Sensitivity analysis for a 4-sensor probe used for bubble velocity vector measurement
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 [1], 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 [1]. The 
purpose of this research presented in this paper is to investigate the sensitivity of 4-sensor-probes, 
used for bubble velocity vector measurement to dimensional measurement errors of the probe and to 
errors in measuring the time intervals between the surfaces of the bubble contacting the sensors in the 
probe. 
 
 
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 [2]. A procedure was carried out whereby an error on a specific probe 
dimension was introduced (errors in the range of -10 % to +10% of the true value of the dimension 
were used). The error in the measured bubble velocity vector was then investigated. A similar 
procedure was used to investigate the effect of measurement errors in the probe ‘time intervals’δt11 , 
22 δt and 33 δt on the measured bubble velocity vector. NB:The bubble velocity vector is quantified in 
terms of a polar angle α an azimuthal angle β and a velocity magnitude v . 
Results demonstrate that it is crucial to measure probe dimensions precisely (within the range of ±1%) 
as small errors in the probe dimensions or measured time intervals can give rise to large errors in the 
values ofα , β and v .
Power law approximations to gas volume fraction and velocity profiles in low void fraction vertical gas–liquid flows
Abstract A dual sensor conductance probe was used to measure the distributions of the local gas volume fraction and the local gas axial velocity in vertical upward, bubby air–water flows in which the mean gas volume fraction was less than 0.1. Very limited data are available in the literature for such low volume fraction flows. The measured local gas volume fraction and velocity distributions were approximated by power law functions. The power law exponents associated with the measured local gas volume fraction profiles were found to be up to 30% higher than values predicted in the literature. The power law exponents associated with the measured local gas velocity profiles were also found to be somewhat higher than values predicted in the literature. The power law exponents for the measured local gas volume fraction and local axial gas velocity distributions at a given flow condition were combined to obtain an estimate of the ‘Zuber–Findlay’ distribution parameter C 0 at that flow condition. The mean value of C 0 for all of the flow conditions investigated was 1.09. This value of C 0 was found to give good agreement with the gradient of a plot of the mean gas velocity u g versus the homogeneous velocity u h , where u g and u h were obtained from reference measurements. This agreement is evidence for the good accuracy of the measured volume fraction and velocity profiles. Finally, the paper casts doubt upon previously published criteria regarding the optimum axial sensor separation in dual sensor probes.
Economics of General-Purpose Assembly Robots
Summary A study of the comparative economics of various automatic assembly systems using general-purpose assembly robots is described. In the study, use is made of a “typical” candidate assembly whose profile is obtained from statistical analysis of actual products submitted by interested companies. It is shown that the choice of assembly system and the various parts presentation methods depends on three main factors, namely: the annual production volume per shift, the number of parts in the product and the equipment payback period.