Preliminary Numerical Solutions of the Evolution of Free Jets

2012 ◽  
Author(s):  
Fabio Gori ◽  
Matteo Angelino ◽  
Andrea Boghi ◽  
Ivano Petracci
Keyword(s):  
Numerical Solutions ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Centerline Velocity ◽  
Two Dimensional ◽  
Potential Core ◽  
Free Jet ◽  
Air Jet ◽  
Flow Evolution ◽  
Metallic Grids

The present paper presents preliminary numerical solutions of the flow evolution of a two dimensional rectangular free jet. The numerical simulations in a two-dimensional domain are carried out with Open-FOAM, the open-source code, and compare the numerical results with the experimental visualizations performed in the same laboratory with the shadowgraph technique. The evolution of a two-dimensional submerged free jet is reported in the literature by the presence of two regions of flow: the potential core, where the centerline velocity maintains equal to that on the slot exit, and the turbulent or mixing region, where the centerline velocity decreases with the distance from the exit. Previous anemometric measurements, carried out in this laboratory with an air jet emerging from a rectangular channel, showed the presence of a region of flow, just outside the exit and before the potential core, where velocity and turbulence remain almost equal to those measured on the exit, and it has been called “undisturbed region of flow” because is present also in turbulent conditions. Previous and present shadowgraph visualizations show a jet which has the same height along the undisturbed region of flow and increases its height afterwards. The length of the undisturbed region depends on the Reynolds number of the flow and on the presence of turbulence promoters, e.g. metallic grids, at the exit of the slot. The undisturbed region is becoming nil with the increase of the Reynolds numbers, in agreement to the literature. The present two dimensional numerical solutions, carried out at Re numbers equal to 25,000 and 60,000 confirm the results obtained with the shadow visualizations.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

scholarly journals Planar flows past thin multi-blade configurations

1996 ◽  
Vol 324 ◽  
pp. 355-377 ◽  
Author(s):  
F. T. Smith ◽  
S. N. Timoshin
Keyword(s):  
Boundary Layer ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Laminar Flows ◽  
Two Dimensional ◽  
Boundary Layer Equations ◽  
Require Solution ◽  
Lift And Drag ◽  
Planar Flows ◽  
Steady Laminar

Two-dimensional steady laminar flows past multiple thin blades positioned in near or exact sequence are examined for large Reynolds numbers. Symmetric configurations require solution of the boundary-layer equations alone, in parabolic fashion, over the successive blades. Non-symmetric configurations in contrast yield a new global inner–outer interaction in which the boundary layers, the wakes and the potential flow outside have to be determined together, to satisfy pressure-continuity conditions along each successive gap or wake. A robust computational scheme is used to obtain numerical solutions in direct or design mode, followed by analysis. Among other extremes, many-blade analysis shows a double viscous structure downstream with two streamwise length scales operating there. Lift and drag are also considered. Another new global interaction is found further downstream. All the interactions involved seem peculiar to multi-blade flows.

A two-dimensional vortex condensate at high Reynolds number

2013 ◽  
Vol 715 ◽  
pp. 359-388 ◽  
Author(s):  
Basile Gallet ◽  
William R. Young
Keyword(s):  
Stokes Equation ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Finite Limit ◽  
Two Dimensional ◽  
Navier Stokes Equation ◽  
Quasilinear Theory ◽  
Zero Integral ◽  
High Reynolds

AbstractWe investigate solutions of the two-dimensional Navier–Stokes equation in a $\lrm{\pi} \ensuremath{\times} \lrm{\pi} $ square box with stress-free boundary conditions. The flow is steadily forced by the addition of a source $\sin nx\sin ny$ to the vorticity equation; attention is restricted to even $n$ so that the forcing has zero integral. Numerical solutions with $n= 2$ and $6$ show that at high Reynolds numbers the solution is a domain-scale vortex condensate with a strong projection on the gravest mode, $\sin x\sin y$. The sign of the vortex condensate is selected by a symmetry-breaking instability. We show that the amplitude of the vortex condensate has a finite limit as $\nu \ensuremath{\rightarrow} 0$. Using a quasilinear approximation we make an analytic prediction of the amplitude of the condensate and show that the amplitude is determined by viscous selection of a particular solution from a family of solutions to the forced two-dimensional Euler equation. This theory indicates that the condensate amplitude will depend sensitively on the form of the dissipation, even in the undamped limit. This prediction is verified by considering the addition of a drag term to the Navier–Stokes equation and comparing the quasilinear theory with numerical solution.

