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Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.


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TL;DR: In this article, a coaxial jet originating from parallel coplanar pipe nozzles is computed by a compressible large eddy simulation (LES) using low-dissipation and low-dispersion schemes in order to determine its acoustic field and to study noise generation mechanisms.
Abstract: A coaxial jet originating from parallel coplanar pipe nozzles is computed by a compressible large eddy simulation (LES) using low-dissipation and low-dispersion schemes in order to determine its acoustic field and to study noise generation mechanisms. The jet streams are at high velocities, the primary stream is heated, and the Reynolds number based on the primary velocity and the secondary diameter is around 106. High levels of turbulence intensity are also specified at the nozzle exit. The jet aerodynamic field and the near-pressure field are both obtained directly from the LES. The far-field noise is calculated by solving the linear acoustic equations, from the unsteady LES data on a cylindrical surface surrounding the jet. A good agreement is observed in terms of directivity, levels, and narrow-band spectra with noise measurements carried out during the EU project CoJeN for a coaxial jet displaying same stream velocities and temperatures, coplanar nozzle outlets with identical area ratio, and a high Reynolds number. However, certainly due to differences in the properties of the nozzle-exit boundary layers with respect to the experiment, some unexpected peaks are noticed in the simulation spectra. They are attributed to the development of a Von Karman street in the inner mixing layer and to vortex pairings in the outer shear layer. High correlation levels are also calculated between the pressure waves radiated in the downstream direction and flow quantities such as axial velocity, vorticity norm, density, and temperature, taken around the end of the primary and secondary potential cores. Noise generation in the coaxial jet therefore appears significant around the end of the two potential cores. These flow regions are characterized by intermittency, a dominant Strouhal number, and variations in the convection velocity as similarly found in single jets. The use of density or temperature to compute flow-noise correlations finally seems appropriate for a heated jet flow, but might lead to correlations with acoustic disturbances in the potential core.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the results of flexible micro-pillars and pillar arrays were tested for wall shear stress measurements in flows with fluctuating wall-shear stress such as unsteady separated flows or turbulent flows.
Abstract: We present in this paper test results of flexible micro-pillars and pillar arrays for wall shear stress measurements in flows with fluctuating wall shear stress such as unsteady separated flows or turbulent flows. Previous papers reported on the sensing principle and fabrication process. Static calibrations have shown this sensor to have a maximum nonlinearity of 1% over two orders of wall-shear-stress. For measurements in flows with fluctuating wall shear stress the dynamic response has been experimentally verified in an oscillating pipe flow and compared to a calculated response based on Stokes’ and Oseen’s solution for unsteady flow around a cylinder. The results demonstrate good agreement under the given boundary conditions of cylindrical micro-pillars and the limit of viscous Stokes-flow around the pillar. Depending on the fluid and pillar geometry, different response curves result ranging from a flat low-pass filtered response to a strong resonant behavior. Two different methods are developed to detect the frequency content and the directional wall shear stress information from image processing of large sensor films with arrays of micro-pillars of different geometry. Design rules are given to achieve the optimal conditions with respect to signal-to-noise ratio, sensitivity and bandwidth for measurements in turbulent flows.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a numerical investigation of laminar periodic flow and heat transfer in a three-dimensional isothermal-wall square channel fitted with 45° inclined baffles on one channel wall is carried out.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a unified hydrodynamic model is developed for prediction of gas-liquid (co-current) pipe flow behavior based on slug dynamics, which is validated with extensive experimental data acquired with different pipe diameters, inclination angles, fluid physical properties, gas- liquid flow rates and flow patterns.
Abstract: In Zhang et al. [1], a unified hydrodynamic model is developed for prediction of gas-liquid (co-current) pipe flow behavior based on slug dynamics. In this study, the new model is validated with extensive experimental data acquired with different pipe diameters, inclination angles, fluid physical properties, gas-liquid flow rates and flow patterns. Good agreement is observed in every aspect of the two-phase pipe flow.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of varying strength of swirl on the Dean vortices as well as the interplay of swirling motion and Dean cells was examined through snapshot proper orthogonal decomposition (POD) with the aim to reveal the unsteady behaviour of the Dean Vortices under turbulent flow conditions, the so-called "swirl-switching" phenomenon.

81 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202335
202275
2021170
2020177
2019273
2018281