Wall shear stress from single almost spherical and long Taylor bubbles in laminar upward tube flow

An experimental electrodiffusional technique with eight double probes is used to detect perturbation of the wall shear stress by a single bubble in laminar upward tube flow. Small almost spherical and long Taylor bubbles are tested. The wall shear stress perturbations by bubbles have a complex structure. It is possible to define three components of perturbation caused by a small bubble. The perturbation by Taylor bubble contains only two components due to the main flow symmetry around the bubble. An unexpectedly long shear stress pulsations zone is registered behind the Taylor bubbles.