CFD investigation of a generic vehicle side-view mirror
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Typ
Projektarbete, avancerad nivå
Program
Publicerad
2020
Författare
Ibáñez, Cristóbal
Palm, Richard
Rahani, Ramin
Shao, Xinyuan
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Electric automobiles are becoming more common in today’s society. Since interior
car noise can have negative mental health effects for the driver and passengers, it becomes
relevant to find out how it is being generated. One important source of noise
is the surface pressure fluctuations caused by shear layer impingement and turbulence
from the flow around a side-view mirror. Even though many studies about the
flow past a side-view mirror have been done, there is not sufficient research for lower
speed cases at which electric cars drive at. The purpose of this project is therefore
to study the flow around a generic side-view mirror and investigate how it generates
noise for some of these cases. The computational fluid dynamics (CFD) software
STAR-CCM+, running both steady and unsteady Reynolds-Averaged Navier Stokes
(RANS) simulation models is used. Three cases at different freestream speeds of 20,
30 and 40 m/s are simulated. To ensure accurate results, a mesh independence study
is carried out for the 40 m/s case with steady RANS simulation. The final mesh
is then used to simulate the 20 and 30 m/s cases as well. The steady flow fields
were obtained using the realizable k −" model and later used as initialization fields
for the unsteady cases, were SST k − ! model is used. Pressure fluctuations data
series of specific sensors placed on the surfaces of the mirror and window where analyzed
for their power spectral density (PSD) in the frequency domain. For sensors
placed in the back of the mirror and on the window inside the recirculation region,
noticeable peaks at 500-1300 Hz in the signal’s power were observed. Comparison
of the PSD’s against the Strouhal number revealed that the power peaks are due to
coherent structures in the free shear layer developed from the mirror edges. Those
PSD peaks will generate tonal noise which is of 500-1300 Hz. Measures should be
taken to prevent drivers and passengers from hearing this kind of noise. The present
study is also a fundamental step to provide hydrodynamic pressure fluctuation data
for a future acoustic wave simulations.
Beskrivning
Ämne/nyckelord
side-view mirror , URANS , pressure fluctuation , PSD , SST k −! model , realizable k − " model