Turbulence Generated Secondary Flows in Ducts of Non-Circular Cross-Section

1982 ◽  
Vol 24 (3) ◽  
pp. 119-127
Author(s):  
W. J. Seale
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Secondary Flows ◽  
Algebraic Expression ◽  
Rod Bundle ◽  
Stress Models

The use of algebraic stress models in the prediction of secondary flows in straight ducts of non-circular cross-section is found to be unsatisfactory and to give inconsistent results in the sub-channels within a rod bundle. An algebraic expression is presented which allows the source of axial vorticity to be calculated directly and without iteration. The expression is shown to reproduce secondary velocities in square and triangular ducts, and in a duct consisting of two inter-connected subchannels.

scholarly journals Two-phase flow in channels with non-circular cross-section of pneumatic transport of powder material

2018 ◽  
Vol 22 (Suppl. 5) ◽  
pp. 1407-1424
Author(s):  
Sasa Milanovic ◽  
Milos Jovanovic ◽  
Zivan Spasic ◽  
Boban Nikolic
Keyword(s):  
Cross Section ◽  
Numerical Experiments ◽  
Circular Cross Section ◽  
Pneumatic Transport ◽  
Secondary Flows ◽  
Solid Particles ◽  
Stress Model ◽  
Two Phase ◽  
Initial Flow ◽  
Numerical Grid

The paper presents a numerical simulation of two-phase turbulent flow in straight horizontal channels of pneumatic transport with non-circular cross-section. For the granular flow simulation, we have chosen the flow of solid particles of quartz, flour, and ash in the flow of air, which is transporting fluid. During the modeling of the flow, the transported solid particles are reduced to spherical shapes. A correction of the stress model of turbulence is performed by taking into account the influences of the induction of secondary flows of the second order in the gas phase. The full Reynolds stress model was used for modeling the turbulence, and the complete model is used for the turbulent stresses and turbulent temperature fluxes. All numerical experiments were conducted for the same initial flow conditions and a single uniform grid was adopted for all numerical experiments. The flow is observed in a straight channel of a square cross-section and dimensions of sides of 200 mm and the length of 80 Dh. During the simulation, the fineness of the numerical grid was also tested, and the paper shows results of the numerical grid of the highest resolution beyond which the fineness does not influence the obtained results. The paper offers graphics of velocities of the solid particles transported by the transporting fluid (air) along the channel.

scholarly journals Flow of a new class of non-Newtonian fluids in tubes of non-circular cross-sections

2019 ◽  
Vol 377 (2144) ◽  
pp. 20180069 ◽  
Author(s):  
Juan P. Gomez-Constante ◽  
Kumbakonam R. Rajagopal
Keyword(s):  
Shear Stress ◽  
Velocity Field ◽  
Cross Section ◽  
Cross Sections ◽  
Applied Mathematics ◽  
Constitutive Relations ◽  
Maximum Shear Stress ◽  
Circular Cross Section ◽  
Secondary Flows ◽  
Shear Stresses

Fluids described by constitutive relations wherein the symmetric part of the velocity gradient is a function of the stress can be used to describe the flows of colloids and suspensions. In this paper, we consider the flow of a fluid obeying such a constitutive relation in a tube of elliptic and other non-circular cross-sections with the view towards determining the velocity field and the stresses that are generated at the boundary of the tube. As tubes are rarely perfectly circular, it is worthwhile to study the structure of the velocity field and the stresses in tubes of non-circular cross-section. After first proving that purely axial flows are possible, that is, there are no secondary flows as in the case of many viscoelastic fluids, we determine the velocity profile and the shear stresses at the boundaries. We find that the maximum shear stress is attained at the co-vertex of the ellipse. In general tubes of non-circular cross-section, the maximum shear stress occurs at the point on the boundary that is closest to the centroid of the cross-section. This article is part of the theme issue ‘Rivlin's legacy in continuum mechanics and applied mathematics’.

Secondary Flows in Eccentric-Annular Tubes

2019 ◽  
Author(s):  
Mario Letelier ◽  
Dennis A. Siginer ◽  
Diego L. Almendra ◽  
Juan Stockle
Keyword(s):  
Cross Section ◽  
Shape Factor ◽  
Vortical Structure ◽  
Circular Cross Section ◽  
Weissenberg Number ◽  
Secondary Flows ◽  
Material Parameters ◽  
Annular Cross Section ◽  
Nonlinear Viscoelastic ◽  
Transversal Flow

Abstract In this paper, transversal flow field of nonlinear viscoelastic fluids abiding by the modified-Phan-Thien-Tanner (MPTT) constitutive model in straight tubes of eccentric-annular cross-section is investigated. An analytical solution is developed based on an asymptotic expansion in terms of the Weissenberg number coupled with the shape factor method a one-to-one mapping taking the circular cross-section into the eccentric annular cross section. The analysis reveals the formation of transversal flows due to elasticity and to the eccentricity parameter. The number of vortices in the cross-section depends on the ratio of the diameters in addition to the eccentricity parameter. The effect of these parameters on the vortical structure is explored for different values of the material parameters.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

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