question

Unfortunately there's no perfect rule of thumb on when accuracy becomes an issue in fluid objects. The tick time is only one factor among many that may impact accuracy, such as flow rates, the number of and connection configuration of the objects in the system, and even the accuracy "tolerance" that users are willing to accept. In relation to DJ's reply, in some situations a 2% tolerance might be "good enough," whereas in others it is obviously unacceptable.

I think what DJ was getting at in his answer is that Talumis' FloWorks module simulates fluid systems in a much faster and more accurate manner. In reality, the question of "how much inaccuracy is acceptable" shouldn't really need to be a question at all. As such, we at FlexSim have discontinued our development of the fluid library, and instead suggest FloWorks, and use it ourselves in-house, as the best high-accuracy fluid simulation solution in FlexSim. We have left the legacy fluid library in the product so that users who do not want to pay the extra add-on cost of FloWorks may still have a solution, albeit a less accurate solution, for simulating fluids.

So, my suggestion is, if you really just want to get a rough estimate out of your simulation, then perhaps the fluid library will be good enough. You can do a sensitivity analysis (try different tick times) to see how much results are affected. But if you don't want to even worry if the accuracy is good enough, to me it is worthwhile to bite the bullet and get a license of FloWorks.