Measurement of reference bubble velocity vector for a local 4- sensor probe using orthogonal high speed cameras

In recent years, there has been an increase in the level of interest shown in making flow rate measurements in multiphase flow. This in part has been brought about by the metering requirements of the oil and natural gas industries. Measuring the volumetric flow rate of each of the flowing components is often required and this is particularly true in production logging applications, where it may be necessary to measure the flow rates of oil and water down hole in vertical and inclined oil wells. Within the University of Huddersfield, work has been undertaken on the study of vertical and inclined multiphase flow. Previous work was based on the use of local, dual-sensor conductance probes to obtain the local axial velocity and volume fraction of the bubbles in multiphase flows. The purpose of this research presented in this paper is to investigate the accuracy with which a 4-sensor probe can measure bubble velocity vectors using two orthogonal high speed cameras. The probe was manufactured from 0.3mm diameter stainless steel acupuncture needles due to their high level of rigidity. The acupuncture needles were mounted inside a stainless steel tube with an outer diameter of 4mm. A procedure was carried out whereby where all the readings are taken simultaneously from both the cameras and 4-sensor probe. The camera and DAQ setting are made such they were controlled by an external trigger signal that is achieved thought the same circuit that is been used for the probe signal. The velocity vector of the top plane, centre of gravity (COG) and bottom plane of the bubbles were measured using the high speed cameras and compared with the bubble velocity vector obtained from the probe signal. In this paper bubble velocity vector is quantified in term of a polar angle α an azimuthal angle β and a velocity magnitude . v Nomenclature α Polar angle (degrees) β azimuthal angle (degrees) v Velocity magnitude (m/s) 11 t δ 22 t δ 33 t δ Time delays (s) calculated from the times at which the bubble surface contacts sensors 0, 1, 2 and 3 [3].