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EXPERIMENTAL INVESTIGATION OF JETS PRODUCED BY ROTATING FULLY DEVELOPED PIPE FLOW

Luca Facciolo
Linne Flow Centre, KTH Mechanics, Royal Institute of Technology, S-100 44 Stockholm, Sweden

Nils Tillmark
KTH Mechanics, SE-100 44 Stockholm, Sweden

Alessandro Talamelli
II Facoltà di Ingegneria, Università di Bologna, Via Fontanelle 40, Forl`ı, 47100, Italy

Résumé

The flow field of a turbulent jet emerging from a rotating pipe has been experimentally studied for three Reynolds numbers and for different swirl values. The investigation of the mean and fluctuating axial and azimuthal velocity profiles, performed with Laser Doppler Velocimetry, includes the near exit and the transitional jet region. The data, together with the axial decay and turbulence intensity along the centreline, show the large effects of the swirl number on the flow field development. Relatively small effects are observed to be caused by variations in the Reynolds number. The entrainment results are strongly affected by the swirl and by the Reynolds number due to changes in the vortical structures. Spectra, obtained by means of hot wire anemometry, show that the swirl number does not affect the characteristic frequencies measured at the jet axis.