scholarly journals Wind-Induced Response of Inclined and Yawed Ice-Accreted Stay Cable Models

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Songyu Cao ◽  
Himan Hojat Jalali ◽  
Elena Dragomirescu
Keyword(s):  
Aerodynamic Drag ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Induced Response ◽  
Ice Accretion ◽  
Stay Cable ◽  
Cfd Simulations ◽  
Stay Cables ◽  
Inclination Angles ◽  
Drag And Lift

During the past decades, wind-induced vibrations of bridge stay cables were reported to occur under various incipient conditions. The ice formation on stay cables is one of these conditions, which causes the ice-accreted stay cables to alter their cross section geometry, thus modifying their aerodynamic characteristics. Wind tunnel tests and several CFD simulations were performed for ice-accreted inclined bridge stay cables with two ice-accretion profiles dimensions, 0.5D and 1D, where D is the diameter of the cable. Wind-induced vibrations were analyzed experimentally for cable models with yaw inclination angles of 0°, 30°, and 60° and vertical inclination angles of 0° and 15°, for Reynolds numbers of up to 4 × 105. The aerodynamic drag and lift coefficients of the cable models and the pressure coefficients were determined from the CFD-LES simulations. The experimental results indicated that the vertical and torsional vibrations of the ice-accreted stay cables increased with the increase of the vertical and yaw angles. Also, higher vertical and torsional vibration amplitudes were measured for the case with larger ice thickness, indicating the effect of the ice accretion profile on the cable wind-induced response.

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.

Numerical Simulations on Aerodynamic Drag of Ground Transportation System (GTS) Model

2006 ◽  
Author(s):  
Manish P. Sitlani ◽  
Kendrick Aung
Keyword(s):  
Experimental Data ◽  
Aerodynamic Drag ◽  
Reynolds Numbers ◽  
Transportation System ◽  
Navier Stokes ◽  
Vehicle Speed ◽  
Cfd Simulations ◽  
Total Drag ◽  
Closing The Gaps ◽  
Reynolds Average

The aerodynamic drag characteristics of a heavy-duty truck with two configurations, a tractor and a single trailer, and a tractor and a tandem-trailer (two trailers), have been studied. The aerodynamic drag of a truck depends on geometry, frontal area and shape, and the speed of the truck. The basic geometry used in the simulation is a 1:8 scale Ground Transportation System (GTS). The effects of vehicle geometry, frontal shape, vehicle speed, and the gap size were investigated and the drag coefficients were computed. The effect of add-on devices such as aerodynamic boat-tail plates at the rear of the trailer on the aerodynamic drag of the truck has also been analyzed. In particular, the effects of the gap between tractor and trailer, and the gap between trailers on the aerodynamic drag of tractor and two trailers configuration were determined. The feasibility of Reynolds-Average Navier-Stokes (RANS) κ-ε model in the prediction of aerodynamic drag at various Reynolds numbers has also been studied. The CFD software from CD-adapco together with an expert tool, es-aero, was used for all the analyses reported in this paper. CFD simulations for tractor and single trailer configuration were performed for various Reynolds numbers. The simulation results were validated with available experimental data and good agreements were found. Validation of numerical results for tractor and single trailer with the experimental data formed the basis for analyzing tractor and double trailer configuration. The tractor and two trailers configuration for different gap sizes between the trailers at various speeds were analyzed. The results showed that closing the gaps and incorporating boat-tails at the rear of the trailer could reduce the drag by as much as 33 percent. Drag coefficient also reduced by 46 percent by introducing smooth frontal fillets in case of tractor and single trailer. The study also emphasizes flow structures around the vehicle that contribute to the total drag.

Aerodynamic Analysis of the Preliminary Design of SURIAKAR 4 Using CFD

2014 ◽  
Vol 629 ◽  
pp. 507-512
Author(s):  
Lai Gwo Sung ◽  
Wan Zaidi Wan Omar ◽  
Ahmad Zafri Zainudin ◽  
S. Mansor ◽  
Tholudin Mat Lazim
Keyword(s):  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Rear Wheel ◽  
Preliminary Design ◽  
Ansys Fluent ◽  
Design Speed ◽  
Drag And Lift ◽  
The Stability ◽  
The Right ◽  
Grid Independence

A four-wheel solar car, the SURIAKAR 4, was designed based on the revised regulations of the Challenger Class World Solar Challenge (2013). It is a four-wheel car with the front and back wheels enclosed in a wind cheating cover. The cockpit is located in such a way that it sits between the front and rear wheel, within the wheel cover on the right side of the car. This paper investigates the aerodynamic characteristics of the car, especially the drag and lift forces, and other forces and moments that determine the stability of the car using CFD package ANSYS Fluent. The model analysis was done with 2.23 million elements after a thorough grid independence study was conducted. The drag coefficient of SURIAKAR 4 is 0.1817. With a frontal area of 0.8934 m2 and at the design speed, the car requires 2132 W of power to overcome this aerodynamic drag. The results also showed that the airflow quality around the car is relatively well-behaved, with only a few turbulent flow points identified. This flow incurs drag penalty and thus have to be modified.

scholarly journals Aerodynamic Analysis of Rear Diffusers for a Passenger Car Using CFD

2020 ◽  
Author(s):  
Bugra Alkan
Keyword(s):  
Drag Reduction ◽  
Driving Forces ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Cfd Simulations ◽  
Fuel Prices ◽  
Computational Fluid Dynamics Cfd ◽  
Reduction Effect ◽  
Cost Efficient ◽  
Conventional Device

