OVERVIEW

The objective of this module is to provide students with an understanding of the basic principles of radar, sonar, magnetic and infrared measurement systems, and how they interact with ships, especially in relation to the acoustic emission and electromagnetic response.

AIMS AND CONTENT

LEARNING OUTCOMES

The student will possess the ability to understand an evaluation of the underwater noise, radar response, infrared emission and magnetic signature and of a ship, and to reason about the causes that govern them.

AIMS AND LEARNING OUTCOMES

The module aims to provide students with a general understanding of the concepts of underwater noise, infrared emission, radar response and magnetic signature of a ship and the mechanisms that govern them. Upon completion of the module, the student will be able to:

• describe the basic principles of ship acoustic and electromagnetic signatures;
• understand the impact assessments of said signatures, especially in relation to the probability of detection of the ship;
• analyze operation and purpose of radar and sonar systems;
• solve simple design problems related to the signatures mentioned above.

PREREQUISITES

No additional knowledge and skills are required beyond those of students admitted to the Master of Science in Naval Engineering.

TEACHING METHODS

Classroom lectures and of case studies' description, often with the support of slides provided to students in advance, as well as visits to department laboratories and seminars by industrial experts. Attendance at all these activities is recommended.

SYLLABUS/CONTENT

ACOUSTIC SIGNATURE

• Introduction: underwater acoustic noise, conversion efficiency: vibration, transmission, radiation.
• Spectrum of a signal: Fourier transform; periodic signals and Fourier series; random signals; stationarity; autocorrelation and power spectral density.
• Acoustic waves in fluids: nature of waves, wave equation, plane waves and spherical waves, acoustic impedance, intensity and power, decibel measurements.
• Propagation losses: geometric spreading, medium absorption, transmission loss for spherical waves, sound velocity profile, acoustic ray tracing, ray trajectory curvature.
• Passive sonar equation: quantities involved, signal-to-noise ratio, expected performance, ambient acoustic noise, relation with ship acoustic signature.
• Radiated noise: monopole, dipole, quadripole; efficiency, directivity, examples; propeller tonal radiation and singing.
• Cavitation: general aspects and types; propeller cavitation; calculation models; surface and submersible vessels.
• Flexural vibration: mechanical noise generation; vibration transmission; vibration radiation.
• Flow noise: origin, radiation, interactions.
• Summary of noise sources: relative importance; effect of velocity; radiated acoustic power; calculation of radiated noise level.
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ELECTROMAGNETIC SIGNATURES

• Introduction and basic concepts of electromagnetic fields: field vectors and sources, Maxwell's equations.
• Electromagnetic fields in materials: constitutive equations and dispersion.
• Electromagnetic waves: propagation and radiation.
• Fundamental concepts of antennas and main types of antennas used in shipbuilding.
• Radar: principles of operation and resolution.
• Radar equation and range calculation.
• Radar cross section and radar signatures in the naval field.
• Electromagnetic emission: blackbody radiation, elements of Planck's laws, Stefan-Boltzmann, Wien.
• IR imaging and infrared signatures in the naval domain.
• Magnetic signatures: main sources of signatures (ferromagnetic materials and magnetization, eddy currents, mention of corrosion effects), models for prediction.
   

RECOMMENDED READING/BIBLIOGRAPHY

D. ROSS, Mechanics of Underwater Noise, Peninsula Publishing, 1987

R. J. URICK, Principles of Underwater Sound, 3rd edition, McGraw-Hill, 1983

X. LURTON, An Introduction to Underwater Acoustics, Principles and Applications, Second Edition, Springer-Praxis, 2010.

M. SKOLNIK, Introduction to radar systems, 3rd ed., McGraw-Hill, 2001.

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

https://corsi.unige.it/8738/p/studenti-orario

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

Oral test on the topics covered in the classroom lectures, laboratory and any industrial seminars. Students with specific learning disorders will be allowed to adopt specific modalities and supports that will be determined on a case-by-case basis, in agreement with the Engineering Course Delegate in the Commission for the Inclusion of Students with Disabilities.

ASSESSMENT METHODS

The oral test will assess the ability to describe the principles governing acoustic and electromagnetic wave fields, the different signatures of the ship, and the operation of radar and sonar systems, discussing the relative importance of the various sources in relation to the ship. It will also assess the technical language and the ability to analyze simple practical problems, reasoning with autonomy and rigour.