Vortex Trapping by Different Cavities on an Airfoil
TL;DR: In this paper, the authors presented the flow over an airfoil with different cavity shapes placed on the suction surface of a symmetric airframe, and the cavity with both sharp edges showed better results in terms of lift and drag as compared to other shapes of the cavity.
Abstract: The paper presents the flow over an airfoil with different cavity shapes placed on the suction surface of a symmetric airfoil. Unsteady simulations of flow over the airfoil with and without cavities were performed by Reynolds averaged Navier-Stokes (RANS) solver. Lift and drag were checked and the separation point identified at different Reynolds numbers and different angles of attack. The airfoil with cavity produced more drag and less lift as compared to the airfoil without cavity. The cavity with both sharp edges showed better results in terms of lift and drag as compared to other shapes of the cavity.
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22 Jun 2020
TL;DR: In this article, the authors study periodic, infinitely long spanwise grooves on a laminar boundary layer over a plate for 1000 $R\phantom{\rule{0}{0ex}}{e}_{L}$ 25000 below a certain width-to-depth aspect ratio (AR), a primary vortex inside each groove causes the freestream to slip over, reducing skin friction.
Abstract: Engineered surface textures can manipulate boundary layers affecting fluid drag We study periodic, infinitely long spanwise grooves on a laminar boundary layer over a plate for 1000 $R\phantom{\rule{0}{0ex}}{e}_{L}$ 25000 Below a certain width-to-depth aspect ratio (AR), a primary vortex inside each groove causes the freestream to ``slip over'', reducing skin friction Increasing AR poses a tradeoff in drag reduction due to pressure drag from groove vertical walls Overall, transverse grooves for laminar flow can reduce total drag up to 10% compared to a flat plate, despite increasing the wetted surface area
7 citations
TL;DR: In this paper , the flow characteristics and velocity fields over the vertical axis wind turbines DU 06 W 200 airfoil developed by Delft University of Technology and some other innovative designs are examined by computational fluid dynamics (CFD) simulation and particle image velocimetry (PIV) measurements.
Abstract: In this paper the flow characteristics and velocity fields over the vertical axis wind turbines DU 06 W 200 airfoil developed by Delft University of Technology and some other innovative designs are examined by computational fluid dynamics (CFD) simulation and particle image velocimetry (PIV) measurements. In these case studies a modification of the plain airfoil upper and/or lower surfaces was applied with the assistance of different techniques. CFD was conducted using the turbulent model of RANS k- ω SST. The PIV experiments were performed using a wind tunnel test and smoke flow visualization. Different practical cases, namely riblet under surface, riblet above surface, cavity front, cavity back, double cavity, single riblet, and spoiler, were designed and examined. Moreover, two hybrid blade airfoils designed and inspired by combining the DU 06 W 200 and NACA 63215 developed by National Advisory Committee for Aeronautics (NACA) were also tested. The results show that the new design hybrid blade airfoil can significantly modify the flow pattern over the airfoil and improve aerodynamic performance. The new design hybrid blade airfoil could deliver improved efficiency for industrial applications, specifically for the design and development of vertical axis wind turbines.
6 citations
5 citations
01 Jun 2021
3 citations
TL;DR: In this article, a Computational Fluid Dynamics (CFD) investigation is carried out for analyzing the simultaneous effect of suction and cavity for controlling flow separation on NACA 0012 airfoil.
Abstract: In the present research, a Computational Fluid Dynamics (CFD) investigation is carried out for analyzing the simultaneous effect of suction and cavity for controlling flow separation on NACA 0012 airfoil. Hence, a perpendicular suction jet (jet = -90°) is employed with Rjet equal to 0.15 at Ljet = 0.1c. Simultaneously, a cavity is used at 90% of chord length (0.9c) with 20 mm width and 10 mm depth. The fluid flow is assumed to be 2D turbulent, and incompressible. The results demonstrate that lift coefficient has raised by 30% and drag coefficient has decreased by 40% at α = 14° by using simultaneous suction and cavity. The flow control method improves lift to drag ratio and stall angle has increased from 14° to 22°. Consequently, the flow separation has been delayed, the recirculation zone has gone downstream and completely eliminated by utilizing simultaneous suction and cavity as an effective flow control method.
2 citations
Cites background from "Vortex Trapping by Different Caviti..."
...Besides, several efforts have been done on the aerodynamic characteristic of the airfoil with cavity [25-28]....
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References
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TL;DR: In this paper, the steady profile of a touching pair of vortex regions with equal and opposite vorticity in a bounded uniform stream is calculated and a family of possible solutions is deduced, depending upon the magnitude of a (non-dimensionalized) parameter.
Abstract: A calculation is made of the steady profile adopted by a touching pair of vortex regions with equal and opposite vorticity in a bounded uniform stream. A family of possible solutions is deduced, depending upon the magnitude of a (non-dimensionalized) vorticity parameter. A similar calculation is carried out incorporating a flat plate normal to the stream at the upstream end of the vortex configuration. The requirement of tangential separation at the plate tip selects a unique value of the vorticity. It is found that, as the width of the plate is reduced in relation to that of the channel, the vortex profile asymptotically approaches one member of the above mentioned family. The asymptotic form of the flow in the vicinity of the plate is deduced for this case and compared with a previous calculation.
27 citations
01 Jan 2008
TL;DR: In this paper, an experimental campaign performed at CIRA CT-1 wind tunnel aimed to investigate the potential benefit obtainable using a trapping vortex cell system on a high-thick airfoil with and without steady suction and/or injection mass flow.
