scholarly journals Experimental Analysis of Pressure Drop and Laminar to Turbulent Transition for Gas Flows in Smooth Microtubes

2007 ◽  
Vol 28 (8-9) ◽  
pp. 670-679 ◽  
Author(s):  
Gian Luca Morini ◽  
Marco Lorenzini ◽  
Stéphane Colin ◽  
Sandrine Geoffroy
2008 ◽  
Vol 7 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Gian Luca Morini ◽  
Marco Lorenzini ◽  
Sandro Salvigni ◽  
Marco Spiga

Author(s):  
Sandrine Geoffroy ◽  
Ste´phane Colin ◽  
Marco Lorenzini ◽  
Gian Luca Morini

Reviews of the experimental results related to the laminar-to-turbulent transition in microchannels have appeared in the last years in the literature. These studies indicate that the transition from the laminar to the turbulent flow in micro-scale passages has been experienced at critical Reynolds numbers ranging from 70 up to 10000. In this work the characteristics of the laminar-to-turbulent transition for gases flowing through commercial Peek microtubes used for gas-chromatography columns are experimentally investigated. The microtubes tested are characterized by an internal diameter ranging between 300 μm and 100 μm with a L/Dh ratio in the range between 167 to 4000. Since the absolute roughness of the microtubes tested was very low (less than 0.05 μm) it is possible to uncouple the effects of the roughness on the laminar-to-turbulent transition. In the paper the effects of the gas compressibility and of the L/Dh ratio on the critical Reynolds number for which the laminar-to-turbulent transition takes place will be analyzed and discussed by comparing the experimental results with the other data published in the literature.


2021 ◽  
Vol 33 (6) ◽  
pp. 065128
Author(s):  
Hamid Hassan Khan ◽  
Syed Fahad Anwer ◽  
Nadeem Hasan ◽  
Sanjeev Sanghi

2004 ◽  
Vol 30 (4) ◽  
pp. 509-514 ◽  
Author(s):  
Hideki TOKANAI ◽  
Eiji HARADA ◽  
Jun-ichi HASEGAWA ◽  
Masafumi KURIYAMA

2016 ◽  
Vol 120 (1225) ◽  
pp. 473-493 ◽  
Author(s):  
A. Koreanschi ◽  
O. Sugar-Gabor ◽  
R. M. Botez

ABSTRACTThe drag coefficient and the laminar-to-turbulent transition for the aerofoil component of a wing model are optimised using an adaptive upper surface with two actuation points. The effects of the new shaped aerofoils on the global drag coefficient of the wing model are also studied. The aerofoil was optimised with an ‘in-house’ genetic algorithm program coupled with a cubic spline aerofoil shape reconstruction and XFoil 6.96 open-source aerodynamic solver. The wing model analysis was performed with the open-source solver XFLR5 and the 3D Panel Method was used for the aerodynamic calculation. The results of the aerofoil optimisation indicate improvements of both the drag coefficient and transition delay of 2% to 4%. These improvements in the aerofoil characteristics affect the global drag of the wing model, reducing it by up to 2%. The analyses were conducted for a single Reynolds number and speed over a range of angles of attack. The same cases will also be used in the experimental testing of the manufactured morphing wing model.


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