Applies To Product(s): Bentley HAMMER Version(s): 08.11.xx.xx Environment: N\A Area: Modeling Subarea: N\A Original Author: Nancy Mahmoud, Bentley Technical Support Group Problem What does the "Wave Speed Reduction Factor" under Calculation Options do? Solution At low pressures entrained air in a liquid can come out of solution, which can reduce the wave speed. This Wave Speed Reduction Factor field gives some control over the wave speed in the model at low pressures. It is used in conjunction with the "Decrease Time" and "Increase Time" fields. For example, consider entering the following data in the model: a wavespeed of 1000m/s , a Wave Speed Reduction Factor of 0.5, a Decrease Time of 0.2 seconds, and an Increase Time of 3 seconds. In this case, if the liquid pressure reaches vapor pressure, the wave speed in that pipe will start to reduce. Assuming the pressure doesn't increase again in the meantime, the wavespeed will reduce to 500 m/s (1000 m/s x Wave Speed Reduction Factor) linearly over 0.2 seconds (the Decrease Time). While the pressure stays low the wavespeed will stay at 500 m/s, but if the pressure increases the wavespeed will also increase linearly back up to 1000 m/s over 3 seconds (the Increase Time).
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