The Effect of Sinusoidally Changing Magnetic Field Strength on Flow Separation and Heat Transfer in Backward-Facing Step Geometry

Öz

Flow separation is a physical phenomenon that greatly affects the performance in aerodynamic and heat transfer applications and cannot be neglected during design. Backward-facing step is the reference geometry, which is important in the studies carried out to examine the flow separation or to investigate the effectiveness of control methods aimed at manipulating the separated flow. In this study, the effect of the magnetic field, which is an active flow control method, on flow separation in backward-facing step geometry and heat transfer were investigated numerically. The intensity of the magnetic field was changed continuously, depending on a sinusoidal function over time. The investigation was limited to laminer flow conditions. Water based iron oxide (Fe3O4 – water) nanofluid was used as a working fluid and the nanofluid modeled as a single phase. As a result of numerical simulations, the method examined has been found to be successful in influencing the wake flow and the convective heat transfer caused by the flow in this zone.

Anahtar Kelimeler

• Backward-facing step
• Flow control methods
• Flow seperation
• Heat transfer
• Magnetohydrodynamics

Zamanla Sinüzoidal Olarak Değişen Manyetik Alan Şiddetinin Ters Basamak Geometrisinde Akış Ayrılması ve Isı Transferine Etkisi

Öz

Akış ayrılması, aerodinamik ve ısı transferi uygulamalarında performansı büyük ölçüde etkileyen, tasarım sırasında göz ardı edilemeyecek fiziksel bir olgudur. Ters basamak geometrisi, akış ayrılmasını incelemek veya ayrılmış akışı manipüle etmeyi hedefleyen kontrol yöntemlerinin etkinliğini araştırmak amacıyla gerçekleştirilen çalışmalarda önemli bir yere sahip referans geometridir. Bu çalışmada bir aktif akış kontrol yöntemi olan manyetik alanın ters basamak geometrisinde akış ayrılması ve ısı transferine etkisi sayısal olarak incelenmiştir. Manyetik alanın şiddeti zamana göre sinüzoidal bir fonksiyona bağlı kalarak sürekli şekilde değiştirilmiştir. İnceleme laminer akış koşulları ile sınırlandırılmıştır. Çalışma sıvısı olarak su bazlı demir oksit (Fe3O4-su) nano akışkanı kullanılmış ve nano akışkan tek fazlı olarak modellenmiştir. Sayısal simülasyonlar sonucunda incelenen yöntemin ölü akış bölgesine ve bu bölgedeki akışın sebep olduğu konveksiyon ile ısı transferine etki etmede başarılı olduğu görülmüştür.

Anahtar Kelimeler

• Akış kontrol yöntemleri
• Akış ayrılması
• Isı transferi
• Manyetohidrodinamik
• Ters basamak geometrisi

Kaynakça

1. 1. Kim, J., Kline, S.J., Johnston, J.P., 1980. Investigation of a Reattaching Turbulent Shear Layer: Flow Over a Backward-facing Step. 302-308.
2. 2. Armaly, B.F., Dursts, F., Pereira, J.C.F., Schonung, B., 1983. Experimental and Theoretical Investigation of Backward-facing Step Flow. Journal of Fluid Mechanics 127, 473-496.
3. 3. Adams, E.W., Eaton, J.K., 1988. An LDA Study of the Backward-facing Step Flow, Including the Effects of Velocity Bias, 275-282.
4. 4. Chun, K.B., Sung, H.J., 1996. Control of Turbulent Separated Flow Over a Backward- facing Step by Local Forcing, Experiments in Fluids, 21, 417-426.
5. 5. Tsay, Y.L., Chang, T.S., Cheng, J.C., 2005. Heat Transfer Enhancement of Backward- facing Step Flow in a Channel by Using Baffle Installation on the Channel Wall, Acta Mechanica, 174, 63-76.
6. 6. Nie, Jian H., Chen, Y.T., Hsieh, H.T., 2009. Effects of a Baffle on Separated Convection Flow Adjacent to Backward-facing Step. International Journal of Thermal Sciences 48, 618-625.
7. 7. Mohammed, Omer, H.A., Alawi, A., Wahid, M.A., 2015. Mixed Convective Nanofluid Flow in a Channel Having Backward-facing Step with a Baffle, Powder Technology, 275, 329-343.
8. 8. Selimefendigil, F., Öztop, H.F., 2013. Numerical Analysis of Laminer Pulsating Flow at a Backward Facing Step with an Upper Wall Mounted Adiabatic Thin Fin, Computers & Fluids 88, 93-107.

