Laminar flow through slots

1988 ◽  
Vol 190 ◽  
pp. 179-200 ◽  
Author(s):  
E. G. Tulapurkara ◽  
B. H. Lakshmana Gowda ◽  
N. Balachandran
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Flow Visualization ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Computer Code ◽  
Channel Height ◽  
Visualization Technique ◽  
Recirculating Flow ◽  
Flow Through

Laminar flow through slots is investigated using a flow-visualization technique and the numerical solution of the Navier-Stokes equations for steady flow. In the flow situation studied here, the fluid enters an upper channel blocked at the rear end and leaves through a lower channel blocked at the front end. The two channels are interconnected by one, two and three slots. The flow-visualization technique effectively brings out the various features of the flow through slot(s). The ratio of the slot width to the channel height w/h is varied between 0.5 to 4.0 and the Reynolds number Re, based on the velocity at the entry to the channel and the height of the channel, is varied between 300 and 2000. Both w/h and Re influence the flow in general and the extent of the regions of recirculating flow in particular. The Reynolds number at which the vortex shedding begins depends on w/h. Computations are carried out using the computer code 2/E/FIX of Pun & Spalding (1977). The computed flow patterns closely resemble the observed patterns at various Reynolds numbers investigated except around the Reynolds number where the vortex shedding begins.

scholarly journals Computational and Experimental Study of Turbulent Flow Past an Array of Bluff Bodies Aligned Along the Channel Axis

1997 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shih-Hui Chen
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Channel Height ◽  
Bluff Bodies ◽  
Reynolds Stresses ◽  
Height Ratio ◽  
Channel Axis ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Phase Cycle

Computations and measurements of time mean velocities, total fluctuation intensities, and Reynolds stresses are presented for spatially periodic flows past an array of bluff bodies aligned along the channel axis. The Reynolds number based on the channel hydraulic diameter and cross-sectional bulk mean velocity, the pitch to rib-height ratio, and the rib-height to channel-height ratio were 2 × 104, 10, and 0.133, respectively. The unsteady phase-averaged Navier-Stokes equations were solved using a Reynolds stress model with wall function and wall-related pressure strain treatment to reveal the feature of examined unsteady vortex shedding flow. Laser Doppler velocimetry measurements were performed to measure the velocity filed. Code verifications were performed through comparisons with others’ measured developing single-rib flow and our measured fully developed rib-array flow. The computed results and measured data are found in reasonable agreement, which justifies the turbulence model adopted. The calculated phase-averaged flow field clearly displays the vortex shedding behind the rib and is characterized in terms of shedding Strouhal number, vortex trajectory, vortex celerity, and vortex travelling distance in a phase cycle. Furthermore, the difference between the computed developing single-rib flow and fully developed rib-array flow is addressed.

scholarly journals Heavy Oil Laminar Flow in Corrugated Ducts: A Numerical Study Using the Galerkin-Based Integral Method

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1363
Author(s):  
Valdecir Alves dos Santos Júnior ◽  
Severino Rodrigues de Farias Neto ◽  
Antonio Gilson Barbosa de Lima ◽  
Igor Fernandes Gomes ◽  
Israel Buriti Galvão ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Heavy Oil ◽  
Integral Method ◽  
Numerical Study ◽  
Temperature Dependent ◽  
Flow Through ◽  
Fanning Friction Factor ◽  
Cylindrical Duct

Fluid flow in pipes plays an important role in different areas of academia and industry. Due to the importance of this kind of flow, several studies have involved circular cylindrical pipes. This paper aims to study fully developed internal laminar flow through a corrugated cylindrical duct, using the Galerkin-based integral method. As an application, we present a study using heavy oil with a relative density of 0.9648 (14.6 °API) and temperature-dependent viscosities ranging from 1715 to 13000 cP. Results for different fluid dynamics parameters, such as the Fanning friction factor, Reynolds number, shear stress, and pressure gradient, are presented and analyzed based on the corrugation number established for each section and aspect ratio of the pipe.

