Journal articles on the topic 'Global aerodynamic coefficients'
To see the other types of publications on this topic, follow the link: Global aerodynamic coefficients.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Global aerodynamic coefficients.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Albisser, Marie, and Simona Dobre. "Sensitivity Analysis for Global Parameter Identification. Application to Aerodynamic Coefficients." IFAC-PapersOnLine 51, no. 15 (2018): 963–68. http://dx.doi.org/10.1016/j.ifacol.2018.09.069.
2
Laupré, Gabriel, and Jan Skaloud. "On the Self-Calibration of Aerodynamic Coefficients in Vehicle Dynamic Model-Based Navigation." Drones 4, no. 3 (July 12, 2020): 32. http://dx.doi.org/10.3390/drones4030032.
Abstract:
The performance of vehicle dynamic model (VDM)-based navigation largely depends on the accurate determination of aerodynamic coefficients that are unknown a priori. Among different techniques, such as model simulations or experimental analysis in a wind tunnel, the method of self-calibration via state-space augmentation benefiting Global Navigation Satellite System (GNSS) positioning represents an interesting and economical alternative. We study this technique under simulation with the goal of determining the impact of aircraft maneuvers on the precision and (de)-correlation of the aerodynamic coefficients among themselves and with respect to other error-states. A combination of different maneuvers indicates to be essential for obtaining satisfactory aerodynamic coefficients estimation and reduce their uncertainty.
3
Svorcan, Jelena, Ognjen Pekovic, and Toni Ivanov. "Estimation of wind turbine blade aerodynamic performances computed using different numerical approaches." Theoretical and Applied Mechanics 45, no. 1 (2018): 53–65. http://dx.doi.org/10.2298/tam171130004s.
Abstract:
Although much employed, wind energy systems still present an open, contemporary topic of many research studies. Special attention is given to precise aerodynamic modeling performed in the beginning since overall wind turbine performances directly depend on blade aerodynamic performances. Several models different in complexity and computational requirements are still widely used. Most common numerical approaches include: i) momentum balance models, ii) potential flow methods and iii) full computational fluid dynamics solutions. Short explanations, reviews and comparison of the existing computational concepts are presented in the paper. Simpler models are described and implemented while numerous numerical investigations of isolated horizontal-axis wind turbine rotor consisting of three blades have also been performed in ANSYS FLUENT 16.2. Flow field is modeled by Reynolds Averaged Navier-Stokes (RANS) equations closed by two different turbulence models. Results including global parameters such as thrust and power coefficients as well as local distributions along the blade obtained by different models are compared to available experimental data. Presented results include fluid flow visualizations in the form of velocity contours, sectional pressure distributions and values of power and thrust force coefficients for a range of operational regimes. Although obtained numerical results vary in accuracy, all presented numerical settings seem to slightly under- or over-estimate the global wind turbine parameters (power and thrust force coefficients). Turbulence can greatly affect the wind turbine aerodynamics and should be modeled with care.
4
Michálek, Petr, and Stanislav Hračov. "Experimental investigation of aerodynamic coefficients of the Holy Trinity Column in wind tunnel." MATEC Web of Conferences 313 (2020): 00049. http://dx.doi.org/10.1051/matecconf/202031300049.
Abstract:
The analysis of the aerodynamic force coefficients of the Holy Trinity Column in Olomouc based on the experimental wind tunnel testing is presented. Two aerodynamic models corresponding to geometrical scales 1:75 and 1:150 were built using 3D-printer and tested in the smooth flow in order to define the global static wind effects. The larger model served as a reference case for the tests of the isolated column, while the model build with smaller scale enabled also the experimental examination of the influence of the closest surroundings. The comparison of the aerodynamic coefficients obtained from the testing of both models for various wind speeds confirms their similarity and interchangeability. The independence of the coefficients on Reynolds number, Re, were successfully verified and the presented coefficients were determined for Re = 2.7 105 for a large number of angles of wind attack. The significant decrease in the static wind load due to the surrounding buildings were observed. The obtained results can broaden the knowledge of wind load related to this type historical monuments and can be useful when deciding about their global maintenance, a type of remedial work or their conservation.
5
Buzica, Andrei, Lisa Debschütz, Florian Knoth, and Christian Breitsamter. "Leading-Edge Roughness Affecting Diamond-Wing Aerodynamic Characteristics." Aerospace 5, no. 3 (September 19, 2018): 98. http://dx.doi.org/10.3390/aerospace5030098.
Abstract:
Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the AVT-183 diamond wing configuration with variation of leading-edge roughness size and Reynolds number. Wind tunnel testing applying force and surface pressure measurements are conducted and the results presented and analysed. For the investigated Reynolds number range of 2.1 × 10 6 ≤ R e ≤ 2.7 × 10 6 there is no significant influence on the aerodynamic coefficients. However, leading-edge roughness height influences the vortex separation location. Trip dots produced the most downstream located vortex separation onset. Increasing the roughness size shifts the separation onset upstream. Prior to stall, global aerodynamic coefficients are little influenced by leading-edge roughness. In contrast, maximum lift and maximum angle of attack is reduced with increasing disturbance height. Surface pressure fluctuations show dominant broadband frequency peaks, distinctive for moderate sweep vortex breakdown. The experimental work presented here provides insights into the aerodynamic characteristics of diamond wings in a wide parameter space including a relevant angle of attack range up to post-stall.
6
Zhu, Hongyu, Gang Wang, Yi Liu, and Boping Ma. "Uncertainty Analysis of Supersonic Biplane's Aerodynamic Characteristics." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 37, no. 5 (October 2019): 909–17. http://dx.doi.org/10.1051/jnwpu/20193750909.
Abstract:
Utilizing the interference of shock and expansion waves, supersonic biplane can reduce the wave drag remarkably. However, the supersonic biplane is only designed at special conditions, so that it has poor performance at off-design conditions. To analyze supersonic biplane's aerodynamic characteristics at off-design conditions, the non-instructive probabilistic collocation method has been employed to achieve uncertainty quantification. Besides, Sobol global sensitivity is adopted to accurately evaluate the influence of the input uncertainty parameters. The uncertainty parameters are Mach number and the angle of attack which both satisfy special normal distributions. Aerodynamic coefficients and pressure distribution from the biplane's surface as well as flow filed are studied. The results of uncertainty quantification show that the main reason for aerodynamic characteristics fluctuations is the pressure pulsation from the maximum thickness of the lower airfoil's upper surface. The results of global sensitivity show that Mach number is the most important factor for the variation of aerodynamic performance.
7
Wiński, Krzysztof, and Adam Piechna. "Comprehensive CFD Aerodynamic Simulation of a Sport Motorcycle." Energies 15, no. 16 (August 15, 2022): 5920. http://dx.doi.org/10.3390/en15165920.
Abstract:
Nowadays, aerodynamics is a key focal point in the vehicle design process. Beyond its direct impact on the performance of a vehicle, it also has significant effects on economics and safety. In the last decade numerical methods, mainly Computational Fluid Dynamics (CFD), have established themselves as a reliable tool that assists in the design process and complements classical tunnel tests. However, questions remain about the possible obtained accuracy, best practices and applied turbulence models. In this paper, we present a comprehensive study of motorcycle aerodynamics using CFD methods which, compared to the most common car aerodynamics analysis, has many specific features. The motorcycle, along with its rider, constitutes a shape with very complex aerodynamic properties. A detailed insight into the flow features is presented with detailed commentary. The front fairing, the front wheel and its suspension were identified as the main contributors to the aerodynamic drag of the motorcycle and its rider. The influence of rider position was also studied and identified as one of the most important elements when considering motorcycle aerodynamics. An extensive turbulence models study was performed to evaluate the accuracy of the most common Reynolds-averaged Navier–Stokes models and novel hybrid models, such as the Scale Adaptive Simulation and the Delayed Detached Eddy Simulation. Similar values of drag coefficients were obtained for different turbulence models with noticeable differences found for k−ϵ models. It was also observed that near-wall treatment affects the flow behaviour near the wheels and windshield but has no impact on the global aerodynamic parameters. In the summary, a discussion about the obtained results was set forth and a number of questions related to specifics of motorcycle CFD simulations were addressed.
8
Zalewski, Wiesław. "The Impact of Propeller on Aerodynamics of Aircraft / Wpływ Śmigła Na Aerodynamikę Samolotu." Journal of KONBiN 33, no. 1 (September 1, 2015): 209–22. http://dx.doi.org/10.1515/jok-2015-0018.
Abstract:
Abstract The paper presents a numerical analysis of the impact of working propellers on the aerodynamics of the aircraft. Analysis was made on the example of a twin-engined, unmanned aircraft with electric drive during the low altitude flight. Three configurations were studied and compared: the plane without propellers, the plane with pusher propellers and the plane with tractor propellers. For each configuration distributions of aerodynamic coefficients along the span of the wing and their global values for the entire aircraft were estimated. Calculations were performed using the Fluent solver with implementation of a simplified model of propeller based on the Blade Element Theory. Results of the analysis indicate a slight advantage of the tractor propellers configuration.
