Marine engineering

In this thesis, feasibility of a concept for launch and recovery of the Remus AUV from WAM-V USV is investigated. A modular recovery system which can be added to the WAM-V payload tray was designed, and based on a review of previous literature a CONOPS was developed for the launch and recovery process. The first phase of the CONOPS, which pertains to the position of the REMUS initially on the free surface prior to sling engagement is simulated using ANSYS AQWA. Preprocessing for the simulation involved simplification of the model in ANSYS SpaceClaim to achieve a proper mesh as well as theoretical calculations of the input parameters for wave environment and point masses etc. The simulation was evaluated by taking into consideration two wave environment scenarios: beam sea’s (-90 degrees) and head seas (0 degrees). The wave environment was based on a linear frequency range for the waves which considered wavelengths that correspond to half and double the length of the WAM-V 16’. The significance of the simulation is characterized through identifying the ideal direction and wave frequency range for recovery based on the RAOs of the two vehicles.

The objective of this research was to characterize the seawater transport and its effect on the transverse tensile strength of a carbon/vinylester composite. The moisture contents of neat vinylester and unidirectional carbon/vinylester composite panels immersed in seawater were monitored until saturation. A model for moisture up-take was developed based on superposition of Fickian diffusion, and Darcy’s law for capillary transport of water. Both the predicted and measured saturation times increased with increasing panel size, however the diffusion model predicts much longer times while the capillary model predicts shorter time than observed experimentally. It was also found that the saturation moisture content decreased with increasing panel size. Testing of macroscopic and miniature composite transverse tensile specimens, and SEM failure inspection revealed more fiber/matrix debonding in the seawater saturated composite than the dry composite, consistent with a slightly reduced transverse tensile strength.

The time series method of Auto Regressive Moving Average (ARMA) is applied to
the problem of real time ship motion prediction. The theory of Scalar input
Scalar output ARMA (n, n-1) model and the same extended to multiple series as
vector, ARMAV model have been concisely presented. The field experimental
procedure for roll measurement of vessel at sea and barge model test procedure
for heave and pitch measurements are discussed. The time series data of roll is
analysed as a scalar ARMA (n, n-1) model and the results of prediction are
presented. The model test data of heave, pitch and wave were analysed as ARMAV
(n,n-1) vector model and the results are presented. The model test and
experimental results demonstrate the feasibility of ARMA modeling procedure as a
valuable tool in the area of real time ship motion prediction.