The low acoustic noise and turbulence wind tunnel of the University of Sao Paulo

This paper introduces the Low Acoustic Noise and Turbulence (LANT) wind tunnel of the Sao Carlos School of Engineering, University of Sao Paulo (USP-EESC), Brazil. The closed-loop wind tunnel features several devices to improve flow uniformity, reduce swirl, and lower the background acoustic noise and turbulence, enabling stability and aeroacoustic experiments. The design criteria was based on the best practices reported, in particular for low turbulence wind tunnels. Yet, these criteria are conflicting and we discuss the decisions that had to be made and present flow quality results that were achieved. The 16-bladed axial fan with 13-blade stators is driven by a variable-speed electric motor. At the corners, 100 mm dense acoustic foam is installed on the vertical walls, floor and ceiling, and the turning vanes are filled with acoustic-absorbing material. The long settling chamber contains a 3.175 mm mesh hexagonal honeycomb and five fine mesh nylon screens, ending in a 7:1 area ratio short contraction. The 3-m long closed-working section has a $1\times 1\ {\rm m}^2$ cross-section area. At 15 m/s the working section wall boundary layer is less than 100 mm thick, providing an area of at least $800\times 800\ \mathrm{mm}^2$ where the streamwise flow uniformity was within 1%. In the 10–30 m/s flow speed range, the turbulence intensity ranged from 0.05% to 0.071% and the background acoustic noise level, obtained with an inflow microphone, ranged from 90 and 110 dB. A benchmark experiment on a flat plate boundary layer produced an almost perfect two-dimensional Blasius profile up to $Re_x \approx 2.5 \times 10^6$ . A beamforming benchmark experiment on aeroacoustics accurately identified the sound emitted by a cylinder immersed in the flow.

Direct velocity measurements in high-temperature non-ideal vapor flows

Direct velocity measurements in a non-ideal expanding flow of a high temperature organic vapor were performed for the first time using the laser Doppler velocimetry technique. To this purpose, a novel seeding system for insemination of high-temperature vapors was specifically conceived, designed, and implemented. Comparisons with indirectly measured velocity, namely inferred from pressure and temperature measurements, are also provided. Nozzle flows of hexamethyldisiloxane (MM, C$$_6$$ 6 H$$_{18}$$ 18 OSi$$_2$$ 2 ) at temperature up to $$220\,^\circ \mathrm {C}$$ 220 ∘ C and pressure up to 10 bar were taken as representative of non-ideal compressible-fluid flows. The relative high temperature, high pressure and the need of avoiding contamination pose strong constraints on the choice of both seeding system design and tracer particle, which is solid. A liquid suspension of tracer particles in hexamethyldisiloxane is injected through an atomizing nozzle in a high-temperature settling chamber ahead of the test section. The spray droplets evaporate, while the particles are entrained in the flow to be traced. Three different test cases are presented: a subsonic compressible nozzle flow with a large uniform region at Mach number 0.7, a high velocity gradient supersonic flow at Mach number 1.4 and a near-zero velocity gradient flow at Mach number 1.7. Temperature, pressure and direct velocity measurements are performed to characterize the flow. Measured velocity is compared with both computational fluid dynamics (CFD) calculations and velocity computed from pressure and temperature measurements. In both cases, the thermodynamic model applied was a state-of-the-art Helmoltz energy equation of state. A maximum velocity deviation of 6.6% was found for both CFD simulations and computed velocity. Graphical abstract

A flow and acoustic facility for characterization of liner and meta-acoustic surfaces under grazing flow condition

The Hong Kong University of Science and Technology (HKUST) has designed and assembled a new facility, a grazing flow tube, for aeroacoustic characteristics measurement of acoustic liners, e.g. transmission loss, impedance, etc., under a high-speed grazing flow. The cross-section of the test section of the tube has a dimension of 50 mm × 50 mm, and the grazing flow speed can be up to 0.3 Ma. A settling chamber, a long-enough flow development section and a multi-stage anechoic termination are adopted to ensure the high-quality flow field and acoustic field. This paper presents the detailed designs of the key components of the facility, as well as the calibrations of the velocity profile in a series of cross-section surfaces of the duct along the streamwise direction and sound pressure distributions in the axial and circumferential directions. Pitot tube, Hotwire and PIV are used to obtain the flow field measurement results. The overall performance of the diagnostic facility is verified by comparing the impedance results of acoustic liners acquired from an impedance tube under the static condition and the theoretical variation of axial wavenumber with Ma number under the grazing flow.

Modeling and Wind Flow Analysis of an Eiffel (Open) Type Sub-Sonic Wind Tunnel

Wind tunnel (WT) is a device that artificially produces airflow relative to a stationary body and measures aerodynamic force and pressure distribution, simulating the actual conditions with an important aspect of accurately feigning¬ the full complexity of fluid flow. The aim of the present study is to design the three dimensional geometry of a small, open-circuit (also known as Eiffel Type), and subsonic (low speed) wind tunnel (WT) capable of demonstrating or acting as a vital tool in aero-mechanics research. The project and fabrication itself, poses as an onerous task with the cynosure/central theme being the delineation/depiction of wind tunnel components such as Test Section, contraction cone, diffuser, drive system and settling chamber.

