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1 – 10 of 95Sathish Kumar K, Naren Shankar R, Anusindhiya K and Senthil Kumar B.R.
This study aims to present the numerical study on supersonic jet mixing characteristics of the co-flow jet by varying lip thickness (LT). The LT chosen for the study is 2 mm, 7.75…
Abstract
Purpose
This study aims to present the numerical study on supersonic jet mixing characteristics of the co-flow jet by varying lip thickness (LT). The LT chosen for the study is 2 mm, 7.75 mm and 15 mm.
Design/methodology/approach
The primary nozzle is designed for delivering Mach 2.0 jet, whereas the secondary nozzle is designed for delivering Mach 1.6 jet. The Nozzle pressure ratio chosen for the study is 3 and 5. To study the mixing characteristics of the co-flow jet, total pressure and Mach number measurements were taken along and normal to the jet axis. To validate the numerical results, the numerical total pressure values were also compared with the experimental result and it is proven to have a good agreement.
Findings
The results exhibit that, the 2 mm lip is shear dominant. The 7.75 mm and 15 mm lip is wake dominant. The jet interaction along the jet axis was also studied using the contours of total pressure, Mach number, turbulent kinetic energy and density gradient. The radial Mach number contours at the various axial location of the jet was also studied.
Practical implications
The effect of varying LT in exhaust nozzle plays a vital role in supersonic turbofan aircraft.
Originality/value
Supersonic co-flowing jet mixing effectiveness by varying the LT between the primary supersonic nozzle and the secondary supersonic nozzle has not been analyzed in the past.
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Ezhilmaran G., Sekar S., Sathish Kumar K. and Thanigaiarasu S.
This study aims to investigate the effect of slanted perforation diameter in tabs for the control of Mach 1.4 underexpanded supersonic jet flow characteristics.
Abstract
Purpose
This study aims to investigate the effect of slanted perforation diameter in tabs for the control of Mach 1.4 underexpanded supersonic jet flow characteristics.
Design/methodology/approach
Numerical investigation was carried out for NPR 5 to analyze the effect of slanted perforation diameter in tabs to control the Mach 1.4 jet. Four sets of tabs with slanted circular perforation geometries (Φp = 1, 1.5, 2 and 2.5 mm) were considered in this study. The inclination angle of 20° (αP) with reference to the jet axis was maintained constant for all the four tabs considered.
Findings
Determined value indicates there is a 68%, 71%, 73% and 75% drop in supersonic core for the Φp = 1, 1.5, 2.0 and 2.5 mm, respectively. The results show that the tabs with 2.5 mm perforation diameter were found to be efficient in reducing the supersonic jet core in comparison with other tab cases. The reduction in supersonic core length is due to the extent of miniscule vortices exuviating from slanted small and large diameter perforation in the tabs.
Practical implications
The concept of slanted perforation can be applied in scramjet combustion, which finds its best application in hypersonic vehicles and in noise suppression in fighter aircraft.
Originality/value
Slanted perforation and circular shapes with different diameters have not been studied in the supersonic regime. Examining the effect of circular diameter in slanted perforation is an innovation in this research paper.
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Naren Shankar R., Kevin Bennett S., Dilip Raja N. and Sathish Kumar K.
This study aims to analyze co-flowing jets (CFJs) with constant velocity ratio (VR) and varying primary nozzle lip thickness (LT) to find a critical LT in CFJs below which mixing…
Abstract
Purpose
This study aims to analyze co-flowing jets (CFJs) with constant velocity ratio (VR) and varying primary nozzle lip thickness (LT) to find a critical LT in CFJs below which mixing enhances and beyond which mixing inhibits.
Design/methodology/approach
CFJs were characterized with a constant VR and varying LTs. A single free jet with a diameter equal to that of a primary nozzle of the CFJ was used for characteristic comparison. Numerical simulation is carried out and is validated with the experimental results.
Findings
The results show that within a critical limit, the mixing enhanced with an increase in LT. This was signified by a reduction in potential core length (PCL). Beyond this limit, mixing inhibited leading to the elongation of PCL. This limit was controlled by parameters such as LT and constant VR. A new region termed as influential wake zone is identified.
Practical implications
In this study, the VR is maintained constant and bypass ratio (BR) was varied from low value to very high values. Presently, subsonic commercial turbo fan operates under low to ultra-high BR. Hence the present study becomes vital to the current scenario.
Originality/value
To the best of the authors’ knowledge, this is the first effort to find the critical value of LT for a constant VR for compressible co-flow jets. The CFJs with constant VR and varying LT have not been studied in the past. The present study focuses on finding a critical LT below which mixing enhances and above which mixing inhibits.
