1. In a physical computing device that implements an engineering design tool comprising a surrogate model generator, the physical computing device having a processor and memory, a computer implemented method comprising: with the physical computing device that implements the engineering design tool comprising a surrogate model generator, transmitting to a computer processor a first set of input variables, the first set of input variables comprising one or more variables representing one or more physical quantities at a first time period, the first time period representing an event time period; executing on the computer processor computer readable instructions representing a numerical transport model that outputs a representation of a physical process over the first time period; executing on the computer processor computer readable instructions for calculating the indicial admittance function of the numerical transport model for the first time period using inverse convolution; executing on the computer processor computer readable instructions for constructing a surrogate model using the indicial admittance function, the surrogate model representing the numerical transport model; executing on the computer processor computer readable instructions for storing the surrogate model on a computer readable storage medium, providing a stored surrogate model; transmitting to the computer processor a second set of input variables representing one or more physical quantities at a second time period, the second time period being within the first time period; executing on the computer processor instructions for calculating a representation of the physical process at the second time period with a second set of input variables using the stored surrogate model; and executing on the computer processor instructions for outputting the representation of the physical process at the second time.