scholarly journals Secondary motion in three-dimensional branching networks

2017 ◽  
Vol 29 (6) ◽  
pp. 063602 ◽  
Author(s):  
Abhijit Guha ◽  
Kaustav Pradhan
Keyword(s):  
Three Dimensional ◽  
Branching Networks ◽  
Secondary Motion

Secondary motion in convection layers generated by lateral heating of a solute gradient

2002 ◽  
Vol 455 ◽  
pp. 1-19 ◽  
Author(s):  
CHO LIK CHAN ◽  
WEN-YAU CHEN ◽  
C. F. CHEN
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Convection Cell ◽  
Experimental Conditions ◽  
Longitudinal Plane ◽  
Secondary Motion ◽  
Solute Gradient

The three-dimensional motion observed by Chen & Chen (1997) in the convection cells generated by sideways heating of a solute gradient is further examined by experiments and linear stability analysis. In the experiments, we obtained visualizations and PIV measurements of the velocity of the fluid motion in the longitudinal plane perpendicular to the imposed temperature gradient. The flow consists of a horizontal row of counter-rotating vortices within each convection cell. The magnitude of this secondary motion is approximately one-half that of the primary convection cell. Results of a linear stability analysis of a parallel double-diffusive flow model of the actual ow show that the instability is in the salt-finger mode under the experimental conditions. The perturbation streamlines in the longitudinal plane at onset consist of a horizontal row of counter-rotating vortices similar to those observed in the experiments.

Design and Construction of Three-Dimensional Physiologically-Based Vascular Branching Networks for Respiratory Assist Devices

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Jose Santos ◽  
Alla A Gimbel ◽  
Athanasios Peppas ◽  
James G Truslow ◽  
Daniel Lang ◽  
...  
Keyword(s):  
Drug Development ◽  
Three Dimensional ◽  
Lab On A Chip ◽  
In Vitro Diagnostics ◽  
Assist Devices ◽  
Branching Networks ◽  
Physiologically Based ◽  
Vascular Branching ◽  
Design And Construction

Microfluidic lab-on-a-chip devices are changing the way that in vitro diagnostics and drug development are conducted, based on the increased precision, miniaturization and efficiency of these systems relative to prior...

Analysis of Buoyancy and Tube Rotation Relative to the Modified Chemical Vapor Deposition Process

1990 ◽  
Vol 112 (4) ◽  
pp. 1063-1069 ◽  
Author(s):  
M. Choi ◽  
Y. T. Lin ◽  
R. Greif
Keyword(s):  
Secondary Flow ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Horizontal Tube ◽  
Deposition Process ◽  
Secondary Flows ◽  
Secondary Motion

The secondary flows resulting from buoyancy effects in respect to the MCVD process have been studied in a rotating horizontal tube using a perturbation analysis. The three-dimensional secondary flow fields have been determined at several axial locations in a tube whose temperature varies in both the axial and circumferential directions for different rotational speeds. For small rotational speeds, buoyancy and axial convection are dominant and the secondary flow patterns are different in the regions near and far from the torch. For moderate rotational speeds, the effects of buoyancy, axial and angular convection are all important in the region far from the torch where there is a spiraling secondary flow. For large rotational speeds, only buoyancy and angular convection effects are important and no spiraling secondary motion occurs far downstream. Compared with thermophoresis, the important role of buoyancy in determining particle trajectories in MCVD is presented. As the rotational speed increases, the importance of the secondary flow decreases and the thermophoretic contribution becomes more important. It is noted that thermophoresis is considered to be the main cause of particle deposition in the MCVD process.

Cellular vortex shedding in the wake of a tapered plate

2008 ◽  
Vol 617 ◽  
pp. 355-379 ◽  
Author(s):  
VAGESH D. NARASIMHAMURTHY ◽  
HELGE I. ANDERSSON ◽  
BJØRNAR PETTERSEN
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Vortex Shedding ◽  
High Reynolds Number ◽  
Three Dimensional ◽  
Base Pressure ◽  
Recirculation Bubble ◽  
Apparent Lack ◽  
Secondary Motion ◽  
High Reynolds

Direct numerical simulation (DNS) of vortex shedding behind a tapered plate with the taper ratio 20 placed normal to the inflow has been performed. The Reynolds numbers based on the uniform inflow velocity and the width of the plate at the wide and narrow ends were 1000 and 250, respectively. For the first time ever cellular vortex shedding was observed behind a tapered plate in a numerical experiment (DNS). Multiple cells of constant shedding frequency were found along the span of the plate. This is in contrast to apparent lack of cellular vortex shedding found in the high-Reynolds-number experiments by Gaster & Ponsford (Aero. J., vol. 88, 1984, p. 206). However, the present DNS data is in good qualitative agreement with similar high-Reynolds-number experimental data produced by Castro & Watson (Exp. Fluids, vol. 37, 2004, p. 159). It was observed that a tapered plate creates longer formation length coupled with higher base pressure as compared to non-tapered (i.e. uniform) plates. The three-dimensional recirculation bubble was nearly conical in shape. A significant base pressure reduction towards the narrow end of the plate, which results in a corresponding increase in Strouhal number, was noticed. This observation is consistent with the experimental data of Castro & Rogers (Exp. Fluids, vol. 33, 2002, p. 66). Pressure-driven spanwise secondary motion was observed, both in the front stagnation zone and also in the wake, thereby reflecting the three-dimensionality induced by the tapering.

