Yukimaru Shimizu

Wind Tunnel Study of the Interaction between Two Horizontal Axis Wind Turbines

Interactions between neighboring wind turbines in complex terrain are complex and many problems are still unsolved. This paper, through wind tunnel tests, investigates the interaction between two horizontal axis wind turbines (HAWTs) under two different flow patterns. The purpose of the study is to begin to obtain fundamental procedures for arranging turbines in a wind farm in a complex terrain, with no-fixed intervals between wind turbines and different wind conditions. The main factors investigated are: (1) experimental analysis of the wake behind HAWTs, (2) performance measurements of the HAWTs, and (3) detailed investigation of interaction between two HAWTs. The results include the effects of inflow velocity, turbulence intensity and turbine array on wind turbine output power as affected by the wake.

Studies on a horizontal axis wind turbine with passive pitch-flap mechanism (performance and flow analysis around wind turbine)

We describe the development of a passive system to control the output power of a horizontal axis wind turbine. This pitch-flap coupling mechanism can reduce rotor power above rated wind speed. This mechanism has two kinds of blade motions: the flapping and the pitching motions. Braking effects are investigated experimentally

Power Augmentation Effects of a Horizontal Axis Wind Turbine With a Tip Vane—Part 1: Turbine Performance and Tip Vane Configuration

This paper describes the experimental results of output power augmentation of a horizontal axis wind turbine with a tip vane. In order to find the relationship between the performance of the turbine and the configuration of the tip vane, various types and sizes were used. It was found that V-type and S-type tip vanes can improve turbine performance. Also, the dimensions of V- and S-type tip vanes were investigated. The maximum improvement achieved was a 25 prevent increase in power in a existing wind turbine without a tip vane.

Power Augmentation of a HAWT by Mie-type Tip Vanes, considering Wind Tunnel Flow Visualisation, Blade-Aspect Ratios and Reynolds Number

Wind tunnel results are reported concerning the effects of blade aspect ratio and Reynolds number on the performance of a horizontal axis wind turbine (HAWT) with Mie-type1 tip attachments. The flow behaviour around the blade tips and the Mie-type tip vanes is presented. Detailed surface oil film visualization and velocity measurements around the blade tips, with and without Mie vanes, were obtained with the two-dimensional, Laser-Doppler Velocimetry method. Experiments were performed with rotors having blades with different aspect ratio and operating at different Reynolds numbers. The properties of the vortices generated by the Mie vanes and the blade tips were carefully studied. It was found that increased power augmentation by Mie vanes is achieved with blades having smaller aspect ratio and smaller Reynolds number.

Power Augmentation Effects of a Horizontal Axis Wind Turbine With a Tip Vane—Part 2: Flow Visualization

We present a discussion of the physics of the flow discussed in our first report. By visualizing the flow around the tip vane, the following results were drawn: 1) The strength of the tip vortex, the induced drag and turbulence on the blade tip can be diminished with a tip vane. 2) The inflow rate to the rotary surface of wind turbine can be increased with the tip vane

Rotor Configuration Effects on the Performance of a HAWT With Tip-Mounted Mie-Type Vanes

In this paper, the relationships between the power augmentation of a HAWT due to Mie-type tip vane application and other factors influencing the efficiency of a wind turbine such as the blade aspect ratio, number of blades, blade pitch angle and Reynolds number are investigated. Experiments were carried out in a wind tunnel with an open, 3.6 m diameter, test section. Rotor models included two- and three-blade upwind turbines with four sets of blades with different aspect ratios. With the rotor blades tested, a maximum power augmentation of about 14.5% was achieved due to Mie vane application. The relationships between power augmentation due to the Mie vane and the above factors are investigated. It is found that the application of a tip-mounted Mie vane results in a larger increase in maximum power coefficient for rotors with smaller aspect ratios and for lower wind speeds. Surface oil film and surface tuft visualization methods were used to detect the flow patterns at the blade tip. Addition of the Mie vanes causes significant changes in flow behavior near the blade tip, resulting in additional blade lift.

Secondary Flow and Hydraulic Losses Within Sinuous Conduits of Rectangular Cross Section

This paper describes the relationship between hydraulic losses and secondary flow within sinuous conduits with complicated bends. It has been found that the nature of secondary flow present in the bends is quite sensitive to the geometric configuration of the bend and the actual aspect ratio of the conduit section. Indeed, many different secondary flow patterns have been found to exist as the bend geometry is altered. A wide range of experiments has been conducted for various aspect ratios of a rectangular conduit with different curvatures.

Studies on Performance and Internal Flow of U-Shaped and Snake-Shaped Bend Diffusers: 2nd Report

Influence des rapports de section, des angles et des courbures des differents elements du diffuseur

Studies on Performance and Internal Flow of Twisted S-Shaped Bend Diffuser—The So-Called Coiled Bend Diffuser: 1st Report

This paper is the result of our research into the twisted S -shaped bend diffuser—the so-called coiled bend diffuser. It is a diffuser with a centerline in the shape of a twisted “S .” Our studies show that the performance characteristics of this bend diffuser are greatly improved when interaction by the bend elements generates an adequate secondary flow inside the diffuser. Full consideration was given to the influence of the divergent angle of the bend elements, consisting of the diffuser or curvature radius ratio of the bend, on these performance characteristics. The relation between diffuser performance and internal flow also was studied. Some guidelines for designing such a high performance diffuser is given.

Experimental Study for Mutual Interference between Two Horizontal Axial Wind Turbines (In Case of Wind Tunnel Tests for Two Kinds of Artificially Generated Flow Patterns).

The mutual interference of plural wind turbines becomes important when many wind turbines are located in large-scale wind farm. Several papers have analyzed the problems of mutual interference among plural wind turbines. However, the effects of boundary layer profile and turbulence in wind for mutual interference of plural horizontal axis wind turbines (HAWTs) are still unknown enough. In order to solve such problems, extensive experiments were performed in a large-scale wind tunnel. The paper describes the following points, (1) experimental analysis of wake behind HAWT for two different flow patterns, (2) relationships between HAWT performances and two different flow patterns, (3) detailed investigation for mutual interference between two HAWTs, through wind tunnel testing for two kinds of artificial flow patterns.