scholarly journals THREE-DIMENSIONAL NUMERICAL SIMULATION OF A VERTICAL THERMAL TANK

2020 ◽  
Vol 19 (1) ◽  
pp. 97
Author(s):  
G. A. A. Moreira ◽  
A. Barbosa ◽  
A. L. Viana ◽  
R. M. Valle
Keyword(s):  
Numerical Simulation ◽  
Temperature Profile ◽  
Transport Model ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Internal Diameter ◽  
Time Step ◽  
External Temperature ◽  
Shear Stress Transport Model ◽  
Temperature Contour

In this study, the results obtained by the numerical simulation presented in this paper are compared with the results obtained experimentally by Oliveski (2000) for a vertical cylindrical thermal reservoir with internal diameter of 0.42m and internal height of 0.57m (79L). In the simulation using Ansys software, for the same parameters of the problem, a study to evaluate the degree of mesh refinement was performed based on the methodology used by Adolfo (2015). The boundary conditions adopted were: Flow: Transient; Buoyancy Model: Boussinesq Approximation; Step of time used: 1s; Wall Condition: Top Non slip / adiabatic; Base: h = 06 [Wm ^ 2 / K]; Lateral: h = 10 [Wm ^ 2 / K]; Initial tank conditions: Null velocity field and initial temperature of approximately 355.15 K. Total simulated flow time: 18,000 s. For the external temperature, contour condition used in the simulation, the ambient temperature was used as a function of time through the graph provided by Oliveski. Three meshes were compared based on the methodology used by Adolfo (2015) in his studies. These have 1,512,143 and 7,997,663, 851,837 and 4,379,079, 271,898 and 1,308,368, number of nodes and elements, respectively. For the turbulence model adopted, the SST (Shear Stress Transport) model was used. The simulations took approximately 58 days to complete. The residue sought in the iterations was at least 0.001, with a maximum of 100 iterations for each time step. For the behavior of the temperature field in the tank over time the formation of the stratified temperature profile was observed, as described in Oliveski's work, and also that the thermal stratification occurs only in the lower region and that in the upper region the water becomes temperature is almost constant. In terms of mean temperature in the tank, the simulation is very close to the results shown by Savicki (2007). However, in terms of temperature profile along the height of the tank, this behavior is shown to be different. Another fact is that the height of the thermocline found in this simulation was considerably higher than that shown in the Savicki simulation. Therefore, the results obtained were validated with the experimental results presented by Oliveski and the numerical results presented by Savicki. It has been confirmed that the mesh with the second refinement level is already sufficiently capable of generating satisfactory results.

scholarly journals Numerical simulation of flow past a heated/cooled sphere

2012 ◽  
Vol 692 ◽  
pp. 332-346 ◽  
Author(s):  
Ryoichi Kurose ◽  
Mamiko Anami ◽  
Akitoshi Fujita ◽  
Satoru Komori
Keyword(s):  
Numerical Simulation ◽  
Temperature Dependence ◽  
Temperature Difference ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Boussinesq Approximation ◽  
Nusselt Numbers ◽  
Flow Past ◽  
Fluid Properties ◽  
Adiabatic Case

AbstractThe characteristics of flow past a heated/cooled sphere are investigated for particle Reynolds numbers $50\leq {\mathit{Re}}_{p} \leq 500$ in conditions with and without buoyancy by means of three-dimensional numerical simulation in which temperature dependence of fluid properties such as density and viscosity is exactly taken into account. The results show that in the absence of buoyancy, drag coefficients of the heated and cooled spheres are larger and smaller than those of the adiabatic case, respectively, and their Nusselt numbers are smaller and larger than the values estimated by a widely used empirical expression for predicting Nusselt numbers, respectively. In addition, the temperature difference between the sphere and ambient fluid strongly affects the flow separation points, size of vortex ring behind the sphere and Strouhal number for vortex shedding. These changes are attributed to the temperature dependence of fluid properties in the vicinity of the sphere. Even in the presence of buoyancy, the temperature dependence of fluid properties strongly affects the drag coefficient and Nusselt number and therefore the Boussinesq approximation becomes inapplicable as the temperature difference increases, regardless of the magnitude of the Richardson number.

