Shock Wave Pressure and Velocity Measuring Using a Novel Optic Sensor in a Newly Designed Diaphragm-less Shock Tube

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RESEARCH PAPER

Shock Wave Pressure and Velocity Measuring Using a Novel Optic Sensor in a Newly Designed Diaphragm-less Shock Tube M.A. Samimi 1 & J. Zamani 1 & F. Sardarzadeh 1 Received: 3 February 2020 / Accepted: 20 October 2020 # The Society for Experimental Mechanics, Inc 2020

Abstract This paper suggests a new optical system for measuring shock wave characteristic that is installed in a shock tube. This shock tube has an innovative pneumatic rapid opening valve designed to open from the center of the tube to the corners. In this measurement system, a plate has placed in front of the shock wave. The plate displacement has measured during a collision by measuring the amount of light reflectance change. Then these optical data have converted to a voltage. After calibration with the help of a piezoresistive sensor in the shock tube and showing its voltage-pressure relation, the shock wave pressure diagram has been demonstrated, which contains the wave’s positive and negative parts. Also, the delay time in this system is investigated. In addition to the shock wave velocity, the system can measure the timing and velocity opening of the pneumatic valve replaced in the shock tube. The velocity is also calculated theoretically and compared with the experimental results. The unique feature of this automatic valve is its opening from the center of the tube to the corners, like a camera aperture, which is best suited for opening the valve and resulting wave uniformity. Also, the alignment of the driver and the driven prevented gas perturbation due to the redirection or rotation. This problem has seen in most recently used valves. Finally, the planar shock wave formation has been investigated. Keywords Shock wave . Shock tube . Rapid opening valve . Optical measurement system . Calibration

Introduction Scientists have studied the shock wave for many years. Producing shock wave, and its effects are one of the main headings in explosion mechanics. One of the restrictions for producing shock waves is the requirement for explosive substances. It has been years that the scientists of this field have provided the possibility of shock wave creating with no need for an explosive substance. By using shock tubes, scientists have provided the possibility to generate a shock wave without the need for explosives. Producing controlled and similar shock waves even with the help of explosive substances are tough, however shock tubes have made it possible. Shock tubes have a wide range of applications; such as studying the shock waves [1], calibration of sensors [2], studying gas circulation [3], modeling and studying of boundary * F. Sardarzadeh [email protected] 1

Mechanical Engineering, K.N.Toosi University, Tehran, Iran

layers on physical samples [4], the pattern of gas compounds combustion and solid fuel ignition [5]. Besides, there are many applications in the aerospace industry [6], medical and military; such as studying brain injuries caused by the explosion [7] considering the effect of shock waves on metal plates [8