Validation of a Software Tool (DROPSIM) to Predict the ‘Drop and Getaway’ Behaviour of a Lifeboat

2015 ◽  
Author(s):  
Elia Palermo ◽  
Roberto Tonelli ◽  
Frans Quadvlieg ◽  
Jule Scharnke ◽  
Ingo Drummen ◽  
...  
Keyword(s):  
Software Tool ◽  
Free Fall ◽  
Model Tests ◽  
Simulation Tools ◽  
Normal Means ◽  
Strip Theory ◽  
Calm Water ◽  
Validation Procedure ◽  
Prototype Software ◽  
Free Falling

The purpose of a free fall lifeboat is to evacuate people from platforms in case of emergency, and when other, normal means of evacuation, are not possible. For instance, when the weather is too rough, and evacuation cannot be performed by helicopters, the lifeboats are the last way of escape. It is thus essential to be able to properly assess the operability of a lifeboat and the safety of its occupants upon evacuation. Over the past four years, methods to quantify the operability limits of a lifeboat were analysed in a research project carried out for Statoil. As part of this project, a prototype software (denominated DROPSIM) was developed to predict the ‘drop and sailaway behaviour’ of a lifeboat. DROPSIM is a simplified method based on strip theory, with the objective to obtain predictions that are consistent with the relevant statistical behaviour of the lifeboat, and for the same target level of probability. Particularly because DROPSIM is a simplified tool, it is vital to verify that the software is adequate for simulating thousands of random lifeboat drops, yielding robust statistical predictions with sufficient accuracy. In order to show the performance of the simulation tool, an extensive validation procedure was established, based on a large amount of model test and data from other simulation tools. The following topics were considered in the validation: A. Verification: basic checks, e.g. related to buoyancy without comparison to model tests B. Consistency of simulated and measured response for basic test cases, including free-falling wedge tests and a variety of impact tests with a bullet shaped model C. Prediction of the sailaway behaviour of a lifeboat in comparison to model tests D. Comparison with integrated drop and sailaway model tests in normal and off-design (extreme) conditions in calm water and in waves. In this paper the results of the validation of DROPSIM are presented and discussed. Another dedicated paper gives insight into the mathematical model of DROPSIM ([1]).

CFD Simulations of Lifeboat During Sailing Phase in Harsh Weather

2015 ◽  
Author(s):  
Vidar Tregde ◽  
Sverre Steen
Keyword(s):  
Degrees Of Freedom ◽  
Free Fall ◽  
Model Tests ◽  
Full Scale ◽  
Cfd Simulations ◽  
Thrust Coefficient ◽  
Cfd Models ◽  
Calm Water ◽  
Set Up ◽  
Full Scale Tests

A free fall lifeboat is going through several phases during a drop; sliding on the skid, rotation on skid, free fall, water entry, ventilation, maximum submergence, resurfacing and the sailing phase. In the sailing phase, the engine is running, providing propeller thrust, and the vessel is exposed to wind and waves while trying to run away from the host. CFD simulations of the lifeboat in the sailing phase have been run in regular Stokes 5th order waves, as well as simulations in irregular seas. The regular waves have been set up with different wave heights and wave periods. The set-up of waves have been done to fulfil the requirements in DNV-OS-E406, which is the DNV-GL offshore standard for design of free fall lifeboats. Validation of the CFD models are done with comparison to model tests from calm water tests as well as self-propelled model tests in waves. Results from full scale tests in calm water and in waves are also used in validation of CFD results. The hydrodynamic problem solved for 3 degrees-of-freedom (DOF) free running model in waves with thrust force from propeller is solved using the CFD software Star CCM+. A method for estimating thrust coefficient with a combination of full scale calm water results and results from CFD simulations is presented. The CFD simulations have shown to give acceptable accuracy for lifeboat in a seaway. Further, the CFD simulations have shown to be very useful for demonstrating fulfilment of requirements in the offshore standard for lifeboats in the sailing phase.

