[taosifme014]

I want to write a Fluent UDF that changes material's property irreversibly once it reaches a certain temperature. Like, if 500 K be my target temperature, at the start of the simulation when the material is below that temperature it will have a density of 1000 kg/m^3. But once the temperature reaches or goes beyond 500 K its density changes to 700 kg/m^3 and stays like that even if in later period temperature falls down below 500K. What algorithm should I follow to write this UDF?