Stotz, Stephan; Wakelam, Christian T.; Guendogdu, Yavuz; Niehuis, Reinhard
Document type:
Konferenzbeitrag / Conference Paper
Title:
Investigation of the Suction Side Boundary Layer Development on Low Pressure Turbine Airfoils with and without Separation using a Preston Probe
Title of conference publication:
Proceedings of ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Volume 2C: Turbomachinery
Subtitle of conference publication:
Düsseldorf, Germany, June 16–20, 2014
Conference title:
ASME Turbo Expo (2014, Düsseldorf)
Conference title:
Turbo Expo, Power for Land, Sea and Air 2014, Düsseldorf
Venue:
Düsseldorf
Year of conference:
2014
Date of conference beginning:
16.06.2014
Date of conference ending:
20.06.2014
Year:
2014
Pages from - to:
1-13
Language:
Englisch
Abstract:
Characterizing the transition process of airfoils can be very
challenging and requires often extensive measurement methods.
Frequently at low Reynolds numbers the suction side separation
often occurs close to the trailing edge so that asserting reattachment
of the flow to form a closed separation bubble from
the profile pressure distributions becomes uncertain. In the current
work the suction side transition process is investigated more
precisely with a convenient method to determine the dynamic
pressure close to the suction surface using a Preston probe (flattened
Pitot tube). Therefore four low pressure turbine airfoils,
which show different characteristics of the transition process
in the static pressure distribution have been investigated at the
High-Speed Cascade Wind Tunnel at the Universit¨at der Bundeswehr
M¨unchen at constant Mach number and under a wide
range of Reynolds numbers (40 000 to 400 000). It is shown
that this method is appropriate to determine transition start and
end as well as the separation and reattachment point of a separated
flow as long as the probe height is small enough compared
to the boundary layer thickness. The measurement results are
compared to profile pressure distributions and hot-wire boundary
layer profiles. Also the influence of periodic unsteady inflow
conditions on the dynamic pressure near the wall is revealed in
the time average. Limitations due to the probe geometry are discussed
and a method to estimate the influence of the probe geometry
on the measured dynamic pressure coefficient is suggested. «
Characterizing the transition process of airfoils can be very
challenging and requires often extensive measurement methods.
Frequently at low Reynolds numbers the suction side separation
often occurs close to the trailing edge so that asserting reattachment
of the flow to form a closed separation bubble from
the profile pressure distributions becomes uncertain. In the current
work the suction side transition process is investigated more
precisely with a convenient method to determi... »