Force Set Types

There are several types of forces that can be defined for analysis with AFT Impulse:

• Point - Point forces are simply the difference in pressure between the fluid and the ambient environment multiplied by the pipe area, which can be used for Dead End junctions.

• Difference - Difference forces are defined between two nodes, or computation stations. These nodes should be located at 90 degree direction changes. There may be one or several junctions between the elbows so long as the flow does not branch between the nodes and all components are axially aligned. An example of this is the hydraulic loading between two elbows along the length of a pipe. See Figure 1 below.

• Difference Exit - Similar to the difference force set in that two nodes are required. However, the first node must be a 90 degree elbow, and the second node must be a location where flow exits the system. A user defined exit area will be used at the exit node for calculating the force across the section. This is useful for modeling forces on exit valves, exit orifices, and relief valves.

Note: Pipes are assumed to be rigid bodies and AFT Impulse does not account for the effect of pipe deflection on forces.