scholarly journals Aerodynamics of a cycling wheel in crosswind by coaxial volumetric velocimetry

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Constantin Jux ◽  
Andrea Sciacchitano ◽  
Fulvio Scarano
Keyword(s):  
Surface Texture ◽  
Rotational Velocity ◽  
Aerodynamic Resistance ◽  
Aerodynamic Characteristics ◽  
Force Measurements ◽  
Road Cycling ◽  
Stall Angle ◽  
Yaw Angle

The aerodynamic characteristics of a modern road cycling wheel in crosswind are studied through force measurements and 3D velocimetry in TU Delft’s Open Jet Facility. The performance of the 62 mm deep rim is evaluated for two tire profiles, and yaw angles up to 20◦ . All measurements are executed at 12.5 m/s (45 km/h) freestream- and wheel-rotational velocity. The wheel’s rim-tire section in crosswind is found to behave similar to an airfoil at incidence, ultimately resulting in a reduction of the wheel’s aerodynamic resistance with increasing yaw angle magnitude. This trend, also referred to as the sail-effect, is limited by the stall angle of the tire-rim profile. The stall angle is found to be dependent on the tire surface texture and varies between 14◦ and 20◦.

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.

scholarly journals A wind-tunnel case study: Increasing road cycling velocity by adopting an aerodynamically improved sprint position

2019 ◽  
pp. 175433711986696
Author(s):  
Timothy Crouch ◽  
Paolo Menaspà ◽  
Nathan Barry ◽  
Nicholas Brown ◽  
Mark C Thompson ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Time Trial ◽  
Force Measurements ◽  
Sampling Errors ◽  
Repeated Testing ◽  
Road Cycling ◽  
Wind Tunnel Study

The main aim of this study was to evaluate the potential to reduce the aerodynamic drag by studying road sprint cyclists’ positions. A male and a female professional road cyclist participated in this wind-tunnel study. Aerodynamic drag measurements are presented for a total of five out-of-seat sprinting positions for each of the athletes under representative competition conditions. The largest reduction in aerodynamic drag measured for each athlete relative to their standard sprinting positions varied between 17% and 27%. The majority of this reduction in aerodynamic drag could be accounted for by changes in the athlete’s projected frontal area. The largest variation in repeat drag coefficient area measurements of out-of-seat sprint positions was 5%, significantly higher than the typical <0.5% observed for repeated testing of time-trial cycling positions. The majority of variation in repeated drag coefficient area measurements was attributed to reproducibility of position and sampling errors associated with time-averaged force measurements of large fluctuating forces.

scholarly journals About mathematical modeling of aerodynamic characteristics in devices with a leakage of the impact systems of plane-parallel streams on the heat exchange surface

2018 ◽  
Vol 170 ◽  
pp. 03024
Author(s):  
Larisa Haritonova ◽  
Valery Azarov ◽  
Igor Stefanenko
Keyword(s):  
Heat Exchange ◽  
Heat Exchangers ◽  
Aerodynamic Resistance ◽  
Aerodynamic Characteristics ◽  
Plane Parallel ◽  
Heat Exchange Surface ◽  
Parallel Streams ◽  
The Impact ◽  
The Mathematical Model ◽  
Exchange Surface

The article is devoted to the development of the general aerodynamic theory in case of a leakage by the systems of plane-parallel impact jets on the plane heat exchange surface [1-2]. An analytical generalization of data on aerodynamic resistance with the blowout of flat surface by the system of the plane-parallel impact jets was implemented. These data were obtained as a result of the application of mathematical theory of planning an experiment. The equations of regression are the mathematical model of process. Functional dependences between the constructive factors and the regime parameters of these first obtained experimental dependences on aerodynamic resistance in the jet heat exchangers with the leakage of air in the form of the system of plane-parallel jets were established. Results of work can be used in developing of different methods of calculation for various new designs of highly effective heat exchangers or their optimization for various branches.

