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Flow Induced Oscillations of a Helmholtz Resonator

Flow Induced Oscillations of a Helmholtz Resonator. Paul E. Slaboch Advisor: Scott C. Morris. Motivation. Interior pressure oscillations are a problem for both the automotive and aerospace communities.

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Flow Induced Oscillations of a Helmholtz Resonator

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  1. Flow Induced Oscillations of a Helmholtz Resonator Paul E. Slaboch Advisor: Scott C. Morris 2006 AME Graduate Student Conference

  2. Motivation • Interior pressure oscillations are a problem for both the automotive and aerospace communities. • In automotive vehicles, the very low frequency (~14-17 Hz) high amplitude pressure oscillations can exceed 120 dB, which can be painful to both drivers and passengers. • The goal of this study is to determine the underlying flow physics of the problem and to generate design guidelines for future vehicles to minimize buffeting. 2006 AME Graduate Student Conference

  3. Introduction • Helmholtz resonators occur when flow passes over an orifice, through a neck and into a volume. • The resonator can be modeled as a spring-mass system. • Uonset occurs when fn=fR 2006 AME Graduate Student Conference

  4. Previous Work 2006 AME Graduate Student Conference

  5. Previous Work 2006 AME Graduate Student Conference

  6. Experimental Setup Open Orifice PIV Cameras Cavity 2006 AME Graduate Student Conference

  7. Pressure Measurements 2006 AME Graduate Student Conference

  8. Pressure Measurements 2006 AME Graduate Student Conference

  9. Pressure Measurements 2006 AME Graduate Student Conference

  10. PIV Flow Visualization 2006 AME Graduate Student Conference

  11. PIV Measurements 2006 AME Graduate Student Conference

  12. Effect of Free Stream Velocity 2006 AME Graduate Student Conference

  13. Effect of BL Thickness 2006 AME Graduate Student Conference

  14. Future Work 2006 AME Graduate Student Conference

  15. Future Work 2006 AME Graduate Student Conference

  16. Conclusions • A series of experiments has been performed to determine the underlying flow physics of a flow induced Helmholtz resonator. • The actual mechanism of the oscillations is neither the roll up of discrete vortices nor a flag flapping shear layer instability. Rather, it appears to be a combination of the two. • The effect of free stream velocity is to spread the vorticity into a more continuous stream while the effect of the boundary layer thickness is to alter the location of the formation of a vortex. • This study, combined with future work, will provide design guidelines for automotive designers. 2006 AME Graduate Student Conference

  17. Thank you for your attention. • Questions? 2006 AME Graduate Student Conference

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