Jet Effects on Coflow Jet Airfoil Performance

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2013

This paper conducts numerical investigations for a 15% thickness Co-Flow Jet (CFJ) airfoil performance enhancement, which includes the variation of lift, drag, and energy expenditure at Mach number 0.03, 0.3, and 0.4 with jet momentum coefficient Cµ = 0.08. The angle of attack(AoA) varies from 0 • to 30 •. Two-dimensional simulation is conducted using a Reynolds-averaged Navier-Stokes (RANS) solver. A 5th order WENO scheme for the inviscid flux and a 4th order central differencing for the viscous terms are used to resolve the the Navier-Stokes equations. Turbulence is simulated with the one equation Spalart-Allmaras model. The study shows that at constant Cµ, the maximum lift coefficient is increased with the increasing Mach number due to the compressibility effect. However, at M=0.4, the airfoil stalls with slightly lower AoA due to the appearance of strong λ shock wave that interrupts the jet and trigger boundary layer separation. The drag coefficients vary less with the Mach number, but is substantially increased at Mach 0.4 when the AoA is high due to shock wave-boundary layer interaction and wave drag. The power coefficient is decreased when the Mach number is increased from 0.03 to 0.3. This is again due to the compressibility effect that generates stronger low pressure suction effect at airfoil leading edge, which makes the CFJ pumping easier and require less power. For the same reason of shock appearance at M=0.4 when the AoA is high, the power coefficient is significantly increased due to large entropy increase. Overall, the numerical simulation indicates that the CFJ airfoil is very effective to enhance lift, reduce drag, and increase stall margin with high Mach number up to 0.4 at low energy expenditure.

A wind tunnel test of baseline airfoil NACA 0015 and CFJ0015-065-065 model was conducted in the Wind tunnel wall test section of the Department of Mechanical Engineering at KUET, Bangladesh. The primary goal of the test was to investigate and compare the airfoil aerodynamic characteristics over a wide range of Angle of Attack (AOA) and with a wind tunnel free stream velocity of 12m/s , Re = 1.89×10 5, C µ = 0.07 at M = 0.030 kg/s. The CFJ increases C L max by 82.5% and decreases Drag by 16.5% at Stall AOA when compared to the baseline air foil. The main goal is to proof that Flow separation is controlled and delayed with the use of CFJ Technique over an Airfoil.

31st AIAA Applied Aerodynamics Conference, 2013

The two dimensional flow of an oscillating SC1095 airfoil with Co-Flow Jet (CFJ) flow control is simulated using Unsteady Reynolds Average Navier-Stokes (URANS). A 5th order WENO scheme for the inviscid flux, a 4th order central differencing model for the viscous terms and the one equation Spalart-Allmaras model for the turbulence are used to resolve the flow. The Mach number is 0.3 and Reynolds number is 3.93 × 10 6 at reduced frequency from 0.05 to 0.2. The simulated results for the baseline agree reasonably well with the experiments for no-stall, mild-stall and deep-stall cases. The CFJ pitching airfoil is found to increase the airfoil performance for every flow studied. At C µ = 0.08 the lift is increased by 32% and the drag is decrease by 80%. Considering only the aerodynamic forces applied on the airfoil and not the pumping power, (L/D) ave for this case reach an outstanding 118.3. When C µ is increased, the average drag becomes negative, proving the feasibility of a CFJ helicopter blade using its pump as the only source of power. Due to the removal of dynamic stall, CFJ airfoil is able to remove the sharp moment drop at high angle of attack. Nomenclature CF J Co-flow jet AoA Angle of attack LE Leading Edge T E Trailing Edge ZN M F Zero-net mass-flux S Planform area c Profile chord U Flow velocity q Dynamic pressure 0.5 ρ U 2 p Static pressure ρ Air density ω Angular velocity of oscillatioṅ m Mass flow M Mach number ∞ Free stream conditions j Jet conditions α 0 Mean angle of attack

5th Flow Control Conference, 2010

The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift enhancement, drag reduction, and stall margin increase. Digital Particle Image Velocimetry, flow visualization and aerodynamic forces measurements are used to reveal the insight of the CFJ airfoil mixing process.

