Estimation of Forces Acting on a Sailboat Using a Kinematic Sensor

Amateur keel boat racing has becoming more and more popular on coastal regions with an old sailing tradition, such as in Adriatic. Although the traditional experience is transmitted to new generations of skippers and crews that compete on national and international regattas with open class boat, the material limits of the boat are often measured subjectively, by sail or mast failure, and transmitted by a story. Most sailors know why some component failed, but often they don’t know what force was needed for the particular failure. Forces acting on a boat are usually estimated with CFD and towing tank experiment for relevant sailing conditions, but full scale data in seaway are rarely taken. Here we wanted to show a low budget method to get a rough estimate of aerodynamic and hydrodynamic forces acting on a keel sailboat using a kinematic sensor. Some approximations are taken into account to construct a simplified mathematical sailboat model, which allow to relate kinematic data to forces acting on sail, hull, keel and rudder. Some data as the geometry and mass distribution of the boat has to be known, other parameters such as water resistance instead has to be experimentally measured. Results of a series of measurements are presented and discussed. Looking on the limitations of such a method, a proposal for a new sensor is made.

Towing Tank Experiments for Flapping-Wing Aerodynamics

This paper presents an empirical approach for flapping-wing aerodynamics using a servo-driven towing tank and a dynamically scale-up robotic manipulator. Time-varying aerodynamic force and moment were measured, and digital particle image velocimetry in multiple cross-sections were conducted. Three case studies showed that the towing tank experiment could be an effective way to investigate the aerodynamic characteristics in detail, which are difficult to be predicted by other conventional approaches. The force and moment measurements clarified that an advance ratio has significant role in governing the LEV behavior and consequent aerodynamic performance of flapping wings. Results for moving sideways showed the effects of the wing-wing and wing-body interaction, and the usefulness of the towing tank experiments for analyzing the flight dynamic characteristics. It was also shown that the towing tank experiments can be applicable to realistic wing motions; test results using the wing kinematics of a living insect in forward flight were well compatible with the trim condition of the insect.

Aerodynamic Characteristics of a Road Vehicle in Steady-State Cornering

The objective of this study was to investigate the aerodynamics of a road vehicle during cornering. We focused on steady-state cornering and divided the vehicle motion into two components, a yaw rotation and a sideslip motion. The fluid-dynamic characteristics of the vehicle in steady-state cornering and the effects of the two motion components were investigated both by a towing tank experiment and by numerical simulation. The results indicate that both of the motion components generated fluid-dynamic centripetal force and fluid-dynamic yaw moments in opposite directions. The distributions of pressure change on the vehicle body, generated by the motion components, were numerically visualized. The physical mechanisms that generated these aerodynamic characteristics are discussed.

A three dimensional non-hydrostatic model for turbulent air flow

A finite-volume code is developed to compute the turbulent airflow over small- scale complex terrain. A pressure-correction algorithm is used to solve the three-dimensional non-hydrostatic flow equations. The turbulent transport is simulated by the k- € model using some modifications suitable for atmospheric boundary-layer application. As an example, the model is used to simulate the flow-field around a cubical building. The same flow as a towing-tank experiment of USEPA was simulated using our code. These simulations show that, the model was capable of simulating recirculation zones behind the building. The results of calculation are also compared with available measurement data.