A Model of Piston Sliding Process for a Double Piston-Actuated Shock Tube

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
I. da S. Rêgo ◽  
T. Ando ◽  
K. Misumi ◽  
T. Miyazaki ◽  
S. Nishiyori ◽  
...  
Keyword(s):  
Shock Tube ◽  
Pressure Ratio ◽  
Motion Equation ◽  
Simplified Model ◽  
Shock Tubes ◽  
Model Based

A double piston-actuated structure designed for replacing the use of diaphragms in conventional shock tubes has been recently developed. In order to clarify the piston sliding process for this structure, a simplified model based on the motion equation of its main sliding piston has been developed. Calculated piston sliding time against pressure ratio has been numerically obtained and indirectly evaluated by examining the experimental curves of the performance of the diaphragmless structure.

Shock Tube Simulation of the Transient Surge Phase Inside an Axial Compressor

2018 ◽  
Author(s):  
Paul Xiubao Huang ◽  
Robert S. Mazzawy
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
High Speed ◽  
Transient Flow ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Dynamic Effect ◽  
Initiation Site ◽  
Flow Reversal ◽  
Expansion Waves

This paper is a continuing work from one author on the same topic of the transient aerodynamics during compressor stall/surge using a shock tube analogy by Huang [1, 2]. As observed by Mazzawy [3] for the high-speed high-pressure (HSHP) ratio compressors of the modern aero-engines, surge is an event characterized with the stoppage and reversal of engine flow within a matter of milliseconds. This large flow transient is accomplished through a pair of internally generated shock waves and expansion waves of high strength. The final results are often dramatic with a loud bang followed by the spewing out of flames from both the engine intake and exhaust, potentially damaging to the engine structure [3]. It has been demonstrated in the previous investigations by Marshall [4] and Huang [2] that the transient flow reversal phase of a surge cycle can be approximated by the shock tube analogy in understanding its generation mechanism and correlating the shock wave strength as a function of the pre-surge compressor pressure ratio. Kurkov [5] and Evans [8] used a guillotine analogy to estimate the inlet overpressure associated with the sudden flow stoppage associated with surge. This paper will expand the progressive surge model established by the shock tube analogy in [2] by including the dynamic effect of airflow stoppage using an “integrated-flow” sequential guillotine/shock tube model. It further investigates the surge formation (characterized by flow reversal) and propagation patterns (characterized by surge shock and expansion waves) after its generation at different locations inside a compressor. Calculations are conducted for a 12-stage compressor using this model under various surge onset stages and compared with previous experimental data [3]. The results demonstrate that the “integrated-flow” model closely replicates the fast moving surge shock wave overpressure from the stall initiation site to the compressor inlet.

Use of Shock Tubes for Blast Testing

2013 ◽  
Author(s):  
Chong Whang ◽  
Warren Chilton ◽  
Philemon Chan
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Laboratory Method ◽  
Physical Models ◽  
Test Model ◽  
Shock Tubes ◽  
Cfd Simulations ◽  
Data Comparison ◽  
Blast Overpressure ◽  
Blast Testing

A computational fluid dynamics (CFD) study was carried out with data comparison to provide guidance for the control of open shock tube wave expansion to simulate field blast loadings for the conduct of biomechanical blast overpressure tests against surrogate test models. The technique involves the addition of a diffuser to the shock tube to prevent overexpansion before the shock wave impacts the test model. Mild traumatic brain injury (mTBI) has been identified as the signature injury for the conflicts in Iraq and Afghanistan, and blast overpressure from improvised explosive devices (IEDs) has been hypothesized as a significant mTBI risk factor. Research in the understanding of the mechanism of blast induced mTBI has been very active, which requires blast testing using animal and physical models. Full scale field blast testing is expensive. The use of shock tubes is clearly a viable cost effective laboratory method with many advantages. CFD simulations with data comparison show that without a diffuser, the shock wave exiting the tube tends to over expand producing an incident waveform with a short positive duration followed by a significant negative phase that is different from a Friedlander wave. However, the overexpansion effects can be mitigated by a diffuser. Shock tube tests also support the simulation results in which a diffuser improves the waveform from the shock tube. CFD simulations were validated by shock tube tests.

scholarly journals On the formation of Friedlander waves in a compressed-gas-driven shock tube

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150611 ◽  
Author(s):  
Abiy F. Tasissa ◽  
Martin Hautefeuille ◽  
John H. Fitek ◽  
Raúl A. Radovitzky
Keyword(s):  
Shock Tube ◽  
Analytical Model ◽  
Blast Waves ◽  
Rational Approach ◽  
Initial Structure ◽  
Shock Tubes ◽  
Rarefaction Waves ◽  
Wave Interactions ◽  
Compressed Gas ◽  
Volume Method

Compressed-gas-driven shock tubes have become popular as a laboratory-scale replacement for field blast tests. The well-known initial structure of the Riemann problem eventually evolves into a shock structure thought to resemble a Friedlander wave, although this remains to be demonstrated theoretically. In this paper, we develop a semi-analytical model to predict the key characteristics of pseudo blast waves forming in a shock tube: location where the wave first forms, peak over-pressure, decay time and impulse. The approach is based on combining the solutions of the two different types of wave interactions that arise in the shock tube after the family of rarefaction waves in the Riemann solution interacts with the closed end of the tube. The results of the analytical model are verified against numerical simulations obtained with a finite volume method. The model furnishes a rational approach to relate shock tube parameters to desired blast wave characteristics, and thus constitutes a useful tool for the design of shock tubes for blast testing.

scholarly journals Irregularity and decadal variation in ENSO: a simplified model based on Principal Oscillation Patterns

2014 ◽  
Vol 43 (12) ◽  
pp. 3327-3350 ◽  
Author(s):  
Maria Gehne ◽  
Richard Kleeman ◽  
Kevin E. Trenberth
Keyword(s):  
Simplified Model ◽  
Decadal Variation ◽  
Model Based
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