Simulations of reactive supersonic/subsonic flow interactions for space launcher applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lorris Charrier ◽  
Lorris Charrier ◽  
Mathieu Jubera ◽  
Grégoire Pont ◽  
Simon Marié ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Early Stage ◽  
Mixing Layer ◽  
Computational Cost ◽  
Cost Effective ◽  
Base Flow ◽  
Content Type ◽  
Planar Laser ◽  
The Impact ◽  
Space Launcher

Purpose The design of a space launcher requires some considerations about the unsteady loads and heat transfer occurring at the base of the structure. In particular, these phenomena are predominant during the early stage of the flight. This paper aims to evaluate the ability of the unstructured, high order finite-volume CFD solver FLUSEPA, developed by Airbus Safran Launchers, to accurately describe these phenomena. Design/methodology/approach This paper first performs a steady simulation on a base flow around a four-clustered rocket configuration. Results are compared with NASA experiments and Loci-CHEM simulations. Then, unsteady simulations of supersonic H2/air reacting mixing layer based on the experiment of Miller, Bowman and Mungal are performed. Three meshes with different cells number are used to study the impact of spatial resolution. Instantaneous and time-averaged concentrations are compared with the combined OH/acetone planar laser-induced fluorescence imaging from the experiment. Findings FLUSEPA satisfactorily predicts the base heat flux at the base of a four-clustered rocket configuration. NASA Loci-CHEM reactive simulations indicate that afterburning plays an important role and should not be neglected. The unsteady reactive computation of a supersonic mixing layer shows that FLUSEPA is also able to accurately predict flow structures and interactions. However, the complexity of the experiment and the lack of details concerning the facility prevents from obtaining satisfactory converged results. Originality/value This study is the first step on the development of a cost-effective method aiming at predicting unsteady loads and heat transfer on space launchers using an unsteady and reactive model for the CDF calculations. It uses original techniques such as conservative CHIMERA-like overset grids, local re-centering of fluxes and local adaptive time-stepping to reduce computational cost while being robust and accurate.

Stock markets' reaction to COVID-19: evidence from the six WHO regions

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Anas Ali Al-Qudah ◽  
Asma Houcine
Keyword(s):  
Stock Returns ◽  
Stock Markets ◽  
Early Stage ◽  
Eastern Mediterranean ◽  
Abnormal Returns ◽  
Western Pacific ◽  
Content Type ◽  
Panel Data Regression ◽  
Daily Stock Returns ◽  
The Impact

PurposeThis study investigates the effects of the COVID-19 outbreak on daily stock returns for the six major affected WHO Regions, namely: Africa, Americas, Eastern Mediterranean, Europe, South-East Asia and Western Pacific.Design/methodology/approachThis study uses an event study method and panel-data regression models to examine the effect of the daily increase in the number of COVID-19 confirmed cases on daily stock returns from 1 March to 1 August 2020 for the leading stock market in major affected countries in the WHO regions.FindingsThe results reveal an adverse impact of the daily increasing number of COVID-19 cases on stock returns and stock markets fell quickly in response to the pandemic. The findings also suggest that negative market reaction was strong during the early stage of the outbreak between the 26th and 35th days after the initial confirmed cases. We further find that stock markets in the Western Pacific region experienced more negative abnormal returns as compared to other regions. The results also confirm that feelings of fear among investors turned out to be a mediator and a transmission channel for the effect of COVID-19 outbreak on the stock markets.Research limitations/implicationsThis study contributes to financial literature in two ways. First, we contribute to existing literature that has examined the effect of various catastrophes and crises on the stock markets Second, we contribute to the recent emerging literature that examines the impact of COVID-19 on financial markets.Practical implicationsThe study may have implications for policymakers to deal with this outbreak without triggering uncertainty in stock markets and reassure investors' confidence. The study may also be of interest to investors, managers, financial analysts by revealing how the stock markets quickly respond to outbreaks.Originality/valueThis study is the first study to examine the impact of the COVID-19 outbreak on the leading stock markets of the WHO regions.

