I am simulating hydraulic hammer using the WP component in the thermal hydraulic library. The resulting transient's damping ratio seems to be incredibly sensitive to the number of segments I define within the component. Which results do I trust?

Just to follow up on this, I determined that it was independent of the transient friction model used. I only found the damping characteristics to be sensitive for small numbers of total WP components. Once I built a more representative, complex system with over 20 total WP components, system damping sensitivity to spatial and temporal discretization seemed to vanish. I realized that I was supposed to keep the length of each division GREATER THAN or equal to the rule of thumb mentioned in the post, not less than or equal to. I suspect that the full scale system has a higher total fluid volume and larger cumulative WP component length which allowed me to use a larger, internal discretization on individual WP components which stabilized the system by increasing the pressure differential between internal nodes of individual WP components. I suppose only having one or two short WP components with smaller internal discretizations created a numerically unstable system with lower pressure differentials between internal nodes, which may have contributed to numerical instability caused by the overdiscretization of a single, short WP component. I also was having run time hangups that I was able to attribute to the switch state methodology built into Easy5 in reference to the orifice transition Reynolds number. I had changed the number from 100 to close to 3000 with minimal impacts to the solution with a significant impact on the run time (although it still takes a while, even with the larger transition Re number).

Just to follow up on this, I determined that it was independent of the transient friction model used. I only found the damping characteristics to be sensitive for small numbers of total WP components. Once I built a more representative, complex system with over 20 total WP components, system damping sensitivity to spatial and temporal discretization seemed to vanish. I realized that I was supposed to keep the length of each division GREATER THAN or equal to the rule of thumb mentioned in the post, not less than or equal to. I suspect that the full scale system has a higher total fluid volume and larger cumulative WP component length which allowed me to use a larger, internal discretization on individual WP components which stabilized the system by increasing the pressure differential between internal nodes of individual WP components. I suppose only having one or two short WP components with smaller internal discretizations created a numerically unstable system with lower pressure differentials between internal nodes, which may have contributed to numerical instability caused by the overdiscretization of a single, short WP component. I also was having run time hangups that I was able to attribute to the switch state methodology built into Easy5 in reference to the orifice transition Reynolds number. I had changed the number from 100 to close to 3000 with minimal impacts to the solution with a significant impact on the run time (although it still takes a while, even with the larger transition Re number).