Underwater Explosions Expansion S hock wave 1st bubble pulse gas globe E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 1
Results 2008 1 kg charges Reference calculated from 5 charges without bubble curtain Attenuations of up to 16 dB could be achieved E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 2
Results 2009 300 kg charges SEL No damping of pressure changes Attenuation of peak pressure from very fast resulting from motion expanding gas sphere (faster than sound speed; of water displaced by high frequency phenomenon) by ~4 dB hot gas globe ( low frequency phenomenon) E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 3
Experiments 2010 Mines: 300 kg „ S chießwolle 39“ S emicircular bubble curtain, r= 70 m, air flow 1 m 3 /min per m pipe Pressure sensors inside and outside b.c. (distance 45 m; 105 m), Hydrophones outside b.c.(distance 105 m) E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 4
Results 2010 Position P1, distance 45 m, depth 4 m Literature 9,3 MPa Mine 3 7,6 MPa Mine 4 7,5 MPa Mine 5 Pressure time (ms) E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 5
Results 2010 Position P3, distance 105 m, depth 3 m Literature from 7,6 MPa from 9,3 MPa Mine 3 - 6 dB att. -19 dB att. Mine 4 Mine 5 - 7dB TL -7 dB TL from 7,5 MPa Bubble -16 dB att. curtain incompl -7 dB TL ete Pressure time (ms) E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 6
Results 2010 1/3 octave band spectra P3, distance 105 m, depth 3 m Bubble curtain incomplete Literature, Leq=215 dB SEL Mine 3, Leq=197 dB Mine 4, Leq=204 dB Mine 5, Leq=196 dB Frequency (Hz) E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 7
S ummary •S uccessful trial with bubble curtain •Attenuation of peaks ≥ 16 dB • Attenuation 1/3 octave bands (>500Hz) ≥ 5 dB (compared to trial with incomplete bubble curtain) •Attenuation L eq ≥ 7 dB E. S chmidtke Damping of S hock Waves MIREMAR 2010, Page 8
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