Measurement of Laminar Flow Development in a Square Duct Using a Laser-Doppler Flowmeter

1967 ◽  
Vol 34 (4) ◽  
pp. 813-818 ◽  
Author(s):  
R. J. Goldstein ◽  
D. K. Kreid
Keyword(s):  
Laminar Flow ◽  
Precision Measurement ◽  
Fluid Velocity ◽  
Flow Distribution ◽  
Flow Region ◽  
Optical Technique ◽  
Fully Developed Flow ◽  
Square Duct ◽  
Flow Development ◽  
Doppler Flowmeter

A system for precision measurement of fluid velocity is developed and applied to determine the laminar flow distribution in a square duct. The experimental technique consists of measuring the Doppler shift of laser radiation scattered by particles moving with the fluid. From this frequency shift, the fluid velocity is inferred. Measurements in the entrance region and fully developed flow region of a square duct indicate that the velocity profile development takes place in a somewhat longer section of the duct than had been predicted. Measurements of the fully developed flow indicate that the optical technique used is capable of measuring velocity within an accuracy of at least 0.1 percent.

Supersonic laminar flow development in a square duct

AIAA Journal ◽  
1987 ◽  
Vol 25 (1) ◽  
pp. 175-177 ◽  
Author(s):  
D. O. Davis ◽  
F. B. Gessner ◽  
G. D. Kerlick
Keyword(s):  
Laminar Flow ◽  
Square Duct ◽  
Flow Development ◽  
Supersonic Laminar

Application of CFD Model for Inlet Flow Region of 17×17 Fuel Assembly

2006 ◽  
Author(s):  
Milorad B. Dzodzo ◽  
Bin Liu ◽  
Pablo R. Rubiolo ◽  
Zeses E. Karoutas ◽  
Michael Y. Young
Keyword(s):  
Fuel Assembly ◽  
Fluid Dynamic ◽  
Flow Distribution ◽  
Flow Region ◽  
Fretting Wear ◽  
Jet Flows ◽  
Cfd Model ◽  
Lateral Velocity ◽  
Fuel Assemblies ◽  
Inlet Conditions

A numerical investigation was performed to study the variation in axial and lateral velocity profiles occurring downstream of the inlet nozzle of a typical Westinghouse 17×17 PWR fuel assembly. A Computational Fluid Dynamic (CFD) model was developed with commercial CFD software. The model comprised the lower region of the fuel assembly, including: the Debris Filter Bottom Nozzle (DFBN), P-grid, Bottom Inconel grid, one and half grid span, as well as the lower core plate hole. The purpose of the study was to obtain insight into the flow redistribution resulting from the interaction of the jet arising from the lower core plate hole and the fuel assembly structure. In particular the axial and lateral velocities before and after the nozzle were studied. The results, axial and lateral velocity contours, streamlines and maximum axial and lateral velocity distributions at various elevations are presented and discussed in relation to the potential risk of high turbulent excitation over the rod and the resulting rod-to-grid fretting-wear damage. The CFD model results indicated that the large jet flows from the lower core plate are effectively dissipated by DFBN nozzle and the grids components of the fuel assembly. The breakup of the large jets in the DFBN and the lower grids helps to reduce the steep velocity gradients and thus the rod vibration and fretting-wear risk in the lower part of the fuel assembly. The presented CFD model is one step towards developing advanced tools that can be used to confirm and evaluate the effect of complex PWR structures on flow distribution. In the future the presented model could be integrated in a larger CFD model involving several fuel assemblies for evaluating the lateral velocities generated due to the non-uniform inlet conditions into the various fuel assemblies.

scholarly journals Biofilm physical structure, internal diffusivity and tortuosity

2005 ◽  
Vol 52 (7) ◽  
pp. 77-84 ◽  
Author(s):  
L.F. Melo
Keyword(s):  
Laminar Flow ◽  
Research Group ◽  
Fluid Velocity ◽  
Physical Structure ◽  
Flow Conditions ◽  
Physical Concept ◽  
Common Trend ◽  
Effective Diffusivities ◽  
Biofilm Structure ◽  
Turbulent Flow Conditions