9
Le-Duc, Thang, and Quoc-Hung Nguyen. "Aerodynamic Optimal Design for Horizontal Axis Wind Turbine Airfoil Using Integrated Optimization Method." International Journal of Computational Methods 16, no. 08 (August 29, 2019): 1841004. http://dx.doi.org/10.1142/s0219876218410049.
Abstract:
In this work, a new approach for aerodynamic optimization of horizontal axis wind turbine (HAWT) airfoil is presented. This technique combines commercial computational fluid dynamics (CFD) codes with differential evolution (DE), a reliable gradient-free global optimization method. During the optimization process, commercial CFD codes are used to evaluate aerodynamic characteristics of HAWT airfoil and an improved DE algorithm is utilized to find the optimal airfoil design. The objective of this research is to maximize the aerodynamic coefficients of HAWT airfoil at the design angle of attack (AOA) with specific ambient environment. The airfoil shape is modeled by control points which their coordinates are design variables. The reliability of CFD codes is validated by comparing the analytical results of a typical HAWT airfoil with its experimental data. Finally, the optimal design of wind turbine airfoil is evaluated about aerodynamic performance in comparison with existing airfoils and some discussions are performed.
10
Fontanella, Alessandro, Ilmas Bayati, Robert Mikkelsen, Marco Belloli, and Alberto Zasso. "UNAFLOW: a holistic wind tunnel experiment about the aerodynamic response of floating wind turbines under imposed surge motion." Wind Energy Science 6, no. 5 (September 9, 2021): 1169–90. http://dx.doi.org/10.5194/wes-6-1169-2021.
Abstract:
Abstract. Floating offshore wind turbines are subjected to large motions due to the additional degrees of freedom of the floating foundation. The turbine rotor often operates in highly dynamic inflow conditions, and this has a significant effect on the overall aerodynamic response and turbine wake. Experiments are needed to get a deeper understanding of unsteady aerodynamics and hence leverage this knowledge to develop better models and to produce data for the validation and calibration of existing numerical tools. In this context, this paper presents a wind tunnel experiment about the unsteady aerodynamics of a floating turbine subjected to surge motion. The experiment results cover blade forces, rotor-integral forces, and wake. The 2D sectional model tests were carried out to characterize the aerodynamic coefficients of a low-Reynolds-number airfoil with harmonic variation in the angle of attack. The lift coefficient shows a hysteresis cycle close to stall, which grows in strength and extends in the linear region for motion frequencies higher than those typical of surge motion. Knowledge about the airfoil aerodynamic response was utilized to define the wind and surge motion conditions of the full-turbine experiment. The global aerodynamic turbine response is evaluated from rotor-thrust force measurements, because thrust influences the along-wind response of the floating turbine. It is found that experimental data follow predictions of quasi-steady theory for reduced frequency up to 0.5 reasonably well. For higher surge motion frequencies, unsteady effects may be present. The turbine near wake was investigated by means of hot-wire measurements. The wake energy is increased at the surge frequency, and the increment is proportional to the maximum surge velocity. A spatial analysis shows the wake energy increment corresponds with the blade tip. Particle image velocimetry (PIV) was utilized to visualize the blade-tip vortex, and it is observed that the vortex travel speed is modified in the presence of surge motion.
11
Othman, Norazila, and Masahiro Kanazaki. "Development of Digital Flight Motion Methodology Based on Aerodynamic Derivatives Approximation." Journal of Robotics and Mechatronics 28, no. 2 (April 19, 2016): 215–25. http://dx.doi.org/10.20965/jrm.2016.p0215.
Abstract:
[abstFig src='/00280002/12.jpg' width=""300"" text='3D contour views of Cz [-0.4—1.05],Mach:0.6-1.4, Alpha:0°-30°' ]The accuracy of efficient flight simulation depends on the quality of the aerodynamic data used to simulate aircraft dynamic motion. The accuracy of such data prediction depends strongly on motion variables, aerodynamic derivatives, and the coefficients used when the complete global aerodynamic database is being building. A surrogate model applied as a prediction method based on several measured points (exact function) used to predict unknown points of interest helps reduce time taken by the experiment or computation. Latin hypercube sampling searches the solution space for aerodynamic data to optimize the experimental design, so the key objective is to develop an aircraft's efficient digital flight motion by solving equations of motion and predicting aerodynamic data using a surrogate model. To realize these goals, we use sample surrogate model data, acquired from empirical model USAF Stability and Control DATCOM. The database was built for two main variables, the angle of attack and the Mach number, along the longitudinal and lateral axes. Exact and predicted functions were compared by calculating the mean squared error (MSE). The digital flight was validated through mode motion analysis and a flight quality scale to prove flight mission capabilities. A comparison between results predicted by the surrogate model and the exact function showed that flight simulation analysis and prediction ability of the surrogate model are useful in future analyses.
12
Zhang, Ao, Yan Liu, Jinguang Yang, Zhi Li, Chuang Zhang, and Yiwen Li. "Machine learning based design optimization of centrifugal impellers." Journal of the Global Power and Propulsion Society 6 (July 25, 2022): 124–34. http://dx.doi.org/10.33737/jgpps/150663.
Abstract:
Big data and machine learning are developing rapidly, and their applications in the aerodynamic design of centrifugal impellers and other turbomachinery have attracted wide attention. In this paper, centrifugal impellers with large flow coefficient (0.18–0.22) are taken as research objects. Firstly, through one-dimensional design and optimization, main one-dimensional geometric parameters of those centrifugal impellers are obtained. Subsequently, hundreds of samples of centrifugal impellers are obtained by using an in-house parameterization program and Latin hypercube sampling method. The NUMECA software is used for CFD calculations to build a sample library of centrifugal impellers. Then, applying the artificial neural network (ANN) to deal with the data in the sample library, a nonlinear model between the flow coefficients, the geometric parameters of these centrifugal impellers and the aerodynamic performance is constructed, which can replace CFD calculations. Lastly with the help of the multi-objective genetic algorithm, a global optimization is carried out to fulfull a rapid design optimization for centrifugal impellers with flow coefficients in the range of 0.18–0.22. Three examples provided in the paper show that the design and optimization method described above is faster and more reliable compared with the traditional design method. This method provides a new way for the rapid design of centrifugal impellers.
13
Flora, Andrea, Pasquale Capasso, Simona Brancaccio, Paolo Ambrico, Alessio D’Onofrio, and Francesco De Stasio. "Effect of control surfaces on the aerodynamic database of the Stratofly hypersonic vehicle." MATEC Web of Conferences 304 (2019): 02021. http://dx.doi.org/10.1051/matecconf/201930402021.
Abstract:
This paper aims at studying the control surfaces of the STRATOFLY project reference aircraft, funded by the European Commission, under the framework of Horizon 2020 plan. The values of aerodynamic coefficients in a wide range of flow free-stream conditions are stored in the aircraft aerodynamic database. The research goal is to update a pre-existent database that was developed with fixed control surfaces using the six control surfaces deflection as input. Different Mach numbers determine different flow regimes: subsonic, transonic, supersonic, and hypersonic. In subsonic, transonic and low supersonic regimes a vortex-lattice solver is used to obtain the global coefficients assuming an unviscous flow on a simplified model. In hypersonic flow a build-up approach is applied: the control surfaces deflection contribution is developed by assuming a two-dimensional flow on the airfoil and by applying shock-expansion theory on the geometry. Then the paper analyses results showing stability and L/D results. The final paragraph focuses on trimmability at cruise Mach. No trimmed solution is obtainable to optimize the propulsive system. The solution proposed to solve this issue is to extend the four elevons: larger elevons are found to be able to trim the vehicle at the desired angle of attack.
14
DINA, Adrian, Sterian DANAILA, Mihai-Victor PRICOP, and Ionut BUNESCU. "Using genetic algorithms to optimize airfoils in incompressible regime." INCAS BULLETIN 11, no. 1 (March 5, 2019): 79–90. http://dx.doi.org/10.13111/2066-8201.2019.11.1.6.
Abstract:
Aerodynamic optimization is a very actual problem in aircraft design and airfoils are basic two-dimensional shape forming cross sections of wings. Traditionally, the airfoil geometry if defined by a very large number of coordinates. Nowadays, in order to simplify the optimization, the airfoil geometry is approximated by a parametrization, which enables to reduce the number of needed parameters to as few as possible, while effectively controlling the major aerodynamic features. The present work has been done on the Class-Shape function Transformation method (CST) [1, 2]. Also, the paper introduces the concept of Genetic Algorithm (GA) to optimize a NACA airfoil for specific conditions. A Matlab program has been developed to implement CS into the Global Optimization Toolkit. The pressure distribution lift and drag coefficients of the airfoil geometries have been calculated using two programs. The first one is an in-house code based on the Hess-Smith [3] panel technique and on the boundary layer integral equations, while the second is an XFOIL program. The optimized airfoil has improved aerodynamic characteristics as compared to the original one. The optimized airfoil is validated using the Ansys-Fluent commercial code.
