scholarly journals Numerical Study on the Effect of an Off-Surface Micro-Rod Vortex Generator Placed Upstream NACA0012 Aerofoil

2021 ◽  
Vol 321 ◽  
pp. 01011
Author(s):  
Abderrahim Larabi ◽  
Michael Pereira ◽  
Florent Ravelet ◽  
Tarik Azzam ◽  
Hamid Oualli ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Passive Control ◽  
Numerical Study ◽  
Vortex Generator ◽  
Adverse Pressure Gradient ◽  
Control Device ◽  
Local Flow ◽  
Moderate Reynolds Number ◽  
Flow Deceleration ◽  
Drag Ratio

In this paper, 3D numerical simulations have been carried out to enhance the understanding of a flow over a passive control device composed of micro cylinder with, d/c = 1.34% placed in the vicinity of NACA0012 aerofoil wing, by means of γ–Reθt transition sensitive turbulence model meant to predict the separation induced by transition achieved for aerofoils operating at moderate Reynolds number (Re = 4.45×105). Results show that the separation of the boundary layer has been eliminated by the passive static vortex generator at stall regime due to the injection of free-stream momentum to the boundary layer. The early transition to turbulent state overcomes the local flow deceleration of an adverse pressure gradient and remains sticked to the wall the boundary layer. Furthermore, the wing aerodynamic performance are improved as drag is reduced and lift is enhanced which is straight forward linked to the lift to drag ratio gain that varies from 22.68% to 134.17% at post stall angles of attack.

Numerical Study of Boundary Layers With Reverse Wedge Flows Over a Semi-Infinite Flat Plate

2009 ◽  
Vol 77 (2) ◽  
Author(s):  
R. Ahmad ◽  
K. Naeem ◽  
Waqar Ahmed Khan
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Numerical Study ◽  
Boundary Layer Equation ◽  
Wedge Angle ◽  
Adverse Pressure Gradient ◽  
Problem Solution ◽  
Weighted Residual Method ◽  
Boundary Layer Problem ◽  
Layer Problem

This paper presents the classical approximation scheme to investigate the velocity profile associated with the Falkner–Skan boundary-layer problem. Solution of the boundary-layer equation is obtained for a model problem in which the flow field contains a substantial region of strongly reversed flow. The problem investigates the flow of a viscous liquid past a semi-infinite flat plate against an adverse pressure gradient. Optimized results for the dimensionless velocity profiles of reverse wedge flow are presented graphically for different values of wedge angle parameter β taken from 0≤β≤2.5. Weighted residual method (WRM) is used for determining the solution of nonlinear boundary-layer problem. Finally, for β=0 the results of WRM are compared with the results of homotopy perturbation method.

Numerical Study of a Vibrating Sub-Boundary Layer Vortex Generator

2005 ◽  
Author(s):  
Kamarul Ahmad ◽  
William McEwan ◽  
John Watterson ◽  
Jonathan Cole
Keyword(s):  
Boundary Layer ◽  
Numerical Study ◽  
Vortex Generator

An Experimental Investigation of Passive Control Device: Blade Wake Interaction on a Ultra High Lift Turbine Profile

2008 ◽  
Author(s):  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Francesco Bertini ◽  
Ennio Spano
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Passive Control ◽  
Control Device ◽  
Boundary Layer Transition ◽  
Critical Conditions ◽  
Ensemble Averaging ◽  
Layer Transition ◽  
High Lift

The transition of the boundary layer subjected to unsteady wake-passing in a linear cascade of ultra high lift profiles has been investigated at the Avio Aerodynamics Laboratory. The blade profiles are representative of the turbine nozzle mid section of a long range aeroengine. Measurements were performed at the cruise Reynolds number. A surface hot-film array was adopted to survey the boundary layer nature and the periodic variations related to the passing wakes. A phase-locked ensemble averaging technique was employed in order to separate the random fluctuations from the periodic ones. Results have been represented in space-time plots in order to provide an overall view of the time-dependent phenomena in terms of the quasi wall shear stress statistical moments, that are important parameters for the analysis of the boundary layer transition and separation. Passive control devices may be adopted to suppress boundary layer laminar separation at critical conditions (low Reynolds numbers, ultra high lift profiles). In the present experimental investigation a wavy step device has been mounted on the suction side of the blade. The effects of this boundary layer control device on the transition process and profile losses have been investigated at cruise Reynolds number, with and without incoming wakes.

