31
Fluent / Re: Histogram plot in DPM
« on: April 27, 2012, 08:43:36 AM »
The time variable on the x-axis will give you residence time of the particles passing through that plane.
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32
Fluent / Re: How can I calculate time-average velocity in transient simulation?
« on: April 25, 2012, 11:10:47 AM »
You will need to save the data files at regular time intervals, say after every 5 time steps. Now we may at times need to find the "average solution" for the past "n" timesteps from the data files that have already been saved.
The attached User Defined Function (UDF) and Scheme utility will help you to do this.
Example Problem:
The user has iterated the case till timestep no. 200, saving files after every 10 timesteps. Now if the user wants to see the average solution for timesteps 50 to 120 then the attached Scheme utility will load the appropriate data files, call the UDF to find the average of velocity, pressure and turbulence parameters and pass them on to FLUENT. The user will have to save this new averaged data with a new name in order to avoid overwriting the last data.
To use this Scheme utility and UDF, you need to ensure that the data files are saved with appropriate name. A correct naming convention would be "string-x.dat.gz"
std-00020.dat.gz
std-00030.dat.gz
std-00040.dat.gz
Here "std-" is the initial string in the file name, "00x" is the timestep number added as an extension, so that the Scheme utility can recognize the appropriate data file.The usage instructions can be found in the "scm-file.scm" file which you can read using notepad or any text editor.
The attached User Defined Function (UDF) and Scheme utility will help you to do this.
Example Problem:
The user has iterated the case till timestep no. 200, saving files after every 10 timesteps. Now if the user wants to see the average solution for timesteps 50 to 120 then the attached Scheme utility will load the appropriate data files, call the UDF to find the average of velocity, pressure and turbulence parameters and pass them on to FLUENT. The user will have to save this new averaged data with a new name in order to avoid overwriting the last data.
To use this Scheme utility and UDF, you need to ensure that the data files are saved with appropriate name. A correct naming convention would be "string-x.dat.gz"
std-00020.dat.gz
std-00030.dat.gz
std-00040.dat.gz
Here "std-" is the initial string in the file name, "00x" is the timestep number added as an extension, so that the Scheme utility can recognize the appropriate data file.The usage instructions can be found in the "scm-file.scm" file which you can read using notepad or any text editor.
33
Fluent / Re: How can I copy my case settings from one case to new case?
« on: April 25, 2012, 10:26:52 AM »
Save all currently defined boundary conditions to a file, enter the write-bc text command and specify a name for the file.
file -> write-bc
FLUENT writes the boundary conditions, the solver, and model settings to a file using the same format as the "zone'' section of the case file.
To read boundary conditions from a file and to apply them to the corresponding zones in your model, enter the read-bc text command.
file -> read-bc
FLUENT sets the boundary conditions in the current model by comparing the zone name associated with each set of conditions in the file with the zone names in the model. If the model does not contain a matching zone name for a set of boundary conditions, those conditions are ignored.
If you read boundary conditions into a model that contains a different mesh topology (e.g., a cell zone has been removed), check the conditions at boundaries within and adjacent to the region of the topological change. This is important for wall zones.
Note: If the boundary conditions are not checked and some remain uninitialized, the case will not run successfully.
When the read-bc feature is not used, all boundary conditions get the default settings when a mesh file is imported, allowing the case to run with the default values.
If you want FLUENT to apply a set of conditions to multiple zones with similar names, or to a single zone with a name you are not sure of in advance, you can edit the boundary-condition file saved with the write-bc command to include wildcards ( *) within the zone names. For example, if you want to apply a particular set of conditions to wall-12, wall-15, and wall-17 in your current model, edit the boundary-condition file so that the zone name associated with the desired conditions is wall-*.
CAUTION:
1. If you are using SCALE, make sure you scale the new geometry first before reading in the bc file.
2. As a practice, go through the panels to make sure they make sense.
3. You need to do these steps in SERIAL.
file -> write-bc
FLUENT writes the boundary conditions, the solver, and model settings to a file using the same format as the "zone'' section of the case file.
To read boundary conditions from a file and to apply them to the corresponding zones in your model, enter the read-bc text command.
file -> read-bc
FLUENT sets the boundary conditions in the current model by comparing the zone name associated with each set of conditions in the file with the zone names in the model. If the model does not contain a matching zone name for a set of boundary conditions, those conditions are ignored.
If you read boundary conditions into a model that contains a different mesh topology (e.g., a cell zone has been removed), check the conditions at boundaries within and adjacent to the region of the topological change. This is important for wall zones.
Note: If the boundary conditions are not checked and some remain uninitialized, the case will not run successfully.
When the read-bc feature is not used, all boundary conditions get the default settings when a mesh file is imported, allowing the case to run with the default values.
If you want FLUENT to apply a set of conditions to multiple zones with similar names, or to a single zone with a name you are not sure of in advance, you can edit the boundary-condition file saved with the write-bc command to include wildcards ( *) within the zone names. For example, if you want to apply a particular set of conditions to wall-12, wall-15, and wall-17 in your current model, edit the boundary-condition file so that the zone name associated with the desired conditions is wall-*.
CAUTION:
1. If you are using SCALE, make sure you scale the new geometry first before reading in the bc file.
2. As a practice, go through the panels to make sure they make sense.
3. You need to do these steps in SERIAL.
34
Fluent / How can I get particles mean diameters at each cell?