15
Christopher, Sundar, and Pawan Gupta. "Global Distribution of Column Satellite Aerosol Optical Depth to Surface PM2.5 Relationships." Remote Sensing 12, no. 12 (June 20, 2020): 1985. http://dx.doi.org/10.3390/rs12121985.
Abstract:
Using a combined Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) mid-visible aerosol optical depth (AOD) product at 0.1 × 0.1-degree spatial resolution and collocated surface PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 μm) monitors, we provide a global five-year (2015–2019) assessment of the spatial and seasonal AOD–PM2.5 relationships of slope, intercepts, and correlation coefficients. Only data from ground monitors accessible through an open air-quality portal that are available to the worldwide community for air quality research and decision making are used in this study. These statistics that are reported 1 × 1-degree resolution are important since satellite AOD is often used in conjunction with spatially limited surface PM2.5 monitors to estimate global distributions of surface particulate matter concentrations. Results indicate that more than 3000 ground monitors are now available for PM2.5 studies. While there is a large spread in correlation coefficients between AOD and PM2.5, globally, averaged over all seasons, the correlation coefficient is 0.55 with a unit AOD producing 54 μgm−3 of PM2.5 (Slope) with an intercept of 8 μgm−3. While the number of surface PM2.5 measurements has increased by a factor of 10 over the last decade, a concerted effort is still needed to continue to increase these monitors in areas that have no surface monitors, especially in large population centers that will further leverage the strengths of satellite data.
16
Patil, A., and J. Navrátil. "CFD analysis of wing-propeller interaction on the NASA X-57 Maxwell aircraft wing." Journal of Physics: Conference Series 2716, no. 1 (March 1, 2024): 012002. http://dx.doi.org/10.1088/1742-6596/2716/1/012002.
Abstract:
Abstract Due to global warming concerns, the Aviation industry is trying to reduce its carbon footprint. Electric propulsion (EP) is one way of doing this, where the power is obtained from electrical sources. The concept of distributed electric propulsion (DEP) is in the focus now. NASA’s X-57 Maxwell, a high winged, all-electric experimental aircraft, uses this concept. The present work aims at developing a CFD model (ANSYS Fluent) to evaluate aerodynamic performance of two configurations of NASA’s X-57 aircraft wing; (i) wing and nacelle (clean wing) and (ii) wing, nacelle and one electric propeller under cruise condition; and compare it with the results of wind tunnel experiment performed by NASA/Armstrong X-57 research program. Parameters like lift, drag and pressure coefficients (CL, CD, CP) are compared for both cases. A good match is observed for CL, CD and CP, thus validating the model. The unsteady RANS solver is very efficient in capturing the effects of propeller slipstream on the wing. After validation, this model is further used to simulate aerodynamic performance of a wing with multi-propeller (DEP) configuration.
17
Li, Peng, Bo Li, Xiaoyu Han, Yuji Tian, and Ruoqi Li. "Experimental Study on Wind Loading Characteristics of Trains under Stationary Tornado-like Vortices." Buildings 12, no. 9 (September 3, 2022): 1377. http://dx.doi.org/10.3390/buildings12091377.
Abstract:
The risk of trains being hit by tornadoes in China continues to increase due to the increasing density of railway lines and the shortening of the train departure intervals and the increasing probability of extreme weather phenomena caused by global climate change. If a train is hit by a tornado, it will cause huge casualties and economic losses, so it is necessary to investigate the tornado-induced effects on trains. A series of rigid-model wind pressure measurement tests on a train car under tornado wind loading were conducted using a tornado-vortex simulator, in order to determine the effects of the distance between the train car and the tornado’s center, the swirl ratio of a tornado-like vortex, and the ground roughness on the wind pressure distributions and wind load characteristics on trains. Apparent discrepancies were observed between tornado-induced wind loading and lateral wind loading obtained from conventional boundary-layer wind tunnel tests. The wind pressure and wind load on the car surface are mainly affected by the combined effects of the aerodynamic flow-structure interaction and the pressure drop accompanying the tornado within 1.5 times the vortex core’s radius, and the impact of tornado-like vortices on the train car is almost negligible as the distance from the train car to the tornado’s center exceeds three times vortex core’s radius. The variation trend of mean/fluctuating pressure coefficients is generally consistent. Large values of fluctuating pressure exist mainly on the top and side surfaces of the train car, especially the side surface proximal to the tornado’s center. The most unfavorable mean sectional side force coefficients were found when the train car is located in the tornado’s core and the largest lift force coefficients at the tornado’s center. The overall side force coefficients peaked when the train car is located at a distance of 1.5 times the tornado’s core radius, whereas the largest lift force coefficients were found when the train car was located at the tornado’s center. The overall distribution patterns of the wind force coefficients of the car under different swirl ratios and ground roughness levels are basically the same. The peak aerodynamic force value increases with increasing swirl ratio, and it decreases as ground roughness increases.
18
Bosak, Grzegorz. "Wind tunnel tests of wind action on a high-rise building." Budownictwo i Architektura 13, no. 2 (June 11, 2014): 163–71. http://dx.doi.org/10.35784/bud-arch.1891.
Abstract:
The paper summarizes the results of wind tunnel tests of a wind action on a high-rise building design in Warsaw. Measurements were accomplished in Wind Engineering Laboratory of Cracow University of Technology. Wind pressures on external surfaces of the building model were acquired. A study of the character of the wind action on a tower of the building was the main aim of the paper. A triangle shape with rounded corners of the cross section of the tower and a complex group of neighbor buildings support aerodynamic analysis in a wind tunnel. Wind pressure coefficients on the external building surfaces and the global horizontal wind action on the building tower on full scale were analyzed.
19
Lu, Yi. "Optimizing vehicle aerodynamics through the synergistic application of Design of Experiments (DoE) and Computational Fluid Dynamics (CFD)." Highlights in Science, Engineering and Technology 76 (December 31, 2023): 544–63. http://dx.doi.org/10.54097/ns22b830.
Abstract:
The aerodynamic design of cars not only creates aesthetic and diverse car shapes, but also ensures their safety and fuel economy. According to Mustafa Cakir's research[1], approximately of the fuel consumption of a car traveling at high speeds is used to counteract air resistance. However, with the increasing severity of global warming, emissions standards for automobile exhaust are becoming increasingly stringent. Considering that gasoline vehicles still dominate the household car market, optimizing the aerodynamic design of automobiles is imperative. This work analyzes and optimizes the aerodynamic design of automobiles through the synergistic application of Design of Experiments (DoE) and Computational Fluid Dynamics (CFD). Before conducting experiments, the article first introduces and derives the basic control equations of computational fluid dynamics, namely the continuity equation and Navier-Stokes equation, and describes how they are used in experiments. Then, the article briefly introduces the drag coefficients of automobiles, which are important theoretical basis for subsequent aerodynamic design optimization in this article. In the experimental part, this study focuses on the influence of four important design parameters: angle of the front window , angle of the hood , angle of the back window , and length of the trunk . Using Solidworks 3D modeling software, the article simulates these design parameters and prepares for CFD numerical simulation by geometry, setting computational domain, boundary conditions, and objective functions, and generating mesh. Based on the DoE and numerical simulation results, the article ultimately selects a front window angle of , a hood angle of , a back window of , and as the optimized design. Compared with the basic model, the optimized model reduces the drag coefficient by about . The conclusion of this study provides ideas and theoretical basis for the aerodynamic optimization design of new generation automobiles with the incorporation of DoE. However, the design parameters of automobiles are countless, and in the future, this article will strive to research and simulate more diverse automobile designs and analyze their aerodynamic performance to explore more optimized designs.
20
Abu-Abdou, K., and M. F. Zedan. "Performance of improved thin aerofoil theory for modern aerofoil sections." Aeronautical Journal 95, no. 942 (February 1991): 64–70. http://dx.doi.org/10.1017/s0001924000023526.
Abstract:
AbstractThe improved thin aerofoil method, which features extended expressions for lift and moment coefficients, is considered for further investigation and validation. The procedure to calculate the singularity coefficients is improved by using all aerofoil coordinates as control points in a least squares scheme. The classical NACA 0012 and NACA 65012 sections, the modern aviation aerofoil LS(1)—0417 and the extremely thick Kennedy-Marsden aerofoil are validated in place of the previously cited Karman-Trefftz aerofoil. This selection covers thickness ratios of up to 27·9%, camber ratios up to 7·69% and incidence up to 16·7°. Comparisons of velocity (or pressure) distributions and aerodynamic coefficients are made with two panel methods and with exact solution or experimental results whichever is available. Results indicated that the accuracy of the extended method is much better than expected and compares well with panel methods except for the extremely thick aerofoil. Additional results in the form of a systematic investigation of a weighted global error in the pressure distribution for the Karman-Trefftz aerofoils used in the previous study, are also included. Such an error shows similar trends and in many cases comparable magnitude to the errors generated by panel methods.
21
Zhao, Jian, Haiyang Li, Xiangyue He, Yuechen Huang, and Jianghui Liu. "Uncertainty Analysis for Return Trajectory of Vertical Takeoff and Vertical Landing Reusable Launch Vehicle." Mathematical Problems in Engineering 2020 (July 11, 2020): 1–18. http://dx.doi.org/10.1155/2020/4313758.
