Good Aerodynamic Performance Research Articles

Fast prediction of the flutter critical wind speed of streamlined box girders by using aerostatic force coefficients and artificial neural networks

In the preliminary design stage of long-span bridges, there are many bridge deck schemes that need to check flutter stability through wind tunnel tests, and therefore it will take a lot of time and money. So, the authors are committed to investigating a way to quickly predict the flutter critical wind speed (FCWS) of bridge decks, and then select the schemes with better aerodynamic performance for further wind tunnel tests. Firstly, taking the streamlined box girder as the research object, the relationship between aerostatic force coefficients and flutter stability was derived, which proves that aerostatic force coefficients can be used to estimate the flutter stability of streamlined box girders. Secondly, through wind tunnel tests, a sample database with 315 sets of test data was obtained to establish the artificial neural networks (ANNs). Finally, by combining the ANNs and the CFD software, a procedure for quickly evaluating the flutter stability of streamlined box girders was proposed. Moreover, taking one long-span bridge as an example, the proposed procedure was used to predict the FCWS of each scheme and select the schemes with good aerodynamic performance. To check the prediction accuracy, the wind tunnel tests corresponding to the bridge deck schemes were performed. By comparing the prediction and test results, it is found that: 1) the proposed procedure can reasonably select the streamlined box girder schemes with good aerodynamic performance for further wind tunnel tests, thus avoiding unnecessary tests and improving work efficiency; 2) by combining with ANNs, aerostatic force coefficients can be used to evaluate the aerodynamic performance of streamlined box girders.

A gradient-descent-based method for design of performance-scaled rotor for floating wind turbine model testing in wave basins

When performing the model testing of floating wind turbine (FWT) in wave basins, using geometric-scaled rotors is unable to achieve the desired thrusts due to the dramatic reduction of Reynolds number experienced by model-scaled blades. Alternatively, a performance-scaled rotor (PSR) is usually utilized. In the present study, a gradient-descent-based method, named as CCB-GD method is proposed to conduct the PSR design for FWT model testing in wave basins. Different from existing methods, the proposed method aims to mimic the radial distribution of normal aerodynamic loads along the blade, rather than the total thrust. This is achieved by combining the blade element momentum theory with gradient descent optimization algorithm. In the present design procedure, a new airfoil with good aerodynamic performance at low Reynolds number is first selected, the optimal radial distribution of twist angles and chord lengths are then determined separately and sequentially based on the gradient-descent optimization algorithm. Additionally, high-order Bezier curves are used to smooth the radial distribution of twist angle and chord length. The proposed method is demonstrated by two case studies, in which the PSR design of the NREL 5 MW wind turbine and the DTU 10 MW wind turbine are conducted and compared with existing methods. Results show that the present method can design the PSR with good accuracy. Besides, the present method is robust, generic and also applicable in the PSR design of MW-scale wind turbines for FWT model testing in the wave basin.

Design and validation of a two-dimensional variable geometry inlet

Abstract The design of a two-dimensional variable geometry inlet which applied to a tandem type turbine-based combined cycle (TBCC) propulsion system was investigated in the present paper through three-dimensional simulations and wind tunnel tests. The operation Mach number range was between 0 and 3. A multi-ramp geometry scheme was adopted to achieve acceptable performance at different inflow Mach number. The first ramp angle was fixed whilst the angles of the second and the third ramps were variable at different inflow Mach numbers. The Mach numbers at throat region were maintained between 1.3 and 1.5 at different inflow Mach numbers according to this variable geometry scheme. A fixed geometry rectangular-to-circular shape diffuser was adopted to improve aerodynamic performance of the inlet. Three-dimensional numerical simulations were carried out between Ma1.5 and Ma3.0. The results indicated that good aerodynamic performance can be achieved at different inflow speed. At the design point, total pressure recovery of the inlet was 0.66 at critical condition. Wind tunnel validation experiment tests were conducted at Ma2.0, showing the movement of terminal shock wave from downstream to upstream as the back pressure increased. The inlet operated at supercritical, critical and subsonic conditions at different back pressure.

Effects of countersunk hole geometry errors on the fatigue performance of CFRP bolted joints

Due to good aerodynamic performance and reliability, countersunk bolt joint is one of the most commonly used connection methods for carbon fiber reinforced polymer (CFRP) components in the aircraft. However, the countersunk hole machining process is inevitably accompanied by geometric errors, which will directly affect the mechanical properties of the joint structure. This paper presents a numerical and experimental investigation on the effect of countersunk hole geometry errors on the fatigue performance of CFRP bolted joints. FE model of CFRP countersunk bolted joints with designed geometry errors are established, and the rationality of the FE analysis was verified by fatigue life and failure forms. The CFRP bolted structure failure mechanism under fatigue load and influence of hole-making geometry error (including countersunk fillets radius, countersunk depth, and countersunk angle) on the fatigue life are investigated. Based on the relationship between fatigue life and the geometry error, the corresponding tolerances for CFRP bolt joint countersunk hole are determined as well. The research results can provide a reference for establishing reasonable geometric accuracy requirements for CFRP joint hole machining.