Numerical Simulation of Vortex Shedding Past a Circular Cylinder in a Cross-Flow at Low Reynolds Number With Finite Volume-Technique: Part 1 — Forced Oscillations

2007 ◽  
Author(s):  
Antoine Placzek ◽  
Jean-Franc¸ois Sigrist ◽  
Aziz Hamdouni
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Finite Volume ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Cross Flow ◽  
Forced Oscillations ◽  
Lift And Drag ◽  
Wake Characteristics

The numerical simulation of the flow past a circular cylinder forced to oscillate transversely to the incident stream is presented here for a fixed Reynolds number equal to 100. The 2D Navier-Stokes equations are solved with a classical Finite Volume Method with an industrial CFD code which has been coupled with a user subroutine to obtain an explicit staggered procedure providing the cylinder displacement. A preliminary work is conducted in order to check the computation of the wake characteristics for Reynolds numbers smaller than 150. The Strouhal frequency fS, the lift and drag coefficients CL and CD are thus controlled among other parameters. The simulations are then performed with forced oscillations f0 for different frequency rations F = f0/fS in [0.50–1.50] and an amplitude A varying between 0.25 and 1.25. The wake characteristics are analysed using the time series of the fluctuating aerodynamic coefficients and their FFT. The frequency content is then linked to the shape of the phase portrait and to the vortex shedding mode. By choosing interesting couples (A,F), different vortex shedding modes have been observed, which are similar to those of the Williamson-Roshko map.

scholarly journals Confined axisymmetric laminar jets with large expansion ratios

2002 ◽  
Vol 456 ◽  
pp. 319-352 ◽  
Author(s):  
A. REVUELTA ◽  
A. L. SÁNCHEZ ◽  
A. LIÑÁN
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Outer Region ◽  
Outer Wall ◽  
Relevant Parameter ◽  
Order Unity ◽  
Laminar Jet ◽  
Recirculating Flow ◽  
Large Expansion ◽  
Downstream Flow

This paper investigates the steady round laminar jet discharging into a coaxial duct when the jet Reynolds number, Rej, is large and the ratio of the jet radius to the duct radius, ε, is small. The analysis considers the distinguished double limit in which the Reynolds number Rea = Rejε for the final downstream flow is of order unity, when four different regions can be identified in the flow field. Near the entrance, the outer confinement exerts a negligible influence on the incoming jet, which develops as a slender unconfined jet with constant momentum flux. The jet entrains outer fluid, inducing a slow back flow motion of the surrounding fluid near the backstep. Further downstream, the jet grows to fill the duct, exchanging momentum with the surrounding recirculating flow in a slender region where the Reynolds number is still of the order of Rej. The streamsurface bounding the toroidal vortex eventually intersects the outer wall, in a non-slender transition zone to the final downstream region of parallel streamlines. In the region of jet development, and also in the main region of recirculating flow, the boundary-layer approximation can be used to describe the flow, while the full Navier–Stokes equations are needed to describe the outer region surrounding the jet and the final transition region, with Rea = Rejε entering as the relevant parameter to characterize the resulting non-slender flows.

Analysis of thermo-hydraulic and entropy generation characteristics for flow through ribbed-wavy channel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sumit Kumar Mehta ◽  
Sukumar Pati ◽  
Shahid Ahmed ◽  
Prangan Bhattacharyya ◽  
Jishnu Jyoti Bordoloi
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Entropy Generation ◽  
Relative Magnitude ◽  
Temperature Fields ◽  
Wavy Channel ◽  
Content Type ◽  
Flow Through ◽  
Numerical Solver ◽  
Wavy Channels

Purpose The purpose of this study is to analyze the thermal, hydraulic and entropy generation characteristics for laminar flow of water through a ribbed-wavy channel with the top wall as wavy and bottom wall as flat with ribs of three different geometries, namely, triangular, rectangular and semi-circular. Design/methodology/approach The finite element method-based numerical solver has been adopted to solve the governing transport equations. Findings A critical value of Reynolds number (Recri) is found beyond which, the average Nusselt number for the wavy or ribbed-wavy channel is more than that for a parallel plate channel and the value of Recri decreases with the increase in a number of ribs and for any given number of ribs, it is minimum for rectangular ribs. The performance factor (PF) sharply decreases with Reynolds number (Re) up to Re = 50 for all types of ribbed-wavy channels. For Re > 50, the change in PF with Re is gradual and decreases for all the ribbed cases and for the sinusoidal channel, it increases beyond Re = 100. The magnitude of PF strongly depends on the shape and number of ribs and Re. The relative magnitude of total entropy generation for different ribbed channels varies with Re and the number of ribs. Practical implications The findings of the present study are useful to design the economic heat exchanging devices. Originality/value The effects of shape and the number of ribs on the heat transfer performance and entropy generation have been investigated for the first time for the laminar flow regime. Also, the effects of shape and number of ribs on the flow and temperature fields and entropy generation have been investigated in detail.

scholarly journals Numerical Investigation on the Effects of Vortex Shedding on Boundary Layer Unsteadiness

