Modelling heat in solids

General discussions about how to formulate a script for FlexPDE.

Modelling heat in solids

Postby zhkhan on Wed Mar 06, 2019 10:45 am

In COMSOL we have an option to model heat transfer in solids. For example we have a solid rectangular bar and we want solve 3D heat equation for this geometry. Can we do it in FlexPDE? Any example?

Thanks
zhkhan
 
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Re: Modelling heat in solids

Postby moderator on Wed Mar 06, 2019 1:25 pm

Absolutely. See the "Samples | Applications | Heatflow" directory of the FlexPDE7 user folder after installing.

FlexPDE is a "scripted finite element model builder". It takes systems of partial differential equations provided by the user and creates a finite element model, builds a mesh, solves the problem and presents graphical output. As such, it has no built-in knowledge of any specific area of application. As long as the user can construct a well-posed PDE system, FlexPDE has a good chance of solving it. Couplings between disparate fields of analysis offer it no difficulty, because it has no concept of what fields "belong together". A partial list of features can be found at http://www.pdesolutions.com/product.html.

If you download our free Lite version, you can peruse over 100 example problems and create small problems of your own design. Downloads can be found at http://www.pdesolutions.com/sdmenu7.html . The User Guide is included in the download and it can also be found online at http://www.pdesolutions.com/help/ .

If you would like to investigate FlexPDE further, we can provide you with a free 30-day trial license to try FlexPDE Professional on your own, larger problems. Information about obtaining a trial can be found at http://www.pdesolutions.com/license.html .

If you decide to purchase FlexPDE, purchasing and pricing information can be found at http://www.pdesolutions.com/pricing7.html .
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Re: Modelling heat in solids

Postby zhkhan on Wed Mar 06, 2019 11:15 pm

I found the 3D_BRICKS+TIME.PDE example but I have a question, which is,
How we will be sure that we are solving the heat equation for a solid not in a square cavity?
zhkhan
 
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Joined: Sat Feb 07, 2015 1:02 am

Re: Modelling heat in solids

Postby moderator on Fri Mar 08, 2019 6:30 pm

The COORDINATES section specifies the geometry of your model (see Coordinates in the help index).
You have seven choices. CARTESIAN3, as in 3D_Bricks.pde, selects a "solid" domain. CARTESIAN2 is the default, and selects a planar model.
The parameters you give to your equation will determine what kind of material is contained in your domain.
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Re: Modelling heat in solids

Postby zhkhan on Fri Mar 08, 2019 10:45 pm

Can you please provide a minimal example?
zhkhan
 
Posts: 11
Joined: Sat Feb 07, 2015 1:02 am

Re: Modelling heat in solids

Postby moderator on Mon Mar 11, 2019 4:32 pm

In our USER GUIDE in the HELP system, we have tried to explain the process of constructing a FlexPDE script as clearly as possible, using examples.
One example used there for 3D is the 3D Canister:

TITLE 'Heat flow around an Insulating Canister'
COORDINATES
Cartesian3
VARIABLES
Phi { the temperature }

DEFINITIONS
K = 1 { default conductivity }
R = 0.5 { blob radius }

EQUATIONS
Div(-k*grad(phi)) = 0

EXTRUSION
SURFACE 'Bottom' z=-1/2
LAYER 'underneath'
SURFACE 'Can Bottom' z=-1/4
LAYER 'Can'
SURFACE 'Can Top' z=1/4
LAYER 'above'
SURFACE 'Top' z=1/2

BOUNDARIES
REGION 1 'box'
START(-1,-1)
VALUE(Phi)=0 LINE TO (1,-1)
NATURAL(Phi)=0 LINE TO (1,1)
VALUE(Phi)=1 LINE TO (-1,1)
NATURAL(Phi)=0 LINE TO CLOSE

LIMITED REGION 2 'blob' { the embedded blob }
LAYER 2 k = 0.001 { the canister only }
START 'ring' (R,0)
ARC(CENTER=0,0) ANGLE=360 TO CLOSE

PLOTS
GRID(y,z) ON x=0
CONTOUR(Phi) ON x=0
VECTOR(-k*grad(Phi)) ON x=0
ELEVATION(Phi) FROM (0,-1,0) to (0,1,0) { note 3D coordinates }

END
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