9. 9. Cheng, J.C., Tsay, Y.L., 2006. Effects of Solid and Slotted Baffles on the Convection Characteristics of Backward-facing Step Flow in a Channel, Heat and Mass Transfer, 42(9), 843-852.
10. 10. Václav, U., Jonáš, P., Mazur, O., 2007. Control of a Channel-flow Behind a Backward-facing Step by Suction/blowing, International Journal of Heat and Fluid Flow 28(4), 665-672.
11. 11. Velazquez, A., Arias, J.R., Mendez, B., 2008. Laminer Heat Transfer Enhancement Downstream of a Backward Facing Step by Using a Pulsating Flow, International Journal of Heat and Mass Transfer, 51(7-8), 2075-2089.
12. 12. Valencia, A., Hinojosa, L., 1997. Numerical Solutions of Pulsating Flow and Heat Transfer Characteristics in a Channel with a Backward- Facing Step, Heat and Mass Transfer, 32(3), 143-148.
13. 13. Khanafer, K., Al-Azmi, B., Al-Shammari, A., Pop, L., 2008. Mixed Convection Analysis of Laminer Pulsating Flow and Heat Transfer Over a Backward-facing Step, International Journal of Heat and Mass Transfer 51(25-26), 5785-5793.
14. 14. Tihon, J., Pěnkavová, V., Pantzali, M., 2010. The Effect of Inlet Pulsations on the Backward-facing Step Flow, European Journal of Mechanics-B/Fluids, 29(3), 224-235.
15. 15. Selimefendigil, F., Öztop, H.F., 2017. Forced Convection and Thermal Predictions of Pulsating Nanofluid Flow Over a Backward Facing Step with a Corrugated Bottom Wall, International Journal of Heat and Mass Transfer, 110, 231-247.
16. 16. Abbassi, H., Ben Nassrallah, S., 2007. MHD Flow and Heat Transfer in a Backward-facing Step, International Communications in Heat and Mass Transfer, 34(2), 231-237.
17. 17. Selimefendigil, F., Öztop, H.F., 2015. Influence of Inclination Angle of Magnetic Field on Mixed Convection of Nanofluid Flow Over a Backward Facing Step and Entropy Generation, Advanced Powder Technology 26(6), 1663-1675.
18. 18. Kumar, A., Amit K.D., 2012. Effect of a Circular Cylinder on Separated Forced Convection at a Backward-facing Step, International Journal of Thermal Sciences, 52, 176-185.
19. 19. Suzuki, H., Kida, S., Nakamae, T., Suzuki, K., 1991. Flow and Heat Transfer Over a Backward-facing Step with a Cylinder Mounted Near its Top Corner, International Journal of Heat and Fluid Flow 12(4), 353-359.
20. 20. Selimefendigil, F., Öztop, H.F., 2015. Numerical Investigation and Reduced Order Model of Mixed Convection at a Backward Facing Step with a Rotating Cylinder Subjected to Nanofluid, Computers & Fluids 109, 27-37.
21. 21. Selimefendigil, F., Öztop, H.F., 2014. Effect of a Rotating Cylinder in Forced Convection of Ferrofluid Over a Backward Facing Step, International Journal of Heat and Mass Transfer, 71, 142-148.
22. 22. Edward, C., Lien, F.S., 2005. Permeability Effects of Turbulent Flow Through a Porous Insert in a Backward-facing-step Channel, Transport in Porous Media, 59(1), 47-71.
23. 23. Benard, N., Sujar Garrido, P., Bonnet, J.P., Moreau, E., 2016. Control of the Coherent Structure Dynamics Downstream of a Backward Facing Step by DBD Plasma Actuator, International Journal of Heat and Fluid Flow, 61, 158-173.
24. 24. Ruisi, R., Zare-Behtash, H., Kontis, K., Erfani, R., 2016. Active Flow Control Over a Backward-facing Step Using Plasma Actuation, Acta Astronautica, 126, 354-363.
25. 25. Garrido, P.S., Benard, N., Moreau, E., Bonnet, J.P., 2015. Dielectric Barrier Discharge Plasma Actuator to Control Turbulent Flow Downstream of a Backward-facing Step, Experiments in Fluids, 56(4), 70.
26. 26. Gholamhosein, P.S., Mirzaei, M., Hajipour, M., 2015. Experimental Study of Separation Bubble Control Behind a Backward-facing step Using Plasma Actuators, Acta Mechanica 226(4), 1153-1165.
27. 27. D'Adamo, J., Roberto, S., Artana, G., 2014. Active Control of a Backward Facing Step Flow with Plasma Actuators, Journal of Fluids Engineering, 136(12).
28. 28. Kyoji, I., Nakamura, K., Senda, M., 2004. Heat Transfer Control of a Backward-facing Step Flow in a Duct by Means of Miniature Electromagnetic Actuators, International Journal of Heat and Fluid Flow, 25(5), 711- 720.
29. 29. Brinkman, H.C., 1952. The Viscosity of Concentrated Suspensions and Solutions, J. Chem. Phys. 20, 571.
30. 30. Society, T.R., Transactions, P., Society, R., Papers, C., Character, P., 1904. XII. Colours in Metal Glasses and in Metallic Films, Philos. Trans. R. Soc. London. Ser. A, Contain. Pap. a Math. or Phys. Character, 203, 385-420.
31. 31. Sheikholeslami, M., Gorji-Bandpay, M., Ganji, D.D., 2012. Magnetic Field Effects on Natural Convection Around a Horizontal Circular Cylinder Inside a Square Enclosure Filled with Nanofluid, Int. Commun. Heat Mass Transf. 39, 978–986.