bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local-Correlation Based Zero-Equation Transition Model for Turbomachinery
Authors: Sandhu Jatinder Pal Singh 
Published: January 2020

Abstract
In this paper, we present a new local-correlation based zero-equation transition model. The new model, which is derived from the local-correlation based one-equation gamma transition model (Menter, F. R., Smirnov, P. E., Liu, T., and Avancha, R., A One-Equation Local Correlation-Based Transition Model, Flow, Turbulence and Combustion, vol. 95, 2015, pp. 583619.), does not require any additional equation to be solved, by defining a new variable, which captures the turbulent kinetic energy and intermittency collectively. The new model only adds three more source terms to the existing transport equation of turbulent kinetic energy. Hence the new model is straightforward to implement in already existing RANS solvers and reduces the computational memory requirement as compared to the other transition models. The transition prediction capability of the new model is tested and compared against the one-equation gamma transition model, especially for turbomachinery applications, where bypass transition is the primary transition mechanism, using a standard flat plate test case, and S809 airfoil. Preliminary results show that the new zero-equation transition model produces satisfactory results in terms of transition-location prediction.
Dynamic Behavior and Off-Design Performance Analysis of Solar Driven ORC Using Scroll Expanders
Authors: Zhang Ying , Narasimhan Arun Kumar , Bai Mengjie , Zhao Li , Deng Shuai , Goswami D. Yogi 
Published: January 2020

Abstract
Solar driven ORC system is a possible solution for small-scale power generation. A scroll expander is considered due to its better suitability among other positive displacement expanders for small-scale power outputs. This work conducted a test of an ORC system with an expansion valve by varying the working fluid mass flow rate in two scenarios. A dynamic system-level model of ORC was developed and validated with experimental data. The validated model was used to predict the ORC performance considering off-design conditions of expander and solar insolation. The experimental data showed that pressures and temperatures exhibited the same trend as that of the working fluid mass flow rate, of which the evaporation pressure was the most sensitive to this variation. The simulation results are in good agreement with the experimental results. Results from the dynamic model showed that the ORC power output was underestimated by up to 54.7%, when off-design performance of expander was not considered. Considering the expander off-design performance and solar insolation, a highest thermal efficiency of 7.6% and an expander isentropic efficiency of 80.6% were achieved.
Computational Study of Mist Assisted Film Cooling on a Flat Plate
Authors: Rao Pabbi Setty Mallikarjuna , Prasad B. V. S. S. S. 
Published: January 2020

Abstract
Previous investigation [1, 2] proposed that an introduction of water droplets into the film cooling air significantly improves the effectiveness of gas turbine blade. In order to allow comparison with experimental data, all the previous studies were confined to laboratory conditions. However, under typical gas turbine operating conditions temperature difference between the main stream flow (1561 K) and the coolant air (644 K) is approximately 917 K. The aim of this study is to numerically investigate the performance of mist assisted film cooling under the typical operating conditions of the gas turbine. Results showed the value of mist assisted film cooling effectiveness are greater than pure air cooling. Trajectories of droplets show that the water droplets vaporize faster. Typical percentage enhancement of the mist assisted film cooling effectiveness is 16% when the cooling air contains 6% mist with droplet diameter of one micron.
Experimental Investigation of Active Control of Cracked Rotor-Bearing System Equipped With Magnetic Bearing
Authors: Sarmah Nilakshi , Tiwari Rajiv 
Published: January 2020

Abstract
The present work investigates the online vibration control of a cracked rotor-bearing system incorporated with AMB. A fatigue crack, which exhibits the opening and closure behavior of cracked faces while rotation, is introduced artificially in the shaft to understand the dynamic behavior of a cracked rotor system. For this, three-point bending tests were performed to obtain edge transverse crack in the shaft. An eight-pole electromagnetic actuator was used to apply control forces directly on to the shaft in the radial direction. The radial force was used to assist vibration suppression in the rotor. In order to achieve active control to mechanical vibration and other disturbances, a simple PID control strategy is used. Closed loop tests are conducted on the d-SPACE DS1202 platform using the differential driving mode of the PID controller to suppress the vibration of a shaft containing a transverse crack integrated with an AMB supported on two conventional bearings. The comparison of the dynamic behavior of the laboratory test rig with and without active magnetic bearing (AMB) with the numerically simulated data is analyzed. The vibration suppression is found to be achieved satisfactorily in the presence of the unbalance force, bow force, crack force, and with other forces on the rotor-bearing system.
Effect of Tip Gap Variation on the Performance of the Transonic Fan Stage With Tandem Stator
Authors: Ananthakrishnan K. , Das Shyama Prasad , Prasad B. V. S. S. S. 
Published: January 2020

