AFT Impulse 2022 Description
AFT Impulse provides a practical tool for the channel transmission systems engineer to address the complex topic of liquid waterhammer channel transmission systems and surge transient events. AFT Impulse includes an integral steady-state solver to compute initial conditions and communicate them seamlessly to the transient solver.
Based on the same proven Fathom AFT solver, steady-state solutions are determined using a modified Newton-Raphson interation matrix. The transient decision mechanism for the Impulse AFT flow is based on the Characteristics Method using a prescribed relationship between spacing step and clock. This allows for a direct solution to each beat, making AFT Impulse very effective.
AFT Impulse allows you to define transients on both time and event basis. For example, initiate a pump start based on pressure at a selected location in the system or valve closure based on flow direction at a selected location. This powerful capability greatly expands the type of transient that can be modeled to include a variety of logic control functions.
Simulating a pump can be as simple as a fixed flow or as complex as involving four quadrant effects, simulating various possible combinations of forward and reverse flow and rotation. Start and displacement simulations can use a specific speed versus time, or account for pump / driver inertia and driver torque versus speed. Pump models can include integral isolation valves and invert rotation brakes.
From the hydraulic timing solution, the variable pressure and the AFT Impulse of the flow, transient unbalanced forces can be calculated. Users can define force sets, which can be any force pair (for example, bends at the beginning and end of a run) and a point force (for example, at the end of a run where the run channel contains a decoupled expansion joint). Users can choose to enable forces from pressure, momentum and frictional pressure drop response.