Numerical study on aerodynamic drag by variation of rear side slope of sedan cars

Large amplitude cable vibrations are difficult to predict using linear theory due to the presence of sag in the suspended profile. A numerical study was therefore undertaken to investigate the dynamic behaviour of inclined cables excited by imposed displacements. To model the nonlinear nature of cable response, a time domain finite element approach was adopted using nonlinear catenary cable elements. Two types of horizontal displacement patterns were enforced at the upper end of the guy. In the first phase of the study, harmonic displacement histories with a wide range of forcing frequencies were considered. In the second phase, random enforced displacements were used to simulate the motion of a guyed mast in gusty winds. The influence of aerodynamic drag and damping forces was investigated by performing analyses under still air, steady wind, and turbulent wind conditions. It was found that nonlinear coupling of related harmonic response components was significant at certain critical frequencies, particular when the excitation was harmonic and acted in the plane of the guy. Positive aerodynamic damping was shown to effectively suppress resonant and nonlinear coupling response.Key words: cables, structural dynamics, wind loading, finite element method, nonlinear analysis, guyed towers.

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Numerical study on reducing aerodynamic drag and noise of circular cylinders with non-uniform porous coatings

Aerospace Science and Technology ◽

10.1016/j.ast.2020.106308 ◽

2020 ◽

Vol 107 ◽

pp. 106308

Author(s):

Pikai Zhang ◽

Yu Liu ◽

Zhiyong Li ◽

Hanru Liu ◽

Yannian Yang

Keyword(s):

Aerodynamic Drag ◽

Numerical Study ◽

Circular Cylinders ◽

Porous Coatings

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Interaction between an aerodynamically driven, wall-bound drop and a single groove

The European Physical Journal Special Topics ◽

10.1140/epjst/e2020-900269-5 ◽

2020 ◽

Vol 229 (10) ◽

pp. 1757-1769 ◽

Cited By ~ 1

Author(s):

Patrick M. Seiler ◽

Ilia V. Roisman ◽

Cameron Tropea

Keyword(s):

Channel Flow ◽

Drag Force ◽

High Speed ◽

Adhesion Force ◽

Aerodynamic Drag ◽

Rear Side ◽

Threshold Condition ◽

High Speed Video ◽

Gravity Forces ◽

Typical Time

Abstract The interaction between an air-driven, wall-bound drop and a groove in the wall of a channel flow has been investigated experimentally using a high-speed video system. Three major outcomes of drop interaction with the groove are observed: (i) the drop passes over the groove, (ii) the drop is immediately fully captured in the groove or (iii) the drop is captured after first wetting the rear side of the groove. The mechanisms leading to these different outcomes are governed by the aerodynamic drag force, by inertial and gravity forces, and by the adhesion force associated with the substrate wettability. A threshold condition for drop capture is developed, based on the ratio of the typical time for drop passage over the groove to the time for the drop to be sucked into the groove. It has been shown that the probability for drop capture increases for higher Bond numbers.

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An Unsteady Analysis on Thermal Stratification in the SCS Piping Branched Off the RCS Piping

Problems Involving Thermal Hydraulics, Liquid Sloshing, and Extreme Loads on Structures ◽

10.1115/pvp2003-1815 ◽

2003 ◽

Author(s):

Kwang-Chu Kim ◽

Man-Heung Park ◽

Hag-Ki Youm ◽

Sun-Ki Lee ◽

Tae-Ryong Kim ◽

...

Keyword(s):

