Study of Drag Reduction Devices for a Square Back Vehicle Configuration Using RANS CFD Simulations

2012 ◽  
Author(s):  
Bahram Khalighi ◽  
Kuo-Huey Chen ◽  
Gianluca Iaccarino
Keyword(s):  
Drag Reduction ◽  
Three Dimensional ◽  
Common Element ◽  
Flow Structures ◽  
Vehicle Model ◽  
Cfd Simulations ◽  
Upward Deflection ◽  
Unsteady Rans ◽  
The Common ◽  
Shedding Frequency

The aerodynamic flow around a simplified road vehicle model with and without drag reduction devices is investigated. The simulations are carried out using the unsteady RANS in conjunction with the ν2-f turbulence model. The corresponding experiments are performed in a small wind tunnel which includes pressure and velocity fields measurements. The devices are add-on geometry parts (a box with a cavity and, boat-tail without a cavity) which are attached to the back of the square-back model to improve the pressure recovery and reduce the flow unsteadiness. The results show that the recirculation regions at the base are shortened and weakened and the base pressure is significantly increased by the devices which lead to lower drag coefficients (up to 30% reduction in drag). Also, the results indicate a reduction of the turbulence intensities in the wake as well as a rapid upward deflection of the underbody flow with the devices in place. A suppression or damping of the unsteadiness is the common element of the devices studied. The baseline configuration (square-back) exhibits strong three-dimensional flapping of the wake. The main shedding frequency captured agrees well with the available experimental data. Comparisons with the measurements show that the simulations agree reasonably well with the experiments in terms of drag and the flow structures.

Unsteady Aerodynamic Flow Investigation Around a Simplified Square-Back Road Vehicle With Drag Reduction Devices

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Bahram Khalighi ◽  
Kuo-Huey Chen ◽  
G. Iaccarino
Keyword(s):  
Drag Reduction ◽  
Three Dimensional ◽  
Common Element ◽  
Road Vehicle ◽  
Flow Investigation ◽  
Upward Deflection ◽  
Unsteady Rans ◽  
The Common ◽  
Shedding Frequency ◽  
Coanda Jet

The unsteady flow around a simplified road vehicle model with and without drag reduction devices is investigated. The simulations are carried out using the unsteady RANS in conjunction with the v2-f turbulence model. The corresponding experiments are performed in a small wind tunnel which includes pressure and velocity fields measurements. The devices are add-on geometry parts (a box with a cavity and, boat-tail without a cavity) which are attached to the back of the square-back model to improve the pressure recovery and reduce the flow unsteadiness. The results show that the recirculation regions at the base are shortened and weakened and the base pressure is significantly increased by the devices which lead to lower drag coefficients (up to 30% reduction in drag). Also, the results indicate a reduction of the turbulence intensities in the wake as well as a rapid upward deflection of the underbody flow with the devices in place. A reduction of the unsteadiness is the common element of the devices studied. The baseline configuration (square-back) exhibits strong three-dimensional flapping of the wake. The main shedding frequency captured agrees well with the available experimental data. Comparisons with the measurements show that the simulations agree reasonably well with the experiments in terms of drag and the flow structures. Finally, a blowing system (Coanda jet) is investigated numerically. In this case a drag reduction of up to 50% is realized.

Drag reduction and wear resistance mechanisms of a bionic shovel by discrete element method simulation

SIMULATION ◽  
2018 ◽  
Vol 95 (3) ◽  
pp. 231-239 ◽  
Author(s):  
Rui Zhang ◽  
Dianlei Han ◽  
Yuan He ◽  
Haijin Wan ◽  
Songsong Ma ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Drag Reduction ◽  
High Speed ◽  
Three Dimensional ◽  
Discrete Element ◽  
Resistance Mechanisms ◽  
Fatigue Wear ◽  
Soil Particles ◽  
The Common ◽  
Element Method

The ostrich has a steady and enduring high-speed running ability. Toenails are one key part of ostrich feet and their unique morphology is crucial in insertion into sand and for traction provision. In this study, information of bionic curves was extracted through studying the toenail structure and morphology, and three-dimensional reconstruction of toenails by reverse engineering. Based on the principle of bionic engineering, a bionic shovel was designed by optimizing the traditional shovel. A shovel–soil interaction mechanical model was established via the discrete element method. The insertion into soil processes of the bionic shovel and the common plate were simulated. The dynamic mesoscopic mechanical behaviors of soil particles around the shovel surface, the contact force field, and the velocity field, as well as the forces acting on the shovel surface were analyzed. The bionic shovel outperformed the common plate in insertion. The main reason for drag reduction in the bionic shovel was the inner concave bending surface, along which the soil particles climbed, and the particle movement trend was consistent. Simulations showed stress concentrated at the tip of the shovel, which facilitated the production of fatigue wear. Therefore, the tip needs to be considered firstly during bionic shovel design in the future.

