Various Angles Of Attack Research Articles

Wake flow evolution behind a circular cylinder with two perpendicular slits at various angles of attack

Wake flow evolution behind a circular cylinder with two perpendicular slits at various angles of attack

NumericalStudy of Turbulent Flows over a NACA 0012 Airfoil: Insights into Its Performance and the Addition of a Slotted Flap

This work provides a comprehensive overview of various aspects of airfoil CFD simulations. The airflow around a 2D NACA 0012 airfoil at various angles of attack is simulated using the RANS SST turbulent flow model and compared to experimental data. The airfoil is then modified with a slotted flap and additionally the angle of the flap is altered. The flow model is subsequently coupled to a heat transfer model to compare the isothermal versus non-isothermal performance. The airfoil with the slotted flap shows increased CL and CD values compared to the standard NACA 0012. Larger flap angles further increase the CL and CD. The lift and drag coefficients show no difference in the non-isothermal model compared to the isothermal model, indicating the isothermal model is sufficient for this system. The 3D model without wingtips shows a similar CL to the 2D model as it effectively has an infinite span. Adding a wingtip reduces the lift coefficient, as the air can flow around the wingtip, increasing the pressure on top of the wing. Overall, these results match the behavior expected from wing theory well, showing how CFD can be effectively applied in the development and optimization of wings, flaps, and wingtips.

Transient analysis of thermo-sensitive cavitating flows over a hydrofoil in various angles of attack and temperatures

The present work aims to contrastively study the cavitation intensity, temperature drop, turbulence kinetic energy as well as the changed lift and drag forces for various free-stream temperatures and angle of attacks (T∞=68.64-88.54K,AOA=3.5o-12o) in a thermo-sensitive cavitating flow. The simulation results indicate that the higher temperature and larger angle of attack intensify the cavitation thermal effect and increase the temperature drop jointly. The difference lies in the large angle of attack promotes the cavitation development, but the high temperature weakens the cavitation intensity and reduces the vapour volume. The influential mechanisms exist in the cavity evolution, vorticity, turbulence kinetic energy as well as angle of attack are revealed. The high-level turbulence kinetic energy occurs in the unstable flow regions, include the cavity tail, the separation zone on the suction surface and cavitation vorticity region. For the attached cavity, the larger angle of attack suppresses the turbulence kinetic energy due to the enhanced cavity adhesion on hydrofoil surface. The turbulence kinetic energy caused by cavity shedding and cavity collapse becomes more obvious at a smaller angle of attack. The study on the force evolution show that increased temperature and angle of attack weaken the fluctuation amplitudes of lift and drag forces and reduce the occurrence frequencies of peak values, and then the averages of lift and drag forces are increased. The temperature rise increases the average of lift force and reduces the average of drag force, which is characterized by a increase of lift-drag ratio. Meanwhile, the quantitative results include transition of shedding period and temperature drop in cavity thickness direction are also analysed.

Tonal Noise Control Versus Performances on NACA0015 Hydrofoil

Strong correlation between boundary layer excitation and hydrofoil eigenmode occurs for specific angles of attack and Reynolds numbers, resulting in strong tonal noise emissions under certain circumstances. This study aims to analyze the performance of vibration control methods such as truncated trailing edge or boundary layer triggering. The study explores the conditions for hydro elastic trailing edge vibrations on a hydrofoil clamped in a hydrodynamic tunnel, with tests performed for Reynolds numbers up to 1.2 × 106 and various angles of attack up to 10°. Experiments were conducted on a clamped 0.1 m chord NACA0015 aluminum hydrofoil, with measurements taken for both vibrations and hydrodynamic components such as lift, drag, and moment. The goal of the study is to closely understand the impact of vibration control on hydrofoil efficiency. This could be very beneficial for those who are working on optimizing profile design. The study first presents the experimental setup, followed by an analysis of the hydrofoil’s vibratory response and a presentation of the effectiveness of control solutions. Then, the performance of these solutions is discussed followed by a conclusion.