Abstract:
The uncertainties during the return trajectory of vertical takeoff and vertical landing reusable launch vehicle weaken the ability of precision landing and make the return process more challenging. This paper is devoted to quantifying the probability uncertainty of return trajectory with uncertain parameters. The uncertainty model of return multi-flight-phase under the uncertainties of initial flight path angle, axial aerodynamic coefficient, and atmospheric density is established using the generalized polynomial chaos expansion method. By parameterizing random uncertainties and introducing random parameters into the uncertainty model, the uncertainty analysis problem of return trajectory is transformed into stochastic trajectory approximation problem. The coefficients of the polynomial basis function are solved by the stochastic collocation method. Then state solutions, statistical properties, and global sensitivity with Sobol index are established based on coefficients. The simulation results show the efficiency and accuracy of this method compared with the Monte Carlo method, the evolution process of main output parameters under random parameters, and relative importance for random parameters. Through the uncertainty analysis of the return trajectory, the robustness of return trajectory can be quantified, which is contributed to improving the safety, reliability, and robustness of recovery and landing mission.
22
Eiximeno, Benet, Carlos Tur-Mongé, Oriol Lehmkuhl, and Ivette Rodríguez. "Hybrid Computation of the Aerodynamic Noise Radiated by the Wake of a Subsonic Cylinder." Fluids 8, no. 8 (August 21, 2023): 236. http://dx.doi.org/10.3390/fluids8080236.
Abstract:
The noise radiated by the flow around a cylinder in the subcritical regime at ReD=1×104 and at a subsonic Mach number of M=0.5 is here studied. The aerodynamic sound radiated by a cylinder has been studied with a wide range of Reynolds numbers, but there are no studies about how the Mach number affects the acoustic field in the subsonic regime. The flow field is resolved by means of large-eddy simulations of the compressible Navier–Stokes equations. For the study of the noise propagation, formulation 1C of the Ffowcs Williams–Hawkings analogy is used. The fluid flow results show good agreement when comparing the surface pressure coefficient, the recirculation length, the vortex shedding frequency and the force coefficients against other studies performed under similar conditions. The dynamic mode decomposition of the pressure fluctuations is used to relate them with the far-field noise. It is shown that, in contrast to what happens for low Mach numbers, quadrupoles have a significant impact mainly in the observers located in the streamwise direction. This effect leads to a global monopole directivity pattern as the shear fluctuations compensate for the lower value of the aeolian tone away from the cross-stream direction.
23
Kepekci, Haydar. "Comparative Numerical Aerodynamics Performance Analysis of NACA0015 and NACA4415 Airfoils." International Journal of Engineering, Science and Information Technology 2, no. 1 (January 18, 2022): 144–51. http://dx.doi.org/10.52088/ijesty.v2i1.236.
Abstract:
The climate crisis caused by global greenhouse gas emissions has led to many disasters around the world in recent years. Some of these disasters are floods in various parts of Europe, melting of Arctic glaciers, and rising water levels in the oceans. People living on islands in Southeast Asian countries are forced to migrate due to rising water levels. With the increase in the frequency of such situations, life on earth is at risk. Greenhouse gas emissions harm not only humans but also animals and plants. The most effective measure that can be taken against this is to stay away from fossil fuels. With the use of fossil fuels, the carbon ratio in the atmosphere increases, and climatic imbalances occur. For this reason, the interest in alternative energy sources is increasing. Wind energy is one of the most widely used renewable energy sources. This is due to the low cost of installation and ease of use. The most important factor affecting the aerodynamic efficiency of wind turbines is the blade profiles. Numerous types of wing profiles have been designed and put into use. In this study, numerical analyzes of NACA 0015 and NACA 4415 airfoils at various angles of attack were performed by determining forces every five degrees between 0 and 20 degrees using ANSYS Fluent commercial software. Lift coefficients and drag coefficients were also calculated for the angles of attack used. According to the analysis results obtained, optimum attack angles were found for each airfoil. As a result, NACA0015 and NACA4415 airfoils were compared in terms of their performance.
24
Pytel, Krzysztof, Stanislaw Gumula, Piotr Dudek, Sebastian Bielik, Szymon Szpin, Wiktor Hudy, Małgorzata Piaskowska – Silarska, and Marcin Kowalski. "Testing the performance characteristics of specific profiles for applications in wind turbines." E3S Web of Conferences 108 (2019): 01015. http://dx.doi.org/10.1051/e3sconf/201910801015.
Abstract:
The publication presents the results of aerodynamic characteristics of selected profile blades for applications in wind turbines. Considering the potential of energy resources and investors’ preferences, the amount of energy produced in wind farms in the total amount of electricity generated will be systematically growing and probably, in the next few years, wind energy will be the first in the field of electricity production from all types of power plants. Harnessing the power of moving air masses is now a global phenomenon. Rotor wheel converts wind energy into mechanical energy when using blades with chosen shape and oriented in the terms of the optimum performance. The aim of the measurements was to determine the impact of blade shape and blade angle of attack on the efficiency of conversion of wind energy into mechanical energy on the rotor wheel. The obtained power coefficients were presented as results.
25
Svorcan, Jelena. "WMLES of flows around small-scale propellers - estimating aerodynamic performance and wake visualization." Theoretical and Applied Mechanics, no. 00 (2023): 10. http://dx.doi.org/10.2298/tam231012010s.
Abstract:
Wall-modeled large-eddy simulation (WMLES) is an advanced mathematical model for turbulent flows which solves for the low-pass filtered numerical solution. A subgrid-scale (SGS) model is used to account for the effects of unresolved small-scale turbulent structures on the resolved scales (i.e. for the dissipation of the smaller scales), while the flow behavior near the walls is modeled by wall functions (thus reducing the requirements for mesh fineness/ quality). This paper investigates the possibilities of applying WMLES in the estimation of aerodynamic performance of small-scale propellers, as well as in the analysis of the wake forming downstream. Induced flows around two propellers designed for unmanned air vehicles (approximately 25 cm and 75 cm in diameter) in hover are considered unsteady and turbulent (incompressible or compressible, respectively). Difficulties in computing such flows mainly originate from the relatively low values of Reynolds numbers (several tens to several hundreds of thousands) when transition and other flow phenomena may be present. The choice of the employed numerical model is substantiated by comparisons of resulting numerical with available experimental data. Whereas global quantities, such as thrust and power (coefficients), can be predicted with satisfactory accuracy (up-to several percents), distinguishing the predominant flow features remains challenging (and requires additional computational effort). Here, wakes forming aft of the propeller rotors are visualized and analyzed. These two benchmark examples provide useful guidelines for further numerical and experimental studies of small-scale propellers.
26
Bekemeyer, P., R. Thormann, and S. Timme. "Rapid gust response simulation of large civil aircraft using computational fluid dynamics." Aeronautical Journal 121, no. 1246 (September 21, 2017): 1795–807. http://dx.doi.org/10.1017/aer.2017.104.
Abstract:
ABSTRACTSeveral critical load cases during the aircraft design process result from atmospheric turbulence. Thus, rapidly performable and highly accurate dynamic response simulations are required to analyse a wide range of parameters. A method is proposed to predict dynamic loads on an elastically trimmed, large civil aircraft using computational fluid dynamics in conjunction with model reduction. A small-sized modal basis is computed by sampling the aerodynamic response at discrete frequencies and applying proper orthogonal decomposition. The linear operator of the Reynolds-averaged Navier-Stokes equations plus turbulence model is then projected onto the subspace spanned by this basis. The resulting reduced system is solved at an arbitrary number of frequencies to analyse responses to 1-cos gusts very efficiently. Lift coefficient and surface pressure distribution are compared with full-order, non-linear, unsteady time-marching simulations to verify the method. Overall, the reduced-order model predicts highly accurate global coefficients and surface loads at a fraction of the computational cost, which is an important step towards the aircraft loads process relying on computational fluid dynamics.
27
Bantscheff, Konstantin, and Christian Breitsamter. "Dynamic Structural Scaling Concept for a Delta Wing Wind Tunnel Configuration Using Additive Manufacturing." Aerospace 10, no. 7 (June 22, 2023): 581. http://dx.doi.org/10.3390/aerospace10070581.