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A flying wing personal aerial vehicle (PAV) is designed using a co-flow jet airfoil (CFJ); it is designed to take-off and land on regular roads and highways, at take-off speed of 60mph. The advantages of using CFJ throughout the entire PAV are the enhanced lift/stall margin and thrust generation. It has a targeted range of 500miles, at a cruise mach number of 0.3 at an altitude of 10,000ft with a payload of 3 passengers. The aspect ratio achieved is 2.5 with the addition of an elliptical wing to increase the wing span of the PAV. The mass flow of the jet that covers the surface of the wings needed is of 19kg/s, requiring a power of 684hp (510kW) to pump the jets to such mass flow rate. Given these conditions, the CFD analysis is still in progress.

32nd AIAA Applied Aerodynamics Conference, 2014

This paper is the Part I of a parametric study on CFJ airfoils. A trade study is performed for a series of CFJ airfoils based on the NACA 23121 airfoil on the injection location, suction location, suction size, angle of attack (AoA), momuntum coefficient , airfoil thickness, Reynolds number and their resulting effects on the lift, drag, moment and energy consumption. The two dimensional flow is simulated using steady and unsteady Reynolds Average Navier-Stokes (RANS). A 5th order WENO scheme for the inviscid flux, a 4th order central differencing model for the viscous terms and the one equation Spalart-Allmaras turbulence model are used. The Mach number is 0.15 and Reynolds number is 6.4 × 10 6. CFJ airfoils are shown to be effective at increasing the lift and reducing the drag drastically. The jet location and the AoA are found to be influential parameters for the energy consumption and aerodynamic efficiency. The pitch-down moment and energy consumption are reduced when the suction is located more upstream. The lift and drag are improved when the suction is located more downstream. The pumping power decreases when the AoA is increased before the apparition of a recirculation region. When the AoA is further increased, the energy consumption is increased because of the increased jet total pressure losses due to the strong adverse pressure gradient and separated flow.

2nd AIAA Flow Control Conference, 2004

A novel subsonic airfoil circulation augment technique using co-flow jet(CFJ) to achieve superior aerodynamic performance for subsonic aircraft is proved numerically by CFD simulation. The advantages of co-flow jet airfoil include high lift at high angle of attack, ultra high C l /C d at cruise point, and low penalty to the overall cycle efficiency of the airframe-propulsion system. Unlike the conventional circulation control (CC) airfoil which is only suitable for landing and taking off, the CFJ airfoil can be used for the whole flying mission. No blunt leading and trailing edge is required so that the pressure drag is small. No moving parts are needed and make it easy to be implemented and weight less. The jet to enhance the circulation will be recirculated. Compared with the CC airfoil, the recirculating CFJ airfoil will significantly save fuel consumption because: 1) the power required to energize the jet is less; 2) no penalty to the jet engine thrust and efficiency due to the disposed jet mass flow since the jet mass flow is recirculated. For the NACA2415 airfoil studied, at low AOA with moderate momentum jet coefficient, the coflow jet airfoil will not only significantly enhance the lift, but also dramatically reduce the drag, or even generate the negative drag (thrust). The mechanism is that the coflow jet can control the pressure drag by filling the wake, and could generate negative pressure drag greater than the friction drag. This may allow the aircraft to cruise with very high aerodynamic efficiency. At high AOA, both the lift and the drag are significantly higher than the airfoil with no flow control, which may enhance the performance of taking off and landing within short distance.