Гидродинамика сетных жестких безузловых конструкций

Rigid netting structures are elements, parts of commercial fishing gear and aquaculture cages. They serve to enclose or filter hydrobionts, they are engineering structures. Rigid netting structures can be used as inserts in commercial fishing gear, as well as selective gratings and elements that prevent hydraulic backwater in trawls. They are also elements of stationary fishing gear, such as winders or other fishing gear or barriers. In aquaculture cages, rigid netting structures, the elements of which have a sufficiently large value of the longitudinal and transverse modulus of elasticity E, are parts that ensure the strength of the netting structures. Mesh rigid structures are made of plastic or aluminum rods in the form of cylinders, which can be either smooth or twisted. The article considers the application of a numerical method for determining the hydrodynamic characteristics of mesh rigid structures using the software developed by the authors. A schematization of a rigid netting structure, a mathematical model based on Navier-Stokes partial differential equations, a computational domain, initial and boundary conditions are proposed. The calculation was carried out on a regular computational grid using an implicit finite-difference scheme using the methods of coordinate-wise splitting, linearization of nonlinear equations with subsequent correction of nonlinear coefficients, and solution of the obtained tridiagonal systems by the sweep method. The results of numerical experiments are presented in the form of visualization of pressure on the surface of various mesh structures at various angles of attack.

Evaluation of wing performance for NACA 4415 using subparametric finite element transforms

The goal of the current research is to improve the lift performance of an aerodynamic device for commercial application by performing accurate aerodynamic computations and flow analyses of NACA 4-digit airfoil designs. An enhanced aerodynamic characteristic, which has been estimated effectively by interpreting the impacts of Reynolds numbers at various angles of attack, is crucial for a cost-effective airfoil shape. Numerous Reynolds numbers have been used in the analysis of these aerodynamic properties. Investigations were carried out using subparametric finite elements and a unique approach for higher order triangular element meshing in relation to the NACA 4415 airfoil design. This approach provides precise boundary node information for the airfoil design, resulting in improved calculations of the lift coefficient, drag coefficient, and lift-to-drag ratio. Moreover, it effectively addresses the challenges faced in aerospace research pertaining to flow analysis, thereby reducing the complexities involved. The evaluationof the airfoil shape and analysis for incompressible flow over the NACA 4415 airfoil design could improve the overall effectiveness of the aerodynamic vehicle. Any vehicle's aerodynamic surface must go through a number of tests before being launched. Modern technology can be incorporated into the design process to reduce the high costs associated with these testing processes. The current flow analysis and aerodynamic investigations exhibit a high degree of accuracy, and the use of HO elements lowers the expense of the experiment.

Hydrodynamic characteristics of fine-mesh minnow netting for sampling nets

Fine-mesh minnow nettings with a high solidity ratio (defined as the ratio of the projected area to the total area enclosed by the outline area) of 0.44–0.72 were used to investigate the hydrodynamic characteristics for various angles of attack (0°–90°). A brief summary of knotless plane netting in an expanded solidity ratio range of 0.075–0.75 is given. Experimental results show that the drag coefficient of minnow netting in a solidity ratio range of 0.44–0.72 is 0.13 to 0.035 in the parallel case and 1.60 to 1.86 in the normal case. The dual effect of the solidity ratio on the drag coefficient of knotless plane netting is confirmed in a wider solidity-ratio range. The maximum lift coefficient of minnow netting increases from 0.55 to 1.02 for an angle of attack of 40° as the solidity ratio increases from 0.44 to 0.72. The proposed empirical formulas of the hydrodynamic model in terms of drag and lift coefficient for knotless plane netting varying a wider solidity ratio and angle of attack are more accurate than those of previous models. Therefore, the present formulas allow precise numerical calculation for the optimal design of sampling nets and fishing gear.

