SDtoolbox

This package aims to (at least partly) reimplement CalTech's Shock and Detonation Toolbox ("sdtoolbox") in Julia.

Focus is put on performance critical parts such as ODE integration. With this in mind, the original SciPy libraries are replaced with Julia's DifferentialEquations.jl. Besides calculation speed improvements, this should also provide more stability for more complex kinetic mechanisms.

Usage

Define initial conditions and select kinetic mechanism:

P₁ = 1e5
T₁ = 300
X₁ = "H2:42, O2:21,N2:79"

# uses the GRI 3.0 kinetic mechanism
mech = "gri30.xml"

Construct Cantera gas objects

SDtoolbox exports direct access to Cantera Python Package via PyCall.jl as ct.

gas₁ = ct.Solution(mech)
gas₁.TPX = T₁,P₁,X₁

Calculate CJ detonation velocity

U₁ = CJspeed(P₁,T₁,X₁,mech)

CJspeed accepts an optional keyword method which defines the algorithm to calculate the Chapman-Jouguet velocity for the given mixture. The two methods proposed by the original sdtoolbox (umin,aeq) are complemented by the algorithm used by the well-established NASA CEARUN. So far, tests reveiled the latter to be the most stable and efficient, which is why CEA is currently the default setting.

Calculate post shock states:

Uses shock relations to calculate a frozen (i.e. no change in composition) state. The equilibrium state is then reached by forcing chemical equilibrium.

gas_fr = PostShock_fr(U₁, P₁, T₁, X₁, mech)
gas_eq = PostShock_eq(U₁, P₁, T₁, X₁, mech)

out = zndsolve(gas,gas₁,U₁,advanced_output=true)

cvsolve(gas)

cell_size(T₁,P₁,X₁,mech)

Future improvements

Since code transfer to Julia is done gradually and there is currently no direct Julia interface for Cantera, this package heavily relies on PyCall. This results in all of the cantera calls to be the most obvious remaining performance bottlenecks, although speedups compared to the pure Python implementation of the sdtoolbox can still be quite significant.

Possible solutions for this could be:

• Wait until there is a native Julia interface for Cantera
• Use the Arrhenius.jl package
• Call Cantera C++ subroutines directly

Additional to dos

• use multiple dispatch on cell_size to calculate CJ speed only when necessary.
• move try-catch from cell_size to CJspeed.