D. P. Coiro

Dynamic Behaviour of the Patented Kobold Tidal Current Turbine: Numerical and Experimental Aspects

This paper provides a summary of the work done at DPA on numerical and experimental investigations of a novel patented vertical axis and variable pitching blades hydro turbine designed to harness energy from marine tidal currents. Ponte di Archimede S.p.A. Company, located in Messina, Italy, owns the patented KOBOLD turbine that is moored in the Messina Strait, between the mainland and Sicily. The turbine has a rotor with a diameter of 6 meters, three vertical blades of 5 meters span with a 0.4 m chord ad hoc designed curved airfoil, producing high lift with no cavitation. The rated power is 160 kW with 3.5 m/s current speed, which means 25% global system efficiency. The VAWT and VAWT_DYN computer codes, based on Double Multiple Steamtube, have been developed to predict the steady and dynamic performances of a cycloturbine with fixed or self-acting variable pitch straight-blades. A theoretical analysis and a numerical prediction of the turbine performances as well as experimental test results on both a model and the real scale turbine will be presented and discussed.

Improving Hang-Glider Maneuverability using Multiple Winglets: A Numerical and Experimental Investigation

The main aim of this paper is to investigate the influence of multiple winglets on hang-glider climbing performance. The study aims to optimize the C 3/2 L /C D parameter. The investigation was performed both numerically and experimentally starting from airfoils and winglet shape design. Given the shape of a real hang-glider wing under aerodynamic load, the first phase of the work concerned the main geometric characteristics of winglet design: the number of winglets, airfoils, planform shape, and twist. A 3-D wing model was built and using the indications obtained from the design, different sets of winglets were built. The wing model was built to enable winglets to be applied to the wing tip without changing the wing span and aspect ratio. The tests carried out on the hang-glider model showed an improvement in wing performance of about 15 %. However, the model reproduced a full-scale wing flying under aerodynamic load and, according to the model builders, it showed a positive twist angle (leading edge up). This could mean that the winglets were more efficient because the original wing showed a strong tip vortex. A new model wing with an elliptical planform was therefore built to verify this further. The test results on the elliptical wing did not show the same improvement in performance obtained with the hang-glider model. Nevertheless, compared to the original elliptical wing an improvement was still found.

Design and Testing of a Multi-Element Airfoil for Short-Takeoff-and-Landing Ultralight Aircraft

The design and analysis of a new airfoil to be employed on a ultralight aircraft with short takeoff and landing is presented. An inverse design philosophy has been applied and is described; the numerical analysis performed used XFOIL, MSES, and TBVOR computational codes and the effects of airfoil shape on complete aircraft performances were taken into account. A high-lift configuration, including slat and single-slotted flap geometries, has been developed and is illustrated in this paper. Exhaustive wind-tunnel tests were performed at the Department of Aerospace Engineering and the experimental results are described here. To validate numerical results and to analyze the effect of laminar bubbles on airfoil performance, the pressures on airfoil surface and in the wake were measured and flow visualizations were done using fluorescent oil. The landing configuration was also tested and an experimental optimization of flap and slat positions was carried out to obtain a high maximum lift coefficient.

Numerical and experimental analysis of a shrouded hydroturbine

One of the most promising fields in energy production from renewable sources is related to the intensive exploitation of marine and river current power. This paper will illustrate the design and the performances of a shrouded hydro turbine to harness clean energy from marine and river currents. This system has been developed and tested at the University of Naples, to explore the feasibility of plants based on such idea. Two different diffusers have been designed, realized and tested. A simple designed method has been carried out in order to define the diffuser pitch angle. In order to evaluate the design diffuser angle in more accurate way a numerical simulation has been carried out. The experimental test results were compared with the bare wind turbine. The data were non-dimensionalized with respect to the disc turbine area in order to compare the ducted turbine performances with a bare turbine with the same overall size of the ducted wind turbine.