scholarly journals Prediction and measurement of the aerodynamic performance of a wind turbine

2018 ◽  
Vol 240 ◽  
pp. 04001
Author(s):  
Ali Cemal Benim ◽  
Michael Diederich ◽  
Fethi Gül
Keyword(s):  
Wind Turbine ◽  
Transport Model ◽  
Three Dimensional ◽  
Detached Eddy Simulation ◽  
Simulation Framework ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Shear Stress Transport Model ◽  
Flow Turbulence ◽  
Good Agreement

Aerodynamic behavior of a small wind turbine is analyzed, both experimentally and numerically. Mainly, an unsteady three-dimensional formulation is adopted, where the flow turbulence is modelled by an Improved Delayed Detached Eddy Simulation framework, using the four-equation transitional Shear Stress Transport model, as the turbulence model. A quite good agreement between the measurements and calculations is observed.

A Parametric Study on Fluid Flow and Heat Transfer in a Printed Circuit Heat Exchanger

2011 ◽  
Author(s):  
Sang-Moon Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Transport Model ◽  
Three Dimensional ◽  
Design Parameters ◽  
Printed Circuit ◽  
Reference Shape ◽  
Shear Stress Transport Model

Numerical analyses for pressure drop and heat transfer in the flow channels of a printed circuit heat exchanger have been performed numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations have been solved in conjunction with the shear stress transport model as a turbulence closure. The numerical solutions are validated with the available experimental results of the reference shape. The effects of two design parameters, namely, the channel angle and the ellipse aspect ratio of the cold channel, on the heat transfer and the friction performance have been evaluated.

Numerical Simulation Study of Soluble and Conservative Liquid Chemicals Diffusion in Tidal River

2013 ◽  
Vol 864-867 ◽  
pp. 1427-1432
Author(s):  
Jian Wei Zhang ◽  
Wan Qing Wu
Keyword(s):  
Numerical Simulation ◽  
Simulation Study ◽  
Hydrodynamic Model ◽  
Moving Boundary ◽  
Transport Model ◽  
Three Dimensional ◽  
Concentration Field ◽  
Pollutant Transport ◽  
Tidal River ◽  
Simulation Results

Based on three-dimensional hydrodynamic model, moving boundary technique and embedded pollutant transport model, the concentration field of the soluble and conservative liquid chemicals spilled into the tidal river was calculated and the chemicals movement around a jetty at DA Liaohe was simulated. By analyzing the simulation results, the chemicals motion law with tide and their concentration field on and in water were deduced.

Comparison between two-dimensional and three-dimensional computational fluid dynamics techniques for two straight-bladed vertical-axis wind turbines in inline arrangement

2018 ◽  
Vol 42 (6) ◽  
pp. 647-664 ◽  
Author(s):  
Saeed Nazari ◽  
Mahdi Zamani ◽  
Sajad A Moshizi
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Two Dimensional ◽  
Dimensional Approach ◽  
Case Scenario ◽  
Worst Case ◽  
Simulation Techniques ◽  
Shear Stress Transport Model ◽  
Dimensional Simulation

This study is dedicated to drawing a comparison between two- and three-dimensional approach capabilities for the simulation of two similar rotors placed in three inline (or tandem) arrangements. This arrangement is generally recognized as the worst-case scenario for the downwind rotor considering the vortices and disorders produced by the upwind rotor. The rotor in question with the diameter of 2.5 m is made up of three NACA0015 blades with the chord length and span size equal to 0.4 and 3 m, respectively. Based on the authors’ previous works, the [Formula: see text] shear stress transport model was selected for this comparative study. According to the results, there is an appreciable deviation in the aerodynamic performance of the upwind rotor predicted by the two-dimensional and three-dimensional simulation techniques. There is no tangible difference between the two-dimensional and three-dimensional results in terms of the averaged power output for the downwind rotor. However, the study of flow field employing different means like vortex structures, axial velocity, and even torque variation indicates that the two-dimensional approach is unable to achieve realistic and reliable output data. The introduced “pillar effect” regarding the dimensional limitations of the two-dimensional approach, which affects the vorticity shape and its dissipation, is plausible evidence for this discrepancy.

