Monitor Derivative
The monitor derivative report is a monitor-based report that numerically computes the derivative of one monitor with respect to another as of the latest sample time/iteration that they have in common. This shows how much one monitor is affecting another.
Use cases include:
- Monitoring pressure at a point in a transient acoustics simulation, in which you want the derivative of that pressure with respect to time for an application
- Monitoring force and displacement on a piston face in a shock absorber simulation, in which you want the derivative of force with respect to displacement to input into a linearized analysis downstream
To predict how a monitor value is evolving, you can compute its derivative of level 1, which is equivalent to the acceleration of the changes, as follows:
- Derivative Order at 1
- Accuracy Order to 3 or more
- Additional samples to 3 or more
Monitor Derivative Report Properties
- Units
- Units for specifying the quantity. An exponent appears when you set Derivative Order to a value greater than 1.
- Source monitor
- The monitor to use as the source variable.
- Differentiation variable
- The monitor to use as the differentiation variable. It can be set to physical time or iteration to get a simple derivative.
- Derivative Order
- The level of derivative to obtain from the two monitors. The derivative order is set to 1 by default but it can be increased to get a derivative of higher degree.
- Accuracy Order
- Increases the order of the polynomial function used in the approximation to improve accuracy.
- Additional samples
- Takes a specified number of extra samples in addition to the Sample count originally specified in the Last N Samples node. The Sample count property value gets updated to reflect the total number specified. As with the Accuracy Order, increasing the samples can also get a better approximation function.
Child Node Properties
The monitor derivative report node has a child node named Last N Samples.
- Sample count
- The number of data samples N collected for each cell within the monitor. For the Last N Samples node only.
- Sample start event
-
The event at which to begin collecting data. See User-Defined Update Events.
注 With the derivative report, it is usually not appropriate to use a sample start event, as the report handles its own input samples automatically. Using a start event policy may deprive the monitor from getting enough samples to compute the derivatives. - Include start event sample
- When On, includes the sample at a start event in the sample collection.