Series 60 CB = 0.6 hull form are presented and discussed to point out the essential differences between the flows at low and high Froude number and to assess the nature of the interaction between wavemaking and the boundary layer and wake. In Part 2, scale effects on the near-field wave patterns are examined through wave profile and local and global wave-elevation measurements for 1.829 and 3.048 m models and Froude numbers 0.316, 0.3, and 0.25. The bow-wave amplitude and divergence angle are larger and the stern waves smaller for the smaller model. The latter scale effect is well known, but the former one is a new and unexpected result. Also, comparisons are made between the experimental results and those from a wavy inviscid-flow method, which provides an evaluation of the capabilities of the computational method. Although the computations predict the gross features of the wave system and velocity and pressure fields, they do not simulate the complex details of either the wave system or the flow field, especially close to the hull and wake centerplane.

Thermal performance enhancement in a wedge duct with in-line pin fins combined with vortex generators

2019 ◽  
Vol 29 (8) ◽  
pp. 2545-2565
Author(s):  
Safeer Hussain ◽  
Jian Liu ◽  
Lei Wang ◽  
Bengt Ake Sunden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Vortex Generators ◽  
Content Type ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Enhancement

Purpose The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs). Design/methodology/approach This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers. Findings The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins. Originality/value VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.

Boundary Layer Control of an Axial Compressor Cascade Using Nonconventional Vortex Generators

2015 ◽  
Author(s):  
Ahmed M. Diaa ◽  
Mohammed F. El-Dosoky ◽  
Mahmoud A. Ahmed ◽  
Omar E. Abdel-Hafez
Keyword(s):  
Boundary Layer ◽  
Passive Control ◽  
Axial Compressor ◽  
Vortex Generators ◽  
Boundary Layer Control ◽  
Geometrical Parameters ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Flow Equations ◽  
Layer Control

Boundary layer control plays a decisive role in controlling the performance of axial compressor. Vortex generators are well known as passive control devices of the boundary layer. In the current study, two nonconventional types of vortex generators are used and their effects are investigated. The used vortex generators are doublet, and wishbone. Three dimensional turbulent compressible flow equations through an axial compressor cascade are numerically simulated. Comparisons between cascade with and without vortex generators are performed to predict the effect of inserting vortex generator in the overall performance of the axial compressor. Results indicate that using vortex generators leads to eliminate or delay the separation on the blade suction surface, as well as the endwall. Furthermore, the effects of the vortex generators and their geometrical parameters on the aerodynamic performance of the cascade are documented. In conclusion, while the investigated vortex generators cause a slight increase in the total pressure loss, a significant reduction in the skin friction coefficient at the bottom endwall is found. This reduction is estimated to be about 46% using doublet and 32% using wishbone.

On the generation of sound by turbulent boundary layer flow over a rough wall

1984 ◽  
Vol 395 (1809) ◽  
pp. 247-263 ◽  
Keyword(s):  
Boundary Layer ◽  
Near Field ◽  
Spectral Characteristics ◽  
Rigid Wall ◽  
Control Surface ◽  
Aerodynamic Noise ◽  
Stream Velocity ◽  
Main Stream ◽  
Wall Roughness ◽  
Boundary Layer Turbulence

The production of sound by scattering of the near field of low Mach number boundary-layer turbulence by a rough, rigid wall is examined on the basis of Lighthill’s theory ( Proc. R. Soc. Lond . A 211, 564 (1952)) of aerodynamic noise. The radiation is expressed in terms of the turbulence pressure spectrum on a control surface that is parallel to the mean plane of the wall and at a stand-off distance equal to the height of the wall roughness elements, the surface irregularities being modelled by a distribution of hemispherical bosses on an otherwise plane wall. The intensity of the sound produced by unit area of the wall varies as the sixth power of the main stream velocity and, for given wall roughness, increases as the boundary-layer thickness decreases. These conclusions are in accord with experimental observations reported by Hersh { AIAA paper no. 83-0786) of the generation of high frequency sound by turbulent flow from sand-roughened pipes, and it is shown how, for moderately rough pipes, the theory reproduces the spectral characteristics of Hersh’s data.

scholarly journals Computational Modelling of Three Different Sub-Boundary Layer Vortex Generators on a Flat Plate

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3107 ◽  
Author(s):  
Ruben Gutierrez-Amo ◽  
Unai Fernandez-Gamiz ◽  
Iñigo Errasti ◽  
Ekaitz Zulueta
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Flow Separation ◽  
Computational Modelling ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Primary Vortex ◽  
Good Efficiency ◽  
Local Boundary ◽  
Passive Flow Control

Flow separation is the source of several problems in a wind turbine including load fluctuations, lift losses, and vibrations. Vortex generators (VGs) are passive flow control devices used to delay flow separation, but their implementation may produce overload drag at the blade section where they are placed. In the current work, a computational model of different geometries of vortex generators placed on a flat plate has been carried out throughout fully meshed computational simulations using Reynolds Averaged Navier-Stokes (RANS) equations performed at a Reynolds number of R e θ = 2600 based on local boundary layer (BL) momentum thickness θ = 2.4 mm. A flow characterization of the wake behind the vortex generator has been done with the aim of evaluating the performance of three vortex generator geometries, namely Rectangular VG, Triangular VG, and Symmetrical VG NACA0012. The location of the primary vortex has been evaluated by the vertical and lateral trajectories and it has been found that for all analyzed VG geometries the primary vortex is developed below the boundary layer thickness δ = 20 mm for a similar vorticity level ( w x m a x ). Two innovative parameters have been developed in the present work for evaluating the vortex size and the vortex strength: Half-Life Surface S 05 and Mean Positive Circulation Γ 05 + . As a result, an assessment of the VG performance has been carried out by all analyzed parameters and the symmetrical vortex generator NACA0012 has provided good efficiency in energy transfer compared with the Rectangular VG.

An efficient method for predicting zero-lift or boundary-layer drag including aeroelastic effects for the design environment

2015 ◽  
Vol 119 (1221) ◽  
pp. 1451-1460
Author(s):  
J. A. Camberos ◽  
R. M. Kolonay ◽  
F. E. Eastep ◽  
R. F. Taylor
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Near Field ◽  
Field Method ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Design Environment ◽  
Navier Stokes Equations ◽  
Induced Drag ◽  
Flight Regimes

AbstractOne of the aerospace design engineer’s goals aims to reduce drag for increased aircraft performance, in terms of range, endurance, or speed in the various flight regimes. To accomplish this, the designer must have rapid and accurate techniques for computing drag. At subsonic Mach numbers drag is primarily a sum of lift-induced drag and zero-lift drag. While lift-induced drag is easily and efficiently determined by a far field method, using the Trefftz plane analysis, the same cannot be said of zero-lift drag. Zero-lift drag (CD,0) usually requires consideration of the Navier-Stokes equations, the solution of which is as yet unknown except by using approximate numerical techniques with computational fluid dynamics (CFD). The approximate calculation of zero-lift drag from CFD is normally computed with so-called near-field techniques, which can be inaccurate and too time consuming for consideration in the design environment. This paper presents a technique to calculate zero-lift and boundary-layer drag in the subsonic regime that includes aeroelastic effects and is suitable for the design environment. The technique loosely couples a two-dimensional aerofoil boundary-layer model with a 3D aeroelastic solver to compute zero-lift drag. We show results for a rectangular wing (baseline), a swept wing, and a tapered wing. Then compare with a rectangular wing with variable thickness and camber, thinning out from the root to tip (spanwise direction), thus demonstrating the practicality of the technique and its utility for rapid conceptual design.

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