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 Create/Edit Materials dialog box, choose piecewise-linear in the drop-down list to the right of the property name (e.g., Viscosity). The Piecewise-Linear Profile dialog box(Figure  8.2.2) will open automatically.

Figure 8.2.2: The Piecewise-Linear Profile Dialog Box

  Since this is a modal dialog box, 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 dialog box in Figure  8.2.2 shows the final inputs for the profile depicted in Figure  8.2.3.

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

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