Numerical Simulation of Flow Past Multiple Porous Cylinders

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
M. H. Al-Hajeri ◽  
A. Aroussi ◽  
A. Witry
Keyword(s):  
Reynolds Number ◽  
Power Plants ◽  
Flow Behavior ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Solid Cylinder ◽  
Flow Past ◽  
Line Array ◽  
Face Velocity ◽  
Porous Cylinders

The present study numerically investigates two-dimensional laminar flow past three circular porous cylinders arranged in an in-line array. Six approaches to face velocity (Vi/Vf) ratios are used and particle trajectories are computed for a range of velocities and particle diameters. Furthermore, the flow past a solid cylinder, which had similar geometry characteristics to the porous cylinders used in this study, is compared with the flow around multiple porous cylinders. For the same range of Reynolds number (312–520), the flow behavior around the solid cylinder differs from the flow around the porous cylinders. The flow characteristics around solid cylinders are determined by the Reynolds number, whereas the flow characteristics around the porous cylinders are detrained by the Vi/Vf ratio. Stagnation areas are found behind each porous cylinder, and the size of these areas increases as the Vi/Vf velocity ratio increases. Furthermore, for the particle ranges used in power plants (<50 μm), the particles were uniformly distributed around the surface of the porous cylinders.

Flow Characteristics of a Low Reynolds Number Jet in Crossflow with an Obstacle Block

2016 ◽  
Vol 9 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Jianlong Chang ◽  
Xudong Shao ◽  
Xiao Hu ◽  
Shuangbiao Zhang
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Vortex Pair ◽  
Lower Velocity ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Crossflow Velocity ◽  
Low Reynolds

The jet in crossflow at very low Reynolds number (Re=100) with and without block is performed by means of large eddy simulation for the jet-to-crossflow velocity ratios (r) ranging from 1 to 3, and the corresponding flow characteristics are compared. The results show that the time-averaged particle trajectories of the jet are slightly changed if a block is presented, and the mixed vortices are weakened. The existence of the block also can accelerate the formation of stable counter-rotating vortex pair. At lower velocity ratio (r=1), the block has little effect on the jet in crossflow with a symmetrically positive and negative kidney shaped vortices. As the velocity ratio increases, the effect of block not only can generate an asymmetry of positive and negative kidney shaped vortices, but also it can reinforce the interaction between the positive and negative vortices in the jet in crossflow. The effect of block on the temperature field is also analyzed in detail.

Anisotropy-Invariant Mapping of Turbulence in a Flow Past an Unswept Airfoil at High Angle of Attack

2005 ◽  
Vol 128 (3) ◽  
pp. 559-567 ◽  
Author(s):  
N. Jovičić ◽  
M. Breuer ◽  
J. Jovanović
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Separation Bubble ◽  
Flow Behavior ◽  
Angle Of Attack ◽  
High Angle ◽  
High Angle Of Attack ◽  
Fine Grid ◽  
Flow Past ◽  
Moderate Reynolds Number

Turbulence investigations of the flow past an unswept wing at a high angle of attack are reported. Detailed predictions were carried out using large-eddy simulations (LES) with very fine grids in the vicinity of the wall in order to resolve the near-wall structures. Since only a well-resolved LES ensures reliable results and hence allows a detailed analysis of turbulence, the Reynolds number investigated was restricted to Rec=105 based on the chord length c. Admittedly, under real flight conditions Rec is considerably higher (about (35-40)∙106). However, in combination with the inclination angle of attack α=18 deg this Rec value guarantees a practically relevant flow behavior, i.e., the flow exhibits a trailing-edge separation including some interesting flow phenomena such as a thin separation bubble, transition, separation of the turbulent boundary layer, and large-scale vortical structures in the wake. Due to the fine grid resolution applied, the aforementioned flow features are predicted in detail. Thus, reliable results are obtained which form the basis for advanced turbulence analysis. In order to provide a deeper insight into the nature of turbulence, the flow was analyzed using the invariant theory of turbulence by Lumley and Newman (J. Fluid Mech., 82, 161–178, 1977). Therefore, the anisotropy of various portions of the flow was extracted and displayed in the invariant map. This allowed us to examine the state of turbulence in distinct regions and provided an improved illustration of what happens in the turbulent flow. Thus, turbulence itself and the way in which it develops were extensively investigated, leading to an improved understanding of the physical mechanisms involved, not restricted to a standard test case such as channel flow but for a realistic, practically relevant flow problem at a moderate Reynolds number.

Flow Past Large Obstructions Between Corotating Disks in Fixed Cylindrical Enclosures

1997 ◽  
Vol 119 (3) ◽  
pp. 499-505 ◽  
Author(s):  
Hiroshi Suzuki ◽  
Joseph A. C. Humphrey
Keyword(s):  
Reynolds Number ◽  
Flow Characteristics ◽  
Empty Space ◽  
Disk Surface ◽  
Dynamical Instability ◽  
Theoretical Expression ◽  
Disk Radius ◽  
Flow Past ◽  
Arm Support ◽  
Torque Coefficient

