scholarly journals Mathematical Modeling of Drag Coefficient Reduction in Circular Cylinder Using Two Passive Controls at Re = 1000

2018 ◽  
Vol 23 (1) ◽  
pp. 2
Author(s):  
Chairul Imron ◽  
Lutfi Mardianto ◽  
Basuki Widodo ◽  
Tri Yuwono
Keyword(s):  
Mathematical Modeling ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Coefficient Reduction

Aerodynamics of Cyclist Posture, Bicycle and Helmet Characteristics in Time Trial Stage

2012 ◽  
Vol 28 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Vincent Chabroux ◽  
Caroline Barelle ◽  
Daniel Favier
Keyword(s):  
Statistical Analysis ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Drag Force ◽  
Time Trial ◽  
Frontal Area ◽  
Significant Gain ◽  
Upper Limbs ◽  
Force Coefficient ◽  
Coefficient Reduction

The present work is focused on the aerodynamic study of different parameters, including both the posture of a cyclist’s upper limbs and the saddle position, in time trial (TT) stages. The aerodynamic influence of a TT helmet large visor is also quantified as a function of the helmet inclination. Experiments conducted in a wind tunnel on nine professional cyclists provided drag force and frontal area measurements to determine the drag force coefficient. Data statistical analysis clearly shows that the hands positioning on shifters and the elbows joined together are significantly reducing the cyclist drag force. Concerning the saddle position, the drag force is shown to be significantly increased (about 3%) when the saddle is raised. The usual helmet inclination appears to be the inclination value minimizing the drag force. Moreover, the addition of a large visor on the helmet is shown to provide a drag coefficient reduction as a function of the helmet inclination. Present results indicate that variations in the TT cyclist posture, the saddle position and the helmet visor can produce a significant gain in time (up to 2.2%) during stages.

Laminar Forced Convection From a Circular Cylinder Placed in a Micropolar Fluid

2006 ◽  
Vol 129 (3) ◽  
pp. 256-264 ◽  
Author(s):  
F. M. Mahfouz
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Prandtl Number ◽  
Drag Coefficient ◽  
Forced Convection ◽  
Vortex Shedding ◽  
Micropolar Fluid ◽  
Clear Trend ◽  
Thermal Fields ◽  
Laminar Forced Convection

In this paper laminar forced convection associated with the cross-flow of micropolar fluid over a horizontal heated circular cylinder is investigated. The conservation equations of mass, linear momentum, angular momentum and energy are solved to give the details of flow and thermal fields. The flow and thermal fields are mainly influenced by Reynolds number, Prandtl number and material parameters of micropolar fluid. The Reynolds number is considered up to 200 while the Prandtl number is fixed at 0.7. The dimensionless vortex viscosity is the only material parameter considered in this study and is selected in the range from 0 to 5. The study has shown that generally the mean heat transfer decreases as the vortex viscosity increases. The results have also shown that both the natural frequency of vortex shedding and the amplitude of oscillating lift force experience clear reduction as the vortex viscosity increases. Moreover, the study showed that there is a threshold value for vortex viscosity above which the flow over the cylinder never responds to perturbation and stays symmetric without vortex shedding. Regarding drag coefficient, the results have revealed that within the selected range of controlling parameters the drag coefficient does not show a clear trend as the vortex viscosity increases.

An Experimental Investigation for Flow Past a Circular Cylinder With Rectangular Strips

2002 ◽  
Author(s):  
Chuan He ◽  
Tianyu Long ◽  
Mingdao Xin ◽  
Benjamin T. F. Chung
Keyword(s):  
Experimental Investigation ◽  
Fluid Flow ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Experimental Results ◽  
Sharp Edge ◽  
Flow Past ◽  
Rectangular Strips

This paper reports an experimental investigation for fluid flow past a circular cylinder with two small rectangular strips and single sharp-edge strips on its surface. The experimental results reflected that different arrangements or dimensions of the strips produced significantly different effects on the flow. The forward step caused a stronger disturbance with a small increase in drag. The backward step arrangement softened the disturbance but reduced the drag coefficient by 33%.

scholarly journals Influence of Inflow Turbulence on the Flow Characteristics around a Circular Cylinder

2019 ◽  
Vol 9 (17) ◽  
pp. 3595 ◽  
Author(s):  
Jianfeng Yao ◽  
Wenjuan Lou ◽  
Guohui Shen ◽  
Yong Guo ◽  
Yuelong Xing
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Turbulent Flow ◽  
Drag Coefficient ◽  
Turbulence Intensity ◽  
Lift Coefficient ◽  
Wind Pressure ◽  
Separation Point ◽  
Critical Regime ◽  
Smooth Flow

