scholarly journals Effect of Natural Wind on the Transiting Test for Measuring the Aerodynamic Coefficients of Structures

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1493
Author(s):  
Guangxia Zhu ◽  
Xin Liu ◽  
Lulu Liu ◽  
Shengli Li
Keyword(s):  
Aerodynamic Force ◽  
Pressure Coefficient ◽  
Triangular Prism ◽  
Aerodynamic Coefficients ◽  
Force Coefficient ◽  
Moving Vehicle ◽  
Aerodynamic Pressure ◽  
Measurement Results ◽  
Prism Model ◽  
Natural Wind

The aerodynamic coefficients transiting test is a new method for measuring the structural aerodynamic coefficients using the wind generated by a moving vehicle. However, the effect and correction of natural wind on the transiting test has not been studied. Hence, in this study, the investigation of the aerodynamic force and pressure measurements on a special triangular prism model is simulated through the transiting test under different natural wind conditions for 30° and 90° angles of wind incidence. Force and pressure measurement results in the transiting test are used to describe and explain the effect of natural wind in the range of 0–3.0 m/s on the aerodynamic coefficients of the triangular prism qualitatively and quantitatively. The results show that the driving wind field of the vehicle, aerodynamic force coefficient, and aerodynamic pressure coefficient are significantly influenced by strong natural wind greater than 1.71 m/s, which must be considered and so it is recommended that the structure aerodynamic coefficients transiting test should be conducted under the condition that the natural wind is less than 1.71 m/s. In addition, the method of two-direction round-trip measurement is proposed to modify the effect of natural wind on transiting tests.

scholarly journals Characterisation of football trajectories for assessing flight performance

2018 ◽  
Vol 233 (1) ◽  
pp. 16-26
Author(s):  
Matthew Ward ◽  
Martin Passmore ◽  
Adrian Spencer ◽  
Simon Tuplin ◽  
Andy Harland
Keyword(s):  
Aerodynamic Force ◽  
Flight Path ◽  
Force Coefficient ◽  
High Profile ◽  
Inflection Points ◽  
Wide Range ◽  
Identical Manner ◽  
The Difference ◽  
Flight Model ◽  
Mathematical Process

Much discussion surrounds the flight of association footballs (soccer balls), particularly where the flight may be perceived as irregular. This is particularly prevalent in high-profile competitions due to increased camera coverage and public scrutiny. All footballs do not perform in an identical manner in flight. This article develops methods to characterise the important features of flight, enabling direct, quantitative comparisons between ball designs. The system used to generate the flight paths included collection of aerodynamic force coefficient data in a wind tunnel, which were input into a flight model across a wide range of realistic conditions. Parameters were derived from these trajectories to characterise the in-flight deviations across the range of flights from which the aerodynamic performance of different balls were statistically compared. The amount of lateral movement in flight was determined by calculating the final lateral deviation from the initial shot vector. To quantify the overall shape of the flight, increasing orders of polynomial functions were fitted to the flight path until a good fit was obtained with a high-order polynomial indicating a less consistent flight. The number of inflection points in each flight was also recorded to further define the flight path. The orientation dependency of a ball was assessed by comparing the true shot to a second flight path without considering orientation-dependent forces. The difference between these flights isolated the effect of orientation-dependent aerodynamic forces. The article provides the means of quantitatively describing a ball’s aerodynamic behaviour in a defined and robust mathematical process. Conclusions were not drawn regarding which balls are good and bad; these are subjective terms and can only be analysed through comprehensive player perception studies.

Fluidelastic Instability of an Infinite Double Row of Circular Cylinders Subject to a Uniform Cross-Flow

1983 ◽  
Vol 105 (1) ◽  
pp. 59-66 ◽  
Author(s):  
S. J. Price ◽  
M. P. Paidoussis
Keyword(s):  
Aerodynamic Force ◽  
Mass Parameter ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Frequency Detuning ◽  
Complex Flow ◽  
Force Coefficient ◽  
Double Row ◽  
Mechanical Coupling ◽  
Fluid Damping

This paper represents the first stage of a fundamental investigation of the vibration phenomena induced in heat exchanger bundles subject to a cross-flow. Using aerodynamic force coefficient data, obtained experimentally from a static wind tunnel model, a linearized quasi-static analysis is employed to analyze the stability of an infinite double row of circular cylinders in uniform cross-flow. From the analysis it is shown that the instability is a result of the negative fluid damping forces, resulting from the complex flow pattern in the row. A new expression is obtained relating the critical velocity for the onset of instability to the damping parameter, the mass parameter and the pitch ratio of the cylinders. The expression is compared with experimental data available in the literature, from dynamic laboratory results, and a good correlation is obtained. Using this stability analysis the effect of mechanical coupling and frequency detuning, both between modes in one cylinder and modes in adjacent cylinders, is examined. In general it is shown that mechanical coupling is destabilizing and frequency detuning stabilizing.

