Doubt in execution of program

[Ankit Patil]

I am an engineering student from India. I am learning FDS  myself.  

Sir, I need your help in this matter. I want to use multiple fuel reactions with burn away solid fuel. 

Please check in attachment, I am sending you my FDS file (txt), error message and vegetation model. The block is represented as burn away fuel but it cannot work. How can I make this possible to run? What kind of changes do I have to make?

Aim is to make this obstacle burn away invisible by using this running fire.

Best regards,

Ankit Patil 

[dr_jfloyd]

The error message is for forest42 and you have attached 40 and 41. The error message is telling you that if you are using simple chemistry (REAC with C,H,O, and/or N) then you cannot have more than one REAC input. Does the input for forest42 have more than one REAC input?  If so the solution is to either use just one REAC or use complex chemistry where you define the entire reaction (See the User's Guide).

[Ankit Patil]

Yes sir input of forest 42 have more than one reaction. But in forest 40 and 41 the obstacle is not invisible after it touches fire. I want it to burn away. I considered the obstacle as a foam. Fire passes but its not become invisible. How I can be it invisible?

[Ankit Patil]

This is a output video of forest41, please ignore error message in last conversation

[dr_jfloyd]

If you are trying to predict the burning of objects you are doing research. The only ouptut you have for the block is a BNDF file for burning rate. This is not much information for you to analyze to assess what is happening. If you are going to be doing research with FDS, when a simulation doesn't go as expected you need to make sure you have sufficient outputs that you can make an effort to determine on your own what is happening in the simulation.

Looking at you 41 inputs,:

-your foam properties come from the burn_away example cases. These are made up properties for the purpose of having a simple verification case that gets a specific desired result.

-What fuel is your foam block producing and what have you told FDS to do with that fuel?

For an object to disappear with BURN_AWAY, you must consume all the fuel present in a grid cell. For this to happen:

-The line fire must heat the block to a high enough temperature for it to ignite. Is this happening in your case? What surface temperature is the foam block reaching and what surface temperature is required for your reaction to start burning at a meaningful rate?

-If the line fire ignites the foam block, that fire must be capable of sustaining itself once the line fire moves past the block. Is the foam block temperature increasing after ignition, as the line fire moves away do you have heat feedback to the surface where you would expect continued burning. If you have only just barely ignited the block heat losses may cause the flame to go out. Think about holding a hand held propane torch against a large block of wood. You will get some immeadiate burning of the wood, but if you pull the torch away after just a couple of seconds that burning will stop as you won't have heated the block enough for the flame to sustain itself.

[Ankit Patil]

Actually my research is related to forest fire. I will consider the vegetation let us take tree when fir passes through  it, it will burn away from the surface. For this, I am now doing work on FDS. When fire passes it will ignite and burn away. So I consider, a small surface 5*5 m, in that I placed block of methane considered as foam so when fire touches it will auto ignited and burn away. So, In future, I will do survey of forest and make model of simulation. Let us consider 1km forest land, number of trees and other vegetation is included, and spread of fire burnt these vegetation in real looking simulation. that is the objective, to achieve this objective I am preparing for small scale fire simulation. In my forest41 file, the vent is covered by small grass and I placed a foam block of methane. 

So for burn away, should I reduced the fire spread rate? so fire will spread slowly and reduce the that block? Or you have some input files related to forest fires for reference purpose? Your advice is require and beneficial for my project. 

Please check in attachment, I am sending you my output file of forest41  hrr in excel  

[dr_jfloyd]

You need to take the time to add more outputs to your simulation so that you can determine the root cause of why your foam block is not burning. I noted four things to start that you should understand about your simulation.