OJFD  Vol.6 No.2 , June 2016
Aerodynamic Sound Radiated from Longitudinal and Transverse Vortex Systems Generated around the Leading Edge of Delta Wings
Abstract: Flow around the front pillar of an automobile is typical of a flow field with separated and reattached flow by a vortex system. It is known that the vortex system causes the greatest aerodynamic sound around a vehicle. The objective of the present study is to clarify the relationship between vortical structures and aerodynamic sound by the vortex system generated around the front pillar. The vortex system consists of the longitudinal and the transverse system. The characteristics of the longitudinal vortex system were investigated in comparison with the transverse one. Two vortex systems were reproduced by three-dimensional delta wings. The flow visualization experiment and the computational fluid dynamics (CFD) captured well the characteristics of the flow structure of the two vortex systems. These results showed that the longitudinal with the rotating axis along mean flow direction had cone-shaped configuration whereas the transverse with the rotating axis vertical to mean flow direction had elliptic one. Increasing the tip angles of the wings from 40 to 140 degrees, there first exists the longitudinal vortex system less than 110 degrees, with the transition region ranging from 110 to 120 degrees, and finally over 120 degrees the transverse appears. The characteristics of aerodynamic sound radiated from the two vortex systems were investigated in low Mach numbers, high Reynolds number turbulent flows in the lownoise wind tunnel. As a result, it was found that the aerodynamic sound radiated from both the longitudinal and the transverse vortex system was proportional to the fifth from sixth power of mean flow velocity, and that the longitudinal vortex generated the aerodynamic sound larger than the transverse.
Cite this paper: Ogawa, S. , Takeda, J. , Kawate, T. and Yano, K. (2016) Aerodynamic Sound Radiated from Longitudinal and Transverse Vortex Systems Generated around the Leading Edge of Delta Wings. Open Journal of Fluid Dynamics, 6, 101-118. doi: 10.4236/ojfd.2016.62009.

[1]   Lighthill, M.J. (1952) On Sound Generated Aerodynamically I. General Theory. Proceedings of the Royal Society of London A, 211, 564-587.

[2]   Curle, N. (1955) The Influence of Solid Boundaries upon Aerodynamic Sound. Proceedings of the Royal Society of London A, 231, 505-514.

[3]   Howe, M.S. (2003) Theory of Vortex Sound: Cambridge Texts in Applied Mathematics. Cambridge University Press, Cambridge.

[4]   Howe, M.S. (2014) Acoustics and Aerodynamic Sound. Cambridge University Press, Cambridge.

[5]   Haruna, S., Nouzawa, T., Kamimoto, I. and Sato, H. (1990) An Experimental Analysis and Estimation of Aerodynamic Noise Using a Production Vehicle. SAE Transactions: Journal of Passenger Cars, 99, SAE Technical Paper 900316.

[6]   Nouzawa, T., Li, Y. and Nakamura, T. (2011) Mechanism of Aerodynamic Noise Generated from Front-Pillar and Door Mirror of Automobile. Journal of Environment and Engineering, 6, 615-626.

[7]   Hamamoto, N., Okutsu, Y. and Yanagimoto, K. (2013) Investigation for the Effect of the External Noise Sources onto the Interior Aerodynamic Noise. Proceedings of SAE 2013 World Congress & Exhibition, Detroit, 16-18 April 2013, SAE Technical Paper 2013-01-1257.

[8]   Haruna, S., Hashiguchi, M., Kamimoto, I. and Kuwahara, K. (1992) Numerical Study of Aerodynamic Noise Radiated from a Three-Dimensional Wing. SAE Transactions: Journal of Passenger Cars, 101, SAE Technical Paper 920341.

[9]   Takeda, J. and Ogawa, S. (2014) Prediction of Aerodynamic Noise Radiated from a Delta Wing. Proceedings of the 4th International Symposium on Technology for Sustainability, Taipei, 19-21 November 2014.

[10]   Ogawa, S. and Li, Y. (2014) Control of Longitudinal Vortex Generated around Front Pillar of Vehicles, Based on Clarification of the Vortex Generation Mechanism Using a Delta-Wing. Proceedings of the 12th International Conference on Motion and Vibration Control, Hokkaido, 3-7 August 2014.

[11]   Jacobi, A.M. and Shah, R.K. (1995) Heat Transfer Surface Enhancement through the Use of Longitudinal Vortices: A Review of Recent Progress. Experimental Thermal and Fluid Science, 11, 295-309.

[12]   Iwasaki, M., Hara, J. and Honda, I. (2014) Development of Vortex Generator for EGR Cooler. Proceedings of FISITA 2014 World Automotive Congress, Maastricht, 2-6 June 2014.

[13]   Ogawa, S. (1995) Aerodynamic Noise of a Body with Separated and Reattached Flow by Longitudinal Vortices. Ph.D. Thesis, University of Tokyo, Tokyo.

[14]   Ogawa, S. (1995) Generation Mechanism of Aerodynamic Noise by Interference between Longitudinal Vortex and Body. Proceedings of the 44th Japan National Congress for Applied Mechanics, 44, 215-220.

[15]   Ogawa, S. and Takeda, J. (2015) Mechanism of Generation and Collapse of a Longitudinal Vortex System Induced around the Leading Edge of a Delta Wing. Open Journal of Fluid Dynamics, 5, 265-274.