Numerical Investigation for Single-Phase and Two-Phase Flow in Duct Banks with Multi Types of Vortex Generators

This paper examines the numerical work of the thermal convection over tube banks with winglets through the heat exchanger in two parts under turbulent conditions. The first section investigates the influence of two-phase (water and air) flow on the performance of two kinds of vortex generators (Delta and Rectangular) winglets across the oval tube banks. The second section studied the performance of four types of winglets (Delta, Rectangular, Zikzak, and Sinusoidal wavy), circular and oval tubes, forward and downward configurations, and various angles of attack (15°

Comparative Study and Aerodynamic Analysis of Rectangular Wing Using High-Lift Systems

High-lift systems are designed to expand the flight envelope and have a most important effect on the size of the wing, economy, and safety of many airliner configurations. Even a small increment of lift using a high-lift system can significantly impact an aircraft’s profitability. The effective design of the airfoil shape with the required aerodynamic performance is still difficult. In the early days, the designs of airfoils were randomly set up and tested in the flow section, and then, the Wright brothers emerged with a cambered section. NACA has provided an appropriate airfoil definition that supports us in making airfoil designs using formulas, not randomly. This paper describes the influence of aerodynamic analysis of wing with flaps at various deflection angles. Aerodynamic variables for the aircraft wing, which is made up of the NACA airfoil 6412 model with and without flaps, have been studied at various angle of attack (AOA) (i.e., -4, -2, 0, 2, 4, 6, 8, 10, 12, and 16) and different Mach number at 0.2, 0.3, and 0.4. Also, the analysis was done for the 15000 ft altitude to check the density effects for the real-time applications. The coefficients of lift and drag are gained by examining the pressure distribution over the surface of the wing. Lift increases as the approach ascends from a low to a high angle of attack, and the most extreme lift is produced at a specific point. After that, when the angle of attack increases further, the drag component increases, so the stall occurs at that point in time. The results showed that the NACA 6412 airfoil obtained the maximum lift at 14°, and the lift value started to decrease. The CFD computations are performed in Ansys Fluent by performing hybrid mesh using ICEM-CFD. The analysis is performed for various configurations of the wing section, and the effects of flow parameters like angle of attack, altitude, and the gap distance between the main wing and slotted flap were compared to identify the better configurations.

An Analytical Solution for Unsteady Aerodynamic Forces on Streamlined Box Girders with Coupled Vibration

This paper is a contribution to analyzing the aerodynamic forces on a streamlined box girder (SBG) with coupled vibration in a potential flow. The key enabling step was to assume that the normal velocity of the airflow at an arbitrary point on the surface of the SBG was equal to the normal velocity of the surface motion. The aerodynamic drag force, lift force, and pitching moment were expressed as functions of the motion state of the SBG and the SBG’s shape-related parameters. To investigate the applicability of this force model, the analytical solution at various angles of attack was compared with a numerical simulation in a viscous flow. The results imply that the amplitude of the analytical lift force and pitching moment agree well with the numerical results under the angles of attack of 0° and ±3°. Furthermore, the analytical drag force effectively predicts the second-order phenomenon resulting from the multiplication of the vertical and torsional vibration velocities. As a consequence, the present analytical solution provides an effective method for analyzing the aerodynamic forces acting on SBGs with coupled vibration.

Group gliding of three manta rays in multiple formations

Manta rays are often seen gliding and cruising in organized formations in oceanariums. We posed the following questions: (1) Why do they glide in a group? (2) What is the best group gliding formation? (3) How does the gliding attack angle affect the hydrodynamics of group gliding? To solve these questions, we first established a numerical model of the manta ray and then conducted numerical simulations of three manta rays engaged in tandem, orthotriangular, and antitriangular variable attack angle group gliding. The results show that group drag reduction can be produced in all three arrangements, and the critical attack angle of lift is −2°. In the tandem formation, the manta ray at the head of the group always experiences the least drag, and the lift of each individual is noticeably different. In the orthotriangular formation, the system drag reduction is more difficult to produce, and the lift of each individual is similar. In the antitriangular formation, system drag reduction can be produced at all attack angles due to the uniqueness of the flow field pressure distribution, and thus it is the most ideal group gliding formation.

