Fluid Resistances

[Dougt115]

IF I have a pipe with two restrictions in it (one at each end) each with a different diameter does the resistance change based on the direction of fluid flow?

The case is a hydraulic damper that has a load of 900N to pull and 600N to push, the position change rate is the same in both directions. The geometry is supposed to be identical but due to tolerances there is a chance that one opening is smaller that the other.

Testing on and Instron, Trapazoidal cycle, 12mm/sec to 5mm wait 1 sec, decrease 12mm/sec to 0mm wait 2 sec, Repeat 5 cycles
Record max loads during each cycle.

Any other suggestions as to a cause in the uneven loading would be appreciated.

Theoretically there are no parts moving during the cycling.

 

[1gibson]

What is the orifice geometry?

____ ____
____| |____

Or

____ ____
___/ \___

The first one should be the same with flow in either direction. The latter will have different coefficients for flow in each direction.

 

[BigInch]

The resistance does not change, but resistances are pressure drops and the pressure at any point in the system is = Reference Pressure - the sum of resistances to that point, so the pressure at a point may change radically if fluid direction changes.

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