Numerical simulation of three-phase flow in an external gear pump using immersed boundary approach

This paper presents a three-phase fully compressible model applied along with an immersed boundary model for predicting cavitation occurring in a two dimensional gear pump in the presence of non-condensable gas (NCG). Combination of these models is capable of overcoming numerical challenges such as modelling the contact between the gears and simulating the effect of NCG in cavitation. The model accounting for the effect of NCG also has broader applicability, since gas dissolved in liquids can come out of the solution when exposed to low pressures; this plays a significant role in the pump performance and cavitation erosion. Here the simulation results are presented for the gear pump at different operating conditions including the contact between gear, gear RPM and % of NCG; their effects on performance and cavitation is demonstrated. The results suggest that modelling the contact between the gears play a role in the cavitation prediction inside the gear pump. An increase in cavitation is observed when the contact is modelled even for the small pressure difference considered between the inlet and outlet. An increase in the RPM of the gears also results in increased cavitation within the pump, whereas an increase in the percentage of NCG content by a small amount can reduce the cavitation to a greater extent. This reduction is due to the expansion of the gas at a lower pressure which recovers the pressure and prevents or delays the phase-change process of the working fluid. The fluctuations in the outflow rate is also found to increase when the gears are in contact and also with increasing gas content

ACTINOMYCIN “D” FROM MARINE SEDIMENT ASSOCIATED STREPTOMYCES CAPILLISPIRALIS MTCC10471

In our screening program for new bio-active metabolites from marine actinomycetes, a cyclic depsipeptide wasfound in the fermentation medium of marine Strepromyces (SS23/4) isolated from sediments collected from Bayoff Bengal, vellampattai,Tamilnadu. It showed strong biological activity against gram-positive / gram negativebacteria by agar overlay technique. It was taxonomically characterized by the basis of morphological andphenotypic characteristics, genotypic data and phylogenetic showing Streptomyces sps. Bio active compoundwas obtained by solvent extraction and purification using column chromatography followed by reverse phaseHPLC. The pure compound had potent activity against Mycobacterium tuberculosis and Multi Drug ResistantMycobacterium tuberculosis strains (437RU) at a concentration of 10 μg/mL, and The minimum inhibitoryconcentration (MIC) against standard test organisms was found to be 1μg/mL against B.subtilis, E.coli andMethicillin resistant Staphylococcus aureus. The compound exhibited potent cytotoxic activity against breastcarcinoma (MCF-7), melanoma cells (A375), prostate carcinoma (DU145) and lung carcinoma (A549) cellswith IC values 20μg/ml. The symbiotic Streptomyces capillispiralis MTCC 10471 produces crude antibiotic30mg/Lt by using nonoptimized fermentation conditions. The structure of the antibiotic was explained by 1D,2D NMR and LC-ESI-MS/MS, MALDI-TOF/MS experiments, revealed that it belongs to cyclic ploy peptideActinomycin D

Numerical simulation of fuel dribbling and nozzle wall wetting

The present work describes a numerical methodology and its experimental validation of the flow development inside and outside of the orifices during a pilot injection, dwelt time and the subsequent start of injection cycle. The compressible Navier-Stokes equations are numerically solved in a six-hole injector imposing realistic conditions of the needle valve movement and considering in addition a time-dependent eccentric motion. The valve motion is simulated using the immersed boundary method; this allows for simulations to be performed at zero lift during the dwelt time between successive injections, where the needle remains closed. Moreover, the numerical model utilises a fully compressible two-phase (liquid, vapour) two-component (fuel, air) barotropic model. The air’s motion is simulated with an additional transport equation coupled with the VOF interface capturing method able to resolve the near-nozzle atomisation and the resulting impact of the injected liquid on the oleophilic nozzle wall surfaces. The eccentric needle motion is found to be responsible for the formation of strong swirling flows inside the orifices, which not only contributes to the breakup of the injected liquid jet into ligaments but also to their backwards motion towards the external wall surface of the injector. Model predictions suggest that such nozzle wall wetting phenomena are more pronounced during the closing period of the valve and the re-opening of the nozzle, due to the residual gases trapped inside the nozzle, and which contribute to the poor atomisation of the injected fluid upon re-opening of the needle valve in subsequent injection events

Bronchiectasis in India:results from the European Multicentre Bronchiectasis Audit and Research Collaboration (EMBARC) and Respiratory Research Network of India Registry

