Speeding up Hydrodynamic Simulations with a Parametric, Templated Approach

Hull Design engineers and hydrodynamicists need high fidelity tools to help understand the performance of the vessels they are designing. In the context of Computational Fluid Dynamics (CFD), it is often assumed these numerical simulations will take a long time to run and are cumbersome to the design process. Thus, high fidelity CFD tools are not yet seen as practical for a design environment. In the first part of the paper, a methodology for parameterizing all aspects of a simulation as dependent variables expressed in terms of length, speed, and displacement will be discussed. Then, a technique that can both speed up the runs and verify the uncertainly in the discretization will be shown. Lastly, by combining both methodologies, a demonstration on how to implement these techniques and speed up runs and get to high fidelity answers in a very fast and cost-effective manner will be showcased.

Increase in Stability of an X-Configured AUV through Hydrodynamic Design Iterations with the Definition of a New Stability Index to Include Effect of Gravity

A study about the effect of different configurations of stationary and movable appendages on the dynamic stability of an autonomous underwater vehicle (AUV) is presented. A new stability index that can be used to assess dynamic stability in the vertical plane is derived. It improves upon the vertical plane stability index by accurately accounting for the contribution of hydrostatic forces to dynamic stability, even at low speeds. The use of the new stability index is illustrated by applying it to a set of AUV configurations based on an AUV initially designed at Virginia Tech and built by Dive Technologies. The applicability of this index depends on the speed of the craft. The range of applicability in terms of speed is presented for the DIVE craft as an example. The baseline design of the DIVE craft has asymmetry in the vertical plane and symmetry in the horizontal plane. A virtual planar motion mechanism (VPMM) is used to obtain the hydrodynamic coefficients of the hull. Design iterations are performed on the baseline design by varying the appendages in shape and size, adding appendages and adding features on appendages. The best and the baseline design from this effort are incorporated in a 6 DOF lumped-parameter model (LPM) to compare results of a straight line maneuver. A computational fluid dynamic (CFD) tool is used to obtain the trajectory comparison of turn-circle maneuver for these two designs. A principal conclusion is the important contribution of a hydrostatic restoring force at low-moderate speeds by using GVgrav and the influence of design of control surfaces, both stationary and non-stationary, in the achievement of control-fixed course stability.

Graphical criteria of inherent stability of river vessels for the case of shallow waters navigation

Форма корпуса речного водоизмещающего судна во многом определяет его динамические свойства. Удачно подобранные геометрические параметры обеспечивают судну не только требуемую грузоподъемность и грузовместимость, но и предсказуемую управляемость при различных внешних условиях. Задача проектирования корпусов судов с заданными характеристиками управляемости связана с исследованием связи между геометрией корпуса и его динамикой. Динамику судна оценивают по виду характеристики управляемости и по критериям переходных процессов при выполнении специальных маневров головными судами серии или масштабными моделями [1, 2]. Использование таких методов затруднительно на этапе проектирования, так как необходимо изготовить масштабную модель и провести ее испытания при различных внешних условиях. Кроме того, этот способ достаточно затратный по времени, особенно если требуется изготавливать большое количество моделей. С целью сокращения числа моделей предлагается на этапе проектирования качественно оценивать динамические свойства будущего корпуса, а на этапе натурных экспериментов производить только небольшие корректировки. The hull geometry of a displacement riverboat largely determines its dynamic properties. Successfully selected geometric parameters provide a vessel not only with required cargo capacity and carrying capacity, but also with predictable steerability under various external conditions. The task of ship hull design with preset steerability properties is connected with investigation of relation between geometry of the hull and its dynamics. Vessel dynamics is estimated by type of controllability characteristic and by criteria of transients during special maneuvers by head vessels of series or scale models [1, 2]. The use of such methods is difficult at the design stage, since it is necessary to make a scale model and test it under various external conditions. In addition, this method is quite time-consuming, especially if a large number of models is required. In order to reduce the number of models, it is proposed to assess qualitatively the dynamic properties of the future hull at the design stage, and to make only small adjustments at the stage of full-scale experiments.