The combination of an innovative dry powder for inhalation and a standard cisplatin-based chemotherapy in view of therapeutic intensification against lung tumours

Cisplatin is one of the most commonly used chemotherapy in lung cancer despite its high nephrotoxicity leading to an administration only every 3–4 weeks. This study is the first report of a preclinical investigation of therapeutic intensification combining a cisplatin dry powder for inhalation (CIS-DPI) with an intravenous (iv) cisplatin-based treatment. CIS-DPI with 50% cisplatin content (CIS-DPI-50) was developed using lipid excipients through scalable processes (high-speed and high-pressure homogenization and spray-drying). CIS-DPI-50 showed good aerodynamic performance (fine particle fraction of ~ 55% and a mass median aerodynamic particle size of ~ 2 µm) and a seven-fold increase and decrease in Cmax in the lungs and in plasma, respectively, in comparison with an iv cisplatin solution (CIS-iv) in healthy mice. Finally, the addition of CIS-DPI-50 to the standard cisplatin/paclitaxel iv doublet increased the response rate (67% vs 50%), decreased the tumour growth and prolonged the median survival (31 vs 21 days), compared to the iv doublet in the M109 lung carcinoma model tending to demonstrate a therapeutic intensification of cisplatin.

Numerical Study on Aerodynamic Performance of Different Forms of Adaptive Blades for Vertical Axis Wind Turbines

The wind energy exploitation technique has been developed very quickly in recent years. The vertical axis wind turbine is a hot research domain due to several advantages: low noise, flexible for installation, ease of maintenance, great safety and credibility, etc. The aerodynamic performances of different forms of airfoils including an active deformation airfoil and a fluid-solid coupling passive airfoil with two-dimensional (2D) and three-dimensional (3D) cases have been investigated numerically in this paper. Firstly, the aerodynamic performances of the airfoils with the maximum deformation amplitudes of their cambers which are 3%, 5% and 7% of the chord length have been discussed, respectively, with the angles of attack in the range of 0° and 20°. Secondly, for the angle of attack set at 18°, the two-way fluid-solid coupling simulations with the Young’s Modulus of 1 Mpa and 2 Mpa have also been investigated. Results show that: (1) for the pseudo 3D and real 3D single active deformation airfoil cases, the lift coefficients increase as the maximum deformation amplitudes augment from 3% to 7% of the chord length at the same angle of attack. With the same maximum deformation amplitude, when the angles of attack increase from 0° to 20°, the lift coefficients which increase firstly and then decrease are bigger than that of the original NACA0012 airfoil. When the maximum deformation amplitude of the pseudo 3D airfoil reaches 5% of the chord length, a relatively good aerodynamic performance with better inhibition effect of vortex generation can be obtained. The 3D vortex distribution demonstrates that the deformable airfoil has a better vortex generation controlling effect at the middle cross-section along the spanwise direction than the non-deformable airfoil. (2) From the aspect of fluid-solid coupling, the lift increases and the drag decreases so that the lift to drag ratio has a big improvement when the Young’s Modulus is equal to 1 Mpa and 2 Mpa. The deformable airfoil can inhibit the generation and the shedding of the surface vortex when the fluid-solid coupling effect is considered.

Inter-Disciplinary Approach to Suborbital Reusable Spaceplane Composite Wing Design

The development of the wing of suborbital reusable spaceplane is a complex task due to conflicting requirements that are sufficient for its structure. They include high mass and cost efficiency, sustainability, low g-forces, effective heat protection under the consideration of technological restraints. To satisfy outlined requirements in the design of the composite wing the inter-disciplinary approach is presented relying on advanced methods of mathematical modelling. The approach starts with wing shape optimization enabling to get good aerodynamic performance. Subsequent optimal re-entry trajectory planning which use both angle-of-attack and angle-of-bank changes to control the re-entry provides a set level of g-forces and heat flux. Then based on the obtained trajectory the aerodynamic loads for the wing are gained. To acquire composite materials properties of the wing the analysis/test approach is applied that comprises multilevel modelling of mechanical and thermal material properties by commercial software. The results of modelling are validated by experiment. In addition, to enhancing mass efficiency of the wing structure the topology optimization of its wing box and structural optimization of the wing skin is conducted which uses both angles of orientations and thicknesses of composite monolayers as the variables with constraints on the strength and stiffness of wing skin. Furthermore, the approach includes thermal design due to high aerodynamic heating taking place during re-entry. Thermal loads are analysed by modelling the thermal state of the structure. The analysis showed that the wing skin needs thermal protection. As the thermal protection coating, the material based on glass microspheres was chosen. Its thickness through wing is obtained in the result of parameter optimization. As the result, the interdisciplinary approach to the design of the spaceplane composite wing is developed that allows feeding back mass, economic, aerodynamic, heat and strength impact into the spaceplane wing design synthesis.