Leading Edge Contamination of a C-D Compressor Blade Using Large Eddy Simulation

2020 ◽  
Author(s):  
S. Katiyar ◽  
S. Sarkar
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Separation Bubble ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Suction Surface ◽  
Local Flow ◽  
Flow Acceleration ◽  
Eddy Simulation ◽  
Large Eddy

Abstract A large-eddy simulation (LES) is employed here to predict the flow field over the suction surface of a controlled-diffusion (C-D) compressor stator blade following the experiment of Hobson et al. [1]. When compared with the experiment, LES depicts a separation bubble (SB) in the mid-chord region of the suction surface, although discrepancies exist in Cp. Further, the LES resolves the growth of boundary layer over the mid-chord and levels of turbulence intensity with an acceptable limit. What is noteworthy that LES also resolves a tiny SB near the leading-edge at the designed inflow angle of 38.3°. The objective of the present study is to assess how this leading-edge bubble influences the transition and development of boundary layer on the suction surface before the mid-chord. It appears that the separation at leading-edge suddenly enhances the perturbation levels exciting development of boundary layer downstream. The boundary layer becomes pre-transitional followed by a decay of fluctuations up to 30% of chord attributing to the local flow acceleration. Further, the boundary layer appears like laminar after being relaxed from the leading edge excitation near the mid-chord. It separates again because of the adverse pressure gradient, depicting augmentation of turbulence followed by the breakdown at about 70% of chord.

scholarly journals Effect of Micro-Vortex Generator in Hypersonic Inlet

2011 ◽  
pp. 10-13
Author(s):  
Vivek V. Kumar ◽  
Surendra Bogadi
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Vortex Generator ◽  
Adverse Pressure Gradient ◽  
Actual Case ◽  
Hypersonic Inlet ◽  
Hypersonic Speeds ◽  
Structured Meshes ◽  
Free Stream Mach Number ◽  
Micro Vortex Generator

In the present study computational tests were carried out to get an understanding of the flow field in a pure mixedcompression hypersonic inlet at a free stream Mach number of 7 and an altitude of 35km. Structured meshes have been used for depicting the motion of fluid inside the inlet. First, a grid has been selected after conducting a grid study. Two dimensional simulations were carried out with standard sst k-ω model using FLUENT. Computational results are compared with the available data. The results obtained from the computational tests revealed several important flow field details at hypersonic speeds. The basic shock structure inside the inlet was obtained. The boundary layer formed inner side of the engine had an adverse pressure gradient on the top ramp. Due to this the boundary layer thickens and the static pressure starts to decrease whose effect leads till the trailing edge of inlet. By providing small wedge shaped Micro-Vortex Generator (MVG) where the shockboundary layer occurs we can smooth the boundary layer formed inside the inlet. Thus there will be more efficient compression than the actual case. The results obtained in the present series of tests, could help the hypersonic inlet design optimization at offdesign condition

scholarly journals Experimental Investigation of the Vortex Flow around an Axisymmetric Body with the Five-Hole Probe and Hot Wire Probe

2020 ◽  
Author(s):  
amir farajollahi ◽  
Mojtaba Dehghan Manshadi ◽  
Kazem Hejranfar
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Incidence Angle ◽  
Vortex Generator ◽  
Adverse Pressure Gradient ◽  
Axisymmetric Body ◽  
The Body ◽  
Vortical Flow ◽  
Hot Wire ◽  
Wire Probe

