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Download or read book Direct Numerical Simulation of Turbulent Flow Over Wide‐rib Rectangular Grooves written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Seyyed Vahid Mahmoodi Jezeh
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Square Duct Roughened with Transverse Or V-shaped Ribs written by Seyyed Vahid Mahmoodi Jezeh and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This integrated thesis documents a series of complementary numerical investigations aimed at an improved understanding of turbulent flows and heat transfer in a square duct with ribs of different shapes mounted on one wall. Direct numerical simulation (DNS) is used to accurately resolve the spatial and temporal scales of the simulated flows. The first DNS investigates the turbulent flow in a ribbed square duct of different blockage ratios. The results are compared with those of a smooth duct flow. It is observed that an augmentation of the blockage ratio concurrently generates stronger turbulent secondary flow motions, which drastically alter the turbulent transport processes between the sidewall and duct center, giving rise to high-degrees of non-equilibrium states. The dynamics of coherent structures are studied by examining characteristics of the instantaneous velocity field, swirling strength, spatial two-point auto-correlations, and velocity spectra. The impact of the blockage ratio on the turbulent heat transfer is investigated in the second numerical study. The results show that owing to the existence of the ribs and confinement of the duct, organized secondary flows appear as large streamwise-elongated vortices, which have profound influences on the transport of momentum and thermal energy. This study also shows that the spatial distribution and magnitude of the drag and heat transfer coefficients are highly sensitive to the rib height. The final study focuses on a comparison of highly-disturbed turbulent flows in a square duct with inclined and V-shaped ribs mounted on one wall. The turbulence field is highly sensitive to not only the rib geometry but also the boundary layers developed over the side and top walls. Owing to the difference in the pattern of the cross-stream secondary flow motions of these two ribbed duct cases, the flow physics in the inclined rib case is significantly different from the V-shaped rib case. It is found that near the leeward and windward faces of the ribs, the mean inclination angle of turbulence structures in the V-shaped rib case is greater than that of the inclined rib case, which subsequently enhances momentum transport between the ribbed bottom wall and the smooth top wall.
Author : Stanford University. Thermosciences Division. Thermosciences Division
Publisher :
ISBN 13 :
Total Pages : 250 pages
Book Rating : 4.F/5 ( download)
Download or read book Direct Numerical Simulation of Turbulent Flow Over a Backward-facing Step written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1994 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Michal Andrzej Kopera
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (824 download)
Download or read book Direct Numerical Simulation of Turbulent Flow Over a Backward-facing Step written by Michal Andrzej Kopera and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-dimensional, turbulent flow in a channel with a sudden expansion was studied by direct numerical simulation of the incompressible Navier-Stokes equations. The objective of this study was to provide statistical data of backwardfacing step flow for turbulence modelling. Additionally, analysis of the statistical and dynamical properties of the flow is performed. The Reynolds number of the main simulation was Reh = 9000, based on the step height and mean inlet velocity, with the expansion ratio ER = 2:0. The discretisation is performed using the spectral/hp element method with stiffly-stable velocity correction scheme for time integration. The inlet boundary condition is a fully turbulent velocity and pressure field regenerated from a plane downstream of the inlet. A constant flowrate was ensured by applying Stokes flow correction in the inlet regeneration area. Time and spanwise averaged results revealed, apart from the primary recirculation bubble, secondary and tertiary corner eddies. Streamlines show an additional small eddy at the downstream tip of the secondary corner eddy, with the same circulation direction as the secondary vortex. The analysis of the 3D, timeonly average shows the wavy spanwise structure of both primary and secondary recirculation bubble, that results in spanwise variations of the mean reattachment location. The visualisation of spanwise averaged pressure uctuations and streamwise velocity showed that the interaction of vortices with the recirculation bubble is responsible for the apping of the reattachment position. The characteristic frequency St = 0:078 was found. The analysis of small-scale energy transfer was performed to reveal large backscatter regions in strong Reynolds stress areas in the mixing layer. High correlation of small-scale transfer with non-linear interaction of large-scale velocity and small-scale vorticity was found. The data of the flow fields was archived. It contains the averages for velocities, pressure and Reynolds stress tensor, as well as 3D instantaneous pressure and velocity history.
Author : Asmund Huser
Publisher :
ISBN 13 :
Total Pages : 462 pages
Book Rating : 4.:/5 (324 download)
Download or read book Direct Numerical Simulation of Turbulent Flow in a Square Duct written by Asmund Huser and published by . This book was released on 1992 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jiaxin Yan
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Direct Numerical Simulation of Turbulent Flows in a Rectangular Duct of Different Aspect Ratios written by Jiaxin Yan and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct numerical simulations are performed to investigate turbulent flows in a rectangular duct of aspect ratio varying from 1.0 to 3.0 at a fixed low Reynolds number 150. Persistent secondary flows of Prandtl's second kind are observed in the corners of the ducts. As the aspect ratio increases, streamwise vortices near the top and bottom walls extend towards to the central vertical plane of ducts. Particularly, the displacement of vortex cores near the top/bottom wall can be described as a function of the distance to the sidewall. Detailed analyses of turbulence statistics including the mean flow, turbulent kinetic energy, turbulent intensities, Reynolds stress budgets, and pre-multiplied one-dimensional energy spectrum are conducted to understand the aspect ratio effects on the flow physics. In the duct of aspect ratio 3.0, hairpin flow structures are present in the central regions of the duct, and their characteristics are similar to those exhibited in the plane channel flows. Furthermore, as indicated by the energy spectra, a spanwise quasi-homogeneous region spans over approximately 270 wall units in the central region of the rectangular duct.
