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1

Soret and Dufour effects on an unsteady MHD flow about a permeable rotating vertical cone with variable fluid properties

Jamir Temjennaro, Konwar Hemanta

Archives of Thermodynamics

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2024

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Vol. 45, no 1

75--86

EN

The objective of the present work is to examine the characteristics of unsteady incompressible magnetohydrodynamic fluid flow around a permeable rotating vertical cone. The effects of thermal radiation, viscous dissipation, and the Soret and Dufour effects are investigated in the analysis of heat and mass transfer. The viscosity of the fluid is considered inversely proportional to the temperature, and the thermal conductivity of the fluid is considered directly proportional to the temperature. The governing equations are converted into ordinary differential equations using suitable similarity transformations, which are then solved numerically using bvp4c from MATLAB. Results obtained in this study are in excellent correlation with previously conducted studies. The results demonstrate that the Dufour and Soret effects subsequently reduce the heat transit rate (by 3.3%) and mass transit rate (by 1.2%) of the system. It is also detected that fluids with higher viscosity tend to increase tangential skin friction (+8.9%) and azimuthal skin friction (+8.3%). The heat transit rate of the system is found to be more efficient for fluids with higher viscosity and lower thermal conductivity and Eckert numbers. Furthermore, the thickness of the momentum, thermal, and concentration boundary layers significantly reduces while the heat and mass transit rates (+17.8% and +18.3%, respectively) of the system become more efficient for greater values of the unsteadiness parameter.

2

Electrospinning of Aligned Fibrous Materials on an Inner Rapidly Rotating Cone Surface

Tomaszewski W., Kudra M, Ciechańska D., Szadkowski M., Gutowska A.

Fibres & Textiles in Eastern Europe

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2012

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Vol. 20, no. 6B (96)

44--51

EN

The paper presents a new way for producing fibrous mats with aligned micro- and nanofibres by electrospinning technique using a fast rotating filter basket of a properly adapted commercial centrifugal juicer as the collecting electrode. This method was used to obtain the fibrous materials from polylactide (PLA) and polyvinyl alcohol (PVA) with different degrees of fibres aligned depending on the linear velocity of the rotating substrate. The highest degree of the fibre alignment, measured by the planar orientation factor, with a value of 0.8 - 0.9, was obtained at the linear speeds of the rotating substrate in the range of 22 - 36 m/s. Using the gravimetric method, the velocity of fibre formation during electrospinning was tested under different conditions, i.e. at the immobile substrate as well as rapidly rotating, reaching values ranging from 4 to 200 m/s. The investigations suggest that electrospinning of the fibres on the rapidly rotating substrate is not only a modification of their receiving, but also significantly changes the nature of the fibre formation in this spinning technique.

PL

W artykule przedstawiono nowy sposób wytwarzania mat włóknistych o uszeregowanych mikro- i nano-włóknach techniką elektroprzędzenia, wykorzystujący szybkoobrotowy kosz filtracyjny w odpowiednio dostosowanej komercyjnej sokowirówce odśrodkowej jako elektrodę odbiorczą. Metodą tą uzyskano materiały włókniste z polilaktydu (PLA) i polialkoholu winylowego (PVA) o różnym stopniu uszeregowania włókien, zależnym od szybkości liniowej obracającego się podłoża. Najwyższy stopień uszeregowania włókien, mierzony czynnikiem orientacji płaskiej, osiągnął wartości 0,8-0,9 przy szybkości liniowej obracającego się podłoża w zakresie 22-36 m/s. Stosując metodę grawimetryczną badano szybkość formowania włókien przy elektroprzędzeniu w różnych warunkach, tak przy nieruchomym jak i szybko obracającym się podłożu, osiągając wartości w zakresie od 4 do 200 m/s. Wskazano także, że elektroprzędzenie włókien z odbiorem na szybko obracające się podłoże nie jest tylko modyfikacją odbioru tych włókien, ale istotnie zmienia charakter formowania włókien w tej technice przędzenia.

3

Absolute instability in the compressible boundary layer of the rotating cone

Tuliszka-Sznitko E.

Research Bulletin / Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics

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1999

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nr 9

151-156

EN

In the present paper the instability character (absolute/convective) of compressible viscous flow around geometries rotating in uniform flow is analyzed. The linear local stability theory is used to investigate the boundary layer stability. Following the works of Briggs and Bers in the field of plasma physics, the absolute instability region is identified by singularities of dispersion relation called pinch - points. Calculations have been made for different Mach numbers and wall temperatures.

4

Free convection over a vertical rotating cone with constant wall heat flux

Kumari M., Pop I.

Applied Mechanics and Engineering

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1998

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Vol. 3, no 3

451-464

EN

This paper summarizes a numerical study of free convection flow over a vertical rotating cone in a quiescent fluid. A combined forced/free convection parameter is defined which allows the description of the entire regime from pure free convection to pure forced convection flow. The transformed equations are solved numerically for some values of the Prandtl number and the combined convection parameter using a very efficient finite-difference method. The effects of these parameters on the velocity and temperature fields as well as on the local skin friction and wall temperature distribution are illustrated. The results are compared with those from the literature. An excellent agreement is found.