The Mach Stem

If the explosion occurs above the ground, when the expanding blast wave strikes the surface of the earth, it is reflected off the ground to form a second shock wave. This reflected blast wave can merge with the incident shock wave. This merging phenomenon is called the ”Mach effect” . The overpressure at the front of the Mach wave is generally about twice as great as that at the direct blast wave front. This footage is from a conventional explosion.