Numerical Investigation of the Effect of Changing the Thickness of Airfoils used in Wind Turbines on the Lift to Drag Ratio

In this paper, the effect of changing the thickness of the airfoils on the lift and drag coefficients and lift to drag ratio for three types of airfoils is presented. The study was done by making a 2D simulation by using the commercial software ANSYS FLUENT 2019R1. The airfoils that were selected for the simulation were the NREL S830, SG6043, and SD7062. In order to study the effect of changing the thickness of airfoils on the aerodynamic characteristics, the thickness of NREL S830, SG6043, and SD7062 airfoils was increased and decreased by 20%. The method used to increase and decrease the thickness was done by modifying the coordinates of the upper and lower curves of the baseline airfoils in the y-direction. The simulation was done using the Spalart Allmaras turbulence model for low wind speed (5m/s) and a wide range of attack angles (from 0 to 15 degrees). The aerodynamic characteristics, which are the lift and drag coefficients, lift to drag ratio, and the optimum angle of attack, are presented in this study. It was concluded that reducing the thickness to 20% leads to a remarkable increase in the lift to drag ratio while increasing the thickness leads to a decrease in the lift to drag ratio. It was also concluded that reducing thickness will not always lead to maximizing the lift coefficient but will always reduce the drag coefficient. It was also found that for wind turbines operating in low wind speed regions, the SG6043 airfoil profile is the most suitable as it showed a good aerodynamic performance at low wind speed.

Low-speed wind turbine design based on Wilson theory

As a clean and renewable energy with huge reserves, wind energy has been widely developed and utilized worldwide. Wind turbine blades are one of the main components of wind power generation. The degree of conversion of wind energy by the blades can determine the efficiency of the wind turbine. This paper aims to optimize the design of low-speed wind turbine blades with a rated power of 600 kW and an average wind speed of 4.3 m/s at the hub height. Wind turbines use variable speed and pitch control to determine the design parameters of the wind turbine. We choose an airfoil with good aerodynamic performance at low wind speeds. The Wilson design method is used to calculate the chord length, torsion angle and other parameters of each segment of the blade, complete the preliminary shape design of the low-speed blade, and calculate its aerodynamic performance.

Aerodynamic effects of leading edge (LE) slats and slotted trailing edge (TE) flaps on NACA-2412 airfoil in prospect of optimization

Currently, various high lift devices are being employed in the general aviation industry. The performance of these high lift devices depends on various parameters, among which the geometrical or positional parameters are one of the most important as their influence is very prominent on the aerodynamics of the wing. Hence, attention is to be given to the optimization of these devices to increase their efficiency and performance. This article focuses on the optimization of high lift devices such as leading edge slats and trailing edge flaps. The optimization is achieved with four defined configurations for each high lift device and then compared their results with each other to find the best configuration; here the best performance refers to maximization of section coefficient of lift. A two-dimensional CFD (computational Fluid Dynamics) analysis performed on best three element airfoil using SolidWorks Flow Simulation tool with variation in aerodynamic parameters as lift and pitching moment. The obtained results have an accuracy of 1.09% for maximum coefficient of lift and 0.4% for landing condition respectively. Thus the optimized NACA2412 three-element airfoil gives good aerodynamic performance.

Algorithm for Accumulating Part Mating Gaps to Evaluate Solid and Fluid Performances

Abstract Part mating gaps need to be effectively adjusted during the assembly of products and greatly affect the working performance. This paper develops an algorithm to calculate the dimensional and aerodynamic indexes affected by part mating gaps. Mating gaps are expressed by displacements of one contact surface, and indexes are evaluated by displacements of key surface, when the surface is ready to compare with the other. A graph that denotes contacts as nodes and related paths through the physical domain as lines is proposed to express assembly sequences and hierarchies. A variable is defined to combine the time set with the displacement set. Boolean algebraic theorems are extended to derive a compact expression for the contact graph that supports the organization of accumulations at different surfaces with propagations through physical domains. Demonstrations of this method using three products exhibit the general applicability, and the application shows that the performance deviations of the centrifugal fan and axial turbine are apparent. In particular, the isentropic efficiency is good with a certain probability, despite turbines having mating gaps. The algorithm benefits both design and assembly: design can be performed through the fluid domain, which is affected by the mating gaps, and when the parts are being adjusted, the selected tolerance limit allows engineers to monitor key surfaces to ensure good aerodynamic performance.

