Adi Maimun Abdul Malik

Tandem riser VIV suppression fairing model test

In deepwater development areas of Southeast Asia, the current is strong and relatively more persistent compared to other deepwater regions. Top tensioned risers (TTR) are critical submerged components of offshore platforms, constantly exposed to currents. These currents cause unsteady flow patterns around the risers i.e. vortex shedding. When the vortex shedding frequency is near the risers natural frequency, undesirable resonant vibration of the riser also known as Vortex Induced Vibration (VIV) occurs. Several types of VIV suppression devices are used in the offshore industry. Among them, the U-shaped fairing claims to have the capabilities of reducing VIV effectively as well as lowering drag loads. This study investigates the effectiveness of a U-shaped fairing in suppressing riser VIV. The model test was successfully performed in a towing tank facility located at Universiti Teknologi Malaysia (UTM), Johor Bahru, Malaysia. This study is a significant collaboration between a local academic institution and the offshore oil and gas industry, aligned with the industrys initiative of increasing local capabilities for research and development. In this study, the VIV of two risers in tandem is simulated using scaled test models. The current flow is simulated by towing the vertically submerged test models with a moving carriage. The riser with fairing models are attached to a pair of custom-designed test rigs which are able to measure the forces and also allow movement of the test model during towing tests. The two test rigs are attached to a steel structure under the carriage which accommodates different tandem riser configurations and spacings. Two different sizes of risers and fairings are tested to check for Reynolds number effects. For each tandem riser configuration, three different riser conditions are tested, i.e. (a) bare risers without fairings; (b) risers with weathervaning fairings, and (c) upstream riser with fairing stuck at different orientations and downstream riser with weathervaning fairing. The test results show significant reduction in drag and VIV for the risers with weathervaning fairings in different tandem configurations. Interesting motion characteristics are shown in some of the stuck fairing cases highlighting the adverse effects should the fairings fail to perform normally in the field. Effective mitigation of VIV in risers using fairing suppression devices could lead to improved riser fatigue life and overall a more economical platform design. These benefits are highly applicable to local deepwater developments for the oil and gas industry.

Electrical Generation Using Renewable Technology for Remote Area: A Review

This paper is a review about process, progress and operation principle of renewable technology using water current as a clean, green and renewable energy to generate electricity for areas especially remote site that access to water but they are poor in electricity.

Propeller Effect on 3D Flow at the Stern Hull of a LNG Carrier Using Finite Volume Method

Numerical study and RANS simulations have been applied to investigate the incompressible free surface flow around the stern hull of Liquefied Natural Gas (LNG) ship affected by working propeller behind of her. Experimental works are carried out using LNG ship model in Marine Teknologi Center (MTC) of Univrsiti Teknologi Malaysia (UTM) to verify the computational fluid dynamic (CFD) results. Ansys-CFX 14.0 based on viscous flow finite volume code using the two-phase Eulerian–Eulerian fluid approach and shear stress transport (SST) turbulence model have been used in this study. A tetrahedral unstructured combined with prism grid were used with the viscous flow code for meshing the computational domain of water surface around it. CFD simulation has been verified using available experimental results. Finally, the flow structure, streamlines, velocity and pressure distribution around stern hull and propeller zone are discussed and analysed.

Numerical Prediction of Thermal Effect on Flow Field around a High-Rise Building Model

Recently, CFD (Computational Fluid Dynamics) is being more and more used in the investigation of the flow and thermal around high-rise buildings. In this study, prediction of thermal effect on flow pattern around high-rise buildings model located in the surface boundary layer was carried out using k-e turbulence model. Investigation of thermal effect on flow pattern behind the building and comparison between isothermal and non-isothermal building using standard k-e showed that the surface temperature of building wall led to a strong upward motion close to heating wall and decreased the reattachment length behind it. The model sittings of validation study was accomplished by comparing the simulation of wind flow around building models with the experimental data of Architectural Institute of Japan (AIJ) that results showed in weak wind region, standard k-e has good agreement with experimental.

Prediction of wind flow around high-rise buildings using RANS models

Recently, CFD (Computational Fluid Dynamics) is being increasingly used to investigation of the flow around high-rise buildings. In this study, prediction of wind flow around two cases high-rise buildings model placed within the surface boundary layer were carried out using various turbulence models. The accuracy of two-equation turbulence models were compared with experimental data of Architectural Institute of Japan (AIJ).as a result, all two-equation models are shown overestimation the reattachment length behind the buildings.

Arm Effect on Performance of Vertical Axis Current Turbine Using RANS Simulation

Climate changing, electrical demands, rising diesel fuel prices, as well as fossil fuel-based energy is limited and in fact is depleting ,are subjects to use of renewable technologies. Among the different renewable energy technologies, hydro power generation (large and small scale) is the prime choice in terms of contribution to the worlds electricity generation by using water current turbines.CFD simulation using two equations turbulence model was carried out to compare performance of conventional savonius turnine and new consept of vertical axis turbine. This study was coducted to reach suitable desigh of vertical axis turbines for capturing more kineticenergy of current via of others esspecially,low current speed.

Riser VIV suppression device tests for application to a southeast Asia TLP

The Southeast Asia metocean environment is characterized by moderate wind and waves with relatively strong and persistent currents. The design of a Tension Leg Platform (TLP) for Southeast Asia is strongly affected by the current and resulting drag loads, particularly if many risers are required. To reduce vortex-induced vibrations (VIV) of offshore tubular members i.e. top tension risers (TTRs), vortex suppression devices such as helical strakes and fairings are used.This paper gives an insight into a set of riser VIV model tests which is carried out to study the effectiveness of an open-back “U”-shaped fairing in suppressing riser VIV. The splitting loads and the drag loads of the fairings are also investigated during these tests. The tests are being done at the Marine Technology Center (MTC), Universiti Teknologi Malaysia (UTM) in support of this application, and also in part to increase local technological capabilities. Two sizes of risers are being tested in three configurations: (a) bare riser without any fairings; (b) riser with weathervaning fairings (normal condition) and (c) riser with fairings fixed at different headings (abnormal condition). The test results show that in the normal condition, the fairing is effective at suppressing VIV.Copyright