Abstract
The main goal of modern axial compressor development is to increase the power to weight ratio with higher efficiency. In the present investigation, highly loaded single stage axial compressor with tandem stator vanes is used. Tandem vanes help in attaining the compact compressor stage along with high pressure loading. It is designed for a stage pressure ratio of 2, mass flow rate of 9.02 kg/s operating at 30800 rpm resulting in transonic flow field. The aerodynamic performance of this compressor detoriates due to the tip leakage and secondary flows. Steady-state numerical investigation is carried out to study the flow structures near the tip region of transonic rotor and how different tip gaps influence the overall performance of the compressor. Further the effects of tip leakage flow variation on the performance of tandem vanes are also highlighted. Transonic fan stage with baseline tip gap of 0.5mm is analyzed along with different tip clearance values ranging from 0 % to 3 % of axial chord. Three-dimensional viscous Reynolds Averaged Navier Stokes (RANS) equations are solved using SST k-ω turbulence model. Computational domain discretized with high quality hexahedral elements (Y+ &lt; 2) in AUTOGRID, Numeca. The numerical procedure is verified against the experimental results of Rotor37 transonic rotor test case. Tip leakage losses contribute a substantial amount to the total loss of stage. Overall performance and the stall characteristics for the compressor stage has been evaluated for different tip gap variations.. Further, the topological properties are exploited to visualize the critical points and separation lines on rotor and tandem vanes. Increase in rotor total pressure loss coefficient is observed with increasing tip gap. In contrary, overall total pressure loss coefficient improves for smaller tip gap values and then detoriates. It is observed optimum tip gap height lies close to the 1.125mm, 2% of baseline design value.
Numerical Study of Part Clearance and Free Stream Turbulence on High End-Wall LP Turbine Nozzle Annular Cascade
Authors: Bhavsar Hardikkumar , Mistry Chetan S. 
Published: January 2020

Abstract
The performance of the gas turbine engines can be improved using variable area nozzle turbine (VANT) in the off-design condition by actively controlling the mass flow rate for various applications of engine. However, VANT demands part clearances to be provided near both the hub and tip of the vane for its mechanical movement. This clearance induces leakage flow and formation of the leakage vortex which interacts with the secondary flow in the vane passage. In this paper, the numerical study is performed on high endwall angle vane geometry of 2nd stage LPT from Pratt and Whitney E3 engine using commercially available CFD tool ANSYS CFX. The effect of free stream turbulence at 0.5%, 5% and 10% is studied along with the change of incidence angle from −10 to +10 on the annular cascade nozzle flow field. The static entropy contour, vorticity contour and total pressure loss coefficient are used to analyzed the flow. The free stream turbulence affects the structure of the vortices within the flow passage. However, no significant change on total pressure loss coefficient is present as turbulence intensity is changed from 0.5% to 5%, but total pressure loss coefficient increases as turbulence intensity is changed to 10%.
Comparative Study of Force Prediction Techniques Using Multi Component Accelerometer Force Balance for High Enthalpy Ground Testing
Authors: Kamal Abhishek , Das Gagan Chandra , Kulkarni Vinayak , Sahoo Niranjan 
Published: January 2020

