2 research outputs found
Perception Enhanced Virtual Environment for Maritime Applications
This paper presents the development of a realtimeperception enhanced virtual environment for maritimeapplications which simulates real-time six degrees of freedomship motions (pitch, heave, roll, surge, sway, and yaw) underuser interactions, environmental conditions and various threatscenarios. This simulation system consists of reliable shipmotion prediction system and perception enhanced immersivevirtual environment with greater ecological validity. Thisvirtual environment supports multiple-display viewing that cangreatly enhance user perception and we developed the ecologicalenvironment for strong sensation of immersion. In this virtualenvironment it is possible to incorporate real world ships,geographical sceneries, several environmental conditions andwide range of visibility and illumination effects. This system canbe used for both entertainment and educational applications suchas consol level computer games, teaching & learning applicationsand various virtual reality applications. Especially this framework can be used to create immersive multi user environments
Motion analysis of FPSO in multidirectional seas : the West African offshore region
PhD ThesisThe use of experiment remains the most accurate method in the prediction and evaluation
of roll damping. Several models ranging from CFD to analytical and empirical techniques
and tools have been developed over the years for this purpose. However, the issue of
accurately capturing the adherent multilinear behaviour for hulls with sharp edges and
bilge keels remains a challenge until date. The elaborate works of Oliveira and Fernandes
(Oliveira and Fernandes ,2006,2010,2014) identified and characterized the existence of
two regimes using the bilinear model, later modified to the hyperbolic model. Following
their work, and identifying this gap, an enhancement in their formation lead to the
introduction of a third damping term, which represented the transition between the large
angle side and the small angle regions. A modified hyperbolic model has been proposed
and tested against existing models with reasonable agreement in terms of regenerating the
measured decay. The model’s capture of the transition region was validated using the
rigorous procedure of the bilinear methodology. The relative uncertainty associated with
the predictive model was evaluated to fall within 3.5% to 5.9% .The decay data were used
to modify the regression model of Oliveira and Fernandes and the enhanced model
reduced the predictive error in the model parameters from second to first order range. The
extracted damping coefficient and model where implemented in a code to study the
influence of directionality and spectrum type on the roll motion response of the freefloating unit (typical FPSO) in real sea environment. Interactive contour plot
representation was used to capture the sensitivities of spectrum type, directionality and
the multidirectional wave streams summation techniques developed prior to roll motion
response simulation. A barred region for the number of regular waves to be used was
established using the maximum spectra energy density and the estimated significant wave
height as the indicators. A 6dof code was developed using simplified methods and
techniques. The novel frequency-spectra weighted technique was proposed for the
estimation of the excitation force components of the equation of motion in irregular short
crested seas from regular wave formulations. The method was validated by running
similar scenarios in HydroD and the irregular wave test on scaled model. The roll motion
response from the proposed method compared favourably within first order error range
against the HydroD simulations and the irregular wave experiment conducted for
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JONSWAP spectrum for the targeted significant wave heights. Similar error margins
were also observed for the measured as well as the estimated wave elevations and all other
motion modes. The interactive results from the contour plots when translated into roll
motion was very evident in the estimated magnitudes in different sea state spectra
combinations (type and directions). The use of the suggested spectra form (lognormal or
triangular for the swell sea and JONSWAP-Glenn for the wind sea) for the West African
region identified variations in the roll response of between 1-23% or more than 5.5o
This goes to further show the need to use site or region specific spectrum for the determination
of design and operational parameters for offshore structures and associated units and for
personnel seakeeping comforts.Niger delta development commission (NDDC) in Nigeri