Aeroacoustic Analysis of a NACA Duct
Regular paper
KTH Royal Institute of Technology
Wednesday 3 june, 2015, 09:00 - 09:20
0.1 London (90)
Abstract:
Since they were developed in the 1940s, NACA ducts have been used on numerous
types of ground and air vehicles. Their particular shape allows for air to be
passively dragged inside the vehicle with high pressure recovery and low drag.
Although their aerodynamic properties have been extensively studied, little
work has been done to assess their acoustic properties. In this paper an
aeroacoustic analysis of a typical NACA duct is performed for low Mach
numbers. The unsteady flow is solved through DES and the acoustics in the far
field is computed through the use of a Ffowcs Williams-Hawkings (FW-H)
integral. The results are analysed for various flow speeds. Acoustic results
are presented for both permeable and impermeable FW-H surfaces. These results
will be compared to experimental measurements. The mechanisms responsible for
noise generation are discussed and some ideas for solutions to reduce the
noise are proposed. Excessive noise generated by NACA ducts has been observed
on trains where the inlets, usually located along the side walls of the power
car, have been connected to tonal noise measured in pass-by tests. These
observations will be discussed with regard to the simulation cases.