Abstract Anaxisymmetric body experiences the vertical flow around itself at incidence angle. If the adverse pressure gradient is significant, the boundary layers separated and a vortex is formed. The flow over a submarine at AOA (angle of attack) has specified separation of boundary layer and large vortex structures around the body. This flow influences body drag, acoustic and maneuverability. A propermethod to decrease and control the impacts of this separated flowis to use vortex generator. The mainobjective of the present study is to investigate the flow field around a Suboff model with applying the vortex generator by using the hot wire and five-hole probe in 0° ≤ α ≤ 20° angles of attack. The novelty of present study is application of two experimental method, (hot wire probe and five-hole probe) which can help to precisely study the structure of three-dimensional vortical flow field, the boundary layer velocity profiles and probability of the separation on the model with and without existence of vortex generator. The results indicate that vortex generators significantly decrease cross-flow separation, the size of vortices and the vortical flow.

scholarly journals The effects of minute vortex generator jet in a turbulent boundary layer with adverse pressure gradient

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110232
Author(s):  
Mohammad Javad Pour Razzaghi ◽  
Cheng Xu ◽  
Yue Liu ◽  
Yasin Masoumi
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Turbulent Flows ◽  
Velocity Ratio ◽  
Vortex Formation ◽  
Vortex Generator ◽  
Adverse Pressure Gradient ◽  
Passive Flow Control ◽  
Vortex Generator Jet

Experimental and numerical analysis of active and passive flow control is an important topic of practical value in the study of turbulent flows. This paper numerically analyzed the effects of an air microjet on an adverse pressure gradient turbulent boundary layer over a flat plane. Experimental data were employed to verify the numerical modeling. Vortex formation and development were then studied by changing the microjet to inflow velocity ratio (VR) and microjet angles. According to the results, the best values of the angles [Formula: see text] and [Formula: see text] for various velocities were found to be 30° and from 60° to 90°, respectively. Moreover, at VRs = 1, 2, and 4, the [Formula: see text] values (the distance at which the complete vortex persisted in the flow) were 0.058, 0.078, and 0.18, respectively. Compared to VR = 1, the vortex strength for VRs = 2 and 4 grew by 3.5 and 6.8 times, respectively. When the microjet was added to the flow, the highest variation in the Reynolds stress along the x-direction from VR = 1–4 was 10%. The corresponding values along the y and z- directions were 15% and 2.7 times, respectively.

scholarly journals Study of Vortex Generator Effect on Airfoil Aerodynamics Using the Computational Fluids Dynamics Method

2020 ◽  
Vol 3 (2) ◽  
pp. 23
Author(s):  
Siti Aisyah Ayudia ◽  
Artoto Arkundato ◽  
Lutfi Rohman
Keyword(s):  
Boundary Layer ◽  
Lift Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Vortex Generator ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Separation Flow ◽  
Main Thing ◽  
Dynamics Method

The lift force is one of the important factors in supporting the aircraft flying capabilities. The airplane has a section called the aircraft wing. In particular, the wing section of aircraft is called the airfoil. One of the efforts to increase the lift force is to make the flow of air fluid at the top of the airfoil more turbulent. Turbulent flow can attract momentum from the boundary layer, the result of this momentum transfer has energy that is more resistant to the adverse pressure gradient which can trigger the flow separation. Efforts that can be made to reduce separation flow and increase lift force are the addition of a turbulent generator on the upper surface of the airfoil, one type of turbulent generator is a vortex generator, a vortex generator can accelerate the transition from the laminar boundary layer to the turbulent boundary layer. This study was conducted with the aim of knowing the effect of the vortex generator on the aerodynamics of NACA-4412 using the computational fluid dynamics method. The main thing that will be investigated is the effect of the straight type vortex generator application on the lift coefficient, by comparing the plain airfoil and airfoil that has been applied to the vortex generator to vary the angle of attack. The variation of the angles of attack are 0º, 5º, 10º, 15º and the placement of the vortex generator is 24% of the leading edge. The results obtained that the lift coefficient changes with increasing angle of attack and the application of a vortex generator to an airfoil can increase the lift coefficient than a plain airfoil. The optimum increase in lift coefficient is at the angle of attack of 5º as much as 13%.

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