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Sathish Kumar K. and Senthilkumar Chidambaram
The purpose of this study is to increase the jet mixing effectiveness of Mach 1.6 axisymmetric jet using semi-circular corrugated triangular tabs (Tabs A, B and C), in which the…
Abstract
Purpose
The purpose of this study is to increase the jet mixing effectiveness of Mach 1.6 axisymmetric jet using semi-circular corrugated triangular tabs (Tabs A, B and C), in which the locations of the semi-circular corrugations are varied along the leaned sides of the triangular tabs.
Design/methodology/approach
The tabs are fixed at the exit of the nozzle facing each other 180° apart. To quantify the jet mixing effectiveness of the semi-circular corrugated tabs, Pitot pressure measurements were carried out for the cases of over-expansion, marginally over-expansion and under-expansion levels of Mach 1.6 jet, along the jet centerline and the jet spread, along and normal to the tab axis.
Findings
The results exhibit that the semi-circular corrugated Tab A augments the jet mixing when compared to Tabs B and C. This impact in jet mixing is strongly due to the small-scale vortices shed from the tabs and the mixed effect of the corrugation locations and expansion ratio. The maximum percentage reduction in core length is about 73.6 per cent for the jet with semi-circular corrugated Tab A at NPR 5, whereas it is 71.4 and 67.1 per cent for Tabs B and C, respectively.
Practical implications
The reduction in core length of the jet with minimum thrust loss is obtained by controlling the jet used with semi-circular corrugated triangular tabs of equal blockage ratio 5.12 per cent with respect to the nozzle exit diameter.
Originality/value
The locations of the semi-circular corrugations varied systematically at the equally leaned sides of the triangular tab ensure the novelty of this study.
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Sathish Kumar K., Senthilkumar Chidambaram and Naren Shankar Radha Krishnan
This paper aims to present the jet mixing effectiveness of triangular tabs with semi-circular corrugations to control the subsonic and sonic correctly expanded jets.
Abstract
Purpose
This paper aims to present the jet mixing effectiveness of triangular tabs with semi-circular corrugations to control the subsonic and sonic correctly expanded jets.
Design/methodology/approach
Three semi-circular corrugated triangular tabs (Tab A, Tab B and Tab C) of equal blockage 5.11% are used, in which the corrugation locations on the tabs are varied. The offset distance between the semi-circular corrugations at the leaned edges of the triangular tabs are 0.0, 0.75 and 1.5 mm for the Tabs A, B and C, respectively. Two identical semi-circular corrugated tabs has been placed exactly 180° apart at the exit of the convergent nozzle. The pitot pressure measurements were taken to study the jet mixing characteristics of the tabs for the jet exit Mach numbers of 0.6, 0.8 and 1.0, and it is compared with the free jet.
Findings
The jet centerline pitot pressure decay reveals that, Tab A is very effective than Tab B and Tab C. For the jet exit Mach numbers of 0.6, 0.8 and 1.0, the potential core reduction for the Tab A is found to be 69.1%, 69.7% and 70.8%, respectively, when compared with the free jet.
Practical implications
The semi-circular corrugated triangular tabs were found to be more effective than the plain triangular tabs of equal blockage ratio for reducing the core length with minimum thrust loss.
Originality/value
The offset distance of the semi-circular corrugations are varied along the leaned sides of the triangular tabs, which is the novelty of this study.
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Naren Shankar Radha Krishnan, Irish Angelin S., Ganesan V.G. and Sathish Kumar K.
In comparison to a nozzle with a larger/finite separation distance (Thanigaiarasu et al., 2019), a thin-lip nozzle (Srinivasarao et al., 2017) minimizes drag. Coaxial nozzles with…
Abstract
Purpose
In comparison to a nozzle with a larger/finite separation distance (Thanigaiarasu et al., 2019), a thin-lip nozzle (Srinivasarao et al., 2017) minimizes drag. Coaxial nozzles with thin lips are an appropriate tool for studying high subsonic jets because it does not create a dominant re-circulation zone. This study aims to analyze the characteristic of separation distances, between primary and secondary nozzles, within the range of 0.7–3.2 mm which can be considered a thin lip.
