Aerodynamic Analysis of Pickup Truck

2011 ◽  
Vol 201-203 ◽  
pp. 1296-1299
Author(s):  
Xiao Ni Qi ◽  
Jian Meng ◽  
Yong Qi Liu
Keyword(s):  
Reverse Flow ◽  
Symmetry Plane ◽  
Cross Flow ◽  
Flow Region ◽  
Flow Fields ◽  
Mean Flow ◽  
Near Wake ◽  
Recirculation Flow ◽  
Pickup Truck ◽  
The Cross

The present study focuses on the aerodynamics of pickup trucks. The CFD software FLUENT was used to simulate flow field around a pickup truck in this paper. Numerical simulation was taken on a 1/5th pickup truck model. The surface pressure distribution, the wake velocity distribution of the special profiles and the flow structures were obtained. The research indicted that there was a recirculation flow region over the bed for pickup truck. The cab shear layer did not interact directly with the tailgate, flowing above the top of the tailgate. There was a downwash flow in the symmetry plane behind the tailgate with no reverse flow region in the symmetry plane, and the formation of two smaller recirculation flow regions was on both sides of the symmetry plane. Mean flow fields in the near wake of the cab showed a weak pair of counter-rotating vortices behind the cab. In the cross-flow planes behind the tailgate, the mean flow fields show strong counter-rotating vortices behind the tailgate. Instantaneous flow fields in the cross-flow planes of the pickup truck near wake showed compact vortex structures located randomly in space.

PIV Measurements of the Cross-Flow Velocity Field in the Near Wake of a Generic Pickup Truck

2006 ◽  
Author(s):  
Bahram Khalighi
Keyword(s):  
Velocity Field ◽  
Symmetry Plane ◽  
Cross Flow ◽  
Velocity Data ◽  
Near Wake ◽  
Mean Velocity ◽  
Piv Measurements ◽  
Pickup Truck ◽  
The Mean ◽  
The Cross

The cross-flow field (flow in planes normal to the direction of motion) in the near wake of a generic pickup truck is investigated experimentally using Particle Image Velocimetry (PIV). The PIV measurements of the velocity field normal to the free-stream direction are carried out at four stream-wise locations behind the cab and the tailgate. The PIV data are processed to obtain the instantaneous velocity field, the mean and the turbulence properties of the flow. The instantaneous results in the near wake of the cab show various vortical structures. The mean velocity data shows that the flow moves from the sides toward the center of the bed near the tailgate. The velocity data in the near wake of the tailgate shows a pair of counter-rotating vortices that induces a downwash velocity field at the symmetry plane. This downwash promotes an attached flow behind the tailgate, thus generating a pressure recovery which leads to reductions in the total drag.

Three-Dimensional Forced Convection in Plane Symmetric Sudden Expansion

2004 ◽  
Vol 126 (5) ◽  
pp. 836-839 ◽  
Author(s):  
J. H. Nie and ◽  
B. F. Armaly
Keyword(s):  
Nusselt Number ◽  
Forced Convection ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
Outer Edge ◽  
Sudden Expansion ◽  
Recirculation Flow ◽  
Plane Symmetric ◽  
Laminar Forced Convection

Simulations of three-dimensional laminar forced convection in a plane symmetric sudden expansion are presented for Reynolds numbers where the flow is steady and symmetric. A swirling “jetlike” flow develops near the sidewalls in the separating shear layer, and its impingement on the stepped wall is responsible for the maximum that develops in the Nusselt number adjacent to the sidewalls and for the reverse flow that develops in that region. The maximum Nusselt number on the stepped wall is located inside the primary recirculation flow region and its location does not coincide with the jetlike flow impingement region. The results reveal that the location where the streamwise component of wall shear stress is zero on the stepped walls does not coincide with the outer edge of the primary recirculation flow region near the sidewalls.

