Dwi Lastomo

Improving a two-equation eddy-viscosity turbulence model to predict the aerodynamic performance of thick wind turbine airfoils

Numerical simulations for relatively thick airfoils are carried out in the present studies. An attempt to improve the accuracy of the numerical predictions is done by adjusting the turbulent viscosity of the eddy-viscosity Menter Shear-Stress-Transport (SST) model. The modification involves the addition of a damping factor on the wall-bounded flows incorporating the ratio of the turbulent kinetic energy to its specific dissipation rate for separation detection. The results are compared with available experimental data and CFD simulations using the original Menter SST model. The present model improves the lift polar prediction even though the stall angle is still overestimated. The improvement is caused by the better prediction of separated flow under a strong adverse pressure gradient. The results show that the Reynolds stresses are damped near the wall causing variation of the logarithmic velocity profiles.

Enhancing BEM simulations of a stalled wind turbine using a 3D correction model

Nowadays wind turbine rotors are usually employed with pitch control mechanisms to avoid deep stall conditions. Despite that, wind turbines often operate under pitch fault situation causing massive flow separation to occur. Pure Blade Element Momentum (BEM) approaches are not designed for this situation and inaccurate load predictions are already expected. In the present studies, BEM predictions are improved through the inclusion of a stall delay model for a wind turbine rotor operating under pitch fault situation of -2.3° towards stall. The accuracy of the stall delay model is assessed by comparing the results with available Computational Fluid Dynamics (CFD) simulations data.

The effects of energy storages on small signal stability of a power system

Utilizing additional devices for small signal stability enhancement of power systems is crucial over the last few years due to increasing number of demand, uncertainty of load and integrating intermittent power system based on renewable energy. Among the number of additional devices in power system, energy storage is becoming more popular in last few decade. This paper investigates the impact of different types of energy storage on the small signal stability of power system. In order to analyze the impact of aforementioned energy storage for small signal stability, a single power system connected to an infinite bus is used as a test system. The eigenvalue and damping ratio of the investigated mode are used to examine the impact of energy storage on dynamic behavior of the investigated system. Furthermore, a time domain simulation is used to validate the eigenvalue analysis of the system. From the simulation, it is found that the type of energy storage have significant influence on the small signal stability of power system, indicated by the increasing value of damping over the system.