Underwater Explosions Expansion S hock wave 1st bubble pulse gas - - PowerPoint PPT Presentation

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Underwater Explosions Expansion S hock wave 1st bubble pulse gas - - PowerPoint PPT Presentation

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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

slide-1
SLIDE 1

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 1

Underwater Explosions

S hock wave 1st bubble pulse gas globe Expansion

slide-2
SLIDE 2

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 2

Results 2008

Reference calculated from 5 charges without bubble curtain

1 kg charges

Attenuations of up to 16 dB could be achieved

slide-3
SLIDE 3

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 3

Results 2009

SEL

300 kg charges

No damping of pressure changes resulting from motion

  • f water displaced by

hot gas globe (low frequency phenomenon) Attenuation of peak pressure from very fast expanding gas sphere (faster than sound speed; high frequency phenomenon) by ~4 dB

slide-4
SLIDE 4

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 4

Experiments 2010

Mines: 300 kg „ S chießwolle 39“ S emicircular bubble curtain, r= 70 m, air flow 1 m3/min per m pipe Pressure sensors inside and outside b.c. (distance 45 m; 105 m), Hydrophones outside b.c.(distance 105 m)

slide-5
SLIDE 5

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 5

Results 2010

Pressure

Position P1, distance 45 m, depth 4 m

time (ms) 9,3 MPa 7,6 MPa 7,5 MPa

Literature Mine 3 Mine 4 Mine 5

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SLIDE 6

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 6

Results 2010

Position P3, distance 105 m, depth 3 m

Pressure time (ms) from 9,3 MPa

  • 19 dB att.
  • 7 dB TL

from 7,6 MPa

  • 6 dB att.
  • 7dB TL

from 7,5 MPa

  • 16 dB att.
  • 7 dB TL

Bubble curtain incompl ete

Literature Mine 3 Mine 4 Mine 5

slide-7
SLIDE 7

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 7

Results 2010

1/3 octave band spectra P3, distance 105 m, depth 3 m

SEL

Frequency (Hz)

Bubble curtain incomplete

Literature, Leq=215 dB Mine 3, Leq=197 dB Mine 4, Leq=204 dB Mine 5, Leq=196 dB

slide-8
SLIDE 8

Damping of S hock Waves

  • E. S

chmidtke MIREMAR 2010, Page 8

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 Leq ≥ 7 dB