1. Code appears to run but stops abruptly?

• Make sure that there is an inlet and outlet specified even if their default values are all set to zero.
• Ensure that the subfolders are all empty before executing the run. If you have previously attempted to run the code in this directory, some files were automatically created that must be deleted before starting to run again.
• Ensure that "Read Only" is not checked on the properties tag for the subfolders.
• Check the residuals.dat file in the OUTPUT directory for information on the run if available.

• Although there are several criteria for selecting a time step, in any case the time step selected should not exceed the cell length divided by the maximum velocity in that cell neighborhood:
  
• (This criterion is based on the Courant, Freidericks, Levy number -CFL number being smaller than one.) The equation states that a smaller mesh size will result in a smaller required time step. Too small of a time step will result in excessive computational time, while too large of a time step will cause the code to diverge. The user should refine the time step (and mesh size) until convergence is achieved.

• The data for the source term are listed in six columns within the rates.dat file as follows: time (s), MLR (kg/s), HRR (J/s), soot (kg/kg), CO2 (kg/kg), and CO (kg/kg)
• Where MLR = mass loss rate of the fuel, HRR = heat release rate
• Species terms (soot, CO2, CO) are dimensionless since they are normalized by the mass release rate of fuel. In the code the source terms were being renormalized by just the mass release rate of fuel in order to arrive at a species source term in units of kg/s. Note that the source term values in the RATES.DAT file should be thought of as normalized values rather than mass fractions since the sum of mass fractions are typically regarded to equal 1. The source term values in the RATES.DAT file now exceed 1 since the values are not normalized by the total mass in the system (fuel + air).

• The text file called RATES.DAT should be placed in the CODE_FILES directory with a format as described above and should look like the text below. Note that the first number in the first line indicates the number of total rows - in this case, the flaming fire with a duration of 300 seconds.
• 
  300
  

  1	0.00000	4.221186207	0.00000	0.123201367	0.002230761
  2	0.00000	4.351586207	0.00000	0.000000	0.0000000
  3	7.0086E-07	4.537186207	0.00000	0.003048311	0.0000000
  4	1.28563E-06	6.250786207	0.253294655	0.689696307	0.008616213
  5	3.73895E-06	8.576386207	0.034949194	0.171916645	0.003647407

  
  
• The user is able to input any three species of interest after the columns listing time, MLR, and HRR. The only requirement is that the each species release in kg/sec is normalized by the MLR of the fuel in kg/sec. After the sixth column entry in the first data row, a few words of text (i.e. flaming source) are permitted to describe what type of source is contained in the file.

• If the code was downloaded prior to 4/2008, the limit on the number of cells in the domain was 30 x 30 x 40. Creating a domain with a larger number of cells in any direction resulted in a problem with initialization of the arrays. This initialization problem was seen in the first time step results as a discontinuity in the domain values.
  The code was later updated to allow for 40 x 40 x 80 cells in the domain. The code version downloaded after 4/2008 reflects this change. Please note that as the cell size in the domain decreases, the time step should also decrease.

Top of page