Aerodynamic Performance Analysis Research Articles

Investigation of aerodynamic performance characteristics of a wind-turbine-blade profile using the finite-volume method

Two-dimensional incompressible flow around a NACA 63–415 airfoil, which is encountered in engineering applications as a typical wind-turbine-blade profile, is investigated computationally. Aerodynamic loads and the flow mechanism over this particular blade profile are examined in detail to determine the optimum angle of attack. Simulations are performed in the range of the typical operating conditions encountered for commercial-scale wind turbines with Reynolds numbers 105≤Re≤3×106 and for angles of attack 0∘≤α≤20∘. The turbulent flow was modelled by means of the Spalart-Allmaras and the Shear-Stress Transport (SST) k-ω turbulence models to provide a direct comparison between data obtained with different models. The results obtained are compared to numerical and experimental data available in literature for validation. The aerodynamic performance analysis reveals that the optimum angle of attack for this blade profile is α=6∘ for Re≤106 and α=7∘ for Re≥1.6×106.

Aerodynamic Performance Analysis of a Curved-channel ABLE Airfoil in Supersonic Continuous and Hypersonic Rarefied Flows

An airfoil, equipped with a curved-channel ABLE, is a good alternative to increase the lift-to-drag ratio. For this purpose, a curved-channel artificial blunted leading edge (ABLE) was applied to several supersonic/hypersonic symmetrical airfoils to analyse the aerodynamic performance in low-altitude supersonic continuous flow and high-altitude hypersonic rarefied flow during the process of re-entry into the atmosphere. The compressible Navier–Stokes equations were solved using the finite volume method to analyse the aerodynamic performance and determine the optimal curved-channel ABLE airfoil for supersonic continuous flow. Thereafter, the drag reduction and lift increment efficiency of the optimal ABLE airfoil were analysed in the hypersonic rarefied flow. The variation in the aerodynamic performance of the ABLE airfoil with the Knudsen number and freestream Mach number was determined using the direct simulation Monte Carlo (DSMC) method. The results showed that with suitable ABLE configuration and parameter values, the concept of ABLE can help reduce the drag coefficient, improve the lift coefficient, and obtain a better lift-to-drag ratio in both continuous and rarefied flows without considerable aerothermal penalty. However, the drag reduction effect of the curved-channel airfoil in the rarefied flow is much lower than that in the continuous flow, because of the lower proportion of the wave drag in the total drag, and the overall aerodynamic performance is significantly deteriorated because of the rarefaction effect of the atmosphere.

Calculation Method of Aerodynamic Performance of Small Propeller with Serrated Trailing Edge

The small propeller with serrated trailing edge of the UAV has the characteristics of low aerodynamic noise. In this paper, based on the momentum-leaf theory and modified the airfoil parameters, the aerodynamic performance calculation method of the propeller with a serrated tail structure is put forward. Combined with the CDF technology of three-dimensional aerodynamic performance analysis of small propeller blades at low Reynolds number, this method was used to calculate the aerodynamic performance of the small propeller with serrated tail structure, and the calculation results were experimentally verified. The experimental results show that, using the modified airfoil parameters, the established aerodynamic performance calculation method of the tail serrated structure propeller hover state has a good effect.

Aerodynamic Performance Analysis of a Building-Integrated Savonius Turbine

The building-integrated wind turbine is a new technology for the utilization of wind energy in cities. Previous studies mainly focused on the wind turbines mounted on the roofs of buildings. This paper discusses the performance of Savonius wind turbines which are mounted on the edges of a high-rise building. A transient CFD method is used to investigate the performance of the turbine and the interaction flows between the turbine and the building. The influence of three main parameters, including the turbine gap, wind angle, and adjacent turbines, are considered. The variations of the turbine torque and power under different operating conditions are evaluated and explained in depth. It is found that the edge-mounted Savonius turbine has a higher coefficient of power than that operating in uniform flows; the average Cp of the turbine under 360-degree wind angles is 92.5% higher than the turbine operating in uniform flows. It is also found that the flow around the building has a great impact on turbine performance, especially when the turbine is located downwind of the building.