Route to chaos on a dragonfly wing cross section in gliding flight

The route from linear towards nonlinear and chaotic aerodynamic regimes of a fixed dragonfly wing cross section in gliding flight is investigated numerically using direct Navier-Stokes simulations (DNSs). The dragonfly wing consists of two corrugations combined with a rear arc, which is known to provide overall good aerodynamic mean performance at low Reynolds numbers. First, the three regimes (linear, nonlinear, and chaotic) are characterized, and validated using two different fluid solvers. In particular, a peculiar transition to chaos when changing the angle of attack is observed for both solvers: The system undergoes a sudden transition to chaos in less than 0.1^{∘}. Second, a physical insight is given on the flow interaction between the corrugations and the rear arc, which is shown as the key phenomenon controlling the unsteady vortex dynamics and the sudden transition to chaos. Additionally, aerodynamic performances in the three regimes are given, showing that optimal performances are closely connected to the transition to chaos.

A study of morphing aircraft on morphing rules along trajectory

Morphing aircraft can meet requirements of multi-mission during the whole flight due to changing the aerodynamic shape, so it is necessary to study its morphing rules along the trajectory. However, trajectory planning considering morphing variables requires a huge number of expensive CFD computations due to the morphing in view of aerodynamic performance. Under the given missions and trajectory, to alleviate computational cost and improve trajectory-planning efficiency for morphing aircraft, an offline optimization method is proposed based on Multi-Fidelity Kriging (MFK) modeling. The angle of attack, Mach number, sweep angle and axial position of the morphing wing are defined as variables for generating training data for building the MFK models, in which many inviscid aerodynamic solutions are used as low-fidelity data, while the less high-fidelity data are obtained by solving viscous flow. Then the built MFK models of the lift, drag and pressure centre at the different angles of attack and Mach numbers are used to predict the aerodynamic performance of the morphing aircraft, which keeps the optimal sweep angle and axial position of the wing during trajectory planning. Hence, the morphing rules can be correspondingly acquired along the trajectory, as well as keep the aircraft with the best aerodynamic performance during the whole task. The trajectory planning of a morphing aircraft was performed with the optimal aerodynamic performance based on the MFK models, built by only using 240 low-fidelity data and 110 high-fidelity data. The results indicate that a complex trajectory can take advantage of morphing rules in keeping good aerodynamic performance, and the proposed method is more efficient than trajectory optimization by reducing 86% of the computing time.

Numerical study on the flow field characteristics of the new high-speed maglev train in open air

With the increasing demand of higher travelling speed, a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h. To better capture the flow field structures around the maglev train, an improved delayed detached eddy simulation (IDDES) is adopted to model the turbulence. Results show that the new maglev train has good aerodynamic load performance such as small drag coefficient contributing to energy conservation. The main frequencies of aerodynamic forces for each car have a scattered distribution. There are two pairs of counter-rotating large vortices in the non-streamlined part of the train that make the boundary layer thicker. Many high-intensity vortices are distributed in the narrow space between skirt plates or train floor and track. In the gap between the train floor and track (except near the tail car nose), the main frequency of vortex shedding remains constant and its strength increases exponentially in the streamwise direction. In the wake, the counter-rotating vortices gradually expand and reproduce some small vortices that move downward. The vortex has quite random and complex frequencydomain distribution characteristics in the wake. The maximum time-averaged velocity of the slipstream occurs near the nose of the head car, based on which, the track-side safety domain is divided.

A comprehensive investigation on the design and off-design performance of supercritical carbon dioxide power system based on the small-scale lead-cooled fast reactor

Nuclear energy is a kind of stable, controllable and cleaner energy without massive discharge of pollutant. A comprehensive investigation on the design and off-design performance of supercritical carbon dioxide power system is conducted for the small-scale lead-cooled fast reactor in this paper. A suitable design operating condition is determined based on the system thermodynamic model and exergoeconomic model in the design stage. The off-design condition models of turbine, compressor and heat exchangers are established. Five kinds of off-design control strategies and their relationship with cleaner production and sustainable development are studied under different grid loads conditions. Results show that the system thermal efficiency can reach upto 32.18% with the optimal total product unit cost of 21.33$⋅GJ−1 in the design stage. A designed centrifugal compressor based on the demonstrated Two-zone model displays good aerodynamic performance and a wide off-design operating range. The off-design performance analysis exhibits that all control strategies can complete the adjustment of power output over a range of 10%–100%. Inventory control is the best control strategy. Cleaner production coefficient decreases with the grid load for all control strategies, and this research can provide references for cleaner production and promote the sustainable development of society effectively.