Numerical calculations have been performed for isothermal, laminar, three-dimensional flow past one or two fixed obstructions radially aligned and symmetrically located between a pair of disks corotating in a fixed cylindrical enclosure. The single-obstruction cases respectively model the influence on the flow of (a) a magnetic head arm support and (b) an air lock. The dual-obstruction cases model the simultaneous presence of these two objects. The air lock produces an interdisk cross-stream plane blockage of 62 percent while the two head arm supports produce blockages of 31 percent and 62 percent, respectively. For the cases with the air lock and arm support simultaneously present, the circumferential angle between them is fixed to 40 or 80 deg. Velocity, pressure, shear stress and the disk torque coefficient are predicted mostly for a Reynolds number (Re=ΩR22/v) corresponding to 10,000, approximately, where R2, Ω, and v are the disk radius, the disk angular velocity in rad/s, and the kinematic viscosity of air at 300 K, respectively. The calculations show that a large blockage significantly alters the interdisk flow characteristics by markedly raising the pressure ahead of an obstruction and accelerating the flow through the empty space around it. This induces a detached region of reversed flow ahead of the obstruction, quite distinct from that in its wake. The disk surface pressure distributions point to a potential source of dynamical instability in rotating disk flows with obstructions. By redefining the torque coefficient and Reynolds number to account for dual blockage effects the relationship between these two quantities generally follows the theoretical expression of Humphrey et al. (1992). It is shown that the bulk of the drag on an obstruction is form drag as opposed to friction drag.

Influence of Staggering Angle of a Rotating Rod on Flow Past a Circular Cylinder

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
T. Ayyappan ◽  
S. Vengadesan
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Flow Characteristics ◽  
Diameter Ratio ◽  
Speed Ratio ◽  
Minimum Drag ◽  
Flow Past ◽  
Pitch Length ◽  
Stagger Angle

The influence of the staggering position of a rotating rod on flow past a main circular cylinder is investigated numerically. The rod is rotated at a constant speed ratio of 3. The effect of the diameter ratio of the rotating rod is studied by considering two different diameter ratios. The investigation is carried out at a fixed pitch length of 1. The study is carried out for two Reynolds number, viz., 100 and 500. The momentum injection from the rod is found to alter the flow characteristics behind the main cylinder. For a certain arrangement of stagger angle and diameter ratio, the vortex shedding behind the main cylinder gets suppressed. The corresponding configuration for which minimum drag coefficient is achieved is suggested from this study.

Flow Characteristics of Low Concentration Non-Newtonian Fluid Through a Channel With an Obstruction at the Entry

2002 ◽  
Author(s):  
M. A. Kabir ◽  
M. M. K. Khan ◽  
M. G. Rasul
Keyword(s):  
Reynolds Number ◽  
Newtonian Fluid ◽  
Reverse Flow ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Channel Length ◽  
Width Ratio ◽  
Test Channel ◽  
Low Concentration ◽  
Channel Velocity

The flow of Newtonian fluid (eg. water) in the test channel with an obstruction at the entrance placed in a wider channel was seen to be stagnant, forward or reverse depending on the position of the obstruction. This interesting flow phenomenon has potential benefit and can be employed in the control of energy and various flows in process engineering. This study was extended to non-Newtonian fluid for further investigation using flat plate as an obstruction. A low concentration polyacrylamide fluid solution (0.018%) showing non-Newtonian fluid behavior was used in this investigation. The parameters that affect the flow inside and around the test channel were the gap (g) between the obstruction geometry and the test channel, the Reynolds number and the length of the test channel. The maximum reverse flow inside the test channel observed was 20%–25% of the outside test channel velocity at g/w (gap to width) ratio of 1 for Reynolds number of 1000 to 3500. The results of the influence of the test channel length and the Reynolds number on the velocity ratio (Vi/Vo: inside velocity/outside velocity in the test channel) is also presented and discussed.

Fluid Flow Behavior for a Confined Rotating MCM Disk With Round Jet Array Impingement

2007 ◽  
Author(s):  
C. J. Fang ◽  
C. Y. Lee ◽  
C. H. Peng ◽  
T. W. Lin ◽  
Y. H. Hung
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Turbulence Intensity ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Streamwise Velocity ◽  
Potential Core ◽  
Round Jet ◽  
Jet Array

A series of experimental investigations on the studies related to fluid flow characteristics of a confined rotating Multi-Chip Module (MCM) disk with round air jet array impingement have been performed. The relevant parameters influencing fluid flow characteristics include the ratio of jet separation distance to nozzle diameter (H/d), jet Reynolds number (Rej) and rotational Reynolds number (Rer). The parametric ranges are Rej = 712 – 4087, Rer = 0 – 2906, H/d = 0.83–14.4 and Z/d = 1–7. The potential core lengths of all the nozzle jets increases with increasing jet Reynolds number or H/d ratio and decreases with increasing rotational Reynolds number. New correlations of the ratio of potential core length to nozzle diameter at various nozzle jets in terms of relevant influencing parameters are proposed. Furthermore, the strengths on both streamwise velocity and turbulence intensity increase with increasing Z/d ratio. The turbulence intensity for the cases of jet array impingement growing up along the axial directions are significantly faster than the cases of single round jet impingement. The jet array impingement has a higher momentum flux in the flow interaction region between two adjacent nozzles; accordingly, it can achieve a more uniform thermal performance as compared with the cases of single round jet impingement. Near-surface fluid flow behavior including the streamwise velocity and turbulence intensity distributions can be employed to interpret the heat transfer characteristics for jet array impingement.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

Sign in / Sign up

Export Citation Format

Share Document