Recent Advances in Wake Dynamics and Active Drag Reduction of Simple Automotive Bodies

2021 ◽  
Author(s):  
Yu Zhou ◽  
Bingfu Zhang
Keyword(s):  
Machine Learning ◽  
Drag Reduction ◽  
Closed Loop ◽  
Three Dimensional ◽  
The Body ◽  
Flow Structures ◽  
Slant Angle ◽  
Reduction Mechanisms ◽  
Reduction Methods ◽  
Active Drag

Abstract This is a compendium of recent progresses in the development of wake dynamics and active drag reduction of three-dimensional simple automotive models, largely focused on the generic Ahmed body. It covers our new understanding of involved instabilities, predominant frequencies, pressure distribution and unsteady flow structures in the high- (12.5° < f < 30°) and low-drag (f > 30°) bodies and the square-back body (f = 0°), where f is the rear slant angle of the body. Various drag reduction methods and their performances are reviewed, including open- and closed-loop controls along with machine-learning control. The involving drag reduction mechanisms, net saving and efficiencies are discussed. Comments are made for the areas that deserve more attention and future investigation.

Various issues relating to computational fluid dynamics simulations of carotid bifurcation flow based on models reconstructed from three-dimensional ultrasound images

2003 ◽  
Vol 217 (5) ◽  
pp. 393-403 ◽  
Author(s):  
A D Augst ◽  
D C Barratt ◽  
A D Hughes ◽  
S A McG Thom ◽  
X Y Xu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Internal Carotid ◽  
Three Dimensional ◽  
Carotid Bifurcation ◽  
External Carotid ◽  
Flow Data ◽  
Cfd Simulations ◽  
The Common

Computational fluid dynamics (CFD) flow simulation techniques have the potential to enhance understanding of how haemodynamic factors are involved in atherosclerosis. Recently, three-dimensional ultrasound has emerged as an alternative to other three-dimensional imaging techniques, such as magnetic resonance angiography (MRA). The method can be used to generate accurate vascular geometry suitable for CFD simulations and can be coupled with Doppler ultrasound to provide physiologically realistic flow boundary conditions. However, there are various ways to utilize the flow data acquired, possibly leading to different results regarding both flow and wall shear stress patterns. A disadvantage of three-dimensional ultrasound for imaging the carotid bifurcation has been established as being the scanning limitation of the jawbone position. This may make artificial extensions of the internal and/or external carotid arteries necessary, which in turn may influence the predicted flow patterns. Flow simulations were carried out for three outflow calculation schemes as well as four geometries with different extensions to the carotid daughter vessels. It was found that variation of flow patterns was more strongly influenced by the outflow conditions than by the extensions of the daughter vessels. Consequently, it is recommended that for future CFD simulations of carotid flow using three-dimensional ultrasound data, the outflow boundary conditions should rely on the most accurate measurement available, and flow data recorded in the common and internal carotid are considered more reliable than data from the external carotid. Even though the extended lengths of the daughter vessels have insignificant effects on the predicted haemodynamic parameters, it would be a safer option to extend the internal carotid by approximately three times the diameter of the common carotid artery.

scholarly journals Performance Curve of a Radial Flow Turbine for an OWC Plant

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1413
Author(s):  
Mina Saad ◽  
Bruno Pereiras ◽  
José González ◽  
Jesús M. Fernández Oro ◽  
Manuel García Díaz
Keyword(s):  
Radial Flow ◽  
Three Dimensional ◽  
Flow Structures ◽  
Performance Curve ◽  
Oscillating Water Column ◽  
Three Dimensional Flow ◽  
Radial Turbine ◽  
Hexahedral Meshes ◽  
Unsteady Rans ◽  
3D Numerical Model

In this article, the performance of a radial flow turbine is determined in the framework of oscillating water column installations (OWC). The studied turbine redesigned and adapted from previous studies to this application, is analyzed in detail using CFD Fluent v16.2 and TurboGrid for mesh preprocessing. In particular, a 3D numerical model with high-quality hexahedral meshes (necessary to analyze the unsteady phenomena in the blade passages of the turbine) has been developed to obtain an enhanced prediction of the flow patterns. The results obtained through a full unsteady RANS resolution of the viscous and three-dimensional flow structures reveal the optimal performance of the radial turbine and confirm the expected improvements introduced during the redesign of the machine.

Iterative algorithm for a split equilibrium problem and fixed problem for finite asymptotically nonexpansive mappings in Hlbert space

Filomat ◽  
2017 ◽  
Vol 31 (5) ◽  
pp. 1423-1434 ◽  
Author(s):  
Sheng Wang ◽  
Min Chen
Keyword(s):  
Equilibrium Problem ◽  
Iterative Algorithm ◽  
Nonexpansive Mappings ◽  
Common Element ◽  
Fixed Point Set ◽  
Split Equilibrium Problem ◽  
Asymptotically Nonexpansive Mappings ◽  
Asymptotically Nonexpansive ◽  
Point Set ◽  
The Common

In this paper, we propose an iterative algorithm for finding the common element of solution set of a split equilibrium problem and common fixed point set of a finite family of asymptotically nonexpansive mappings in Hilbert space. The strong convergence of this algorithm is proved.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

Manipulation of three-dimensional asymmetries of a turbulent wake for drag reduction

2021 ◽  
Vol 912 ◽  
Author(s):  
Yann Haffner ◽  
Thomas Castelain ◽  
Jacques Borée ◽  
Andreas Spohn
Keyword(s):  
Drag Reduction ◽  
Three Dimensional ◽  
Turbulent Wake

Abstract

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