Computational Ocean Acoustics - MIT OpenCourseWare · PDF file•SEALAB Passive and Active Sonar Simulator. ... Passive Sonar ¾sealab –p Active Sonar ... 13.853 COMPUTATIONAL...

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

Computational Ocean Acoustics

• Ray Tracing• Wavenumber Integration• Normal Modes• Parabolic Equation

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

Normal Modes• Modes for Range-Dependent Envir.

– Coupled Modes (5.9)– One-way Coupled Modes– Adiabatic Modes– SEALAB Propagation Modeling Environment

• Modes in 3-D Environments– Continuously coupled modes– Adiabatic Approximation– 3-D Propagation in 2-D Environments– General 3-D Modal Propagation Framework

• SEALAB Passive and Active Sonar Simulator

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

Simulation and Stimulationof Sonar Signal Processing Frameworks

Real Expt

SEALABSIM/STIM

Data Collection

SignalProcessing

Detection/Classification

Display

InversionPassive

Tomography

ModalDatabase

Steering Vectors

EnvironmentalDatabase

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

SEALABGraphical User

Interface

FilterModeling HeuristicsData files - Scripts

Legacy CodesWave-theory Acoustic models

Source/Receiver DynamicsSpatial variability

Temporal Variability

SEALAB Architecture

Graphics

Signal Processing

Sources: NATO SACLANT lab, MITSources: NATO SACLANT lab, MIT

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

SEALABMIT OE Acoustics Computing Environment

#!/usr/csh## SEALAB Environment#setenv SEALAB_ROOT /keel0/henrik/Vasa/Sealabsetenv SCRIPTS ${SEALAB_ROOT}/scriptssetenv SEALAB_BIN ${SEALAB_ROOT}/util/binsetenv MCM_BIN "${SEALAB_ROOT}/mcm/bin"setenv MODEL_BIN "${SEALAB_ROOT}/model/bin"setenv PASSIVE_BIN "${SEALAB_ROOT}/pas/bin"setenv ACTIVE_BIN "${SEALAB_ROOT}/act/bin"## OASES and CSNAP environment#setenv OASES_ROOT /keel0/henrik/Oasessetenv OASES_SH $OASES_ROOT/binsetenv OASES_BIN $OASES_ROOT/bin/i386-linux-linuxsetenv OASES_LIB $OASES_ROOT/lib/i386-linux-linux setenv CON_BWCOL COLsetenv CON_PACKGE MTVsetenv CON_DEVICE X11## OASES3D #setenv SCATT_BIN /keel0/henrik/Scatt/bin/i386-linux-linux#set path=( . $SEALAB_BIN $ACTIVE_BIN $PASSIVE_BIN $MODEL_BIN \

$MCM_BIN $SCRIPTS $OASES_SH $OASES_BIN $SCATT_BIN $path)## MTV environment#setenv MTV_WRB_COLORMAP "ON"setenv MTV_COLORMAP jetsetenv MTV_PSFONT helveticasetenv MTV_PRINTER_CMD "lpr"setenv MTV_PSCOLOR "ON"## PRINTER#setenv PRINTER lp1

SEALAB Initialization on Linux boxes:

source /keel0/henrik/Vasa/Sealab/scripts/slbinit

Running SEALAB

Transmission Loss

sealab –t

Passive Sonar

sealab –p

Active Sonar

sealab –a

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

SEALAB

Propagation Modeling

Courtesy Vasa Associates. Used with permission.

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

Courtesy Vasa Associates. Used with permission.

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

SEALAB

Propagation Modeling

Courtesy Vasa Associates. Used with permission.

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

SEALAB

Propagation Modeling

Courtesy Vasa Associates. Used with permission.

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

[See Jensen Fig. 5.19a]

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

Solution Techniques• Ray tracing• Parabolic Equation• ‘Layer Method’ – Direct Global Matrix

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

xmk1xmkj

Eigenvalue Problem Independent of kyrmk1 rmkj

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

xmk

x(m-1)k

x(m+1)k1

1

1

xmk

x(m+1)kj

j

x(m-1)kj

kx

Evanescent Modes

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

x;mk

x;m-1k

x;m+1k1

1

1

x;mk

x;m+1kj

j

x;m-1kj

kx

Only difference for 3D

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

x;mk

x;m-1k

x;m+1k1

1

1

x;mk

x;m+1kj

j

x;m-1kj

kx

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

y

x

xj-1 jx xj+1

Sectorj

x

yk

yk

x;mk

x;m-1k

x;m+1k1

1

1

x;mk

x;m+1kj

j

x;m-1kj

kx

COMPUTATIONAL OCEAN ACOUSTICS13.853 Lecture 15

3-D Modal Modeling Framework

3-D Ocean Environment Range-Independent Sectors

[See Jensen Fig 5.19b][See Jensen Fig 5.19a]

Computational Procedure

1. Pre-compute modes for all sectors2. Each source-receiver combination

• Horizontal ray tracing, all mode combinations

• Local single-scattering approximation in plane geometry

• Approximate accounting for geometric spreading r-1/2