1. Status Report of New Issues TF –CFD* sub wg
WLTP-26-14e
CFD subwg
Status Report of New Issues TF –CFD* sub wg
*CFD: Computational Fluid Dynamics method, method to simulate aero drag
18th Jan., 2019
Mayumi “Sophie” Morimoto (JASIC)

2. Review of CFD sub wg report on 22nd WLTP IWG

3. Review of CFD sub wg report on 25th WLTP IWG

4. Status of CFD discussion
Status & Schedule
3 meetings was held after 25th Sep. WLTP IWG.
1 Workshop was held with a great support from European Commission, software venders, OEMs.
No meeting is planned before 27th WLTP IWG.
Workshop in 11th April
Members from European Commission, UTAC (France), VCA (UK), NTSEL (Japan), and Malta joined the workshop.
Software vender Dessault Systems explained the areas that Computational fluid dynamic methods (flow-simulation) are used. - Medical, Air crafts, oil mining, heavy-duty aero drag in US, etc.
European Commissions made presentation on European process for validation of virtual test pattern written in Directive 2007/46/EC Annex XVI, Appendix 1.
Skoda made presentation as OEM on how CFD are used within development of the vehicle.

5. Status of CFD discussion
Proposal from WLTP CFD sub-wg on discussion
for software validation for simulation of aero drag
(See WLT-26-11e_app1 for more details)
Motivation
Current requirement for flow-field validation in Annex 7, § (a) to GTR 15 doesn’t specify the measurement method and criteria
CFD sub-wg members propose to add ΔcD·A correlation approach (in analogy to wind tunnel method validation in Annex 4, § 6.2)
We also propose to replace the requirement for flow-field validation with the proposed ΔcD·A correlation approach
Premise
CFD simulation in WLTP is intended for calculation of optional equipment (not absolute values, only ΔcD·A).
General idea of the ΔcD·A correlation approach
Compare the results (ΔcD·A) from the Wind Tunnel and the simulation software for one or more vehicle types/body-styles (depending on model potrfolio and intended simulation usage) and a specific number of optional equipment parts (e.g. several types of wheels).
Large enough set of compared variants can assure the validity of the CFD method and indirectly prove the validity of the flow-field.
CFD sub-wg members want to clarify the method

6. Thank you very much for your attention!