GSC - Goal Seek & Control

What is the GSC Module?

An optional add-on module to AFT Fathom which allows users to perform multi-variable goal seeking and simulate system control functions.

Many engineering modeling tasks involve more than just directly solving a system. In some cases a manual, “cut and try” method of changing input variables to achieve desired operating results is required. When a single parameter is being changed, the manual process (while tedious and time consuming) can be used successfully. However, varying two or more parameters at the same time quickly becomes impractical.

The GSC module automates the process of changing input variables to achieve desired design goals. For single variable situations, the GSC module offers the advantage of being much faster than manual methods. Further, it provides a practical tool for solving cases when there are two or more variables.

How Does the GSC Module Work?

The GSC module employs numerical optimization technology like that used in the AFT Fathom ANS Module. The optimization engine employed by the AFT Fathom GSC module uses state-of-the-art optimization technology licensed from Vanderplaats Research and Development, the leading company in optimization technology. However, rather than minimizing some function value such as system cost or weight, the GSC module satisfies equality criteria using “goal programming” methods.

The core hydraulic solution in AFT Fathom is performed by the Hydraulic SolverHydraulic Solver The part of AFT Fathom that applies the governing incompressible flow equations to obtain a solution to the pipe system.. In standard AFT Fathom usage, the Hydraulic Solver is called once to solve a system. The GSC module’s Numerical Optimizer is used to call the Hydraulic Solver repeatedly, thus solving a series of models with different inputs. The Numerical Optimizer adjusts the user specified Variables in order force the Hydraulic Solver output values to agree with the user specified Goals. Figure 1 depicts the relationship between the different components.

Using the GSC Module

The user has the option of activating or not activating the GSC module when AFT Fathom first loads. After AFT Fathom is loaded, the GSC module can be activated or deactivated for use from the Modules panel in the Analysis Setup window or the Tools menu. Whether or not GSC is activated impacts the View menu, Analysis menu, Model Data window, Solution Progress window, and Output window as is discussed in the Modules panel topic.

If the GSC module is active, the user can still run models without goal seeking. This is selected under Goal Seek & Control on the Analysis menu. Hence there are three possibilities for GSC.

• GSC is not active

• GSC is active and goal seeking is ignored

• GSC is active and goal seeking is performed