Experimental study of shock wave strengthening by a positive density gradient in a cryogenic shock tube

Richtmyer–Meshkov (RM) instability is regarded as a central role for understanding the hydrodynamic processes involved in inertial confinement fusion, supersonic combustion and supernova explosion. Because of its academic implication and engineering applications, the RM instability has received much attention since it was proposed. As an important tool for studying RM instability, shock tube experiment on shock–fluid interface interaction has been widely adopted and great progress has been achieved in past decades. The generation of a shock wave, the formation of an initial interface and the diagnostic of flow field are the three elements for studying the RM instability experimentally. This review surveys the advances in experimental investigations of RM instability in shock tube environment. Originating from a simple configuration as a planar shock interacting with a simple perturbed interface, the experimental study of RM instability approaches more complex situations like a convergent shock with a simple interface, or a planar shock with a complex interface. It is then expected that the experimental study on the real circumstance may be realized by using a complex shock with a complex interface. Finally, we propose the following issues for future study: (1) evolution of the RM instability induced by cylindrically converging shock waves; (2) effect of the three dimensions on the RM instability; (3) interaction of perturbed shock wave with an initially uniform or perturbed interface; and (4) formation and mixing mechanism of the compressible turbulence in the final stage of the RM instability.

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Experimental study of the nonstationarity of the interaction of a shock wave with a boundary layer

Известия Российской академии наук Механика жидкости и газа ◽

10.31857/s056852810002307-8 ◽

2018 ◽

pp. 105-115

Author(s):

Xyaolin Lyu ◽

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Sikhe Yi ◽

Khaibo Nyu ◽

Ksinkhey Chzhao ◽

...

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Experimental Study

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Factors Contributing to Increased Blast Overpressure Inside Modern Ballistic Helmets

Applied Sciences ◽

10.3390/app10207193 ◽

2020 ◽

Vol 10 (20) ◽

pp. 7193

Author(s):

Maciej Skotak ◽

Jonathan Salib ◽

Anthony Misistia ◽

Arturo Cardenas ◽

Eren Alay ◽

...

Keyword(s):

Experimental Study ◽

Shock Tube ◽

Principle Component Analysis ◽

Hot Spots ◽

Shape Factor ◽

Elevated Pressure ◽

Focal Points ◽

Parietal Region ◽

Blast Overpressure ◽

Pressure Fields

This study demonstrates the orientation and the "shape factor" have pronounced effects on the development of the localized pressure fields inside of the helmet. We used anatomically accurate headform to evaluate four modern combat helmets under blast loading conditions in the shock tube. The Advanced Combat Helmet (ACH) is used to capture the effect of the orientation on pressure under the helmet. The three modern combat helmets: Enhanced Combat Helmet (ECH), Ops-Core, and Airframe, were tested in frontal orientation to determine the effect of helmet geometry. Using the unhelmeted headform data as a reference, we characterized pressure distribution inside each helmet and identified pressure focal points. The nature of these localized “hot spots” is different than the elevated pressure in the parietal region of the headform under the helmet widely recognized as the under-wash effect also observed in our tests. It is the first experimental study which indicates that the helmet presence increased the pressure experienced by the eyes and the forehead (glabella). Pressure fingerprinting using an array of sensors combined with the application of principle component analysis (PCA) helped elucidate the subtle differences between helmets.

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