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16:00   Aerodynamics; new wind tunnels and sailing Chair: Len Brownlie 16:00 20 mins NEW WIND TUNNEL FACILITY DEDICATED FOR SPORTS TECHNOLOGY RESEARCH AND DEVELOPMENT Mikael Backström, Peter Carlsson, Jonas Danvind, Andrey Koptyug, David Sundström, Mats Tinnsten Abstract: Objective testing of new garments, footwear and equipment for sports and outdoor activities is a challenge designers, researchers and industry are constantly facing. Outdoor tests are the most realistic, but the same time quite complex and demanding special measurement technology. The results of such tests are often hard to interpret because of the rapidly varying ambient conditions, and individual specifics of test human subjects. Common alternative is provided by the indoor tests made in stable controlled environment. The same time controlling such parameters as temperature, wind, humidity with indoor facilities replicating all ambient conditions needed for the testing is a complex undertaking. Significant amount of research and development related to the behavior of sports equipment at high speeds and windy conditions is carried out in wind tunnels. But the dominant majority of such facilities are designed and constructed for automotive and aerospace sectors. A new wind tunnel facility opened in March 2015 at Sports Tech Research Centre of Mid Sweden University is up to date the only one designed under direct control of the sports technology specialists and dedicated primarily to the research and development within sports and outdoor sector. Constructing such dedicated facility had a main goal of replicating ambient conditions for training and equipment testing in a controlled manner, including such parameters as wind speed, temperature and, uniquely, rain. This wind tunnel is housing one of the largest treadmills (5 m long and 3 m wide), which can be adjusted for leveled, uphill and downhill motion, placed inside the channel of 10 m2 with varying wind speeds. Wind speed can be adjusted to match the treadmill speed or independently up to approximately 65 km/h (without narrowing the wind channel). Sprinkler system can generate the rainy conditions from the fine mist to the heavy monsoon. Present work reports on the details of new wind tunnel construction, results of its validation and first studies carried out in this facility. As this facility is open for wide international cooperation we also report on the general directions of research we are planning to carry out in this facility. 16:20 20 mins DESIGN AND CONSTRUCTION OF AN OPEN-CIRCUIT WIND TUNNEL WITH SPECIFIC MEASUREMENT EQUIPMENT FOR CYCLING Bert Celis, Harm Ubbens Abstract: Cycling rules and regulations subjected by the Union Cycliste International (UCI) bound the design spectrum of sports engineers concerning the global shapes of bicycles and cycling gear. In order to gain profits the micro-aerodynamics and attitudes of cyclists and their gear must be investigated. Examinations of the micro-aerodynamics of cycling clothing and bicycles and the attitude of the athletes on their bikes are part of the research goals of Flanders’ Bike Valley. This cluster collaboration therefore invested in building a cycling wind tunnel. This paper will discuss the detail design of the wind tunnel and focusses especially on the test section with its measurement devices. Due to the limited available building space the wind tunnel configuration is of the open circuit suction type, which can host a tandem pair of cyclists in the test section of 6.5 meters length with a squared 2.5 meter diameter. Next to the balance to measure the drag of the object in the wind tunnel, two main measurement systems are included to measure the attitude of the cyclist and micro-aerodynamics in the airflow. The attitude of the cyclist is measured by two camera bars on either side of the test section which records infrared spots on the body joints of the cyclist. Positioning of the athlete can improve the performance and stability of the cyclist and reduce the risk of injuries. Two camera bars are used, in comparison to a single bar for most bikefitting equipment, to correct for the possible asymmetrical position on the bike. The micro-aerodynamics of the airflow is measured with the use of Particle Image Velocimetry (PIV). This camera-laser system captures multiple shots of the airflow, with added oil particle, to see the relative movement of these particles, and hence the airflow. Flanders’ Bike Valley, founded by Ridley Race Productions, BioRacer, Lazer, Voxdale and Flanders’ Drive, has currently 45 members and strives for open innovation in the cycling industry. Next to the wind tunnel tests Flanders’ Bike Valley hosts an incubation centre to encourage the joint go-to-market strategies of multiple companies to bring new and innovative products on the market. 16:40 20 mins NUMERICAL PREDICTION OF THE OPTIMAL HEEL AND TRIM OF A LASER DINGHY Miikka Pennanen, Rickard Lindstrand Levin, Lars Larsson, Christian Finnsgård Abstract: As the Laser Olympic dinghy is one of the highest-level sail racing classes in the world, there is an interest in obtaining physical facts around the experience that already exist. For this reason, a numerical investigation has been carried out to find the best heel and trim angles in upwind sailing. Flat water is assumed. The core of the work is a newly developed Inverse Velocity Prediction Program (IVPP) that computes the required wind speed for a given boat speed. Input to the program is both available towing tank data and CFD results. By keeping speed constant interpolation is avoided in the very non-linear resistance-speed relation, reducing considerably the required number of CFD computations. Another reduction is obtained by a special technique for avoiding interpolation in leeway. Systematic CFD computations are carried out to find the optimum trim versus heel at the speeds 2, 3, 4, 5 knots. Using this relation the required wind speed at the four boat speeds can be expressed as a function of heel only. The heel angle corresponding to the smallest wind speed is the best. Knowing this, and the corresponding optimum trim, the position of the sailor is computed. It turns out that the predicted best positions correspond well with practical experience. However, the results highlight the benefit of a small heel in higher winds, which often is regarded as undesired by sailors