Air Flow Visualizaton Using Titanium Tetrachloride

Freymuth, P.

doi:10.1007/978-3-642-83787-6_1

Cited by 2 publications

(2 citation statements)

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“…On comparing these flow-visualization pictures with the r.m.s. boundary-layer profiles of case 1, similar conclusions are found to those of Freymuth (1989). Freymuth investigated the growth of small disturbances in an excited jet by hot-wire measurements and flow visualization.…”

Section: Flow Visualizationsupporting

confidence: 76%

“…The LDA yielded some important results throughout the investigation, but it was still unclear exactly how the flow behaved as it passed over the trailing edge and into the wake using. Therefore, smoke streakline flow visualization was performed to observe the flow structure at the aerofoil trailing edge and into the wake using titanium tetrachloride (Freymuth 1989). A few drops of TiCl 4 were introduced by pipette onto the surface of the aerofoil at approximately 70 % chord, which was upstream of separation, but close enough to maintain a dense filament of smoke over the trailing edge.…”

Section: Flow Visualizationmentioning

confidence: 99%

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Boundary-layer instability noise on aerofoils

1999

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An experimental and theoretical investigation has been carried out to understand the tonal noise generation mechanism on aerofoils at moderate Reynolds number. Experiments were conducted on a NACA0012 aerofoil section in a low-turbulence closed working section wind tunnel. Narrow band acoustic tones were observed up to 40 dB above background noise. The ladder structure of these tones was eliminated by modifying the tunnel to approximate to anechoic conditions. High-resolution flow velocity measurements have been made with a three-component laser-Doppler anemometer (LDA) which have revealed the presence of strongly amplified boundary-layer instabilities in a region of separated shear flow just upstream of the pressure surface trailing edge, which match the frequency of the acoustic tones. Flow visualization experiments have shown these instabilities to roll up to form a regular Kármán-type vortex street.A new mechanism for tonal noise generation has been proposed, based on the growth of Tollmien-Schlichting (T-S) instability waves strongly amplified by inflectional profiles in the separating laminar shear layer on the pressure surface of the aerofoil. The growth of fixed frequency, spatially growing boundary-layer instability waves propagating over the aerofoil pressure surface has been calculated using experimentally obtained boundary-layer characteristics. The effect of boundary-layer separation has been incorporated into the model. Frequency selection and prediction of T-S waves are in remarkably good agreement with experimental data.

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Section: Flow Visualizationsupporting

confidence: 76%

Section: Flow Visualizationmentioning

confidence: 99%