Actuator 기법을 이용한 프로펠러 3축 성분 힘/모멘트 해석

For aerodynamic performance and stability analysis of distributed propulsion aircraft which adopt many propellers/rotors, all the 3-axial components forces and moments must be properly taken into account. In this study, two actuator methods have been established to be capable of numerical simulations including all the force and moment components produced by rotor/propeller. A procedure in which the 3-axial components are transformed from the aerodynamic force and moment of blade elements has been added to actuator disk method(ADM) and actuator surface method(ASM). The numerical analyses are carried out for a single propeller of quad tilt propeller(QTP) at various flight conditions including the variation of side slip angle. The results are compared with wind tunnel test data and full CFD simulation with overset grid. All the force and moment components are found to agree very well in terms of engineering purposes and the present methods are identified to be numerically very efficient compared to full CFD. Power-on effect and longitudinal stability of the full configuration of QTP is further analyzed by carrying out the additional numerical simulations. The results indicate that the present methods is practically very useful to investigate the aerodynamic performance of distributed propulsion aircraft.

Unsteady aerodynamic performance analysis of an airborne wind turbine under load varying conditions at high altitude

The blade air loads of the Airborne Wind Turbine (AWT) may be significantly influenced by the unsteady flow-field at high altitude. Under these susceptible situations, the rotor needs in-depth considerations with respect to transient aspects. The present study focuses on the unsteady aerodynamic performance of stand-alone rotor under the influence of wind shear, yawed, and tilted configurations. The Computational Fluid Dynamics (CFD) transient simulations based on the sliding mesh approach are carried out for analyzing the unsteady behavior of the rotor by lifting the rotor assembly at an airborne altitude from the ground. All simulations are conducted at optimal operating conditions of wind speed and tip speed ratio. In-house Unsteady Blade Element Momentum (UBEM) code using the wind shear, dynamic stall, dynamic wake, and yaw /tilt model are applied to acquire an empirical assessment in terms of rotor torque, thrust, and power coefficient. Finally, the CFD simulated results are compared against the performance curves generated by the UBEM model and acceptable agreement is found within 4.1% deviation at peak operational conditions. The results further reveal that the time-varying aerodynamic loads on the rotor blade gradually achieve steady behavior after three rotation periods. Meanwhile, unique similarities are found in yawed and tilted inflow cases and a 10.7% loss in power coefficient is observed due to rotor yawed inflows. Additionally, in the absence of tower shadows, the strong flow interactions around the rotor blade impose a positive impact on power output. Despite the complexity of unsteady flow phenomena, this present study would be helpful to design a more proficient airborne rotor under the varying load conditions.

Design and aerodynamic performance analysis of a variable-sweep-wing morphing waverider

The wide speed range and large flight envelope of the hypersonic vehicle require that its aerodynamic configuration still has good aerodynamic performance at low Mach number. Therefore, the variable Mach number waverider is proposed to achieve good flight performance in a wide speed range. In this paper, based on the delta-winged variable Mach number waverider, a variable-sweep-wing morphing waverider is proposed and studied, including four specific sweep-wing configurations, namely loiter, standard, dash and wing-retracted configurations. In the current study, the aerodynamic performances of this variable-sweep-wing morphing waverider with four configurations are investigated under subsonic/supersonic/hypersonic flight conditions. At the same time, the numerical approaches employed are validated against the available experimental data in the open literature. The obtained results show that compared with the wing-retracted configuration, the best flight performance of this variable-sweep-wing morphing waverider can be achieved using different configuration for different flight condition. However, within the hypersonic speed range, the aerodynamic performance is improved through morphing but its advantages are not as large as that in the subsonic speed. Besides, effects of wing downwash and shockwave are also analyzed. In conclusion, the variable-sweep-wing morphing waverider improves both low-speed and high-speed aerodynamic performances, and it expands the flight speed range.

Design and aerodynamic performance of new Floating H-Darrieus Vertical Axis Wind Turbines

In the last decade, several countries started work on the development of Floating Vertical Axis Wind Turbines, which have significant advantages over Floating Horizontal Axis Wind Turbines. In the present work, we expose a brief history of the use of this type of wind turbines, and we contribute to understanding the existing technologies and we also propose a new design of Floating H-Darrieus Vertical Axis Wind Turbine with three stage rotors. This design solves the problem of starting a large turbine and facilitates maintenance by adopting three mechanisms Bearing Swivel Rollers at each stage. We use the Double Multiple StreamTube method for aerodynamic simulations. The numerical results of the aerodynamic performance analysis show that variable radius rotors maximize the power generated.