Kit preparation for mixed-model assembly: efficiency impact of confirmation methods

2019 ◽  
Vol 119 (3) ◽  
pp. 547-560 ◽  
Author(s):  
Patrik Fager
Keyword(s):  
Learning Curve ◽  
Design Methodology ◽  
Mixed Model ◽  
Early Stage ◽  
Time Efficiency ◽  
Content Type ◽  
Order Batching ◽  
The Impact ◽  
Mixed Model Assembly ◽  
Practical Implications

PurposeConfirmations are applied in kit preparation for mixed-model assembly to promote quality, but research that explains the impact on time efficiency has been lacking. The purpose of this paper is to determine the extent to which the type of confirmation method relates to time-efficient kit preparation when order batching is applied.Design/methodology/approachAn industrially relevant laboratory experiment is applied, simulating kit preparation with order batching for mixed-model assembly. The time efficiency is studied as associated with four confirmation methods – barcode ring scanner, button presses, voice commands and RFID-reading wristbands – when applied as pick-from and place-to confirmation. Furthermore, the paper also considers the quality outcome.FindingsEfficiency is promoted by methods that minimise interrupting the picker’s motions when performing pick-from confirmations and with methods that allow each hand to place components and perform place-to confirmations simultaneously – here represented by button presses and RFID-reading wristbands. Moreover, combining various methods for the tasks of pick-from or place-to confirmation can benefit efficiency.Research limitations/implicationsPickers at an early stage of the learning curve (one shift of training) were considered.Practical implicationsThe findings promote the customised applications of picking information systems in industry.Social implicationsCombining various methods for the tasks of pick-from and place-to confirmation can provide more fitting applications that better align with the picker’s preferences.Originality/valueCombinations of various methods when applied as either pick-from or place-to confirmation, or both, are studied.

A comprehensive survey on utilization of hybrid nanofluid in plate heat exchanger with various number of plates

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faraz Afshari ◽  
Azim Doğuş Tuncer ◽  
Adnan Sözen ◽  
Halil Ibrahim Variyenli ◽  
Ataollah Khanlari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Flow Behavior ◽  
Plate Heat Exchanger ◽  
Single Type ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Plate Heat ◽  
The Impact

Purpose Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat exchangers. Different types of nanofluids are available and used in different applications. The main purpose of this study is to investigate the effects of using hybrid nanofluid and number of plates on the performance of plate heat exchanger. In this study, TiO2/water single nanofluid and TiO2-Al2O3/water hybrid nanofluid with 1% particle weight ratio have been used to prepare hybrid nanofluid to use in plate type heat exchangers with three various number of plates including 8, 12 and 16. Design/methodology/approach The experiments have been conducted with the aim of examining the impact of plates number and used nanofluids on heat transfer enhancement. The performance tests have been done at 40°C, 45°C, 50°C and 55°C set outlet temperatures and in five various Reynolds numbers between 1,600 and 3,800. Also, numerical simulation has been applied to verify the heat and flow behavior inside the heat exchangers. Findings The results indicated that using both nanofluids raised the thermal performance of all tested exchangers which have a various number of plates. While the major outcomes of this study showed that TiO2-Al2O3/water hybrid nanofluid has priority when compared to TiO2/water single type nanofluid. Utilization of TiO2-Al2O3/water nanofluid led to obtaining an average improvement of 7.5%, 9.6% and 12.3% in heat transfer of heat exchangers with 8, 12 and 16 plates, respectively. Originality/value In the present work, experimental and numerical analyzes have been conducted to investigate the influence of using TiO2-Al2O3/water hybrid nanofluid in various plate heat exchangers. The attained findings showed successful utilization of TiO2-Al2O3/water nanofluid. Based on the obtained results increasing the number of plates in the heat exchanger caused to obtain more increment by using both types of nanofluids.

