Effect of probe geometry on flow patterns around cylindrical probes under quasi-isothermal conditions

Probe geometry in cooling curve analysis plays a significant role in the heat extraction history. In this work, we used cellophane ribbons attached to the probe tip to aid visualizing flow patterns around cylindrical probes at room temperature. The probes were placed within a plexiglass tube, with water flowing parallel to their longitudinal axis. Videos were recorded while water was flowing past the probe. The variables studied were probe geometry, free-stream velocity, and water temperature. Videos were analyzed, using the image analysis software Tracker, to determine the instantaneous position of the ribbons during one minute of recording.

Water temperature has a considerable effect on the behavior of the cellophane ribbon because its mechanical properties are temperature-dependent. An increment of the flow velocity intensifies the oscillation frequency of the ribbons. The conical-end and the hemispherical-end probes generate uniform streamlines around the tip while the flat-end probe distorts the flow pattern near the probe tip.