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Exploring the Role of the Inlet Machining Angle on the Pressure and Flow Characteristics of Microchannels under Slip Flow Conditions
Ayhan Nazmi İlikan Ayhan Nazmi İlikana
aChief Researcher, Alternative Energy Technologies Department, TUBITAK RUTE, Gebze, Kocaeli, Türkiye
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Abstract:
This study numerically investigates how machining inlet angles affect the pressure drop and hydrodynamic entrance length in microchannels. Two-dimensional CFD simulations were performed under steady conditions with Reynolds (Re) numbers ranging from 1-100 and Knudsen (Kn) numbers of 0.001, 0.01, and 0.1 within the slip flow regime. Air was used as the working fluid, and the Navier‒Stokes equations were solved with Maxwell slip boundary conditions. The results show that at constant inlet machining angles and Re values, the pressure drop increased by up to 75% as Kn decreased from 0.1 to 0.001. For all Kn values, the pressure loss increased by an average of 3% at a 15° angle, 10% at 30°, and 25% at 45° compared with that of a straight channel. As Re increased, these values escalated further. The findings suggest that pressure loss tends to increase significantly for inlet angles above 30°, particularly at higher Reynolds numbers; therefore, keeping the angle below this value may be beneficial. Additionally, the entrance length increased with both Re and Kn, with the inlet machining angle affecting it only when the channel length matched the diameter at Re 1 or was 7-8 times the diameter at Re 100. No substantial effect was observed for longer channels. The results aligned well with the literature, supporting the conclusions of the present study.
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Keywords: microchannel, slip flow, CFD, machining
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©
2026
CSME , ISSN 0257-9731
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