این مقاله انگلیسی ISI در نشریه الزویر در ۲۲ صفحه در سال ۲۰۱۷ منتشر شده و ترجمه آن ۳۵ صفحه بوده و آماده دانلود رایگان می باشد.
|عنوان فارسی مقاله:||بررسی تجربی حوادث ضربه موج در عرشه بر روی یک مدل TLP|
|عنوان انگلیسی مقاله:||Experimental investigation of wave-in-deck impact events on a TLP model|
|رشته های مرتبط:||مهندسی عمران، مهندسی هیدرولیک، آب و سازه های هیدرولیکی، سازه و سازه های دریایی|
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|توضیحات||ترجمه این مقاله در سطح متوسط انجام شده است.|
|نشریه||الزویر – Elsevier|
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بخشی از ترجمه
در سالهای اخیر، تلاشهای زیادی برای تحقیق بر روی مشکلات اثر wave-in-deck در سکوهای خارج از ساحل توسط آزمایشات تجربی یا متدهای عددی یا ترکیبی از هر دو انجام شده است. از این رو، دانش مهندسی حال حاضر به پیشبینی دقیق بزرگی و پراکندگی بارهای wave-in-deck و پاسخ جهانی بدست آمده از سازه های شناور که محدود باقی مانده نیاز داشت.
بخشی از مقاله انگلیسی
In the 2004–۲۰۰۵ year period, hurricanes Ivan, Katrina and Rita in the Gulf of Mexico destroyed 126 offshore structures and severely damaged 183 other structures (Kaiser et al., 2009). The reported damage suggests that during tropical storms or hurricanes the wave height exceeds the design height for many existing offshore structures. Most recently, in December 2015, the living quarters of 50 workers of an offshore drilling rig in the North Sea were damaged when an extreme wave hit the accommodation block leaving one person dead and two more injured (REUTERS, 2016). It has been found that these deck impact events occur more frequently than have been predicted using theoretical methods (Naess and Gaidai, 2011).
The majority of cited research conducted on wave impact on offshore decks has focused on investigating simplified deck boxes or flat plates. However, under deck structures, such as columns and pontoons, can affect the force magnitude and its distribution on the upper deck structure. Owing to the hydrodynamic interaction between the columns and pontoons of a multi-column platform such as tension leg platform (conventional TLP), the diffraction and radiation effects can cause the wave elevation to increase and locally impact the lower deck (Niedzwecki and Huston, 1992; Scharnke and Hennig, 2015; Abdussamie et al., 2016a). Niedzwecki and Huston (1992) found that column spacing plays a major role in the wave upwelling underneath the deck and thereby it may affect the vertical wave-in-deck force. Abdussamie et al. found that the deck-column intersection areas of a fixed TLP model under the action of long-crested irregular waves experienced larger wave-in-deck slamming pressures than the middle areas of the deck underside. Scharnke and Hennig (2015) investigated the effect of substructures on the wave-in-deck load magnitude by attaching a box-type deck structure to a square column. It was found that the column presence had a significant effect on the magnitude of global vertical forces and local pressures; the load magnitudes were significantly increased.
With the column present, the upward peak of the vertical wave-in-deck force increased to more than double the maximum load measured without the column. Wave-in-deck slam events may produce major global and local loads on floating offshore structures. Global loads can generate large forces in the tendons and risers and adversely affect the floating structure’s motions, whilst local loads can cause structural damage to the deck and equipment impairing the safety of operation and life onboard (DNV, 2009). A significant part of the tendon tension experienced by a TLP during storm conditions can be associated with the ringing response, which is a narrow band process due to low damping in heave motion (Johannessen et al., 2006; Hennig et al., 2011). Thus, there is a need to investigate the dynamic behaviour of a TLP installation due to wave-in-deck slam events. Among the known theoretical approaches, the momentum method developed by Kaplan (1992); Kaplan et al. (1995), has been used extensively to estimate the wave impact and slamming loads on fixed offshore platforms. For instance, the method has been applied for the analysis of wave impact on decks of Gravity Based Structures (GBS) (Baarholm and Stansberg, 2005) as well as other fixed offshore platforms (Baarholm, 2009; Baarholm and Faltinsen, 2004). The use of the momentum method is also recommended by classification societies for analysing wave impact forces on decks of floating platforms. Baarholm et al. (2001) investigated theoretically an extreme wave impact on the deck of a semisubmersible platform due to regular waves.
The authors used a Wagner based approach to account for the platform motions and Stokes second order wave theory to describe the incident waves. The panel code WAMIT was used to obtain the transfer functions for the linear induced motions. The authors concluded that the deck impact caused a significant suction force which led to a large downward heave motion. With application to fixed structures, attempts have been made to predict the slam pressure and its distribution through the deck area using the linear wave theory. Wang (1970) developed a theoretical formula for the impact pressure on a flat plate of negligible thickness, which demonstrated good qualitative agreement with the pressure measured in model tests. The limitations of the momentum and similar methods are related to its use of wave kinematics of a non-disturbed wave field or otherwise relying on the potential flow theory for an incompressible fluid; this implies that no consideration is given to the effect of trapped air or viscous effects. Methods based on the computational fluid dynamics (CFD) have therefore received an increasing amount of attention in recent years. Commonly used commercial codes such as STAR-CCM+ and ANSYS FLUENT are available for modelling and solving wave-in-deck impact problems using the volume of fluid (VOF) method to capture freesurface hydrodynamic flows (CD-Adapco, 2012; Fluent, 2009). Nevertheless, CFD-based techniques have still limited acceptance for practical use for modelling a moored floating body subjected to extreme waves in an irregular sea state. Model tests have previously been carried out to estimate wave-indeck forces on different types of offshore structures. Model tests remain arguably the best approach for estimating wave-in-deck loads (Scharnke et al., 2014). The vast majority of published work has been focused on measuring global wave-in-deck impact forces on simplified deck boxes or flat plates fixed in space and subjected to regular waves (Bhat, 1994) and random waves (Sun et al., 2011). On the other hand, investigations of typical multi-column floaters are scarce. Furthermore, most investigations conducted on such structures are subjected to project confidentiality requirements and are therefore not available in the public domain.