A Numerical Study on a Vertical-Axis Wind Turbine with Inclined Arms

This work focuses on a particular type of vertical-axis wind turbine, in which a number of inclined arms with airfoil-shaped cross-sections are mounted to connect the principal blades to their hub. While the majority of the known studies on vertical-axis turbines is devoted to the role of principal blades, in most of the cases without taking into account other parts of the wind turbine, the objective of this work is to investigate the effect of uncommon arm geometries, such as the inclined arms. The inclined arms are known to have a potentially beneficial role in the power extraction from the wind current but, due to the complexity of the phenomena, the investigation on aerodynamics of this type of turbine is often impossible through analytical models, such as blade-element momentum theory. It turns out that adequate studies can only be carried out by wind tunnel experiments or CFD simulations. This work presents a methodical CFD study on how inclined arms can be used on a selected wind turbine configuration to harvest additional power from the wind. The turbine configuration, geometry, and some fundamental definitions are introduced first. Then an in-depth CFD analysis is presented and discussed.

Prediction of Aerodynamic Performance of Airfoils in Low Reynolds Number Flows

In many industrial applications the evaluation of the influence of laminar separation can be fundamental for the prediction of accurate global and local aerodynamic performances; this is the case of wing sections operating at low Reynolds numbers.

Fuzzy logic control for a small pitch controlled wind turbine

In this paper a control system for a pitch controlled variable speed wind turbine is described and analyzed. One of the main control system goals is to limit the aerodynamic power produced by the wind turbine to the nominal power in high wind speed region. In turbulent wind environment the power production control becomes difficult due to fluctuation of the wind speed. A fuzzy logic based control system was designed and investigated for a 60 kW mini wind turbine. A wind turbine aeroelastic model was developed in order to simulate the turbine behavior for different intensity of turbulent wind. Both the designed fuzzy logic control system and a classical PID control system were simulated and the results in terms of turbine rpm and power production were compared.

Experimental tests of GEM- Ocean's kite, an innovative patented submerged system for marine current energy production

This paper presents some recent experimental results of towing tank tests on an innovative system configuration for clean energy applications. This concept has been already tested on a preliminary prototype model at the University of Naples. The original concept consists of a submerged floating body linked to the seabed by means of a tether. Electrical generators and auxiliary systems are housed within the hulls of the floating bodies. Two turbines are installed on a support structure exposed to the flow. This is the basic concept of what we call here the “GEM system” (Generatore Elettrico Marino, Marine Electrical Generator) or “Oceans kite” configuration.

Harnessing marine current energy with tethered submerged systems: Experimental tests and numerical model analysis of an innovative concept

An innovative system concept in marine/river current technologies is presented. A floating submerged body is used as a support to turbines and a casing for electrical and control systems. A series of experimental test has been performed in a towing tank on a test model using already characterized turbines, in order to evaluate its behavior in response to current actions. The present paper is aimed to report the results of such tests and to obtain a simple dynamic model to compare with experimental results.

Improving Aircraft Endurance Through Turbulent Separation Control by Pulsed Blowing

Boundary-layer unsteady blowing is one of the most advanced solutions for reducing aircraft parasite drags and flow separation at high angles of attack. It allows high lift along with low drag to be achieved and, because endurance is one of the most important performance parameters for certain types of aircraft, such as unmanned aerial vehicles, clearly the CL 3/2 /CD ratio has to be maximized. The main goal of the present investigation is to explore possible ways to obtain efficient turbulent boundary-layer control and, at the same time, to consider the practical problems connected to the installation of the device in a real wing. This study seeks mainly to verify the effectiveness of active control via pulsed blowing as a tool to delay boundary-layer separation. Numerical simulations and wind-tunnel experimental investigations on a wing model equipped with instruments are presented and the results discussed. An extensive numerical and experimental investigation on the parameters that can affect flow separation has been carried out. As a result of this analysis, it seems that tubing length produces the most significant effect on the resonant frequencies of a pulsed-blowing system, whereas slot exit and cavity volume mainly affect the resonant peak amplitude. The best actuation frequency varies, depending on the type of aerodynamic performance to be optimized (efficiency, lift, or endurance).