The NOBEL Code

In this chapter the advanced ASCI computer codes, NOBEL/SAGE/RAGE, for modeling compressible fluid dynamics are described. The detonation physics described in Chapters 1 through 4 of this book has been included into the NOBEL code. 

As described in reference 1 and Appendix D, the three-dimensional partial differential equations for nonviscous, nonconducting, compressible fluid flow are 

The overhead associated with the CMAR technique is about 20% of the total runtime, which is small compared to the gains of using CMAR instead of a uniform mesh. 

Much larger computational volumes, times and differences in scale can be simulated than is possible using previous Eulerian techniques such as those described in Appendices C and D. 

The original code is called SAGE. A later version with radiation is called RAGE. A recent version with the techniques for modeling reactive flow described in Chapters 1 through 4 is called NOBEL and was used for modeling many problems in detonation physics some of which are described later in this chapter. 

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Modeling of corner turning using the NOBEL code is described in Chapter 6, Figures 6.50 and 6.51, and in the Powerpoint NOBEL.PPT on the CD-ROM in the /NOBEL/BUNOBEL directory. Animations are on the CD-ROM in the /MOVIE/CORNER.MVE directory. 

The numerical model used to interpret cylinder wall expansion experiments must include a realistic description of build-up of detonation, Forest Fire burn and resulting detonation wave curvature. A problem in numerical simulation of long cylinders of explosive confined by thin metal walls is to obtain sufficient numerical resolution to describe the explosive burn properly and also to follow the simulation of long cylinders. The NOBEL code includes the necessary physics and will numerically model cylinder tests as described in Chapter 6. 

Animations of jet penetrations of inerts and explosives modeled using the NOBEL code are on the CD-ROM in the MOVIE directory as follows ... 

Figure 5.53 The pressure and mass fraction contours at various times for a hemispherical initiator of 0.635 cm radius PBX-9407 surrounded by 0.635 cm of PBX-9404 initiating PBX-9502 (X0290). The pressure contour interval is 50 kbar and the mass fraction contour interval is O.f. The calculation was performed using the TDL code. A calculation using the NOBEL code is on the CD/ROM in the /MOVIE/DET.MVE directory.

Douglas Venable developed the X-Ray machine PHERMEX and applied it to many problems of shock and detonation wave physics in the 1960 s. In this chapter we will use the NOBEL code to model some of his classic PHERMEX experimental observations of Munroe jets. Most of our current understanding and modeling of detonation wave corner turning depends upon the PHERMEX experiments of Venable. 

In the mid 1960 s, B. G. Craig at the Los Alamos National Laboratory performed experiments designed to characterize the formation of water waves from explosives detonated near the water surface. He reported observing the formation of ejecta water jets above and jets or roots below the expanding gas cavity. This was unexpected and a scientific mystery which remained unsolved until it was finally modeled using the NOBEL code in December of 2002. 

The NOBEL code has been used to model the experimental geometries of Sonett and of Craig. The experimental observations were reproduced as the atmospheric pressure was varied as described in reference 14. 

The cavity, water ejecta and water surface profiles shown in the PHERMEX radiography in Figure 6.20 were closely approximated by the compressible hydrodynamic modeling described in reference 15 using the 2DE code and in Figure 6.21 using the NOBEL code. 

Explosive interfaces or defects such as cracks will result in Munroe jets which can cause significant damage to adjacent metals. The Munroe jets formed by etchings on explosive surfaces can result in remarkable sketches such as the metal plate image of Alfred Nobel made during his lifetime shown in Figure 6.34. The NOBEL code described in this chapter uses the Nobel image as its symbol. 

Until the development of the NOBEL code, it was not possible to numerically model small gaps with the resolution needed. The NOBEL initial geometry and the plate dent are shown in Figure 6.37. 

The HOM equation of state described in Appendices A, B, C and E is used by the NOBEL code to generate the required equation of state tables. The table generation assumes that slopes near the minimum and maximum pressures of the HOM equation of state can be used to generate higher and lower pressures in the tables. The NOBEL code uses the Los Alamos SESAME tables for non-reactive materials when needed. 

The results of using the NOBEL code with build-up to and of detonation for a 2.54 cm thick slab and a 2.54 diameter cylinder of PBX-9501 are shown in Figure 6.45. 

The experiment was modeled using the NOBEL code with the Multiple-Shock Forest Fire option for build-up to detonation and including build-up of detonation. The density, pressure and mass fraction contours are shown in Figure 6.48 for Shot 1697. 

The modeling of insensitive high explosive initiators using the 2DL, 2DE and 3DE codes is described in Chapter 5, section 5.8. While the build-up to detonation process was described using Forest Fire, it was not possible to also investigate the build-up of detonation until the development of the NOBEL code described in this chapter. 

A detonator for PBX-9502 was studied using proton radiography at the PRad facility. It consisted of a 0.4 cm radius hemisphere of PBX-9407 initiated with a bridge wire which initiated a 1.5 cm radius hemisphere of LX-07 that then initiated PBX-9502, leaving a large region of undecomposed PBX-9502. The build-up to and of detonation was modeled using the NOBEL code. A 0.5 cm thick Dural plate was located 2.7 cm from the center of the detonator. 

The August 27, 1883 Krakatoa hydrovolcanic explosion was modeled using the NOBEL code in references 1 and 19. 

The revolution in numerical modeling has been made possible by the development of the multi-material adaptive grid Eulerian codes SAGE/NOBEL/RAGE with models to describe the build-up to detonation using the Forest Fire heterogeneous shock initiation burn model and models to describe the build-up of detonation which results in factors of two variations in the explosion energy with time. The build-up to and of detonation was first modeled in 2002 by the NOBEL code. 

The CD-ROM has been revised to include PowerPoint programs for each of the Chapters of the book and the remarkable advances that occurred since 2000 as a result of the development of the NOBEL code. The complete PDF files for the seven Los Alamos Data Volumes are included on the CD-ROM along with the recently published Russian Shock Wave Data generated between 1949 and 2000 by their Federal Nuclear Centers. The FORTRAN codes along with the executable codes for Windows 95, 98, ME, XP and VISTA operating systems are on the CD-ROM. The FORTRAN codes along with the executable codes for the OS X operating system on the Apple IMAC computer are also on the CD-ROM. 

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