52nd Aerospace Sciences Meeting, 2014

Pitching airfoils with Co-Flow Jet (CFJ) flow control are simulated using Unsteady Reynolds Average Navier-Stokes (URANS) at Mach number 0.4 with reduced frequency of 0.1. The flow is transonic with shock wave boundary layer interaction. A 5th order WENO scheme for the inviscid flux, a 4th order central differencing model for the viscous terms and the one equation Spalart-Allmaras model for the turbulence are used to resolve the flow. The airfoil oscillate around its mean AoA of 10 • with amplitude of 5 • , 7.5 • and 10 •. The study demonstrates that the CFJ pitching airfoil is very effective to remove dynamic stall at high Mach number of 0.4. The performance is significantly enhanced with radically increased lift, reduced drag, and decreased moment variation. Nomenclature CF J Co-flow jet AoA Angle of attack LE Leading edge T E Trailing edge BL Boundary layer ZN M F Zero-net mass-flux M Mach number α 0 Mean angle of attack α 1 Amplitude of oscillation ω Angular velocity of oscillation S Planform area c Profile chord ρ Air density U Flow velocity q Dynamic pressure 0.5 ρ U 2 p Static pressurė m Mass flow ∞ Free stream conditions j Jet conditions k Reduced frequency ω c/(2 U ∞) τ Dimensionless time 2 t U ∞ /c

2022

An active flow control method as CoFlow-Jet (CFJ) is implemented on the NACA 0024 airfoil at the chord-based Reynolds number of 1.5×105. For this purpose, an in-house solver based on the Reynolds averaged Navier-Stokes equations in two-dimensional, incompressible and unsteady form with the SST-k-ω turbulence model is prepared. Several levels of jet momentum coefficient (Cμ) are studied to achieve a proper momentum coefficient for each angle of attack (α). The findings demonstrate that at Cμ=0.06, the lift coefficients at low attack angles (up to α =15̊) dramatically increase. Furthermore, the dynamic stall at the given Reynolds number and with the lowered frequency of 0.15 is explored. In the instance of Cμ=0.07, the lift coefficient curve does not show a noticeable stall feature compared to Cμ=0.05, suggesting that a more powerful stronger jet can entirely control the dynamic stall. The impact of raising the Reynolds numbers from 0.5 × 105 to 3 × 105 on this active flow control is ...

Circulation Control technology is a very effective way of achieving high lift forces required by aircraft during take-off and landing. This technology can also directly control the flow field over the wing. Compared to a conventional high-lift system, a Circulation Control Wing (CCW) can generate comparable or higher lift forces during take-off/landing with fewer or no moving parts and much less complexity. In this work, an unsteady three-dimensional Navier-Stokes analysis procedure has been developed and applied to Circulation Control Wing configurations. The effects of 2-D steady jets and 2-D pulsed jets on the aerodynamic performance of CCW airfoils have been investigated. It is found that a steady jet can generate very high lift at zero angle of attack without stall, and that a small amount of blowing can eliminate vortex shedding at the trailing edge, a potential noise source. It is also found that a pulsed jet can achieve the same high lift as a steady jet at lower mass flow rates, especially at a high frequency, and that the Strouhal number has a more dominant effect on the pulsed jet performance than just the frequency or the free-stream velocity.

Journal of the American Helicopter Society, 1998

A numerical study was conducted to investigate the effect of an array ofzero-mass "synthetic" jets on the aerodynamic characteristics of the NACA-0012 airfoil. Flowfield predictions were made using a modified version of the NASA Ames "ARCZD" unsteady, hvo-dimensional, compressible Navier-Stokes flow solver. An unsteady surface transpiration boundary condition was enforced over a user-specified portion of the airfoil's upper andlor lower surface to emulate the time variation of the mass flux out from and into the airfoil's surface. Here, a sinusoidal function which describes the approximate time behavior of the instantaneous mass flux across the airfoil's surface was used. Numerical results have indicated that zero-mass jets can, with the careful selection of their peak amplitude and frequency, enhance the lift characteristics of airfoils (helicopter rotor blades, wings, etc.). Effects of the jet peak suction and blowing velocities, oscillation frequency, and jet surface placement on the time histories of the sectional lift, drag and moment are presented for hvo angles of attack and a free stream Mach number of 0.60. Flowfield results that provide insight into the mechanics of the interaction behveen the array of jets and the developing houndary layer over the airfoil are presented.

