Full Vehicle Aero-Thermal Cooling Drag Sensitivity Analysis for Various Radiator Pressure Drops

Simmonds, Nicholas; Tsoutsanis, Panagiotis; Drikakis, Dimitris; Gaylard, Adrian; Jansen, Wilko

doi:10.4271/2016-01-1578

Cited by 10 publications

(9 citation statements)

References 12 publications

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“…Current cooling air flow CFD studies can be traced to work undertaken on generic models such as the Ahmed body, modified with an internal duct, as performed by Barnard [1,2]. More recent work in the field has taken advantage of modern computational resources in modeling full vehicle airflow problems on production automotive geometries such as Large Saloons [3,4,5] and SUVs [3,6,7,8,9].…”

Section: Cooling Air Flowsmentioning

confidence: 99%

“…[10,11,12,13]. Other relevant work in this subject has focused on studying the effect of various components on the system [5,9,14].…”

Section: Cooling Air Flowsmentioning

confidence: 99%

“…The computational domain can be seen in Figure 5. These domain settings in STARCCM+ have previously resulted in accurate predictions for the cooling drag coefficient [5], the domain will be used for all models whereby they will be switched out and the center of the front of the vehicles positioned at (0.5,0,0) m.…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…Rotating wheels are modeled by Moving Reference Frames (MRF) in RANS and one configuration of the IDDES simulations to bridge the gap between the steady-state and transient simulations. A detailed discussion on the implementation of MRF's in this set-up can be seen in previous work by Simmonds et al [5]. Sliding mesh approaches were used for both IDDES and LBM methodologies.…”

Section: Boundary Conditionsmentioning

confidence: 99%

See 3 more Smart Citations

Complete Body Aerodynamic Study of three Vehicles

Simmonds¹,

Pitman²,

Tsoutsanis³

et al. 2017

SAE Technical Paper Series

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Cooling drag, typically known as the difference in drag coefficient between open and closed cooling configurations, has traditionally proven to be a difficult flow phenomenon to predict using computational fluid dynamics. It was seen as an academic yardstick before the advent of grille shutter systems. However, their introduction has increased the need to accurately predict the drag of a vehicle in a variety of different cooling configurations during vehicle development. This currently represents one of the greatest predictive challenges to the automotive industry due to being the net effect of many flow field changes around the vehicle. A comprehensive study is presented in the paper to discuss the notion of defining cooling drag as a number and to explore its effect on three automotive models with different cooling drag deltas using the commercial CFD solvers; STARCCM+ and Exa PowerFLOW. The notchback DrivAer model with under-hood cooling provides a popular academic benchmark alongside two fully-engineered production cars; a large saloon (Jaguar XJ) and an SUV (Land Rover Range Rover). Initially three levels of spatial discretization were used with three steady-state RANS solvers (k-ɛ realizable, k-ω SST and Spalart-Allmaras) to ascertain whether previous work using RANS on the large saloon studying cooling flows could be replicated on other vehicle shapes. For both the full-production vehicles, all three turbulence models were capable of predicting the cooling drag delta within 5 counts (0.005 C d). However, the DrivAer model was much more sensitive to both changes in turbulence models and mesh sizes. For the SA turbulence model only the drag coefficient was well predicted, for the other two RANS models no amount of grid refinement allowed the models to correctly predict the flow field. It was seen when comparing the k-ɛ realizable and SA turbulence models the difference in cooling drag was attributed to the rear of the vehicle. This highlighted that despite similar drag values from the cooling package, the cooling deltas were very different, suggesting that cooling drag cannot be thought of as open-closed drag with the addition of drag due to the cooling package. Further work on the DrivAer model expanded on the RANS simulations utilizing the eddy-resolving methods, IDDES and LBM, as validation cases. Oscillations which were seen in the SA and k-ω SST RANS turbulence models were shown to be of similar levels to those in the transient methods indicating a pseudo-unsteadiness present in the steady-state solvers and the importance of resolving it. Drag and lift coefficient absolute values were compared showing that only the IDDES method with sliding wheels and LBM method could obtain physical results for the majority of the tested criteria.

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Section: Cooling Air Flowsmentioning

confidence: 99%

“…[10,11,12,13]. Other relevant work in this subject has focused on studying the effect of various components on the system [5,9,14].…”

Section: Cooling Air Flowsmentioning

confidence: 99%

Section: Boundary Conditionsmentioning

confidence: 99%

Section: Boundary Conditionsmentioning

confidence: 99%

See 2 more Smart Citations

Complete Body Aerodynamic Study of three Vehicles

Simmonds¹,

Pitman²,

Tsoutsanis³

et al. 2017

SAE Technical Paper Series

Self Cite

View full text Add to dashboard Cite

show abstract

“…9 show C D , C LF and C LR on the vertical axis, respectively, for change of opening heights of the air intake on the horizontal axis, where (a) and (b) indicate the cases without and with radiator, respectively.T. Sawaguchi, Y. Takakura Journal of Flow Control, Measurement & Visualization…”

mentioning

confidence: 99%

Reduction of Aerodynamically Undesirable Influences Due to Engine Cooling Flow in Road Vehicle

Sawaguchi¹,

Takakura²

2020

JFCMV

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The purpose of this research is to clarify causes for the change in aerodynamic characteristics of a road vehicle model due to engine cooling flow in wind-tunnel experiments with the moving-belt ground board, in order to propose methods to reduce the drag and lift. With regard to engine cooling flow, the air-intake system was adjusted with variable opening area and position for the engine loading system of FF and FR with and without a radiator. A simplified 1/5 scale vehicle model was manufactured with transparent externals around the engine for flow visualization. The overall results show that with enlargement of the opening area, the drag and the front lift increased and the rear lift decreased. The flow visualization and the measurements of underfloor velocity and surface pressure indicated the cause of the characteristics changes. Enlargement of the opening area causes flow disturbance by merging of the scavenging flow and the underfloor flow, which has blockage effects for the upstream of each flow with keeping high pressure in the engine compartment and causes pressure loss under the floor behind the engine unit. The difference between the two engine loading systems lies indirection and location of the engine unit, which causes the differences of how the flow features affect the aerodynamic characteristics. The effect of the radiator is to reduce the range of changes in drag and lift. Finally, it is discussed that the principle of reducing drag and lift is to suppress interference of scavenging flow, and concrete methods are proposed.

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