Yusuke Naka

Statistical Characterization of Atmospheric Turbulence Behavior Responsible for Sonic Boom Waveform Deformation

Atmospheric turbulent profiles were statistically quantified in characteristic scales for time, length, and velocity considered to be responsible for sonic boom waveform deformation in the troposph...

Effects of Vibrational Relaxation on Weak Shock Wave Structure in Air

A computational fluid dynamic method is developed to calculate the long range propagation of weak shock wave with the vibrational relaxation in air. Vibrational relaxation kinetics among N2 , O2 , and H2 O is accounted for by solving each species conservation equations with total mass, momentum and energy equations. The conservation equations are solved using a moving grid technique to capture the distortion of the wave during propagation. The propagation of the wave with an overpressure value typically observed in sonic boom on the ground is analyzed using the developed method. The computed results are mainly presented to show the ability to capture a dispersed nature in waves under different humidity conditions due to vibrational relaxation. The present result shows that the variation of a converged wave thickness dependent on a wide range of humidity can be recognized clearly by using the present method.© 2011 ASME

Experimental study on the effects of N‐wave sonic‐boom signatures on window vibration

For fulfillment of overland supersonic flight, it is important to understand the effects of sonic booms on buildings, since these effects, including vibration of walls and rattling noise from windows, are believed to be the main causes of annoyance in indoor spaces. In this study, the vibration of windows impacted by sonic booms is investigated through in‐laboratory experiments by using a device developed at Japan Aerospace Exploration Agency (JAXA). Rattle is captured as high‐frequency components of the acceleration of the windows. The effects of sonic booms having N‐shape signatures with various values of peak overpressure, rise time, and duration are investigated. Results show general tendency of increase of rattle with increasing peak overpressure and decreasing rise time, as expected. However, the results also indicate a possibility that these parameters, as well as duration, affect the time‐frequency structure of the acceleration (and hence rattle) of windows in a somewhat complicated manner.