Design and Aerodynamic Assessment of Diffuser with Longitudinal Separators for Underbody of Sedan

2012 ◽  
Vol 215-216 ◽  
pp. 1033-1037 ◽  
Author(s):  
Xing Jun Hu ◽  
Rui Zhang ◽  
Jian Ye ◽  
Xu Yan ◽  
Zhi Ming Zhao
Keyword(s):  
Relative Position ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Lift Coefficient ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Coefficient ◽  
Aerodynamic Drag Coefficient ◽  
Diffuser Angle ◽  
High Speed Vehicle

The aerodynamic characteristics have a great influence on the steering stability and the fuel economics of a high speed vehicle. The diffuser located at the aft part of a car underbody is one of the most important aerodynamic add-on devices. The parameters of the diffuser, including the diffuser angle, the number and the relative position of longitudinal separator (LS), the shape of the end plate and etc, will affect the underbody flow and the wake. Here, diffuser with longitudinal separator of different number and relative position was investigated. Numerical simulation was used to study the aerodynamic characteristics of a simplified sedan with different diffuser of longitudinal separator. The study found aerodynamic coefficient of the car changes little when we change the relative position of diffuser's longitudinal separator. Besides, we also found that increasing the number of the diffuser's longitudinal separator will increase the vehicle's aerodynamic drag coefficient and reduce the vehicle's lift coefficient.

Investigation of effects of tire contour on aerodynamic characteristics and its optimization

2021 ◽  
pp. 095440702110586
Author(s):  
Lingxin Zhang ◽  
Haichao Zhou ◽  
Guolin Wang ◽  
Huiyun Li ◽  
Qingyang Wang
Keyword(s):  
Aerodynamic Drag ◽  
Great Influence ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Design Parameters ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Design Variables ◽  
Aerodynamic Drag Coefficient ◽  
Contour Design

Reducing the aerodynamic drag is one of the most important approaches for the development of energy-saving and environment-friendly automobiles. The tire contour has a great influence on the aerodynamic characteristics of automobiles. The aim of this study is to investigate the influence of the tire contour design parameters on the aerodynamic characteristics around a closed wheel, and obtain the optimized tire contour to reduce the automobile aerodynamic drag. A passenger car tire 185/65R14 was selected to conduct the wind tunnel test, and the surface pressure coefficients were used to validate the simulation model established using the detached eddy simulation (DES) model. To decrease tire drag, and taking the upper sidewall height, the tread radii, the tread width, and the transition arc radius of the shoulder as four design variables of contour, a combination of the Latin hypercube experimental design, the Kriging surrogate model, and the adaptive simulated annealing (ASA) algorithm were used to optimize the tire contour design parameters. The changes of flow field around the tire, including the velocity, turbulent kinetic energy, and pressure field were compared and analyzed for further understanding of the drag reduction mechanism. It is found that the aerodynamic drag coefficient of the optimized tire is reduced by 14.5%, and the aerodynamic coefficient drag of the car using the optimized tire is reduced by 7%. The present results are expected to provide useful information for designing new tire structures and improving the aerodynamic performance of the automobile.

scholarly journals Experimental Determination of the Impact of Floats on the Aerodynamic Characteristics of an OSA Model in Symmetric Flow

2021 ◽  
Vol 12 (1) ◽  
pp. 41-58
Author(s):  
Michał FRANT ◽  
Stanisław WRZESIEŃ ◽  
Maciej MAJCHER
Keyword(s):  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Symmetric Flow ◽  
Aerodynamic Drag Coefficient ◽  
The Impact ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This paper presents the results of experimental determination of the impact of floats on the aerodynamic characteristics of an OSA model in symmetric flow. The studies have been performed in the low-speed wind tunnel at the Military University of Technology (MUT, Warsaw, Poland). The aircraft model was examined at the dynamic pressure q = 500 Pa in the following angle of attack range = -2828. The investigations have been performed for an aircraft model under plain configuration with floats and without floats. The influence of elevator and flap inclination on the aerodynamic characteristics of the model has also been analysed. The obtained values of aerodynamic drag coefficient, lift coefficient, pitching moment coefficient and lift-to-drag ratio have been presented in the form of tables and graphs. The studies performed demonstrated that the use of floats causes the increase of aerodynamic drag coefficient CD, maximum lift coefficient CLmax as well as critical angle of attack cr. The decrease of lift-to-drag ratio has also been observed. Its value in the case of the model with floats was up to 20% lower than in the model without floats. The studies also showed that the model equipped with floats had a lower longitudinal static stability margin than the model without floats.

