Direct numerical simulation of multiple interacting particles at intermediate Reynolds numbers

2015 ◽  
Vol 25 (2) ◽  
pp. 202-213
Author(s):  
Deming Nie ◽  
Limin Qiu ◽  
Xiaobin Zhang
Keyword(s):  
Linear Growth ◽  
Particle Density ◽  
Reynolds Numbers ◽  
Special Importance ◽  
Particle Collisions ◽  
Interacting Particles ◽  
Content Type ◽  
Initial Evolution ◽  
Direct Forcing ◽  
Initial Arrangement

Purpose – The purpose of this paper is to study the flow patterns and particle-particle collisions during the sedimentation of multiple circular particles under gravity at intermediate Reynolds numbers through direct numerical simulations (DNS). Design/methodology/approach – The previously developed lattice Boltzmann-direct forcing/fictitious domain (LB-DF/FD) method is adopted in this work to conduct DNS. Findings – It is found that the number of particle-particle collisions display a linear growth at long times after an initial evolution, resulting in a constant collision rate, which also depends the initial arrangement. Originality/value – The problem of particle-particle collisions during sedimentation with two kinds of particle density has not been considered before and it is of special importance in various industries.

Heat transfer enhancement using second mode self-oscillating structures

2019 ◽  
Vol 30 (7) ◽  
pp. 3827-3842
Author(s):  
Samer Ali ◽  
Zein Alabidin Shami ◽  
Ali Badran ◽  
Charbel Habchi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Flow Regime ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Content Type ◽  
Laminar Flow Regime ◽  
Second Mode

Purpose In this paper, self-sustained second mode oscillations of flexible vortex generator (FVG) are produced to enhance the heat transfer in two-dimensional laminar flow regime. The purpose of this study is to determine the critical Reynolds number at which FVG becomes more efficient than rigid vortex generators (RVGs). Design/methodology/approach Ten cases were studied with different Reynolds numbers varying from 200 to 2,000. The Nusselt number and friction coefficients of the FVG cases are compared to those of RVG and empty channel at the same Reynolds numbers. Findings For Reynolds numbers higher than 800, the FVG oscillates in the second mode causing a significant increase in the velocity gradients generating unsteady coherent flow structures. The highest performance was obtained at the maximum Reynolds number for which the global Nusselt number is improved by 35.3 and 41.4 per cent with respect to empty channel and rigid configuration, respectively. Moreover, the thermal enhancement factor corresponding to FVG is 72 per cent higher than that of RVG. Practical implications The results obtained here can help in the design of novel multifunctional heat exchangers/reactors by using flexible tabs and inserts instead of rigid ones. Originality/value The originality of this paper is the use of second mode oscillations of FVG to enhance heat transfer in laminar flow regime.

Enigmatic brothers’ uniquecorn poised to be a unicorn

2021 ◽  
Vol 11 (4) ◽  
pp. 1-54
Author(s):  
Mohammad Rishad Faridi ◽  
Saloni Sinha
Keyword(s):  
Strategic Management ◽  
Exponential Growth ◽  
Circular Economy ◽  
Linear Growth ◽  
Scale Up ◽  
Growth Mindset ◽  
Content Type ◽  
Generation Z ◽  
Start Up

