Because of the high elongational viscosity of polymers, a large pressure drop, called entrance loss, is encountered near an abrupt contraction, which can be used for indirect measurements of elongational viscosity.
where [dot.[epsilon]] is the elongation rate, [[eta].sub.e] the elongational viscosity, n the power law index for shear viscosity, [P.sub.e] the entrance loss, [[tau].sub.w] the shear stress at the wall in the downstream channel, and [dot.[gamma].sub.a] is the apparent shear rate.
The design coefficients derived in this study were the entrance loss coefficients, which are the numbers multiplied by the velocity head to estimate the entrance energy loss for a culvert operating in outlet control where the headwater depth is influenced by tail water and friction in the culvert as well as the entrance loss.
The values for the entrance loss coefficient for the field-cast models with straight wingwalls were almost identical for the single-, double-, triple-, and quad-barrel models and averaged 0.52.
3, combined with this entrance loss
, is an accurate predictor of the behavior of the guide.
Extra pressure loss and vortex length predicted by a finite element simulation of entrance loss are compared with the corresponding predictions from Binding's approximate analysis.
Because of the high elongational viscosity of polymers, this extra pressure loss, called the entrance loss, can be particularly large for polymers.
Plastometer Entrance Losses The ASTM D1238 MFI test is a special test that specifies a short capillary L/D.
WIth long L/D capillaries, the ratio of capillary losses to entrance losses decreases, and the measurement approaches polymer viscosity alone.