Experimental studies on the aerodynamic performance of two box girders with side openings

A butterfly web girder is a box-shaped girder with discretely distributed side openings along the spanwise direction. Until now, there have been few studies related to the aerodynamic performance of the butterfly web bridge. The objective of the current study was to clarify the effects of the side openings on the aerodynamic performance of the girder. Two butterfly web girders with side ratios B/D = 3.24 and 5, where B is the girder width and D is the depth, were examined through a series of wind tunnel tests. A comparison of the results for butterfly web girders and conventional box girders of the same shape confirmed that the side openings stabilized the vortex-induced vibration and galloping when B/D = 3.24, whereas the vortex-induced vibration and torsional flutter were stabilized when B/D = 5. The change in the flow field due to the side openings contributed to the stabilization against the vibration. These findings not only confirmed the good aerodynamic performance of the butterfly web bridge but also provided a new method to stabilize the box girder against aerodynamic instabilities via discretely distributed side openings.

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 of a Radial Turbine for Wastegated Turbocharger

With the increasing popularity of turbocharging technology in the automotive industry, and people's increasing awareness of environmental protection, engineers are paying more attention to the technical development of turbochargers, while more advanced tools and methods are being used in the actual turbocharged design process to improve the accuracy and efficiency of research and design. Traditional turbocharger design methods are often based on experimental data and empirical models, and long development cycles conflict with market demand, and high performance conflict with high reliability. In this paper, in order to resolve this significant contradiction, a design process based on a variety of CAE methods and tools is proposed for the design of turbines, which are key components of turbochargers. This process was early applied to the design of turbocharger compressor, and then under the original boundary conditions, considering the challenges of high temperature and high engine demand, it has been improved and applied to the design of a 9L off-road country Tier-IV engine turbine in the Chinese market. The analysis shows that the turbine has good aerodynamic performance and structural reliability. The turbine performance was tested in gas stand the also verified on the engine test. This study demonstrated that the design was successful and future new turbine design can use similar procedure.

Aerodynamic Performance of a New Double-Flap Wing Sail

Abstract As a type of natural energy resource, wind power is used in the modern implementation of wind-assisted technologies as a method for reducing the fuel consumption and environmental pollution of ocean-going ships. In order to promote the full usage of ocean wind energy for cargo ships, an innovative type of ship propulsion-assisted wing sail is proposed in this paper. The propulsion efficiency of this new wing sail can be increased by enlarging its area in both the transverse and vertical directions in good weather conditions, and it can be folded up automatically in poor weather conditions, improving the sailing safety of the ship. The sail parameters relating to the gaps and rotation angles between different parts of the wing sail are compared, and the values giving the best aerodynamic performance are identified using CFD simulation technology. The results for the lift and drag coefficients for the new wing sail at different attack angles are also compared with those of traditional aerofoil sails, including an arc-shaped rigid sail and a variable-camber sail proposed in 2015. From the viewpoint of the sailing performance of the vessel, our results demonstrate that this new type of wing sail has good aerodynamic performance and can reduce fuel costs for commercial vessels.

Lift, drag and pitching moment performances of different wing profiles for MAV wings

The wing profile for Micro Air Vehicle (MAV) can be easily developed through the polynomial equation method which is proven in generating good aerodynamic performances. However, the study demands more studies in profile configurations to provide more evidence which interrelated with its aerodynamic performances. Thus, in this works, an aerodynamic study on different wing profiles configurations has been carried out. Profile 1, Profile 2 and Profile 3 were developed through the 3rd order polynomial equations have analyzed based on simulation works by using ANSYS-CFX. Based on the lift distribution analysis, it shows that Profile 3 has a huge advantage in generating better lift distribution (CL) among the wing profiles. Profile 3 able to produce at least 20% to 22.9% better maximum lift coefficient (CLmax) and CL magnitude compared to the other wing profiles. Despite its benevolent in CL performances, Profile 3 has induced the highest drag (CD) penalty among the wing profiles. Profile 3 has consistently produced at least 57.5% higher CD magnitude compared to other wing profiles. However, in terms of moment coefficient (CM) performances, Profile 3 has shown a promising ability in providing better wing stability compared to the other wing profile due to steeper CM slope.