Testing of a spherical dual‐tipped optical fiber probe for local measurements of void fraction and gas velocity in two‐phase flows

Abstract

AbstractAn alternate and easy method of constructing an optical liber probe tip is presented for the study of different two‐phase flow variables such as local time‐averaged void fraction, gas velocity and interfacial bubble passage frequency. The proposed probe tip has similar response characteristics to the “U‐bend” single fiber probe and is easier to construct than the 90° wedge tipped probe. The signal from the spherical tip seems to be insensitive to changes in bubble velocity as opposed to the 90° wedge and is more advantageous at higher velocities. The signal from the spherical tip has the same time duration as the signal changes from liquid to gas and vice versa for the same bubble velocity. A simplified model is presented to describe the balance of forces around the spherical tip when a bubble is penetrated. The model offers a qualitative explanation of why the non‐dimensional response intensity decreases as the bubble velocity increases.