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.

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.

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.

CFD Analysis of Drag Reduction Using External Devices on Pickup Trucks

2010 ◽  
Author(s):  
Feysal A. Adem ◽  
Dongmei Zhou ◽  
Pramod Krishnani
Keyword(s):  
Numerical Simulations ◽  
Inclination Angle ◽  
Cfd Simulation ◽  
Aerodynamic Drag ◽  
Lift Coefficient ◽  
Aerodynamic Drag Coefficient ◽  
Zero Degree ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Yaw Angle

The flows over a pickup truck with add-on devises were studied using computational fluid dynamics (CFD) with the objective of investigating the effect of these add-no devices on the flow structures around the vehicle, aerodynamic drag, and lift coefficient. All numerical simulations were performed using commercial CFD software Fluent [8]. A generic pickup model with extended cab was used as the base model and all the flow simulations were performed at zero degree yaw angle. The pickup configurations used in the present CFD simulation include Aerocap with different rear inclination angle α, Tonneau cover, Rear Roof Garnish, and Tail-plates. Results from numerical simulations indicated that Aerocap with inclination angle α = 12° and a reduced rear width has produced the minimum aerodynamic drag coefficient. It was also shown that the wake region decrease when the rear inclination angle increases.

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 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.

Іmprovement of driving-speed properties improvement of the method for selecting the parameters of the motor-transmission unit car

2021 ◽  
Vol 13 (1) ◽  
pp. 111-117
Author(s):  
Mikhail Podrigalo ◽  
◽  
Volodymyr Krasnokutskyi ◽  
Vitaliy Kashkanov ◽  
Olexander Tkachenko ◽  
...  
Keyword(s):  
Aerodynamic Drag ◽  
Dynamic Properties ◽  
Aerodynamic Characteristics ◽  
Gear Ratio ◽  
Design Stage ◽  
Transmission Unit ◽  
Air Resistance ◽  
Design Speed ◽  
Maximum Design ◽  
Engine Power

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.

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.

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