Impedance Characteristics of Orifices
Keywords:
fluid circuit component,
fluitdic control,
flow measurement,
pressure measurement,
dynamics
1987 Volume 23 Issue 1 Pages 21-26
Details
1987 Volume 23 Issue 1 Pages 21-26
The resistance R and the inertance L of a short-tube orifice without through-flow have been measured indirectly from the pressure signal transfer across the orifice installed in a 130m long tube of 8mm ID. The orifices tested are 0.5, 1, 2mm dia. and their length to diameter ratio l/d covers 0.25 to 4.
Nonlinear effect on R is proportional to (vm/ω)/l and inversely to √ν/ω/d, where vm/ω is the displacement amplitude or “stuck” length of vibrating fluid column within the orifice, and √ν/ω is the thickness of dynamic boundary layer (vm: velocity amplitude, ω: angular frequency, ν: kinematic viscocity). Decrease of L with the amplitude may be well explained by the end-correction modified with the stuck length.
Both data of R and L for smaller orifices (0.5, 1mm dia.) are plotted most compactly by use of general formed tube impedance. Thus, for l/d greater than about unity, an orifice should be considered as a transmission line connected with a nonliner impedance rather than as a knife-edged orifice.