Airfoil Shape Optimization of a Horizontal Axis Wind Turbine Blade using a Discrete Adjoint Solver

In this study, airfoil shape optimization of a wind turbine blade is performed using the ANSYS Fluent Adjoint Solver. The aim of this optimization process is to increase the wind turbine output power, and the objective function is to maximize the airfoil lift to drag ratio (Cl/CD ). This study is applied to the NREL phase VI wind turbine, therefore, the S809 airfoil is used as a reference profile. First, for the validation of the applied numerical model, steady-state simulations are carried out for the S809 airfoil at various angles of attack. Then, the optimization is performed with the airfoil set at a fixed angle of attack, , considering three Reynolds numbers, Re =3 105,4.8 105 and 106. Next, computations are performed for the fluid flow around the optimized airfoils at angles of attack AOA= 6.1° ranging from 0° to 20°. The results show that (i) the lift to drag ratios of the optimized airfoils are significantly improved compared to the baseline S809 airfoil, (ii) this improvement is sensitive to the Reynolds number, and (iii) the Cl/CD ratios are also improved for another angle of attack values. Thereafter, the optimized airfoils are used for the design of the NREL Phase VI blade and the aerodynamic performances of this new wind turbine are assessed using the open-source code QBlade. These latter results indicate that when the blades are designed with the optimized airfoils, the wind turbine aerodynamic performances increase significantly. Indeed, at a wind speed of 10 m/s, the power output of the wind turbine is improved by about 38% compared to that of the original turbine.

Investigation of Aerodynamic Characteristics of a Two-Bladed Sailing Wind Turbine

The article examines a prototype of a wind turbine with two blades. For experimental work, a mock-up of a sailing wind turbine consisting of two blades was developed. The material of the sail blades was selected according to elasticity and lightness, cheapness, roughness of the streamlined surfaces. The study shows the aerodynamic parameters acting on the blade. The air flow velocity varied from 3 to 12 m/s. The dependence of the lifting force and the frontal barrier on the air flow velocity was obtained by turning the blades of the wind turbine so that the angle of attack was α = 00; 150; 300; 450 и 600. It is established that when the position of the blade’s changes, the lifting force and the drag force decrease. With an increase in the angle of attack α > 00 leads to a decrease in the midsection of the wind wheel with respect to the air flow. On this basis, there is a decrease in aerodynamic forces. As the speed of the air treacle increases, the speed of rotation of the wind wheel also increases. However, during the experiment it was found that the location of the blades at different angles affects the numerical value of the rotational speed. According to the conducted experiments, several values were obtained. The analysis of the obtained values is carried out. A graph is constructed based on the dependence of the wind wheel rotation frequency on the wind speed with a change in the angle of attack. A wind turbine with blades with a variable angle of attack, which, turning, gradually become more parallel to the direction of the wind. Centrifugal forces regulate the inclination of the blades, and as a result, the speed of rotation of the wind wheel, and keep the wind generator at the nominal speed of rotation.

Aerodynamic Characteristics of Blerak Winglet

The induced drag created by wingtip vortices has a significant impact on aircraft performance. Winglets are wingtip extensions that are intended to reduce the creation of vortices and increase the fuel efficiency. The present study is based on analyzing different winglets planform for aircraft at various angles of attack (AOA) to improve the aerodynamic efficiency. The Finite Volume Method in pressure-based solver along with the Realizable k - ɛ turbulence model, with standard atmospheric boundary conditions is used to do the CFD computations in ANSYS Fluent. According to the findings, an optimized BLERAK (Blended + Raked) winglet from the present study has a substantial impact on aerodynamic efficiency when compared to conventional winglets, and it is projected to yield a higher lift-to-drag ratio. The blerak winglets model gives 1.5 to 2% drag reduction than the other winglet models at angle of attack variations of 8°, 12° and 16°.

