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

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lengthExplosiveopeningxd pyrad ex,in d ex,endd air,ind air,endFigure 19: 3D simplified model with hexahedrons or tetrahedronsAlternatively four tetrahedral elements can be used instead of one hexahedral element. This resultsin a higher number of elements. The meshing can be done with scripts that convert the hexahedronsin tetrahedrons. These scripts are presented in [7]. The script pxhex2te converts the hexahedrons intetrahedrons; the script pxqua2tr converts the quadrangles to triangles (necessary for the surfaces).For the simulation a model is used which has in most cases a TNT charge of a volume of 8000 cm 3 ,accordingly a cube of 20 x 20 x 20 cm or a sphere with radius of 12.4 cm. The mass of this chargeis 12.8 kg. An ALE-calculation is used for all further investigations. The explosive is build as anEulerian mesh, the air is build as an ALE mesh.The symmetry at the surfaces can be considered by defining symmetry planes with the CONTSPLA AUTO command. This command defines symmetry conditions orthogonal to the surface ofthe defined nodes. Another possibility is the definition with the FSR-command as a sliding surface.Both methods give the same results.The calculations performed with the conical model are summarized in Table 4 and shortly describedhereafter.30
Cased pyr /d ex,in /d ex,end /d air,in /d air,end opening/ Charge Element type t endlengthCON1 0.05/0.05/0.08/0.2/0.2 0.2/4.0 12.8 FL34 (NF34) 4.0e-3CON2 0.01/0.02/0.02/0.02/0.05 0.2/4.0 12.8 FL34 (NF34) 4.0e-3CON3 0.008/0.01/0.01/0.01/0.05 0.1/4.0 12.8 FL34 (NF34) 4.0e-3CON4 0.008/0.005/0.005/0.005/0.02 0.03/1.3 12.8 FL34 (NF34) 4.7e-4CON5 0.008/0.005/0.005/0.005/0.02 0.03/1.3 12.8 FL35/FL38 4.7e-4CON6 0.002/0.002/0.002/0.002/0.01 0.01/1.3 12.8 FL35/FL38 4.7e-4CON7 0.001/0.001/0.001/0.001/0.005 0.01/1.3 12.8 FL35/FL38 4.7e-4CON8 0.001/0.001/0.001/0.001/0.01 0.05/3.0 12.8 FL35/FL38 1.5e-3CON9 0.001/0.001/0.001/0.001/0.01 0.05/3.0 1.0 FL35/FL38 1.5e-3CON10 0.001/0.001/0.001/0.001/0.005 0.05/3.0 1.0 FL35/FL38 1.5e-3CON11 0.0005/0.0005/0.0005/0.0005/0.01 0.025/1.5 1.0 FL35/FL38 1.5e-3CON12 0.005/0.001/0.001/0.001/0.01 0.1/3.0 1.0 FL35/FL38 1.5e-3CON13 0.005/0.001/0.001/0.001/0.04 0.2/3.0 1.0 FL35/FL38 1.5e-3CON14 0.005/0.001/0.001/0.001/0.02 0.2/1.5 1.0 FL35/FL38 1.5e-3CON20 0.0002/0.0001/0.001/0.001/0.005; 6.5e-3/0.4 1.0 FL35/FL38 7.0e-5Table 4: Calculations with a conical meshCON1This calculation uses the modified tetrahedral elements (see [7]) also for the tip of the model. Themesh is relatively coarse. The development of the air pressure wave is presented in Figure 20. Thepressure-time curve for a distance of 1 m shows the increase of the pressure until a value of1.83 10 6 Pa (time step size for evaluation 2 10 -6 sec) which is equivalent to 18.3 times theatmospheric pressure. The resulting pressure does not depend on the time step size for theevaluation. By choosing every calculated time step for the evaluation (1.75 10 -7 sec) the maximumpressure is also 1.830958 10 6 Pa. After the pressure peak the pressure is decreasing up to 232.2 Pa.This value of the “negative” pressure is relatively high. The pressure-time curve for other distancesfollows also these trends.31
Page 1 and 2: Simulation of the Effectsof an Air
Page 3 and 4: Distribution ListLechner S.Anthoine
Page 5 and 6: 1 IntroductionThis work is being co
Page 7 and 8: • Far zone. The blast wave result
Page 9 and 10: Figure 2: Model of Kingery [14] wit
Page 11 and 12: 2.2.3 ImpulseThe impulse of the air
Page 13 and 14: Figure 5: Different parameters for
Page 15 and 16: 250200Impulse from KingeryImpulse w
Page 17 and 18: the specific heat ratio and the spe
Page 19 and 20: determined with a fluid pre-calcula
Page 21 and 22: From this asymptotic form it can al
Page 23 and 24: 2.0E+101.6E+10without burn mass fra
Page 25 and 26: Case opening d pyra d ex,in d ex,en
Page 27 and 28: Pressure [Pa]2.4E+102.0E+101.6E+101
Page 29: 5.0E+094.0E+09EUROPLEXUS x=0.105EUR
Page 33 and 34: Figure 21: Comparison of a coarse w
Page 35 and 36: CON9This model has approximately th
Page 37 and 38: 4E+7Max. pressure [Pa]3E+72E+7Kinge
Page 39 and 40: Case Size of the model Description
Page 41 and 42: CUB4This model uses a finer mesh th
Page 43 and 44: 6. Complete the volumes by adding t
Page 45 and 46: Figure 33: Maximum pressures versus
Page 47 and 48: experimental values is obtained wit
Page 49 and 50: 4.6.3 Arrival TimeThe arrival time
Page 51 and 52: value in [13]). These results show
Page 53 and 54: Modell airl bBubbleBubbleBubbleTNT
Page 55 and 56: Several calculations are done with
Page 57 and 58: 3. Calculation of the factor α bub
Page 59 and 60: quadratic. Therefore, the size of t
Page 61 and 62: 400Impulse [Pa sec]300200.Kingery 5
Page 63 and 64: 5 = hemispherical detonation (half
Page 65 and 66: 9 References[1] Alia, A.; Souli, M.
Page 67 and 68: 10 Apendix10.1 EUROPLEXUS Codedyms.
Page 69 and 70: CALLMECVAL(GET_FMT(6),NEWMAT%MATVAL
Page 71 and 72: 10.2 Miscellaneous codeairblastresu
Page 73 and 74: else{ //Kingerydouble t=log10(z);do
Page 75 and 76: maxar=0;REPE I0 (NBEL vges);ar = as
Page 77 and 78: *defining the surfaces around the a
Page 79 and 80: lpyr1 = p1 d ppy2;lpyr2 = p1 d ppy3
Page 81 and 82:
lpyr2 = p1 d ppy3;lpyr3 = p1 d ppy4
Page 83:
*Cube intermediaire (centre=o0 et a
Page 86:
The mission of the JRC is to provid
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Simulation of the Effects of an Air Blast Wave - ELSA - Europa

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