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Hybrid Laminar Flow concept (Reneaux, 2004). In the Hybrid Laminar Flow concept, the laminar flow can be maintained by the application of suction in the region of the leading edge to control the development of cross-flow and TollmienSchlichting instabilities combined with favourable pressure gradients in the spar box region (Figure 7). It is first necessary to ensure that the attachment line remains laminar and to avoid contamination phenomenon. Anti contamination devices have to be used to avoid the contamination of the attachment line by the turbulent structures coming from the fuselage. Gareth Williams (2010) from Airbus (Smart Fixed Wing Aircraft (SFWA) project) recently in his presentation pointed out that, so far two types of laminar flow technology have evolved. Natural laminar flow, exploiting shape and materials, Hybrid laminar flow, where an active system induces laminarity, typically suction (Figure 8). SFWA investigates the potential of both, but will focus on Natural Laminar Flow as it avoids recognized complexity and weight penalty of the Hybrid counterpart.
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Drag reduction for aerial vehicles has a range of positive ramifications: reduced fuel consumption, larger operational range, greater endurance and higher achievable speeds. The aerodynamic drag breakdown of a transport aircraft at cruise shows that the skin friction drag and the lift-induced drag constitute the two main sources of drag, approximat...
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... In particular, it can improve the efficiency of the whole industry by mainly increasing the fuel efficiency to achieve the goal of annual 1. 5% fuel efficiency improvement set by IATA, dedicated to reducing carbon emission and fuel cost [15]. Moreover, it indirectly increases the maximum operational range [16] and minimizes the potential danger from wake turbulence [17]. ...
Civil aviation has grown rapidly over the past hundred years as demand from air travellers has increased. Since the mid to late 20th century, there have been recurring global energy crises due to political and economic upheavals. In this international context, airlines have tended to operate less draggy, more fuel efficient aircraft in order to maximise profits through fuel cost savings . To this end, aircraft manufacturers have historically tried a variety of methods to address the issue of drag reduction.This paper highlights the importance of three drag reduction methods utilized on modern subsonic airliners by introducing their basic principle and evaluating their effectiveness based on previous research and typical experiments. This paper summarizes and analyzes different approaches to reduce drag in civil aviation. It first investigates the principle behind frictional, induced, and profile drag in theoretical aspects. It then discusses in detail the biomimicry microstructure based on shark skin and its uniqueness on aircraft fuselages surface to reduce frictional drag, the split scimitar winglet and its ideal performance to reduce induced drag when compared with other wingtip devices with different cant angles. The newly introduced adaptive lifting surface changes the wings geometric configuration momentarily, and its ability to reduce profile drag at different stages of flight. This paper also comprehensively compares both the benefits and potential compromises of these drag reduction methods.
... Percentages of the stable regions are computed and found that there were almost negligible instabilities in e-v plane for a high torsional spring rate (c) and for large values of relaxation length (σ), there is a small increase in the stable region. This paper presents the effects of the modification of the landing gear on the drag coefficient of the fighter aircraft and hence effects on the range and endurance of the fighter aircraft [3][4][5][6][7][8][9][10][11]. ...
In the present paper, the effect of the change of position and change of dimension (modification) of the landing gear on the drag reduction of the fighter aircraft have been studied. Modeling of the landing gear of model 1 to model 4, have been done using Catia V5 and numerical simulation have performed using CFD to evaluate the coefficient of drag, velocity, turbulence intensity and static pressure. The modification of landing gear results in a reduction of the drag coefficient. The drag coefficient for model 1 was found 1.37. Whereas, for model 4 the drag coefficient was reduced to 0.46. The maximum drag reduction was achieved for model 4 is about 66%. The drag reduction of fighter aircraft would directly affect the fuel consumption, rang, and endurance of the fighter aircraft.
... The parameters of the lift coefficient model are the wing aspect ratio, fuselage width, sweepback angle, wing span, and Mach number. The drag coefficient is determined by an empirical drag build-up method of profile drag, induced drag, and wave drag [40]. The main component of profile drag is the friction/form drag considering turbulent flow with compressibility effects for the fuselage, wing, horizontal and vertical stabilizers, and the nacelle [41]. ...