Abstract:
Considering aeroelastic effects plays a vital role in the aircraft design process. The construction of elastic wind tunnel models is a critical element in the investigation of occurring aeroelastic phenomena. However, the structural scaling between full-scale and reduced-scale configurations is a complex design and manufacturing task and is usually avoided in wind tunnel testing. This work proposes a numerical approach for a dynamic aeroelastic scaling technique, which is applied to a fictive delta wing configuration. This scaling methodology is designed to optimise the structural layout of wind tunnel models with an integrated rib and spar structure to meet the behaviour of a realistic full-scale equivalent. For the modelling approach of the wing structure, a beam and shell structure is utilised. The applied scaling laws for the relevant quantities and the applied procedures are described. Computational fluid dynamics (CFD) calculations are performed by solving the Reynolds-averaged Navier–Stokes (RANS) equations for the assumption of a rigid full-scale and down-scaled wing. These calculations are used to verify the aerodynamic scaling assumptions, which are applied to the scaling procedure of the wind tunnel model. Global aerodynamic coefficients are evaluated for a variety of angles of attack. The local flow phenomena of the full-scale and the scaled model are compared in more detail for a medium and a high angle of attack. The pressure coefficient distribution shows a proper accordance for the full-scale and the scaled model. To verify the results of the structural scaling optimisation, a high-fidelity structural full-scale model is compared with the scaled model using the ELFINI FEM solver. Therefore, all structural components are modelled by 2D elements. The results for the reduced eigenfrequencies and according modes of the full-scale and the scaled model show a high level of similarity. A static deformation of the structural grids is performed by applying the aerodynamic loads from the CFD simulations. The results show that the deviation of the nondimensional deformation between the scaled and the full-scale model is negligible. Consequently, the applied scaling methodology proves to be a valuable tool for the conceptual approach of designing aeroelastically scaled wind tunnel models considering 3D-printed material.
28
Allet, A., S. Halle´, and I. Paraschivoiu. "Numerical Simulation of Dynamic Stall Around an Airfoil in Darrieus Motion." Journal of Solar Energy Engineering 121, no. 1 (February 1, 1999): 69–76. http://dx.doi.org/10.1115/1.2888145.
Abstract:
The objective of this study is to investigate the two-dimensional unsteady flow around an airfoil undergoing a Darrieus motion in dynamic stall conditions. For this purpose, a numerical solver based on the solution of the Reynolds-averaged Navier-Stokes equations expressed in a streamfunction-vorticity formulation in a non-inertial frame of reference was developed. The governing equations are solved by the streamline upwind Petrov-Galerkin finite element method (FEM). Temporal discretization is achieved by second-order-accurate finite differences. The resulting global matrix system is linearized by the Newton method and solved by the generalized minimum residual method (GMRES) with an incomplete triangular factorization preconditioning (ILU). Turbulence effects are introduced in the solver by an eddy viscosity model. Our investigation centers on an evaluation of the algebraic Cebeci-Smith model (CSM) and the nonequilibrium Johnson-King model (JKM). In an effort to predict dynamic stall features on rotating airfoils, first we present some testing results concerning the performance of both turbulence models for the flat plate case. Then, computed flow structure together with aerodynamic coefficients for a NACA 0015 airfoil in Darrieus motion under dynamic stall conditions are presented.
29
Eftekhari, Hesam, Abdulkareem Sh Mahdi Al-Obaidi, and Sucharita Srirangam. "Numerical Investigation of Hybrid Savonius-Darrieus Vertical Axis Wind Turbine at Low Wind Speeds." Journal of Physics: Conference Series 2523, no. 1 (July 1, 2023): 012032. http://dx.doi.org/10.1088/1742-6596/2523/1/012032.
Abstract:
Abstract The need for electricity on the Earth is increasing day by day, and this requires building more electric power plants where most of the power plants cause CO2 emission which would increase the global warming. Using wind energy as one type of renewable energies, would contribute to reduce the global warming. In countries such as Malaysia where the average annual wind speed is 2-2.5 m/s using wind energy is a challenge because of the low wind speed. However, using a hybrid Savonius-Darrieus vertical axis wind turbine in low wind speed areas, the performance of the wind turbine may increase, and the starting rotation speed will decrease. This research aims at a comprehensive study on a hybrid Savonius-Darrieus wind turbine with helical Savonius rotor combined with helical and straight bladed Darrieus rotor. In this research, a base model with the name of Model Base was generated and two models with new configurations were generated in SOLIDWORKS. A numerical studies and simulation were conducted on these three designs using Ansys Fluent to identify the more suitable combination for low wind speed areas. Based on the obtained result hybrid Savonius-Darrieus with helical Savonius rotor and helical Darrieus rotor were found to be the most suitable combination because of their stable aerodynamic performance throughout a full rotation. Best performance for these models was found to be at 0.45 TRS with maximum torque and power coefficients of 0.68 and 0.306 respectively.
30
Dudley, R., and P. Chai. "Animal flight mechanics in physically variable gas mixtures." Journal of Experimental Biology 199, no. 9 (September 1, 1996): 1881–85. http://dx.doi.org/10.1242/jeb.199.9.1881.
Abstract:
Empirical studies of animal flight performance have generally been implemented within the contemporary atmosphere. Experimental alteration of the physical composition of gas mixtures, however, permits construction of novel flight media and the non-invasive manipulation of flight biomechanics. For example, replacement of atmospheric nitrogen with various noble gases results in a tenfold variation in air density at a constant oxygen concentration. Such variation in air density correspondingly elicits extraordinary biomechanical effort from flying animals; hummingbirds and euglossine orchid bees hovering in such low-density but normoxic mixtures have demonstrated exceptionally high values for the mechanical power output of aerobic flight muscle. As with mechanical power, lift coefficients during hovering increase at low air densities in spite of a concomitant decline in the Reynolds number of the wings. The physical effects of variable gas density may also be manifest in morphological and physiological adaptations of animals to flight across altitudinal gradients. Global variation in atmospheric composition during the late Paleozoic may also have influenced the initial evolution and subsequent diversification of ancestral pterygotes. For the present-day experimenter, the use of physically variable flight media represents a versatile opportunity to explore the range of kinematic and aerodynamic modulation available to flying animals.
31
Wang, Lin, Xinzi Tang, and Xiongwei Liu. "Blade Design Optimisation for Fixed-Pitch Fixed-Speed Wind Turbines." ISRN Renewable Energy 2012 (August 16, 2012): 1–8. http://dx.doi.org/10.5402/2012/682859.
Abstract:
Fixed-pitch fixed-speed (FPFS) wind turbines have some distinct advantages over other topologies for small wind turbines, particularly for low wind speed sites. The blade design of FPFS wind turbines is fundamentally different to fixed-pitch variable-speed wind turbine blade design. Theoretically, it is difficult to obtain a global mathematical solution for the blade design optimisation. Through case studies of a given baseline wind turbine and its blade airfoil, this paper aims to demonstrate a practical method for optimum blade design of FPFS small wind turbines. The optimum blade design is based on the aerodynamic characteristics of the airfoil, that is, the lift and drag coefficients, and the annual mean wind speed. The design parameters for the blade optimisation include design wind speed, design tip speed ratio, and design attack angle. A series of design case studies using various design parameters are investigated for the wind turbine blade design. The design outcomes are analyzed and compared to each other against power performance of the rotor and annual energy production. The design outcomes from the limited design cases demonstrate clearly which blade design provides the best performance. This approach can be used for any practice of FPFS wind turbine blade design and refurbishment.
32
BALABAN, Anton, Sorin BERBENTE, Andrei NEAMTU, Gabriela-Liliana STROE, Emil COSTEA, Irina-Beatrice STEFANESCU, Irina-Carmen ANDREI, and Ionel POPESCU. "Case study of TCAS implementation in modern FMS." INCAS BULLETIN 15, no. 2 (June 9, 2023): 11–19. http://dx.doi.org/10.13111/2066-8201.2023.15.2.2.
Abstract:
In this paper, uncertainty is included in the extended framework of global air traffic both through the action of the wind and through the incomplete determination of the aerodynamic coefficients and the inevitable imprecision involved in the execution of ATC instructions. In order to study the air conflict detection process in detail, the possibility of potential conflicts must be evaluated, considering the current state of the international airspace, and taking into account the uncertainty in calculating the future position of the aircraft. A mathematical model for predicting potential aerial conflicts is necessary for this objective. In a probabilistic framework, the mathematical model thus created could be either an empirical distribution of future aircraft positions in space or a dynamic model, such as a stochastic differential equation, that describes the movement of the aircraft and implicitly defines a distribution for the position’s future of the aircraft/ future aircraft positions. Based on the prediction model, aircraft flight safety matrices can be evaluated. The mathematical methods applied in the Detection and Resolution of Air Traffic Conflicts - CDR involve a wide range of fields, but also the appropriate modeling of physical systems such as airplanes, the codification of mathematical algorithms for conflict detection, as well as the properly applied procedures for resolving potential air conflicts.
33
Benavent-Oltra, Jose Antonio, Juan Andrés Casquero-Vera, Roberto Román, Hassan Lyamani, Daniel Pérez-Ramírez, María José Granados-Muñoz, Milagros Herrera, et al. "Overview of the SLOPE I and II campaigns: aerosol properties retrieved with lidar and sun–sky photometer measurements." Atmospheric Chemistry and Physics 21, no. 12 (June 17, 2021): 9269–87. http://dx.doi.org/10.5194/acp-21-9269-2021.