Observational Simulation of Extreme Weather Conditions and Aviation Meteorology Applications

<p>Observations and prediction of extreme weather (Wx) conditions are important for land, air and sea or water transportation applications. These conditions adversely affect the economic and social life of people.  Extreme Wx conditions for aviation operations for example, include, gust (Ug), wind (Uh), and turbulence (U’), low visibility (Vis), fog and frost, and icing as well as heavy precipitation. These conditions can be studied either in the natural atmosphere or in the laboratory. There have been several aircraft and balloon based in-situ studies related to extreme Wx conditions affecting aviation operations.  However, studying extreme Wx conditions from aircraft observations is limited due to safety and sampling issues, instrument uncertainties, and even the possibility of the aircraft producing its own physical and dynamical effects. Remote sensing-based techniques (e.g., retrieval techniques) for studying extreme Wx conditions usually represent a volume that cannot characterize the important scales, and also represents indirect observations. Therefore, climatic wind tunnel simulations of atmospheric processes together with field observations can help us to better evaluate the interactions among microphysical and dynamical processes affecting extreme Wx conditions e.g., cold air temperatures (Ta) and low/high relative humidity with respect to water (RHw). The Climatic Wind Tunnel (CWT) in the Automotive Centre of Excellence (ACE) at the Ontario Tech University has a large semi-open jet test chamber with a flow area of 7-13 m<sup>2</sup> that can precisely control Ta down to -40ºC, and Uh up to 250 km hr<sup>-1</sup>.  Ice and liquid phases of particle size distributions n the CWT are measured with optical probes such as GCIP, CDP, BCP, FMD, and LPM probes (Gultepe et al 2019, PAAG). The ACE CWT employs several modes of generating sprays, including a spray nozzle array suspended in its settling chamber and fed by heated pressurized de-ionized water to create supercooled droplets, a snow gun also located in the settling chamber, and a spray rig at the nozzle exit, to create a wide range of particle sizes from a few µm up to mm size range to create extreme Wx conditions. These set-ups, together with a range of cold Ta and RHw, plus a wide range of Uh, enabled simulation of severe Wx conditions, including icing, Vis, strong Uh and U’, ice fog and frost, freezing fog, heavy snow, and blizzard conditions. Overall, the results from the CWT simulations supported by the Ontario Tech University AViation MEteorological Supersite (AVMES) observations will be summarized for the aviation operations representing cold environments.</p>

ANALISIS DAN PERHITUNGAN PADA DAYA MOTOR UNTUK TEROWONGAN ANGIN (WIND TUNNEL) TIPE SUBSONIC DENGAN TEST SECTION 0,2 X 0,2 M UNTUK ALAT PERAGA MEKANIKA FLUIDA SKALA LABOLATORIUM

Aerodinamika yaitu salah satu bagian dari ilmu dinamika fluida yang mempelajari tentang gaya yang bekerja kepada suatu objek benda yang berada di dalam suatu aliran fluida. Pemecahan pada persoalan aerodinamika yang umumnya melibatkan penghitungan berbagai sifat pada aliran yang terjadi, semacam kecepatan, tekanan, temperatur, maupungaya masa jenis, sebagai suatu fungsi terhadap ruang dan waktu. Dengan mempelajari model - model aliran yang ada, maka akan memungkinkan untuk menghitung maupun memperkirakan momen dan gaya bekerja pada suatu objek yang berada pada aliran tersebut. Laporan secara eksperimen yang berguna dalam pemecahan permasalahan aerodinamika bisa didapat melalui berbagai macam metode, dan salah satu metode tersebut yaitu dengan menggunakan wind tunnel.Tujuan memperoleh angka air volume / CMH yang dibutuhkan pengujian pada (test section) di rangkaian terbuka wind tunnel. Mengetahui total keseluruhan kerugian pada tiap bagian rangkaian terbuka wind tunnel. Mengetahui dari hasil perhitungan daya motor pada fan yang benar dan sesuai.Dari perhitungan yang telah dilakukan maka nilai minimal air volume yang diperlukan pada bagian test section sebesar 2880,14 CMH (Cubic Meter Hour). Analisa dari perhitungan Energy losses (kerugian energi) dari setiap komponen dalam rangkaian terbuka wind tunnel yaitu settling chamber ( untuk nilai Honeycomb nilai K0 = 0,004687 dan screen nilai K1 = 0,004687) , contraction dengan nilai K2 = 0,02745, test section nilai K3 = 0,0675 , Diffuser nilai K4 = 0,72962, dan saluran discharge nilai K5 = 0,1667887. Maka total dari keseluruhan nilai tersebut dijumlahkan Ktotal = 0,20014656. Perhitungan nilai daya motor yang dibutuhkan pada hasil perhitungan pada BAB 4 sebesar 233,51 W -> ½ HP.

Analysis of Equivalence Ratio in an Oxygen Acetylene Mixture

The paper presents an exclusive approach to analyze the oxygen and acetylene mixture in a Pulse Detonation Engine setup at PEC. The experiment was carried out by varying the amount of mass flow of acetylene and oxygen into the tube at different pressures in the settling chamber. The equivalence ratio of the acetylene-oxygen mixture with respect to the valve opening time of acetylene and oxygen was plotted. The analysis of equivalence ratio also defines the procedure which involved the cycle of valves and pressure supply to attain different values of filling fraction of the tube. The results experimentally predicted the feasible range of operation at different pressures in the settling chamber of the pulse detonation engine.