Learning outcomes Appendix 1: Comic Frames A At the end of the case study discussion, students will able to as follows: Explain various growth strategies as a potential unicorn with the exponential growth mindset rather than linear growth mindset through adaptation of Massive Transformative Purpose (MTP) and Moonshot Thinking (MT). Demonstrate innovative and creative plans and ideas, with the ability to scale up in the circular economy. Review and summarize the power of Collaborative Innovation (CI). Compare and contrast different ways in dealing with Hedgehog and Fox style of leadership into the business. Appendix 2: Comic Frames B At the end of the case study discussion, students will able to as follows: Act with a growth strategy as a potential unicorn with the exponential growth mindset rather than linear growth mindset through adaptation of MTP and MT. Simulate innovative and creative plans and ideas, with the ability to scale up in the circular economy. Assess and leverage the power of CI. Decide and differentiate in dealing with Hedgehog and Fox style of leadership into the business. Case overview/synopsis Ankit Tripathi, was a compassionate 22-year-old, the typical lad from New Delhi, India, who seemed driven to change the world. His elder brother Atul Tripathi, a young, creative 25-year-old, was sat there next to him, beaming with pride and gratitude. Both brothers, being mechanical engineering graduates, had experienced the advancement of technology at the cost of Mother Earth. It pained them no end. It was the reason that Atul had refused to serve as an engineer in a government institution after graduating. The parents were shocked when Ankit followed suit. The brothers were poles apart in their personality and temperament, and it was rare to see them agree on anything in this way. Yet, they agreed to disagree with their parents and ventured into becoming entrepreneurs with a purpose and passion to salvage the environment. They had a vision, but without a proper roadmap, it would certainly be a tough game. Nevertheless, they boldly embarked upon their journey and established their start-up “Uneako” in 2019. “Uneako” was a calculated risk, taking into account family resistance (parents’ attitude/perception), personal conflicts (psychological), financial limitations (resources), shallow expertise (professionalism), social concern acceptability and low awareness (environment), government regulations (legalities/approvals), conflicts between brothers (personality issues), etc. Being from a nonbusiness family, the brothers had defied the wave of obstacles and challenges in daring to start their own business, putting at stake the hard-earned money of their father, Satendra Tripathi. Amidst so much social mockery, would Atul and Ankit succumb and become a laughing stock or would they find something that they could live and die for? Complexity Academic Level Appendix 1: Comic Frames A: This case has been particularly focused on undergraduate level students pursuing business or commerce programs. Especially those studying core courses, for example, entrepreneurial and strategic management. Appendix 2: Comic Frames B: This case has been particularly focused postgraduate-early stage or higher level students pursuing business or commerce programs. Particularly those specializing in entrepreneurial and strategic management courses. Also, can be taught in the entrepreneurial or start-up workshops. Supplementary materials www.pewresearch.org/topics/generation-z/ Paulynice. J.P., (2019) “From Idea to Reality: An Entrepreneur’s Guide to Meaningful Business Growth” Paulynice Consulting Group. Hardy.D., (2015) “The Entrepreneur Roller Coaster: It’s Your Turn to Join The Ride” Success Publishers. Wadhwa.V., Amla.I., Salkever.A., (2020) “From Incremental to Exponential” Berrett-Koehler Publishers. Sustainable Entrepreneurship: Business Success through Sustainability edited by Christina Weidinger, Franz Fischler, René Schmidpeter, Springer 2014. Teaching notes are available for educators only. Subject code CSS 3: Entrepreneurship.

Investigating the effect of nanoparticles diameter on turbulent flow and heat transfer properties of non-Newtonian carboxymethyl cellulose/CuO fluid in a microtube

2019 ◽  
Vol 29 (5) ◽  
pp. 1699-1723 ◽  
Author(s):  
Ali Rahimi Gheynani ◽  
Omid Ali Akbari ◽  
Majid Zarringhalam ◽  
Gholamreza Ahmadi Sheikh Shabani ◽  
Abdulwahab A. Alnaqi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Electronic Devices ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Vlsi Circuits ◽  
Convection Heat Transfer Coefficient ◽  
Content Type ◽  
Competing Interests

Purpose Although many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Design/methodology/approach Present numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10−6 is considered for saving computer memory usage and the time for the numerical solving procedure. Findings In constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent. Research limitations/implications The numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it. Practical implications The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Originality/value This manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.

