Abstract
A circular cylinder was tested in cross flow over the subsonic speed range. Timeresolved pressure distributions give information on surface pressure fluctuations and the corresponding drag and base drag coefficients are provided. The Strouhal number variation is compared with the measurements of other authors. Flow changes at higher subsonic velocities and into the transonic range are described. At Mach numbers above 0.6 the changing strength of the vortices reduces the base drag coefficient up to a Mach number of 0.9, where the onset of sonic flow increases the drag. Time-resolved base pressure fluctuations at low Mach numbers are in agreement with the findings of other researchers with regard to the relative time spent in vortex formation and shedding. As the Mach number increases the time spent in vortex formation becomes equal to that spent in shedding. The paper concentrates on providing detailed base pressure data rather than attempting to produce universal correlations. Physical explanations have been given, where possible, to assist toward a more general modeling of the problem.
Highlights
This paper reports on an experimental investigation of the base pressure variation over the subsonic speed range on a circular cylinder in cross flow
Turbine blades with a thick trailing edge, such as those investigated by Carscallen et al.3, have a high loss penalty associated with the trailing edge
The cross flow about a circular cylinder changes significantly at higher subsonic velocities and into the transonic range
Summary
This paper reports on an experimental investigation of the base pressure variation over the subsonic speed range on a circular cylinder in cross flow. In subsonic flows past a blunt trailing-edged turbine blade, or past its simplified model, a circular cylinder, periodic vortex shedding is almost always present up to a Mach number of about 1.2. This vortex shedding was found to be present in the wakes of blades with thick trailing edges, often associated with pressure waves propagating upstream along the blade surfaces when the local free stream flow was subsonic. Cicatelli and Sieverding conducted an investigation into the effect of vortex shedding on the base region flow They found that the pressure in this region fluctuated by as much as 8% of the downstream dynamic head near separation and by 4.8% in the base region. It has been concluded that, for bluff body flows, “calculation methods which neglect base pressure effects are incapable of accurately calculating the flow patterns or the total pressure loss”
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