Documentation of Operational Limits of Free-Fall Lifeboats by Combining Model Tests, Full-Scale Tests, and Computer Simulation

2009 ◽  
Author(s):  
Wojciech E. Kauczynski ◽  
Per Werenskiold ◽  
Frode Narten
Keyword(s):  
Wave Height ◽  
Model Test ◽  
Free Fall ◽  
Model Tests ◽  
Full Scale ◽  
Test Results ◽  
Extrapolation Methods ◽  
Basic Performance ◽  
Calm Water ◽  
Full Scale Tests

Historically, approval of lifeboats is based on a “calm water” philosophy through the SOLAS regulatory regime. In spring 2005 during offshore installation tests in calm water, unacceptable structural deflection of the roof for one type of free-fall lifeboat was revealed. Immediate actions were initiated by the Norwegian Oil Industry Association (OLF) and Statoil, including the goal of studying and documenting the main performance factors for free-fall lifeboats at up to a 100-year weather condition. In addition, OLF has request to develop relevant criteria for in depth classification of performance, and finally to upgrade urgently, when relevant, all free-fall lifeboats operating on the Norwegian continental shelf to the agreed standards. The basic performance criteria of free-fall lifeboat systems in emergency conditions are: structural strength, acceleration loads on passengers during water impact, boat forward speed immediately after water entry, and the manoeuvring away to a safe distance from the installation. Within the OLF-project, MARINTEK has performed an extensive model test program (over 25000 tests) with the 14 different types of free-fall lifeboats (launched by vertical drop or from a skid). Boat performances have been examined in different weather conditions, ranging from still water up to 11m wave height (regular waves and wind) or 7m (irregular significant wave height with corresponding wind). Calm water model test results have been compared to full-scale test results. In order to extend prognosis of the lifeboat performances up to 100-year storm condition (Hs = 15.7m), special extrapolation methods have been developed for studying the three basic performance areas, augmented by computer simulations applied for higher sea states. This paper presents example results and experiences gained from the model tests, full-scale tests and combined use of simulations and model test results. Experimental model test set-up and applied analysis and extrapolation methods are reviewed. Finally, the application of newly proposed performance and technical criteria is discussed.

scholarly journals Multi-Camera Based Setup for Geometrical Measurement of Free-Falling Molten Glass Gob

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1041
Author(s):  
Mazhar Hussain ◽  
Mattias O’Nils ◽  
Jan Lundgren
Keyword(s):  
Free Fall ◽  
Frame Rate ◽  
Geometrical Parameters ◽  
Contactless Method ◽  
Molten Material ◽  
Dynamic Changes ◽  
Direct Measurements ◽  
Molten Materials ◽  
Free Falling

High temperatures complicate the direct measurements needed for continuous characterization of the properties of molten materials such as glass. However, the assumption that geometrical changes when the molten material is in free-fall can be correlated with material characteristics such as viscosity opens the door to a highly accurate contactless method characterizing small dynamic changes. This paper proposes multi-camera setup to achieve accuracy close to the segmentation error associated with the resolution of the images. The experimental setup presented shows that the geometrical parameters can be characterized dynamically through the whole free-fall process at a frame rate of 600 frames per second. The results achieved show the proposed multi-camera setup is suitable for estimating the length of free-falling molten objects.

Structural Integrity Assessment of Free-Fall Lifeboats by Combining Fast Monte-Carlo Simulations With CFD by Means of Proxy Load Variables

2016 ◽  
Author(s):  
Sébastien Fouques ◽  
Ole Andreas Hermundstad
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Structural Integrity ◽  
Free Fall ◽  
Integrity Assessment ◽  
Proxy Variables ◽  
Pressure Load ◽  
Calm Water ◽  
Measured Pressure

The paper is concerned with the launch of free-fall lifeboats (FFL). It proposes a method that complies with the DNV-OS-E406 standard in order to select characteristic launches from Monte Carlo simulations for further structural load assessment with CFD and FEM. Proxy variables derived from kinematic parameters and aiming at predicting pressure load indicators are computed with the VARUNA launch simulator developed by MARINTEK. The statistical distributions of the proxy variables obtained from the Monte Carlo simulations are used to identify critical scenarios, and characteristic launches can then be selected from a chosen probability level. The feasibility of the proposed method is documented in the paper for several types of pressure loads. Existing model test data from various FFL-launch campaigns in calm water and in waves are used to compute the proxy variables as it would be done in the VARUNA simulator. Scatter diagrams showing the correlation with actual measured pressure load indicators are then established to assess the quality of the chosen proxy variables.

