An update to our 1D dynamic simulation library for hydraulic systems, built on OpenModelica: fluid model updated, new components, and more reliable FMU export.
SFPLibDyn 4.0 is now available, the latest update to our hydraulic simulation library for fluid-mechanical systems, built on OpenModelica. The most significant change in this release concerns how the library handles hydraulic fluid properties, but the update also brings new control components, more reliable FMU model export, and alignment with the latest OpenModelica versions.
At the heart of the update: the new hydraulic fluid model evolves
Hydraulic fluid isn’t just a “liquid flowing through pipes”: its viscosity and density change with temperature and pressure, and this has a real impact on the accuracy of a hydraulic simulation. A typical example is high-pressure systems, where simplified fluid property models can easily underestimate local viscosity values. With SFPLibDyn 4.0, we have introduced new capabilities and improved the user experience for who want to take full advantage of the flexibility and accuracy offered by our fluid property models.
The old tabbed window has been replaced with a more guided workflow: you first select which fluid in the model you want to modify, and a dedicated window opens for that fluid alone. For each fluid, you can choose among several preset models or freely customize the parameters, just as in the previous version.
The real novelty is that viscosity and density can now be calculated using different models, depending on how much realism the simulation requires. For viscosity, for example, you can choose to keep it constant to simplify and speed up the simulation, make it temperature-dependent, or make it dependent on both temperature and pressure — this last option is particularly useful for hydraulic systems operating at high pressures, where neglecting the effect of pressure on viscosity would lead to unrealistic results. A similar approach applies to density, where a model widely used in the industry for petroleum-derived fluids is also available.
In short: the SFPLibDyn simulation library now lets you choose the right balance between computation speed and physical accuracy, fluid by fluid. Since this is the most significant change in this release, we’ll be dedicating a follow-up article to it soon.
New control logic components: integrator, derivative, PI and PID
SFPLibDyn 4.0 introduces several new blocks for anyone who needs to simulate, alongside the hydraulic circuit, the electronic logic that controls it: an integrator, a derivative block, and two controllers, PI and PID. These are components built for realistic use in control system simulation, with features useful during testing, such as the ability to freeze or reset their state during the simulation and automatic handling of output saturation. They come in handy whenever you need to simulate a control loop — for example, pressure or speed regulation in a hydraulic system.
New hydraulic valves
Two new valve models have also been added, belonging to the logic elements family: one normally closed and one normally open, both with external pilot control. Their behavior adapts automatically to the chosen parameters, including the graphical symbol in the diagram, and they make it possible to generically represent different families of logic hydraulic valves that, in a commercial catalog, are often found in similar but not identical variants.
More reliable FMU export
Anyone using SFPLibDyn models exported as FMUs to integrate with other simulation tools will find an important improvement: a bug in previous OpenModelica versions could make certain parameters appear editable when they were actually locked to the value used at model creation time. This issue has been fixed, and the SFPLibDyn library has been updated accordingly, so parameters are now genuinely configurable when needed. Alongside this, FMU creation is now handled through a new graphical interface, simpler to use than the previous approach.
Other library improvements
The update also includes a refreshed color scheme for the library’s icons and several fixes to existing components (including a shuttle valve, a flow rate sensor, and a few ball valve models), aimed at making the simulation library’s behavior more stable and robust.
An online guide that keeps growing with SFPLibDyn
Alongside the guide already built into the library, which stays tied to the installed version, we’ve launched an online SFPLibDyn manual designed to grow together with the product. That’s the key difference: while the built-in guide is only updated with each new library release, the online manual is expanded and corrected more frequently, without waiting for the next release. It covers installation and licensing, a quick OpenModelica guide, information on the trial version, deeper insights into the library’s structure, solutions to common issues, practical examples, and an FAQ section — a resource meant to complement, not replace, the documentation already included in the library.
And what about the OpenModelica 1.27 update?
SFPLibDyn 4.0 is also an opportunity to align with OpenModelica 1.27, a jump of two versions from the one we currently offer. This isn’t our own work, but it’s worth highlighting a few improvements that matter to anyone modeling with Modelica every day: a more modern and responsive graphical interface, enhanced post-processing features, simpler tools for finding where a component is used across your models, and even the first experimental AI integration features — a topic we’ll be coming back to ourselves soon.
