Local resistance of fluid flow across sudden contraction in small channels

Abstract

The pressure drop caused by flow area contraction in microchannels has been experimentally studied in this paper using the tiny gap pressure measurement method. The working fluid was deionized water at room temperature at near-atmospheric pressure. Three test sections with area ratios of 0.284 and 0.274 and at different tube diameter sizes were used. The experimental results show that the abrupt contraction coefficient K c decreases with the Reynolds number increasing, and it is much higher than that of conventional tubes in laminar flow. The widely-applied correlation K c = 0.5(1 -σ) 0.75 could not predict the contraction coefficient of turbulent flow in the micro tubes. The K c decreases as the tube diameter increases. The transition from laminar to turbulent flow is not obvious when the diameter of the small tube is 0.32 mm.

Pore-network modelling of non-Darcy flow through heterogeneous porous media

“…It has been found that using kd and α equal to 1.0 provides better representation of the non-Darcy flow which is characterised by higher velocities compared to the Darcy flow. This also agrees with the experimental findings of Abdelall et al (2005) and Guo et al (2010) performed on small channels. They showed that when using kd = 1.33 or α = 2.0 in equations 10 and 11, this result in overestimation of Ke and Kc in most of the cases they tested.…”

“…To consider the inertial effects due to expansion, when flow moves from a pore throat to a connected pore body, and contraction, when flow moves from a pore body to a connected pore throat, the pressure loss due to these two processes should be considered in the calculation of total pressure drop through any pore throat. In the developed model, the pressure losses due to the inertial effects, expansion and contraction, are expressed using equations 10 and 11 (Kays, 1950;Abdelall et al, 2005;Guo et al, 2010;Momen et al, 2016).…”

Gravity‐driven flow control in a fully integrated microfluidic cartridge for molecular point‐of‐care testing

“…When liquid flows into a standard microfluidic chamber, a sudden contraction at the chamber outlet can create a bottleneck effect known as "necking" along the lower sidewall [42]. This localized resistance can significantly affect flow control accuracy.…”

Turbulent Flow Pressure Losses in Gasoline Particulate Filters

“…Moreover, the supporting experiments have been performed for circular and triangular tube geometries only, while the theoretical expressions vary considerably with the shape of the channels and between single and multiple channel configurations. Some experimental work has been performed more recently on mini-and micro-channels, but results of these are also inconclusive ( [46], [47], [48]). Therefore, it appears that no reliable, validated data exists for laminar contraction losses in square ducts and duct arrays.…”