Design/methodology/approach
A separation distance of 0.7 (Papamoschou, 2004), 1.7 and 2.65 mm (Lovaraju and Rathakrishnan, 2011) is considered for the present study. The main nozzle exit Mach number is maintained at a subsonic condition of Mach 0.6, and the co-flowing nozzle exit Mach number is varied from 0% (secondary jet stopped/single jet) to 100% (Mach 0.6) in steps of 20% with respect to the main nozzle exit Mach number. A comparison was made between these velocity ratios for all three lip thicknesses in the present study. Design mesh and analysis were done by using Gambit 2.6.4 and Fluent 6.12. Velocity contours and turbulence contours were studied for qualitative analysis.
Findings
When lip thickness increases from 0.7 to 2.65 mm, the potential core length (PCL) of the primary jet decreases marginally. Additionally, the PCL of the primary jet elongates significantly as the velocity ratio increases. The primary shear layer is dominant at 20% co-flow (20 PCF), less dominant at 60% co-flow (60 PCF) and almost disappeared at 100% co-flow (100 PCF). Concurrently, the secondary shear layer almost disappeared in 20 PCF, dominant in 60 PCF and more dominant in 100 PCF. Different zones such as initial merging, intermediate and fully merged zones are quantitatively and qualitatively analyzed.
Practical implications
Co-flow nozzle is used in turbofan engine exhaust. The scaled-down model of a turbofan engine has been analyzed. Core length is directly proportional to the jet noise. The PCL signifies the jet noise reduction in a high-speed jet. For a low-velocity ratio, the potential core is reduced and hence can reduce the jet noise. At the same time, as the velocity ratio increases, the mass flow rate of the coaxial increases. The increase in the mass flow increases the thrust of the engine. The aircraft engine designer should analyze the requirement of the aircraft and choose the optimal velocity ratio coaxial nozzle for the engine exhaust (Papamoschou, 2004).
Originality/value
There have been many research studies carried out previously at various lip thickness such as 0.4 (Georgiadis, 2003), 0.7 (Papamoschou, 2004), 1.5 (Srinivasarao et al., 2014a), 1.7 (Sharma et al., 2008), 2 (Naren, Thanigaiarasu and Rathakrishnan, 2016), 2.65 (Lovaraju and Rathakrishnan, 2011), 3 (Inturiet al., 2022) and 3.2 mm (Perumal et al., 2020). However, there is no proper study to vary the lip thickness in this range from 0.7 to 3.2 mm to understand the flow behavior of a co-flowing jet.
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Naren Shankar R., Ganesan V.G., Dilip Raja N., Sathish Kumar K. and Vijayaraja K.
The effect of increasing lip thickness (LT) and Mach number on subsonic co-flowing Jet (CFJ) decay at subsonic and correctly expanded sonic Mach numbers has been analysed…
Abstract
Purpose
The effect of increasing lip thickness (LT) and Mach number on subsonic co-flowing Jet (CFJ) decay at subsonic and correctly expanded sonic Mach numbers has been analysed experimentally and numerically in this study. This study aims to a critical LT below which mixing enhances and above which mixing inhibits.
Design/methodology/approach
LT is the distance, separating the primary nozzle and the secondary duct, present in the co-flowing nozzle. The CFJ with LT ranging from 2 mm to 150 mm at jet exit Mach numbers of 0.6, 0.8 and 1.0 were studied in detail. The CFJ with 2 mm LT is used for comparison. Centreline total pressure decay, centreline static pressure decay and near field flow behaviour were analysed.
Findings
The result shows that the mixing enhances until a critical limit and a further increase in the LT does not show any variation in the jet mixing. Beyond this critical limit, the secondary jet has a detrimental effect on the primary jet, which deteriorates the process of mixing. The CFJ within the critical limit experiences a significantly higher mixing. The effect of the increase in the Mach number has marginal variation in the total pressure and significant variation in static pressure along the jet axis.
Practical implications
In this study, the velocity ratio (VR) is maintained constant and the bypass ratio (BR) was varied from low value to very high values for subsonic and correctly expanded sonic. Presently, commercial aircraft engine operates under these Mach numbers and low to ultra-high BR. Hence, the present study becomes essential.
Originality/value
This is the first effort to find the critical value of LT for a constant VR for a Mach number range of 0.6 to 1.0, compressible CFJ. The CFJs with constant VR of unity and varying LT, in these Mach number range, have not been studied in the past.
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Vishal Vyas and Sonika Raitani
The price war and intense competition in Indian banking industry have exposed banks to one of the major threat of switching. Consumers are now more price and service conscious in…
Abstract
Purpose
The price war and intense competition in Indian banking industry have exposed banks to one of the major threat of switching. Consumers are now more price and service conscious in their financial services purchasing behaviour. They are more prone to change their banking behaviour as banking products and services are nearly identical in nature. The purpose of this paper is to provide an insight of the drivers that lead a customer switch from one service provider to another in Indian banking industry using exploratory design.
