Investigation of the Cooling and Underbody Flow Field on a Detailed Scale Model Passenger Car: Part 2—Effect of Ground Simulation

2009 ◽  
Author(s):  
Christoffer Landstro¨m ◽  
Lasse Christoffersen ◽  
Lennart Lo¨fdahl
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Aerodynamic Drag ◽  
Scale Model ◽  
Experimental Investigations ◽  
Passenger Cars ◽  
Local Flow ◽  
Passenger Car ◽  
Reynolds Number Effects ◽  
Cooling Air

Future demands on passenger cars consist to a large extend of making them more energy efficient. Reducing the driving resistance by reducing the aerodynamic drag will be one important part in reducing fuel consumption. In most cases during passenger car development, early experimental investigations are performed in scale model wind tunnels. Considering that such models inevitably suffer from Reynolds number effects it is important to understand how this affects the test results. Investigations of the aerodynamics of a detailed scale model Volvo S60 have been performed in the aerodynamic wind tunnel at Chalmers University of Technology. The investigation aimed at increasing the understanding of how the flow field in scale model testing is affected by ground simulation and different cooling air flow configurations at different Reynolds numbers. A full width moving ground system was used in the experiments. Pressure taps were distributed between the cooling air inlets, the underbody and the vehicle base. An internal six component balance was used to measure global forces and moments. By combining the results from the measurements it was possible to increase the understanding of some of the local flow features. Results showed significant Reynolds number effects both with stationary ground as well as moving ground and rotating wheels. Global aerodynamic drag as well as front and rear axle lift was found to be affected.

Investigation of the Cooling and Underbody Flow Field on a Detailed Model Scale Passenger Car: Part 1—Cooling Flows and Reynolds Number Effects

2009 ◽  
Author(s):  
Lasse M. Christoffersen ◽  
Christoffer Landstro¨m ◽  
Lennart Lo¨fdahl
Keyword(s):  
Reynolds Number ◽  
Lead Time ◽  
Primary Source ◽  
Scale Model ◽  
Passenger Car ◽  
Detailed Model ◽  
Cooling Flows ◽  
Car Model ◽  
Reynolds Number Effects ◽  
Reynolds Number Dependency

To decrease the lead time and hence cost for an aerodynamic development programme for a new car model, extended use of down scaled wind tunnel models is one possibility. This however, requires that the models carry many of the exterior, engine bay and underbody details that are present on the full scale counterpart. An important issue in scale testing is to understand the Reynolds number effects that will be present and with an increased detail level of the model it is believed that there will be other Reynolds number effects than on the simplified models that historically have been used. Therefore; the aim of this work is to explain some of the Reynolds number effects that are developed on a detailed model of a sedan type passenger car. The analysis is based on experimental data with both load and pressure measurements as the primary source carried out on a 30% model of a Volvo S60. In the experiment both moving ground and rotating wheels were utilized. With the Reynolds number ranging from 8.8e5 to 3.5e6 it was possible to notice interesting Reynolds number effects. The results show that there is a significant Reynolds number dependency of the scale model. However, it is also shown that the Reynolds number dependency is dependent on the detail level of the model.

Investigation of Aerodynamic Wheel Designs on a Passenger Car at Different Cooling Air Flow Conditions

2011 ◽  
Author(s):  
Christoffer Landstro¨m ◽  
Lennart Lo¨fdahl
Keyword(s):  
Drag Reduction ◽  
Aerodynamic Drag ◽  
Air Flow ◽  
Flow Structures ◽  
Sustainable Mobility ◽  
Passenger Cars ◽  
Passenger Car ◽  
Flow Configurations ◽  
Cooling Air Flow ◽  
Cooling Air

Passenger cars represent the largest part of all means of personal transportation today. Thus, it is important to work towards reduced energy consumption of cars if a sustainable mobility is to be achieved. This involves many aspects of vehicle engineering; one of them being aerodynamics. This study focuses on aerodynamic drag and the contributions from the wheels at different cooling air flow configurations. Wheels and wheel housings are important for the overall aerodynamic drag on passenger cars. It has been shown that as much as 25% of the aerodynamic drag originates from these components. Therefore, it is desirable to understand the flow structures related to the wheels and wheel housings, and how they interact with other important flow regions. This paper presents an investigation of the effects of wheel designs on aerodynamic drag at different cooling air flow configurations on a sedan type passenger car. Comparisons between numerical simulations and wind tunnel measurements are made for some of the configurations as well. Several additional wheel configurations were investigated numerically to further investigate the flow structures at the front and rear wheels. The numerical results show that the effects of radial wheel covering varied noticeably with cooling air flow configuration. In two of the configurations this resulted in a net drag increase with closed cooling air inlets. The best configuration with closed cooling air inlets generated an overall drag reduction of 29 drag counts compared with the numerical baseline with open cooling air inlets. In addition to the obvious drag reduction of closing the cooling air inlets, the main reasons for the additional decrease was limiting the drag increase at the front stagnation region and positive interference effects along the underbody and vehicle base.

