Separation flow characteristics upstream of finite crest length weir with a downstream ramp

The lateral jet interaction on a slender body in supersonic flow was investigated by numerical simulation. The spatial and surface flow characteristics induced by jet interaction were shown. As a result, when the lateral jet is not in the longitudinal symmetry plane, the jet interaction causes asymmetric separation flow of surface and space, and destroys the pressure distributions of the slender body. With different angle of attack and circumferential positions of jet, the flow characteristic of the after body for jet in asymmetry plane changes greatly. The results with and without jet interaction also show that the far-field interaction played a major role in the lateral jet interaction.

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Influence of Acoustic Disturbances on the Separation Flow Characteristics Behind Two Semi-Infinite Circular Cylinders

Separated Flows and Jets ◽

10.1007/978-3-642-84447-8_87 ◽

1991 ◽

pp. 719-722

Author(s):

S. P. Bardakhanov ◽

V. V. Larichkin

Keyword(s):

Flow Characteristics ◽

Circular Cylinders ◽

Separation Flow ◽

Acoustic Disturbances

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Experimental and Numerical Investigations on the Flow Characteristics within Hydrodynamic Entrance Regions in Microchannels

Micromachines ◽

10.3390/mi10050317 ◽

2019 ◽

Vol 10 (5) ◽

pp. 317 ◽

Cited By ~ 1

Author(s):

Haiwang Li ◽

Binghuan Huang ◽

Min Wu

Keyword(s):

Stokes Equations ◽

Flow Characteristics ◽

Simulated Data ◽

Working Fluid ◽

Separation Flow ◽

Entrance Length ◽

Number Range ◽

Numerical Investigations ◽

Micro Piv ◽

Strong Agreement

Flow characteristics within entrance regions in microchannels are important due to their effect on heat and mass transfer. However, relevant research is limited and some conclusions are controversial. In order to reveal flow characteristics within entrance regions and to provide empiric correlation estimating hydrodynamic entrance length, experimental and numerical investigations were conducted in microchannels with square cross-sections. The inlet configuration was elaborately designed in a more common pattern for microdevices to diminish errors caused by separation flow near the inlet and fabrication faults so that conclusions which were more applicable to microchannels could be drawn. Three different microchannels with hydraulic diameters of 100 μm, 150 μm, and 200 μm were investigated with Reynolds (Re) number ranging from 0.5 to 50. For the experiment, deionized water was chosen as the working fluid and microscopic particle image velocimetry (micro-PIV) was adopted to record and analyze velocity profiles. For numerical simulation, the test-sections were modeled and incompressible laminar Navier–Stokes equations were solved with commercial software. Strong agreement was achieved between the experimental data and the simulated data. According to the results of both the experiments and the simulations, new correlations were proposed to estimate entrance length. Re numbers ranging from 12.5 to 15 was considered as the transition region where the relationship between entrance length and Re number converted. For the microchannels and the Reynolds number range investigated compared with correlations for conventional channels, noticeable deviation was observed for lower Re numbers (Re < 12.5) and strong agreement was found for higher Re numbers (Re > 15).

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Numerical Resolution of Compressor Corner Separation Problem

Volume 2C: Turbomachinery ◽

10.1115/gt2020-14587 ◽

2020 ◽

Author(s):

Wei Sun ◽

Zhong-Nan Wang ◽

Liping Xu

Keyword(s):

Large Scale ◽

Flow Characteristics ◽

Separation Flow ◽

Compressor Cascade ◽

Corner Separation ◽

Numerical Resolution ◽

Turbulence Closures ◽

Rans Models ◽

Generation Mechanisms ◽

Blending Function

Abstract Corner separation is a common flow phenomenon within compressors that can significantly affect the compressor performance. The RANS turbulence closures, commonly used in the industrial CFD simulations, often struggle to predict corner separation with reasonable accuracy. In this paper, the results of two RANS-based modelling approaches are presented for the corner separation within a high-loaded Prescribed Velocity Distribution (PVD) compressor cascade. The flow characteristics are studied to facilitate understanding the causes of varying performance of RANS models. It is observed that mixing plays a crucial role in accurately predicting the type, location, and size of flow separation. The source terms that control the turbulence mixing in SA and SST models are identified, based on physical analyses. Both RANS models are modified to better model the mixing process. Based on the modified SST model, an improved RANS-LES blending function has been proposed for a hybrid RANS-LES model. This new blending function ensures reliable shielding of attached boundary layers by the RANS portion of the hybrid model. Finally, to gain further understanding of the endwall flow physics, the turbulence characteristics of the resolved corner separation flow are studied, in terms of the large-scale unsteadiness and loss generation mechanisms.

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