Simulation of the Effects of an Air Blast Wave - ELSA - Europa

2.2.3 ImpulseThe impulse of the air blast wave has a big influence on the response of the structures. The impulseis defined here as the area under the pressure time curve with the unit of pressure*sec. The impulsecan be calculated with (Kinney [15])0.067 1 + ( Z / 0.23)I =2 34Z 1 + ( Z /1.55)4(6)Another possibility is the polynomial equation of Kingery [14]. The comparison of the impulseresulting from both equations shows that the equation of Kinney simplifies the curve of the impulsebetween a scaled distance of 0.5 and 1.5 m/kg 1/3 .800600impulse [Pa sec]400200KinneyKingery00 0.5 1 1.5 2 2.5 3scaled distance [m/kg 1/3 ]Figure 4: Different equations for the impulse (Kinney [15] and Kingery [14])2.2.4 Negative PhaseDetonations produce an overpressure peak, and afterwards the pressure decreases and drops belowthe reference pressure (generally the atmospheric pressure). The influence of the so-called negativephase depends on the scaled distance. For scaled distances Z larger than 20 and especially for Zlarger than 50 the influence of the negative phase can not always be neglected. The size of thepositive impulse and of the negative impulse is then nearly the same. If the structure can react11