Shape Optimization of an Asymmetric Airfoil for Low Wind Speed Region having Adjoint-Based Optimization Technique

The land needed to install wind turbines is shrinking as power generation from renewable energy sources increases significantly. A large number of studies are being conducted to maximize the power extraction from wind turbines in areas with low wind speeds. Wind turbine blades play a significant role in utilizing the maximum amount of energy from the wind. The aerodynamic performance of a wind turbine blade depends on the airfoil shape. The shape optimization of an asymmetric S2027 airfoil for a low wind speed region was investigated using the adjoint-based optimization technique. The primary objectives of this study were to maximize the lift coefficient, minimize the drag coefficient, and maximize the lift-to-drag ratio. The optimization is based on the adjoint method for Reynolds number variation in the range of 2 × 105 to 5 × 105 and an angle of attack variation from 0° to 12°. A two-dimensional Reynolds–Averaged Navier–Strokes Computational Fluid Dynamics model was created with all the operating parameters and used for optimization. The aerodynamic performance was validated experimentally. For each optimization function, approximately 16 shapes were obtained. The aerodynamic performance for each optimized shape was determined under different operating conditions. Different airfoil shapes with a specific chord, leading and trailing edges, and span arrangement was obtained. The drag coefficient was reduced by 2%–30%; the lift coefficient was improved by 2%–35%, and the lift-to-drag ratio was improved up to 40%.

Aeroacoustic airfoil shape optimization enhanced by autoencoders

Aeroacoustic noise is a major concern in wind turbine design that can be minimized by optimizing the airfoils that shape the rotating blades. To this end, we present a framework for airfoil shape optimization to reduce the trailing edge noise for the design of wind turbine blades. Far-field noise is evaluated using Amiet’s theory coupled with the TNO-Blake model to calculate the wall pressure spectrum and fast turn-around XFOIL simulations to evaluate the boundary layer parameters. The computational framework is first validated using a NACA0012 airfoil at 0° angle of attack. Particle swarm optimization is used to find the optimized airfoil configuration. The multi-objective optimization minimizes the A-weighted overall sound pressure level at various angles of attack, while ensuring enough lift and minimum drag. Furthermore, traditional shape optimization techniques show difficulties to converge to the optimum, when too many shape parameters are included in the optimization. For this reason, we compare classic parameterization methods to define the airfoil geometry (i.e., CST) to a machine learning method (i.e., a variational autoencoder). We observe that variational autoencoders can represent a wide variety of geometries, with only four encoded variables, leading to efficient optimizations, which result in improved optimal shapes. When compared to the baseline geometry, a NACA0012, the autoencoder-based optimized airfoil reduces by 3% (1.75 dBA) the overall sound pressure level (with decreased noise across the entire frequency range), while maintaining favorable aerodynamic properties in terms of lift and drag.

Airflow Characteristic of UAV Quadcopter Propeller Blade Using Computational Fluid Dynamics (CFD)

In this study, the main focus is to study of air flow characteristic of UAV quadcopter propeller at incorporate blade profile using variableangle of attack (AoA)and revolution per minute (RPM) with its twisted blade using Computational Fluid Dynamics (CFD) / Ansys tool. Three propellers have been designed which Propeller 1 is untwisted while Propeller 2 and 3 twisted at certain angle. Three speeds which are 4000 rpm, 6000 rpm and 8000 rpm have been set for each propeller are being analysed using ANSYS Fluid Flow (fluent). The result shows the different thrust force generated by three propellers and Propeller 2 (33.6757 N) has the highest thrust force generated compared to Propeller 1 and 3 especially at 8000 rpm. This is due to the suitable twisting angle profile that has been set at the Propeller 2at this operating speed. For comparison, Propeller 3 produce the highest thrust force of 18.44Nat 6000 rpmexceeding Propeller 2 which is 17.81 N.To summarize, each propeller blade profile has a distinctive aerodynamic performance and should be adopted by matching the flight operating condition. Higher rpmgenerateshigherthrust force, and increaselift and drag coefficient.

