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Natural convection in a closed domain STILL NEEDING help! |
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March 28, 2011, 07:44 |
Natural convection in a closed domain STILL NEEDING help!
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#1 |
New Member
Gregory
Join Date: Mar 2011
Posts: 11
Rep Power: 15 |
Hi FLUENT users, I am trying to model natural convection in a closed car cabin with radiation. Below is the summary of my solution. But the temperature and velocity distributions do not seem to make sense, and the mass flow rate between two arbitrary planes steadily increases with more iterations. Please give me your valuable advise, please!
I would be glad to answer any questions. FLUENT Version: 3d, dp, pbns, rngke (3d, double precision, pressure-based, RNG k-epsilon) Release: 6.3.26 Title: Models ------ Model Settings ----------------------------------------------------------------- Space 3D Time Steady Viscous RNG k-epsilon turbulence model Wall Treatment Standard Wall Functions RNG Differential Viscosity Model Disabled RNG Swirl Dominated Flow Option Disabled Heat Transfer Enabled Solidification and Melting Disabled Radiation None Species Transport Disabled Coupled Dispersed Phase Disabled Pollutants Disabled Pollutants Disabled Soot Disabled Boundary Conditions ------------------- Zones name id type -------------------------------- air 2 fluid outlet 3 wall bottomhalf 4 wall tophalf 5 wall rearwindscreen 6 wall frontwindscreen 7 wall default-interior 9 interior Boundary Conditions air Condition Value ------------------------------------------------------------------ Material Name air Specify source terms? no Source Terms () Specify fixed values? no Local Coordinate System for Fixed Velocities no Fixed Values () Motion Type 0 X-Velocity Of Zone (m/s) 0 Y-Velocity Of Zone (m/s) 0 Z-Velocity Of Zone (m/s) 0 Rotation speed (rad/s) 0 X-Origin of Rotation-Axis (m) 0 Y-Origin of Rotation-Axis (m) 0 Z-Origin of Rotation-Axis (m) 0 X-Component of Rotation-Axis 0 Y-Component of Rotation-Axis 0 Z-Component of Rotation-Axis 1 Deactivated Thread no Laminar zone? no Set Turbulent Viscosity to zero within laminar zone? yes Porous zone? no Conical porous zone? no X-Component of Direction-1 Vector 1 Y-Component of Direction-1 Vector 0 Z-Component of Direction-1 Vector 0 X-Component of Direction-2 Vector 0 Y-Component of Direction-2 Vector 1 Z-Component of Direction-2 Vector 0 X-Component of Cone Axis Vector 1 Y-Component of Cone Axis Vector 0 Z-Component of Cone Axis Vector 0 X-Coordinate of Point on Cone Axis (m) 1 Y-Coordinate of Point on Cone Axis (m) 0 Z-Coordinate of Point on Cone Axis (m) 0 Half Angle of Cone Relative to its Axis (deg) 0 Relative Velocity Resistance Formulation? yes Direction-1 Viscous Resistance (1/m2) 0 Direction-2 Viscous Resistance (1/m2) 0 Direction-3 Viscous Resistance (1/m2) 0 Choose alternative formulation for inertial resistance? no Direction-1 Inertial Resistance (1/m) 0 Direction-2 Inertial Resistance (1/m) 0 Direction-3 Inertial Resistance (1/m) 0 C0 Coefficient for Power-Law 0 C1 Coefficient for Power-Law 0 Porosity 1 Solid Material Name aluminum outlet Condition Value ------------------------------------------------------------- Wall Thickness (m) 0 Heat Generation Rate (w/m3) 0 Material Name aluminum Thermal BC Type 1 Temperature (k) 300 Heat Flux (w/m2) 0 Convective Heat Transfer Coefficient (w/m2-k) 20 Free Stream Temperature (k) 300 Enable shell conduction? no Wall Motion 0 Shear Boundary Condition 0 Define wall motion relative to adjacent cell zone? yes Apply a rotational velocity to this wall? no Velocity Magnitude (m/s) 0 X-Component of Wall Translation 1 Y-Component of Wall Translation 0 Z-Component of Wall Translation 0 Define wall velocity components? no X-Component of Wall Translation (m/s) 0 Y-Component of Wall Translation (m/s) 0 Z-Component of Wall Translation (m/s) 0 External Emissivity 1 External Radiation Temperature (k) 300 Wall Roughness Height (m) 0 Wall Roughness Constant 0.5 Rotation Speed (rad/s) 0 X-Position of Rotation-Axis Origin (m) 0 Y-Position of Rotation-Axis Origin (m) 0 Z-Position of Rotation-Axis Origin (m) 0 X-Component of Rotation-Axis Direction 0 Y-Component of Rotation-Axis Direction 0 Z-Component of Rotation-Axis Direction 1 X-component of shear stress (pascal) 0 Y-component of shear stress (pascal) 0 Z-component of shear stress (pascal) 0 Surface tension gradient (n/m-k) 0 Specularity Coefficient 0 bottomhalf Condition Value ------------------------------------------------------------- Wall Thickness (m) 0 Heat Generation Rate (w/m3) 0 Material Name aluminum Thermal BC Type 2 Temperature (k) 300 Heat Flux (w/m2) 0 Convective Heat Transfer Coefficient (w/m2-k) 20 Free Stream Temperature (k) 300 Enable shell conduction? no Wall Motion 0 Shear Boundary Condition 0 Define wall motion relative to adjacent cell zone? yes Apply a rotational velocity to this wall? no Velocity Magnitude (m/s) 0 X-Component of Wall Translation 1 Y-Component of Wall Translation 0 Z-Component of Wall Translation 0 Define wall velocity components? no X-Component of Wall Translation (m/s) 0 Y-Component of Wall Translation (m/s) 0 Z-Component of Wall Translation (m/s) 0 External Emissivity 1 External Radiation Temperature (k) 300 Wall Roughness Height (m) 0 Wall Roughness Constant 0.5 Rotation Speed (rad/s) 0 X-Position of Rotation-Axis Origin (m) 0 Y-Position of Rotation-Axis Origin (m) 0 Z-Position of Rotation-Axis Origin (m) 0 X-Component of Rotation-Axis Direction 0 Y-Component of Rotation-Axis Direction 0 Z-Component of Rotation-Axis Direction 1 X-component of shear stress (pascal) 0 Y-component of shear stress (pascal) 0 Z-component of shear stress (pascal) 0 Surface tension gradient (n/m-k) 0 Specularity Coefficient 0 tophalf Condition Value ------------------------------------------------------------- Wall Thickness (m) 0 Heat Generation Rate (w/m3) 0 Material Name aluminum Thermal BC Type 2 Temperature (k) 300 Heat Flux (w/m2) 0 Convective Heat Transfer Coefficient (w/m2-k) 20 Free Stream Temperature (k) 300 Enable shell conduction? no Wall Motion 0 Shear Boundary Condition 0 Define wall motion relative to adjacent cell zone? yes Apply a rotational velocity to this wall? no Velocity Magnitude (m/s) 0 X-Component of Wall Translation 1 Y-Component of Wall Translation 0 Z-Component of Wall Translation 0 Define wall velocity components? no X-Component of Wall Translation (m/s) 0 Y-Component of Wall Translation (m/s) 0 Z-Component of Wall Translation (m/s) 0 External Emissivity 1 External Radiation Temperature (k) 300 Wall Roughness Height (m) 0 Wall Roughness Constant 0.5 Rotation Speed (rad/s) 0 X-Position of Rotation-Axis Origin (m) 0 Y-Position of Rotation-Axis Origin (m) 0 Z-Position of Rotation-Axis Origin (m) 0 X-Component of Rotation-Axis Direction 0 Y-Component of Rotation-Axis Direction 0 Z-Component of Rotation-Axis Direction 1 X-component of shear stress (pascal) 0 Y-component of shear stress (pascal) 0 Z-component of shear stress (pascal) 0 Surface tension gradient (n/m-k) 0 Specularity Coefficient 0 rearwindscreen Condition Value ------------------------------------------------------------- Wall Thickness (m) 0 Heat Generation Rate (w/m3) 0 Material Name aluminum Thermal BC Type 4 Temperature (k) 300 Heat Flux (w/m2) 0 Convective Heat Transfer Coefficient (w/m2-k) 0 Free Stream Temperature (k) 300 Enable shell conduction? no Wall Motion 0 Shear Boundary Condition 0 Define wall motion relative to adjacent cell zone? yes Apply a rotational velocity to this wall? no Velocity Magnitude (m/s) 0 X-Component of Wall Translation 1 Y-Component of Wall Translation 0 Z-Component of Wall Translation 0 Define wall velocity components? no