Flow characteristics of an axial turbine with chamber and diffuser adopted in compressed air energy storage system

Axial turbine is an important work-output device in Compressed Air Energy Storage (CAES) system. A compact chamber and a short diffuser are both adopted in the turbine to obtain higher power with lower investment. As a result, the internal flow field is also influenced significantly. In present study, internal flow characteristic of an axial turbine adopted in a new 10MW CAES system is analyzed with compact chamber and short diffuser by three-dimensional steady numerical method. The results illustrate that the isentropic efficiency obtained by the numerical method agrees well with the experiment. Analysis of aerodynamic performance indicates that maximum entropy increase is found in rotor, and the flow loss in stator also cannot be neglected. Back flow with lower velocity, higher static pressure and entropy is observed near bottom of the chamber, and non-uniform distribution of total pressure is thus formed at outlet of chamber. As a result, obvious variation of inlet attack angle of stator is observed along spanwise and circumferential direction, the entropy in stator is thus increased by 33.17%. Fluid with velocity of 23m/s is found at outlet of diffuser, which causes higher leasing velocity loss. The struts significantly reduces the pressure recover ability of diffuser by 11.42%. However, higher pressure recovery coefficient can be obtained at 0.035 m ∼ 0.135 m along axial distance of diffuser when actual inlet swirl angle is applied.

Aerodynamic Performance Characterization of Slotted Propeller: Part B Effect of Angle

In this paper, designs of slotted propeller blade were discussed numerically, in terms of aerodynamic performance and static structural analysis. Baseline APC Slow Flyer 10’ x 7’ small scale propeller blade was modified by including slots along the propeller blade. Numerical analysis has been done to determine the influence of slots angle towards thrust coefficient, power coefficient and efficiency. Simulations were performed by using ANSYS Fluent implementing k-ω turbulence model and Multiple Reference Frame to incorporate rotational speed of the propeller. The analyses were conducted at a fixed rotational speed, with variance of advance ratio. Initial slotted design is set at 180 degree and the angles were changed with 10-degree interval, ranging from 180 degree to 90 degree. The results were compared with available experimental data. For the slotted design, the result shows that inducing slots do not always lead to improvement in propeller blade performance. Improvement in thrust coefficient with the range of 0.267% to 2.71% can be seen for low advance ratio for most of slot angles. However, a significant increase in power coefficient can be observed which reduces the overall efficiency of the propeller blade. For stress and deformation, ANSYS Mechanical Static Structure was used to determine maximum Von-Mises stress, maximum Von-Mises strain, and total deformation. The analyses were conducted by using 60% long strand fiber glass reinforced nylon 6 Natural. The blade is more suitable to operate at higher velocity. At lower operational velocity, the blade tends to experience material failure as the stress exceeds stress at break.

Trajectory Estimation of Hypersonic Glide Vehicle Based on Analysis of Aerodynamic Performance

Due to high speed and high maneuverability of hypersonic glide vehicles (HGVs), the state estimation of such targets has always been a research hotspot. In order to improve accuracy of the trajectory estimation, a nonlinear aerodynamic parameter model for target estimation based on aerodynamic performance analysis is proposed. Firstly, the dynamic characteristics of the hypersonic glide vehicle during the hypersonic gliding stage was analyzed. Then, aiming at HTV-2-liked vehicle, the engineering calculation method was used to form the reference aerodynamic model for the target estimation. Secondly, a deviation model described by first-order Markov process was introduced to compensate the uncertainties of the unknown maneuver information from the target. Finally, extended Kalman filter was utilized to estimate the state of the target. The simulation results show that the proposed model is able to improve the accuracy of acceleration estimation for the HTV-2-liked hypersonic gliding vehicles.

