Incorrect number or types of inputs or outputs for function solvepde.

Hello everyone,

I am preparing an assignment for a course - my code is getting the solvepde error (title) at the very end, and I am not sure what the issue might be. I would love some input - thank you kindly!!

The prompt and the code:

Square pipes are used when building infrastructure. We will now look at an example of a 1/2" steel pipe surrounded by 2'' of concrete on all external sides and filled with concrete.

Let us compare two scenarios:

• the building is placed in the Death Valley, where the highest temperature recorded was 134 F (56.7 C).
• the building is placed in Fairbanks, Alaska, where the lowest temperature recorded was ca. -66 F (-54.4).

How does heat propagate in the concrete-steel-concrete composite system?

% Geometry

geom = multicuboid([11 12 16],[11 12 16],60);
pdegplot(geom,FaceLabels="on",FaceAlpha=0.5)

% Thermal Model
tmodel = createpde("thermal","transient");

tmodel.Geometry = geom;

% Thermal Properties: C1 is the inside 

k_concrete = 2.04; %W/mC %https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.matec-conferences.org/articles/matecconf/pdf/2018/104/matecconf_eece2018_06005.pdf&ved=2ahUKEwiEvrPJ6-WGAxV-FlkFHX0tBCMQFnoECBIQAw&usg=AOvVaw2ABKGgoRACGkNwjUag6rUf
k_steel = 50; %W/mC %https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.heissbemessung.net/Infothek/Materialien_im_Brandfall/Thermal-conductivity-steel.html&ved=2ahUKEwjRz-Db6-WGAxUqL1kFHa_RDkcQFnoECCIQAw&usg=AOvVaw0uqB4TjsVmYNj5ydlfIaK9

rho_concrete = 2400; %kg/m3
rho_steel = 7850; %kg/m3

c_concrete = 880; %J/kgC
c_steel = 420; %J/kg C

wind_v = 100; %m/s
h_air = 0.0222*wind_v^2+3.1511*wind_v+10.9; %W/m2 C, http://dx.doi.org/10.1007/s11595-011-0312-3
T_air = 56.7; % C

% Boundary Conditions

thermalProperties(tmodel,"Cell",1,"ThermalConductivity",k_concrete, "MassDensity",rho_concrete,"SpecificHeat",c_concrete);
thermalProperties(tmodel,"Cell",2,"ThermalConductivity",k_concrete,"MassDensity",rho_steel,"SpecificHeat",c_steel);
thermalProperties(tmodel,"Cell",3,"ThermalConductivity",k_concrete, "MassDensity",rho_concrete,"SpecificHeat",c_concrete);

thermalBC(tmodel,"Face",[1 2 11 12 17 18],"HeatFlux",0); % Ends of the slab do not exchange heat
thermalBC(tmodel,"Face",[13 14 15 16],"ConvectionCoefficient",h_air,"AmbientTemperature",T_air); % External faces 

% Initial Conditions

class(tmodel)
thermalIC(tmodel,18,"Cell",[1 2 3]);

% Mesh

generateMesh(tmodel);

tlist = 0:1000; %s

Rt = solvepde(tmodel,tlist);

Answer 1

[Steven Lord]

When I run your code, tmodel is a pde.ThermalModel object but the solvepde function is defined only for pde.PDEModel objects.

pmodel = createpde; % make a sample pde.PDEModel object
class(pmodel)

ans = 'pde.PDEModel'

tmodel = createpde("thermal","transient");
class(tmodel)

ans = 'pde.ThermalModel'

which solvepde

/MATLAB/toolbox/pde/+pde/@PDEModel/solvepde.m  % pde.PDEModel method

Is a pde.ThermalModel object also a pde.PDEModel object? It is not.

isa(tmodel, class(pmodel))

ans = logical
   0

Looking at the documentation page, the correct function to use to solve a system defined as a pde.ThermalModel object is the solve function.

[Michela]

Thank you for showing me those tips!