Imperial College London
Portrait Picture

Professor Aimee S. Morgans

Faculty of Engineering, Department of Mechanical Engineering

Professor of Thermofluids
 
 
 
//

Contact

 

+44 (0)20 7594 9975a.morgans

 
 
//

Location

 

621City and Guilds BuildingSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Hesse:2021:10.1016/j.compfluid.2021.104901,
author = {Hesse, F and Morgans, AS},
doi = {10.1016/j.compfluid.2021.104901},
journal = {Computers & Fluids},
pages = {1--17},
title = {Simulation of wake bimodality behind squareback bluff-bodies using LES},
url = {http://dx.doi.org/10.1016/j.compfluid.2021.104901},
volume = {223},
year = {2021}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - A large eddy simulation (LES) study of the flow around a 1/4 scale squareback Ahmed body at Re H = 33 , 333 is presented. The study consists of both wall-resolved (WRLES) and wall-modelled (WMLES) simu- lations, and investigates the bimodal switching of the wake between different horizontal positions. Within a non-dimensional time-window of 1050 convective flow units, both WRLES and WMLES simulations, for which only the near-wall region of the turbulent boundary layer is treated in a Reynolds-averaged sense, are able to capture horizontal (spanwise) shifts in the wake’s cross-stream orientation. Equilib- rium wall-models in the form of Spalding’s law and the log-law of the wall are successfully used. Once these wall-models are, however, applied to a very coarse near-wall WMLES mesh, in which a portion of the turbulent boundary layer’s outer region dynamics is treated in a Reynolds-averaged manner as well, large-scale horizontal shifts in the wake’s orientation are no longer detected. This suggests larger-scale flow structures found within the turbulent boundary layer’s outer domain are responsible for generat- ing the critical amount of flow intermittency needed to trigger a bimodal switching event. By looking at mean flow structures, instantaneous flow features and their associated turbulent kinetic energy (TKE) production, it becomes clear that the front separation bubbles just aft of the Ahmed body nose generate high levels of TKE through the shedding of large hairpin vortices. Only in the reference WRLES and (rela- tively) fine near-wall mesh WMLES simulations are these features present, exemplifying their importance in triggering a bimodal event. This motivates studies on the suppression of wake bimodality by acting upon the front separation bubbles.
AU  - Hesse,F
AU  - Morgans,AS
DO  - 10.1016/j.compfluid.2021.104901
EP  - 17
PY  - 2021///
SN  - 0045-7930
SP  - 1
TI  - Simulation of wake bimodality behind squareback bluff-bodies using LES
T2  - Computers & Fluids
UR  - http://dx.doi.org/10.1016/j.compfluid.2021.104901
UR  - https://www.sciencedirect.com/science/article/pii/S0045793021000670?via%3Dihub
UR  - http://hdl.handle.net/10044/1/87850
VL  - 223
ER  -
Download