Numeric and Analytic Investigations of Mean-Square Exponential Stability for Stochastically Timed Systems

This paper is motivated by the problems posed in feedback control design when actuators, sensors, and/or computational nodes connect via unreliable or unpredictable communications channels. In these cases, there is a degree of stochastic uncertainty to the timing of the system’s discretizing elements, such as digital-to-analog converters. Several theorems related to the stability of non-uniformly sampled discrete dynamical systems have recently been proposed; here we examine through numeric investigation the characteristics of systems which are mean square exponentially stable (MSES). In particular we present a method to compute the range of mean and variance that a nonuniformly discretized feedback control system may tolerate while remaining MSES. Several examples are presented.

Numeric Investigation of Fluid Solid Interaction and Performance Analysis of Pre-Bent Wind Turbine Blade

The current work is focused on numeric investigation of aerodynamic load developed on a wind turbine blade and its effects on aeroelastic characteristics of a wind turbine blade. In order to do that proper turbulent model along with appropriate assumptions need to be determined. Geometry is modeled with actual blade data for both twist and tapper. The blade tip is not considered during the modeling. Validation is done by NREL phase VI wind turbine blade data as well as other published data. Finally the aerodynamic load obtained from the CFD simulation is transferred to perform the structural analysis. It has been found that the load distribution along the blade span is not linear. It varies with the span length and it also varies along the chord of the blade airfoil. Due to this varying load the stresses developed in the blade are dissimilar which dictates the skin thickness of the blade and the shape of the spur inside the blade. It has also been observed that the aerodynamic characteristics such as lift coefficient (CL) and pressure coefficient (CP) changes with the deflection of the blade which affects the power output of the wind turbine. Finally a pre-bent blade model has been analyzed and the effect due to the bent on the performance of the wind turbine has been observed and presented. It has been found that the pre-bent blade has better Cp distribution than deflected blade and the deviation of Cp from the actual straight blade reduce significantly in pre-bent blade compare to deflected blade. The pressure distribution along the chord of the blade airfoil at different locations have been observed and presented.

Numeric Investigation of Fluid Solid Interaction on Wind Turbine Blade

The current work is focused on numeric investigation of aerodynamic load developed on a wind turbine blade and its effects on aeroelastic characteristics of a wind turbine blade. In order to do that proper turbulent model along with appropriate assumptions need to be determined. Geometry is modeled with actual blade data for both twist and tapper. Blade tip is not considered during the modeling. Validation is done by NREL phase VI wind turbine blade data as well as other published data. Finally the aerodynamic load obtained from the CFD simulation is transferred to perform the structural analysis. It has been found that the load distribution along the blade span is not linear. It varies with the span length and it also varies along the chord of the blade airfoil. Due to this varying load the stresses developed in the blade is dissimilar which dictates the skin thickness of the blade and the shape of the spur inside the blade. It has also been observed that the aerodynamic characteristics such as lift coefficient (CL) and pressure coefficient (CP) changes with the deflection of the blade which affects the power output of the wind turbine.