Description of the flow of mechanically agitated liquid in a system with cylindrical draft-tube and radial baffles

1987 ◽  
Vol 52 (6) ◽  
pp. 1416-1429 ◽  
Author(s):  
Ivan Fořt ◽  
Miloslav Hošťálek ◽  
Hans Dietrich Laufhütte ◽  
Alfons Bertram Mersmann
Keyword(s):  
Stream Function ◽  
High Speed ◽  
Draft Tube ◽  
Laser Doppler Anemometry ◽  
Vertex Angle ◽  
Flat Bottom ◽  
Mean Velocity ◽  
Radial Profiles ◽  
Flow Intensity ◽  
The Mean

A model is described of two-dimensional vortex turbulent flow of homogeneous liquid in a cylindrical tank with flat bottom and radial baffles at its walls agitated with an inclined plane blade impeller rotating in a cylindrical draft-tube. The obtained field of the mean Stokes stream function expresses the streamline distribution in the system. As the boundary conditions of the used solution of stream equation serve partly the values of the mean Stokes stream function on the system boundaries (bottom, liquid level, walls of tank and draft-tube, tank axis), partly the radial profiles of axial and radial components of mean velocity on the level of draft-tube lower base obtained by the laser-doppler anemometry. It follows from the comparison with results of previously published studies that in systems with cylindrical draft-tube and axial high-speed impeller, the convective flow intensity of agitated liquid is higher and the streamline distribution in system is more uniform providing that the conical bottom with 120° vertex angle is used instead of the flat bottom.

Liquid circulation in a cylindrical vessel with radial baffles and inclined blade impeller

1989 ◽  
Vol 54 (6) ◽  
pp. 1599-1611
Author(s):  
Ivan Fořt ◽  
Miloslav Hošťálek ◽  
Jaroslav Medek
Keyword(s):  
Stream Function ◽  
Stokes Equations ◽  
Laser Doppler Anemometry ◽  
Relative Size ◽  
Power Input ◽  
Cylindrical Vessel ◽  
Flat Bottom ◽  
Mean Velocity ◽  
Liquid Circulation ◽  
Radial Profiles

Liquid circulation was studied in a cylindrical vessel with radial baffles under the turbulent flow regime of liquid agitated gradually with the following types of four inclined blade impellers: impeller with plane blades inclined at the angle of 25°; impeller with asymmetrically profiled blades at the angle of 30°-17°; impeller with strength-profiled blades. By solving the turbulent (vortex) analogy of the Stokes equations for the creeping (non-inertial) laminar flow, the streamline distribution (the Stokes stream function) in the bulk of agitated charge was obtained for each of impellers studied (relative size d/D = 1/3, relative distance from the bottom H2/D = 1/3, relative vessel filling H/D = 1), placed axisymmetrically in the vessel and pumping the liquid towards its flat bottom. The zero values of the Stokes stream function at the bottom, walls, and charge liquid level, and further the radial profiles of axial and radial component of mean velocity in the cross sections under and above the impeller obtained experimentally by the laser-doppler anemometry on the assumption of axial symmetry of the agitated system studied were set as the boundary conditions for the solution of the partial differential equation considered. It follows from the results obtained that the homogenous circulation of agitated charge at the relatively lowest value of the impeller power input is reached when agitating with the asymmetrically profiled blade impeller which therefore can successfully replace the propeller mixer with airfoil profiled blades.

scholarly journals Study of Pumping Capacity of Pitched Blade Impellers

10.14311/380 ◽  
2002 ◽  
Vol 42 (4) ◽  
Author(s):  
I. Fořt ◽  
T. Jirout ◽  
R. Sperling ◽  
S. Jambere ◽  
F. Rieger
Keyword(s):  
Laser Doppler Anemometry ◽  
Radial Profile ◽  
Axial Flow ◽  
Power Input ◽  
Vessel Diameter ◽  
Energetic Efficiency ◽  
Turbulent Regime ◽  
Flat Bottom ◽  
Mean Velocity ◽  
Liquid Suspensions

A study was made of the pumping capacity of pitched blade impellers in a cylindrical pilot plant vessel with four standard radial baffles at the wall under a turbulent regime of flow. The pumping capacity was calculated from the radial profile of the axial flow, under the assumption of axial symmetry of the discharge flow. The mean velocity was measured using laser Doppler anemometry in a transparent vessel of diameter T = 400 mm, provided with a standard dished bottom. Three and six blade pitched blade impellers (the pitch angle varied within the interval a Îá24°; 45°ń) of impeller/vessel diameter ratio D/T = 0.36, as well as a three blade pitched blade impeller with folded blades of the same diameter, were tested. The calculated results were compared with the results of experiments mentioned in the literature, above all in cylindrical vessels with a flat bottom. Both arrangements of the agitated system were described by the impeller energetic efficiency, i.e, a criterion including in dimensionless form both the impeller energy consumption (impeller power input) and the impeller pumping effect (impeller pumping capacity). It follows from the results obtained with various geometrical configurations that the energetic efficiency of pitched blade impellers is significantly lower for configurations suitable for mixing solid-liquid suspensions (low impeller off bottom clearances) than for blending miscible liquids in mixing (higher impeller off bottom clearances).

