A boiling bubble is created on an artificial site that is part of a bubble generator that is mounted at the center of a pipe. Downflow of water impinges on the bubble generator and creates a stagnation flow above the artificial cavity. Stable axisymmetric elongation in the direction away from the wall and multiple shape oscillation cycles are observed. The time of growth and attachment is typically of the order of 250 ms. Amongst the length scales that characterize the bubble shape is the radius of curvature of the upper part of the bubble, R. The period of oscillation, T, is strongly dependent on time, as is R. The parameters C and m in the defining equation T velence C R~(m) (((rho)_(L)/sigma))~(1/2) have been determined by fitting to data of more than 100 bubbles. For each operating condition, the same values of C and m have been found. The value of m is 1.49 +- 0.02, which is explained from the continuous growth of the bubble and from the relation to the period of oscillation of a free bubble deforming in the fundamental mode corresponding tot the 3th Legendre Polynomial. For the latter, R is the radius of the volume-equivalent sphere, R_(0), and C is (12)~(1/2), while for attached boiling bubbles C is found to amount 1.9(12)~(1/2). The difference is easily explained from the continuous growth, difference in definition, finite amplitude oscillation and proximity of the wall.
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