More often than not, airlines use aircraft in operating scenarios beyond their optimal design conditions, which negatively affects their performance characteristics. These effects are statistically reflected in flight operational data, which are indirectly constrained by air transportation management as well as aircraft design. In this research, we develop a data-enhanced methodology for modeling dynamic flight simulations of aircraft to enable accurate estimation of performance parameters. The relevant flight phases and constraints of these simulations are determined by employing supervised machine learning on the flight data. The methodology is demonstrated by simulating flights across representative short-, medium-, and long-haul sectors using data shared by our airline partner. We compare the fuel burn and flight time calculation results with those from the Bréguet range and endurance equations, from an available open-source flight performance model, and from the reference data for validation. The developed dynamic flight simulation model is designed in such a way to enable accurate flight performance analysis even when high-fidelity force analyses and control models are absent, which is common in preliminary design frameworks. This will further enable incorporating flight data into aircraft design processes.
... In the Airbus design, the use of Sharklets is claimed to have reduced wingtip vortices and reduced total drag [1]. Other researchers have also discussed and compared winglets on aircraft, as presented by Jahanmiri [2] and Scholz [3]. ...
The Aerodynamic performance of an object is very dependent on the flow of fluid through it and the geometric shape of the object. The use of Unmanned Aerial Vehicle (UAV) demands high aerodynamic performance because it strongly supports the cruising range and fuel or battery used. By reducing drag and increasing the lift optimally, the resulting lift to drag ratio will get maximum results. This study compares the use of winglets in UAVs at low Reynolds numbers. This is very important because generally UAVs are used at low Reynolds numbers. The freestream used is Re = 2.34 x 10 ⁴ on several low to high angle of attack. The type of airfoil used is Eppler 562 which is equipped with a winglet. Winglets used are simple winglets, blended winglets, and wingtip fence. The geometry was analyzed using numerical simulations namely computational fluid dynamic (CFD). The turbulent model used in this study is K-ω SST on Ansys 19.1. From this study it was found that the use of a wingtip fence produced the best aerodynamic performance compared to other configurations. In addition, the use of a wingtip fence can delay stall and separation better than simple and blended winglets.
... Zhou et al. [14] have recently reported some drag reduction for perforated wall/slot on three-dimensional wing at supercritical conditions, whereas Jiang et al. [30] have reported the reduction in buffeting through use of a punched hole near the airfoil trailing edge. Reviews of work done in drag-reduction methods can be found in [8,28,[31][32][33][34][35] and more recently in the works of Mrinal and Humrutha [36] and Gaitonde [37]. ...
A computational study has been carried out to assess the effectiveness of a porous medium as a passive control device suitable for reducing the drag in a normal-shock-wave/boundary-layer interaction at transonic speeds with a view toward application in aircraft wings. Reduction in overall drag is achieved via recirculation inside the porous medium, which primarily weakens the shock structure and hence reduces the wave drag. The study has been carried out for a Mach 1.3 normal-shock-wave/boundary-layer interaction on a flat plate in the presence of a porous medium beneath the region of interaction. The computations are performed as steady-state RANS calculations using Menter’s SST \(k-\omega /k-\epsilon \) model for turbulence closure. A parametric study that investigates the dependency of the effectiveness of control on dimensions of the cavity (length and depth), relative position of the cavity, and porosity of the medium has been carried out. It is observed that the change in overall drag is pronounced for parameters which result in significant changes to the size of the lambda-shock structure, such as the length of the cavity upstream of the inviscid shock location. Among the parameters investigated, porosity is seen to strongly affect the boundary-layer properties, with increase in porosity resulting in higher viscous drag.
... Gambar 2. Definisi aspect ratio pada rancangan sayap [2] Banyak studi telah dilakukan untuk mengurangi induced drag pada pesawat selain menambah aspect ratio. Pada [3] direview beberapa penelitian yang telah dilakukan untuk mengurangi drag pada pesawat terbang, salah satunya adalah menggunakan winglet. Adapun studi mengenai wingtip device telah dimulai sejak tahun 1920an, [4] [5] [6] melakukan studi terhadap sayap yang diberi pelat datar diujungnya. ...