Evaluation of RANS Approach in Predicting the Physics of Incompressible Turbulent Jets-Into-Crossflows

2007 ◽  
Author(s):  
Khodyar Javadi ◽  
Mohammad Taeibi-Rahni ◽  
Masoud Darbandi
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Numerical Data ◽  
Turbulent Jets ◽  
Reynolds Stress Model ◽  
Shear Stress Transport Model ◽  
Near Wall

This work is conducted with evaluation of different turbulence models capabilities in predicting three dimensional jet-into-crossflow (JICF) interactions. For this purpose, first of all, comprehensive discussions on the near wall flow complexities due to discharge of a jet into a crossflow are presented. In this regards, large scale coherent structures such as: counter rotating vortex pairs (CRVP’s), near wall secondary motions, horseshoe vortices, and wall jets like are discussed. Secondly, the abilities of different turbulence models in predicting such flows (JICF) are evaluated. Our evaluation is based on three points of view including: 1) JICF characteristics, 2) computed location, and 3) sensitivity to different flow variables. In this regard, the turbulence models such as k-ε, k-ω, shear stress transport model (SST), and Reynolds stress model (RSM) are employed. Their related results are compared to credential available experimental/numerical data as well themselves. Since the same basic code with the same grid density as well as numerical discretization scheme is used, it is save to conclude that, any differences in the results are due to the abilities of turbulence models. The flow field computation was governed by Reynolds Averaged Navier-Stokes (RANS) equations performing finite volume method with SIMPLE algorithm over a non-uniform structured grid.

scholarly journals Modelling boundary-layer transition on wings operating in ground effect at low Reynolds numbers

2018 ◽  
Vol 233 (11) ◽  
pp. 2820-2837 ◽  
Author(s):  
LS Roberts ◽  
MV Finnis ◽  
K Knowles
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wind Tunnel ◽  
Transport Model ◽  
Three Dimensional ◽  
Ground Effect ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Shear Stress Transport Model ◽  
Low Reynolds

The transition-sensitive, three-equation k- kL- ω eddy-viscosity closure model was used for simulations of three-dimensional, single-element and multi-element wing configurations operating in close proximity to the ground. The aim of the study was to understand whether the model correctly simulated the transitional phenomena that occurred in the low Reynolds number operating conditions and whether it offered an improvement over the classical fully turbulent k-ω shear stress transport model. This was accomplished by comparing the simulation results to experiments conducted in a 2.7 m × 1.7 m closed-return, three-quarter-open-jet wind tunnel. The model was capable of capturing the presence of a laminar separation bubble on the wing and predicted sectional forces and surface-flow structures generated by the wings in wind tunnel testing to within 2.5% in downforce and 4.1% in drag for a multi-element wing. It was found, however, that the model produced insufficient turbulent kinetic energy during shear-layer reattachment, predicted turbulent trailing-edge separation prematurely in areas of large adverse pressure gradients, and was found to be very sensitive to inlet turbulence quantities. Despite these deficiencies, the model gave results that were much closer to wind-tunnel tests than those given by the fully turbulent k-ω shear stress transport model, which tended to underestimate downforce. Significant differences between the transitional and fully turbulent models in terms of pressure field, wake thickness and turbulent kinetic energy production were found and highlighted the importance of using transitional models for wings operating at low Reynolds numbers in ground effect. The k- kL- ω model has been shown to be appropriate for the simulation of separation-induced transition on a three-dimensional wing operating in ground effect at low Reynolds number.

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