Rüdiger Höffer

Wind tunnel experiments on micro-scale dispersion of exhausts from motorways

Since exhaust gases from road traffic are mainly released in the immediate vicinity of urban areas, constructive measures are required to prevent unfavourable immissions. Up to now, the micro-scale dispersion of exhausts could not be sufficiently predicted by purely theoretical methods. At the Ruhr-University Bochum, wind tunnel experiments have been conducted. Aerodynamic similarity criteria for the atmospheric boundary layer and in particular the traffic-induced turbulence have to be considered. Comparison of time averaged concentrations, measured in situ and in the corresponding wind tunnel model, prove the reliability of this experimental tool. With this background, the influence of different noise abatement barriers on the spread of exhaust gases is systematically investigated.

Flat plate flutter derivatives – an alternative formulation

Abstract The aerodynamic derivatives for a flat plate, based on Theodorsens circulation function, are rewritten in an alternative formulation called the marine coefficient model (MC). In the MC model the flat plate expressions are simpler and physical interpretations as aerodynamic damping and aerodynamic added mass can be given. The MC model is derived from the frequently applied aerodynamic derivatives model (AD) through substitution of the independent variables.

DESIGN AND CONSTRUCTION OF A PROTOTYPE SOLAR UPDRAFT CHIMNEY IN ASWAN/EGYPT

This work is part of a joint project funded by the Science and Technology Development Fund (STDF) of the Arab republic of Egypt and the Federal Ministry of Education and Research (BMBF) of the Federal Republic of Germany. Continuation of the use of fossil fuels in electricity production systems causes many problems such as: global warming, other environmental concerns, the depletion of fossil fuels reserves and continuing rise in the price of fuels. One of the most promising paths to solve the energy crisis is utilizing the renewable energy resources. In Egypt, high insolation and more than 90 percent available desert lands are two main factors that encourage the full development of solar power plants for thermal and electrical energy production. With an average temperature of about 40 °C for more than half of the year and average annual sunshine of about 3200 hours, which is close to the theoretical maximum annual sunshine hours, Aswan is one of the hottest and sunniest cities in the world. This climatic condition makes the city an ideal place for implementing solar energy harvesting projects from solar updraft tower. Therefore, a Solar Chimney Power Plant (SCPP) is being installed at Aswan City. The chimney height is 20.0 m, its diameter is 1.0m and the collector is a four-sided pyramid, which has a side length of 28.5 m. A mathematical model is used to predict its performance. The model shows that the plant can produce a maximum theoretical power of 2 kW. Moreover, a CFD code is used to analyse the temperature and velocity distribution inside the collector, turbine and chimney at different operating conditions. Static calculations, including dead weight and wind forces on the solar updraft chimney and its solar collector, have been performed for the prototype. Mechanical loading and ambient impact on highly used industrial structures such as chimneys and masts cause lifetime-related deteriorations. Structural degradations occur not only from rare extreme loading events, but often as a result of the ensemble of load effects during the life-time of the structure. A Structural Health Monitoring (SHM), framework for continuous monitoring, is implemented on the solar tower. For the ongoing case study, the types of impacts, the development of the strategic sensor positioning concept, examples of the initially obtained results and further prospects are discussed. Additional wind tunnel tests have been performed to investigate the flow situation underneath the solar collector and inside the transition section. The flow situation in and around the SCPP has been simulated by a combination of the wind tunnel flow and a second flow inside the solar tower. Different wind tunnel velocities and volume flow rates have been measured respectively. Particle Image Velocimetry (PIV) measurements give some indication of the flow situation on the in- and outside of the solar tower and underneath the collector roof. Numerical simulations have been performed with the ANSYS Fluent to validate the experimental tests.

EXPERIMENTAL, NUMERICAL AND ANALYTICAL INVESTIGATIONS OF WIND-INDUCED NET PRESSURES FOR INDUSTRIAL BUILDINGS WITH ENVELOPE POROSITIES

The magnitude and the spatial distribution of wind-induced net pressures (external and internal) on buildings are frequently discussed among research communities and construction industries. This paper deals with this topic based on a case study about an industrial building in Denmark, which was damaged due to the wind impact during a storm when a large part of the roof covering was blown off. In order to detect the reason for the damage the wind-induced loads were studied by i) wind tunnel experiments on the external pressures due to different wind directions, ii) analytical investigations of internal pressure due to envelope porosities and planned openings and iii) numerical analyses for the internal and the external pressure. The Reynolds averaged Navier-Stokes (RANS) method is employed to build a numerical model. The experimental, analytical and numerical results are compared with the indicated characteristic loads from the Eurocode.