Numerical study of Dean vortices in developing Newtonian and viscoelastic flows through a curved duct of square cross-section

2009 ◽  
Vol 337 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Mohammed Boutabaa ◽  
Lionel Helin ◽  
Gilmar Mompean ◽  
Laurent Thais
Keyword(s):  
Cross Section ◽  
Numerical Study ◽  
Viscoelastic Flows ◽  
Dean Vortices ◽  
Curved Duct

3D Simulation of Dean Vortices at 30° Position of 180° Curved Duct of Square Cross-Section under Opposing Buoyancy

2018 ◽  
Vol 389 ◽  
pp. 153-163 ◽  
Author(s):  
Mourad Mokeddem ◽  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Cross Section ◽  
Richardson Number ◽  
Three Dimensions ◽  
Governing Equations ◽  
Dean Number ◽  
Thermal Buoyancy ◽  
Dean Vortices ◽  
Flow And Heat Transfer ◽  
Curved Duct ◽  
Physical Phenomena

3D numerical simulations are performed to analyze correctly the effect of opposing thermal buoyancy and Dean number on Dean vortices, fluid flow and heat transfer through 180° curved duct of square cross-section. Due to tremendous found results, this works emphasizes only at the position 30° of the bend portion. The governing equations involving momentum, continuity and energy are solved in three dimensions under these assumptions: the flow is laminar, steady-state and incompressible. The present study is investigated in the range of these conditions: Dean number of De = 125 to 150, Richardson number of Ri = 0 to 2 at Pr = 1. The principal obtained results are represented in forms of streamlines and isotherms to analyze and to discuss the found physical phenomena. The local Nusselt number along the wall of square cross-section is also computed and presented. The main found point is that the opposing thermal buoyancy has a tendency to eliminate the effect of centrifugal force at the position 30° of bend portion of 180° curved duct.

Secondary instability of flow in a curved duct of square cross-section

1996 ◽  
Vol 323 ◽  
pp. 387-409 ◽  
Author(s):  
Philip A. J. Mees ◽  
K. Nandakumar ◽  
J. H. Masliyah
Keyword(s):  
Cross Section ◽  
Travelling Waves ◽  
Outer Wall ◽  
Travelling Wave ◽  
Shear Instability ◽  
Radius Of Curvature ◽  
Duct Flow ◽  
Wave State ◽  
Dean Vortices ◽  
Curved Duct

Experiments and simulations of a travelling wave state of incompressible Newtonian flow in a curved duct of square cross-section are presented. The travelling wave mode develops from the well-documented steady four-cell flow state and is characterized by oscillations of the two Dean vortices near the centre of the outer wall.The oscillations were induced by a carefully positioned pin at 5° from the inlet of the curved section along the symmetry line of the cross-section. It was shown that the travelling wave state is characteristic for curved duct flow and that the pin made it possible to observe the oscillations within the 270° long curved duct. Travelling waves were observed at flow rates above Dn = 170 (Dn = Re/(R/a)1/2, where Re is the Reynolds number, R is the radius of curvature of the duct and a is the duct dimension. The curvature ratio, R/a, is 15.1).If no other disturbances are imposed, the oscillations are the result of the selective amplification of random disturbances in the flow, leading to a broad frequency spectrum. The travelling wave was found to lock in to an imposed periodic disturbance at a selected frequency. The flow structure of the locked state was investigated in detail, using flow visualization and a one-component laser Doppler anemometer to measure streamwise or spanwise velocities. Direct numerical simulations using the package CFDS-FLOW3D are in very good agreement with the experiments and confirm the existence of a fully developed, streamwise-periodic travelling wave state.The inflow region between the two Dean vortices, which transports low-speed fluid away from the outer wall, creates strongly inflectional spanwise profiles of the streamwise velocity. Similarities with twisting vortices in a curved channel and sinuous oscillations of Görtler vortices show that the travelling waves observed here result from a secondary shear instability of these spanwise inflectional profiles.

Boundary element method in numerical study of three-dimensional Stokes flows in channels of arbitrary shape

2012 ◽  
Vol 9 (1) ◽  
pp. 94-97
Author(s):  
Yu.A. Itkulova
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Cross Section ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Periodic Flows ◽  
Element Method

In the present work creeping three-dimensional flows of a viscous liquid in a cylindrical tube and a channel of variable cross-section are studied. A qualitative triangulation of the surface of a cylindrical tube, a smoothed and experimental channel of a variable cross section is constructed. The problem is solved numerically using boundary element method in several modifications for a periodic and non-periodic flows. The obtained numerical results are compared with the analytical solution for the Poiseuille flow.

Pin-Fin Heat Sink With Horizontal Base and Blocked Edges

2008 ◽  
Author(s):  
D. Sahray ◽  
H. Shmueli ◽  
N. Segal ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Contact Resistance ◽  
Cross Section ◽  
Heat Input ◽  
Heat Sink ◽  
Numerical Study ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Pin Fin

In the present work, horizontal-base pin fin heat sinks exposed to free convection in air are studied. They are made of aluminum, and there is no contact resistance between the base and the fins. For the same base dimensions the fin height and pitch vary. The fins have a constant square cross-section. The edges of the sink are blocked: the surrounding insulation is flush with the fin tips. The effect of fin height and pitch on the performance of the sink is studied experimentally and numerically. In the experiments, the heat sinks are heated using foil electrical heaters. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks and their environment are modeled using the Fluent 6 software. The results show that heat transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are analyzed for various fin heights. Also assessed are effects of the blocked edges as compared to the previously studied cases where the sink edges were exposed to the surroundings.

scholarly journals NUMERICAL STUDY OF RADIATIVE CORRECTIONS IN THE LOW Q2 REGION AT HERA

1994 ◽  
Vol 09 (18) ◽  
pp. 3229-3244
Author(s):  
K. CHARCHULA ◽  
J. GAJEWSKI
Keyword(s):  
Cross Section ◽  
Numerical Study ◽  
Radiative Corrections ◽  
Hadronic Final State ◽  
Radiative Effects ◽  
Final State ◽  
Cross Section Measurement ◽  
Photoproduction Cross Section ◽  
Section Measurement

A detailed numerical study of radiative corrections in the low Q2 region at the HERA ep collider was performed. The specific case of the total photoproduction cross section measurement was taken as an example. Two different programs, TERAD91 and HER-ACLES4.2, were used to get an estimate of the size of radiative effects. It was found that radiative corrections can be quite large at some points of the space of leptonic (x, y) variables. However, after imposing experimentally feasible cuts on the radiated photon and the hadronic final state one gets corrections at the level of a few per cent.

scholarly journals Steady and unsteady flow of non-newtonian fluid in curved pipe with triangular

2006 ◽  
Vol 3 (3) ◽  
pp. 470-480
Author(s):  
Baghdad Science Journal
Keyword(s):  
Unsteady Flow ◽  
Pressure Gradient ◽  
Secondary Flow ◽  
Cross Section ◽  
Numerical Study ◽  
Equations Of Motion ◽  
Curved Pipe ◽  
First Case ◽  
Stable Flow ◽  
Flow Cross

This paper deals with numerical study of the flow of stable and fluid Allamstqr Aniotina in an area surrounded by a right-angled triangle has touched particularly valuable secondary flow cross section resulting from the pressure gradient In the first case was analyzed stable flow where he found that the equations of motion that describe the movement of the fluid

Sign in / Sign up

Export Citation Format

Share Document