Engin Gücüyen

Numerical analysis of deteriorated sub-sea pipelines under environmental loads

The significant point is the bidirectional interaction technique in FSI analysis while investigating subsea corrosion effect. By this way, pipe environment is accurately modelled and fluid effects are also considered. The effect of external corrosion defects on structural behaviour of a pipeline is studied by creating a nonlinear numerical model based on the finite element method according to ABAQUS analysis program. Corrosion losses of sections are obtained from experimental results and applied to the model. Numerical model is formed by a span of sub-sea pipeline that is subjected to environmental loads. Seismic and wind-generated irregular wave loads are considered as environmental loads. Irregular wave is represented with equivalent eight regular waves via FFT. The pipe is modelled according to two different types which are non-corroded(intact) and corroded (deteriorated) to demonstrate corrosion effects on it. The visible type of corrosion in marine environment is named ‘pitting’ corrosion, in which the material loss is locally interpenetrated over the surface. By considering this situation, the corroded and non-corroded pipes are modelled as 3D solid elements. The main point is revealing how the subsea corrosion affects the structural behaviour of pipelines on the basis of implementation of experimental results to a model structure due to changes of stresses and displacement.

Analysis of Offshore Wind Turbine Tower under Environmental Loads

ABSTRACT Researchers have started to use numerical methods in the fluid–structure interactive solutions with the advancing of computing technology. There are few studies investigating bidirectional fluid structure interaction (FSI) analysis due to requirements of high computer capacity. This insufficiency is attempted to be corrected in this study. Offshore wind turbine tower is selected to employ the method under environmental loads. To detect accuracy of the numerical analysis, the tower is modelled as a single-degree-of-freedom (SDOF) system. The equation of motion of the system is numerically integrated by using a fourth-order Runge–Kutta method. Time-varying lateral displacement of the tower and first natural frequency values are obtained from analysis. Afterwards, the structure and the environment are modelled in ABAQUS finite elements program. Bidirectional FSI technique is applied to the structure due to the interaction between ABAQUS/CFD-ABAQUS/Explicit. The accuracy of SDOF and bidirectional FSI analyses results is determined in the end.

Analysis of submarine outfalls subjected to wave load

Posljednjih se godina bilježi znacajan napredak u podrucju tehnologije izvođenja podmorskih ispusta. Takav napredak doveo je do konstrukcijskih poboljsanja podmorskih ispusta, posebice difuzorskih i vertikalnih cijevi te sapnica. Rad se bavi modeliranjem jednog dijela podmorskog ispusta, tocnije difuzora, izrađenih od raznih materijala te utjecajima njihovog okruženja (unutarnji i vanjski tokovi). U analizama primijenjena je tehnika interakcije fluida i konstrukcije. Provedene analize pokazuju da su naprezanja najvisa na spojevima između glavne i vertikalne cijevi. Najvisi se pomaci ostvaruju pri osnom nanosenju valnog opterecenja na konstrukciju.

Early age corrosion of mild steel in aggressive media

Effects of the time of holding, type of section, and concentration of the solution on the early age corrosion of mild steel are studied. Section types for steel specimens were box, tube, and corner. They were subjected to 3.5%, 5.0%, and 7.0% NaCl solutions. It was established that the concentration of the solution affects the corrosion until reaching the saturation value.