« on: April 25, 2012, 10:08:30 AM »
I am running a Fluent CFD simulation with lagrangian discrete phase particles of varying sizes in a spray. I want to calculate mean particle size/diameter in each cell. Can it be done in Fluent?
Thanks.
Thanks.
35
Fluent / Compiling and Loading FLUENT 14 64-bit UDFs using "FREE" Microsoft Visual Studio
« on: April 10, 2012, 11:17:49 AM »
Just wanted to share guidelines for compiling and loading FLUENT 14 64-bit UDFs using the "FREE" Microsoft Visual Studio 2010 32-bit Express Edition and the 7.1 SDK
See the attached PDf file.
See the attached PDf file.
36
Fluent / Convergence of FLUENT calculations involving combustion and radiation
« on: February 13, 2012, 08:51:16 PM »
Hi,
How can I improve the convergence of FLUENT calculations involving combustion and radiation?
Thanks.
How can I improve the convergence of FLUENT calculations involving combustion and radiation?
Thanks.
37
Fluent / Error: > (greater-than): invalid argument [2]: wrong type [not a number]
« on: February 12, 2012, 12:36:32 PM »
How do I resolve the following error: Error: > (greater-than): invalid argument [2]: wrong type [not a number] Error Object: nan in Fluent?
Thank you.
Thank you.
38
Fluent / How can I compute gradient of VOF simulation
« on: February 08, 2012, 10:17:44 AM »
Hi,
I am carrying out VOF simulation. I want to calculate the gradient VOF. Can any one suggest me how to do this?
Thanks.
I am carrying out VOF simulation. I want to calculate the gradient VOF. Can any one suggest me how to do this?
Thanks.
39
Fluent / Conjugate heat transfer problem in Fluent 12. Energy residuals are high.
« on: February 06, 2012, 06:34:36 PM »
Hello,
I have a conjugate heat transfer problem in Fluent 12.0. The energy residuals do not converge. What could be the cause and how do I get it converged?
Thank you.
I have a conjugate heat transfer problem in Fluent 12.0. The energy residuals do not converge. What could be the cause and how do I get it converged?
Thank you.
40
Fluent / What is Swirl fraction in the hollow cone injection in Fluent?
« on: February 04, 2012, 06:32:06 PM »
Hi,
How does the swirl fraction impact the hollow cone spray and how do I define it? Does anyone know?
Thank you.
How does the swirl fraction impact the hollow cone spray and how do I define it? Does anyone know?
Thank you.
41
Fluent / How do I get contour plot of D32 (Sauter Mean diameter) over a plane in Fluent
« on: February 04, 2012, 05:49:36 PM »
Hello,
I want to plot contours of D32 (sauter mean diameter) in Fluent? I am modelling spray simulation.
Thank you.
I want to plot contours of D32 (sauter mean diameter) in Fluent? I am modelling spray simulation.
Thank you.
42
Fluent / Turbulent viscosity limited to viscosity ratio of .... in Fluent
« on: February 04, 2012, 04:36:32 PM »
Hi,
How to resolve the warning message saying that the turbulent viscosity limited to viscosity ratio of 1e5 in 34 cells?
Help.
How to resolve the warning message saying that the turbulent viscosity limited to viscosity ratio of 1e5 in 34 cells?
Help.
43
Fluent / I am getting divergence on the first iteration for an axisymmetric problem?
« on: February 04, 2012, 04:21:53 PM »
I am running a 2d axisymmetric simulation but it diverges on the first iteration with the following message:
Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!
Error: Divergence detected in AMG solver: x-momentum
Error Object: #f
Help me please.
Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!
Error: Divergence detected in AMG solver: x-momentum
Error Object: #f
Help me please.
44
Fluent / DPM concentration in a cell using Fluent UDF
« on: February 02, 2012, 04:11:18 PM »
Hi,
I am working on modelling of heat transfer from the discrete phase (lagrangian) to the continuous phase. I need to find out the concentration of the discrete phase in the cells. Based on the concentration, I can modify the equation used for heat transfer between the two phases. Because when the particles are moving very close to each other, the effective heat transfer coefficient will be very different from the heat transfer coefficient of a single particle.
Could any one here also tell me about the literature in dealing with heat transfer from spherical particles that are closely spaced?
Thank you.
I am working on modelling of heat transfer from the discrete phase (lagrangian) to the continuous phase. I need to find out the concentration of the discrete phase in the cells. Based on the concentration, I can modify the equation used for heat transfer between the two phases. Because when the particles are moving very close to each other, the effective heat transfer coefficient will be very different from the heat transfer coefficient of a single particle.
Could any one here also tell me about the literature in dealing with heat transfer from spherical particles that are closely spaced?
Thank you.
45
Fluent / How many particle tracks do I need for discrete particle tracking in CFD?
« on: January 27, 2012, 09:45:53 AM »
Hi,
I am a beginner in multiphase simulation using Lagrangian approach. How do I know how many particles do I need to have a representative particle trajectory in the simulation? Does it depend on the mass flow of the particles? Does each particle represent its own mass of single particle or is it the total mass flow of the particles divided by the number of particle tracks?
Please help.
Many thanks.
I am a beginner in multiphase simulation using Lagrangian approach. How do I know how many particles do I need to have a representative particle trajectory in the simulation? Does it depend on the mass flow of the particles? Does each particle represent its own mass of single particle or is it the total mass flow of the particles divided by the number of particle tracks?
Please help.
Many thanks.