Effect of corrugated skins on the aerodynamic performance of the cambered airfoils

2018 ◽  
Vol 35 (3) ◽  
pp. 1567-1582 ◽  
Author(s):  
Masoud Kharati-koopaee ◽  
Mahmood Fallahzadeh-abarghooee
Keyword(s):  
Drag Coefficient ◽  
Design Methodology ◽  
Reynolds Numbers ◽  
Numerical Approach ◽  
Aerodynamic Performance ◽  
Content Type ◽  
Lift Curve ◽  
Finite Volume Approach ◽  
Naca 0012 ◽  
Relative Curve

Purpose This paper aims to study the effect of corrugated skins on the aerodynamic performance of the cambered NACA 0012 airfoils at different corrugations parameters, maximum cambers, Reynolds numbers and maximum camber locations. Design/methodology/approach In this work, numerical approach is concerned, and results are obtained based on the finite volume approach. To characterize the effect of corrugated skins, the NACA 0012-corrugated airfoil section is chosen as the base airfoil, and different cambered corrugated airfoil sections are obtained by inclusion the camber to the base airfoil. In this research, the corrugation shape is a sinusoidal wave and corrugated skins are in the aft 30 per cent of airfoil chord. To investigate the effect of corrugations on the cambered sections, the drag coefficient and averaged lift curve slope for the corrugated airfoils are compared to those of the corresponding smooth sections. Findings Results indicate that the effect of increase in the maximum camber and also Reynolds number on the relative zero-incidence drag coefficient is of little importance at low corrugation amplitudes, whereas at high corrugation, amplitude results in different behaviors. It is found that as the maximum camber increases, the deterioration in the relative curve slope introduced by corrugated skins is reduced, and reduction in this deterioration is significant for high corrugation amplitudes airfoils. It is shown that an increase in the maximum camber location has nearly no effect on the relative zero-incidence drag coefficient and also relative lift curve slope. Originality/value The outcome of the present research provides the clues for better understanding of the effect of different corrugations parameters on the aerodynamic performance of the unmanned air vehicles to have as high aerodynamic performance as possible in different mission profiles of such vehicles.

A note on the flow coefficients of capillary tube and small orifice restrictors exposed to very low Reynolds number flow

2005 ◽  
Vol 57 (3) ◽  
pp. 116-120 ◽  
Author(s):  
Suat Canbazoğlu ◽  
Fazıl Canbulut
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Capillary Tube ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Hydraulic Control ◽  
Capillary Tubes ◽  
Content Type ◽  
Control Devices ◽  
Low Reynolds

PurposeThe main objective of this study was to obtain the flow restricting capacity by determining their flow coefficients and to investigate the unsteady flow with low Reynolds number in the flow‐restricting devices such as orifices and capillary tubes having small diameters.Design/methodology/approachThere is an enormous literature on the flow of Newtonian fluids through capillaries and orifices particularly in many application fields of the mechanical and chemical engineering. But most of the experimental results in literature are given for steady flows at moderate and high Reynolds numbers (Re>500). In this study, the unsteady flow at low Reynolds number (10<Re<650) through flow‐restricting devices such as orifices and capillary tubes having very small diameters between 0.35 and 0.70 mm were experimentally investigated.FindingsThe capillary tubes have much more capillarity property with respect to equal diameter orifices. Increasing the ratio of capillary tube length to tube diameter and decreasing the ratio of orifice diameter to pipe diameter before orifice increase the throttling or restricting property of the orifices and the capillary tubes. The orifices can be preferred to the capillary tubes having the same diameter at the same system pressure for the hydraulic systems or circuits requiring small velocity variations. The capillary tubes provide higher pressure losses and they can be also used as hydraulic accumulators in hydraulic control devices to attenuate flow‐induced vibrations because of their large pressure coefficients. An important feature of the results obtained for capillary tubes and small orifices is that as the d/D for orifices increases and the L/d reduces for capillary tubes, higher values C are obtained and the transition from viscous to inertia‐controlled flow appears to take place at lower Reynolds numbers. This may be explained by the fact that for small orifices with high d/D ratios and for capillary tubes with small L/d ratios, the losses due to viscous shear are small. Another important feature of the results is that the least variations in C for small orifices and the higher variations in C for capillary tubes occur when the d/D and L/d ratios are smallest. This has favourable implications in hydraulic control devices since a constant value for the C may be assumed even at relatively low values of Re.Originality/valueTo the authors' knowledge, there is not enough information in the literature about the flow coefficients of unsteady flows through capillary tubes and small orifices at low Reynolds numbers. This paper fulfils this gap.