Numerical analysis of aerodynamic performance of a floating offshore wind turbine under pitch motion

The aerodynamic performance of wind turbines is essential to evaluate their electricity-generating capability. Compared with the wind turbines with traditional fixed structures, the aerodynamic performance of floating offshore wind turbines (FOWTs) is affected by the additional platform motion, especially for the pitch motion. In view of this, the computational fluid dynamics (CFD) method with the improved delayed detached eddy simulation (IDDES) is applied. Before the numerical simulation, the CFD model of the redesigned 1:50 scale rotor from NREL 5 MW wind turbine is verified with the available experimental data and numerical comparison. Then, the aerodynamics of the FOWT under the harmonic pitch motion with different periods and amplitudes is investigated. It is shown that the aerodynamic performance of the FOWT is sensitive to these parameters of the pitch motion. First, amplitudes of the rotor thrust and torque decrease with the increment of the pitch period. In particular, the wake interference phenomenon is the most evident when the pitch period is short and the pitch amplitude is high, which may compensate some energy to the rotor. In addition, amplitudes of the rotor thrust and torque increase with the increment of the pitch amplitude. Also, the stall phenomenon happens when the pitch amplitude is high, which may impact FOWTs’ aerodynamic performance adversely. Finally, the rotor power increases under the periodic pitch motion, especially by decreasing the period or increasing the amplitude. It is concluded that the pitch motion of the platform will change the aerodynamic performance of a wind turbine and should be taken into consideration during design procedure.

Aerodynamic and Structural Characteristics of a Centrifugal Compressor Impeller

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. The performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of the compressor under centrifugal force and pressure load from the aerodynamic analysis are applied to the impeller blade and hub to perform the one-way Fluid–Structure Interaction (FSI). For the stress assessment, maximum equivalent von Mises stresses in the impeller blades are compared with the maximum allowable stress of the impeller material. The effects of varying the pressure field on the deformation and stress of the impeller are also calculated. The aerodynamic and structural performance of the centrifugal compressor at 73,000 rpm are investigated in terms of the efficiency, pressure ratio, equivalent von Mises stress, and total deformation of the impeller.

Analysis of Aerodynamic Performance of a Microscale Radial Flow Wave-rotor for Gas Turbine Topping Cycle

This paper addresses the aerodynamic design of a radial flow wave-rotor for a microscale gas turbine engine. A, wave-rotor topping gas turbine cycle was described. The wave diagram was used for expressing behaviors of shock and expansion waves in the wave-rotor cells. Finally, geometrical configuration of the wave-rotor was described on the basis of aerodynamic design.

Low speed aerodynamic performance analysis of vortex lift waveriders with a wide-speed range

The wide-speed range characteristics of aerodynamic configuration for aircraft are critical to the design of the hypersonic vehicle, and many novel strategies have been proposed. As one of the valid schemes of aircraft with a wide-speed range, the vortex lift waverider with a wide-speed range has attracted an increasing attention. In the current study, the low speed aerodynamic performance of vortex lift waveriders with a wide-speed range has been investigated numerically by means of the three-dimensional implicit Reynolds-averaged Navier-Stokes (RANS) equations coupled with the SST k-ω turbulence model. At the same time, the numerical approaches employed have been validated against the available experimental data in the open literature. The obtained results show that the low speed lift-to-drag ratio of the cuspidal waverider is higher than that of the general osculating cone waverider, while the low speed lift-to-drag ratio of the delta-winged waverider is lower than that of the general osculating cone waverider except for the small and negative angles of attack. At the same time, the low speed vortex lift characteristics of the three types of osculating cone waveriders have been compares and analyzes, and some valuable conclusions have been obtained.

CFD analysis of variable wall thickness scroll expander integrated into small scale ORC systems

Abstract The studies of constant wall thickness scroll expander have pointed out that geometries with large built-in volume ratios are necessary to achieve high performances in small-sized organic Rankine cycle (ORC) units. The variable wall thickness expander design offers the opportunity of increasing the geometric expansion ratio with the number of scroll turns remaining unchanged to avoid sealing and lubricating issues. In this paper, unsteady and three-dimensional computational fluid dynamics (CFD) simulations of scroll expander using variable wall thicknesses were therefore carried out to investigate the effects of the geometry on the internal flow behaviour. The scroll expander was integrated into an ORC unit fed by R123. The dynamic mesh technology of ANSYS Fluent was applied to generate the deforming mesh in the expander working chambers. The aerodynamic performance analysis yielded how over-expansion phenomena occurred at low pressure ratio while under-expansion phenomena were existing at high pressure ratio which are consistent with the thermodynamic theory of scroll expander. The higher pressure ratio was also contributing to higher temperature drops during the expansion process. Moreover, the occurrence of flank leakages through the radial clearances and its effects on the flow field were pointed out further proving the thermodynamic theory of scroll expander.