Evaluation of bend curvature of superheater tube using CFD analysis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sushovan Chatterjee ◽  
Subhasish Das ◽  
Neelam Kumar Sarma
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Flow Behavior ◽  
Radius Of Curvature ◽  
Pass System ◽  
Maximum Heat ◽  
Curvature Ratio ◽  
Content Type ◽  
Superheater Tube ◽  
The Impact

Purpose The heat transfer within a heat exchanger is highly influenced by geometry of the components especially those with hollow structures like tubes. This paper aims to intend toward the study of efficient and optimized heat transfer in the bends of superheater tubes, with different curvature ratio at constant Reynolds Number. Design/methodology/approach The effect of changing curvature ratio on enthalpy of the fluid passing through the superheater tubes for multi-pass system has been studied with the aid of computational fluid dynamics (CFD) using ANSYS 14.0. Initially a superheater tube with two pass system has been examined with different curvature ratios of 1.425, 1.56, 1.71, 1.85 and 1.99. An industry specified curvature ratio of 1.71 with two pass is investigated, and a comparative assessment has been carried out. This is intended toward obtaining an optimized radius of curvature of the bend for enhancement of heat transfer. Findings The results obtained from software simulation revealed that the curvature ratio of 1.85 provides maximum heat transfer to the fluid flowing through the tube with two pass. This result has been found to be consistent with higher number of passes as well. The effect of secondary flow in bends of curvature has also been illustrated in the present work. Research limitations/implications The study of heat transfer in thermodynamic systems is a never-ending process and has to be continued for the upliftment of power plant performances. This study has been conducted on steady flow behavior of the fluid which may be upgraded by carrying out the same in transient mode. The impact of different curvature ratios on some important parameters such as heat transfer coefficients will certainly upgrade the value of research. Originality/value This computational study provided comprehensive information on fluid flow behavior and its effect on heat transfer in bends of curvature of superheater tubes inside the boiler. It also provides information on optimized bend of curvature for efficient heat transfer process.

The impact of media on entrepreneurship participation: a cross-country panel data analysis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Muhammad Arshad ◽  
Sharjeel Saleem ◽  
Rabeeya Raoof ◽  
Naheed Sultana
Keyword(s):  
Panel Data ◽  
New Product Development ◽  
Indirect Effect ◽  
Cognitive Theory ◽  
Early Stage ◽  
Entrepreneurial Intention ◽  
Content Type ◽  
Informal Investment ◽  
The Impact ◽  
The Relationship

Purpose Unlike the previous studies that examined the direct relationship between media attention on entrepreneurship (MAE) and entrepreneurship participation, this paper aims to examine the mediated link through entrepreneurial intention. Design/methodology/approach The cognitive theory of media provides the foundation for predictions that primary outcome of MAE is the entrepreneurial intention which in turn affects the different types of entrepreneurship participation (early-stage startup activities, new product development [NPD] activities and informal investment activities). The test of the hypothesized model relies on panel data for 2010–2015 on 40 developing and developed countries taken from the Global Entrepreneurship Monitor report of 2015. Findings MAE has an indirect effect on two types of entrepreneurship participation (early-stage startup activities and informal investment activities) via entrepreneurial intention, whereas there is no direct or indirect effect of MAE on NPD activities. The findings also suggest when the entrepreneurial intention is added as a mediator in the model; the direct effect of MAE on early-stage entrepreneurial activities becomes insignificant. Originality/value To the best of the authors’ knowledge, this is the first study in its nature which established the relationship between MAE and entrepreneurial intention. In addition, this study also explained the mediation mechanism between the relationship of MAE and entrepreneurship participation by using the panel data.

Is business planning useful for the new venture emergence?

2018 ◽  
Vol 12 (4) ◽  
pp. 847-870 ◽  
Author(s):  
Ya-long Wei ◽  
Dan Long ◽  
Yao-kuang Li ◽  
Xu-sheng Cheng
Keyword(s):  
Early Stage ◽  
Contextual Factors ◽  
New Ventures ◽  
Panel Study ◽  
Binary Logistic Regression ◽  
New Venture ◽  
Business Planning ◽  
Content Type ◽  
Innovative Products ◽  
The Impact

