Flow-Field Prediction in Submerged and Confined Jet Impingement Using the Reynolds Stress Model

1999 ◽  
Vol 121 (4) ◽  
pp. 255-262 ◽  
Author(s):  
G. K. Morris ◽  
S. V. Garimella ◽  
J. A. Fitzgerald
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reynolds Stress ◽  
Reynolds Numbers ◽  
Reynolds Stress Model ◽  
Nozzle Diameter ◽  
Stress Model ◽  
Target Plate ◽  
Plate Spacing ◽  
Numerical Predictions

The flow field of a normally impinging, axisymmetric, confined and submerged liquid jet is predicted using the Reynolds Stress Model in the commercial finite-volume code FLUENT. The results are compared with experimental measurements and flow visualizations and are used to describe the position of the recirculating toroid in the outflow region which is characteristic of the confined flow field. Changes in the features of the recirculation pattern due to changes in Reynolds number, nozzle diameter, and nozzle-to-target plate spacing are documented. Results are presented for nozzle diameters of 3.18 and 6.35 mm, at jet Reynolds numbers in the range of 2000 to 23,000, and nozzle-to-target plate spacings of 2, 3, and 4 jet diameters. Up to three interacting vortical structures are predicted in the confinement region at the smaller Reynolds numbers. The center of the primary recirculation pattern moves away from the centerline of the jet with an increase in Reynolds number, nozzle diameter, and nozzle-to-target plate spacing. The computed flow patterns were found to be in very good qualitative agreement with experiments. The radial location of the center of the primary toroid was predicted to within ±40 percent and ±3 percent of the experimental position for Re = 2000–4000 and Re = 8500–23000, respectively. The magnitude of the centerline velocity of the jet after the nozzle exit was computed with an average error of 6 percent. Reasons for the differences between the numerical predictions at Re = 2000–4000 and experiments are discussed. Predictions of the flow field using the standard high-Reynolds number k-ε and renormalization group theory (RNG) k-ε models are shown to be inferior to Reynolds stress model predictions.

scholarly journals Computation of Turbulent Heat Transfer on the Walls of a 180 Degree Turn Channel With a Low Reynolds Number Reynolds Stress Model

2002 ◽  
Author(s):  
D. L. Rigby ◽  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Stress ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Stress Model ◽  
Generalized Gradient ◽  
Low Reynolds

The Low Reynolds number version of the Stress-ω model and the two equation k-ω model of Wilcox were used for the calculation of turbulent heat transfer in a 180 degree turn simulating an internal coolant passage. The Stress-ω model was chosen for its robustness. The turbulent thermal fluxes were calculated by modifying and using the Generalized Gradient Diffusion Hypothesis. The results showed that using this Reynolds Stress model allowed better prediction of heat transfer compared to the k-ω two equation model. This improvement however required a finer grid and commensurately more CPU time.

scholarly journals Analysis of Separated Flows Inside an Annular Compressor Cascade Using a Low-Re-Number k-ϵ and an Algebraic Reynolds-Stress-Model

1997 ◽  
Author(s):  
Jürgen R. Lücke ◽  
Heinz E. Gallus
Keyword(s):  
Flow Field ◽  
Reynolds Stress ◽  
Three Dimensional ◽  
Separated Flow ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Mean Flow ◽  
Compressor Cascade ◽  
Production Term ◽  
Algebraic Reynolds Stress Model

The flow field inside an annular compressor cascade is numerically investigated. The mean flow features are complex three-dimensional zones of turbulent separation at hub and shroud at high inflow angles. The flow field is investigated with an implicit three-dimensional Navier-Stokes code. To predict turbulent effects the flow solver includes two different variants of a Low-Re-number k-ϵ-model and an algebraic Reynolds-stress-model. Using the Low-Re-number model the structure of the regions of separated flow are fairly well predicted. However, intensity and size of these zones are too small compared with the experimental data. Better results are produced using the anisotropic algebraic Reynolds-stress-model combined with a stagnation point modification of the turbulent production term. Stucture and intensity of the vortex systems are simulated in more detail. Static pressure distributions and loss contours are in a very good agreement with the experiments.

Liquid Jet Impingement Without and With Heat Transfer

2009 ◽  
Author(s):  
F. A. Jafar ◽  
G. R. Thorpe ◽  
O¨. F. Turan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Liquid Jet ◽  
Substantial Impact ◽  
Plate Spacing ◽  
Numerical Predictions ◽  
Surface Configuration

Equipment used to cool horticultural produce often involves three-phase porous media. The flow field and heat transfer processes that occur in such equipment are generally quantified by means of empirical relationships amongst dimensionless groups. This work represents a first step towards the goal of harnessing the power of computational fluid dynamics (CFD) to better understand the heat transfer process that occur in beds of irrigated horticultural produce. The primary objective of the present study is to use numerical predictions towards reducing energy and cooling water requirement in cooling horticultural produce. In this paper, flow and heat transfer predictions are presented of a single slot liquid jet on flat and curved surfaces using a CFD code (FLUENT) for 2-D configurations. The effects of Reynolds number, nozzle to plate spacing, nozzle width and target surface configuration have been studied. Reynolds numbers of 250, 500, 700, 1800 and 1900 are studied where the liquid medium is water. Here, the Reynolds number is defined in terms of the hydraulic nozzle diameter, inlet jet velocity and fluid kinematic viscosity. The results show that Reynolds numbers, nozzle to plate spacing and nozzle width have a significant effect on the flow filed and heat transfer characteristics; whereas the target surface configuration at stagnation area has no substantial impact. The use of a numerical tool has enabled detailed investigation of these characteristics, which have not been available in the literature previously.