Turbulence measurements in axisymmetric jets of air and helium. Part 2. Helium jet

1993 ◽  
Vol 246 ◽  
pp. 225-247 ◽  
Author(s):  
N. R. Panchapakesan ◽  
J. L. Lumley
Keyword(s):  
Density Ratio ◽  
Effective Diameter ◽  
Mean Velocity ◽  
Velocity Fluctuations ◽  
Air Jet ◽  
Plume Region ◽  
Turbulent Schmidt Number ◽  
Radial Profiles ◽  
The Mean ◽  
Mean Concentration

A turbulent round jet of helium was studied experimentally using a composite probe consisting of an interference probe of the Way–Libby type and an × -probe. Simultaneous measurements of two velocity components and helium mass fraction concentration were made in the x/d range 50–120. These measurements are compared with measurements in an air jet of the same momentum flux reported in Part 1. The jet discharge Froude number was 14000 and the measurement range was in the intermediate region between the non-buoyant jet region and the plume region. The measurements are consistent with earlier studies on helium jets. The mass flux of helium across the jet is within ±10% of the nozzle input. The mean velocity field along the axis of the jet is consistent with the scaling expressed by the effective diameter but the mean concentration decay constant exhibits a density-ratio dependence. The radial profiles of mean velocity and mean concentration agree with earlier measurements, with the half-widths indicating a turbulent Schmidt number of 0.7. Significantly higher intensities of axial velocity fluctuations are observed in comparison with the air jet, while the intensities of radial and azimuthal velocity fluctuations are virtually identical with the air jet when scaled with the half-widths. Approximate budgets for the turbulent kinetic energy, scalar variance and scalar fluxes are presented. The ratio of mechanical to scalar timescales is found to be close to 1.5 across most of the jet. Current models for triple moments involving scalar fluctuations are compared with measurements. As was observed with the velocity triple moments in Part 1, the performance of the Full model that includes all terms except advection was found to be very good in the fully turbulent region of the jet.

Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe

2020 ◽  
Author(s):  
Ayesha Almheiri ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Saqib Salam ◽  
Afshin Goharzadeh
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Tangential Velocity ◽  
Circular Disk ◽  
Pipe Diameter ◽  
Working Fluid ◽  
Complex Flow ◽  
Mean Velocity ◽  
Radial Profiles ◽  
The Mean

Abstract Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.

Axisymmetric Flow in a Motored Reciprocating Engine

1978 ◽  
Vol 192 (1) ◽  
pp. 213-223 ◽  
Author(s):  
A. D. Gosman ◽  
A. Melling ◽  
J. H. Whitelaw ◽  
P. Watkins
Keyword(s):  
Laser Doppler Anemometry ◽  
Axisymmetric Flow ◽  
Flow Characteristics ◽  
Small Scale ◽  
Mean Velocity ◽  
Inlet Velocity ◽  
Reciprocating Engine ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
The Mean

A study was made of axisymmetric, laminar and turbulent flow in a motored reciprocating engine with flow through a cylinder head port. Measurements were obtained by laser-Doppler anemometry and predictions for the laminar case were generated by finite-difference means. Agreement between calculated and measured results is good for the main features of the flow field, but significant small scale differences exist, due partly to uncertainties in the inlet velocity distribution. The measurements show, for example, that the mean velocity field is influenced more strongly by the engine geometry than by the speed. In general, the results confirm that the calculation method can be used to represent the flow characteristics of motored reciprocating engines without compression and suggest that extensions to include compression and combustion are within reach.

Laser Insight Into the Turbulent Swirl Flow Behind the Axial Flow Fan

2014 ◽  
Author(s):  
Đorđe S. Čantrak ◽  
Novica Janković ◽  
Milan R. Lečić
Keyword(s):  
Vortex Core ◽  
High Speed ◽  
Isotropic Turbulence ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Swirl Flow ◽  
Test Rig ◽  
Axial Fan ◽  
Mean Velocity ◽  
Swirl Flows

Complex experimental study of the turbulent swirl flow behind the axial fan is reported in this paper. Axial fan with nine blades, designed to generate Rankine vortex, was positioned in the circular pipe entrance transparent section with profiled free bell mouth inlet. Two test rigs were built in order to study the turbulent swirl flow generated on the axial fan pressure side in the case of axially unrestricted and restricted swirl flows. One-component laser Doppler anemometry (LDA) and stereo particle image velocimetry (SPIV) were used in the first test rig in the measuring section 3.35D, measured from the test rig inlet. One of the latest measurement techniques, high speed SPIV (HSS PIV), was used for the measurements in the second test rig in the section 2.1D downstream the fan’s trailing edge. Achieved Reynolds numbers in the first test rig are Re = 182600 and 277020, while in the second Re = 186463. Turbulent velocity field non-homogeneity and anisotropy is revealed using the LDA system. Calculated turbulent statistical properties, such as moments of the second and higher orders, reveal complex mechanisms in turbulent swirl flow. It is shown for the used axial fan construction that swirl number has almost constant value for two various duty points generated by changing rotation number. Study of the instant and mean velocity fields obtained using SPIV discovers vortex core dynamics. Obtained percentage of the unique positions of the total velocity minimum are 10% for the first regime, while 11.5% for the second regime in the first test rig. HSS PIV experimental results have also shown the three-dimensionality and non-homogeneity of generated turbulent swirl flow. Experimentally determined and calculated invariant maps revealed three-component isotropic turbulence in the vortex core region.

