#: locale=en ## Tour ### Description ### Title tour.name = A-Tunnel ## Media ### Title panorama_8CB7F024_85CB_A8E7_41DD_FF2DCE168A17.label = PIC_20160211_163930_20210209082913 panorama_8CB82AF8_85CB_B96F_41C5_10A248A1CCD3.label = PIC_20201209_131114_20210209082908 panorama_8CB8F4FF_85CB_A961_41C2_D808EA873DAB.label = PIC_20201209_131439_20210209082908 panorama_8F2AE29F_85CB_69A1_419A_E7348C39319E.label = PIC_20160211_163727_20210209082908 ## Hotspot ### Tooltip HotspotPanoramaOverlayArea_8112BAEE_8AA2_1B31_41BA_8380013BB478.toolTip = On the top most floor, you would find the collector, \ which is covered with acoustic absorbing foam that splits the flow towards the return leg of the A-tunnel. \ Splitter silencers are used for absorbing the background noise. \ There are two sets of silencers on each side of the fan room. \ Each set of silencers consists of three blocks of acoustic absorbing foam of 0.2 m width, 2.5 m length and 2.6 m height. \ These blocks have a separation between each other of 0.1 m. \ The inner walls of the airline in this section are also covered with acoustic absorbing foam, ensuring maximum sound absorption in the frequency range of interest. \ This leads to an engine on either side, where flow is accelerated through the contraction by a pressure difference generated by two Ferrari industrial centrifugal fans from the collector to the contraction nozzle. \ The fans provide a maximum volumetric air flow per fan of approximately 13500 m3/h and a maximum static pressure discharge of approximately 9000 Pa. \ Each fan has ten rotor blades and an installed power of 30 kW. \ Thus, at the maximum rotational speed (about 3000 rpm), the expected blade passing frequency (BPF) is approximately 500 Hz. \ The accelerated flow again goes to the collector and the process is continuous. It is truly a work of art. HotspotPanoramaOverlayArea_81741812_8A9E_0716_41D5_2879D65490B0.toolTip = On the top most floor, you would find the collector, \ which is covered with acoustic absorbing foam that splits the flow towards the return leg of the A-tunnel. \ Splitter silencers are used for absorbing the background noise. \ There are two sets of silencers on each side of the fan room. \ Each set of silencers consists of three blocks of acoustic absorbing foam of 0.2 m width, 2.5 m length and 2.6 m height. \ These blocks have a separation between each other of 0.1 m. \ The inner walls of the airline in this section are also covered with acoustic absorbing foam, ensuring maximum sound absorption in the frequency range of interest. \ This leads to an engine on either side, where flow is accelerated through the contraction by a pressure difference generated by two Ferrari industrial centrifugal fans from the collector to the contraction nozzle. \ The fans provide a maximum volumetric air flow per fan of approximately 13500 m3/h and a maximum static pressure discharge of approximately 9000 Pa. \ Each fan has ten rotor blades and an installed power of 30 kW. \ Thus, at the maximum rotational speed (about 3000 rpm), the expected blade passing frequency (BPF) is approximately 500 Hz. \ The accelerated flow again goes to the collector and the process is continuous. It is truly a work of art. HotspotPanoramaOverlayArea_88F39CE6_85DF_7963_41B8_02BF7D72DDE2.toolTip = Welcome to the ground floor!! \ What you see here is a rounded inlet to the contraction which was computationally designed in order to ensure smooth inlet conditions and avoid flow separation in the full regime. \ The lip was designed as a 2:1 ratio ellipse and constructed in three segments which were 3D-printed (see below for additional details). \ To further ensure minimal flow separation, the inlet is furnished with a coarse screen mesh of approximately 57% open area, \ providing a mild pressure jump to stabilize the flow. Downstream of the flow straightener, four anti-turbulence screens are arranged at an interval distance of 200 mm. \ The screens are made of rectangular stainless steel meshes of diameter 0.25 mm and with a cell size of 1 mm arriving at an open area coefficient of 64.5%. \ The four screens are pre-tensioned and installed on removable wooden rings, facilitating periodic maintenance and cleaning. \ Let’s go to the happening place !! HotspotPanoramaOverlayArea_9457EAF3_8626_0BEA_41D5_7E98EE50FA21.toolTip = Go up, mid floor (Happening place !!) HotspotPanoramaOverlayArea_9514D4C2_8666_1E2A_41C5_76993540FAC0.toolTip = Go up, top floor of the tunnel HotspotPanoramaOverlayArea_9797AB80_8666_0A25_41D4_7D2D19D01805.toolTip = The acoustic array is another impressive addition to the tunnel. \ It currently consists of 64 G.R.A.S. 40PH analog free-field microphones with integrated constant current power (CCP) amplifiers installed inside of the anechoic plenum of the wind-tunnel. \ Each microphone has a diameter of 7 mm and a length of 59.1 mm. \ It was decided to employ three steel perforated plates with square holes in a regular grid pattern to fit the microphones. \ Each plate has a dimensions of 1 m x 2 m and has a total of 8450 perforations, \ i.e. possible microphone positions. \ This design offers a compromise solution between reduced acoustic reflections, \ robustness and a large number of potential microphone positions. HotspotPanoramaOverlayArea_979F693E_861A_365D_41D6_2B464060FB43.toolTip = You see melamine foams which act as acoustic absorbers. \ A common criterion to determine the geometry of the acoustic foam wedges is that the total height of the wedge should be larger than or equal to a quarter of the acoustic wavelength (k=4) of the design frequency cut-off. \ The selected wedge geometry (with a total height of 0.49 m) should allow for free-field propagation of sound for frequencies above approximately 173.5 Hz. \ The floor was covered with the same type of acoustic absorbing foam with an additional metal grid on top of it with square grid holes of 10 mm side. \ The grid allows access to the wind-tunnel facility and the transport of measurement equipment, \ while not generating unwanted sound reflections within the frequency range of interest HotspotPanoramaOverlayArea_97D67774_866A_3AED_41CA_10E2993FBA62.toolTip = What you see here as an example is a scaled down model of a landing gear, \ for the analysis of noise reduction strategies. Landing gear noise is now a substantial contributor to the overall noise scattered by aircraft, \ especially during landing. \ As such, it causes disturbance to people living in the vicinity of aerodromes. \ For this reason, a significant body of research proposing different noise abatement approaches has been recently developed. \ One of the most promising strategies is the employment of porous fairings upstream the undercarriage. \ In the framework of the EU H2020 research program INVENTOR, \ TU Delft is currently working with different partners to identify permeable materials that can optimize noise abatement for specific working conditions. \ Specifically, TU Delft’s role includes the experimental characterization of scaled baseline and treated models in order to identify the most promising materials, \ and the study of the mechanism responsible for noise abatement employing numerical tools, \ such as the LBM solver PowerFLow. HotspotPanoramaOverlayArea_986B02FB_866A_7BDA_41C8_CE2EFBD35E46.toolTip = Go down, midfloormid floor \ of the windtunnel HotspotPanoramaOverlayArea_9D1017C2_8666_1A25_41DF_9293539D1DCF.toolTip = Go down, groundfloor of the windtunnel