A Reynolds-Stress Model for Near-Wall and Low-Reynolds-Number Regions

1988 ◽  
Vol 110 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Nobuyuki Shima
Keyword(s):  
Reynolds Number ◽  
Reynolds Stress ◽  
Present Model ◽  
Transport Model ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulence Energy ◽  
Stress Model ◽  
Low Reynolds ◽  
Near Wall

The Reynolds stress model for high Reynolds numbers proposed by Launder et al. is extended to near-wall and low-Reynolds-number regions. In the development of the model, particular attention is given to the high anisotropy of turbulent stresses in the immediate vicinity of a wall and to the behavior of the exact stress equation at the wall. A transport model for the turbulence energy dissipation rate is also developed by taking into account its compatibility with the stress model at the wall. The model and the low-Reynolds-number model of Hanjali’c and Launder are applied to fully-developed pipe flow. Comparison of the numerical results with Laufer’s data shows that the present model gives significantly improved predictions. In particular, the present model is shown to reproduce the sharp peak in the distribution of the streamwise turbulence intensity in the immediate vicinity of the wall.

scholarly journals Turbulence Models for Single Phase Flow Simulation of Cyclonic Flotation Columns

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 464 ◽  
Author(s):  
Shiqi Meng ◽  
Xiaoheng Li ◽  
Xiaokang Yan ◽  
Lijun Wang ◽  
Haijun Zhang ◽  
...  
Keyword(s):  
Flow Field ◽  
Reynolds Stress ◽  
Single Phase ◽  
Flow Fields ◽  
Reynolds Stress Model ◽  
Measured Data ◽  
Stress Model ◽  
Model Simulations ◽  
Flotation Columns ◽  
Cyclonic Flow

Cyclonic fields are important for cyclonic static microbubble flotation columns (FCSMCs), one of the most important developments in column flotation technology, particularly for separation of fine particles, where the internal flow field has enormous influence on flotation performance. PIV (particle image velocimetry) and CFD (computational fluid dynamics) are the most effective methods to study flow fields. However, data is insufficient for FCSMC flow fields and similar cyclonic equipment, with turbulence model simulations producing different views to measured data. This paper employs an endoscope and PIV to measure axial and cross sections for single-phase swirling flow fields in FCSMCs. We then compare various turbulence model simulations (Reynolds stress model (RSM), standard k-ε, realizable k-ε, and RNG (renormalization group) k-ε) to the measured data. The RSM (Reynolds stress model) predicts cyclonic flow field best in flotation columns with 16.22% average relative velocity deviation. Although the realizable k-ε model has less than 30% relative deviation in radial and tangential directions, axial deviations reach 78.11%. Standard k-ε and RNG k-ε models exhibited approximately 40% and 30% radial and tangential deviation, respectively, and cannot be used even for trend predictions for axial velocity. k-ε models are based on isotropic assumptions with semi-empirical formulas summarized from experiments, whereas RSM fundamentally considers laminar flow and Reynolds stress, and hence is more suitable for anisotropic performance. This study will contribute to flotation column and other cyclonic flow field equipment research.

scholarly journals Reynolds Stress Model for Viscoelastic Drag-Reducing Flow Induced by Polymer Solution

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1659 ◽  
Author(s):  
Wang
Keyword(s):  
Polymer Solution ◽  
Reynolds Stress ◽  
Reynolds Numbers ◽  
Reynolds Stress Model ◽  
Computational Time ◽  
Stress Model ◽  
Turbulent Model ◽  
Mean Velocity ◽  
Conformation Tensor ◽  
Computational Ability

Viscoelasticity drag-reducing flow by polymer solution can reduce pumping energy of pipe flow significantly. One of the simulation manners is direct numerical simulation (DNS). However, the computational time is too long to accept in engineering. Turbulent model is a powerful tool to solve engineering problems because of its fast computational ability. However, its precision is usually low. To solve this problem, we introduce DNS to provide accurate data to construct a high-precision turbulent model. A Reynolds stress model for viscoelastic polymer drag-reducing flow is established. The rheological behavior of the drag-reducing flow is described by the Giesekus constitutive Equation. Compared with the DNS data, mean velocity, mean conformation tensor, drag reduction, and stresses are predicted accurately in low Reynolds numbers and Weissenberg numbers but worsen as the two numbers increase. The computational time of the Reynolds stress model (RSM) is only 1/120,960 of DNS, showing the advantage of computational speed.

Prediction of strongly curved turbulent duct flows with Reynolds stress model

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 91-98
Author(s):  
Jiang Luo ◽  
Budugur Lakshminarayana
Keyword(s):  
Reynolds Stress ◽  
Reynolds Stress Model ◽  
Stress Model
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