Abstract:
Abstract. The Sierra Nevada Lidar aerOsol Profiling Experiment I and II (SLOPE I and II) campaigns were intended to determine the vertical structure of aerosols by remote sensing instruments and test the various retrieval schemes for obtaining aerosol microphysical and optical properties with in situ measurements. The SLOPE I and II campaigns were developed during the summers of 2016 and 2017, respectively, combining active and passive remote sensing with in situ measurements at stations belonging to the AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere) in the Granada area (Spain). In this work, we use the in situ measurements of these campaigns to evaluate aerosol properties retrieved by the GRASP code (Generalized Retrieval of Atmosphere and Surface Properties) combining lidar and sun–sky photometer measurements. We show an overview of aerosol properties retrieved by GRASP during the SLOPE I and II campaigns. In addition, we evaluate the GRASP retrievals of total aerosol volume concentration (discerning between fine and coarse modes), extinction and scattering coefficients, and for the first time we present an evaluation of the absorption coefficient. The statistical analysis of aerosol optical and microphysical properties, both column-integrated and vertically resolved, from May to July 2016 and 2017 shows a large variability in aerosol load and types. The results show a strong predominance of desert dust particles due to North African intrusions. The vertically resolved analysis denotes a decay of the atmospheric aerosols with an altitude up to 5 km a.s.l. Finally, desert dust and biomass burning events were chosen to show the high potential of GRASP to retrieve vertical profiles of aerosol properties (e.g. absorption coefficient and single scattering albedo) for different aerosol types. The aerosol properties retrieved by GRASP show good agreement with simultaneous in situ measurements (nephelometer, aethalometer, scanning mobility particle sizer, and aerodynamic particle sizer) performed at the Sierra Nevada Station (SNS) in Granada. In general, GRASP overestimates the in situ data at the SNS with a mean difference lower than 6 µm3 cm−3 for volume concentration, and 11 and 2 Mm−1 for the scattering and absorption coefficients. On the other hand, the comparison of GRASP with airborne measurements also shows an overestimation with mean absolute differences of 14 ± 10 and 1.2 ± 1.2 Mm−1 for the scattering and absorption coefficients, showing a better agreement for the absorption (scattering) coefficient with higher (lower) aerosol optical depth. The potential of GRASP shown in this study will contribute to enhancing the representativeness of the aerosol vertical distribution and provide information for satellite and global model evaluation.
34
Hamiga, Władysław Marek, and Wojciech Bronisław Ciesielka. "Numerical Analysis of Aeroacoustic Phenomena Generated by Heterogeneous Column of Vehicle." Energies 15, no. 13 (June 25, 2022): 4669. http://dx.doi.org/10.3390/en15134669.
Abstract:
The last decade has seen an exponential interest in conventional and unconventional energy issues. This trend has also extended to road transport issues and is driven by expectations to minimize fuel and/or energy consumption and negative environmental impact. In the global literature, much attention is focused on the work of autonomous transport, both passenger and trucks, and on the phenomena of platooning. The paper presents original aerodynamic and aeroacoustic tests of heterogeneous vehicle columns. In the work, models of a car, a van and a truck were built, followed by heterogeneous columns with different distances between the vehicles. Computational fluid dynamics (CFD) methods and two turbulence models, k−ω shear stress transport (SST) and large eddy simulation (LES), were used in this study. The study enabled the determination of drag coefficients and lift force. Application of the Ffowcs Williams–Hawkings (FW-H) analogy allowed for the determination of the distributions of sound pressure levels generated by moving vehicles and columns of vehicles. In order to verify the developed models, acoustic field measurements were made for the following passages: passenger car, van, and truck. Acoustic pressure level and A-weighted sound level (SPL) were measured in Krakow and in its vicinity. Research has shown that grouping vehicles into optimal columns and maintaining distances between vehicles using modern control systems can result in significant energy savings and reduce harmful emissions to the environment.
35
You, Wonhee, Hyukbin Kwon, Joonhyuk Park, and Yujeong Shin. "Effect of wind gusts on the dynamics of railway vehicles running on a curved track." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, no. 4 (June 13, 2017): 1103–20. http://dx.doi.org/10.1177/0954409717708924.
Abstract:
Due to global warming, there is an increasing number of wind gusts that affect the stability of railway vehicles. A railway vehicle running on a curved track during a wind gust is subjected to multiple forces simultaneously, which include the centrifugal force and forces exerted by the wind gust and cant, and they significantly affect the vehicle’s dynamic characteristics as well as its safety. The forces increase the vibration of carbodies and the risk of derailment and overturning of cars; the effect is worse on irregular tracks. In order to review the phenomenon in detail, a 1/20 scale model of a railway vehicle was built to measure the aerodynamic coefficients in five directions—side force, lift force, roll moment, pitch moment, and yaw moment—through a wind tunnel test. The data collected were applied as external forces to a full-scale railway vehicle model traveling on a curved track. Using a multibody simulation software program, SIMPACK, a railway vehicle was modeled, which was then used in the simulation of the dynamic characteristics and safety of vehicles while traveling on a curved track during a wind gust. Using the actual measured track data from the curved zone, a comparison was made on the dynamic characteristics of the car traveling, with and without a wind gust, on a curved track with a railway curve radius of 599 m; also, the difference was analyzed with the direction of the wind gust blowing from inside and toward the center of curvature. The results showed that in the presence of a wind gust blowing from outside the curvature with an average speed of 25 m/s it is advisable to stop train services on grounds of safety.
36
Engelbrecht, Johann P., Hans Moosmüller, Samuel Pincock, R. K. M. Jayanty, Traci Lersch, and Gary Casuccio. "Technical note: Mineralogical, chemical, morphological, and optical interrelationships of mineral dust re-suspensions." Atmospheric Chemistry and Physics 16, no. 17 (August 31, 2016): 10809–30. http://dx.doi.org/10.5194/acp-16-10809-2016.
Abstract:
Abstract. This paper promotes an understanding of the mineralogical, chemical, and physical interrelationships of re-suspended mineral dusts collected as grab samples from global dust sources. Surface soils were collected from arid regions, including the southwestern USA, Mali, Chad, Morocco, Canary Islands, Cabo Verde, Djibouti, Afghanistan, Iraq, Kuwait, Qatar, UAE, Serbia, China, Namibia, Botswana, Australia, and Chile. The < 38 µm sieved fraction of each sample was re-suspended in a chamber, from which the airborne mineral dust could be extracted, sampled, and analyzed. Instruments integrated into the entrainment facility included two PM10 and two PM2.5 filter samplers, a beta attenuation gauge for the continuous measurement of PM10 and PM2.5 particulate mass fractions, an aerodynamic particle size analyzer, and a three-wavelength (405, 532, 781 nm) photoacoustic instrument with integrating reciprocal nephelometer for monitoring absorption and scattering coefficients during the dust re-suspension process. Filter sampling media included Teflon® membrane and quartz fiber filters for chemical analysis and Nuclepore® filters for individual particle analysis by scanning electron microscopy (SEM). The < 38 µm sieved fractions were also analyzed by X-ray diffraction for their mineral content while the > 75, < 125 µm soil fractions were mineralogically assessed by optical microscopy. Presented here are results of the optical measurements, showing the interdependency of single-scattering albedos (SSA) at three different wavelengths and mineralogical content of the entrained dust samples. To explain the elevated concentrations of iron (Fe) and Fe ∕ Al ratios in the soil re-suspensions, we propose that dust particles are to a large extent composed of nano-sized particles of micas, clays, metal oxides, and ions of potassium (K+), calcium (Ca2+), and sodium (Na+) evenly dispersed as a colloid or adsorbed in amorphous clay-like material. Also shown are differences in SSA of the kaolinite/hematite/goethite samples from Mali and those from colloidal soils elsewhere. Results from this study can be integrated into a database of mineral dust properties, for applications in climate modeling, remote sensing, visibility, health (medical geology), ocean fertilization, and impact on equipment.
37
Liu, Chun Ke, and Jiao Wang. "Bus Body Design and Calculation of Aerodynamic Drag Coefficient." Applied Mechanics and Materials 496-500 (January 2014): 2655–59. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.2655.
Abstract:
With the ownership of Chinese automotive increasing, the road is more and more crowded and the energy crisis swept the global at the same time, which requires us to develop the larger buses now. According to the company standard and the related laws and regulations，a 12m bus body is designed. Build the 12m bus body’s 3D model by UniGraphics NX，generate mesh generation about the 3D model in the GAMBIT and calculate the aerodynamic drag coefficient using the FLUENT software, after all this, the 12m bus body whose the aerodynamic drag coefficient meets the needs of low speed characteristics is successfully designed.
38
Cheng, Ji, Ping Jiang, Qi Zhou, Jiexiang Hu, Tao Yu, Leshi Shu, and Xinyu Shao. "A lower confidence bounding approach based on the coefficient of variation for expensive global design optimization." Engineering Computations 36, no. 3 (April 8, 2019): 830–49. http://dx.doi.org/10.1108/ec-08-2018-0390.