Laminar Mixed Convection Adjacent to Three-Dimensional Backward-Facing Step

2001 ◽  
Vol 124 (1) ◽  
pp. 209-213 ◽  
Author(s):  
A. Li and ◽  
B. F. Armaly
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
The Other ◽  
Backward Facing Step ◽  
Number Range ◽  
Grashof Number ◽  
Recirculation Flow

Simulations of three-dimensional laminar buoyancy-assisting mixed convection adjacent to a backward-facing step in a vertical rectangular duct are presented to demonstrate the influence of Grashof number on the distributions of the Nusselt number, and the reverse flow regions that develop adjacent to the duct’s walls. The Reynolds number, and duct’s geometry are kept constant: heat flux at the wall downstream from the step is kept uniform but its magnitude varied to cover a Grashof number range of 0–4000; all the other walls in the duct are kept at adiabatic condition; and the flow, upstream of the step, is treated as fully developed and isothermal. Increasing the Grashof number results in increasing the Nusselt number; the size of the secondary recirculation flow region adjacent to the stepped wall; the size of the reverse flow region adjacent to the sidewall and the flat wall; and the spanwise flow from the sidewall toward the center of the duct. On the other hand, the size of the primary recirculation flow region adjacent to the stepped wall decreases and detaches partially from the heated stepped wall as the Grashof number increases. Details are presented and discussed.

Influence of Oscillating Boundary Layer Suction on Aerodynamic Performance in Highly-Loaded Compressor Cascades

2018 ◽  
Author(s):  
Xu Hao ◽  
Liu Bao ◽  
Cai Le ◽  
Zhou Xun ◽  
Wang Songtao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vortex Shedding ◽  
Large Scale ◽  
Reverse Flow ◽  
Separation Bubble ◽  
Flow Region ◽  
Flow Fields ◽  
Separation Flow ◽  
Oscillating Boundary ◽  
Pod Analysis

Vortex structures of the separation flow fields in compressor cascades controlled by the boundary layer oscillating suction (BLOS) are numerically investigated. The proper orthogonal decomposition (POD) method is adopted to present the variation of characteristics owned by large-scale vortices. It is found that unsteady perturbation re-organizes the aspirated flow fields and, if in a proper situation, reduces the loss furthermore. Through POD analysis, variations of vortical structures are described. The results turn out that the periodic perturbation leads to a vortex shedding process with the same frequency as the excitation. The reason of loss reduction could be summarized by actuated vortices enhancing the momentum of the stagnated fluid in the reverse flow region as well as decreasing the frequencies of vortex shedding. Finally, 3-D numerical results turn out that the oscillation can transform the stable corner separation bubble to vortex rings shedding downstream and hence improve cascade performance.

Flow characteristics of a pickup truck with regard to the bed geometry variation

2010 ◽  
Vol 224 (7) ◽  
pp. 881-891 ◽  
Author(s):  
J Ha ◽  
S Jeong ◽  
S Obayashi
Keyword(s):  
Drag Coefficient ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Wind Tunnel Experiments ◽  
Significant Interaction Effect ◽  
Recirculation Flow ◽  
Pickup Truck ◽  
Bed Height ◽  
Pressure Area ◽  
Main Factors

The bed is one of the most important parts of a pickup truck for aerodynamic performance. The flow characteristics of a pickup truck were examined in a series of wind tunnel experiments and numerical simulations with regard to the bed geometry variation, the bed length, and the bed height. The drag coefficient was changed in accordance with the bed geometry variation so that the bed length and bed height had a significant interaction effect. The main factors that affected the drag coefficient were the bed recirculation flow over the bed and the reverse flow in the wake. The drag coefficient increased when the downwash of the bed flow was not recirculated into the bed but was attached to the upper part of the tailgate. The larger reverse flow in the wake and the enlarged adverse pressure area inside the bed influenced the drag increment when there was no attachment of the bed flow. For a low-drag pickup truck, the bed should be designed such that the bed flow is not attached to the tailgate and the reverse flow in the wake is small.

Turbulent Flow Over a NACA 4412 Airfoil at Angle of Attack 15 Degree

2003 ◽  
Author(s):  
O. O. Badran ◽  
H. H. Bruun
Keyword(s):  
Reverse Flow ◽  
Separation Bubble ◽  
Angle Of Attack ◽  
Flow Region ◽  
Shear Stresses ◽  
Separation Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Trailing Edge ◽  
Short Period

This paper presents the measured mean flow and Reynolds stresses results, obtained on the center-line plane of the airfoil, covering the boundary layers over the upper surface, the potential flow region and the wake downstream of the trailing edge, at αa = 15°. The flying X-hot-wire probe was used to measure the U and V components of the flow field over the airfoil. An improved understanding of the physical characteristics of separation on the airfoil sections and in the region of the trailing edge is of direct value for the improvement of high lift wings for aircraft. From the study of the separation flow at angle of attack αa = 15°, the following can be concluded: (1) An intermittent reverse flow region occurred near the trailing edge of the airfoil. A separation bubble occurred for a short period of time and was then swept away with the stream wise flow. (2) The angle of attack αa = 15° corresponds to the position of maximum lift for a NACA 4412 airfoil section. (3) It is found that values of the Reynolds normal and shear stresses move away from the surface with downstream distance, and (4) In the wake region, relatively large values of Reynolds stresses occurred, which were related to the vertical oscillation in the lower wake.