1970 ◽  
Vol 37 ◽  
pp. 33-39
Author(s):  
ABM Toufique Hasan ◽  
Dipak Kanti Das
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Finite Element ◽  
Flow Field ◽  
Flat Plate ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Number Range ◽  
Rotating Speed ◽  
Rotating Circular Cylinder

The interaction between an initially laminar boundary layer developed spatially on a flat plate under the influence of vortex shedding induced from a rotating circular cylinder has been simulated numerically. The rotational speed of the cylinder is varied to generate the vortex shedding of different intensities. Also the flat plate is kept at different positions from the cylinder. Due to asymmetry in the flow field, the present problem is governed by unsteady Navier-Stokes equations which are simulated numerically by finite element method. Computations are carried out for low Reynolds number range up to 1000. Instantaneous development of the flow field, unsteady boundary layer integral parameters, and wall skin friction are presented on different streamwise locations over the plate. From the computation, it is observed that the vortex shedding substantially affects the boundary layer development. The disturbed displacement and momentum thicknesses of the plate increase up to 1.6 times and 2.6 times of the undisturbed flow, respectively. Also the plate shape factor approaches a value of 1.5 which is typical for turbulent flow. This interaction strongly depends on the rotating speed of the cylinder, the relative positions of the cylinder and the plate and also on Reynolds number of the flow. Keywords: Vortex shedding, finite element, boundary layer, wall skin friction.doi:10.3329/jme.v37i0.817Journal of Mechanical Engineering Vol.37 June 2007, pp.33-39

Effect of Reynolds number in laminar flow through a sudden planar contraction

AIChE Journal ◽  
1985 ◽  
Vol 31 (10) ◽  
pp. 1736-1739 ◽  
Author(s):  
E. Mitsoulis ◽  
J. Vlachopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Flow Through ◽  
Planar Contraction

scholarly journals Thermal Performance Enhancement of the Mixed Convection between two Parallel Plates by using Triangular Ribs

2021 ◽  
Vol 26 (2) ◽  
pp. 11-30
Author(s):  
K.A. Jehhef ◽  
F.A. Badawy ◽  
A.A. Hussein
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Performance Enhancement ◽  
Stokes Equations ◽  
Channel Width ◽  
Heated Wall ◽  
Channel Height ◽  
Parallel Plates

Abstract This paper aims to investigate the mixed convection between two parallel plates of a vertical channel, in the presence of a triangular rib. The non-stationary Navier-Stokes equations were solved numerically in a two-dimensional formulation for the low Reynolds number for the laminar air flow regime. Six triangular ribs heat-generating elements were located equidistantly on the heated wall. The ratio of the ribs to the channel width is varied (h / H = 0.1, 0.2, 0.3 and 0.4) to study the effect of ribs height effects, the ratio of the channel width to the ribs height is fixed constant at (H / w = 2) and the ratio of the channel height to the ribs pitch is fixed at (W/p=10). The influence of the Reynolds number that ranged from 68 to 340 and the Grashof number that ranged from 6.6 ×103 to 2.6 ×104 as well as the Richardson number chosen (1.4, 0.7, 0.4 and 0.2) is studied. The numerical results are summarized and presented as the profile of the Nusselt number, the coefficient of friction, and the thermal enhancement factor. The contribution of forced and free convection to the total heat transfer is analyzed. Similar and distinctive features of the behavior of the local and averaged heat transfer with the variation of thermal gas dynamic and geometric parameters are investigated in this paper. The results showed that the Nusselt number and friction factor increased by using the attached triangular ribs, especially when using the downstream ribs. Also, the results revealed that the Nusselt number increased by increasing the ratio of the ribs to the channel width.

Unsteady Isothermal Flow Through a Staggered Tube Bundle Array

2012 ◽  
Author(s):  
Artit Ridluan ◽  
Surasing Arayangkun ◽  
Coochart Phayom
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Cfd Simulation ◽  
Transient Flow ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Isothermal Flow ◽  
Flow Through

Two-dimensional Unsteady simulations of isothermal flow through a staggered tube bundle array at three different Reynolds numbers 54, 72, and 90 were investigated. The Navier-Stokes equations are numerically solved. Based on the CFD simulation results, the unsteady flow patterns were developed behind the rear row of the array, while for the other rows, the steady separated and reattached flow behaviors were observed, small, short, and closed separation bubble behind the rods. At Reynolds Number of 54, the transient flow was perfectly periodic. The complicated patterns of unsteady flow could be observed at Reynolds numbers of 72 and 90. The shedding patterns of vortices from the last rods were different and no longer periodic as found at Reynolds number of 54. The degree of chaos is increased as Reynolds number progressed.

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