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Nicholas Cowlan

Bio: Nicholas Cowlan is an academic researcher. The author has contributed to research in topics: Transient (oscillation) & Impact pressure. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

Papers
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Proceedings ArticleDOI
01 Jan 2009
TL;DR: In this paper, the authors investigated a transient sloshing flow in a rectangular tank by comparing model tests and unsteady Reynolds-Averaged Navier-Stokes CFD simulation.
Abstract: This study investigates a transient sloshing flow in a rectangular tank by comparing model tests and unsteady Reynolds-Averaged Navier-Stokes CFD simulation. The sloshing flow is excited by a normally periodic surge motion, which is then subjected to a transient akin to an LNG carrier encountering a particularly steep wave. It is found that the impact pressure recorded in the transient motion is several times greater than that observed at resonance. High speed video data and CFD simulation is used to analyse the sloshing flow. The severity is explained by the absence of entrained air bubbles prior to impact and the second mode response one half period before impact.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: A comprehensive review of recent research developments on the hydrodynamics of FLNG can be found in this paper, where numerical calculations and model tests are summarized, existing problems are discussed, and further research topics regarding FLNG are suggested.

74 citations

Journal ArticleDOI
TL;DR: In this paper, a criterion based on wave propagation is developed to assess the importance of including fluid compressibility for sloshing flows with low levels of fluid impact, which can be simulated with incompressible fluid models for both air and water.

32 citations

DissertationDOI
21 Dec 2012
TL;DR: In this article, a validated holistic numerical method, which captures all hydrodynamic aspects that are relevant during offloading operations, is presented, which allows accurate extrapolation of results from model scale to full scale.
Abstract: Developing maritime gas fields in deep water by Floating Liquefied Natural Gas (FLNG) concepts poses demanding technical challenges. So far, no systems are in operation but projects in the design or construction phase are characterized by a floating terminal barge that produces, liquefies and stores natural gas at the offshore location. Frequently operating shuttle tankers are moored either alongside (side-by-side) or at the stern of the terminal (tandem) to receive the cryogenic liquefied cargo. During the offloading procedure, which takes 18 to 24 hours in changing environmental conditions, the transfer system has to tolerate the occurring relative motions between the terminal and the tanker. Gradually changing filling levels and free surface effects inside the tanks significantly influence the seakeeping behavior of the LNG carrier. Methods and research results published so far encompass experimental and numerical analyses of individual aspects of the complex hydrodynamic problem related to offshore LNG transfer. Well known work includes the determination of pressure peaks on tank walls caused by violent sloshing or exemplary reproductions of coupling effects between resonant internal fluid motions and wave-induced vessel motions. However, available results are mostly based on idealized conditions (two-dimensional setups, model testing with fresh water instead of LNG) where relevant hydrodynamic effects are observed to some extend but their consequences on the extrapolation of data to full scale operations is not fully comprehended. Due to these restrictions, most of the results obtained by current standard approaches are defective or at least incomplete. In this thesis, the first validated holistic numerical method, which captures all hydrodynamic aspects that are relevant during offloading operations is presented. By in-depth studies on the basis of this approach, the background of the occurring phenomena can be fully comprehended, which allows accurate extrapolation of results from model scale to full scale. Combining the introduced method and the gained background knowledge is a critical prerequisite for the conduction of trustworthy feasibility studies and the determination of operational ranges for FLNG projects. The selected linear potential theory based procedure is capable to excellently reproduce seakeeping characteristics as well as internal fluid motions. The entire cal-

6 citations

Proceedings ArticleDOI
01 Jan 2010
TL;DR: In this article, a numerical study of liquid dynamics in an LNG tank is presented, where the experimental data is analyzed from statistical point of view in order to obtain distributions of the pressure peaks.
Abstract: Numerical study of liquid dynamics in an LNG tank is presented. The available data from large scale (1:10) sloshing experiments of 2D section of an LNG carrier reveal large scatter in recorded values of peak pressures. The experimental data is analysed from statistical point of view in order to obtain distributions of the pressure peaks. Then the entire experimental data record is reproduced numerically by CFD simulations and it is shown that pressure peaks obtained numerically display scatter of values as well. A statistical description of the numerically obtained record is provided and compared with description derived from the experimental data. The applied CFD code ComFLOW solves Navier-Stokes equations and uses an improved Volume of Fluid (iVOF) method to track movement of fluid’s free surface. Two different fluid models, single-phase (liquid+void) and two-phase (liquid+compressible gas) can be applied, the latter model being capable of simulating bubbles and gas entrapped in liquid. For low tank filling rate discussed in the paper (10%) the single-phase approach is sufficient. Comparison of statistical properties of experimental and numerical records is offered.Copyright © 2010 by ASME

4 citations