Spectral Density and Time Scales of Velocity Fluctuations in the Wake of a Simplified Car Model Univ. of Erlangen

Format:

Conference/Event

Author/Creator:

Lienhart, Lienhart, author.

Contributor:

Pêgo, João Pedro

Conference Name:

SAE 2012 World Congress & Exhibition (2012-04-24 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

Although CFD is considered a well-established tool in thedevelopment of car aerodynamics it is obvious that there is still astrong demand on verification and validation of schemes and modelsinvolved in the numerical codes. This is reflected by theconstantly high number of publications dealing with the matter. Oneof the test cases most often adopted for the purpose is the genericcar model proposed by Ahmed and others This is because of itsgeometrical simplicity and the realistic complex flow field whichis reproducibly generated in its wake and makes it a selective testcase. Another reason is the availability of comprehensiveexperimental data sets, amongst others the one we reported in anearlier paper. The velocity data covers the complete flow fieldaround the model but focuses on the wake region. Besides meanvalues it provides turbulence quantities such as Reynolds stressesand other higher-order statistical moments measured usinglaser-doppler anemometry (LDA).After reviewing the results of numerous CFD approaches andcomparing those to the experimental data it turns out that mostdeficiencies arise from the failing prediction of detachment andreattachment of the flow on the rear body at a slant angle of 25°.A closer analysis reveals a severe underestimation of thefluctuating quantities in the wake and most notably in the shearlayers between the outer flow and the recirculation region. Thisfact in turn can be directly associated with the difficulties inpredicting reattachment. Because of these findings further LDAmeasurements with high spectral resolution were performed atselected locations. One major aim of the study was to identify thetime scales of the fluctuations and in this way to come tosuggestions what measures are advisable to reduce the uncertaintiesboth in CFD and experimental results

Notes:

Vendor supplied data

Publisher Number:

2012-01-0592

Access Restriction:

Restricted for use by site license