Flow Characteristics Inside Circular Injection Holes Normally Oriented to a Crossflow: Part I — Flow Visualizations and Flow Data in the Symmetry Plane

2000 ◽  
Vol 123 (2) ◽  
pp. 266-273 ◽  
Author(s):  
Sang Woo Lee ◽  
Sang Won Park ◽  
Joon Sik Lee
Keyword(s):  
Separation Bubble ◽  
Symmetry Plane ◽  
Flow Region ◽  
Windward Side ◽  
Leeward Side ◽  
Flow Data ◽  
Mean Flow ◽  
Injection Hole ◽  
Potential Core ◽  
Flow Visualizations

Experimental results are presented that describe flow behavior inside circular injection holes with a sharp square-edged inlet. Oil-film flow visualizations and mean flow data are obtained in the flow symmetry plane of injection holes that are normally oriented to a crossflow. Additional visualizations inside inclined holes are also performed for inclination angles of 30 and 60 deg. Data are presented for three different length-to-diameter ratios: L/D=0.5, 1.0, and 2.0. The blowing ratio is fixed at M=2.0 in the flow visualizations and takes the values M=0.5, 1.0, and 2.0 in the flow measurements. The normal-injection flow visualization in the case of L/D=2.0 clearly demonstrates the existence of four distinct near-wall flow regions: an inlet separation region, a reattachment region, a developing region, and a near-exit flow region. When L/D=1.0 and 2.0, an inlet separation bubble is apparent with a clear imprint of recirculating flow traces, especially on the windward side, even though it is not so well organized on the opposite side. For a short hole such as L/D=0.5, however, the separation bubble with flow recirculation seems to be suppressed by the crossflow. Due to the presence of the inlet separation bubble, actual flow passage is in the form of a converging–diverging channel, regardless of the L/D values. In general, the crossflow stabilizes the inside flow on the leeward side, meanwhile destabilizes it on the windward side. On the contrary, the inclination of the injection hole in the leeward direction of the crossflow stabilizes the flow near the windward wall but destabilizes it near the leeward wall. Relatively short holes such as L/D=0.5 and 1.0 do not allow the boundary-layer development on the wall. Particularly in the case of L/D=0.5, a direct interference is observed between the complicated inlet and exit flows. The inlet flow, however, seems to be isolated from the exit flow for a long hole such as L/D=2.0. It is also found that the potential-core inside the normal injection hole comprises a converging flow region, a diverging flow region, a developing flow region, and a flow region deflected by the crossflow.

The Role of Axial Flow in Near Wake on the Cross-Flow Vibration of the Inclined Cable of Cable-Stayed Bridges

2010 ◽  
Author(s):  
Masaru Matsumoto
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Axial Flow ◽  
Splitter Plate ◽  
Near Wake ◽  
Karman Vortex ◽  
The Cross ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

Nowadays, the violent wind-induced vibration, including “rain-wind induced vibration” and “dry-galloping”, of stay-cables of cable-stayed bridges has become the most serious issue for bridge design. Up-to-date, the major factors for excitation of inclined cables have been clarified to be, for “rain-wind” induced vibration, the formation of “water-rivulet” on the particular position of upper cable surface, and, for “dry galloping”, the “axial flow” which flows in the near wake along cable-axis, and the effect of drag-force associated with Reynolds number, separately. However, the details of the effect of “axial flow” remain unsolved. Thus, this study aims to clarify the effect of axial flow in near wake on the aero-elastic vibration of inclined cables basing on various experiments. The mean velocity of axial flow was almost 60% of approaching wind velocity. Furthermore, the aerodynamic effect of the “axial flow” on cross-flow vibration of inclined cables is discussed in relation to the mitigation of Karman vortex shedding in near wake. Since the role of axial flow seems to be similar to the splitter plate installed in wake from the point of mitigation of Karman vortex shedding, to clarify the cross-flow response in relation to the mitigation of Karman vortex, the perforated ratio of the splitter plate was variously changed, then the similarity of effect of axial flow and the one of splitter plate was verified comparing their unsteady lift force-characteristics. In summary, it is shown that the axial flow on aerodynamic cross-flow vibration might excite like galloping similarly with the splitter plate by mitigation of Karman vortex.

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