BACKGROUND: Bronchiectasis is a common but neglected chronic lung disease. Most epidemiological data are limited to cohorts from Europe and the USA, with few data from low-income and middle-income countries. We therefore aimed to describe the characteristics, severity of disease, microbiology, and treatment of patients with bronchiectasis in India. METHODS: The Indian bronchiectasis registry is a multicentre, prospective, observational cohort study. Adult patients ( 6518 years) with CT-confirmed bronchiectasis were enrolled from 31 centres across India. Patients with bronchiectasis due to cystic fibrosis or traction bronchiectasis associated with another respiratory disorder were excluded. Data were collected at baseline (recruitment) with follow-up visits taking place once per year. Comprehensive clinical data were collected through the European Multicentre Bronchiectasis Audit and Research Collaboration registry platform. Underlying aetiology of bronchiectasis, as well as treatment and risk factors for bronchiectasis were analysed in the Indian bronchiectasis registry. Comparisons of demographics were made with published European and US registries, and quality of care was benchmarked against the 2017 European Respiratory Society guidelines. FINDINGS: From June 1, 2015, to Sept 1, 2017, 2195 patients were enrolled. Marked differences were observed between India, Europe, and the USA. Patients in India were younger (median age 56 years [IQR 41-66] vs the European and US registries; p<0\ub70001]) and more likely to be men (1249 [56\ub79%] of 2195). Previous tuberculosis (780 [35\ub75%] of 2195) was the most frequent underlying cause of bronchiectasis and Pseudomonas aeruginosa was the most common organism in sputum culture (301 [13\ub77%]) in India. Risk factors for exacerbations included being of the male sex (adjusted incidence rate ratio 1\ub717, 95% CI 1\ub703-1\ub732; p=0\ub7015), P aeruginosa infection (1\ub729, 1\ub710-1\ub750; p=0\ub7001), a history of pulmonary tuberculosis (1\ub720, 1\ub707-1\ub734; p=0\ub7002), modified Medical Research Council Dyspnoea score (1\ub732, 1\ub725-1\ub739; p<0\ub70001), daily sputum production (1\ub716, 1\ub703-1\ub730; p=0\ub7013), and radiological severity of disease (1\ub703, 1\ub701-1\ub704; p<0\ub70001). Low adherence to guideline-recommended care was observed; only 388 patients were tested for allergic bronchopulmonary aspergillosis and 82 patients had been tested for immunoglobulins. INTERPRETATION: Patients with bronchiectasis in India have more severe disease and have distinct characteristics from those reported in other countries. This study provides a benchmark to improve quality of care for patients with bronchiectasis in India. FUNDING: EU/European Federation of Pharmaceutical Industries and Associations Innovative Medicines Initiative inhaled Antibiotics in Bronchiectasis and Cystic Fibrosis Consortium, European Respiratory Society, and the British Lung Foundation

Numerical simulation of cavitation in the presence of non-condensable gas using a three-phase model

The interactions between liquid, vapour and gas (three phases) play a vital role in determining the efficiency of many engineering equipments. To study these interactions, a three phase model is developed using barotropic equations of state and implemented into the Navier-Stokes equations; the barotropic fluid is assumed to be in thermal and mechanical equilibrium with the air. The air's motion is simulated using two different approaches, a sharp interface capturing VOF technique and a diffused interface mixture model. Alongside the so-called three-phase model, an immersed boundary method (IBM) is also developed for modelling the complex geometry motions. Both these models are implemented into the Ansys Fluent solver using User Defined Functions (UDF's) and are validated against relevant experimental studies. Several three-phase flow simulations have been performed, starting from simplified 2D simulations and moving to more complex industrial applications, such as Diesel injectors and gear pumps. Firstly, the three-phase model using the sharp interface VOF approach, in conjunction with the LES model for resolving turbulence, is used for studying the influence of in-nozzle flow on primary atomisation from an asymmetric step-nozzle. The results obtained from the simulation show a good correlation with the experimental observations. The transient flow phenomena occurring during the opening, closing and dwelt time in fuel injectors are known to significantly contribute to excess exhaust emissions in engines. The three-phase model using the VOF approach with a model for wall-adhesion is used for predicting the flow development inside and outside of the orifices and the wall wetting during the start, end, dwelt time and the subsequent start of the injection cycle. The simulations are performed and validated in a six-hole VCO-type injector imposing realistic conditions of the valve movement, implemented using the immersed boundary method; this allows for simulations to be performed at zero lift during the dwelt time between successive injections. The three-phase model using the mixture approach in conjunction with the IBM model is further used for simulating the effect of varying gas content in the fluid on cavitation occurring from an external gear pump. These simulations have revealed the importance of modelling contact between the gears in predicting the pump performance accurately. Moreover, it was observed that the main effect of increasing the NCG content in the fluid is a reduction in cavitation occurring inside the pump