Author : Douglas C. Chu
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (252 download)
Download or read book A Direct Numerical Simulation of Laminar and Turbulent Flow Over Streamwise Aligned Riblets written by Douglas C. Chu and published by . This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Ravindranath Lanka
Publisher :
ISBN 13 :
Total Pages : 260 pages
Book Rating : 4.:/5 (451 download)
Download or read book Direct Numerical Simulation of Turbulent Flow in a Curved Channel written by Ravindranath Lanka and published by . This book was released on 2000 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jukka Komminaho
Publisher :
ISBN 13 :
Total Pages : 196 pages
Book Rating : 4.:/5 (185 download)
Download or read book Direct Numerical Simulation of Turbulent Flow in Plane and Cylindrical Geometries written by Jukka Komminaho and published by . This book was released on 2000 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Rafael Hurtado Rosas
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Direct Numerical Simulation of Turbulent Flow and Heat Transfer Within a Spanwise-rotating Elliptical Pipe written by Rafael Hurtado Rosas and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Henry Andrew Carlson
Publisher :
ISBN 13 :
Total Pages : 518 pages
Book Rating : 4.E/5 ( download)
Download or read book Direct Numerical Simulation of Laminar and Turbulent Flow in a Channel with Complex, Time-dependent Wall Geometries written by Henry Andrew Carlson and published by . This book was released on 1995 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jony Castagna
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Direct Numerical Simulation of Turbulent Flows Over Complex Geometries written by Jony Castagna and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Zhao-Ping Zhang
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Direct Numerical Simulation of Turbulent Flow in a Circular Pipe Subjected to Radial System Rotation written by Zhao-Ping Zhang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, direct numerical simulations have been preformed with a high-order spectral element method computer code to investigate the Coriolis force effect on a fully-developed turbulent flow confined within a circular pipe subjected to radial system rotations. In order to study the radially rotating effects on the flow, a wide range of rotation numbers have been tested. In response to the system rotation imposed, large-scale secondary flows appear as streamwise counter-rotating vortices, which highly interact with the boundary layer and have a significant impact on the turbulent flow structures and dynamics. A quasi Taylor-Proudman region occurs at low rotation numbers, where the mean axial velocity is invariant along the rotating axis. As the rotation number increases, laminarization occurs near the bottom wall of the pipe, and the flow become fully laminarized when the rotation number approaches one. The characteristics of the flow field are investigated in both physical and spectral spaces, which include the analyses of the first- and second-order statistical moments, pre-multiplied spectra of velocity fluctuations, budget balance of the transport equation of Reynolds stresses, and coherent flow structures.
Author : Edris Bagheri
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)
Download or read book Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Concentric Annular Pipe written by Edris Bagheri and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the effects of computational domain size and radius ratio on fully developed turbulent flow and heat transfer in a concentric annular pipe are investigated using direct numerical simulation (DNS). To perform DNS, a new parallel computer code based on the pseudo-spectral method was developed using the FORTRAN 90/95 programing languages and the message passing interface (MPI) libraries. In order to study the effects of computational domain size on the turbulence statistics, twelve test cases of different domain sizes are compared. The effects of radius ratio are investigated through a systematic study based on four radius ratios of a concentric pipe. The characteristics of the velocity and temperature fields are examined at two Reynolds number of Re_(D_h ) =8900$ and 17700. The radius ratio affects the interaction of two boundary layers of the concentric annular pipe and has a significant impact on the turbulent flow structures and dynamics. The characteristics of the flow and temperature fields are investigated in both physical and spectral spaces, which include the analyses of the first- and second-order statistical moments, budget balance of the transport equation of Reynolds stresses, two-point correlation coefficients, and premultiplied spectra of velocity, vorticity, and temperature fluctuations. It is observed that the scales and dynamics of turbulence structures vary with the radius ratio as well as the surface curvature of the concave and convex walls. The characteristic length scales of the turbulence structures are identified through a spectral analysis.
Author : Alvaro Vidal Torreira
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (112 download)
Download or read book Direct Numerical Simulation of Turbulent Wall-bounded Flows in Moderately Complex Geometries written by Alvaro Vidal Torreira and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Robert deLancey Moser
Publisher :
ISBN 13 :
Total Pages : 192 pages
Book Rating : 4.F/5 ( download)
Download or read book Direct Numerical Simulation of Curved Turbulent Channel Flow written by Robert deLancey Moser and published by . This book was released on 1984 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Patrick Loulou
Publisher :
ISBN 13 :
Total Pages : 196 pages
Book Rating : 4.F/5 ( download)
Download or read book Direct Numerical Simulation of Incompressible Pipe Flow Using a B-spline Spectral Method written by Patrick Loulou and published by . This book was released on 1996 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
