AFT Fathom's GSC Module both automates various aspects of parametric modeling and enhances Fathom's ability to simulate system control functions.
A common aspect of parametric modeling is making a series of runs to determine the value of one or more inputs required to yield a desired value of one or more outputs. For example, what pump speed will yield control valve operation within a specified open percantage range, or what pressure reducing valve setting will produce a minimum required flow rate among multiple demand points? With one variable and goal, GSC provides a handy savings in time to automate this procedure. Start expanding the number of variables and goals, however, and GSC's functionality isn't just convenient, you'll often find the only way to find the answer in a practical amount of time.

Finding an input's value to produce a desired output isn't a simple matter of trial and error. This would be both time inefficient and often fail to find a solution. GSC uses powerful numerical optimization methods to perturb the system and determine the sensitivity of the goals to the variables. Perturbation and searching is repeated to yield a solution quickly and robustly.

Goal Seek & Control Manager

Easily and quickly set goals and define variables with the goal seek & control manager. Drop down lists let you select the type of object (pipe or junction) and, based on your choice, automatically list the available objects in your model the appropriate goal or variable type. Goals and variables may duplicated to quickly build variations and you can choose to ignore selected goals and variables on the fly, allowing you to run variations on your goal and variable set while retaining definitions you've built.

The GSC Module's wide variety of goal types provides tremendous capability in automating your system modeling. These include -

• Point goal - a specified output value at a specific location
• Group goal - may be either a sum or max/min, for example, the total flow of a group of pipes or the maximum or minimum flow within the group
• Differential goal - an output value of specified difference between two points; e.g. the pump speed to produce a desired differential pressure between users on a common supply/return main

Variables may be linked, forcing values to be the same, for example, parallel pumps to operate at the same speed.

Variable and Goals

Input values to be changed are referred to in GSC as variables, while the corresponding output values are the goals, and include a wide variety of input and output values in AFT Fathom.

Input parameters that may be used a variables include -

• Pumps - speed, flow rate, head rise, impeller diameter
• Reservoirs (tanks) - liquid level, surface pressure, temperature
• Branch point - source/sink flow rate
• Assigned flow - flow rate, elevation, temperature
• Assigned pressure - pressure, elevation, temperature
• Valve - Cv, K, elevation
• Control Valve - setpoint
• Orifice - diameter, K factor, area
• Check valve - Cv, K
• Venturi - K factor
• Screen - K factor, area
• Heat exchanger - K factor, heat rate, outlet temperature, temperature differential, enthalpy change, heat transfer area, overall U value, secondary fluid flow rate, secondary fluid temperature
• Spray discharge - area, K factor, exit pressure, number of sprinklers (goes with K), number of holes (sparger), elevation
• General component - K factor
• Three way valve - open percentage

Output parameters that may be used a goals include -

• Area change - flow rate,, velocity, pressure, temperature, gradeline
• Branch - flow rate, velocity, pressure, temperature, energy gradeline, hydraulic gradeline
• Control valve - flow rate and velocity (pressure control valves), pressure (flow control valves), temperature, gradeline (flow control), Cv, open percentage, pressure drop and head loss
• Dead end - pressure, gradeline
• Bend - flow rate, velocity, pressure, temperature, gradeline
• Assigned flow - pressure, gradeline
• General component - flow rate, velocity, pressure, temperature, gradeline
• Heat exchanger - heat rate, flow rate, velocity, pressure, temperature, gradeline
• Jet pump - flow rate, velocity, pressure, temperature, gradeline
• Check valve - flow rate, velocity, pressure, temperature, gradeline
• Relief valve - flow rate, velocity, pressure, temperature, gradeline
• Orifice - flow rate, velocity, pressure, temperature, gradeline
• Assigned pressure - flow rate
• Pump - flow rate, velocity, pressure, temperature, gradeline, pressure/head rise, power, NPSH margin
• Reservoir (tank) - flow rate
• Screen - flow rate, velocity, pressure, temperature, gradeline
• Spray discharge - flow rate
• Tee/wye - pressure, temperature, gradeline
• Three-way valve - pressure, temperature, gradeline
• Valve - flow rate, velocity, pressure, temperature, gradeline
• Venturi - flow rate, velocity, pressure, temperature, gradeline
• Volume balance - flow rate, velocity, pressure, temperature, gradeline
• Pipes - flow rate, velocity, pressure, temperature, gradeline, head loss, pressure drop due to friction, pressure gradient, min/max pressure, temperature loss, inside wall temperature, heat rate