On using converging shock waves for pressure amplification in shock tubes

Abstract

While conventional shock tubes have a distinct advantage in dynamic calibration methods due to their inherent capability to generate pressure pulses of desired amplitude and fast rise time, they are limited to the lower levels of the pressure amplitude realization range (≤7 MPa). With the increasing need for a traceable dynamic calibration standard across wider pressure ranges, a novel technique using converging shock waves is demonstrated in this work that pushes the upper limit of the standard shock tube into the medium-high pressure range. The experiments are conducted in the shock tube facility equipped with a test section that smoothly transforms the incident plane shock into a spherical shock wave that converges, accelerates and thereby amplifies its strength many folds. The experimentally recorded pressure traces are compared with numerical simulations performed by an in-house code. Using this technique, pressure pulses with peak amplitudes in the range of 30–40 MPa, with < 3.4% uncertainty based on numerical reference profile, were realized in the test section with nominal usage of resources.

Laser-induced cavitation bubbles and shock waves in water near a concave surface

“…Focusing of SWs can be either intentionally exploited or may be an undesirable effect. Converging shocks are used in technology (SW ignition of fusion [2] and concave detonation-driven shocks [3] ) basic science (converging SW triggered star formation, supernova explosions and void collapses [4] and pressure amplification setups [5] ) and medicine (extracorporeal SW lithotripsy [6] , drug delivery by SW focusing [7] , SW mediated cell transfection [8] and high-intensity focused ultrasound (HIFU) [9] ). Detrimental effects of SW focusing are found in aeronautics (superbooms caused by a turning maneuver of a supersonic aircraft [10] ) automotive industry (damage of combustion chambers [11] ) and also medicine (possible collateral tissue damage following laser-based ophthalmic procedures [12] , [13] ).…”

Development of Measurement and Calibration Techniques for Dynamic Pressures and Temperatures – Results and Achievements

“…In this project, KTH and RISE successfully extended the operational pressure range of shock tubes up to 40 MPa and 26 MPa, respectively. This was achieved by implementing a converging test section that smoothly transforms the incident plane shock into a spherical shock wave that converges, accelerates, and thereby amplifies its strength [5]. Numerical simulations predicting the pressure profile were developed and compared with the experimental profile (Figure 1).…”

Effect of the Dynamic Response of a Side-Wall Pressure Measurement System on Determining the Pressure Step Signal in a Shock Tube Using a Time-of-Flight Method

“…Therefore, V wall is usually extrapolated from the velocity distribution along the driven section determined using a time-of-flight (TOF) method. This method determines the shock wave velocity along the driven section using the times of the shock wave passages over the side-wall pressure sensors t i with the centers at locations x i along the driven section [ 30 , 31 , 32 , 33 , 34 ]. Considering the quadratic model for the variation of the shock wave velocity V ( x ) = ax 2 + bx + c , four side-wall pressure sensors are required to obtain the constants a , b and c by solving the system of three equations [ 34 ]: where i = 1–3.…”