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Second Automotive CFD WorkshopCase 1 Windsor Model
Gary PageAeronautical & Automotive Engineering
Loughborough University
Introduction} First Automotive CFD Workshop had two cases:
} SAE Notchback} DrivAer
} SAE more accessible, geometrically simpler, less computationally resource intensive } Resulted in 34 predictions from 11 contributors
} Same approach this year, but using the Windsor Model} Plentiful data taken in Loughborough University wind tunnel (up to and
including tomographic PIV)
https://repository.lboro.ac.uk/articles/dataset/Windsor_Body_Experimental_Aerodynamic_Dataset/13161284
2 Second Automotive CFD Workshop
Windsor Model
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Varney, M., “Base Drag Reduction for Squareback Road Vehicles,” Loughborough University, Feb, 2020.10.26174/thesis.lboro.11823759.v1
'with Wheels’ wW Cases 1A and ‘no Wheels’ nW Case 1B
Second Automotive CFD Workshop
Domain
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} Experiment: a 3.2m long working section, 1.92m wide x 1.32m high cross section expanding to 1.94m wide
} CFD: extend upstream and downstream to 11m long, parallel sidewalls (but no slip)
Second Automotive CFD Workshop
Grids
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} 8 grids supplied, combinations of:} RANS or Eddy Resolved} Wall Modelled or Wall Resolved} Wheels or No Wheels
} RANS are half model (with symmetry), Eddy Resolved full model} Trimmer + Prism layers generated in STAR-CCM+} Range from 3.3M cells (nW_WMRANS) to 50M cells (wW_WRER)} Aim to be consistent across all grids:
} WR vs WM change prism layers only} RANS vs ER change grid spacing under car and in wake only
} If impossible to use these grids, then should supply solution matching as closely as possible (Table 1 of document)
Second Automotive CFD Workshop
Grids
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Refinement zones
Origin on floor at mid-track, mid-wheelbase
Second Automotive CFD Workshop
Wheel Treatment: Experiment
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} Non rotating, attached to body, ‘trough’ to give 3-4mm clearance} Pins transmit force to balance
CHAPTER 2. EXPERIMENTAL METHODOLOGY
contact patch, but with a small amount of clearance to prevent the model grounding
with the tunnel floor. This version of the model was initially designed to have
rotating wheels, but here they have been hard mounted to the model body and to
prevent grounding of the model, a pad beneath each wheel is recessed to maintain
a ⇠ 4mm gap between the wheel and the floor, as shown in Figure 2.3.
(a) No wheels - Wheel arch blank (b) With wheels - Wheel installed
Figure 2.2: Comparison between the no wheel and with wheel models.
Figure 2.3: Windsor wheel interface with the tunnel floor.
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Second Automotive CFD Workshop
Wheel Treatment: CFD
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} Dropped wind tunnel floor by 3mm to give same clearance with flat ground plane} Retained pins
Second Automotive CFD Workshop
Wall Spacing
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Wall Modelled: aim for y+ 60-100 Wall Resolved: aim for y+ 0.5-2
Second Automotive CFD Workshop
Inflow Boundary Layer Velocity
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} Upstream extent chosen to grow broadly correct boundary layer thickness} Empty tunnel simulated with WR RANS SST and compared to original tunnel
reports at centre of working section
Inflow Boundary Layer Turbulence
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File Formats
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} Generated in STAR-CCM+ and exported as .ccm file} May be directly readable by other packages?
} .ccm imported into ANSA, then exported as } OpenFOAM} CGNS} Fluent .msh
Closure} Set of 8 grids ready
} Potential issue with wheel treatment?
} Reporting requirements to be defined:} Compulsory: forces, moments, limited pressures} Optional: full surface, cuts
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