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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 : M. Piller
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (742 download)
Download or read book Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Square Duct at Low Reynolds Number written by M. Piller and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, we present the results from Direct Numerical Simulations of turbulent, incompressible flow through a square duct, with an imposed temperature difference between two opposite walls, while the other two walls are assumed perfectly insulated. The mean flow is sustained by an imposed, mean pressure gradient. The most interesting feature, characterizing this geometry, consists in the presence of turbulence-sustained mean secondary motions in the cross-flow plane. In this study, we focus on weak turbulence, in that the Reynolds number, based on bulk velocity and hydraulic diameter, is about 4450. Our results indicate that secondary motions do not affect dramatically the global parameters, like friction factor and Nusselt number, in comparison with the plane-channel flow. This issue is investigated by looking at the distribution of the various contributions to the total heat flux, with particular attention to the mean convective term, which does not appear in the plane channel flow.
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 : Bayode Owolabi
Publisher : Springer
ISBN 13 : 303019745X
Total Pages : 141 pages
Book Rating : 4.0/5 (31 download)
Download or read book Characterisation of Turbulent Duct Flows written by Bayode Owolabi and published by Springer. This book was released on 2019-05-31 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents several new findings in the field of turbulent duct flows, which are important for a range of industrial applications. It presents both high-quality experiments and cutting-edge numerical simulations, providing a level of insight and rigour rarely found in PhD theses. The scientific advancements concern the effect of the Earth’s rotation on large duct flows, the experimental confirmation of marginal turbulence in a pressure-driven square duct flow (previously only predicted in simulations), the identification of similar marginal turbulence in wall-driven flows using simulations (for the first time by any means) and, on a separate but related topic, a comprehensive experimental study on the phenomenon of drag reduction via polymer additives in turbulent duct flows. In turn, the work on drag reduction resulted in a correlation that provides a quantitative prediction of drag reduction based on a single, measurable material property of the polymer solution, regardless of the flow geometry or concentration. The first correlation of its kind, it represents an important advancement from both a scientific and practical perspective.
Author : Peter R. Voke
Publisher : Springer Science & Business Media
ISBN 13 : 9780792331063
Total Pages : 454 pages
Book Rating : 4.3/5 (31 download)
Download or read book Direct and Large-Eddy Simulation I written by Peter R. Voke and published by Springer Science & Business Media. This book was released on 1994-10-31 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.
Author : Gaurav Sharma
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (711 download)
Download or read book Direct Numerical Simulation of Particle-laden Turbulence in a Straight Square Duct written by Gaurav Sharma and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle-laden turbulent flow through a straight square duct at Re[subscript tau]= 300 is studied using direct numerical simulation (DNS) and Lagrangian particle tracking. A parallelized 3-D particle tracking direct numerical simulation code has been developed to perform the large-scale turbulent particle transport computations reported in this thesis. The DNS code is validated after demonstrating good agreement with the published DNS results for the same flow and Reynolds number. Lagrangian particle transport computations are carried out using a large ensemble of passive tracers and finite-inertia particles and the assumption of one-way fluid-particle coupling. Using four different types of initial particle distributions, Lagrangian particle dispersion, concentration and deposition are studied in the turbulent straight square duct. Particles are released in a uniform distribution on a cross-sectional plane at the duct inlet, released as particle pairs in the core region of the duct, distributed randomly in the domain or distributed uniformly in planes at certain heights above the walls. One- and two-particle dispersion statistics are computed and discussed for the low Reynolds number inhomogeneous turbulence present in a straight square duct. New detailed statistics on particle number concentration and deposition are also obtained and discussed.
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 : 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:
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 : Roger Peyret
Publisher : Springer
ISBN 13 : 3709125901
Total Pages : 320 pages
Book Rating : 4.7/5 (91 download)
Download or read book Advanced Turbulent Flow Computations written by Roger Peyret and published by Springer. This book was released on 2014-05-04 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects the lecture notes concerning the IUTAM School on Advanced Turbulent Flow Computations held at CISM in Udine September 7–11, 1998. The course was intended for scientists, engineers and post-graduate students interested in the application of advanced numerical techniques for simulating turbulent flows. The topic comprises two closely connected main subjects: modelling and computation, mesh pionts necessary to simulate complex turbulent flow.
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 : Asmund Huser
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Direct Simulation of Turbulent Flow in a Square Duct written by Asmund Huser and published by . This book was released on 1994 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 : 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 : Ravi Kumar Madabhushi
Publisher :
ISBN 13 :
Total Pages : 436 pages
Book Rating : 4.:/5 (292 download)
Download or read book Direct and Large-eddy Simulations of Turbulent Flow in a Square Duct written by Ravi Kumar Madabhushi and published by . This book was released on 1993 with total page 436 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 : 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.