Abstract: This paper summarises the experimental campaign performed at CIRA CT-1 wind tunnel aimed to investigate the potential benefit obtainable using a trapping vortex cell system on a high thickness airfoil with and without steady suction and/or injection mass flow. The behaviour of a 2D model, equipped with a span wise oriented circular cavity, has been investigated. Pressure distribution on the model surface and inside the cavity and the complete flow field around the model and inside the cavity have been measured. An extensive test campaign has been carried out in the CT-1, an open circuit wind tunnel, with test section size of 305x305x600 mm 3 and maximum speed of 55 m/s. Due to the limited dimensions of the WT, the model has been mounted on the bottom wall of the wind tunnel in order to avoid blockage problems. The model represents a two dimensional high thickness airfoil with a chord length of 350mm. The model angle of attack ranges between 5.66° to 12.66° with a step of 1°. The installation of the model on the wind tunnel bottom wall presented heavy flow instability under the front part of the model. The flow instability has been solved applying a flow suction in front the model trough a porous wall installed on the bottom WT wall. The cavity has been realized with transparent material in order to allow optical access and consequently PIV measurements. The model has been designed in order to permit flow suction and/or blowing inside the cavity. The influence of different parameters has been investigated. Tests have been performed varying the wind tunnel speed (form 15 m/s, to 30 m/s), varying the suction mass flow (from 0 m 3 /h to 25 m 3 /h) varying the blowing mass flow (from 0 m 3 /h to 50 m 3 /h) applying suction and blowing at the same time, and varying the model angle of attack (AoA). In the paper the performed test campaign, the adopted experimental set-up, the data post-processing and the results' description are reported.
24 citations
"Vortex Trapping by Different Caviti..." refers methods in this paper
...The experimental results with cavity near the TE with suction system for removing the unsteady circulation in front of the model are explained by Gregorio and Fraioli [7]....
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TL;DR: In this paper, a new airfoil-design concept was developed to produce greater lift coefficients over a much broader range of operational angles of attack, to improve or eliminate stall at virtually all operational airspeeds, to increase functional lift-to-drag ratios over a greater range of operations, and to be adaptable for aircraft of both the fixed-wing and the rotarywing types.
Abstract: The research in this paper is the result of an experimental study regarding a new airfoil‐design concept, which is developed to produce greater lift coefficients over a much broader range of operational angles of attack, to improve or eliminate stall at virtually all operational airspeeds, to increase functional lift‐to‐drag ratios over a greater range of operational angles of attack, and to be adaptable for aircraft of both the fixed‐wing and the rotary‐wing types. The writer has combined his effort with L. L. Smith, and a U.S. Patent, entitled “Airfoil,” Patent No. 4,606,519, was obtained on August 19, 1986. Patents were also obtained or are pending in other countries. The experimental results, obtained by using the new airfoil‐design concept, have been compared with experimental results obtained from a conventional NACA 23012 airfoil. Flight performance tests by using a 2.134‐m (7.0 ft) model and remote‐control devices, as well as flow‐separation studies, were also performed. The results were compared ...
23 citations
TL;DR: In this paper, the effects of trapped vortex cell (TVC) on the aerodynamic performance of a NACA0024 wing model were investigated experimentally at Re ǫ = 106 and $$ 6.67\times 10^{5}$$¯¯.
Abstract: The effects of a trapped vortex cell (TVC) on the aerodynamic performance of a NACA0024 wing model were investigated experimentally at Re = 106 and $$6.67\times 10^{5}$$
. The static pressure distributions around the model and the wake velocity profiles were measured to obtain lift and drag coefficients, for both the clean airfoil and the controlled configurations. Suction was applied in the cavity region to stabilize the trapped vortex. For comparison, a classical boundary layer suction configuration was also tested. The drag coefficient curve of the TVC-controlled airfoil showed sharp discontinuities and bifurcative behavior, generating two drag modes. A strong influence of the angle of attack, the suction rate and the Reynolds number on the drag coefficient was observed. With respect to the clean airfoil, the control led to a drag reduction only if the suction was high enough. Compared to the classical boundary layer suction configuration, the drag reduction was higher for the same amount of suction only in a specific range of incidence, i.e., α = −2° to α = 6° and only for the higher Reynolds number. For all the other conditions, the classical boundary layer suction configuration gave better drag performances. Moderate increments of lift were observed for the TVC-controlled airfoil at low incidence, while a 20% lift enhancement was observed in the stall region with respect to the baseline. However, the same lift increments were also observed for the classical boundary layer suction configuration. Pressure fluctuation measurements in the cavity region suggested a very complex interaction of several flow features. The two drag modes were characterized by typical unsteady phenomena observed in rectangular cavity flows, namely the shear layer mode and the wake mode.
21 citations
TL;DR: In this paper, an efficient method of constructing inviscid Batchelor-model flows is developed based on an analytic continuation of the potential part of the flow into the closed-streamline vortex region.
Abstract: An efficient method of constructing inviscid Batchelor-model flows is developed. The method is based on an analytic continuation of the potential part of the flow into the closed-streamline vortex region. Numerical solutions are presented for Batchelormodel flows past airfoils with cavities. With the airfoil and dividing streamline shape, the eddy vorticity, and the jump in the Bernoulli constant across the eddy boundary given, the program calculates the corresponding cavity shape and the entire flow.
16 citations
"Vortex Trapping by Different Caviti..." refers background or methods in this paper
...But according to Prandtl-Batchelor theorem [11] the vorticity must be constant inside the closed streamline region....
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...Inviscid Batchelor model [9−10] which is a plane steady flow of incompressible fluid past a body with vorticity constant inside and zero outside the region of closed streamlines [11]....
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