Design Optimization of Grids in Grid Fins for Spacecrafts

Grid fins are a type of aero control surfaces used in missiles and rockets in place of more conventional control surfaces such as the planar fins. Conventional planar fins are designed like miniature wings whereas grid fins have smaller lattice aerostructures arranged within a box-like structure. Most grid fins have square grid aerostructures such as those used in the Falcon 9 rocket manufactured by SpaceX. This paper discusses the introduction of 3 innovative designs namely trapezoidal, triangular and hexagonal grids in two configurations - un-tapered and tapered. The taper angles will be 6, 6.5, 7 and 7.5. These new designs will be modelled and analysed using suitable software. The designed grid fins will be simulated in multiple aerodynamic conditions at various angles of attack. The exit velocity of air at the outlet of the grid fin will be measured and analysed in this paper. Once the simulation is complete, the two best designs will be 3D printed with appropriate materials at appropriate scales for wind tunnel testing. The results will be compared and validated with existing data in order to find the overall effectiveness of the designs.

Numerical Study on Flow and Noise Characteristics of an NACA0018 Airfoil with a Porous Trailing Edge

An airfoil with a porous trailing edge has a low noise emission; thus, using a porous medium is a good technique for further reduction of wind turbine noise. In this paper, to reduce airfoil trailing edge noise while minimizing the negative influence of a porous medium on aerodynamic performance, a new filling method is proposed such that a porous medium is only used in the suction side half of the trailing edge, which is more sensitive to the noise generation. The large eddy simulation (LES) technique for flow and the Ffowcs Williams and Hawkings (FW-H) method for acoustics are used. At a Reynolds number of 2.63 × 105 and various angles of attack, an NACA0018 airfoil profile with a porous trailing edge covering 20% of the chord is studied under two porous configurations, namely a fully porous and a suction-side porous trailing edge type. The results show that the flow direction, velocity magnitude, and their distributions along the boundary layer of the two porous airfoils are significantly modified due to the presence of the porous medium. The fluctuation of the pressure coefficient and the increase in the boundary layer thickness are significant at low angles of attack. As compared to the solid airfoil counterpart, the noise radiation from the newly proposed suction-side porous airfoil achieves a noise reduction of 4.3 dB at an angle of attack α = 0°, and a noise reduction of 4.07 dB at an angle of attack α = 2°.

Design and Determination of Aerodynamic Coefficients of a Tail-Sitter Aircraft by Means of CFD Numerical Simulation

Vertical take-off and landing (VTOL) aircraft have become important aerial vehicles for various sectors, such as security, health, and commercial sectors. These vehicles are capable of operating in different flight modes, allowing for the covering of most flight requirements in most environments. A tail-sitter aircraft is a type of VTOL vehicle that has the ability to take off and land vertically on it elevators (its tail) or on some rigid support element that extends behind the trailing edge. Most of the tail-sitter aircraft are designed with a fixed-wing adaptation rather than having their own design. The design of the tail-sitter carried out in this work had the particularity of not being an adaptation of a quad-rotor system in a commercial swept-wing aircraft, but, rather, was made from its own geometry in a twin-rotor configuration. The design was performed using ANSYS SpaceClaim CAD software, and a numerical analysis of the performance was carried out in ANSYS Fluent CFD software. The numerical results were satisfactorily validated with empirical correlations for the calculation of the polar curve, and the performance of the proposed tail-sitter was satisfactory compared to those found in the literature. The results of velocity and pressure contours were obtained for various angles of attack. The force and moment coefficients obtained showed trends similar to those reported in the literature.