X-Component of Wall Translation (m/s) 0 Y-Component of Wall Translation (m/s) 0 Z-Component of Wall Translation (m/s) 0 External Emissivity 1 External Radiation Temperature (k) 340 Wall Roughness Height (m) 0 Wall Roughness Constant 0.5 Rotation Speed (rad/s) 0 X-Position of Rotation-Axis Origin (m) 0 Y-Position of Rotation-Axis Origin (m) 0 Z-Position of Rotation-Axis Origin (m) 0 X-Component of Rotation-Axis Direction 0 Y-Component of Rotation-Axis Direction 0 Z-Component of Rotation-Axis Direction 1 X-component of shear stress (pascal) 0 Y-component of shear stress (pascal) 0 Z-component of shear stress (pascal) 0 Surface tension gradient (n/m-k) 0 Specularity Coefficient 0 |
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March 28, 2011, 07:44 |
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#2 |
New Member
Gregory
Join Date: Mar 2011
Posts: 11
Rep Power: 15 |
frontwindscreen
Condition Value ------------------------------------------------------------- Wall Thickness (m) 0 Heat Generation Rate (w/m3) 0 Material Name aluminum Thermal BC Type 4 Temperature (k) 300 Heat Flux (w/m2) 0 Convective Heat Transfer Coefficient (w/m2-k) 0 Free Stream Temperature (k) 300 Enable shell conduction? no Wall Motion 0 Shear Boundary Condition 0 Define wall motion relative to adjacent cell zone? yes Apply a rotational velocity to this wall? no Velocity Magnitude (m/s) 0 X-Component of Wall Translation 1 Y-Component of Wall Translation 0 Z-Component of Wall Translation 0 Define wall velocity components? no X-Component of Wall Translation (m/s) 0 Y-Component of Wall Translation (m/s) 0 Z-Component of Wall Translation (m/s) 0 External Emissivity 1 External Radiation Temperature (k) 340 Wall Roughness Height (m) 0 Wall Roughness Constant 0.5 Rotation Speed (rad/s) 0 X-Position of Rotation-Axis Origin (m) 0 Y-Position of Rotation-Axis Origin (m) 0 Z-Position of Rotation-Axis Origin (m) 0 X-Component of Rotation-Axis Direction 0 Y-Component of Rotation-Axis Direction 0 Z-Component of Rotation-Axis Direction 1 X-component of shear stress (pascal) 0 Y-component of shear stress (pascal) 0 Z-component of shear stress (pascal) 0 Surface tension gradient (n/m-k) 0 Specularity Coefficient 0 default-interior Condition Value ----------------- Solver Controls --------------- Equations Equation Solved ------------------- Flow yes Turbulence yes Energy yes Numerics Numeric Enabled --------------------------------------- Absolute Velocity Formulation yes Relaxation Variable Relaxation Factor ---------------------------------------------- Pressure 0.3 Density 1 Body Forces 1 Momentum 0.5 Turbulent Kinetic Energy 0.8 Turbulent Dissipation Rate 0.8 Turbulent Viscosity 1 Energy 0.8 Linear Solver Solver Termination Residual Reduction Variable Type Criterion Tolerance ------------------------------------------------------------------------ Pressure V-Cycle 0.1 X-Momentum Flexible 0.1 0.7 Y-Momentum Flexible 0.1 0.7 Z-Momentum Flexible 0.1 0.7 Turbulent Kinetic Energy Flexible 0.1 0.7 Turbulent Dissipation Rate Flexible 0.1 0.7 Energy Flexible 0.1 0.7 Pressure-Velocity Coupling Parameter Value ------------------ Type SIMPLE Discretization Scheme Variable Scheme ----------------------------------------------- Pressure PRESTO! Momentum First Order Upwind Turbulent Kinetic Energy First Order Upwind Turbulent Dissipation Rate First Order Upwind Energy First Order Upwind Solution Limits Quantity Limit --------------------------------------- Minimum Absolute Pressure 1 Maximum Absolute Pressure 5e+10 Minimum Temperature 1 Maximum Temperature 5000 Minimum Turb. Kinetic Energy 1e-14 Minimum Turb. Dissipation Rate 1e-20 Maximum Turb. Viscosity Ratio 100000 Material Properties ------------------- Material: air (fluid) Property Units Method Value(s) ----------------------------------------------------------------------------------- Density kg/m3 incompressible-ideal-gas #f Cp (Specific Heat) j/kg-k constant 1006.43 Thermal Conductivity w/m-k constant 0.0242 Viscosity kg/m-s constant 1.7894001e-05 Molecular Weight kg/kgmol constant 28.966 L-J Characteristic Length angstrom constant 3.711 L-J Energy Parameter k constant 78.6 Thermal Expansion Coefficient 1/k constant 0 Degrees of Freedom constant 0 Speed of Sound m/s none #f Material: aluminum (solid) Property Units Method Value(s) --------------------------------------------------- Density kg/m3 constant 2719 Cp (Specific Heat) j/kg-k constant 871 Thermal Conductivity w/m-k constant 202.4 FLUENT Version: 3d, dp, pbns, rngke (3d, double precision, pressure-based, RNG k-epsilon) Release: 6.3.26 Title: Models ------ Model Settings ----------------------------------------------------------------- Space 3D Time Steady Viscous RNG k-epsilon turbulence model Wall Treatment Standard Wall Functions RNG Differential Viscosity Model Disabled RNG Swirl Dominated Flow Option Disabled Heat Transfer Enabled Solidification and Melting Disabled Radiation None Species Transport Disabled Coupled Dispersed Phase Disabled Pollutants Disabled Pollutants Disabled Soot Disabled Boundary Conditions ------------------- Zones name id type -------------------------------- air 2 fluid outlet 3 wall bottomhalf 4 wall tophalf 5 wall rearwindscreen 6 wall |
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February 6, 2012, 12:23 |
modeling ventilation of a room (only cosidering buoyancy forces due to temp grad)
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#3 |
New Member
arun b
Join Date: Feb 2012
Posts: 2
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hi , iam modeling ventilation of a room , having two windows located on oposite walls, room is square of 3.5m , temp of air in room is 303k , ambient temp is 293k , iam considering 2 domains one is for room another is for atmosphere, boundary conditions taken are interior for windows , pressure inlet for atmospher boundaries , remaning are walls, are these B.C's are sufficient for modeling natural convection taking place because of buoyancy forces ? shall i consider boussinesq approximation ? shall i specify operating density in operating conditions? what should be the density in material panel ? constant,incompressible ideal gas , piecewiseliner,piecewise polynomial,which one shall i take? fluent user guide specified that bossinesq approximation should not be used for my case , if any have idea about specifying density as function of temp . pleeeeeeeeeese help me
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June 12, 2013, 02:12 |
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#4 |
Member
Yash Ganatra
Join Date: Mar 2013
Posts: 67
Rep Power: 13 |
Refer literature. Boussinesq is valid for a max temp difference of 20 deg celsius.
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December 2, 2019, 00:04 |
modeling convection and buoyancy in fluent
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#5 |
New Member
mai Minh
Join Date: Nov 2019
Posts: 5
Rep Power: 6 |
hello everyone, I am in trouble with convection an buoyancy of water depend on gradient of temperature, however, my model is not closure domain. for detail, my model include a hollow cylind, it's heating up itself and it will be dropped down under-water (enclosure in large volume with inlet 0m/s and outlet (operating pressure) ) (under the sea in real life). So when cylind's temperature was increasing, the water inside cylind was heated and descreased in pressure, the water will be moved up by different of pressure.
I want to simulation the descreasing temperature capacity of water when cylind be heated, but i wasn't found anyway to modeling this physical action, i thought that i was wrong in the set up geometry or boundary conditions. So i very appriciate of your help |
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