350,482 research outputs found

    Large probe arrays for measuring mean and time dependent local oil volume fraction and local oil velocity component distributions in inclined oil-in-water flows

    Get PDF
    Arrays of dual-sensor and four-sensor needle conductance probes have been used to measure the mean and time dependent local properties of upward inclined, bubbly oil-in-water flows (also known as dispersed oil-in-water flows) in a 153mm diameter pipe. The flow properties that were measured were (i) the local in-situ oil volume fraction ; (ii) the local oil velocity in the axial direction of the pipe (the direction); and (iii) the local oil velocity in the direction from the lower side of the inclined pipe to its upper side (the direction). Oil velocities in the direction (orthogonal to the and directions) were found to be negligible. For all of the flow conditions investigated it was found that the mean value of varied from a maximum value at the upper side of the inclined pipe to a minimum value at the lower side, and that the rate of decrease of this mean value of with distance in the direction became greater as the pipe inclination angle from the vertical was increased. It was also found that the mean value of was greatest at the upper side of the inclined pipe and decreased towards the lower side of the inclined pipe, the rate of decrease with distance in the direction again becoming greater as was increased. For , a water volumetric flow rate , an oil volumetric flow rate and using a sampling period over a total time interval of , it was found that at the upper side of the inclined pipe the standard deviation in was 31.6% of the mean value of . Furthermore for , , and it was found that the standard deviation in the cross-pipe oil velocity component was approximately equal to the standard deviation in the axial velocity component . These large temporal variations in the local flow properties have been attributed to the presence of large scale Kelvin-Helmholtz waves which intermittently appear in the flow. It is believed that the techniques outlined in this paper for measuring the standard deviation of local flow properties as a function of the sampling period will be of considerable value in validating mathematical models of time dependent oil-water flows. It should be noted that the principal focus of this paper is on the measurement techniques that were used and the methods of data analysis rather than the presentation of exhaustive experimental results at numerous different flow conditions

    Consistency check of {\Lambda}CDM phenomenology

    Full text link
    The standard model of cosmology LCDM assumes general relativity, flat space, and the presence of a positive cosmological constant. We relax these assumptions allowing spatial curvature, time-dependent effective dark energy equation of state, as well as modifications of the Poisson equation for the lensing potential, and modifications of the growth of linear matter density perturbations in alternate combinations. Using six parameters characterizing these relations, we check LCDM for consistency utilizing cosmic microwave background anisotropies, cross correlations thereof with high-redshift galaxies through the integrated Sachs-Wolfe effect, the Hubble constant, supernovae and baryon acoustic oscillation distances, as well as the relation between weak gravitational lensing and galaxy flows. In all scenarios, we find consistency of the concordance model at the 95% confidence level. However, we emphasize that constraining supplementary background parameters and parametrizations of the growth of large-scale structure separately may lead to a priori exclusion of viable departures from the concordance model.Comment: 15 pages, 14 figures, 4 tables; revision with minor change

    The End of the World and a Little Brown Dog

    Get PDF
    • …