MATLAB PARTIAL DIFFERENTIAL EQUATION TOOLBOX 1 Manual de usuario descargar pdf (Pagina 15)

Properties from the pop-up menu. In the Thermal window under the Options tab select Transient

and verify that the Total time is set to 1 sec and the Time increment is set to 0.1 sec. Click the

Advanced Options button and set the Convergence tolerance to 0.0001%, insure the Under-

relaxation factor for the iteration is set to Automatic, and click OK.

Because the geometry is different for the two and three-dimensional cases you will need to create

new boundary and initial conditions instead of just copying them. To set the boundary

conditions, in the Simulation Tree right click on Thermal Loads and select Temperature from the

pop-up menu. In the Type window for the Faces, Edges, Vertices, or Components for

Temperature select the bottom three faces. In the Temperature window set the temperature to

0 ˚C, in the Variation with Time window insure that the button is NOT selected, and then click

the green check mark. Repeat this process to set the temperature to 100 ˚C for the top face. For

the front and back face boundary conditions, either set the heat flux to 0 W or do not set anything

(because the default is zero heat flux when nothing has been specified). Note that these boundary

conditions correspond to two-dimensional heat transfer in the x-y plane.

To set the initial condition, in the Simulation Tree right click on Thermal Loads and select

Temperature from the pop-up menu. In the Type window select Initial temperature and for the

Faces, Edges or Vertices select the entire part by expanding the Part Tree in the upper left-hand

side of the drawing window and selecting the part called “brick”. In the Temperature window set

the temperature to 0 ˚C and then click the green check mark.

Once again, because the geometry is different for the two and three-dimensional cases you will

need to create a new mesh instead of just copying the previous one. To create the unstructured

mesh, in the Simulation Tree right click on Mesh and select Create Mesh from the pop-up menu.

In the Mesh Parameters window select Standard Mesh and set the Global size to 0.05 m. Verify

that the Tolerance is now set to 0.0025 m and then click the green check mark. In the Simulation

Tree right click on Mesh and select Details from the pop-up menu. Verify that the fairy regular

3D mesh has 6,586 tetrahedral elements and 10,771 nodes.

Once again to solve the problem, in the Simulation Tree right click on Transient 3D and select

Run from the pop-up menu. Notice that it will again take a little longer to solve. These results

should be exactly the same as your results for the two-dimensional case above. You can verify

this by using the probes save in Workflow Sensitive1 to compare temperatures at the same

locations for your two and three-dimensional simulations.

To consider a case that is three dimensional, in the Simulation Tree right click on Thermal Loads

and select Convection from the pop-up menu. In the Select Entities window for the Faces for

Convection select the front face. In the Convection Coefficient window set the value to

100 W/m

•C, in the Bulk Ambient Temperature window set the value to 273 K, then click the

green check mark and re-run the simulation. To verify that the results are now three dimensional,

in the Simulation Tree in the Results folder right click on Thermal1 and select Section Clipping

from the pop-up menu. In the Section 1 window, for Reference Entity choose the Right Plane

from the Part Tree in the drawing window and for the Distance enter 0.5 m. In the Options

window, de-select Show section plane and click the green check mark. You should be able to

clearly see from the contour plot on the mid-plane of the brick that the front is now cooler (with

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MATLAB PARTIAL DIFFERENTIAL EQUATION TOOLBOX 1 Manual de usuario Pagina 15