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Naval Architecture & Ocean Engineering
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EN455: Seakeeping and Maneuvering

Catalog Description

EN455: Seakeeping and Maneuvering (2-2-3)

The course is senior-level course covering topics in seakeeping and maneuvering. Topics covered include linearized motion of a ship in waves, including introduction to regular wave theory and a statistical representation of irregular waves. Heave, pitch, and roll motions are investigated using experiments and simulation. Seakeeping considerations in design are discussed. Topics in maneuvering include linearized equations of motion, maneuvering hydrodynamic derivatives, and turning ability. Experimental hydrodynamic derivatives are used to determine the controls-fixed directional stability and turning radius of a ship model.

Textbook

  • Seakeeping: Ship Behavior in Rough Water (Lloyd, 1998)
  • Principles of Naval Architecture: Volume III (Lewis, 1988)

Goals

  1. Apply the theory of linear wave superposition to represent irregular waves. Identify an appropriate wave spectra for describing different sea conditions. Calculate the encounter frequency for a ship.
  2. Perform a discrete Fourier transform on irregular wave data to determine the amplitudes and frequencies of the component waves.
  3. Identify the assumptions of linear strip theory and determine appropriate conditions for applying the theory.
  4. Generate the response amplitude operator (RAO) for the roll, heave, and pitch motions of a specific ship from experimental measurements. Evaluate the expected roll response for a ship given the dominant wave frequency or period, the ship’s roll RAO, the ship’s heading with respect to the waves, and ship’s speed.
  5. Determine the motion spectra in roll, heave, and pitch for a ship in a sea state when the RAO and sea spectra are provided. Using the motion spectrum, calculate the probability of exceedance for a specified amplitude of motion.
  6. Calculate the maneuvering hydrodynamic derivatives for a ship from experimental measurements and use those derivatives to determine the straight-line stability and steady turning radius for the ship.

Prerequisites

  • EN222, Engineering Mechanics with Marine Applications II, AND
  • EN330, Probability and Statistics with Ocean Applications

Class Topics

  1. Harmonic Motion/Vibration Review
  2. Regular Waves
  3. Ocean Waves/Wave Spectrum
  4. Strip Theory
  5. Linearized Heave, Roll, and Pitch Motion in Regular Waves
  6. Linearized Heave, Roll, and Pitch Motion in Irregular Waves
  7. Seakeeping Considerations in Design
  8. Maneuvering – Linearized Equations of Motion
  9. Controls-Fixed Directional Stability
  10. Analysis of Turning Ability

Laboratory Projects

  1. Water Wave Mechanics – Regular Waves
  2. Water Wave Mechanics – Irregular Waves
  3. Dynamic Model Ballasting
  4. Measuring Added Mass in Sway
  5. Head Seas Testing: Wave Induced Motions
  6. Computer-Based Motions Prediction
  7. Rolling Motion at Zero Speed in Beam Seas
  8. Rudder Testing in Circulating Water Channel
  9. LAPMM Testing – Static
  10. LAPMM Testing – Dynamic
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