Temperature Difference ◽

Thermal Stratification ◽

Nuclear Power ◽

Cooling System ◽

Numerical Study ◽

Outer Wall ◽

Maximum Temperature ◽

Rear Side ◽

Maximum Temperature Difference ◽

Starting Point

A numerical study is performed to estimate on an unsteady thermal stratification phenomenon in the Shutdown Cooling System (SCS) piping branched off the Reactor Coolant System (RCS) piping of Nuclear Power Plant. In the results, turbulent penetration reaches to the 1st isolation valve. At 500sec, the maximum temperature difference between top and bottom inner wall in piping is observed at the starting point of horizontal piping passing elbow. The temperature of coolant in the rear side of the 1st isolation valve disk is very slowly increased and the inflection point in temperature difference curve for time is observed at 2700sec. At the beginning of turbulent penetration from RCS piping, the fast inflow generates the higher temperature for the inner wall than the outer wall in the SCS piping. In the case the hot-leg injection piping and the drain piping are connected to the SCS piping, the effect of thermal stratification in the SCS piping is decreased due to an increase of heat loss compared with no connection case. The hot-leg injection piping affected by turbulent penetration from the SCS piping has a severe temperature difference that exceeds criterion temperature stated in reference. But the drain piping located in the rear compared with the hot-leg injection piping shows a tiny temperature difference. In a viewpoint of designer, for the purpose of decreasing the thermal stratification effect, it is necessary to increase the length of vertical piping in the SCS piping, and to move the position of the hot-leg injection piping backward.

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Numerical Study of the Generic Sports Utility Vehicle Design with a Drag Reduction Add-On Device

Journal of Computational Engineering ◽

10.1155/2014/785294 ◽

2014 ◽

Vol 2014 ◽

pp. 1-17 ◽

Cited By ~ 1

Author(s):

Shubham Singh ◽

M. Zunaid ◽

Naushad Ahmad Ansari ◽

Shikha Bahirani ◽

Sumit Dhall ◽

...

Keyword(s):

Drag Reduction ◽

Drag Coefficient ◽

Aerodynamic Drag ◽

Numerical Study ◽

Fuel Efficiency ◽

Ansys Fluent ◽

Mean Pressure ◽

Aerodynamic Drag Coefficient ◽

Total Base ◽

Aerodynamic Parameters

CFD simulations using ANSYS FLUENT 6.3.26 have been performed on a generic SUV design and the settings are validated using the experimental results investigated by Khalighi. Moreover, an add-on inspired by the concept presented by Englar at GTRI for drag reduction has been designed and added to the generic SUV design. CFD results of add-on model and the basic SUV model have been compared for a number of aerodynamic parameters. Also drag coefficient, drag force, mean surface pressure, mean velocities, and Cp values at different locations in the wake have been compared for both models. The main objective of the study is to present a new add-on device which may be used on SUVs for increasing the fuel efficiency of the vehicle. Mean pressure results show an increase in the total base pressure on the SUV after using the device. An overall reduction of 8% in the aerodynamic drag coefficient on the add-on SUV has been investigated analytically in this study.

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Drag-based aerodynamic braking system for the Hyperloop: a numerical study

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2019-0120 ◽

2020 ◽

pp. 1-10

Author(s):

Mohammed Raihan Uddin ◽

Tahsin Sejat Saniat ◽

Sayedus Salehin ◽

Md. Hamidur Rahman

Keyword(s):

High Speed ◽

Aerodynamic Drag ◽

Numerical Study ◽

Detailed Comparison ◽

Sustainable Transportation ◽

Transport Infrastructure ◽

Braking System ◽

Passenger Safety ◽

Aerodynamic Brake ◽

High Mach

The Hyperloop promises to revolutionize the transport infrastructure of the 21st century by reducing travel time and allowing people to reach transonic speed on land. It carries with it the hope of a sustainable transportation system during an era of global energy crisis. Overall passenger safety in a high-speed pod necessitates a reliable braking system. This paper introduces the possibility of utilizing aerodynamic drag in the Hyperloop, anticipated to operate at high Mach and low Reynolds flow regime, to attenuate the speed of the pod. Numerical analysis was conducted to investigate the effect of incorporating an aerodynamic brake at different pod velocities (100, 135, and 150 m/s) and deployment angles (30°, 45°, 60°, and 90°). A detailed comparison between the proposed aerodynamic braking system (AeBS) and existing braking systems for the Hyperloop has been presented in this paper. The results demonstrate an increase in drag value of the pod by 3.4 times using a single 0.15 m2 brake plate. When the brake plate was fully deployed at a pod velocity in excess of 112 m/s, the aerodynamic drag-based braking systems was shown to be more effective than the contemporary eddy current braking system.

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