Increasing environmental pollution and fuel prices are the driving forces for automotive manufacturers to develop energy efficient vehicles with lower emissions. Improving the aerodynamic characteristics and reducing the aerodynamic drag resistance of a car is the easiest and cost efficient way to handle this problem. A conventional device to improve the aerodynamics that is used on sports and racing cars is a diffuser which improve the pressure recovery on the underbody. In this study, the drag reduction effect of a diffuser has been studied on a sedan car. To understand the effects of the diffuser, computational fluid dynamics (CFD) simulations has been performed. In these simulations, diffusers with different angles were simulated to find most effective drag reduction configuration. Analyses have shown that, it is possible to improve the aerodynamic characteristics by implementing diffusers at the vehicle’s underbody.

scholarly journals Аэродинамический профиль в трансзвуковом потоке газа

2021 ◽  
pp. 20-27
Author(s):  
Юрий Александрович Крашаница ◽  
Дмитрий Юрьевич Жиряков
Keyword(s):  
Numerical Methods ◽  
Transonic Flow ◽  
Center Of Pressure ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Pressure Coefficients ◽  
Standard Atmosphere ◽  
Drag And Lift ◽  
Cae System

The subject of investigation in this article is transonic flow. This is a condition in which local speeds of sound are appears on the wing surface, even at the subsonic speed of the nonturbulent flow. As a result, at a certain speed of the incoming flow, the flow regime around the aerodynamic surface will change sharply, which in turn changes the aerodynamic characteristics. Aerodynamic surfaces of the most transport category airplane experience transonic airflow during flight. The goal of the investigation is to study aerodynamic characteristics using numerical methods. The use of numerical methods in the design of aircraft structures is used more and more often to determine the optimal parameters for given operating conditions. This contributes to obtaining a more optimal and perfect design. In this article, we carried out a numerical analysis of the aerodynamic characteristics of airfoils in the transonic flow case using the CAE system CFD ANSYS. As a result of the research, the distributions of the pressure coefficients over the profile surface were obtained. The nature of the flow is obtained, which is similar to the picture of the pressure coefficients for transonic flow in the published sources of this topic. In the area of the middle of the profile, a shock-wave is observed. As a result, the flow around the airfoil changes, which contributes to a change in aerodynamic characteristics. The behavior of the aerodynamic drag and lift coefficients depending on the speed of the Mach number is considered. Also, the position of the center of pressure was analyzed at various velocities of the nonturbulent flow. The calculation was carried out at the cruising altitude of a medium-range aircraft of 11 km. For the calculations, we used the characteristics of the air temperature, the pressure of a given height from the table of the standard atmosphere.

Application of RNG k-ε Turbulence Model on Numerical Simulation in Vehicle External Flow Field

2012 ◽  
Vol 170-173 ◽  
pp. 3324-3328 ◽  
Author(s):  
Jing Yu Wang ◽  
Xing Jun Hu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Turbulence Model ◽  
Aerodynamic Drag ◽  
Wind Tunnel Test ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
External Flow ◽  
Car Model ◽  
Drag And Lift

The two turbulence models were used to numerically simulate the external flow field around the Ahmed standard car model, and the aerodynamic drag and lift coefficients and aerodynamic characteristics around model were obtained. By comparison between the simulation results and the corresponding wind tunnel test data, the differences of two turbulence models were analyzed. The results indicated the simulation result of RNG k-εturbulence model is more precision, and it is more suitable on numerical simulation in vehicle external flow field. The conclusions provide reference for how to select turbulence model.

scholarly journals Vortex-induced vibrations of a cylinder with tripping wires

2001 ◽  
Vol 448 ◽  
pp. 175-195 ◽  
Author(s):  
F. S. HOVER ◽  
H. TVEDT ◽  
M. S. TRIANTAFYLLOU
Keyword(s):  
Reynolds Numbers ◽  
Induced Response ◽  
Excitation Region ◽  
A Value ◽  
Thin Wires ◽  
Vortex Induced Vibrations ◽  
Drag And Lift ◽  
Lock In ◽  
Phase Angles ◽  
The Impact

Thin wires are attached on the outer surface and parallel to the axis of a smooth circular cylinder in a steady cross-stream, modelling the effect of protrusions and attachments. The impact of the wires on wake properties, and vortex-induced loads and vibration are studied at Reynolds numbers up to 4.6 × 104, with 3.0 × 104 as a focus point. For a stationary cylinder, wires cause significant reductions in drag and lift coefficients, as well as an increase in the Strouhal number to a value around 0.25–0.27. For a cylinder forced to oscillate harmonically, the main observed wire effects are: (a) an earlier onset of frequency lock-in, when compared with the smooth cylinder case; (b) at moderate amplitude/cylinder diameter (A/D) ratios (0.2 and 0.5), changes in the phase of wake velocity and of lift with respect to motion are translated to higher forcing frequencies, and (c) at A/D = 1.0, no excitation region exists; the lift force is always dissipative.The flow-induced response of a flexibly mounted cylinder with attached wires is significantly altered as well, even far away from lock-in. Parameterizing the response using nominal reduced velocity Vrn = U/fnD, we found that frequency lock-in occurs and lift phase angles change through 180° at Vrn [thkap ] 4.9; anemometry in the wake confirms that a mode transition accompanies this premature lock-in. A plateau of constant response is established in the range Vrn = 5.1–6.0, reducing the peak amplitude moderately, and then vibrations are drastically reduced or eliminated above Vrn = 6.0. The vortex-induced vibration response of the cylinder with wires is extremely sensitive to angular bias near the critical value of Vrn = 6.0, and moderately so in the regime of suppressed vibration.

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