Numerical Investigation on Visualizations of Confined Air Flow in a Slot Jet Inside a Rectangular Channel

2015 ◽  
Vol 813-814 ◽  
pp. 736-741
Author(s):  
M. Muthukannan ◽  
P. Rajesh Kanna ◽  
S. Jeyakumar ◽  
J.Y. Raja Shangaravel ◽  
S. Raghu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Numerical Investigation ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Vortex Center ◽  
Computational Domain ◽  
Reattachment Length ◽  
Aspect Ratios ◽  
Air Jet

In the present numerical investigation, the flow field of confined slot air jet in a rectangular computational domain is reported. In the present work the flow field parameters like reattachment length, vortex center and horizontal velocity profiles for various Reynolds numbers and for various aspect ratios are presented .The present study reveals that the vortex centers are moving in a downstream direction with increase in Reynolds number. The reattachment length is directly dependent on the Reynolds numbers. In case of vortex dynamics, the vortex size is indirectly dependent on the inlet jet width. In the present investigation, SIMPLE algorithm is used to solve the governing equations. It is concluded that the aspect ratio and the Reynolds number are playing dominant roles in flow field of the present computational domain.

Characterization of the Behavior of Confined Laminar Round Jets

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
D. Tyler Landfried ◽  
Anirban Jana ◽  
Mark Kimber
Keyword(s):  
Stokes Equations ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Half Width ◽  
Navier Stokes ◽  
Centerline Velocity ◽  
Navier Stokes Equations ◽  
Free Jet ◽  
Round Jets

In this work, the Navier–Stokes equations are solved for a laminar, round jet in a large confinement. The flow is characterized as a function of the enclosure-to-jet diameter ratio, in the range 40–100, and the Reynolds numbers at jet inlet in the range 32–65. Results for jet decay and half width suggest that near the jet inlet the flow is identical to a free jet but eventually deviates away from the jet inlet. We develop a set of correlations including the jet centerline velocity and the jet half width, and features of the transition regions in the flow field.

Triple-deck solutions for supersonic flows past flared cylinders

1987 ◽  
Vol 179 ◽  
pp. 469-487 ◽  
Author(s):  
Ph. Gittler ◽  
A. Kluwick
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Asymptotic Expansions ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Hysteresis Phenomenon ◽  
Two Dimensional ◽  
Planar Flow ◽  
Laminar Boundary Layers ◽  
External Flows

Using the method of matched asymptotic expansions, the interaction between axisymmetric laminar boundary layers and supersonic external flows is investigated in the limit of large Reynolds numbers. Numerical solutions to the interaction equations are presented for flare angles α that are moderately large. If α > 0 the boundary layer separates upstream of the corner and the formation of a plateau structure similar to the two-dimensional case is observed. In contrast to the case of planar flow, however, separation can occur also if α < 0, owing to the axisymmetric effect of overexpansion and recompression. The separation point then is located downstream of the corner and, most remarkable, a hysteresis phenomenon is observed.

A Two-Dimensional Analysis of a Heated Free Jet at Low Reynolds Numbers

1971 ◽  
Vol 93 (3) ◽  
pp. 355-363 ◽  
Author(s):  
S. Krishnan ◽  
L. R. Glicksman
Keyword(s):  
Variable Viscosity ◽  
Fluid Dynamic ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Rotating Drum ◽  
Low Reynolds Numbers ◽  
Free Jet ◽  
Approximate Integral ◽  
Jet Behavior ◽  
Flow Through

To spin polymers and glass into continuous fibers, hot molten material is made to flow through a nozzle into air, thus forming a free liquid jet. This cools as it proceeds through the air and the solid fiber is collected on a rotating drum. This maintains a tension on the jet causing it to attenuate as it cools. An approximate integral technique is presented to investigate the relative importance of two-dimensional fluid mechanics for a variable viscosity glass jet in the region of the jet within four to five nozzle diameters of the nozzle exit. The results, when compared with those of an existing analysis based on one-dimensional velocity and temperature profiles, indicate that two-dimensional fluid dynamic effects exert very little influence on the jet shape while small changes in the temperature distribution cause significant changes in the jet behavior. A limited number of experiments performed with a chlorinated polymer provided a very simple and inexpensive means of modeling glass flow and also served to verify the results of the existing analysis over a different range of property values as compared to glass.

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