Study on Numerical Simulation Method of Aerodynamic Performance of High-Speed Train on Bridge

2013 ◽  
Vol 376 ◽  
pp. 312-316 ◽  
Author(s):  
Chao Qun Xiang ◽  
Wen Hua Guo ◽  
Jia Wen Zhang
Keyword(s):  
Static Pressure ◽  
Aerodynamic Performance ◽  
Dynamic Mesh ◽  
Positive Pressure ◽  
Aerodynamic Coefficients ◽  
Force Coefficient ◽  
Rolling Moment ◽  
Velocity Magnitude ◽  
Pressure Distributions ◽  
Mesh Method

The dynamic mesh method that could simulate the actual moving of train was used to calculate the aerodynamic coefficients of train on bridge with wind barriers of various heights, and the static pressure distributions around the train body and velocity magnitude distributions were analyzed, the results computed by dynamic mesh method were compared with that computed by traditional static mesh method. The results show that the aerodynamic coefficients of train and flow field characteristics computed by the two methods agree well under the configuration without wind barriers. However, there is considerable difference between the results computed by the two methods with the installation of wind barriers. It is found that the dynamic mesh method is more reasonable to simulate the aerodynamic coefficients of train with wind barriers by analysis of the contour of static pressure distributions and velocity magnitude distributions. The wind barriers effectively decrease the positive pressure on windward train body and negative pressure on train roof, mainly reduce the side force coefficient, lift force coefficient, rolling moment coefficient. Therefore, the aerodynamic performance of train on bridge under crosswind is improved.

Vehicles Aerodynamics while Crossing each other on Road Based on Computational Fluid Dynamics

2010 ◽  
Vol 29-32 ◽  
pp. 1344-1349 ◽  
Author(s):  
Zhe Zhang ◽  
Ying Chao Zhang ◽  
Jie Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Simulations ◽  
Aerodynamic Force ◽  
The Other ◽  
Moving Mesh ◽  
Aerodynamic Coefficients ◽  
Paper Report ◽  
Vehicle Aerodynamics ◽  
Simulation Results

When vehicles run on road, they will be overtaken, cross by other vehicles or be impacted by crosswind. The other events of overtaking and in crosswind were investigated more deeply. A few of paper report the state of the research on this problem. Until now there are no any wind tunnel and road tests to study on road vehicle aerodynamics while crossing each other. Some numerical simulations were carried out by adopting technology of sliding interface and moving mesh. The method of numerical simulations was narrated in detail. The transient process of vehicles crossing each other was realized. Then the trends of aerodynamic coefficients changing were obtained from the flow field of simulation results. The quantificational changing of vehicles aerodynamic coefficients was obtained when they cross each other. The vehicles are sedan and coach. The simulation results indicated that the all aerodynamic coefficients of two vehicles changed large. The aerodynamic force was important to the vehicles’ handling stability when they cross each other.

scholarly journals CFD Prediction of Airfoil Drag in Viscous Flow Using the Entropy Generation Method

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Wei Wang ◽  
Jun Wang ◽  
Hui Liu ◽  
Bo-yan Jiang
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Turbulent Flows ◽  
Entropy Generation ◽  
Aerodynamic Force ◽  
Pressure Coefficient ◽  
Generation Rate ◽  
Momentum Balance ◽  
Entropy Generation Rate ◽  
Prediction Approach

A new aerodynamic force of drag prediction approach was developed to compute the airfoil drag via entropy generation rate in the flow field. According to the momentum balance, entropy generation and its relationship to drag were derived for viscous flow. Model equations for the calculation of the local entropy generation in turbulent flows were presented by extending the RANS procedure to the entropy balance equation. The accuracy of algorithm and programs was assessed by simulating the pressure coefficient distribution and dragging coefficient of different airfoils under different Reynolds number at different attack angle. Numerical data shows that the total entropy generation rate in the flow field and the drag coefficient of the airfoil can be related by linear equation, which indicates that the total drag could be resolved into entropy generation based on its physical mechanism of energy loss.

scholarly journals Development and Application of Computational Tool Using Local Surface Inclination Methods for Preliminary Analysis of Hypersonic Vehicles

2020 ◽  
Author(s):  
Tiago Cavalcanti Rolim ◽  
Sheila Cristina Cintra ◽  
Marcela Marques da Cruz Pellegrini
Keyword(s):  
Preliminary Analysis ◽  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Hypersonic Vehicles ◽  
Computational Tool ◽  
Local Surface ◽  
Force Coefficients ◽  
Surface Inclination

