Compressible Fluid Flow through Narrow Channels

0549594 - ÚT 2022 CZ eng D - Thesis
Hála, Jindřich
Compressible Fluid Flow through Narrow Channels.
Ústav termomechaniky AV ČR, v. v. i. Defended: ČVUT. 17.09.2021. - Praha: ČVUT, 2021. 112 s.
Institutional support: RVO:61388998
Keywords : narrow channel flow * minichannel * compressible flow * wall shear stress * hot- lm anemometry
OECD category: Applied mechanics
https://dspace.cvut.cz/handle/10467/97592

The turbulence transition in pipe and channel flow represents up to now an important topic, since it is the nature of the flow, which substantially affects the friction and associated losses. With increasing miniaturization and more detailed numerical simulations of the various small flow parts of the turbomachines, the need for experimental data to explore the narrow channel flow phenomena and to validate numerical codes is still there. This thesis presents the results of the project which aimed to experimentally and numerically explore the compressible viscous flow in narrow channels of the rectangular cross-section of the high aspect ratio. Main objectives of this work were to explore the nature of the flow in such channels using a number of experimental methods including hot-film probe, explore the influence of two types of surface roughness and discuss the effects associated with the phenomenon of aerodynamic choking due to friction. Apart from the narrow channel measurements, the thesis contains also the detailed description of the calibration process of the hot-film probe and accompanying numerical study. It was observed that despite the channel length to channel height ratio ranging from 50 to 200, the flow was mostly transitional except the flow in the smallest channel of the height h = 0.5 mm. The effects of the surface roughness were explored using both qualitative and quantitative measurements by means of hot-film probe. The later provided distribution of the wall shear stress at five locations along the channel for two chosen regimes. Further, the analysis revealed inapplicability of the one-dimensional theory for the estimation of the friction factor. The theoretical analysis of the flow choking supported by numerical simulations shows that due to frictional losses, the actual choking is shifted towards the lower back pressure ratios. These findings were summarized in charts, which comprehensively illustrate derived relations.
Permanent Link: http://hdl.handle.net/11104/0327029