Purpose The purpose of this paper is to build a research model to examine the effects of business planning on the new venture emergence, as well as to examine the moderating effects of innovativeness of products. Design/methodology/approach Four hypotheses are put forward and examined by hierarchical binary logistic regression. The data of this paper are based on the first two waves of data from Chinese Panel Study of Entrepreneurial Dynamics project. Findings Results show that engaging in business planning has a positive effect on the new venture emergence, and the timing of business planning does not affect the new venture emergence significantly. This study also finds that the innovativeness of products has a positive moderating effect on the relationship between the timing of business planning and the new venture emergence. Research limitations/implications This study has some limitations. The innovativeness of products is measured by a single indicator, which may not completely reflect the meaning of the attribute. Moreover, this study explores new ventures only in the nascent stage. Practical implications The study is useful for entrepreneurs to realize the importance of business planning. First, engaging in business planning in early start-up stage is a very valuable activity, because business planning can help new ventures reduce the loss caused by trial and error learning. Second, engaging in business planning is more likely to ensure high innovative products quickly be accepted by the market. Because in the process of new venture emergence, the legitimacy signal to stakeholders can be transmitted and new products can be promoted to get support and recognition from stakeholder through the business plan. Originality/value This paper focuses on the early stage of new venture life cycle and the contextual factors to explore the influence of business planning on the new venture emergence under the logic of legitimacy. This paper could enrich business planning research from the perspective of legitimacy theory by inspiring scholars to focus on the differences between new ventures and mature enterprises and to offer proposals of legitimation strategies suitable for new ventures. Meanwhile, this study contributes to the understanding of the contextual factors of business planning. And it discusses the impact of the attribute in business planning on the new venture emergence, which helps scholars to get a deep thought about the value of business planning in entrepreneurial process.

Dufour and Soret effects on Darcy-Forchheimer flow of second-grade fluid with the variable magnetic field and thermal conductivity

2020 ◽  
Vol 30 (9) ◽  
pp. 4331-4347 ◽  
Author(s):  
Ambreen A. Khan ◽  
S. Naeem ◽  
R. Ellahi ◽  
Sadiq M. Sait ◽  
K. Vafai
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Variable Magnetic Field ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Content Type ◽  
Grade Fluid ◽  
The Impact ◽  
Forchheimer Flow

Purpose This study aims to investigate the effect of two-dimensional Darcy-Forchheimer flow over second-grade fluid with linear stretching. Heat transfer through convective boundary conditions is taken into account. Design/methodology/approach Nonlinear coupled governing equations are tackled with a homotopy algorithm, while for numerical computation the computer software package BVPh 2.0 is used. The convergence analysis is also presented for the validation of analytical and numerical results. Findings Valuation for the impact of key parameters such as variable thermal conductivity, Dufour and Soret effects and variable magnetic field in an electrically conducted fluid on the velocity, concentration and temperature profiles are graphically illustrated. It is observed from the results that temperature distribution rises by Dufour number whereas concentration distribution rises by Soret number. The Forchheimer number and porosity parameter raise the skin friction coefficient. The permeable medium has a vital impact and can help in reining the rate of heat transfer. Practical implications The permeable medium has a vital impact and can help in reining the rate of heat transfer. Originality/value To the best of the authors’ knowledge, this study is reported for the first time.

Developing a mentoring programme in the chemical industry

2019 ◽  
Vol 31 (1) ◽  
pp. 42-58 ◽  
Author(s):  
Marta Santos ◽  
Cláudia Pereira ◽  
Daniel Silva ◽  
Maria Antónia Cadilhe ◽  
Liliana Cunha
Keyword(s):  
Chemical Industry ◽  
Early Stage ◽  
Methodological Approach ◽  
Training Programme ◽  
Work Situation ◽  
Content Type ◽  
New Employees ◽  
Know How ◽  
Relationship Of ◽  
The Impact

Purpose The purpose of this paper is to analyse a programme designed to welcome and train new employees, implemented in a chemical industry, privileging the transmission of know-how as a dynamic process where learning is co-constructed in the course of the activity. Design/methodology/approach The design of the programme was based on the analysis of the work performed in real context by operators and supervisors. The data about the programme’s evaluation were collected by questionnaire, assessing the trainees’ global development and the impact of the training programme (after six months). Findings This paper involves designing, planning and implementing “4 × 4 Training”, a training programme for young trainees. Combining in-class training with an extensive component of on-the-job mentoring, the programme involved trainees, mentors and internal trainers, monitored by work psychologists. The results show both the trainees and the mentors evaluate the programme positively. The professional transmission stands out as an activity that is thought through and defined in group, assisted by a mentoring relationship of mutual learning. Practical implications When planning and developing intergenerational transmission processes, it is crucial to consider the organisational conditions, to involve from an early stage the key players of each work situation and to guarantee that the mentoring activity and the productive activity overlap coherently. Originality/value It is an innovative process to integrate trainees in the chemical industry in Portugal. The methodological approach and the findings provide a first framework that justifies the relevance of the transmission of know-how through a real work situation.

