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

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3 Numerical Loading of a Structure with Air Blast WavesThere are several ways of numerical modelling in order to load a structure with an air blast wave.These methods differ in the number of used elements and with them in the calculation time.• Model with the mechanical modelling of the explosive (JWL-equation (15)). A fine mesh isessential to get realistic results. The size of the element in the range around the explosive shouldbe approximately 1 mm. These calculations are very expensive. To reduce the computation timepartitioning can be used. This method reduces the calculation time for models with a largevariation of element sizes.• The method proposed by Clutter [9] is also a solid TNT model and uses only one element forthe explosive. This is possible by different not specified methods in combination with theBecker-Kistiakowsky-Wilson EOS for the explosive.• 1D to 3D. This modelling is proposed in [4] and is also a solid TNT model. A 1D calculation isused until the wave reaches a surface. Then the values of the density, energy, velocity andpressure are mapped into the 3D mesh. Rose [20] maps the 1D model to 2D when the wavearrives the first surface and maps the 2D model to 3D when the wave arrives a second surfacewith another direction. EUROPLEXUS allows the implementation of this method. The methodshould also be validated with a calculation of the first model. The model is a mixture of the firstand the third model. The calculation time should be larger than for the second model.• Model with a compressed bubble. The pressure-time function resulting from a compressedbubble can not easily match the curve of an air blast wave. The size of the compression can becalibrated with the maximum pressure or the impulse. The calculation time is smaller than forthe first model.• Control volume. A volume around the explosive is loaded by a pressure-time curve. Thispressure time curve can be calculated with a model based on the modelling of the explosive.Alternatively, the well known curves from Kingery [14] can be used. This method should bevalidated through comparisons with calculations of the first model. The computation time is inthe range of the second model.• Load-time function. This is only usable for an estimation of the behaviour of a structure loadedby an air blast wave. The structure is loaded by a load-time function built with the pressure-timefunction e.g. from Kingery [14]. This function is implemented in EUROPLEXUS (see chapter7). The calculation is relatively inexpensive. Alternatively, the pressure-time function can be18
determined with a fluid pre-calculation with fixed boundaries for the structure. The structure isthen loaded by the pressures resulting from this fluid calculation.The choice among these methods depends on the scope of the analysis and on further investigationsabout their advantages and shortcomings. Figure 9 shows different models for the simulation of anair blast wave.Solid TNTCompressed bubbleLoad on a control volumeLoad-time functionFigure 9: Several models for air blast wave simulations19
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: the specific heat ratio and the spe
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 and 30: 5.0E+094.0E+09EUROPLEXUS x=0.105EUR
Page 31 and 32: Cased pyr /d ex,in /d ex,end /d air
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
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*Cube intermediaire (centre=o0 et a
Page 86:
The mission of the JRC is to provid
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