Guyana: Liza Phase 2 Novel Execution to Accelerate Field Development

The Liza Phase 2 Project combines a novel execution approach and forward-looking technology components to develop more complex areas of the Liza resource. The project delivers technology to optimize resource development through efficient Subsea, Umbilicals, Risers, and Flowlines (SURF) equipment designs and digital elements to enable future capabilities, such as a fiber optic cable to shore. For a new approach to Floating, Production, Storage and Offloading (FPSO) delivery, the project is partnering with SBM for the first ever use of their Fast4Ward® concept. The SBM Fast4Ward® program utilizes the Multi-Purpose Floater (MPF) hull design and provides the benefits of a new build FPSO with a reduced project development time similar to that of conversions. With almost double the SURF infrastructure as Liza Phase 1, Liza Phase 2 uses learnings and standardized SURF architecture to deliver one of the industry's largest subsea developments. Establishment of win-win partnerships with the primary contractors to achieve best overall value and strategic use of part number duplication contribute to the overall success. Based on the work of ExxonMobil proprietary reservoir modelling, infrastructure is being installed to enable Water Alternating Gas (WAG) injection for the complex development while a subsea fiber optic cable enables data to shore for optimized reservoir management and advanced facilities surveillance. The project is on track to deliver ~2 years after first oil was achieved for Liza Phase 1 by building on design replication and common methodologies where possible. Through thoughtful application of standardization, learnings, and incorporation of new technologies, the project efficiently delivers advanced capabilities to the Liza field. This also enables a "Design One, Build Multiple" (D1BM) approach for future developments in Guyana.

Parametric Hull Design with Rational Bézier Curves and Estimation of Performances

In this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of waterline, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g., continuity, endpoint angles, curvature) have been conceived aimed to avoid unreasonable shapes. These curves can be imported into any commercial Computer Aided Design (CAD) software and used as a frame to fit with a surface. The resistance of the hull can be calculated and plotted in order to have a real time estimation of the performances. The algorithm and the related Graphical User Interface (GUI) have been written in Visual Basic for Excel. To test the usability and the precision of the tool, two existing sailboats with different characteristics have been successfully replicated and a new design, taking advantages of both the hulls, has been developed. The new design shows good performances in terms of resistance values in a wide range of Froude numbers with respect to the original hulls.

Сombined ships stability analysis at the stage of design study

. A method of stability analysis for combined ship (oil carrier/platform ship type) at the stage of design study is presented. It should be noted that not all of ship’s main seaworthiness and operational characteristics are the result of a simple addition of the characteristics of an oil carrier and a platform ship. Their mutual influence takes place, which should be taken into account when analysing the stability in the multivariant optimization problems of internal and external design of such ships. This leads to the requirement to adjust the known methods of stability analysis at the initial stages of ship design, which was the purpose of the present work and its originality. Taking into account the multivariance of the task and the hull design type, the stability assessment will be carried out through the analysis of the metacentric height extreme value on the assumption that the requirements of Russian River Register for admissible heeling angle at static wind effect are met. In order to account for nonlinearity of static stability curve when inclining up to the angles of deck immersion into water and emergence of bilge, it is suggested to apply an approximate method of metacentric radius determination. The proposed method of combined ship stability assessment is recommended to apply at the stage of justification and analysis of ship’s key elements as a limitation in the problems of mathematical modeling of optimization of such type of ships. The method allows to exclude from further consideration at the design study stage the possible options that do not meet the requirements of seaworthiness.

Monitoring Re-Growth of Invasive Plants Using an Autonomous Surface Vessel

Invasive aquatic plant species, and in particular Eurasian Water-Milfoil (EWM), pose a major threat to domestic flora and fauna and can in turn negatively impact local economies. Numerous strategies have been developed to harvest and remove these plant species from the environment. However it is still an open question as to which method is best suited to removing a particular invasive species and the impact of different lake conditions on the choice. One problem common to all harvesting methods is the need to assess the location and degree of infestation on an ongoing manner. This is a difficult and error prone problem given that the plants grow underwater and significant infestation at depth may not be visible at the surface. Here we detail efforts to monitor EWM infestation and evaluate harvesting methods using an autonomous surface vessel (ASV). This novel ASV is based around a mono-hull design with two outriggers. Powered by a differential pair of underwater thrusters, the ASV is outfitted with RTK GPS for position estimation and a set of submerged environmental sensors that are used to capture imagery and depth information including the presence of material suspended in the water column. The ASV is capable of both autonomous and tele-operation.

Hull and Aerial Holonomic Propulsion System Design for Optimal Underwater Sensor Positioning in Autonomous Surface Vessels

Acoustic Doppler Current Profiler (ADCP) sensors measure water inflows and are essential to evaluate the Flow Curve (FC) of rivers. The FC is used to calibrate hydrological models responsible for planning the electrical dispatch of all power plants in several countries. Therefore, errors in those measures propagate to the final energy cost evaluation. One problem regarding this sensor is its positioning on the vessel. If placed on the bow, it becomes exposed to flowing obstacles, and if it is installed on the stern, the redirected water from the boat and its propulsion system change the sensor readings. To improve the sensor readings, this paper proposes the design of a catamaran-like Autonomous Surface Vessel (ASV) with an optimized hull design, aerial propulsion, and optimal sensor placement to keep them protected and precise, allowing inspections in critical areas such as ultra-shallow waters and mangroves.