A Set-Based System for Eliminating Infeasible Designs in Engineering Problems Dominated by Uncertainty

1997 ◽  
Author(s):  
William W. Finch ◽  
Allen C. Ward
Keyword(s):  
Electronic Circuit ◽  
Predicate Logic ◽  
Software Tool ◽  
Design Parameters ◽  
Engineering Systems ◽  
Multiple Sources ◽  
Design Problems ◽  
Engineering Design Problems ◽  
Engineering Problems ◽  
Prototype Software

Abstract This paper gives an overview of a system which eliminates infeasible designs from engineering design problems dominated by multiple sources of uncertainty. It outlines methods for representing constraints on sets of values for design parameters using quantified relations, a special class of predicate logic expressions which express some of the causal information inherent in engineering systems. The paper extends constraint satisfaction techniques and describes elimination algorithms that operate on quantified relations and catalogs of toleranced or adjustable parts. It demonstrates the utility of these tools on a simple electronic circuit, and describes their implementation and test in a prototype software tool.

A Nonlinear Mathematical Model for Ship Turning Circle Simulation in Waves

2005 ◽  
Vol 49 (02) ◽  
pp. 69-79 ◽  
Author(s):  
Ming-Chung Fang ◽  
Jhih-Hong Luo ◽  
Ming-Ling Lee
Keyword(s):  
Mathematical Model ◽  
Degrees Of Freedom ◽  
Regular Waves ◽  
Nonlinear Mathematical Model ◽  
Ship Maneuvering ◽  
Sea Trial ◽  
Six Degrees Of Freedom ◽  
Strip Theory ◽  
Calm Water ◽  
Maneuvering Motion

In the paper, a simplified six degrees of freedom mathematical model encompassing calm water maneuvering and traditional seakeeping theories is developed to simulate the ship turning circle test in regular waves. A coordinate system called the horizontal body axes system is used to present equations of maneuvering motion in waves. All corresponding hydrodynamic forces and coefficients for seakeeping are time varying and calculated by strip theory. For simplification, the added mass and damping coefficients are calculated using the constant draft but vary with encounter frequency. The nonlinear mathematical model developed here is successful in simulating the turning circle of a containership in sea trial conditions and can be extended to make the further simulation for the ship maneuvering under control in waves. Manuscript received at SNAME headquarters February 19, 2003; revised manuscript received January 27, 2004.

scholarly journals On-Sun Performance Evaluation of Alternative High-Temperature Falling Particle Receiver Designs

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
Julius E. Yellowhair ◽  
Kenneth Armijo ◽  
William J. Kolb ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Particle Temperature ◽  
Free Fall ◽  
Mass Flow Rates ◽  
Mesh Structures ◽  
Free Falling ◽  
The Impact

This paper evaluates the on-sun performance of a 1 MW falling particle receiver. Two particle receiver designs were investigated: obstructed flow particle receiver versus free-falling particle receiver. The intent of the tests was to investigate the impact of particle mass flow rate, irradiance, and particle temperature on the particle temperature rise and thermal efficiency of the receiver for each design. Results indicate that the obstructed flow design increased the residence time of the particles in the concentrated flux, thereby increasing the particle temperature and thermal efficiency for a given mass flow rate. The obstructions, a staggered array of chevron-shaped mesh structures, also provided more stability to the falling particles, which were prone to instabilities caused by convective currents in the free-fall design. Challenges encountered during the tests included nonuniform mass flow rates, wind impacts, and oxidation/deterioration of the mesh structures. Alternative materials, designs, and methods are presented to overcome these challenges.