Abstract
Large wave drag and high surface heating are the major concerns of hypersonic flows. Hence, development of force measurement technique or prediction of force has always remained a promising research topic in this field. Present studies also deal with force prediction techniques and force balance calibration methodology for ground testing in an impulse test facility. A blunt double cone model is fabricated along with a three component accelerometer force balance. Impulse hammer hits are made on different locations of this test model. In these calibration experiments, the applied impulse and acceleration responses from three accelerometers are recorded. These calibration tests are repeated multiple times to apply hammer hits of different magnitude. All the input and corresponding output singles are then processed first to arrive at the impulse response function or correlation between input and outputs. Then the force recovery techniques are applied to recover the axial and normal forces generated during application of one of the calibration forces. The experimentally recovered force signals from different techniques are compared and then the accuracy of these predictions is estimated using different error estimation techniques. Such studies are found essential not only in defining the most accurate force prediction technique but also in understanding the time required for prediction by a particular technique. Additionally, such studies essentially helps to improve a force prediction algorithm.
Experimental Analysis of Biogas Combustion With Different Foam Materials in a Porous Media Burner
Authors: Devi Sangjukta , Sahoo Niranjan , Muthukumar P. 
Published: January 2020

Abstract
The existing biogas Conventional Burners (CBs) are less energy efficient and are designed for rich fuel combustion. Porous Media Burner (PMB), working on the principle of combustion in porous media offer several advantages including high thermal efficiency, low emissions, high power intensity, etc. In this work, a study on the effect of porous material on the thermal behaviour of a biogas operated PMB is presented. A state-of-the-art PMB working in the thermal load range of 5 to 10 kW has been developed, which can be used for both industrial and domestic purposes. It is a two section burner composed of a combustion zone and a preheat zone. Keeping the material of the preheat zone unchanged (Al2O3 ceramic), the burner is tested with two different materials in the combustion zone (SiC and ZrO2 foams). Experimental investigation has been done to analyze the stability criteria and study the temperature distribution in the PMB. This includes the identification of the stable operating limits (flashback and blow off) and measurement of temperature profiles in axial and radial direction. These assessments confirm that SiC is a better choice over ZrO2 for lean biogas combustion in PMB.
Performance Improvement of a Combined Power and Cooling Cycle for Low Temperature Heat Sources Using Internal Heat Recovery and Scroll Expander
Authors: Leveni Martina , Narasimhan Arun Kumar , Almatrafi Eydhah , Goswami D. Yogi 
Published: January 2020

Abstract
Low temperature heat sources inherently result in lower cycle efficiencies, which can be improved by means of combined power and cooling generation. In order to produce power and cooling, appropriate thermodynamic cycles and working fluids must be used. Goswami cycle is a combined cycle that produces power and refrigeration by using ammonia-water mixture for low temperature heat sources. In the present study, a scroll expander is modeled specifically for the cycle operating conditions and a theoretical investigation is conducted to determine the cycle performance. A scroll expander design suitable for the operating conditions improves the power output and thereby overall thermal efficiency. The scroll expander efficiency varied between 0.05 and 0.61 for the pressure ratio between 2.2 and 8.6, with a maximum efficiency of 0.697 achieved at a pressure ratio of about 4.4. An internal heat recovery from the rectifier is proposed along with a flow split in the strong solution and analyzed for overall cycle energy efficiency improvement. Internal heat recovery from the rectifier increased the first law effective efficiency and the effective exergy efficiency by 7.9% and 7.8%, respectively, over the basic configuration.
RANS Based Iso-Thermal CFD Analysis of the Flow Field Created by a Radial Swirler in a Conical Nozzle
Authors: Rana Rampada , Kumar Sonu , Muthuveerappan Nagalingam 
Published: January 2020

