PDESystem & MOL

[BLI]

I’m trying to formulate a PDE system for solution via MethodOfLines.jl. In the last step, I need to use the PDESystem constructor. It is not clear to me what the arguments of that function need to be. Here is what I have done, and which is accepted:

@named gas_lift = PDESystem(eqs,bcs,doms,[t,x],[p(t,x),ṁ_ℓf, ṁ_a2t, ṁ_t2p])

However, I get an error message when I run the discretize function.

Question:

1. What is required of the 5th argument, the dvs – dependent variables; [p(t,x),ṁ_ℓf, ṁ_a2t, ṁ_t2p] in the example above? Do I list those that I want to find the values of, or the entire list?
2. In my case, I have a large number of variables in (t,x) and a large number of variables in t. I have 3 PDEs, a number of algebraic equations within the volume, and a number of algebraic equations in the BCs. I have already used the @variables macro of MTK to specify variables. Do I need to repeat all variables here?

[ChrisRackauckas]

@BLI

What is required of the 5th argument, the dvs – dependent variables; [p(t,x),ṁ_ℓf, ṁ_a2t, ṁ_t2p] in the example above? Do I list those that I want to find the values of, or the entire list?

The whole list.

@BLI

In my case, I have a large number of variables in (t,x) and a large number of variables in t. I have 3 PDEs, a number of algebraic equations within the volume, and a number of algebraic equations in the BCs. I have already used the @variables macro of MTK to specify variables. Do I need to repeat all variables here?

Yes, though you can just slap that array down if you define the variables in an array.

[BLI]

I had defined variables in an array…

vars = @variables begin
    # Distributed variables
    m̌_ℓ(..),            [description = "Liquid bulk density, kg/m^3"]
    ṁ_ℓ(..),            [description = "Liquid mass flow rate, kg/s"]
    m̌_g(..),            [description = "Gas bulk density, kg/m^3"]
    ṁ_g(..),            [description = "Gas mass flow rate, kg/s"]
...
# Temporal variables
    ṁ_ℓf(t),            [description = "Liquid mass flow rate from reservoir formation, kg/s"]
    p_f(t),             [description = "Reservoir formation pressure, Pa"]

However, I assume the dvs needs to be in the following form:

dvs = [m̌_ℓ(t,x), ṁ_ℓ(t,x), m̌_g(t,x), ... ṁ_g(t,x), ...ṁ_ℓf, p_f, ...]

In any way, creating the PDESystem(...) seems to work, i.e., does not give an error message.