Model Tests of a Caisson in Wet Towing for Assessing Resistance and Stability in Calm Water and Waves

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Chang-Wook Park ◽  
Jeonghwa Seo ◽  
Shin Hyung Rhee
Keyword(s):  
Degrees Of Freedom ◽  
Model Tests ◽  
Added Resistance ◽  
Power Requirement ◽  
Effective Power ◽  
Six Degrees Of Freedom ◽  
Calm Water ◽  
Improved Stability ◽  
Scale Ratio ◽  
The Stability

A series of model tests of a caisson in wet towing were conducted in a towing tank to assess the stability and effective power requirement in calm water and head sea conditions. The scale ratio of the model was 1/30, and the model-length-based Froude number in the tests ranged from 0.061 to 0.122, which is equivalent to 2 and 4 knots in the full scale, respectively. During the towing of the model, tension on the towline and six-degrees-of-freedom (6DOF) motion of the model were measured. Under the calm water condition, the effects of towing speed, draft, and initial trim variation on the towing stability and effective power were investigated. Initial trim improved stability and reduced required towing power. In head seas, effective power and towing stability were changed with the wavelength. It increased as the wavelength became longer, but the added resistance in long waves also stabilized the model with reduced yaw motion.

Response Surface Models for Analyzing Planing Hull Motions in a Vertical Plane

2014 ◽  
Author(s):  
Tanvir Mehedi Sayeed ◽  
Leonard M. Lye ◽  
Heather Peng
Keyword(s):  
High Speed ◽  
Uniform Design ◽  
Vertical Plane ◽  
Statistical Design ◽  
Surrogate Models ◽  
Center Of Gravity ◽  
Design Parameters ◽  
Strip Theory ◽  
Calm Water ◽  
Sinkage And Trim

A non-linear mathematical model, Planing Hull Motion Program (PHMP) has been developed based on strip theory to predict the heave and pitch motions of planing hull at high speed in head seas. PHMP has been validated against published model test data. For various combinations of design parameters, PHMP can predict the heave and pitch motions and bow and center of gravity accelerations with reasonable accuracy at planing and semi-planing speeds. This paper illustrates an application of modern statistical design of experiment (DOE) methodology to develop simple surrogate models to assess planing hull motions in a vertical plane (surge, heave and pitch) in calm water and in head seas. Responses for running attitude (sinkage and trim) in calm water, and for heave and pitch motions and bow and center of gravity accelerations in head seas were obtained from PHMP based on a multifactor uniform design scheme. Regression surrogate models were developed for both calm water and in head seas for each of the relevant responses. Results showed that the simple one line regression models provided adequate fit to the generated responses and provided valuable insights into the behaviour of planing hull motions in a vertical plane. The simple surrogate models can be a quick and useful tool for the designers during the preliminary design stages.

Thorough Verification and Validation of CFD Simulation for FPSO Roll Damping

2019 ◽  
Author(s):  
Donghwan Lee ◽  
Zhenjia (Jerry) Huang
Keyword(s):  
Numerical Modeling ◽  
Cfd Simulation ◽  
Development Project ◽  
Model Tests ◽  
Design Tool ◽  
Verification And Validation ◽  
Empirical Formulas ◽  
Roll Damping ◽  
Calm Water ◽  
Offshore Industry

Abstract For floating production platform such as FPSO and FLNG, it is important to use confidently estimated roll damping coefficients in the prediction of its motions in waves since in many cases the roll response is mainly contributed from resonance. Traditionally roll damping prediction was made through model tests or empirical formulas. As computing power and numerical modeling techniques have been improved during last a few decades, offshore industry starts to consider CFD as an alternative engineering and design tool complementary and/or supplementary to physical model tests. This paper presents our verification and validation work of modeling practices with commercially available CFD software for engineering applications for FPSO roll decay damping in calm water. The numerical modeling followed a recommended modeling practice developed by a Joint Development Project – TESK JDP [1].

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