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Numerical Modelling and Experiments on Sea Spray Icing

Kulyakhtin, Anton
Doctoral thesis
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PhD (27.25Mb)
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http://hdl.handle.net/11250/277036
Utgivelsesdato
2014
Metadata
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  • Institutt for bygg- og miljøteknikk [3635]
Sammendrag
Oil and gas activities in the cold seas are endangered by icing. Icing may occur when

water spray or moisture is deposited on a vessel or offshore structure above sea level

and the air temperatures is below the freezing temperature of water. Ice accumulation

can block rescue equipment and doors, and clog ventilation systems, which may

increase the risk of explosion as result of volatile gas accumulation. Icing can be caused

by supercooled fog, freezing rain, falling snow and freezing sea spray. The freezing sea

spray caused 80 – 90% of all offshore icing incidents and is the focus of this study.

To take precautions against icing, it is important to understand the physics of icing and

to model it. The rate of ice accretion is mainly defined by the spray flux and heat

transfer, and both must be accurately predicted. Existing icing models, e.g., ICEMOD

and RIGICE04, simplify the structure, subdividing it into cylindrical and flat

components. In these models, airflow around a component is assumed to be unaffected

by other parts of the structure, and the heat transfer is approximated using empirical

relations. In reality, however, the airflow field is complex. Upwind components can

create wind shadow regions or regions of accelerated flow in front of downwind

components; this changes both the spray flux and the heat transfer, thus making

ICEMOD and RIGICE04 inadequate.

A research subject of this PhD study was the heat transfer and spray flow around a

structure in a real airflow. The full-scale measurements in the literature are limited and

it is expensive to perform them. Therefore, for a preliminary answer the question was

addressed using computational fluid dynamics (CFD), which is capable of predicting

the spray flow and heat transfer around a structure with any shape; however, the

accuracy of CFD is uncertain.

Existing models of sea spray icing, e.g., ICEMOD and RIGICE04, neglect heat flux into

the accreted ice and assume that air cooling is directly spent to freeze the water film on

the ice surface. This assumption is good for steady ice growth. However, it is also used

in modelling icing caused by periodic sea spray. This study proves numerically and

experimentally that the heat flux into the accreted ice generated by freezing must not be

neglected.

The main contributions of this work are as follows:

The study develops the marine icing model, MARICE, which uses CFD to

calculate spray flux and heat transfer, and models water film motion on any

arbitrary surface.

· The study shows that Reynolds-averaged Navier-Stokes (RANS) models should

be used with care in icing simulations: the collision efficiency is well predicted

upstream flow separation point by any RANS turbulence model; however, the

wake and separation of the flow is modelled poorly.

· The study develops and validates a new model of ice growth caused by periodic

sea spray, which accounts for the heat conduction inside the accreted ice.
Består av
Paper 1: Kulyakhtin A., Løset S., 2011. Sea spray icing: In-cloud evaporation. Semianalytical and numerical investigation. International Workshop on Atmospheric Icing (IWAIS2011), Chong-Chin, China

Paper 2: Kulyakhtin, A., Kollar, L, Løset, S., Farzaneh, M., 2012. Numerical simulation of 3D spray flow in a wind tunnel with application of O'Rourke's interaction algorithm and its validation. Proceedings of the 21st IAHR International Symposium on Ice (IAHR2012).

Paper 3: Kulyakhtin, A., Shipilova, O., Libby, B. and Løset, S., 2012. Full-scale 3D CFD simulation of spray impingement on a vessel produced by ship-wave interaction. Proceedings of the 21st IAHR International Symposium on Ice (IAHR2012).

Paper 4: Kulyakhtin A., Kulyakhtin S., Løset S. Measurements of Thermodynamic Properties of Ice Created by Frozen Sea Spray, 2013. The 23rd International Ocean and Polar Engineering Conference (ISOPE), Anchorage, USA, June 30 - July 5 2013.

Paper 5: Kulyakhtin, A., Shipilova, O. and Muskulus, M., 2014. Numerical simulation of droplet impingement and flow around a cylinder using RANS and LES models. Journal of Fluid and Structures, Vol. 48, pp. 280-294. http://dx.doi.org/10.1016/j.jfluidstructs.2014.03.007 The article in is reprinted with kind permission from Elsevier, www.sciencedirect.com

Paper 6: Kulyakhtin, A., Tsarau, A., 2014. A time-dependent model of marine icing with application of computational fluid dynamics, Journal of Cold Regions Science and Technology, Vol. 104-105, pp. 33-44. http://dx.doi.org/10.1016/j.coldregions.2014.05.001 The article in is reprinted with kind permission from Elsevier, www.sciencedirect.com

Paper 7: Kulyakhtin, A., Kulyakhtin, S. and Løset, S, 2014. The role of the ice heat conduction in the ice growth caused by periodic sea spray. Journal of Cold Regions Science and Technology (submitted).
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NTNU
Serie
Doctoral thesis at NTNU;2014:338

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