Numerical Studies of Three-Dimensional Arterial Flows in Reverse Curvature Geometry: Part I—Peak Flow

1993 ◽  
Vol 115 (3) ◽  
pp. 316-326 ◽  
Author(s):  
R. K. Banerjee ◽  
Y. I. Cho ◽  
L. H. Back
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Outer Wall ◽  
Momentum Effect ◽  
Centrifugal Effect ◽  
Stress Region ◽  
Secondary Motion ◽  
Low Shear Stress ◽  
Experimental Values

A three-dimensional flow simulation at Repeak = 192 and 580 was made in a smooth reverse curvature model that conformed to the gentle “S” shape from a human left femoral artery angiogram. The objective of this numerical investigation was to find the changes in pressure, shear stress, velocity profile, and particle path occurring in the double-curved arterial vessel. Due to the impingement of blood at the outer wall in the first bend region, the wall shear stress approached 40 dyne/cm2—a value over twice as large as in the straight upstream segment. Conversely, at the inner wall in the first bend, a low shear stress region was found where the value of the shear stress was consistently smaller than that in the straight section. The initiation of centrifugal effects caused by the first bend could clearly be seen at Repeak = 580, but due to the close proximity of the reverse curvature segment, the momentum effect due to the second bend overshadowed the centrifugal effect. Hence, only near the end of the second bend did the centrifugal effect due to the second bend result in a double-spiral-secondary motion. In addition, the numerically calculated pressure drop data were in agreement with prior experimental values.

Steady motion through a branching tube

1977 ◽  
Vol 355 (1681) ◽  
pp. 167-187 ◽  
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Cross Sections ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Steady Motion ◽  
Nonlinear Behaviour ◽  
Initial Development ◽  
Secondary Motion ◽  
High Reynolds

The fluid motion through a straight pipe that bifurcates symmetrically into two semi-circular pipes is considered at high Reynolds numbers, with the aim of deriving some of the effects of the three-dimensionality per se. In a corresponding planar problem the long-scale boundary layer approach yields the initial development of the induced pressure gradient fairly directly, the problem being linear. By contrast, in the three-dimensional situation the favourable pressure gradient is determined by a nonlinear eigenvalue relation, because the pressure gradient is much stronger here and interacts critically with the inviscid coreflow to produce nonlinear behaviour near the outer walls. The proposed structure of the initial part of the boundary layer is apparently self-consistent, with a two-tiered development near the outer walls where the secondary motion is of a relatively fast vortex type and the axial skin friction suffers a sharp increase. The secondary coreflow is a displacement-induced streaming combined with a vortex provoked by the pressure gradient. The analysis applies for any realistic oncoming flow in the single tube and can be extended to treat other tube cross-sections.

A Three-Dimensional Model for Piston Ring-Pack Dynamics and Blow-By Gas Flow

2004 ◽  
Author(s):  
Liang Liu ◽  
Tian Tian
Keyword(s):  
Dynamic Behavior ◽  
Gas Flow ◽  
Piston Ring ◽  
Three Dimensional ◽  
Beam Theory ◽  
Ring Structure ◽  
Three Dimensional Model ◽  
Secondary Motion ◽  
Piston Ring Pack ◽  
Ring Pack

A three-dimensional (3D) model for piston ring-pack dynamics and blow-by gas flow was developed to enable more in-depth analyses of the ring-pack performance. This model predicts the 3D dynamic behavior of compression rings and twin-land oil control ring due to the ring’s non-axisymmetric properties, bore distortion and piston secondary motion. Finite element beam theory is used for ring structure calculation. Gas flows along the axial and circumferential directions of the power cylinder system are resolved simultaneously with the ring dynamics. The model was applied to a heavy-duty diesel engine. Particular emphasis was placed on the dynamics of keystone type of top ring, and the stability of the second ring with a twist chamfer and twin-land oil control ring under the influence of piston secondary motion. The variations of the gas pressure and ring dynamic behavior along the circumference are discussed.

Calculation of turbulence-driven secondary motion in non-circular ducts

1984 ◽  
Vol 140 ◽  
pp. 189-222 ◽  
Author(s):  
A. O. Demuren ◽  
W. Rodi
Keyword(s):  
Eddy Viscosity ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Momentum Equation ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Calculation Methods ◽  
Mean Flow ◽  
Square Duct ◽  
Secondary Motion

Experiments on and calculation methods for flow in straight non-circular ducts involving turbulence-driven secondary motion are reviewed. The origin of the secondary motion and the shortcomings of existing calculation methods are discussed. A more refined model is introduced, in which algebraic expressions are derived for the Reynolds stresses in the momentum equations for the secondary motion by simplifying the modelled Reynolds-stress equations of Launder, Reece & Rodi (1975), while a simple eddy-viscosity model is used for the shear stresses in the axial momentum equation. The kinetic energy k and the dissipation rate ε of the turbulent motion which appear in the algebraic and the eddy-viscosity expressions are determined from transport equations. The resulting set of equations is solved with a forward-marching numerical procedure for three-dimensional shear layers. The model, as well as a version proposed by Naot & Rodi (1982), is tested by application to developing flow in a square duct and to developed flow in a partially roughened rectangular duct investigated experimentally by Hinze (1973). In both cases, the main features of the mean-flow and the turbulence quantities are simulated realistically by both models, but the present model underpredicts the secondary velocity while the Naot-Rodi model tends to overpredict it.

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