Abstract
Improvement of specific fuel consumption and specific thrust of gas turbine engines have necessitated to have better combustion performances requirements in terms of combustion efficiency, flame stability, better ignition characteristics, lower emissions etc. Injector designs play a very pivotal role to meet the above requirements. In this paper steady state flow field studies have been carried out in a conical nozzle fitted with single swirler which is the fundamental part of a typical injector. The aspects of the flow field both inside and outside the injector have been captured by using RANS based calculations of commercial software Ansys Fluent. The computational domain extends from 500mm in the upstream direction and the exit flow of the nozzle is allowed to meet on to a domain of length more than 2000mm. The downstream domain is so chosen that the impact of the wall on to the evaluation of the flow field is found to be negligible resembling the flow field studies in open atmosphere. Realizable k-ε turbulent model and standard wall function were used with wall y+ extended from 30 onwards. The study shows a distinct feature of maximum flow velocity at the exit of the injector lip apart from the presence of regular re-circulation bubble at the exit of the injector.
Experimental Investigations on Meridional and Circumferential Stresses of Bellows due to Internal Pressure
Authors: Pagar Nitin D. , Gawande S. H. 
Published: January 2020

Abstract
Bellows Expansion joints are mostly linked with the piping connections of turbines, heat exchangers, process equipment’s etc. Its primary function is to absorb expansion and contraction in pipelines on which it is fixed and fulfill its functioning through peculiar springy shaped convolutions. At design stage, it is very difficult to guess fatigue life cycles due to evolved stresses in convolutions. When it is subjected to purely axial load, stress generation per convolution acting along longitudinal line is same; however the behavior is different under very small angular rotation and axial shift due to misalignments in structural mountings. To understand it, preliminary investigations on axial case is necessary and also to identify the location of various stresses in convoluted section. This work aims to determine the meridional and circumferential stresses on the convoluted shape when it is subjected to an axi-symmetric internal pressure loading. Experimentation is carried out to determine the maximum stresses and verified it with the help of numerical simulation and analytically. 10 convolution bellows is used for the experiments. It is observed that the meridional stresses are highly dominating the circumferential stresses along the same longitudinal line. Meridional membrane stresses and meridional bending stresses due to pressure are evaluated on two different locations, one on perfectly meridional line and another at the top surface of convolution along the same longitudinal line. The stresses found higher on the top surface of convolutions. Meridional membrane and bending stresses due to deflection are higher than the meridional membrane and bending stresses due to pressure. Evaluation of the maximum stresses is very helpful for the designers to develop the fatigue analysis model and exact prediction of the cycle life of the bellows.
No obvious impact of caesarean delivery on childhood allergic outcomes: findings from Australian cohorts
Authors: Liao Zijun , Lamb Karen E , Burgner David , Ranganathan Sarath , Miller Jessica E , Koplin Jennifer J , Dharmage Shyamali C , Lowe Adrian J , Ponsonby Anne-Louise , Tang Mimi L K , Allen Katrina J , Wake Melissa , Peters Rachel L 
Published: January 2020

Background and objectiveAs caesarean delivery and childhood allergy continue to rise, their inter-relationships may change. We examined whether caesarean delivery predicts allergic disease and impaired lung function in two contemporary harmonised population-based cohorts.MethodsParent-reported asthma and eczema data were drawn from two prospective Australian infant cohorts, HealthNuts (n=5276, born 2006–2010) and the Longitudinal Study of Australian Children (LSAC, n=5107, born 2003–2004) at age 6–7 years, and spirometric lung function from LSAC’s Child Health CheckPoint (n=1756) at age 11–12 years. Logistic regression estimated associations between delivery mode and current asthma and eczema at 6–7 years, and linear regression examined lung function at 11–12 years. Models were adjusted for potential confounding factors.ResultsComplete case analysis included 3135 HealthNuts and 3654 LSAC children (32.2% and 30.9% born by caesarean, respectively). An association was evident between caesarean delivery and asthma at age 6–7 years in HealthNuts (adjusted OR (aOR) 1.25, 95% CI 1.00 to 1.57) but not in LSAC (aOR 1.05, 95% CI 0.86 to 1.28), while neither study showed clear associations with eczema (HealthNuts: aOR 1.09, 95% CI 0.88 to 1.35; LSAC: aOR 0.89, 95% CI 0.69 to 1.15). Spirometric lung function parameters at age 11–12 years were similar by delivery mode. Associations were not modified by duration of breast feeding, maternal history of asthma/eczema, childcare attendance, number of older siblings or pet exposure.ConclusionsIn two unselected populations using harmonised protocols, the likely association of caesarean delivery with developing childhood allergy was small.
‘My hip is damaged’: a qualitative investigation of people seeking care for persistent hip pain
Authors: I R de Oliveira Beatriz , Smith Anne Julia , O'Sullivan Peter P B , Haebich Samantha , Fick Daniel , Khan Riaz , Bunzli Samantha 
Published: January 2020

