Non-boiling heat transfer in horizontal and near horizontal downward inclined gas-liquid two phase flow

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Heat transfer in non-boiling gas-liquid two phase flow has significant practical applications in chemical and petroleum industry. To date, majority of the research in this field have been conducted for two phase flow in horizontal and vertical pipe systems. To explore and enhance the general understanding of heat transfer in non-boiling two phase flow, the main focus of this work is to experimentally measure local and average convective heat transfer coefficients for different flow patterns in horizontal and near horizontal downward inclined two phase flow. In total, 380 experiments are carried out in a 12.5 mm I.D. schedule 10S stainless steel pipe at 0, -5, -10 and -20 degrees pipe orientations using air-water as fluid combination. For each pipe orientation, the superficial gas and liquid Reynolds number is varied from 200 to 19,000 and 2000 to 18,000, respectively. The measured values of the average two phase heat transfer coefficient are found to be in a range of 500 W/m2K to 7700 W/m2K. Comparisons are drawn between the two phase heat transfer coefficients in the above mentioned pipe orientations. It is found that the increase in inclination of the pipe in downward direction causes the two phase heat transfer coefficient to decrease. This trend of two phase heat transfer data is explained based on the flow visualization and establishing its connection with the flow pattern structure and the two phase flow physics.cf201

Non-boiling heat transfer in horizontal and near horizontal upward inclined gas-liquid two phase flow

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Heat transfer in non-boiling gas-liquid two phase flow finds its practical application in chemical and petroleum industries. So far, majority of the research dedicated to study heat transfer in non-boiling two phase flow is limited to horizontal and vertical pipe orientations with very little attention given to the study of this phenomenon in inclined systems. To contribute and further enhance the general understanding of heat transfer in non-boiling two phase flow, the main focus of this work is to experimentally measure local and average convective heat transfer coefficients for different flow patterns in horizontal and near horizontal upward inclined two phase flow. In total, 368 experiments are carried out in a 12.5 mm I.D. schedule 10S stainless steel pipe at 0, +5, +10 and +20 degrees pipe orientations using air-water as fluid combination. For each pipe orientation, the superficial gas and liquid Reynolds number is varied from 200 to 19,000 and 2000 to 18,000, respectively and the measured values of the averaged heat transfer coefficient were found to be in a range of 1300 W/m2K to 8000 W/m2K. The two phase heat transfer coefficients are compared among the above mentioned orientations. It is found that the two phase heat transfer coefficient increases from 0o to +5o and +10o degree and then decreases at +20 degree.cf201

Manifestation of three-body forces in three-body Bethe-Salpeter and light-front equations

Bethe-Salpeter and light-front bound state equations for three scalar particles interacting by scalar exchange-bosons are solved in ladder truncation. In contrast to two-body systems, the three-body binding energies obtained in these two approaches differ significantly from each other: the ladder kernel in light-front dynamics underbinds by approximately a factor of two compared to the ladder Bethe-Salpeter equation. By taking into account three-body forces in the light-front approach, generated by two exchange-bosons in flight, we find that most of this difference disappears; for small exchange masses, the obtained binding energies coincide with each other.Comment: 24 pages, 8 figures, submitted in Few-Body System

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Effect of pipe surface roughness on frictional pressure drop in gas-liquid two phase flows

The main objective of this experimental work is to investigate the effect of pipe surface roughness on frictional component of gas-liquid two phase pressure drop. The pressure drop measurements are carried out with air-water two phase flow in two different flow loops. First flow loop consists of 12.7 mm I.D. (smooth pipe), 12.5 mm (rough pipe) while second flow loop consists of both smooth and rough pipes of 27.8 mm I.D. The smooth and rough pipes are made up of polycarbonate and stainless steel material, respectively. Thus, all experiments are carried out for four different combinations of relative roughness. The gas and liquid flow rates are varied systematically so as to generate all key flow patterns observed in two phase flow. Experimental results show that the increase in the relative roughness increases the frictional pressure drop as a function of both gas and liquid flow rates. This effect is substantial for inertia driven flows (annular flow) compared to bubbly and slug flow patterns. It is also seen that the effect of increase in relative roughness on the frictional pressure drop increases with decrease in the pipe diameter. Moreover, the measurements carried out in 12.7 mm and 12.5 mm I.D. pipes at upward and downward inclinations show that the effect of relative roughness on frictional pressure drop is independent of the pipe inclination. The general trends of frictional pressure drop for different relative roughness are found to be in agreement with the experimental observations reported in literature. Evaluation of the existing two phase flow models developed for smooth pipes show that these correlations under predict the frictional pressure drop in rough pipes.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Evaluation of clinical skills for first-year surgical residents using orientation programme and objective structured clinical evaluation as a tool of assessment

Background: Postgraduate specialities require a combination of knowledge and clinical skills. The internship year is less structured. Clinical and practical skills that are picked up during training are not well regulated and the impact is not assessed. In this study, we assessed knowledge and skills using objective structured clinical examination (OSCE). Aim: To evaluate the clinical skills of new first-year surgical residents using orientation programme and OSCE as a tool for assessment. Settings and Design: Observational study. Materials and Methods: Twenty new first-year surgical residents (10 each in 2008 and 2009) participated in a detailed structured orientation programme conducted over a period of 7 days. Clinically important topics and skills expected at this level (e.g., suturing, wound care etc.) were covered. The programme was preceded by an OSCE to test pre-programme knowledge (the "pre-test"). The questions were validated by senior department staff. A post-programme OSCE (the "post-test") helped to evaluate the change in clinical skill level brought about by the orientation programme. Statistical Analysis: Wilcoxson matched-pairs signed-ranks test. Results: Passing performance was achieved by all participants in both pre- and post-tests. Following the orientation programme, significant improvement was seen in tasks testing the psychomotor and cognitive domains. (P = 0.0001 and P = 0.0401, respectively). Overall reliability of the OSCE was found to be 0.7026 (Cronbach′s coefficient alpha). Conclusions: This study highlighted the lacunae in current internship training, especially for skill-based tasks. There is a need for universal inclusion of structured orientation programmes in the training of first-year residents. OSCE is a reliable, valid and effective method for the assessment of clinical skills