Wind Tunnel Experimental Study of Wind Turbine Airfoil Aerodynamic Characteristics

2012 ◽  
Vol 260-261 ◽  
pp. 125-129
Author(s):  
Xin Zi Tang ◽  
Xu Zhang ◽  
Rui Tao Peng ◽  
Xiong Wei Liu
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Wind Turbine Blades ◽  
High Lift ◽  
Minimum Drag ◽  
Stall Angle ◽  
High Reynolds

High lift and low drag are desirable for wind turbine blade airfoils. The performance of a high lift airfoil at high Reynolds number (Re) for large wind turbine blades is different from that at low Re number for small wind turbine blades. This paper investigates the performance of a high lift airfoil DU93-W-210 at high Re number in low Re number flows through wind tunnel testing. A series of low speed wind tunnel tests were conducted in a subsonic low turbulence closed return wind tunnel at the Re number from 2×105to 5×105. The results show that the maximum lift, minimum drag and stall angle differ at different Re numbers. Prior to the onset of stall, the lift coefficient increases linearly and the slope of the lift coefficient curve is larger at a higher Re number, the drag coefficient goes up gradually as angle of attack increases for these low Re numbers, meanwhile the stall angle moves from 14° to 12° while the Re number changes from 2×105to 5×105.

scholarly journals Investigations on the Unsteady Aerodynamic Characteristics of a Horizontal-Axis Wind Turbine during Dynamic Yaw Processes

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3124 ◽  
Author(s):  
Xiaodong Wang ◽  
Zhaoliang Ye ◽  
Shun Kang ◽  
Hui Hu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Azimuth Angle ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Structured Grid ◽  
Unsteady Aerodynamic ◽  
Yaw Angle

Wind turbines inevitably experience yawed flows, resulting in fluctuations of the angle of attack (AOA) of airfoils, which can considerably impact the aerodynamic characteristics of the turbine blades. In this paper, a horizontal-axis wind turbine (HAWT) was modeled using a structured grid with multiple blocks. Then, the aerodynamic characteristics of the wind turbine were investigated under static and dynamic yawed conditions using the Unsteady Reynolds Averaged Navier-Stokes (URANS) method. In addition, start-stop yawing rotations at two different velocities were studied. The results suggest that AOA fluctuation under yawing conditions is caused by two separate effects: blade advancing & retreating and upwind & downwind yawing. At a positive yaw angle, the blade advancing & retreating effect causes a maximum AOA at an azimuth angle of 0°. Moreover, the effect is more dominant in inboard airfoils compared to outboard airfoils. The upwind & downwind yawing effect occurs when the wind turbine experiences dynamic yawing motion. The effect increases the AOA when the blade is yawing upwind and vice versa. The phenomena become more dominant with the increase of yawing rate. The torque of the blade in the forward yawing condition is much higher than in backward yawing, owing to the reversal of the yaw velocity.

Experimental validation of numerical decambering approach for flow past a rectangular wing

2020 ◽  
Vol 234 (9) ◽  
pp. 1564-1582 ◽  
Author(s):  
Aritras Roy ◽  
R Vinoth Kumar ◽  
Rinku Mukherjee
Keyword(s):  
Reynolds Numbers ◽  
Numerical Approach ◽  
Aerodynamic Characteristics ◽  
Least Square ◽  
Experimental Result ◽  
Numerical Code ◽  
Induced Drag ◽  
Maximum Coefficient ◽  
Stall Angle ◽  
Significant Addition

Experimental investigation on two rectangular wings with NACA0012 and NACA4415 profiles is performed at different Reynolds numbers to understand their aerodynamic behaviours at a high α regime. In-house developed numerical code VLM3D is validated using this experimental result in predicting the aerodynamic characteristics of a rectangular wing with cambered and symmetrical wing profile. The sectional coefficient of lift ([Formula: see text]) obtained from the numerical approach is used to study the variation in spanwise lift distribution. The lift and moment characteristics obtained from wind tunnel experiments are plotted, and change in the maximum coefficient of lift ([Formula: see text]) and stall angle ( α stall) are studied for both of the wing sections. A significant addition to the novelty of the present experiments is to provide some comparison of the numerical induced drag coefficient, [Formula: see text] with experimentally fitted model coefficients using least square technique. A novel method is used to examine the aerodynamic hysteresis at high angles of attack. The area included in the lift- Re curve loop is a measure of aerodynamic efficiency, and its variation with angle of attack and wing plan forms is studied.

scholarly journals The Influence of Boundary Layer Caused by Riblets on the Aircraft Surface

2020 ◽  
Vol 10 (11) ◽  
pp. 3686
Author(s):  
Hongqing Lv ◽  
Zhenqing Wang ◽  
Jiahao Chen ◽  
Lei Xu
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Flow Direction ◽  
Angle Of Attack ◽  
Suction Side ◽  
Aerodynamic Characteristics ◽  
Wall Surface ◽  
Friction Resistance ◽  
Naca0012 Airfoil ◽  
Stall Angle