Abstrak Winglet dirancang untuk meningkatkan kinerja aerodinamis sayap. Desainnya dimaksudkan untuk meminimalkan drag yang dihasilkan oleh pusaran winglet. Alat ujung sayap sendiri memiliki berbagai macam tipe. Studi eksperimental dilakukan untuk melihat pengaruh penerapan winglet terhadap performa aerodinamis sayap. Empat jenis perangkat winglet diuji melalui pengujian terowongan angin untuk mengetahui desain optimal yang memberikan dampak yang lebih baik pada peningkatan aerodinamis. Hasil penelitian menunjukkan bahwa desain nomor 3 memberikan pengaruh tertinggi terhadap peningkatan rasio gaya angkat terhadap gaya hambat sayap. Abstract Winglet devices are design to improve aerodynamic performance of the wing. Its design is intended to minimized drag that produced by wing tip vortices. Wingtip device itself has various type. Experimental study was carried out to observe effect of winglet implementation to the aerodynamic performance of the wing. Four type of wingtip devices was tested by means of wind tunnel testing to find out the optimum design that provide better impact on aerodynamic improvement. The result shows that design number 3 provide highest effect on increasing lift to drag ratio of the wing. PENDAHULUAN Sayap pesawat terbang dirancang untuk menghasilkan gaya angkat yang cukup sesuai kebutuhan perancangan. Gaya angkat yang dihasilkan oleh sayap diperoleh dari perbedaan tekanan udara yang terjadi di bagian bawah dan di bagian atas permukaan sayap. Tekanan yang terjadi pada permukaan bawah lebih besar daripada tekanan yang terjadi di atas permukaan sayap. Hal ini memicu aliran udara yang bertekanan tinggi dari bawah sayap bergerak ke arah udara bertekanan yang lebih rendah di bagian atas melalui ujung sayap. Pergerakan udara dari bawah menuju atas sayap, dikombinasikan dengan kecepatan terbang pesawat akan menghasilkan pusaran di ujung sayap yang disebut sebagai wingtip vortices yang ukurannya semakin ke belakang akan semakin membesar. Wingtip vortices ini menimbulkan salah satu komponen utama gaya hambat pada pesawat yang dinamakan sebagai lift induced drag atau biasa disingkat sebagai induced drag. Pada Gambar 1 terlihat bahwa induced drag dominan pada kecepatan rendah, sedangkan pada kecepatan tinggi yang dominan adalah parasite drag.
... In a subsonic transport aircraft, the majority of the drag is contributed by skin friction during the cruise condition [5][6][7]. The drag reduction can be obtained by suppressing the turbulent skin friction by manipulating boundary layer [8], using devices such as riblets [9] and large eddy breakup devices [10]. ...
... The drag reduction can be obtained by suppressing the turbulent skin friction by manipulating boundary layer [8], using devices such as riblets [9] and large eddy breakup devices [10]. However, an increased cost of manufacturing and maintenance is a concern [6]. The vortex generators re-energize the boundary layer (by generating vortices) and delay the flow separation [11]. ...
... In a subsonic transport aircraft, the majority of the drag is contributed by skin friction during the cruise condition [5][6][7]. The drag reduction can be obtained by suppressing the turbulent skin friction by manipulating boundary layer [8], using devices such as riblets [9] and large eddy break-up devices [10]. ...
Numerical simulations are performed to study the outboard airfoil of advanced technology regional aircraft (ATRA) wings with five different variable camber continuous trailing edge flap (VCCTEF) configurations. The computational study aims to improve the aerodynamic efficiency of the airfoil under cruise conditions. The design of outboard airfoil complies with the hybrid laminar flow control design criteria. This work is unique in terms of analysis of the effects of VCCTEF on the ATRA wing's outboard airfoil during the off-design condition. The Reynolds-Averaged Navier-Stokes equations coupled with the Spalart-Allmaras turbulence model are employed to perform the simulations for the baseline case and VCCTEF configurations. The current computational study is performed at an altitude of 10 km with a cruise Mach number of 0.77 and a Reynolds number of 2.16 × 10 7. Amongst all five configurations of VCCTEF airfoils studied, a flap having a parabolic profile (VCCTEF 123) configuration shows the maximum airfoil efficiency and resulted in an increase of 6.3% as compared to the baseline airfoil.
... In order to reach these objectives, the principal aeronautical industries focused their attention both on the design of new efficient engines but also on the aerodynamical design of more performing wings. In particular, it is important to underline that to maintain a laminar and attached flow over the wing generates a drag reduction respect to a turbulent flow and, in this matter, the aeronautical industry started to develop "Laminar Flow Control" techniques (see (Jahanmiri, 2011) for an exhaustive review), able to reduce drag also of about the 15%, as reported in figure 3, leading to a fuel saving and to a reduction of gas emissions. In this context (but also in other industrial context where a drag reduction is required), it is clear the importance of a full comprehension of the transition phenomena, a problem still open and not fully solved, in order to develop efficient and robust control techniques. ...
