The doubled formulation of string theory, which is T-duality covariant and enlarges spacetime with extra coordinates conjugate to winding number, is reformulated and its geometric and topological features examined. It is used to formulate string theory in T-fold backgrounds with T-duality transition functions and a quantum implementation of the constraints of the doubled formalism is presented....

Vertical Axis Wind Turbines (VAWTs) are omni-directional, low-cost, low-efficiency wind power extractors. A conventional drag-based VAWT consists of multiple thin rotor blades with a typical peak Tip Speed Ratio (λ) < 1. Their lower cut-in speed and maintenance cost make them ideal for generation in urban environments. Numerous studies have been carried out analysing steady operation VAWTs q...

This paper compares three different numerical models to evaluate their accuracy for predicting the performance of an H-rotor vertical-axis wind turbine (VAWT) considering influence struts. The strut VAWTs is one factor that makes flow feature around more complex and thus influences rotor performance. focus this study placed on analyzing how accurately approaches are able reproduce force distrib...

The development of the Vertical Axis Wind Turbine (VAWT) is still a challenge for several researchers in world and Indonesia. Due to potential Indonesian coast generally has an average wind speed 3-7 m / s which classified as low very suitable VAWT operates at speeds. Combining 2 existing types one efforts on improve performance these turbines. Hybrid Savonius-Darrieus can increase coefficient ...

In this article, the suitability of Reynolds-averaged Navier–Stokes (RANS) to predict dynamic response in startup process small-scale Darrieus vertical-axis wind turbines (VAWT) was investigated. Using OpenFOAM, numerical simulations have been run evaluate regions rotor revolution where prediction aerodynamic coefficients is expected give unreliable results. The qualitative aspects self-startin...

A lift-driven vertical axis wind turbine (VAWT) generates peak power when it is rotating at high tip-speed ratios (TSR), which time the blades encounter angles of attack (AOA) over a small range from zero to 30 degrees. However, its ability self-start dependent upon performance low TSRs, AOAs 180 novel vented aerofoil presented with intention improving VAWT TSRs without hampering TSRs. Computat...