Drag reduction of riblets is one of the most important problems in drag reduction of non-smooth surfaces. In the past two decades, the use of riblets arranged along the flow direction to reduce frictional resistance has received considerable attention. In this paper, we study the plates with the triangular concave grooves, triangular protrusion riblets, trapezoidal concave grooves, trapezoidal protrusion riblets, and circular concave grooves. The numerical simulation method is used to calculate five kinds of plates with grooves and riblets under multiple working conditions. The results showed that the plates with grooves and riblets generated vortices inside the grooves, which separated the incoming flow from the wall surface, and by increasing the thickness of the boundary layer, greatly reducing the average velocity gradient of the wall surface, compared with the smooth flat plate, the friction resistance is reduced. But, lateral riblets and grooves cause additional pressure resistance, which is one order of magnitude higher than the friction resistance. Then, the triangular concave grooves are arranged on the suction and pressure sides of the NACA0012 airfoil, respectively. We calculated the aerodynamic parameters of the both airfoils, and the standard NACA0012 airfoil from the −8° attack angle to their respective stall attack angles. The results showed that the NACA0012 airfoil with triangular concave grooves on the suction side reduced the aerodynamic characteristics of the standard NACA0012 at a small angle of attack, but the stall angle of attack of the standard NACA0012 airfoil was improved, because the grooves ensure that some gas can flow normally on the suction side and delay the separation of the boundary layer. The NACA0012 airfoil with triangular concave grooves on the pressure side did not effectively improve the aerodynamic characteristics: lift–drag ratio decreased and stall angle of attack decreased, but it can increase the lift slightly.

Effect of the Air Duct System of a Simplified Vehicle Model on Aerodynamic Performance

2020 ◽  
Vol 17 (2) ◽  
pp. 7985-7995
Author(s):  
A. W. Huluka ◽  
C. H. Kim
Keyword(s):  
Numerical Study ◽  
Aerodynamic Resistance ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Vehicle Model ◽  
Fundamental Study ◽  
Pressure Drag ◽  
Energy Efficiency Improvement ◽  
Simple Body

In this numerical study, ducted Ahmed model is used to study aerodynamic characteristics of ducted models and how ducting would contribute to the energy consumption reduction effort from aerodynamic resistance. Three-dimensional, incompressible, and steady governing equations were solved by commercial software PHOENICS (version 2018) with extended turbulent model proposed by Chen-Kim (1987). The study can be considered as a stepping stone to bring a new approach to design aerodynamically efficient vehicle by ducting target vehicles. To investigate the feasibility of the ducting for aerodynamic energy efficiency improvement, fundamental study has been conducted numerically on a simple body before applying to appropriate vehicle model. It is observed from the study that ducting would reduce over 19% of the pressure drag, to the contrary the increase in skin friction drag is noted although its significance to the total drag is very less compared to pressure drag. Therefore, study of ducting and its effect on aerodynamic performance is expected to contribute to improvement of electric vehicle aerodynamic performance.

Surface Modifications for Improved Maneuverability and Performance of an Aircraft

2011 ◽  
Author(s):  
Deepanshu Srivastav ◽  
K. N. Ponnani
Keyword(s):  
Surface Modifications ◽  
Boundary Layer Separation ◽  
Aerodynamic Characteristics ◽  
Aircraft Wing ◽  
Pressure Drag ◽  
Wing Model ◽  
Study Results ◽  
Stall Angle ◽  
And Performance ◽  
Lift And Drag

The work describes a comparative study of aerodynamic characteristics of an aircraft wing model with and without surface modifications to it. The surface modifications that are considered here are outward dimples on the wing model. In the present study, results of computational fluid dynamics (CFD) analysis are presented showing variance in lift and drag of modified wing models at different angle of attacks. Dimples on the surface aircraft wing model doesn’t affect much the pressure drag since it’s already aerodynamic in shape but it can affect the angle of stall. This project verifies if the dimples that reduce a golf ball’s drag, can also increase an airplane’s critical angle of stall. Dimples delay the boundary layer separation by creating more turbulence over the surface. The airfoil profile considered here is NACA-0018 with uniform cross-section throughout the length of airfoil. Subsonic flows are considered for the study. The CAD model is prepared in CatiaV5 R18 and simulations are carried out in Comsol 3.4 and Comsol 4.0. The overall aim of the study is improved maneuverability and performance of an aircraft. The results justify the increase in the overall lift and reduction in drag of the aircraft, also change of stall angle with different surface modifications on the wing model is observed.

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