Numerical Simulation to Investigate Influence of Additional Devices on Aerodynamic Drag for Heavy-Duty Commercial Truck

2012 ◽  
Vol 209-211 ◽  
pp. 2089-2093 ◽  
Author(s):  
Xin Yu Wang ◽  
Xing Jun Hu ◽  
Lei Liao ◽  
Teng Fei Li
Keyword(s):  
Numerical Simulation ◽  
Drag Coefficient ◽  
Emission Reduction ◽  
Aerodynamic Drag ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Heavy Duty ◽  
Aerodynamic Drag Coefficient ◽  
Made In China ◽  
Made In

To reduce the aerodynamic drag coefficient of a heavy-duty commercial truck made in China, the aerodynamic characteristics of models with additional devices are researched by adopting numerical simulation and taking a certain made-in-china truck model as research object. The mechanism and the effect of reduction of drag coefficient are analyzed and the optimization of model is gained based on contrast to the drag coefficient of base model. The results indicate that the drag coefficient descends in the most degree after roof fairing of cab is applied and the shape of roof fairing has a great influence on drag. The grille and separator can reduce drag coefficient. The research results can reduce the drag coefficients and provide the theoretical references for energy conservation and emission reduction of heavy-duty trucks

Design and simulation research of the double-spin folding mechanism based on a suspended missile

2021 ◽  
pp. 154851292110231
Author(s):  
ZH Yuan ◽  
SY Guo ◽  
SN Zhang ◽  
JQ Zhao ◽  
WJ Lu ◽  
...  
Keyword(s):  
High Reliability ◽  
Lift Coefficient ◽  
Great Influence ◽  
Reference Value ◽  
Aerodynamic Characteristics ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Simulation Research ◽  
Double Spin ◽  
Locking Mechanism

Based on the suspension of a missile using folding rotary wings and airbags, in order to improve the basic parameters and motion characteristics of the rotor during the unfolding process and analyze the aerodynamic characteristics of the entire device in the suspension state, after proposing a scheme of double-spin mechanism, the main folding and unfolding mechanism, initial driving device, rotating driving device, and locking mechanism were designed, and the simulation research is studied by the Automatic Dynamic Analysis of Mechanical System and Ansys Fluent Fluid Simulation software, respectively. The results show that the rotation rate was controlled at 41.8 mm/s, the various motion parameters are reasonable, and the operation process is relatively smooth, with high reliability. The speed and pressure value at the tip of the rotor are higher and the aerodynamic disturbance is obvious, which has a great influence on the aerodynamic performance. The speed and pressure distribution of the surrounding flow field is stable, the lift provided is 46 N, and the lift coefficient is 0.55, which can ensure the long-time suspension state of the missile. This paper puts forward a valuable design idea and has practical reference value for the research of the suspended missile.

