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Blast Testing Issues and TBI: Experimental Models That Lead to Wrong Conclusions.

Needham CE, Ritzel D, Rule GT, Wiri S, Young L - Front Neurol (2015)

Bottom Line: This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured.This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests.Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

View Article: PubMed Central - PubMed

Affiliation: Southwest Division, Applied Research Associates, Inc. , Albuquerque, NM , USA.

ABSTRACT
Over the past several years, we have noticed an increase in the number of blast injury studies published in peer-reviewed biomedical journals that have utilized improperly conceived experiments. Data from these studies will lead to false conclusions and more confusion than advancement in the understanding of blast injury, particularly blast neurotrauma. Computational methods to properly characterize the blast environment have been available for decades. These methods, combined with a basic understanding of blast wave phenomena, enable researchers to extract useful information from well-documented experiments. This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured. However, it is critical that the research community effectively overcomes the confusion that has been compounded by a misunderstanding of the differences between the loading produced by a free field explosive blast and loading produced by a conventional shock tube. The principles of blast scaling have been well established for decades and when properly applied will do much to repair these problems. This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests. Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

No MeSH data available.


Related in: MedlinePlus

Reflection factors (RF) as a function of the cotangent (Z) of the incident angle (a). The reflection factor is the ration of peak reflected overpressure (Pr0) to peak incident overpressure (Ps0) (11).
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Figure 7: Reflection factors (RF) as a function of the cotangent (Z) of the incident angle (a). The reflection factor is the ration of peak reflected overpressure (Pr0) to peak incident overpressure (Ps0) (11).

Mentions: One or two gauges on the test object are insufficient in the absence of computational fluid dynamics (CFD) simulations to fill in the gaps required to define loading over a complex shape such as human head fitted with a helmet. As pointed out earlier, the reflection factor for shock waves is not a monotonic function of the angle of incidence. Figure 7 shows the reflection factor for several incident pressure levels as a function of the cotangent of the incident angle. As the cotangent approaches zero (for a surface parallel to the blast wave), there is no reflection and the load is the incident overpressure. At large values of the cotangent, the reflection factor approaches that of a normal reflection. The enhancement in reflection factor near 45° is the result of the transition from regular reflection to Mach reflection (11).


Blast Testing Issues and TBI: Experimental Models That Lead to Wrong Conclusions.

Needham CE, Ritzel D, Rule GT, Wiri S, Young L - Front Neurol (2015)

Reflection factors (RF) as a function of the cotangent (Z) of the incident angle (a). The reflection factor is the ration of peak reflected overpressure (Pr0) to peak incident overpressure (Ps0) (11).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389725&req=5

Figure 7: Reflection factors (RF) as a function of the cotangent (Z) of the incident angle (a). The reflection factor is the ration of peak reflected overpressure (Pr0) to peak incident overpressure (Ps0) (11).
Mentions: One or two gauges on the test object are insufficient in the absence of computational fluid dynamics (CFD) simulations to fill in the gaps required to define loading over a complex shape such as human head fitted with a helmet. As pointed out earlier, the reflection factor for shock waves is not a monotonic function of the angle of incidence. Figure 7 shows the reflection factor for several incident pressure levels as a function of the cotangent of the incident angle. As the cotangent approaches zero (for a surface parallel to the blast wave), there is no reflection and the load is the incident overpressure. At large values of the cotangent, the reflection factor approaches that of a normal reflection. The enhancement in reflection factor near 45° is the result of the transition from regular reflection to Mach reflection (11).

Bottom Line: This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured.This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests.Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

View Article: PubMed Central - PubMed

Affiliation: Southwest Division, Applied Research Associates, Inc. , Albuquerque, NM , USA.

ABSTRACT
Over the past several years, we have noticed an increase in the number of blast injury studies published in peer-reviewed biomedical journals that have utilized improperly conceived experiments. Data from these studies will lead to false conclusions and more confusion than advancement in the understanding of blast injury, particularly blast neurotrauma. Computational methods to properly characterize the blast environment have been available for decades. These methods, combined with a basic understanding of blast wave phenomena, enable researchers to extract useful information from well-documented experiments. This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured. However, it is critical that the research community effectively overcomes the confusion that has been compounded by a misunderstanding of the differences between the loading produced by a free field explosive blast and loading produced by a conventional shock tube. The principles of blast scaling have been well established for decades and when properly applied will do much to repair these problems. This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests. Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

No MeSH data available.


Related in: MedlinePlus