CFD Study of Hydrodynamics and Separation Performance of a Novel Crossflow Filtration Hydrocyclone (CFFH)

2014 ◽  
Author(s):  
Abdul Motin ◽  
Volodymyr V. Tarabara ◽  
André Bénard
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Separation Efficiency ◽  
Cross Flow ◽  
Scale Model ◽  
Navier Stokes ◽  
Dispersed Phase ◽  
Separation Performance ◽  
Porous Filter ◽  
Discrete Phase

This research addresses various hydrodynamic aspects and the separation performance of a novel cross-flow filtration hydrocyclone (CFFH) using computational fluid dynamics. A CFFH is a device that combines the desirable attributes of a cross-flow filter and a vortex separator into one unit to separate oil from water. The velocity and pressure fields within the CFFH are estimated by numerically solving the filtered Navier-Stokes equations (by using a Large Eddy Simulation (LES) approach). The Lagrangian approach is employed for investigating the trajectories of dispersed droplets based on a stochastic tracking method called the Discrete Phase Model (DPM). The mixture theory with the Algebraic Slip Model (ASM) is also used to compute the dispersed phase fluid mechanics and for comparing with results obtained from the DPM. In addition, a comparison between the statistically steady state results obtained by the LES with the Wall Adaptive Local Eddy-Viscosity (WALE) subgrid scale model and the Reynolds Average Navier-Stokes (RANS) closed with the Reynolds Stress Model (RSM) is performed for evaluating their capabilities with regards to the flow field within the CFFH and the impact of the filter medium. Effects of the Reynolds number, the permeability of the porous filter, and droplet size on the internal hydrodynamics and separation performance of the CFFH are investigated. Results indicate that for low feed concentration of the dispersed phase, separation efficiency obtained based on multiphase and discrete phase simulations is almost the same. Higher Reynolds number flow simulations exhibit an unstable core and thereby numerous recirculation zones in the flow field are observed. Improved separation efficiency is observed at a lower Reynolds number and for a lower permeability of the porous filter.

scholarly journals EFFECT OF THE SPANWISE DISCRETISATION ON TURBULENT FLOW PAST A CIRCULAR CYLINDER

2021 ◽  
Vol 158 (A1) ◽  
Author(s):  
S Kim ◽  
P A Wilson ◽  
Z Chen
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Scale Model ◽  
Spatial Density ◽  
Eddy Simulation ◽  
Large Eddy

The effect of the spanwise discretisation on numerical calculations of the turbulent flow around a circular cylinder is systematically assessed at a subcritical Reynolds number of 10000 in the frame of three-dimensional large-eddy simulation. The eddy-viscosity k-equation subgrid scale model is implemented to evaluate unsteady turbulent flow field. Large-eddy simulation is known to be a reliable method to resolve such a challenging flow field, however, the high computational efforts restrict to low Reynolds number flow or two-dimensional calculations. Therefore, minimum spatial density in the spanwise direction or cylinder axis direction needs to be carefully evaluated in order to reduce high computational resources. In the present study, the influence of the spanwise resolutions to satisfactorily represent three- dimensional complex flow features is discussed in detail and minimum spatial density for high Reynolds flow is suggested.

Flow Field Investigations on the Effect of Rib Placement in a Cooling Channel With Film-Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Martin Kunze ◽  
Konrad Vogeler
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Film Cooling ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Experimental Investigations ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Field Investigations ◽  
Small Influence