Near-Wall Measurements in Turbulent Boundary Layers Using Laser Doppler Anemometry

2002 ◽  
Author(s):  
T. Gunnar Johansson ◽  
Luciano Castillo
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Near Wall

Near wall measurements have been performed in a zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers using Laser-Doppler Anemometry in order to investigate how accurately the wall shear stress can be determined. Also, scaling problems are particularly difficult at low Reynolds numbers since they involve simultaneous influences of both inner and outer scales and this is most clearly observed in the near-wall region. In order to fully describe the zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers it is necessary to accurately measure a number of quantities. These include the mean velocity and Reynolds stresses, and their spatial derivatives all the way down to the wall (y+∼1). Integral parameters that need to be measured are the wall shear stress and boundary layer thickness, particularly the momentum thickness. Problems with the measurement of field properties get worse close to a wall, and they get worse for increasing local Reynolds number. Three different approaches to measure the wall shear stress were examined. It was found that small measurement errors in the mean velocity close to the wall significantly reduced the accuracy in determining the wall shear stress by measuring the velocity gradient at the wall. The constant stress layer was found to be affected by the advection terms. However, it was found that taking the small pressure gradient into account and improving on the spatial resolution in the outer part of the boundary layer made the momentum integral method reliable.

scholarly journals The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct

1994 ◽  
Author(s):  
K. M. Britchford ◽  
J. F. Carrotte ◽  
S. J. Stevens ◽  
J. J. McGuirk
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Anemometry ◽  
Reynolds Shear Stress ◽  
Turbulence Models ◽  
Test Facility ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Curvature Effects ◽  
The Mean

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.

Diffusive turbulence in a confined jet experiment

1997 ◽  
Vol 337 ◽  
pp. 233-261 ◽  
Author(s):  
FRÉDÉRIC RISSO ◽  
JEAN FABRE
Keyword(s):  
Laser Doppler Anemometry ◽  
Pressure Fluctuations ◽  
Mean Flow ◽  
Radial Profiles ◽  
Closed Tube ◽  
Residual Motion ◽  
Velocity Decay ◽  
Self Similar ◽  
The Mean ◽  
Axisymmetrical Jet

An experimental analysis of the turbulence in an axisymmetrical jet within a closed tube is presented. At some distance from the nozzle, a turbulent region develops, where the kinetic energy of the mean flow almost vanishes. In this region, the turbulence is transported by turbulent diffusion and its energy decreases with the distance from the inlet. A complete description of the flow field has been achieved using laser Doppler anemometry. Some unusual features are highlighted: the statistical moments of the velocity decay exponentially, the integral length scales remain constant, the radial profiles are self-similar and the Reynolds stress tensor is isotropic and homogeneous in the radial direction. These results highlight the roles of pressure fluctuations and any mean residual motion in the return to isotropy.

Diffusion characteristics of a plane jet discharged in a wavy crossflowing stream

2004 ◽  
Vol 218 (4) ◽  
pp. 411-423 ◽  
Author(s):  
A A Abdel-Rahman ◽  
M E Eleshaky
Keyword(s):  
Laser Doppler Anemometry ◽  
Rapid Development ◽  
Water Channel ◽  
Mean Velocity ◽  
Diffusion Characteristics ◽  
Crossflow Velocity ◽  
Jet Nozzle ◽  
The Mean ◽  
Plane Jet ◽  
The Waves

an experimental investigation has been undertaken to study the effect of a wavy crossflow on a plane jet discharged vertically downwards in a water channel. Two groups of experiments were performed: one group for a jet discharged into a uniform crossflow; the second group for a jet discharged into a wavy crossflow. Experiments were conducted for four jet-to-crossflow-velocity ratios. For each experiment, measurements using a laser Doppler anemometry system were made at six stations downstream of the exit of the jet nozzle. During the course of the experiments, the channel flow velocity was maintained fairly constant, and the wave generated in the channel was not very steep. The results revealed that the oscillatory motion associated with the waves has a significant effect on both the mean and the turbulent velocity fields. The mean velocity profiles were found to have no maximum value, compared with those of a uniform crossflow. The effect was most pronounced in the zone of flow establishment, where a region of intense fluid mixing arises, resulting in a significant shortening of the zone and a rapid development of the jet flow.

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