Jurnal Asiimetrik: Jurnal Ilmiah Rekayasa & Inovasi

The computational study discusses the application of the co-flow jet technique as a fluid flow control device on the NACA 0015 airfoil. The numerical equation used is the RANS equation with the k-ε turbulence model. There are three variations of the mesh proposed in this paper. The first variation is a fine mesh with 100,000 elements. The second variation is a medium mesh with 50,000 elements. Meanwhile, the third variation is coarse mesh with 25,000 elements. Based on the mesh independence test results, the mesh with the lowest error value is the fine mesh. Co-flow jet is proven to control fluid flow on the upper side of NACA 0015. Co-flow jet can also improve the aerodynamic performance of NACA 0015 by increasing Cl and decreasing Cd. The increase in Cl was 114% and the decrease in Cd was 24%. The fluid flow separation on the upper side of the airfoil can also be handled well by the co-flow jet.

Sādhanā, 2019

In this work, flow separation control has been conducted for the S809 aerofoil at a high Reynolds number using synthetic jet technology. The aerodynamic characteristics of the aerofoil have been compared in detail at different angles of attack, for the cases with and without adoption of synthetic jet. Numerical methods are employed for predicting flow structure and performance of the aerofoil. In addition, main parameters of the synthetic jet are optimized by the orthogonal experimental design, and dual jets are also employed for the comparison to a single jet. The results show that the flow separation at large angles of attack can be eliminated or greatly reduced by the synthetic jet, due to the mixing of low-energy fluid in boundary layer with high-energy fluid produced by the synthetic jet. The lift-to-drag ratio has been considerably increased by the synthetic jet for the critical condition, deep stall condition and complete stall condition as well. The maximum jet velocity of the synthetic jet is found to have the biggest effect on flow separation control. Furthermore, compared with single synthetic jet, the dual jets can make much better improvement on flow separation control of the aerofoil, especially at the complete stall condition.

AIAA Journal (2012)

Large-eddy simulations of flow around a circulation control airfoil (using a Coanda jet blowing over its trailing surface) are performed to investigate the influence of jet-nozzle-lip thickness on airfoil performance. The airfoil geometry is only slightly changed from our previous LES study [Nishino et al., Physics of Fluids, Vol. 22, 2010, 125105] to study three different nozzle-lip thickness cases; the geometry inside the nozzle is maintained the same. The results show that the jet profile across the nozzle exit is insensitive to the nozzle-lip thickness; however, the jet flow downstream of the nozzle exit decelerates more rapidly and thus the circulation around the airfoil decreases as the nozzle-lip thickness increases. It is subsequently shown that this effect is mostly cancelled out by adjusting the jet blowing rate in such a way that the difference of momentum loss arising from the nozzle lip is taken into account, demonstrating that the performance of a Coanda jet on a circulation control airfoil is determined not only by the jet momentum at the nozzle exit but also by the momentum loss behind the nozzle lip. These results suggest that it may be useful to define a new jet momentum coefficient that takes account of the momentum loss due to the nozzle lip, which can be roughly estimated once the velocity of the flow above the nozzle lip is known.

Advances in Science and Technology Research Journal, 2021

Improved Blowing and Suction System (IBSS) is a novel concept that can be effectively implemented in future aircraft to improve the aerodynamic performance of aircraft wings. The proposed IBSS consists of a regular wing without its secondary control surfaces and with a Pump. The injection and suction system is used to create additional flow without disturbing the main flow over the aerofoil which effectively delays the boundary layer separation. The injection and suction areas are kept constant and they are located just below the maximum thickness point and suction is created close to the trailing edge. This paper presents a detailed numerical analysis of the proposed IBSS and the study shows that the stalling angle of attack is increased by 60% while the coefficient of lift is increased 37.5% compared to the baseline aerofoil. Also, the commercially used coflow jet (CFJ) method stalls at a 12° angle of attack whereas with the proposed IBSS method the stall occurs at a 16° angle of ...