A comparative CFD analysis of NACA0012 and NACA4412 airfoils

Wind energy has been seen as one of the most suitable sources of renewable energy. Wind energy is low cost when compared the other sources. Therefore, wind energy can gain an edge over the fossil-fired power plants. Aerodynamic efficiency of the airfoil is very crucial for aerodynamic efficiency of the wind turbine. The primary purpose of our study was to analyze the NACA0012 and NACA4412 airfoil at various attack angles with constant Reynolds number and to examine the effects of the symmetrical and asymmetrical profiles of the airfoil. Analysis of aerodynamic performance of NACA0012 and NACA4412 airfoil were performed with using ANSYS Fluent program. Also, lift coefficients and drag coefficients were calculated at various attack angles. According to calculations, optimum attack angles were found for each profile. Finally, NACA0012 and NACA4412 airfoils were discussed and reported in terms of their airfoil performances.

Detailed Design and Aerodynamic Performance Analysis of a Radial-Inflow Turbine

Radial-inflow turbines (RI turbines) are critical components of air cycle machines (ACM), utilized in environment conditioning systems (ECS). In this work, a process is presented for the full design of a radial-inflow turbine, including volute, nozzle blade row and rotor blade row. The preliminary and detailed aerodynamic design approaches are explained in detail. A mean-line (1D) analysis method coupled with the preliminary design is employed to evaluate the aerodynamic performance of the RI turbine. Then, ANSYS CFX is used to perform unsteady 3D simulations of the designed RI turbine at design and off-design conditions to predict the aerodynamic performance of the turbine for future optimization.

Design and high speed aerodynamic performance analysis of vortex lift waverider with a wide-speed range

According to the geometrical relationships of osculating cone waveriders, two kinds of design methods for the constant swept waverider are discussed in the current study, and both of them own more flexible design curves. The correctness and effectiveness of the proposed approaches has been verified by means of the CFD approach. The design Mach numbers of the cuspidal waverider and the general osculating cone waverider with the same volumetric efficiency of the delta-winged waverider have been determined by writing a program for calculating the volumetric efficiencies of waveriders. Furthermore, the high speed aerodynamic performance advantages of the cuspidal and delta-winged waveriders have been analyzed in detail, in comparison with the high speed aerodynamic performance of the general osculating cone waverider. The obtained results show that compared with the general osculating cone waverider, the cuspidal waverider has better high speed aerodynamic performance under any flight condition in the high speed range, while the high speed aerodynamic performance of the delta-winged waverider is worse. In addition, at the high flight Mach number, the cuspidal waverider shows the significant non-linear behavior of the vortex generated lift, while the delta-winged waverider and the general osculating cone waverider do not have this property.

Aerodynamic performance and flow characteristics analysis of Tesla turbines with different nozzle and outlet geometries

The aerodynamic performance and flow characteristics of a multichannel nozzled Tesla turbine were investigated numerically with different nozzle and outlet geometries at different rotational speeds. Two kinds of nozzle geometries were proposed: one nozzle channel to one disc channel (named as one-to-one turbine) and one nozzle channel to several disc channels (named as one-to-many turbine). Simplified radial outlet and real axial outlet geometries of the Tesla turbines were adopted to research the influence of outlet geometries. The results show that compared with the one-to-many turbine, the isentropic efficiency of the one-to-one turbine is much higher; while the flow coefficient is much lower. In addition, in the middle disc channels (DC1 and DC2) of which two walls are rotating disc walls, the flow fields are almost the same, but different from that in the side channel (DC3) of which one wall is a rotating wall and the other one is a stationary casing wall. DC1 and DC2 generate more torque with less working fluid, thus the disc spacing distance of DC3 should be narrower than that of DC1 and DC2. Compared to the one-to-many turbine, the working fluid flowing through DC1 and DC2 of the one-to-one turbine is much less, and the flow path lines are much longer. The results of different turbine outlet geometries show that compared with the turbines with radial outlet, the isentropic efficiency of the one-to-many turbine with axial outlet is a little higher, while that of the one-to-one turbine with axial outlet is lower. This is due to the larger torque on the disc hole walls, despite a lot more total pressure loss in the exhaust vent of the one-to-many turbine. Therefore, the contribution of disc hole walls to torque cannot be neglected in numerical simulations.