11.5 Routine Descriptions

We now briefly discuss some interfaces to the multifluid database that are likely of interest to the user. Many of these routines include optional arguments.

• Multispecies_setProperty This routine sets the value species property. It should be called within the subroutine Simulation_initSpecies for all the species of interest in the simulation problem, and for all the required properties (any of A, Z, N, E, EB, GAMMA).
  FLASH3 Transition: In FLASH2, you could set multiple properties at once in a call to add_fluid_to_db. In FLASH4, individual calls are required. If you are setting up a nuclear network, there is a precoded Simulation_initSpecies to easily initialize all necessary species. It is located in the unit Simulation/SimulationComposition, which must be listed in your simulation Config file.

• Multispecies_getProperty Returns the value of a requested property.

• Multispecies_getSum Returns a weighted sum of a chosen property of species. The total number of species can be subset. The weights are optional, but are typically the mass fractions $X_i$ of each of the fluids at a point in space. In that case, if the selected property (one of $A_i$, $Z_i$, ..., $\gamma_i$) is denoted ${\cal{P}}_i$, the sum calculated is
  $$\sum_i {X_i}{\mathcal{P}_i} \quad.$$

• Multispecies_getAvg Returns the weighted average of the chosen property. As in Multispecies_getSum, weights are optional and a subset of species can be chosen. If the weights are denoted $w_i$ and the selected property (one of $A_i$, $Z_i$, ..., $\gamma_i$) is denoted ${\cal{P}}_i$, the average calculated is
  $$\frac{1}{N} \sum_i^N {w_i}{\mathcal{P}_i} \quad,$$
  where $N$ is the number of species included in the sum; it may be less than the number of all defined species if an average over a subset is requested.

• Multispecies_getSumInv Same as Multispecies_getSum, but compute the weighted sum of the inverse of the chosen property. If the weights are denoted $w_i$ and the selected property (one of $A_i$, $Z_i$, ..., $\gamma_i$) is denoted ${\cal{P}}_i$, the sum calculated is
  $$\sum_i^N \frac{w_i}{\mathcal{P}_i} \quad.$$

  For example, the average atomic mass of a collection of fluids is typically defined by

  $$\frac{1}{\bar{A}} = \sum_i \frac{X_i}{A_i} ,$$ (11.1)

  
  
  where $X_i$ is the mass fraction of species $i$, and $A_i$ is the atomic mass of that species. To compute $\bar{A}$ using the multifluid database, one would use the following lines  
  

  call Multispecies_getSumInv(A, abarinv, xn(:))
        abar = 1.e0 / abarinv
  

  where xn(:) is an array of the mass fractions of each species in FLASH. This method allows some of the mass fractions to be zero.

• Multispecies_getSumFrac Same as Multispecies_getSum, but compute the weighted sum of the chosen property divided by the total number of particles ($A_i$). If the weights give the mass fractions $X_i$ of the fluids at a point in space and the selected property (one of $A_i$, $Z_i$, ..., $\gamma_i$) is denoted ${\cal{P}}_i$, the sum calculated is
  $$\sum_i \frac{X_i}{A_i}{\mathcal{P}_i} \quad.$$

• Multispecies_getSumSqr Same as Multispecies_getSum, but compute the weighted sum of the squares of the chosen property values. If the weights are denoted $w_i$ and the selected property (one of $A_i$, $Z_i$, ..., $\gamma_i$) is denoted ${\cal{P}}_i$, the sum calculated is
  $$\sum_i^N {w_i}{\mathcal{P}_i}^2 \quad.$$

• Multispecies_list List the contents of the multifluid database in a snappy table format.