Stability analysis is a very powerful tool in order to investigate the properties of a complex fluid system. For example, it turns out to be very useful for understanding the laminar&;turbulent transition scenario or to investigate the dynamic evolution of a fluid in very complex situations such as wakes, jets, recirculation bubbles etc. In this work, linear stability theory has been applied to very different situations. In the first part, we investigate the stability characteristics of a 2D T shaped micro mixer, a very common device in micro- and nano-fluidics, fitted with an anisotropic superhydrophobic texture on the walls of the outlet channel, using a global stability approach. A parametric analysis has been carried out by varying the surface properties, i.e. the equivalent slip length of the grooves and their orientation angle with respect to the direction of the main pressure gradient. We characterize both the primary and the secondary instability of such kind of flow. We show that in some conditions, the presence of the SHS generates an unsteady instability apt to improve the mixing in the channel. The second and third parts concern the linearized study of an incompressible laminar viscous jet passing through a circular aperture. In particular, in the second part we considered the flow passing through a hole of zero thickness. We compute the response of such kind of flow to harmonic perturbations. We characterize both the spatial amplification of perturbations and the impedance, defined as the ratio between the pressure jump and the flow rate across the hole, which is a key quantity to investigate the response of the jet to an acoustic forcing. Owing to the strong spatial amplification of the perturbation the computation requires a special treatment of the downstream boundary conditions, and quickly becomes impossible when the Reynolds number is increased. We introduce a method based on the analytical continuation in the complex plane of the axial coordinate, thus extending the range of Reynolds number investigated up to Re = 3000. The third part concerns the stability of a jet through a circular aperture in a thick plate. Experiments and simulations show that if the plate is thick enough, strong periodic oscillations can occur and lead to characteristic whistling tones, suggesting the existence of a feedback mechanism that supports self-sustained oscillations. We show that, contrary to previous expectations, the feedback mechanism is not related to acoustics and an instability can exist even in a purely incompressible description. We investigate the stability properties of such kind of flow using both the Nyquist criterion, based on the impedance analysis, and the classical global stability approach. Finally, we perform a structural-sensitivity analysis showing that the instability of such kind of flows is connected to the presence of a recirculation region in the hole. In the last part of the thesis we apply the stability analysis to the production of sound in a more traditional configuration, namely the birdcall, where the flow is constrained to pass through two successive holes in curved rigid plates. Although the production of sound in this classical whistle is a compressible phenomenon, an incompressible approach can provide some useful information at least in the region near the hole. We thus initially perform a purely incompressible stability analysis. We identify the critical conditions, the global frequencies, and discuss the structure of the resulting global eigenmodes. In order to reintroduce and evaluate compressible effects, which can be relevant in the cavity between the two holes, we model the cavity as a Helmholtz resonator and couple it to the incompressible simulation. Finally, a fully compressible stability analysis is performed in order to check the accuracy of these simplified approaches in term of critical conditions, global frequencies and structure of the modes.
... T HE economic and ecological success of an aircraft is bound up with its aerodynamic performance [1,2], especially the drag, which is one of the most important parameters in aircraft design. Even a little drag reduction may lead to nonnegligible benefits for the fuel consumption, payload, emissions, noise pollution, and so on. ...
... The base pressure in high speed flow has been divided in to passive and active control [6]. [7] studied flows sudden expansion for high speed compressible subsonic flows in circular pipes. ...
An experimental investigation for over expanded, perfectly expanded and under expanded supersonic jets is presented to study the effectiveness of a static cylinder to reduce base drag at Mach 2 through a converging diverging nozzle for a cross-sectional duct nozzle area ratio of 9. A static cylinder of 2 mm diameter at 2 mm from the side wall of a square duct and 8 mm from the square nozzle exit in the base region is installed as a passive control device. Base pressures in the wake flow after sudden expansion of jets in to a square nozzle have been measured. The length width ratio of the duct is 10. The jets were operated at different nozzle pressure ratios in the range from 2 to 9. The flow field in the square duct was also observed for all cases. Static cylinder as a passive controller was found to reduce the base drag as high as 59 percent at NPR = 9 and 14 percent at NPR = 6. The base pressure depends on Mach number, area ratio, length to width ratio, and nozzle pressure ratio (NPR). When flow from the nozzle is over expanded, the static control is ineffective till NPR is 6. The level of expansion plays a vital role. The flow flux in the square duct remains almost identical with and without control for most of the cases. However, at higher NPRs namely 6, 7.8, and 9 the control results in an increase as well as a decrease in the wall pressure along the duct. Passive control of the base flow is effective for higher NPRs. The flow field for perfectly expanded nozzle is dominated by the shock waves.