Influence of Engine Cabin Simplification on Aerodynamic Characteristics of Car

2014 ◽  
Vol 1042 ◽  
pp. 188-193 ◽  
Author(s):  
Xing Jun Hu ◽  
Jing Chang
Keyword(s):  
Numerical Simulation ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Thin Plates ◽  
Average Thickness ◽  
Two Dimensional ◽  
Engine Cooling ◽  
Aerodynamic Drag Coefficient ◽  
Simulation Results ◽  
The Impact

In order to analyze the impact of engine cabin parts on aerodynamic characteristics, the related parts are divided into three categories except the engine cooling components: front thin plates (average thickness of 2mm), bottom-suspension and interior panels. The aerodynamic drag coefficient (Cd) were obtained upon the combination schemes consisting of the three types of parts by numerical simulation. Results show that Cd by simulation is closer to the test value gained by the wind tunnel experiment when front thin plates were simplified to the two-dimensional interface with zero thickness. The error is only 5.23%. Meanwhile this scheme reduces grid numbers, thus decreasing the calculating time. As the front thin plates can guide the flow, there is no difference on the Cd values gained from the model with or without bottom-suspension or interior panels when the engine cabin contains the front thin plates; while only both bottom-suspension and interior panels are removed, the Cd value can be reduced when the cabin doesn’t contain the front thin plates.

scholarly journals The “Bag Breakup” Spume Droplet Generation Mechanism at High Winds. Part II: Contribution to Momentum and Enthalpy Transfer

2018 ◽  
Vol 48 (9) ◽  
pp. 2189-2207 ◽  
Author(s):  
Yu. Troitskaya ◽  
O. Druzhinin ◽  
D. Kozlov ◽  
S. Zilitinkevich
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Stable Stratification ◽  
Noticeable Increase ◽  
Wind Speeds ◽  
Breakup Mechanism ◽  
Hurricane Wind ◽  
Exchange Processes ◽  
Aerodynamic Drag Coefficient ◽  
High Winds

AbstractIn Part I of this study, we used high-speed video to identify “bag breakup” fragmentation as the dominant mechanism by which spume droplets are generated at gale-force and hurricane wind speeds. We also constructed a spray generation function (SGF) for the bag-breakup mechanism. The distinctive feature of this new SGF is the presence of giant (~1000 μm) droplets, which may significantly intensify the exchange between the atmosphere and the ocean. In this paper, Part II, we estimate the contribution of the bag-breakup mechanism to the momentum and enthalpy fluxes, which are known to strongly affect the development and maintenance of hurricanes. We consider three contributions to the spray-mediated aerodynamic drag: 1) “bags” as obstacles before fragmentation, 2) acceleration of droplets by the wind in the course of their production, and 3) stable stratification of the marine atmospheric boundary layer due to levitating droplets. Taking into account all of these contributions indicates a peaking dependence of the aerodynamic drag coefficient on the wind speed, which confirms the results of field and laboratory measurements. The contribution of the spray-mediated flux to the ocean-to-atmosphere moist enthalpy is also estimated using the concept of “reentrant spray,” and the equation for the enthalpy flux from a single droplet to the atmosphere is derived from microphysical equations. Our estimates show that a noticeable increase in the enthalpy exchange coefficient at winds exceeding 30–35 m s−1 is due to the enhancement of the exchange processes caused by the presence of giant droplets originating from bag-breakup fragmentation.

scholarly journals Bearing friction effect on cup anemometer performance modelling

2021 ◽  
Vol 2090 (1) ◽  
pp. 012101
Author(s):  
D Alfonso-Corcuera ◽  
S. Pindado ◽  
M Ogueta-Gutiérrez ◽  
A Sanz-Andrés
Keyword(s):  
Rotation Rate ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Friction Torque ◽  
Performance Modelling ◽  
Friction Forces ◽  
Aerodynamic Drag Coefficient ◽  
Yaw Angle ◽  
Cup Anemometer ◽  
Bearing Friction

Abstract In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

scholarly journals Numerical studies on aerodynamics of high-speed railway train subjected to strong crosswind

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988727
Author(s):  
Xu Wang ◽  
Yuanhao Qian ◽  
Zengshun Chen ◽  
Xiao Zhou ◽  
Huaqiang Li ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Width Ratio ◽  
Force Coefficient ◽  
Rolling Moment ◽  
Side Force ◽  
Train Speed ◽  
Yaw Angle