An empirical analysis of the effect of MBA programs on organizational success

2014 ◽  
Vol 28 (4) ◽  
pp. 451-460 ◽  
Author(s):  
Atul Gupta ◽  
Sara E. Bennett
Keyword(s):  
Organizational Performance ◽  
Work Experience ◽  
Local Governments ◽  
Relevant Literature ◽  
Local Economy ◽  
Special Importance ◽  
Recent Criticism ◽  
Mba Programs ◽  
Content Type ◽  
Mba Program

Purpose – The purpose of this paper is to empirically examine the value of Masters of Business Administration (MBA) degree. The authors aim to bridge the gap between the theory and individual understanding of the value of an MBA program. Design/methodology/approach – This empirical paper used a non-experimental design to test a proposed model based on a review of relevant literature. MBA alumni completed surveys capturing the constructs researched. Findings – The findings of this research suggest that an MBA adds value to both MBA alumni as well as the organizations who hire them. The main source of this value is the knowledge and skills acquired while taking academic courses in the MBA program. Research limitations/implications – The implication of this research is that an MBA does add value to students that is not necessarily obtained through work experience alone. Practical implications – The MBA degree qualifies an individual to manage an organization. An MBA does provide high potential for return on investment to both individuals well as the organization who hires them. Social implications – Economic growth requires entrepreneurs, professionals, business specialists, and managers. The research findings provide evidence that MBA program graduates do make a significant contribution toward improving the organization employing them. These profitable organizations in turn invest back in the community they operate in and help to improve the overall socio-economic fabric of the local economy. The results of this study also suggest that investment in MBA programs by local governments could bring back significant returns to the community in terms of job growth and availability of quality workforce. Originality/value – Although a considerable amount has been written about the value of an MBA education, there is still a lack of research in the area linking human capital with organizational performance for MBA graduates. This contribution is also of special importance amid the recent criticism of the MBA by prominent management scholars.

New thermal-hydraulic correlations for printed circuit heat exchangers (PCHEs) with zigzag channels under high Reynolds numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Carolina P. Naveira-Cotta ◽  
Jian Su ◽  
Paulo Lucena Kreppel Paes ◽  
Philippe R. Egmont ◽  
Rodrigo P. M. Moreira ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Design Parameters ◽  
Channel Diameter ◽  
Content Type ◽  
Printed Circuit ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
The Impact

Purpose The purpose of this paper is to investigate the impact of semi-circular zigzag-channel printed circuit heat exchanger (PCHE) design parameters on heat transfer and pressure drop of flows under high Reynolds numbers and provide new thermal-hydraulic correlations relevant to conditions encountered in natural gas processing plants. Design/methodology/approach The correlations were developed using three-dimensional steady-state computational fluid dynamics simulations with varying semicircular channel diameter (from 1 to 5 mm), zigzag angle (from 15° to 45°) and Reynolds number (from 40,000 to 100,000). The simulation results were validated by comparison with experimental results and existing correlations. Findings The results revealed that the thermal-hydraulic performance was mostly affected by the zigzag angle, followed by the ratio of the zigzag channel length to the hydraulic diameter. Overall, smaller zigzag angles favored heat transfer intensification while keeping reasonably low pressure drops. Originality/value This study is, to date, the only one providing thermal-hydraulic correlations for PCHEs with zigzag channels under high Reynolds numbers. Besides, the broad range of parameters considered makes the proposed correlations valuable PCHE design tools.