Abstract:
PurposeEngineering design optimization involving computational simulations is usually a time-consuming, even computationally prohibitive process. To relieve the computational burden, the adaptive metamodel-based design optimization (AMBDO) approaches have been widely used. This paper aims to develop an AMBDO approach, a lower confidence bounding approach based on the coefficient of variation (CV-LCB) approach, to balance the exploration and exploitation objectively for obtaining a global optimum under limited computational budget.Design/methodology/approachIn the proposed CV-LCB approach, the coefficient of variation (CV) of predicted values is introduced to indicate the degree of dispersion of objective function values, while the CV of predicting errors is introduced to represent the accuracy of the established metamodel. Then, a weighted formula, which takes the degree of dispersion and the prediction accuracy into consideration, is defined based on the already-acquired CV information to adaptively update the metamodel during the optimization process.FindingsTen numerical examples with different degrees of complexity and an AIAA aerodynamic design optimization problem are used to demonstrate the effectiveness of the proposed CV-LCB approach. The comparisons between the proposed approach and four existing approaches regarding the computational efficiency and robustness are made. Results illustrate the merits of the proposed CV-LCB approach in computational efficiency and robustness.Practical implicationsThe proposed approach exhibits high efficiency and robustness in engineering design optimization involving computational simulations.Originality/valueCV-LCB approach can balance the exploration and exploitation objectively.
39
Marepally, Koushik, Yong Su Jung, James Baeder, and Ganesh Vijayakumar. "Uncertainty quantification of wind turbine airfoil aerodynamics with geometric uncertainty." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042041. http://dx.doi.org/10.1088/1742-6596/2265/4/042041.
Abstract:
Abstract An artificial neural network based reduced order model (ROM) is developed to predict the load coefficients and performance of wind turbine airfoils. The model is trained using a representative database of 972 wind turbine airfoil shapes generated by perturbing the design parameters in each of 12 baseline airfoils defining commercially relevant modern wind turbines. The predictions from our ROM show excellent agreement with the CFD data, with a 99th percentile maximum errors of 0.03 in lift-coefficient, 2 in lift-to-drag ratio and 0.002 in pitching moment coefficient. A Monte-Carlo based uncertainty quantification (UQ) and global sensitivity analysis (GSA) framework is developed using this computationally economical ROM. Using UQ, we observed the stall behavior to be very sensitive to geometric uncertainty, with more than 10% deviation in lift coefficient associated to 5% deviation in geometric features. Sobol’s analysis is used to identify the most influencing geometric feature for the stall behavior to be concentrated at the maximum thickness location on the airfoil suction surface.
40
Brown, William, Michael Wiesneth, Thomas Faust, Nghia Huynh, Carlos Montalvo, Kent Lino, and Andrew Tindell. "Measured and simulated analysis of a model rocket." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 4 (February 5, 2018): 1397–411. http://dx.doi.org/10.1177/0954410017752730.
Abstract:
A comparison between two types of sensors and two types of simulation software are investigated here for a student built rocket. Many students use an open source software package called OpenRocket which uses empirical aerodynamics based on the shape of the rocket. This software is compared to the standard set of rigid body dynamic equations using coefficients for the aerodynamics based on windtunnel and computational fluid dynamics tests. During experimentation two sensors are used and price and resolution is compared. The first sensor is a turn-key sensor called the TeleMega which has many features such as telemetry and on board data logging. In an effort to reduce costs, the Arduino Mega platform has been augmented with a custom made shield capable of measuring Global Positioning System (GPS), angular velocity, and attitude information with on board data logging as well. Although this sensor has limited functionality, the cost is substantially reduced. It is shown that all sensors and simulation software have their strengths and weaknesses with appropriate usage for each.
41
Bontempo, Rodolfo, and Marcello Manna. "Verification of the Axial Momentum Theory for Propellers with a Uniform Load Distribution." International Journal of Turbomachinery, Propulsion and Power 4, no. 2 (May 14, 2019): 8. http://dx.doi.org/10.3390/ijtpp4020008.
Abstract:
The paper provides an evaluation of the errors embodied in the Axial Momentum Theory (AMT) as applied to a uniformly loaded actuator disk model without wake rotation. Although this model exhibits some unphysical features, such as the tip singularity and the violation of the angular momentum equation, it is still considered a touchstone in the theoretical aerodynamics of propellers. To simplify the model, a purely mathematical assumption is commonly used in the differential form of the axial momentum equation, i.e., the contribution of the pressure forces on the lateral surface of the infinitesimal streamtubes swallowed by the disk is neglected. In this paper, the errors introduced by this simplifying assumption are evaluated by comparing the results of the AMT with those of a nonlinear method modelling the free wake as the superposition of ring vortices distributed along the wake boundary. Firstly, the validity of this method is verified in terms of global performance coefficients. Then, using a CFD approach, it is also verified in terms of local flow quantities. The comparison between the ring-vortices method and the AMT shows that, for a highly loaded propeller, significant errors exist in the axial velocity at the disk, especially near the tip. Moreover, despite the uniform load, the axial velocity at the disk varies in the radial direction. Instead, the velocity magnitude remains almost uniform only for values of the thrust coefficient lower than 1.
42
Ismail, Shaik, and Jatinder Singh. "Nonlinear Aerodynamic Global Model Identification using Gram-schmidt Orthogonalization." Journal of Aerospace Sciences and Technologies, August 11, 2023, 392–400. http://dx.doi.org/10.61653/joast.v57i4.2005.769.
Abstract:
This paper discusses a simple technique to identify global models for nonlinear aerodynamic force and moment coefficients of aircraft using multivariate orthogonal functions. Classical Gram-Schmidt procedure and Predicted Squared Error metric are used to generate the orthogonal functions. Global models for the F-16 aircraft are identified from a simplified subsonic (Mach < 0.6) wind tunnel database available in open literature. The identified models are compared with those found in literature for the same wind tunnel database and conclusions are drawn.
43
Gaszner, Manuel, Alexander O. Pugachev, Christos Georgakis, and Paul Cooper. "Leakage and Rotordynamic Coefficients of Brush Seals With Zero Cold Clearance Used in an Arrangement With Labyrinth Fins." Journal of Engineering for Gas Turbines and Power 135, no. 12 (September 23, 2013). http://dx.doi.org/10.1115/1.4025236.
Abstract:
A brush-labyrinth sealing configuration consisting of two labyrinth fins upstream and one brush seal downstream is studied experimentally and theoretically. Two slightly different brush seal designs with zero cold radial clearance are considered. The sealing configurations are tested on the no-whirl and dynamic test rigs to obtain leakage performance and rotordynamic stiffness and damping coefficients. The no-whirl tests allow identification of the local rotordynamic direct and cross-coupled stiffness coefficients for a wide range of operating conditions, while the dynamic test rig is used to obtain both global stiffness and damping coefficients but for a narrower operating range limited by the capabilities of a magnetic actuator. Modeling of the brush-labyrinth seals is performed using computational fluid dynamics. The experimental global rotordynamic coefficients consist of an aerodynamic component due to the gas flow and a mechanical component due to the contact between the bristle tips and rotor surface. The computational fluid dynamics (CFD)–based calculations of rotordynamic coefficients provide, however, only the aerodynamic component. A simple mechanical model is used to estimate the theoretical value of the mechanical stiffness of the bristle pack during the contact. The results obtained for the sealing configurations with zero cold radial clearance brush seals are compared with available data on three-tooth-on-stator labyrinth seals and a brush seal with positive cold radial clearance. Results show that the sealing arrangement with a line-on-line welded brush seal has the best performance overall with the lowest leakage and cross-coupled stiffness. The predictions are generally in agreement with the measurements for leakage and stiffness coefficients. The seal-damping capability is noticeably underpredicted.
44
Chenkai, Zhang, Hu Jun, Wang Zhiqiang, and Gao Xiang. "Design Work of a Compressor Stage Through High-To-Low Speed Compressor Transformation." Journal of Engineering for Gas Turbines and Power 136, no. 6 (January 31, 2014). http://dx.doi.org/10.1115/1.4026520.
Abstract:
Low-speed model testing has advantages such as great accuracy and low cost and risk, so it is widely used in the design procedure of the high pressure compressor (HPC) exit stage. The low-speed model testing project is conducted in Nanjing University of Aeronautics and Astronautics (NUAA) to represent aerodynamic load and flow field structure of the seventh stage of a high-performance ten-stage high-pressure compressor. This paper outlines the design work of the low speed four-stage axial compressor, the third stage of which is the testing stage. The first two stages and the last stage provide the compressor with entrance and exit conditions, respectively. The high-to-low speed transformation process involves both geometric and aerodynamic considerations. Accurate similarities demand the same Mach number and Reynolds number, which will not be maintained due to motor power/size and its low-speed feature. Compromises of constraints are obvious. Modeling principles are presented in high-to-low speed transformation. Design work was carried out based on these principles. Four main procedures were conducted successively in the general design, including establishment of low-speed modeling target, global parameter design of modeling stage, throughflow aerodynamic design, and blading design. In global parameter design procedure, rotational speed, shroud diameter, hub-tip ratio, midspan chord, and axial spacing between stages were determined by geometrical modeling principles. During the throughflow design process, radial distributions of aerodynamic parameters such as D-factor, pressure-rise coefficient, loss coefficients, stage reaction, and other parameters were obtained by determined aerodynamic modeling principles. Finally, rotor and stator blade profiles of the low speed research compressor (LSRC) at seven span locations were adjusted to make sure that blade surface pressure coefficients agree well with that of the HPC. Three-dimensional flow calculations were performed on the low-speed four-stage axial compressor, and the resultant flow field structures agree well with that of the HPC. It is worth noting that a large separation zone appears in both suction surfaces of LSRC and HPC. How to diminish it through 3D blading design in the LSRC test rig is our further work.
