Pressure Losses in Combining Subsonic Flows Through Branched Ducts

Abstract

An investigation of the “additional” total pressure losses occurring in combining flow through several sharp-edged three-leg junctions has been made. Experimental results covering a wide speed range up to choking are presented for three flow geometries of a lateral branch off a straight duct using dry air as the working fluid. A new theoretical flow model provided results in fairly good agreement with the experimental data obtained. Flow visualization of the high-speed flow using the Schlieren method revealed the presence of normal shock waves in the combined flow about one duct diameter downstream of the junction. The highest attainable Mach number (M3) of the averaged downstream (combined) flow was 0.66 for several of the flow geometries. This value of M3 appears to be the maximum possible and is the result of a combination of flow separation and local flow choking.

Fluid flow in an impacting symmetrical tee junction: I single‐phase flow and experimental

“…Empirical loss coefficient correlations were proposed which gave reasonable agreement with experimental values, particularly for high-inlet Reynolds numbers. Abou-Haidar and Dixon [3] pointed out that compressibility only affected prediction accuracy for Mach numbers greater than 0.2. Bassett et al .…”

New coefficient to characterize energy losses in compressible flow at T-junctions

“…2, the notation of the new linking coefficient for the studied flow configurations is shown. The loss coefficient defined by Miller was represented as a function of extrapolated Mach number in common branch at T-junctions with q = constant and for different angles between branches by Abou-Haidar and Dixon [32] and Abou-Haidar [33].…”

“…The only reliable data published in the open literature are the experimental data obtained for commercial T-and Y-junctions by Morimune et al [31] and the experimental investigations on Tand Y-junctions with different angles between branches accomplished by Abou-Haidar and Dixon [32]. In the first work, a graphical extrapolation procedure was used to subtract the friction losses and to obtain the extrapolated flow properties up to the junction departing from the measured static pressure at multiple locations in each branch.…”

“…Commercial codes have also been used by different authors: Shaw et al [25] and Gan and Riffat [26]. Finally, some approximate analytical expressions have been obtained assuming steady, incompressible and uniform flow hypothesis in Navier-Stokes equation system in integral form, Hager [27], Abou-Haidar and Dixon [28], Basset et al [29] and Winterbone and Pearson [30].…”

“…This methodology consists in carrying out numerical simulations of the 3D compressible fluid flow at T-junctions using the general purpose commercial code FLUENT™ [35] and processing the obtained numerical results applying the Fanno fluid flow model to subtract friction losses. The numerical results for different flow types and mass flow rate ratios between branches were compared with our own experimental data and also with the published Abou-Haidar and Dixon data [32]. For this purpose the total pressure loss coefficient defined by Miller [36] was used.…”