To study the influence of turbulence on the wind pressure and aerodynamic behavior of smooth circular cylinders, wind tunnel tests of a circular cylinder based on wind pressure testing were conducted for different wind speeds and turbulent flows. The tests obtained the characteristic parameters of mean wind pressure coefficient distribution, drag coefficient, lift coefficient and correlation of wind pressure for different turbulence intensities and of Reynolds numbers. These results were also compared with those obtained by previous researchers. The results show that the minimum drag coefficient in the turbulent flow is basically constant at approximate 0.4 and is not affected by the turbulence intensity. When the Reynolds number is in the critical regime, the lift coefficient increased sharply to 0.76 in the smooth flow, indicating that flow separation has an asymmetry; however, the asymmetry does not appear in the turbulent flow. Drag coefficient decreases sharply at a lower critical Reynolds number in the turbulent flow than in the smooth flow. In the smooth flow, the separation point is about 80° in the subcritical regime; it suddenly moves backwards in the critical regime and remains almost unchanged at about 140° in the supercritical regime. However, the angular position of the separation point will always be about 140° for turbulent flow for the Reynolds number in these three regimes. Turbulence intensity and Reynolds number have a significant effect on the correlation of wind pressures around the circular cylinder. Turbulence will weaken the positive correlation of the same side and also reduce the negative correlation between the two sides of the circular cylinder.

scholarly journals Similarities of Flow and Heat Transfer around a Circular Cylinder

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 658
Author(s):  
Hao Ma ◽  
Zhipeng Duan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Heat And Mass Transfer ◽  
General Procedure ◽  
Fluid Flows ◽  
Flow And Heat Transfer ◽  
Transfer Behavior ◽  
Entire Flow

Modeling fluid flows is a general procedure to handle engineering problems. Here we present a systematic study of the flow and heat transfer around a circular cylinder by introducing a new representative appropriate drag coefficient concept. We demonstrate that the new modified drag coefficient may be a preferable dimensionless parameter to describe more appropriately the fluid flow physical behavior. A break in symmetry in the global structure of the entire flow field increases the difficulty of predicting heat and mass transfer behavior. A general simple drag model with high accuracy is further developed over the entire range of Reynolds numbers met in practice. In addition, we observe that there may exist an inherent relation between the drag and heat and mass transfer. A simple analogy model is established to predict heat transfer behavior from the cylinder drag data. This finding provides great insight into the underlying physical mechanism.

Flow Characteristics of a Bluff Body Cut From a Circular Cylinder

1997 ◽  
Vol 119 (2) ◽  
pp. 453-454 ◽  
Author(s):  
S. Aiba ◽  
H. Watanabe
Keyword(s):  
Circular Cylinder ◽  
Drag Coefficient ◽  
Flow Velocity ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Angular Position ◽  
Flow Characteristics ◽  
Uniform Flow ◽  
Base Pressure ◽  
Singular Flow

This is a report on an investigation of the flow characteristics of a bluff body cut from a circular cylinder. The volume removed from the cylinder is equal to d/2(1 − cos θs), where d and θs are the diameter and the angular position (in the case of a circular cylinder, θs, = 0 deg), respectively. θs, ranged from 0 deg to 72.5 deg and Re (based on d and the upstream uniform flow velocity U∞) from 2.0 × 104 to 3.5 × 104. It is found that a singular flow around the cylinder occurs at around θs = 53 deg when Re > 2.5 × 104, and the base pressure coefficient (−Cpb,) and the drag coefficient CD take small values compared with those for otherθs.

Underbody aerodynamics: Drag coefficient reduction in road vehicles

2018 ◽  
Author(s):  
R. Heidemann Jr ◽  
A. F. A. Rodrigues ◽  
A. Bohrer ◽  
C. L. Gertz ◽  
A. Cervieri
Keyword(s):  
Drag Coefficient ◽  
Road Vehicles ◽  
Coefficient Reduction

Drag of a Circular Cylinder with Vortex Generators

1962 ◽  
Vol 66 (619) ◽  
pp. 456-457 ◽  
Author(s):  
P. N. Joubert ◽  
E. R. Hoffman
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Laminar Separation

The following is a report of preliminary tests to determine the effect of vortex generators on the drag of a circular cylinder. It was thought that with suitable placement of the vortex generators on the cylinder, the laminar separation of the boundary layer at subcritical Reynolds numbers might be delayed, and a reduction in drag coefficient obtained.

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