45
Pacheco, Jaime, André C. Marta, and Luis Eça. "Wind tunnel testing of a Formula Student vehicle for checking CFD simulation trends." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, November 7, 2023. http://dx.doi.org/10.1177/09544070231203076.
Abstract:
The aerodynamic performance analysis of Formula Student racecars has been mostly done by teams with CFD tools, for time and cost savings, that often lack proper validation. To address this, the FST Lisboa team performed a detailed wind tunnel (WT) test campaign, using a one-third scale model, under different configurations, including variable ride heights, bullhorn appendix, and rear wing flap settings, also replicated in CFD. The simulations used RANS with the SST k-omega turbulence model, with a 13.7 million polyhedral mesh for the test chamber region domain. Both experimental and numerical errors were estimated from the instrumentation and mesh convergence analysis, respectively. Comparisons were made between WT and CFD both in terms of local flow, using tufts for flow visualization, and global flow, using lift, drag, and pitching moment coefficients. Overall, the numerical streamlines agreed very well with the orientations of the tufts in experiments, but some discrepancies were found in regions of cross-flow and high-frequency unsteadiness, mainly caused by limitations of the visualization technique. The gamma transition model in CFD was abandoned as it could not replicate the WT observations. In terms of aerodynamic coefficients, a strong correlation was found between WT and CFD. The parametric studies revealed that the simulations captured the experimental sensitivity to each car setting parameter studied but the uncertainties did not enable a full quantitative evaluation of the aerodynamic performance. The drag reduction system significantly impacted the aerodynamic balance of the racecar, while the current bullhorn design proved to be ineffective. The ride height increase led to higher downforce, mostly due to the higher pitch angle of the vehicle, with negligible variation of the aerodynamic balance. This work validated the team CFD studies, building confidence in that trends estimated in numerical parametric studies are likely to be translated to the real prototype performance.
46
Ciorciari, Roberto, Ilker Kirik, and Reinhard Niehuis. "Effects of Unsteady Wakes on the Secondary Flows in the Linear T106 Turbine Cascade." Journal of Turbomachinery 136, no. 9 (May 2, 2014). http://dx.doi.org/10.1115/1.4027374.
Abstract:
In modern low pressure turbines the efforts to increase aerodynamic blade loading by increasing blade pitch and optimizing midspan performance in order to reduce weight and complexity can produce increased losses in the endwall region. Airfoils of high flow turning and high pressure gradients between the blades generate strong secondary flows which impair the global aerodynamic performance of the blades. In addition, the unsteady incoming wakes take influence on transition phenomena on the blade surfaces and the inlet boundary layer, and consequently affect the development and the evolution of the secondary flows. In this paper, the T106 cascade is used to identify the effect of unsteady wakes on the development of secondary flows in a turbine cascade. Numerical and experimental results are compared at different flux coefficients and Strouhal numbers, the relative differences and similarities are analyzed.
47
Shen, Yang, Wei Huang, Zhen-guo Wang, Da-fu Xu, and Chao-Yang Liu. "A deep learning framework for aerodynamic pressure prediction on general three-dimensional configurations." Physics of Fluids 35, no. 10 (October 1, 2023). http://dx.doi.org/10.1063/5.0172437.
Abstract:
In this paper, a deep learning framework is proposed for predicting aerodynamic pressure distributions in general three-dimensional configurations. Based on the PointNet++ structure, the proposed framework extracts shape features based on the geometric representation of point cloud, outputs pressure coefficients corresponding to locations, and is able to accept inputs of point clouds with different resolutions. By PointNet++, we mean that local and global features of three-dimensional configurations could be effectively extracted through a multi-level feature extraction structure. A parametric approach is utilized to generate 2000 different space shuttle three-dimensional shapes, and their flows at the hypersonic speed are solved by computational fluid dynamics (CFD) as a dataset to support the training of the deep learning. Within the dataset, accurate predictions of pressure and aerodynamic forces are demonstrated for 400 unseen testing shapes. Out of the dataset, geometries that are tested for generalizability include slender, waverider, spaceplane, Apollo capsule, lifting body, and rocket. Remarkably, the framework is capable of predicting pressure distributions and aerodynamic forces for the unseen, independently designed geometries of various types in near-real-time and near-CFD accuracy, proving its excellent applicability to general three-dimensional configurations.
48
Su, Shih-Yung, Yung-Po Liaw, Jing-Rong Jhuang, Shu-Yi Hsu, Chun-Ju Chiang, Ya-Wen Yang, and Wen-Chung Lee. "Associations between ambient air pollution and cancer incidence in Taiwan: an ecological study of geographical variations." BMC Public Health 19, no. 1 (November 9, 2019). http://dx.doi.org/10.1186/s12889-019-7849-z.
Abstract:
Abstract Background Air pollution is a global public health concern. The World Health Organization has recently set up a goal of saving 7 million people globally by 2030 from air pollution related death. We conducted an ecological study of geographical variation to explore the association between air pollution (specifically, particulate matter <2.5 μm in aerodynamic diameter [PM2.5], particulate matter <10 μm in aerodynamic diameter, sulfur dioxide, nitrogen dioxide, nitric oxide, and ozone) and cancer incidence in Taiwan, from 2012 to 2016. Methods In this study, the yearly average concentrations of each air pollutant at 75 air quality monitoring stations were calculated, and using the kriging method, the concentrations were extrapolated to each and every geographical central point of 349 local administrative areas of Taiwan. Spearman rank correlation coefficients between the age-adjusted cancer incidence rates and various air pollutants were calculated by stratifying genders and urbanization degrees of the local administrative areas. A total of 70 correlation coefficients were calculated. Results In total, 17 correlation coefficients were significantly positive at an alpha level of 0.05. Among these, four correlation coefficients between the age-adjusted cancer incidence rates and PM2.5 levels remained significant after Bonferroni correction. For men in developing towns, general towns, and aged towns and for women in aged towns, the age-adjusted cancer incidence rates increased 13.1 (95% confidence interval [CI], 8.8–17.6), 11 (95% CI, 5.6–16.4), 16.7 (95% CI, 6.9–26.4), and 11.9 (95% CI, 5.6–18.2) per 100,000 populations, respectively, for every 1 μg/m3 increment in PM2.5 concentrations. Conclusions A significantly positive correlation was observed between the PM2.5 level and cancer incidence rate after multiple testing correction.
49
Yang, B., Q. Xu, L. He, L. H. Zhao, Ch G. Gu, and P. Ren. "A Novel Global Optimization Algorithm and Its Application to Airfoil Optimization." Journal of Turbomachinery 137, no. 4 (April 1, 2015). http://dx.doi.org/10.1115/1.4028712.
Abstract:
In this paper, a novel global optimization algorithm has been developed, which is named as particle swarm optimization combined with particle generator (PSO–PG). In PSO–PG, a PG was introduced to iteratively generate the initial particles for PSO. Based on a series of comparable numerical experiments, it was convinced that the calculation accuracy of the new algorithm as well as its optimization efficiency was greatly improved in comparison with those of the standard PSO. It was also observed that the optimization results obtained from PSO–PG were almost independent of some critical coefficients employed in the algorithm. Additionally, the novel optimization algorithm was adopted in the airfoil optimization. A special fitness function was designed and its elements were carefully selected for the low-velocity airfoil. To testify the accuracy of the optimization method, the comparative experiments were also carried out to illustrate the difference of the aerodynamic performance between the optimized and its initial airfoil.
50
Novotny, Neal L., Markus P. Rumpfkeil, Jose A. Camberos, Eric J. Nielsen, and Boris Diskin. "Aerodynamic Exergy-Based Analysis and Optimization of the Generic Hypersonic Vehicle Using FUN3D." Journal of Aircraft, February 13, 2024, 1–16. http://dx.doi.org/10.2514/1.c037547.
Abstract:
The development of future novel aircraft concepts requires a holistic approach to vehicle design, analysis, and optimization. Aircraft designers can no longer consider components individually as systems become more interconnected and multidisciplinary. Hence, a new approach to aircraft design and a new way to measure the performance of aircraft are needed. A novel approach to aircraft design is the use of exergy methods that can evaluate typically disparate systems using a universal measure of performance mapped to global system performance. This paper introduces a new functional and its adjoint gradient in FUN3D to determine aerodynamic exergy destruction rates. The functional is verified using the Oswatitsch relationship by comparing it to native, surface-based drag coefficients. The adjoint gradient is verified using the FUN3D native complex step method, and discrete agreement is demonstrated for flowfields and geometric derivatives. The new functional is then used for aerodynamic exergy-based analysis and optimization of the generic hypersonic vehicle. An inverse design problem is conducted first to verify the design optimization framework. Finally, a planform and airfoil aerodynamic inviscid exergy optimization of the GHV is conducted, improving exergy destruction rates by 7.1% while making substantial improvements to the cruise trim characteristics of the vehicle.