Construction of a model of a hydraulic damper.

[magicfrog]

TL;DR

Study of a hydraulic brake based on the flow of hydraulic oil through an adjustable orifice. The aim is to develop a computational model that closely matches the simulation results.

Hi everyone, I’ve tried searching the forum for similar topics but I don’t think I’ve found anything relevant to my specific situation. That’s why I’m here to start this new thread.

I am currently studying a hydraulic brake. The spring-operated system is capable of varying its speed (e.g. linear motion) by opening and closing an orifice, which alters the flow rate of the hydraulic fluid. This is a classic choking valve problem.

Using SolidWorks software and with access to the Motion module, I can simulate this mechanism by applying linear or rotational damping, specifying a value and a law (linear, quadratic, cubic).
What I would like to do is relate this hydraulic damper – caused by oil flowing through an orifice – to a coefficient that can be used in the equations, and find an equivalence with the values I can simulate using the software. I wonder: are there any examples where a damping coefficient can be derived from the analysis of a choked valve problem? Are there any theories and practical examples that have been tested?

The idea is to build a model that can determine a motion damping coefficient based on changes in the airflow passing through the orifice.

I hope I have explained my question clearly enough; if not, please accept my apologies, and thank you to anyone who can help.

 

[Chestermiller]

Damping is often approximated using an ideal dashpot. Is that what you are searching for: an approximate equation for the dashpot coefficient as a function of the damping fluid and hydraulic damper design? Are you considering doing experiments to measure the damping coefficient in independent tests?

 

[magicfrog]

Yes, I would like to develop a mathematical model that can describe the behaviour of a hydraulic damper with an adjustable nozzle, and that I can verify both through testing (if only I could figure out how – I’m thinking of measuring deceleration, or how time varies with and without damping, or simply by varying the flow cross-section) and using the simulation software I have available.

Because I still believe we can derive a relationship that actually describes what I can simulate using the software. For example, if I set a linear damping of 4 N/(mm/s), what does that correspond to in reality? What geometry would give me this approximate damping value? Or, conversely, given a geometry ‘x’, what damping value do I obtain? And how does it vary as the geometry changes?

Are these just observations I can draw from tests, or can I build a detailed mathematical model? And if so, how? What assessments would I need to make?

I imagine this isn’t something that can be developed straight away.