This value represents the acceptable fractional temperature error used to determine the time step. The time step may vary by many orders of magnitude during the course of an analysis, depending on the loads and constraints. At the beginning of an analysis, the time step can be especially small. Since the energy norm in the model is zero at the start of an analysis, the errors in energy norm are normalized by a small value.

This value works with the temperature variation value to control the accuracy of the time integration. For example, if you set Accuracy to a value of 0.001 and set Estimated Variation to a value of 200, the Thermal engine attempts to keep time-step errors in temperature to a value of 0.2 degrees or less.

Creo Simulate controls the accuracy of transient thermal analyses by varying the p-order of element edges and the time step used for numerical integration. These values change as an analysis progresses. Two parameters affect the time step size on the Analysis Definition dialog box for transient thermal analysis—Accuracy and Estimated Variation.

Errors in temperature must be less than the product of the estimated temperature variation and the accuracy.