Health economic analysis of pharmaceutical inventory levels

2020 ◽  
Vol 10 (4) ◽  
pp. 603-628
Author(s):  
Peter Benjamin Ellison ◽  
Robert A. Cook
Keyword(s):  
Health Economics ◽  
Cost Effective ◽  
Current Approach ◽  
Inventory Theory ◽  
Health Economic Analysis ◽  
Content Type ◽  
Wide Range ◽  
Humanitarian Supply Chain ◽  
Demand Coverage ◽  
The Impact

PurposeHumanitarian crises increase vulnerability of children to pneumonia, so aid agencies store pharmaceuticals in advance of this demand. Decisions on how much to store are plagued by many diverse challenges as is common in humanitarian contexts, so this study considers storing more medications to improve the relatively poor (∼80) demand coverage at a representative aid agency.Design/methodology/approachThe paper combines inventory theory with health economics to calculate the impact inventory increases would have on the final cost of pneumonia treatment. It can then assess to what extent inventory can be increased while pneumonia treatment remains cost effective.FindingsThe study finds that more drug investment has only a small effect on the final treatment cost. Substantial drug inventory increases remain well within established guidelines for highly cost-effective treatments, so the agency should consider large increases as an efficient use of funding.Research limitations/implicationsThe study focuses on pneumonia treatment only to allow sufficient depth of analysis. Further research could look at many other treatments using the same approach, although some problem scenarios will include complicating parameters like drug perishability.Practical implicationsThe level of pharmaceutical inventory at humanitarian warehouses is a high-value decision for the aid sector. The method shows the potential for health economics to provide practical decision support for a wide range of humanitarian and ministry of health warehouse operations. While large increases in inventory investment are within guidelines, there is an asymptotically increasing cost as demand coverage approaches 100%. As a result, decision makers may want to set a target demand coverage (e.g. 99%) and allocate remaining aid funding to other projects.Originality/valueMany humanitarian supply chain decisions lack analytical support due to issues with complexity, scale or a lack of reliable input data, and this study is the first to provide analytical insights which can greatly improve the current approach to inventory control policies for pneumonia medications and beyond.

scholarly journals Impact of convection on thermographic analysis of silver based thermal joints

2020 ◽  
Vol 32 (4) ◽  
pp. 241-246
Author(s):  
Krzysztof Jakub Stojek ◽  
Jan Felba ◽  
Johann Nicolics ◽  
Dominik Wołczyński
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Energy Loss ◽  
Thermal Resistance ◽  
Analysis Method ◽  
Content Type ◽  
Heat Transfer Efficiency ◽  
Lowered Pressure ◽  
Thermographic Analysis ◽  
The Impact

Purpose This paper aims to develop thermal analysis method of thermal joints characterization. The impact on convection on thermal resistance analysis with use thermography for silver-based thermal joints were investigated for non-metallized and metalized semiconductor surfaces. Heat transfer efficiency depends on thermal conductivity; radiation was used to perform thermographic analysis; the convection is energy loss, so its removing might improve measurements accuracy. Design/methodology/approach Investigation of thermal joints analysis method was focused on determination of convection impact on thermal resistance thermographic analysis method. Measuring samples placed in vacuum chamber with lowered pressure requires transparent window for infrared radiation that is used for thermographic analysis. Impact of infrared window and convection on temperature measurements and thermal resistance were referred. Findings The results showed that the silicon window allowed to perform thermal analysis through, and the convection was heat transfer mode which create 15% energy loss. Originality/value It is possible to measure thermal resistance for silver-based thermal joints with convection eliminated to improve measurements accuracy.

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