Natural convection in a closed domain STILL NEEDING help!

Yr0gErG · March 28, 2011, 08:44

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

Yr0gErG · March 28, 2011, 08:44

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

arunbollavarapu · February 6, 2012, 13:23

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

yashganatra · June 12, 2013, 03:12

Refer literature. Boussinesq is valid for a max temp difference of 20 deg celsius.

maiminh0110 · December 2, 2019, 01:04

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

March 28, 2011, 08:44	Natural convection in a closed domain STILL NEEDING help!	#1
Yr0gErG 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

February 6, 2012, 13:23	modeling ventilation of a room (only cosidering buoyancy forces due to temp grad)	#3
arunbollavarapu New Member arun b Join Date: Feb 2012 Posts: 2 Rep Power: 0	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

December 2, 2019, 01:04	modeling convection and buoyancy in fluent	#5
maiminh0110 New Member mai Minh Join Date: Nov 2019 Posts: 5 Rep Power: 7	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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June 12, 2013, 03:12		#4
yashganatra 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.