The paper proposes tortuosity as a physical concept particularly useful to interpret internal diffusivities in terms of biofilm structure. Results from different authors are presented showing how average effective diffusivities in biofilms (measured with inert tracers) vary with the fluid velocity: in the case of biofilms formed under turbulent flow conditions, an increase in fluid velocity corresponds to a decrease in the diffusivity, although sometimes this decrease is very slight; however, in laminar flow situations, no common trend is found from research group to research group.

scholarly journals Fluid–Structure Interaction and Flow Redistribution in Membrane-Bounded Channels

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4259 ◽  
Author(s):  
Giuseppe Battaglia ◽  
Luigi Gurreri ◽  
Andrea Cipollina ◽  
Antonina Pirrotta ◽  
Svetlozar Velizarov ◽  
...  
Keyword(s):  
Fluid Velocity ◽  
Fluid Structure Interaction ◽  
Interaction Model ◽  
Flow Distribution ◽  
Transmembrane Pressure ◽  
Hydraulic Permeability ◽  
Fluid Structure ◽  
Membrane Deformation ◽  
Structure Interaction ◽  
Adjacent Channels

The hydrodynamics of electrodialysis and reverse electrodialysis is commonly studied by neglecting membrane deformation caused by transmembrane pressure (TMP). However, large frictional pressure drops and differences in fluid velocity or physical properties in adjacent channels may lead to significant TMP values. In previous works, we conducted one-way coupled structural-CFD simulations at the scale of one periodic unit of a profiled membrane/channel assembly and computed its deformation and frictional characteristics as functions of TMP. In this work, a novel fluid–structure interaction model is presented, which predicts, at the channel pair scale, the changes in flow distribution associated with membrane deformations. The continuity and Darcy equations are solved in two adjacent channels by treating them as porous media and using the previous CFD results to express their hydraulic permeability as a function of the local TMP. Results are presented for square stacks of 0.6-m sides in cross and counter flow at superficial velocities of 1 to 10 cm/s. At low velocities, the corresponding low TMP does not significantly affect the flow distribution. As the velocity increases, the larger membrane deformation causes significant fluid redistribution. In the cross flow, the departure of the local superficial velocity from a mean value of 10 cm/s ranges between −27% and +39%.

scholarly journals Laminar Mixing in Stirred Tank Agitated by an Impeller Inclined

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Koji Takahashi ◽  
Yoshiharu Sugo ◽  
Yasuyuki Takahata ◽  
Hitoshi Sekine ◽  
Masayuki Nakamura
Keyword(s):  
Numerical Simulation ◽  
Laminar Flow ◽  
Mixing Time ◽  
Flow Region ◽  
Experimental Results ◽  
Stirred Tank ◽  
Simulation Methods ◽  
Mixing Performance ◽  
Laminar Mixing ◽  
Numerical Simulation Methods

The mixing performance in a vessel agitated by an impeller that inclined itself, which is considered one of the typical ways to promote mixing performance by the spatial chaotic mixing, has been investigated experimentally and numerically. The mixing time was measured by the decolorization method and it was found that the inclined impeller could reduce mixing time compared to that obtained by the vertically located impeller in laminar flow region. The effect of eccentric position of inclined impeller on mixing time was also studied and a significant reduction of mixing time was observed. To confirm the experimental results, the velocity profiles were calculated numerically and two novel numerical simulation methods were proposed.