ObjectivesClinicians who use the biopsychosocial approach to manage musculoskeletal pain disorders aim to understand how patients make sense of their symptoms. Treatment includes targeting the negative beliefs and coping responses that can lead to progressive pain and disability. We aimed to explore how people seeking care for persistent hip pain and disability make sense of their symptoms.MethodsCross-sectional qualitative study. People were eligible if they were aged ≥18 years, were consulting an orthopaedic surgeon for persistent hip pain and offered a non-surgical intervention. Data were collected through interviews that explored patients’ beliefs about the identity (diagnosis), causes, consequences, timeline and controllability of their symptoms, their strategies to cope with pain and their experiences in seeking healthcare. Transcribed interview data were analysed thematically using a framework approach.ResultsSixteen people (median age=51, range=33–73 years; median duration hip pain=3 years, range=3 months–20 years) participated. Most participants (10/16) believed their pain was caused by an exercise-related injury. Because of the results of imaging and interactions with healthcare professionals, all participants believed they had damaged hip structures. All described ineffective strategies to manage their pain and multiple failed treatments. For many (7/16), a lack of control over symptoms threatened their physical and mental health.ConclusionsThe way participants with persistent hip pain and disability made sense of their symptoms contributed to them avoiding physical activity, and it impaired their sleep, emotional well-being and physical health.
Addition of azathioprine to the switch of anti-TNF in patients with IBD in clinical relapse with undetectable anti-TNF trough levels and antidrug antibodies: a prospective randomised trial
Authors: Roblin Xavier , Williet Nicolas , Boschetti Gilles , Phelip Jean-Marc , Del Tedesco Emilie , Berger Anne-Emmanuelle , Vedrines Philippe , Duru Gerard , Peyrin-Biroulet Laurent , Nancey Stéphane , Flourie Bernard , Paul Stephane 
Published: January 2020

ObjectivesIn patients with IBD experiencing an immune-mediated loss of response (LOR) to antitumour necrosis factor (anti-TNF), algorithms recommend a switch of anti-TNF without immunosuppressive drug. The aim of our study was to compare in these patients two strategies: either switch to a second anti-TNF alone or with addition of azathioprine (AZA). After randomisation outcomes (time to clinical and pharmacokinetic failure) were compared between the two groups during a 2-year follow-up period.DesignConsecutive IBD patients in immune-mediated LOR to a first optimised anti-TNF given in monotherapy were randomised to receive either AZA or nothing with induction by a second anti-TNF in both arms. Clinical failure was defined for Crohn’s disease (CD) as a Harvey-Bradshaw index ≥5 associated with a faecal calprotectin level >250 µg/g stool and for UC as a Mayo score >5 with endoscopic subscore >1 or as the occurrence of adverse events requiring to stop treatment. Unfavourable pharmacokinetics of the second anti-TNF were defined by the appearance of undetectable trough levels of anti-TNF with high antibodies (drug-sensitive assay) or by that of antibodies (drug-tolerant assay).ResultsNinety patients (48 CDs) were included, and 45 of them received AZA after randomisation. The second anti-TNF was adalimumab or infliximab in 40 and 50 patients, respectively. Rates of clinical failure and occurrence of unfavourable pharmacokinetics were higher in monotherapy compared with combination therapy (p<0.001; median time of clinical failure since randomisation 18 vs >24 months). At 24 months, survival rates without clinical failure and without appearance of unfavourable pharmacokinetics were respectively 22 versus 77% and 22% versus 78% (p<0.001 for both) in monotherapy versus combination therapy. Only the use of combination therapy was associated with favourable outcomes after anti-TNF switch.ConclusionIn case of immune-mediated LOR to a first anti-TNF, AZA should be associated with the second anti-TNF.Trial registration number03580876.