1. Visualizing Detonation Diffraction Experiments: F. Pintgen, J.E.Shepherd Simulations: M. Arienti, R. Deiterding ASC RESEARCH REVIEWMAY 12-13 , 2004

2. Experimental Set up 2H2+O2+68%Ar subcritical:

3. Experimental Set up • Excimer pumped dye laser, 5mJ/pulse • ICCD camera, Gate width 40ns • Schlieren system light source: 50ns ruby laser pulse • PLIF and Schlieren image obtained within 100ns

4. Subcritical case Image-height 50mm Multiple shots with 6ms delay increase Straight portion of leading, still shock coupled, reaction front gradually decouples 2H2+O2+7Ar 1bar detonation centerline tube

5. Critical case shot 37 shot 38 2H2+O2+66%Ar, 1bar image-height: 150mm PLIF image taken 70ns after Schlieren image

6. critical case 2H2+O2+66%Ar 1bar image-height 50mm Keystone shaped reaction front features mainly pointing away from the axis of symmetry shot 37 shot 38 shot 40 shot 42

7. Comparison with simulation Keystone-shaped reaction front features mainly pointing away from the axis of symmetry. Contrast with “Classical” keystone in fully developed detonation R. Deiterding, PhD thesis, Brandenburgische Technische Universiät Cottbus, 2003 AMROC simulation 2H2+O2+70%Ar 10kPa l=16mm, D/l=8

8. Comparison with simulation image-height 130mm flow direction Reaction front propagating transversely into shocked but unreacted region • Marco Arienti: • Single step reaction • Perfect gas Equation of State • 6750 x 5858 grid points 2H2+O2+22%N2 100kPa qCJ = 6.8 Activation energy qCJ = 3.5

9. Future work • Extend experimental studies to more irregular mixtures, with higher activation energy • Measure experimentally decaying shock velocity to get a better quantitative comparison with simulations • Revisit tube fracture problem with visualization of fluid dynamics and focus on fluid-solid coupling