CFD Study of Pitch Variations On Helically Coiled Pipe in Laminar Flow Region

2020 ◽  
Author(s):  
Anwer Faraj ◽  
Itimad D J Azzawi ◽  
Samir Ghazi Yahya ◽  
Amer Al-damook
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Region ◽  
Alternative Solution ◽  
Experimental Investigations ◽  
Coil Diameter ◽  
Computational Fluid Dynamics Cfd

Abstract Experimental investigations of the flows inside helically coiled pipe are difficult and may also be expensive, particularly for small diameters. Computational fluid dynamics (CFD) packages, which can easily construct the geometry and change the dimensions with 100% of accuracy, provide an alternative solution for the experimental difficulties and uncertainties. Therefore, a computational fluid dynamics (CFD) study was conducted to analyse the flow structure and the effect of varying the coil pitch on the coil friction factor, through utilising different models' configurations. Two coils were tested, all of them sharing the same pipe and coil diameter: 0.005m and 0.04m respectively. Pitch variations began with 0.01 and 0.05 m for the first, second model respectively. In this study, the velocity was analysed, and the effects of this reduction on coil friction factor were also examined using laminar flow. The results were validated by Ito's equation for the laminar flow.

1102 On the Growth of Oblique T-S waves in Laminar Flow Region around a Turbulence Wedge Induced by Jet Injection(2)

2006 ◽  
Vol 2006 (0) ◽  
pp. _1102-1_-_1102-4_
Author(s):  
Tsuneo AZUMA ◽  
Kensuke MARUYAMA ◽  
Yusuke YAMAMOTO ◽  
Hiroki INATANI
Keyword(s):  
Laminar Flow ◽  
Flow Region ◽  
Jet Injection ◽  
S Waves

Study on the Calculation Method of Gas Flow in Vacuum System Based on the Fluent Software

2010 ◽  
Vol 29-32 ◽  
pp. 1425-1429
Author(s):  
Shi Wei Zhang ◽  
Jin Ce Liu ◽  
Guang Zhe Song ◽  
Zhi Jun Zhang
Keyword(s):  
Laminar Flow ◽  
Calculation Method ◽  
Gas Flow ◽  
Volume Flow Rate ◽  
Fluid Velocity ◽  
Vacuum Field ◽  
Transitional Flow ◽  
Vacuum System ◽  
Continuity Hypothesis ◽  
Fluent Software

In order to improve the calculation method of the vacuum system design, the research focus on the way applying the Fluent software to calculation of gas flow in vacuum system in this paper. It is proved that the permission pressure lower limit is 1Pa for meeting the continuity hypothesis. The applicable flow patterns include turbulent flow, laminar flow and transitional flow between turbulent and laminar flow, which are totally defined as the viscous flow in the traditional vacuum field. By means of user define function (UDF), a layer mesh cell of negative quality source is defined to simulate the constant volume flow rate at the inlet of positive displacement vacuum pump, which makes up for the lack of compressible fluid velocity outlet boundary conditions in Fluent. The usability of Fluent in vacuum system is confirmed by a successful calculating example of gas flow in an ice condenser of vacuum freeze dryer.

Numerical Investigation of the Circle Grids Fractal Flow Conditioner for Orifice Plate Flowmeters

2012 ◽  
Vol 229-231 ◽  
pp. 700-704 ◽  
Author(s):  
Bukhari Manshoor ◽  
Amir Khalid
Keyword(s):  
Flow Rate ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Orifice Plate ◽  
Measuring Error ◽  
Flow Distortion ◽  
Flow Meters ◽  
Flow Development ◽  
Computational Flow Dynamics ◽  
Pipe Fittings

Flow rate measurements are among the most important operations in modern industries dealing with increasingly expensive fluids such as petroleum, natural gas and water. The accuracy of flow meters depends mainly on their position in a pipe network and their operating conditions. Pipe fittings such as valves and bends generate turbulence and swirl and distort the flow distribution in the pipe, leading to a substantial amount of measuring error. For accurate flow rate measurements, the standards ISO 5167 specify either a sufficient straight piping lengths or the inclusion of a flow conditioner between the flow distortion and the flow meter. Flow conditioners serve to reduce the developing length between pipe fittings and flow meters and to create fully developed flow condition within short distances. In the present study, numerical modeling of the flow development upstream and downstream of the orifice plate which used circle grid fractal flow conditioner has been made. Computational Flow Dynamics techniques have been used to predict the flow development downstream the flow conditioners.

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