Design/methodology/approach
The impacts of the influencing factors have been studied and tested empirically using exploratory factor analysis. Quantitative data have been collected by means of questionnaire employed from Clemes et al. and administered to 296 banking customers of Rajasthan utilizing convenience sampling.
Findings
Results reported that price, reputation, responses to service failure, customer satisfaction, service quality, service products, competition, customer commitment and involuntary switching have their significant effect on customers’ switching behaviour.
Research limitations/implications
The findings of present study can be used by the Indian banks for their product and service designing strategies, marketing strategies and customer services practices in order to reduce customer switching. It would help them in improving their service operations and also in increasing customer satisfaction and loyalty by understanding the banking behaviour of their customers.
Originality/value
The originality lies in the fact that this study is one of few which have focused on the drivers leading to the switching intentions of Indian banking customers.
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Usman Tariq, Ranjit Joy, Sung-Heng Wu, Muhammad Arif Mahmood, Asad Waqar Malik and Frank Liou
This study aims to discuss the state-of-the-art digital factory (DF) development combining digital twins (DTs), sensing devices, laser additive manufacturing (LAM) and subtractive…
Abstract
Purpose
This study aims to discuss the state-of-the-art digital factory (DF) development combining digital twins (DTs), sensing devices, laser additive manufacturing (LAM) and subtractive manufacturing (SM) processes. The current shortcomings and outlook of the DF also have been highlighted. A DF is a state-of-the-art manufacturing facility that uses innovative technologies, including automation, artificial intelligence (AI), the Internet of Things, additive manufacturing (AM), SM, hybrid manufacturing (HM), sensors for real-time feedback and control, and a DT, to streamline and improve manufacturing operations.
Design/methodology/approach
This study presents a novel perspective on DF development using laser-based AM, SM, sensors and DTs. Recent developments in laser-based AM, SM, sensors and DTs have been compiled. This study has been developed using systematic reviews and meta-analyses (PRISMA) guidelines, discussing literature on the DTs for laser-based AM, particularly laser powder bed fusion and direct energy deposition, in-situ monitoring and control equipment, SM and HM. The principal goal of this study is to highlight the aspects of DF and its development using existing techniques.
Findings
A comprehensive literature review finds a substantial lack of complete techniques that incorporate cyber-physical systems, advanced data analytics, AI, standardized interoperability, human–machine cooperation and scalable adaptability. The suggested DF effectively fills this void by integrating cyber-physical system components, including DT, AM, SM and sensors into the manufacturing process. Using sophisticated data analytics and AI algorithms, the DF facilitates real-time data analysis, predictive maintenance, quality control and optimal resource allocation. In addition, the suggested DF ensures interoperability between diverse devices and systems by emphasizing standardized communication protocols and interfaces. The modular and adaptable architecture of the DF enables scalability and adaptation, allowing for rapid reaction to market conditions.
Originality/value
Based on the need of DF, this review presents a comprehensive approach to DF development using DTs, sensing devices, LAM and SM processes and provides current progress in this domain.
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María Higueras, Ana Carrasco-Huertas, Ana Isabel Calero-Castillo, Manuel Moreno Alcaide and Francisco José Collado Montero
This paper aims to study the suitability of a selection of 3D printing liquid photopolymer resins for their application in the cultural heritage context.
Abstract
Purpose
This paper aims to study the suitability of a selection of 3D printing liquid photopolymer resins for their application in the cultural heritage context.
Design/methodology/approach
The main concerns regarding the conservation and restoration of cultural assets are the chemical composition and long-term behavior of the new materials that will be in contact with the original object. Because of this, four different LED curing resins were exposed to an accelerated aging procedure and tested to identify the materials which demonstrated a better result. Some specific properties of the material (color, glossiness, pH and volatile organic compound emissions) were measured before and after the exposure.
Findings
Some of the properties measured reported good results demonstrating a decent stability against the selected aging conditions. The main changes were produced in the colorimetric aspect, probably indicating other chemical reactions in the material. Likewise, a case study could be also executed to demonstrate the usefulness of these materials in the cultural field.
Research limitations/implications
It is necessary to study in more detail the long-lasting behavior of the materials employed with these technologies. Further analysis should be carried out highlighting the chemical composition and degradation process of the materials proposed.
Originality/value
This paper contributes to the introduction of curing 3D printing resins in the restoration methodologies of cultural assets. For this, the study of a selection of properties represents the first stage to suggest or reject their use.
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