This work presents a computational tool for preliminary analysis of hypersonic vehicles, based on local surface inclination methods: the HipeX. This program was developed for reading standard triangulation language (STL) geometry files and calculating pressure coefficient and temperature distributions over vehicle’s surface using the Newtonian, modified Newtonian or tangent-wedge methods. Validations were made with a cylinder and a sphere, where only the Newtonian method was applied, and with experimental data from Apollo capsule at Mach 10, where the Newtonian and the modified Newtonian methods were applied. These validations presented the code capability to read geometries as well as to estimate aerodynamic force coefficients. A preliminary application was to predict the aerodynamic force coefficients of a generic hypersonic vehicle over constant dynamic pressure trajectories of 23,940, 60,000 and 95,760 N/m2 with zero angle of attack. With a fixed dynamic pressure of 60,000 N/m2, this vehicle was tested over several Mach numbers and with angle of attack variation from -10 to 10 deg. Zero angle of attack investigation showed minor changes on the force coefficients with altitude, while the variation of angle of attack produced more pronounced variations on these parameters. Maximum flow temperatures over vehicle’s surface were estimated ranging from 850 to 5,315 K.

Effect of Uvula Length on Airflow and Pressure Oscillation in a Human Pharynx Model

2019 ◽  
Author(s):  
Xuanming Zhao ◽  
Junshi Wang ◽  
Pan Han ◽  
Jinxiang Xi ◽  
Haibo Dong
Keyword(s):  
Aerodynamic Force ◽  
Pressure Oscillation ◽  
Magnetic Resonance Images ◽  
Immersed Boundary ◽  
Pressure Oscillations ◽  
Flow Solver ◽  
Pharyngeal Airway ◽  
Aerodynamic Pressure ◽  
Fast Fourier Transform Analysis ◽  
Original Length

Abstract Unsteady uvula motions and the resultant pressure oscillations within the pharyngeal airway are critical for the pathology of snoring and sleeping apnea. In this paper, an immersed-boundary-method based direct numerical simulation flow solver was adopted to simulate the unsteady flows in an anatomically accurate pharynx model reconstructed from human magnetic resonance images (MRI) with prescribed uvula oscillation and airway obstruction. In order to study the influence of uvula length on the aerodynamics of pharyngeal airflow, simulations were conducted using various uvula models with scaled uvula lengths at 25%, 50%, 75%, and 100% of the original length, respectively. Analyses of vortex dynamics, pressure oscillations, and the aerodynamic force of uvula were conducted. It was found the length of uvula had significant impacts on vortex development as well as aerodynamic pressure/force. Shorter uvula induced weaker pressure oscillations and fewer vortices in the airway. Further fast Fourier transform analysis of pressures from different pressure probes showed higher-order harmonic waves other than the base frequency of uvula motion. This study is expected to bring understanding of snoring and sleep apnea and provide guidance for surgery.

scholarly journals Three-dimensional wing structure attenuates aerodynamic efficiency in flapping fly wings

2020 ◽  
Vol 17 (164) ◽  
pp. 20190804 ◽  
Author(s):  
Thomas Engels ◽  
Henja-Niniane Wehmann ◽  
Fritz-Olaf Lehmann
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Force Production ◽  
Reynolds Numbers ◽  
Dimensional Structure ◽  
Micro Computed Tomography ◽  
Venation Pattern ◽  
Aerodynamic Pressure ◽  
Inertial Loading ◽  
External Forces

The aerial performance of flying insects ultimately depends on how flapping wings interact with the surrounding air. It has previously been suggested that the wing's three-dimensional camber and corrugation help to stiffen the wing against aerodynamic and inertial loading during flapping motion. Their contribution to aerodynamic force production, however, is under debate. Here, we investigated the potential benefit of three-dimensional wing shape in three different-sized species of flies using models of micro-computed tomography-scanned natural wings and models in which we removed either the wing's camber, corrugation, or both properties. Forces and aerodynamic power requirements during root flapping were derived from three-dimensional computational fluid dynamics modelling. Our data show that three-dimensional camber has no benefit for lift production and attenuates Rankine–Froude flight efficiency by up to approximately 12% compared to a flat wing. Moreover, we did not find evidence for lift-enhancing trapped vortices in corrugation valleys at Reynolds numbers between 137 and 1623. We found, however, that in all tested insect species, aerodynamic pressure distribution during flapping is closely aligned to the wing's venation pattern. Altogether, our study strongly supports the assumption that the wing's three-dimensional structure provides mechanical support against external forces rather than improving lift or saving energetic costs associated with active wing flapping.

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