Testing the Functionality and Applicability of Smart Devices for a Handheld Celestial Navigation System

In this paper, the functionality and applicability of smart devices for the purpose of handheld celestial navigation systems is investigated. The main instrument used to determine observer position (altitude measurements) in celestial navigation is the sextant. The use of a sextant and almanac or computer is a classical approach to determining the observer\u27s celestial position. This approach has two significant limitations, firstly the time window for the measurements is short, and secondly, the view of the ocean horizon must be clear. With the use of smart devices, we can overcome these two obstacles and create a so-called handheld celestial navigation system. Currently, smart devices have very accurate sensors to measure various physical quantities such as acceleration, angular velocity, orientation, etc. We are particularly interested in validating the orientation sensor for measuring the altitude and azimuth of the celestial body. The altitude of the celestial body is the primary parameter in determining the celestial position using a sextant. The idea is to replace the sextant with a smart device to measure the altitude and possibly the azimuth of the celestial body. To test this idea, two types of experiments are designed. In the first, a system on a tripod to obtain the most accurate measurements possible is set. Such tests will provide detailed information about the accuracy of the smart device\u27s sensors and its applicability in measuring altitude and azimuth. The test system will essentially resemble a theodolite device. In the second experiment, a hands-free measurement experiment that resembles a sextant to test the idea for practical use and functionality in the process of celestial positioning is set. The observed data show that the results of the measurements under controlled conditions are promising and within reasonable bounds for the accuracy of celestial positioning. Estimates of the position error by the graphical method are in the range of 10 Nm to 30 Nm. In order to obtain a fully functional stand-alone celestial positioning system, the proposed assembly needs to be improved through several unchallenging upgrades. A fully functional system can be considered as a cheap off-the-shelf handheld Celestial Navigational System (CNS)

MATHEMATICAL MODEL FOR RIVERBOAT DYNAMICS

Present work describes a simple dynamical model for riverboat motion based on the square drag law. Air and water interactions with the boat are determined from aerodynamic coefficients. CFX simulations were performed with fully developed turbulent flow to determine boat aerodynamic coefficients for an arbitrary angle of attack for the air and water portions separately. The effect of wave resistance is negligible compared to other forces. Boat movement analysis considers only two-dimensional motion, therefore only six aerodynamics coefficients are required. The proposed model is solved and used to determine the critical environmental parameters (wind and current) under which river navigation can be conducted safely. Boat simulator was tested in a single area on the Ljubljanica river and estimated critical wind velocity

Analysis of Generic IGBEM for Lifting Hydrofoils

Today the most crucial aspect in the preliminary vessel design stage is to make it as green/blue as possible. One of the exciting goals is the minimisation of vessel resistance. The use of hydrofoils to reduce the vessel draught and consequently, reduction in the vessel resistance is today one of the hottest design topics, especially for catamaran passenger vessels. In the present work, we discuss the issues related to the implementation of Isogeometric Analysis (IGA) Boundary Element Method (BEM) for the calculation of the hydrodynamic properties of lifting hydrofoils. The use of IGBEM allows numerical calculation of foil hydrodynamic properties without the traditional step of mesh generation using the CAD geometry directly. The analysis relies on the NURBS basis function with the generic Galerkin approach allowing identical solutions procedures for 2D or 3D problems. Method accuracy and computational times for a different number of Degrees of Freedom (DOF) in 2D are investigated

Experimental Estimation of Material and Support Properties for Flexible Dolphin Structures

Present work describes the inverse problem for identification of material and support type properties of flexible dolphin structure. Most liquid bulk terminals are equipped with a jetty as berthing facility. The ship mostly berths to dedicated breasting dolphin structures, which can be single-pile flexible/rigid dolphins or multi-pile flexible/rigid dolphins. This work considers dolphin motion as mass-spring damped system where cantilever approximation mimics dolphin pile. Few measurements have been made for the dolphin structure, which is approximately 30 m long, 15 m immersed in the bottom and placed about 2-3 m above the sea level. The elastic material properties and pile support were identified via inverse method combined with displacement measurements of dolphin head

Ships added mass effect on a flexible mooring dolphin in berthing manoeuvre

This paper deals with the hydrodynamic effect of the ship on a flexible dolphin during a mooring manoeuvre. The hydrodynamic effect refers to the change in momentum of the surrounding fluid, which is defined by the concept of added mass. The main reason for the present study is to answer the question, “What is the effect of the added mass compared to the mass of the ship during the mooring procedure for a particular type of ship?” Measured angular frequencies of dolphin oscillations showed that the mathematical model can be approximated by the zero frequency limit. This simplifies the problem to some extent. The mooring is a pure rocking motion, and the 3D study is approximated by the strip theory approach. Moreover, the calculations were performed with conformal mapping using conformal Lewis mapping for the hull geometry. The fluid flow is assumed to be non-viscous, non-rotating and incompressible. The results showed that the additional mass effect must be taken into account when calculating the flexible dolphin loads

Mathematical Analysis of Macroscopic Models for Slow Dense Granular Flow

In this dissertation we present analysis of macroscopic models for slow dense granular flow. Models are derived from plasticity theory with yield condition and flow rule. Corner stone equations are conservation of mass and conservation of momentum with special constitutive law. Such models are considered in the class of generalised Newtonian fluids, where viscosity depends on the pressure and modulo of the strain-rate tensor. We showed the hyperbolic nature for the evolutionary model in 1D and ill-posed behaviour for 2D and 3D. The steady state equations are always hyperbolic. In the 2D problem we derived a prototype nonlinear backward parabolic equation for the velocity and the similar equation for the shear-rate. Analysis of derived PDE showed the finite blow up time. Blow up time depends on the initial condition. Full 2D and antiplane 3D model were investigated numerically with finite element method. For 2D model we showed the presence of boundary layers. Antiplane 3D model was investigated with the Runge Kutta Discontinuous Galerkin method with mesh addoption. Numerical results confirmed that such a numerical method can be a good choice for the simulations of the slow dense granular flow