The right location of an individual wind turbine within a wind farm is important in order to gain its optimal power output. Due to the large area involved, an experimental study can be difficult and non-economical. This paper presents a methodology by which the location of downstream turbines can be estimated by using velocity pattern analysis. A wake structure of an isolated helical Savonius turbine with 90º twist angle is first evaluated by a Sliding mesh method incorporating Reynold Average (RANS) turbulence model Spalart Allmaras. The formation of vortices outside the wake is then observed. It was found that by placing a downstream turbine at the location of the strongest vortex occurrence, in this case within the area between 20º to 90º with respect to the advancing blade of the upstream turbine, produces an enhancement of power coefficient to the later. Repeating the same procedure for another downstream turbine also yields the same result. The last turbine of the line array always experiences the highest power coefficient of all. An application of the concept to a 9 turbine array in a V formation reveals an overall power improvement of 11%. However, placing the downstream turbine in other areas of weaker vortex shows insignificant improvement.

Starting capability is an important feature of any high performance wind turbine. This parameter is usually referred to the rotor static performance. In this paper, the results of CFD analysis on four Savonius rotor designs are presented with the objective of investigating the effect of twist angle on the starting capability. Essentially it is a comparison between a conventional Savonius rotor and three helical rotors with 0°, 90° and 180° twist angle. The proposed methodology was first validated against the published wind tunnel test data. The best parameters were then used to evaluate the static performance of the four Savonius models. It is observed that helical Savonius rotor contributes to positive static torque coefficient for all rotor angles. The rotor with 90° twist angle gives the highest average static torque coefficient of 0.442 followed by 0° twist angle rotor and 180° twist angle with static torque coefficient of 0.434 and 0.385 respectively. This improvement in static torque coefficient will not only contribute to the better starting capability but also to the overall performance of Savonius rotor.

-Agarwood has been used widely in various ways, including traditional medicine and art. The usage of agarwood has grown broader in modern times include in therapeutic medicines and perfumery. In this paper the agarwood waste has been explored to be used as a fluid loss control agent to control fluid loss without affecting the drilling fluid rheological properties which are density, pH, viscosity, yield point and gel strength. Agarwood waste was used as an additive in the drilling fluid system due to its unique characteristic. Rheological and filtration measurements were performed on the formulated water-based drilling fluid. Formulations of a base solution of fresh water, sodium hydroxide, bentonite, barite, and xanthan gum were presented. The performance of the agarwood waste as the fluid loss control agent was compared with based fluid formulation and water-based drilling fluid with treating with conventional fluid loss control agent (starch). The filtrate volume of drilling fluid with agarwood waste was about 13 ml while for drilling fluid with conventional fluid loss control agent, starch gave 12 ml of filtrate volume after undergoing filtration test by using LPLT filter press. The performance of drilling fluid with agarwood was efficient as drilling fluid with starch.

Proper arrangement of multiple VAWT turbines has been known to have increased the overall power efficiency. The challenge is how to optimally place each turbine within a given location such that the overall performance is improved. This paper presents a methodology by which the placement of individual turbine is determined by the location of vortices created by the upstream turbine. This analysis is carried out by using commercial CFD solver via sliding mesh approach. To clearly observe the creation of wake and vortices by an isolated Savonius turbine, the extra fine mesh was defined outside the rotating zone of the computational domain. The resulted velocity pattern generated shows an area of the high vortex created at the tip of advancing blade at a certain rotor angle. However, the returning blade generates a weaker vortex. The placement of consecutive Savonius wind turbine is, therefore, should be at an angle ranges between 20° to 90° with respect to the advancing blade of the upstream turbine. The analyses on two-turbine, three-turbines and nine turbines in V formation have shown an improvement up to 11% in the overall power efficiency.

An optimum layout of turbines in a wind farm can be measured by a parameter called wind power density. This is essentially the power generated by the turbine per unit area. This paper attempts to demonstrate how the parameter could be increased by an oblique array configuration. In this numerical study, multiple helical Savonius turbines were used to compare the performances of different wind farm layout designs by using a finite element CFD solver. The optimum spacing between turbines was first determined for three turbine array configurations. It was then extended to a nineturbine array in V formation. Three wind farm configurations were considered namely all in clockwise (CW) or counterclockwise direction (CCW) and the other is a combination of CW and CCW direction. The wind power density for each configuration was then compared. The nine turbines arranged in V formation has improved its power density by 4 to 5 times when compared to nine isolated turbines in a wind farm.