This paper presents experimental investigations on flat plate film-cooling in combination with a ribbed cooling channel. The effect of rib placement on the film-cooling injection and the flow in the cooling channel was studied. The velocity fields were measured using optical laser measurement techniques including LDA (laser doppler anemometry) and PIV (particle image velocimetry). A row of three cylindrical film holes is placed in the center rib segment of the cooling channel. The dimensionless rib-to-hole position s/D is varied from 4.5 to 10.5. The investigations are conducted at isothermal conditions for a variation of the coolant Reynolds number Rec,Dh from 10,000 up to 60,000 and for three blowing rates M = 0.5, 0.75, and 1.00. The flow field results for the film-cooling injection showed only a small influence of the rib placement. Due to different coolant-to-main flow pressure ratios across the row, a slight nonuniform share of coolant flow occurs. Intense streamwise mixing and decay of the turbulence in the film jet was observed within the first 10 hole diameters. Enhancement of the turbulence intensity inside the jet core was found with increasing coolant Reynolds numbers. Inside the internal cooling channel, the flow field showed significant influence of the rib position which is most pronounced at low Reynolds number (Rec,Dh = 10,000) and high blowing ratios (M = 1.0). The effect becomes significantly smaller when the Reynolds number is increased. This is mainly attributed to the strongly increasing channel mass flow which equals to a decreasing suction ratio SR = uh/uc of the holes. The experimental results are compared to comprehensive numerical simulations.

Numerical Investigation of the Influence of Side Winds on a Simplified Car at Various Yaw Angles

2010 ◽  
Author(s):  
Sinisˇa Krajnovic´ ◽  
Sasan Sarmast
Keyword(s):  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Numerical Investigation ◽  
Scale Model ◽  
Passenger Car ◽  
Eddy Simulation ◽  
Moderate Reynolds Number ◽  
Large Eddy ◽  
Reynolds Number Flows

The flow around a generic passenger car under the influence of crosswind was predicted using large eddy simulation (LES). The Reynolds number based on the incoming velocity the car’s length, L used was Re = 9 × 105. Yaw angles of crosswind of 10°, 20° and 30° were studied and the LES results were compared with the experimental observations and previous Reynolds averaged Naviers-Stokes (RANS) and detached eddy simulations (DES). The present LES were found to predict flows in better agreement with the experimental observations than previous RANS and DES. This shows that LES is better suited than RANS or DES for moderate Reynolds number flows around scale-model car in crosswinds which are inherently unsteady with regions of massive separations.

scholarly journals Wake Flow Investigation on Notchback MIRA Model by PIV Experiments

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4568
Author(s):  
Yingchao Zhang ◽  
Jinji Li ◽  
Zijie Wang ◽  
Qiliang Wang ◽  
Hongyu Gong ◽  
...  
Keyword(s):  
Flow Field ◽  
Aerodynamic Drag ◽  
Three Dimensional ◽  
Field Structure ◽  
Wake Flow ◽  
Scale Model ◽  
Flow Mechanism ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Piv Method

To deepen our understanding of the flow field and flow mechanism of a car-like model, in this paper, an experimental investigation of the flow field of MIRA notchback 1/8 scale model is carried out using Particle Image Velocimetry (PIV) method. The tests are conducted in an open circuit wind tunnel at a Reynolds number of . In order to obtain the detailed flow field structure of the notchback model, the PIV method was used to capture the flow field images from three orthogonal directions. By studying the vorticity and velocity vector figures of both the time-averaged and instantaneous states, a three-dimensional flow field schematic of the notchback model is summarized, and the formation mechanism and development process of the vortices are analyzed. This study not only provides an intuitive display of the three-dimensional flow field structure of the MIRA notchback model but, more importantly, it provides a reference for the development of automobile aerodynamic drag reduction by analyzing the flow mechanism, which is beneficial to energy conservation.

scholarly journals Reynolds number and wind tunnel wall effects on the flow field around a generic UHBR engine high-lift configuration

2020 ◽  
Vol 11 (4) ◽  
pp. 1009-1023 ◽  
Author(s):  
Junaid Ullah ◽  
Aleš Prachař ◽  
Miroslav Šmíd ◽  
Avraham Seifert ◽  
Vitaly Soudakov ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Flow Field ◽  
Test Section ◽  
Large Scale ◽  
Scale Model ◽  
Small Scale ◽  
Wall Effects ◽  
Tunnel Wall ◽  
High Lift

Abstract RANS simulations of a generic ultra-high bypass ratio engine high-lift configuration were conducted in three different environments. The purpose of this study is to assess small scale tests in an atmospheric closed test section wind tunnel regarding transferability to large scale tests in an open-jet wind tunnel. Special emphasis was placed on the flow field in the separation prone region downstream from the extended slat cut-out. Validation with wind tunnel test data shows an adequate agreement with CFD results. The cross-comparison of the three sets of simulations allowed to identify the effects of the Reynolds number and the wind tunnel walls on the flow field separately. The simulations reveal significant blockage effects and corner flow separation induced by the test section walls. By comparison, the Reynolds number effects are negligible. A decrease of the incidence angle for the small scale model allows to successfully reproduce the flow field of the large scale model despite severe wind tunnel wall effects.

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