Way to multiply the output values of 2 different RAMPs.

[bwklein]

As the subject suggests, I would like a math function control to output the values from two ramps multiplied together, or the product of a control value output by the output value of a ramp.

Is there a direct or clever way to do this?

[mcgratta]

I'm sure there is, but I cannot say off the top of my head. Jason will probably know.

[mcgratta]

I would guess that you create two dummy devices that output exactly the ramp the values, and then use a control function to multiply them together.

[bwklein]

That would work. How do I make a device to report the output value of the ramp? I know how to do it for a control with QUANTITY='CONTROL VALUE' , but I haven't found a way with a RAMP yet.

[johodges]

It would be a lot easier to do this if there was a QUANTITY for DEVC for RAMP_VALUE similar to CONTROL_VALUE. Control functions are pretty flexible though, so I imagine there is a way to do it without a change. It would be a lot cleaner with a RAMP_VALUE output though.

[drjfloyd]

See 18.6.4 Example Case: Heat Release Rate of a Spreading Fire

You just have the RAMP invoked by a CUSTOM function then use that function's ID in the multiply function.

[bwklein]

That's the answer, I was using the FDS documentation for the last release of PyroSim and this example wasn't there. In the new version of the user manual there is a beautiful example of what I am trying to do. Thanks @drjfloyd !