Naar een beter begrip van lokale windbelastingen in de stedelijke omgeving

Wat is de invloed van een gebouw op de windbelasting van de gevel- en dakelementen van een nabijgelegen gebouw? Het antwoord op die vraag is van belang voor een veilig ontwerp van gevel- en daksystemen. Okke Bronkhorst onderzoekt deze invloed in het kader van zijn promotieonderzoek aan de Technische Universiteit Eindhoven

Spectral analysis of pressures measured on two high-rise building models in side-by-side arrangement

Pressure measurements on an isolated square plan form high-rise building model and two square high-rise building models in side-by-side arrangement were analysed using the Fast Fourier Transform (FFT) to define peak frequencies resulting from interference. For the isolated building model, a peak in the power spectrum was determined on the side face at a reduced frequency of fred = fB/UH = 0.08. This value corresponds with St = 0.09, which is a typical value for the vortex shedding process for this type of model. In the side-by-side arrangement, spectral peaks were observed at fred = 0.03, 0.09, and 0.12 on the face inside the passage. The first peak is related to vortex shedding of the combination of two models, the second peak to vortex shedding of the single model. The last peak is caused by reattachment of the shear layer. Analysis of the reduced power (fSpp/qH2) in three frequency bands, fred = 0.01 – 0.06, 0.06 – 0.11 and 0.11 – 0.16, shows an increase in power near the entrance and a decrease near the exit of the passage in all bands with decreasing separation distance. These changes in the spectral power distribution indicate the processes related to the determined spectral peaks (fred = 0.03, 0.09, and 0.12) increase in intensity, but their region of influence in the passage decreases

Wind tunnel and CFD modelling of wind pressures on solar energy systems on flat roofs

Design of solar energy mounting systems requires more knowledge on the wind patterns around these systems. To obtain more insight in the flow patterns, which cause the pressure distributions on the solar energy systems, a wind tunnel test and Computational Fluid Dynamics analysis have been performed. In this study the average pressure coefficients, determined in the wind tunnel measurements, are compared with Reynolds Averaged Navier-Stokes calculations. The comparison, based on the median of all observations over 6 wind directions and all pressure points, showed that the general pressure distribution is well predicted. Overall differences were found of 39% for the Renormalization Group k-e turbulence model, 35% for a differential Reynolds Stress turbulence model with wall reflection term and 35% for a differential Reynolds Stress turbulence model without wall reflection term. The largest differences are observed in the wake of systems that have a large spacing, which is due to an incorrect prediction of the separation zones and therefore the shielding effect of the solar energy systems

A comparison of peak pressure interference factors for high-rise buildings determined in two ABL wind tunnels

Pressure measurements were performed on various configurations of two high-rise building models in two atmospheric boundary layer wind tunnels in the Netherlands. A comparison was made of the interference factors of the minimum and maximum peak pressures over all pressure taps at 0 degree angle of incidence obtained for measurements on the configurations with an interfering model of similar size and shape as the reference model. Both studies observed increases of 30-40% in the minimum and maximum peak pressure for the tandem arrangement configurations (Y = 0) with the interfering model at (X = 4B – 6B). Both studies furthermore determined that when the interfering model is positioned at a distance Y > 3B, there is no influence on the maximum peak pressures over all pressure taps. For an interfering model in the region (X, Y) = (2.5B – 6B, B – 6B), both studies observed increases in minimum peak pressure ranging between 10-50%

Norm, windtunnel of CFD?

Door de nog altijd toenemende rekenkracht van computers komen op vele werkterreinen steeds geavanceerdere modellen beschikbaar. Voor de bepaling van windbelastingen op gebouwen wordt echter nog altijd gebruikt gemaakt van oude methoden: normbladen en windtunnelonderzoek. Uiteraard zijn die doorontwikkeld maar een doorbraak van een rekenkundig alternatief - met Computational Fluid Dynamics (CFD) - is uitgebleven. Een belangrijke reden is dat CFD nog altijd zeer veel rekenkracht eist. En dan nog is het niet zonder meer bruikbaar

Effects of Background Noise and Visual Training on 3D Audio

Spatial audio or 3D audio as an information channel is increasingly used in various domains. Compared to the multitude of synthetic visual systems and 3D representations, audio interfaces are underrepresented in modern aircraft cockpits. Civil commercial aircraft rarely use spatial audio as a supplementary directional information source. Although, different research approaches deal with the benefits of spatial audio. In 3D audio simulator trials, pilots express concern over distractions from background noise and possibly mandatory training requirements. To resolve this, the author developed and tested a 3D audio system to support pilots in future cockpits, called Spatial Pilot Audio Assistance (SPAACE). The experiment took place at the German Aerospace Center’s Apron and Tower Simulator. The developed system creates a three-dimensional audio environment based on normal non-spatial audio. The 27 participants heard the sound through an off-the-shelf aviation-like stereo headset. The main subject of investigation was to evaluate if air traffic control background noise affects spatial perception. The non-normally distributed location error with background noise ( Mdn=6.70∘ ) happened to be lower than the location error without air traffic control background noise ( Mdn=7.48∘ ). The evaluation the effect of visual feedback-based training was the second part of the experiment. In comparing the training session with the no-training session, the location error with training ( Mdn=6.51∘ ) is only moderately lower than the location error without training ( Mdn=7.96∘ ). The results show that humans can perceive the SPAACE audio with high precision, even with distracting background noise as in a busy cockpit environment. The effect of training was not as high as expected, primarily due to the already precise localization baseline without training