Heat transfer promotion in channel laminar flow employing a slab with slits and inclined ribs protruding across

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shiang-Wuu Perng ◽  
Horng Wen Wu ◽  
Jun-Kuan Wu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Reynolds Numbers ◽  
Thermal Engineering ◽  
Channel Height ◽  
The Novel ◽  
Maximum Increase ◽  
Content Type ◽  
Vertical Location ◽  
Cooling Mechanism

Purpose The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across. Design/methodology/approach The novel design of this study is performed through making the slits in the slab (C1–C3: with slits; C4–C6: without slits) and changing the vertical location of this slab (1/4, 1/2 and 3/4 channel height). The thermal fluid characteristics of all cases are analyzed for various Reynolds numbers (500, 1,000, 1,500 and 2,000) by the SIMPLE-C algorithm. Findings The results display that the ribbed slab effectively improves the heat transfer. The slits can modify the flow field in the vortexes around the inclined ribs and remove more heat from this zone to promote the heat transfer. As compared with C0 (without a slab), C2 (the slab with slits and inclined ribs protruding across located vertically on the 3/4 channel height) raises the averaged Nusselt number up to 27.7% at Re = 2,000. As compared with C4 (without slits), C1 (with slits) gains the maximum increase in the averaged Nusselt number by 5.07% at Re = 1,000. Research limitations/implications The constant thermo-physical properties of incompressible fluid and the steady flow are considered in this study. Practical implications The numerical results will profit the design of heated passageway using a slab with slits and inclined ribs protruding across to acquire better heat transfer promotion. Originality/value This slab with slits and inclined ribs protruding across can be applied to the heat transfer promotion and thus be viewed as a useful cooling mechanism in the thermal engineering.

Numerical investigation for endoscopic and Soret-Dufour effects on MHD peristaltic activity of Carreau fluid

2018 ◽  
Vol 28 (12) ◽  
pp. 2960-2978 ◽  
Author(s):  
Tasawar Hayat ◽  
Javaria Akram ◽  
Hina Zahir ◽  
Ahmad Alsaedi
Keyword(s):  
Weissenberg Number ◽  
Navier Stokes ◽  
Special Importance ◽  
Carreau Fluid ◽  
Convective Boundary ◽  
Soret And Dufour Effects ◽  
Content Type ◽  
Dufour Number ◽  
Energy Equations ◽  
The Impact

Purpose The purpose of this paper is to emphasize on the impact of endoscope in MHD peristaltic flow of Carreau fluid. Heat and mass transfer phenomena are comprised of Soret and Dufour effects. Influences of mixed convection and viscous dissipation are also accounted. Wall properties and convective boundary conditions are used. Design/methodology/approach The Navier–Stokes and energy equations used the lubrication approach. The reduced system of equations is executed numerically. The graphical illustration of velocity, temperature, concentration and heat transfer coefficient for various emerging parameters is discussed. Findings The response of Weissenberg number and power law index is decaying toward velocity and temperature. Moreover impression of Soret and Dufour number on temperature is quite reverse to that of concentration. Originality/value The titled problem with the various considered effects has not been solved before, and it is of special importance in various industries. The problem is original.

The Motion of Particles Inside a Droplet

1982 ◽  
Vol 104 (3) ◽  
pp. 438-445 ◽  
Author(s):  
J. N. Chung
Keyword(s):  
Heterogeneous Nucleation ◽  
Characteristic Time ◽  
Particle Density ◽  
Equations Of Motion ◽  
Reynolds Numbers ◽  
Droplet Surface ◽  
Relative Importance ◽  
Particle Agglomeration ◽  
Internal Circulation ◽  
Coal Particles

Equations of motion for particles translating inside a droplet with internal circulation were developed. The forces experienced by these particles and their relative importance are also summarized. Sample calculations for coal particles in oil droplets show that for high-droplet Reynolds numbers, particles will accumulate near the droplet surface before substantial evaporation of the droplet, based on the results that the characteristic time of transport is two orders of magnitude smaller than the droplet lifetime. These accumulations of particles near the droplet surface will probably result in particle agglomeration. Fow low-droplet Reynolds numbers, the particles are making slow looping motions and the characteristic time of transport is comparable to the droplet lifetime. This results in a more even distribution of particles in the droplet with slightly higher particle density near the surface. This indicates a higher particle burning rate and the possibility of internal boiling and microexplosion due to heterogeneous nucleation initiated from those coal particles.

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