Under the action of strong crosswind, the aerodynamic behavior of a rail vehicle at high speed will be changed significantly, which could directly affect the safe operation of the vehicle. With the help of the shape of train used in China, the aerodynamic characteristics of trains with scale of 1:1 is investigated using computational fluid dynamics numerical simulation method, which consists of the variation of aerodynamics force and moment with wind yaw angle, wind speed, train speed, and nose shape. After an initial validation against Baker’s results from wind tunnel test, the numerical model is then used to investigate the aerodynamic characteristics of the trains. The numerical results indicate that lift coefficient of the M train is slightly higher than TMC1 and TMC2 trains. Regardless of aerodynamics force coefficients, TMC1 reaches the maximum at a yaw angle of 75°. Aerodynamics force coefficient increases with both wind speed and train speed, but the change of which is not linear. Comparing aerodynamic force with different geometric dimensions of train nose, it is shown that height–width ratio is insensitive to side force and rolling moment, but sensitive to lift force from the yaw angle 0°–90°. The side force coefficient, as we most concern, is less than other results, when the length–width ratio is 1 and height–width is 0.87.

A new moving model test method for the measurement of aerodynamic drag coefficient of high-speed trains based on machine vision

2017 ◽  
Vol 232 (5) ◽  
pp. 1425-1436 ◽  
Author(s):  
Zhiwei Li ◽  
Mingzhi Yang ◽  
Sha Huang ◽  
Dan Zhou
Keyword(s):  
Machine Vision ◽  
Drag Coefficient ◽  
Model Test ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Full Scale ◽  
Test Method ◽  
Test Accuracy ◽  
Friction Resistance ◽  
Aerodynamic Drag Coefficient

A moving model test method has been proposed to measure the aerodynamic drag coefficient of a high-speed train based on machine vision technology. The total resistance can be expressed as the track friction resistance and the aerodynamic drag according to Davis equation. Cameras are set on one side of the track to capture the pictures of the train, from which the line marks on the side surface of the train are extracted and analyzed to calculate the speed and acceleration of the train. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through multiple tests at different train speeds. Comparisons are carried out with the full-scale coasting test, wind tunnel test, and numerical simulation; good agreement is obtained between the moving model test and the full-scale field coasting test with difference within 1.51%, which verifies that the method proposed in this paper is feasible and reliable. This method can accurately simulate the relative movement between the train, air, and ground. The non-contact measurement characteristic will increase the test accuracy, providing a new experimental method for the aerodynamic measurement.

Experimental Studies on Aerodynamic Characteristics of Pantograph System According to the Pantograph Cover Configurations for High Speed Train

2011 ◽  
Author(s):  
Yeongbin Lee ◽  
Minho Kwak ◽  
Kyu Hong Kim ◽  
Dong-Ho Lee
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Experimental Studies ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Experimental Models ◽  
High Speed Train ◽  
Drag And Lift

In this study, the aerodynamic characteristics of pantograph system according to the pantograph cover configurations for high speed train were investigated by wind tunnel test. Wind tunnel tests were conducted in the velocity range of 20∼70m/s with scaled experimental pantograph models. The experimental models were 1/4 scaled simplified pantograph system which consists of a double upper arm and a single lower arm with a square cylinder shaped panhead. The experimental model of the pantograph cover is also 1/4 scaled and were made as 4 different configurations. It is laid on the ground plate which modeled on the real roof shape of the Korean high speed train. Using a load cell, the aerodynamic force such as a lift and a drag which were acting on pantograph system were measured and the aerodynamic effects according to the various configurations of pantograph covers were investigated. In addition, the total pressure distributions of the wake regions behind the panhead of the pantograph system were measured to investigate the variations of flow pattern. From the experimental test results, we checked that the flow patterns and the aerodynamic characteristics around the pantograph systems are varied as the pantograph cover configurations. In addition, it is also found that pantograph cover induced to decrease the aerodynamic drag and lift forces. Finally, we proposed the aerodynamic improvement of pantograph cover and pantograph system for high speed train.

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