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8.2.2 Inputs for Piecewise-Linear Functions

To define a piecewise-linear function of temperature for a material property, do the following:

1.   In the Materials panel, choose piecewise-linear in the drop-down list to the right of the property name (e.g., Viscosity).The Piecewise-Linear Profile panel(Figure  8.2.2) will open automatically.

Figure 8.2.2: The Piecewise-Linear Profile Panel
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  Since this is a modal panel, the solver will not allow you to do anything else until you perform the following steps.

(a)   Set the number of Points defining the piecewise distribution.

(b)   Under Data Points, enter the data pairs for each point. First enter the independent and dependent variable values for Point 1, then increase the Point number and enter the appropriate values for each additional pair of variables. The pairs of points must be supplied in the order of increasing value of temperature. The solver will not sort them for you. A maximum of 30 piecewise points can be defined for each property. The panel in Figure  8.2.2 shows the final inputs for the profile depicted in Figure  8.2.3.

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If the temperature exceeds the maximum Temperature ( $T_{\rm max}$) you have specified for the profile, FLUENT will use the Value corresponding to $T_{\rm max}$. If the temperature falls below the minimum Temperature ( $T_{\rm min}$) specified for your profile, FLUENT will use the Value corresponding to $T_{\rm min}$.

Figure 8.2.3: Piecewise-Linear Definition of Viscosity as $\mu (T)$
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