Analysis on the aerodynamic performance of vertical axis wind turbine subjected to the change of wind velocity

AbstractReynolds averaged Navier-Stokes equations and Realizable kɛ− model were used in this paper, and the two dimensional unsteady flow field of the vertical axis wind turbine was simulated numerically at different wind velocity. The calculation results showed that the velocity in the region of wind turbine's rotation was much larger than the air flow of the upstream. The length of the wind turbine's downstream wake dispersion region was increased with the increase of the wind velocity. There is a much larger value of the eddy in the rear region of the wind turbine's rotational blades. And eddy existed in the downstream region of the wind turbine, and the larger velocity of cross flow, the larger value of the downstream flow's eddy. When the rotational speed was constant, with the increase in wind velocity, the variation of the wind turbine's total torque coefficient tended to smooth. The calculation results pointed out the direction for the follow-up study

Analysis on the influence of rotational speed to aerodynamic performance of vertical axis wind turbine

AbstractA two dimensional vertical axis wind turbine's model was established in this paper, and two dimensional unsteady incompressible N-S equations and Realizable kɛ− turbulence model were solved with software FLUENT. SIMPLC algorithm was applied, combined with the sliding grid technology; the influence of rotational speed to the flow structure of vertical axis wind turbine was discussed. The results showed that, the rotation of wind turbine had significant influence on wake, and higher the rotational speed, the greater reduction of the wake velocity. The wake velocity restored gradually away from the rotational part. There was much larger turbulent kinetic energy near the tail of the wind turbine's blade. The value of turbulent kinetic energy reduced gradually away from the rotational part, and the flow restored the stratospheric state gradually. With the increase of wind turbine's rotational speed, the value of turbulent kinetic energy in calculation domain increased too. The results showed that the flow structure of vertical axis wind turbine's rotational process could be revealed effectively by numerical simulation, provided theoretical reference for the engineering design of the vertical axis wind turbine

Structure Analysis for Tunnel Longitudinal Deformation Based on Segment Dislocation Mode

AbstractAccording to tunnel structure around joints, tunnel longitudinal deformation is analyzed and a three-dimensional finite element model is built based on segment dislocation mode. Tunnel structure stress analysis is conducted from two aspects of segment in the shear and bolt in the tension. The analysis results show: (1) Segment shear model. When segment dislocation reaches 0.03mm, the principal stressσ1 exceeds 3.0Mpa which is over concrete's tensile strength. Therefore, when convex tenon and concave tenon generate shear, there must be horizontal slipping and bolt is tensioned. (2) Bolt tension model. When joint opening value reaches 2mm, bolt stress exceeds 640Mpa, which is bolt's yield strength. When joint opening value reaches 6mm, which is the waterproof control standard for tunnel, bolt stress reaches 688.7Mpa, which is less than bolt's failure strength. The subway tunnel's structure safety should be controlled from the perspective of waterproof

Anisotropic Pauli spin-blockade effect and spin-orbit interaction field in an InAs nanowire double quantum dot

We report on experimental detection of the spin-orbit interaction field in an InAs nanowire double quantum dot device. In the spin blockade regime, leakage current through the double quantum dot is measured and is used to extract the effects of spin-orbit interaction and hyperfine interaction on spin state mixing. At finite magnetic fields, the leakage current arising from the hyperfine interaction is suppressed and the spin-orbit interaction dominates spin state mixing. We observe dependence of the leakage current on the applied magnetic field direction and determine the direction of the spin-orbit interaction field. We show that the spin-orbit field lies in a direction perpendicular to the nanowire axis but with a pronounced off-substrate-plane angle. It is for the first time that such an off-substrate-plane spin-orbit field in an InAs nanowire has been detected. The results are expected to have an important implication in employing InAs nanowires to construct spin-orbit qubits and topological quantum devices.Comment: 20 pages, 5 figures, Supporting Informatio

Landslides Triggered by Typhoon Morakot in Taiwan

Landslides are general geomorphic erosion processes on hillslopes and can usually cause severe threats to human life and property due to their unexpected occurrence and fast traveling. Typhoon Morakot (in 2009) released more than 2000 mm rainfall during 6 days at the beginning of August 5 in Taiwan, leading to a large number of landslides, especially in southern Taiwan. Here we significantly devote this chapter to address the causes and effects of landslides in Cishan River watershed accompanied with the primary factors of landslide triggering such as the geologic and topographic settings and rainfall characteristics. We evaluate the devastation of landslides caused by Typhoon Morakot and its aftermath, and also assess the present status of landslide hazards mitigation strategies in Taiwan