The lag of the phreatic line depends on factors such as: permeability of soils, drawdown rate, drawdown ratio
and slope gradient during rapid drawdown, the stabilizing effect of the water on the upstream face is lost, but the pore-water pressures within the embankment may remain high.
So with the addition of LDPE to LLDPE, more orientation can be locked in the MD during fabrication of the film, due to a much higher drawdown ratio
in the MD, as compared with the blow-up ratio (BUR) in the CD.
As multilayer reflector of the fiber is drawn from the rolled multilayer film in the preform, the thickness of the individual layers in the preform can be determined by multiplying the desired layer thickness in the fiber by the drawdown ratio
used during the drawing process.
Han  and Huang and White  obtained experimental results on die swell of non-circular fibers, but they studied only free swelling with no drawdown, of which the state is far from real industrial spinning process with a large drawdown ratio
The preferred drawdown ratio
for a die is between 1.8:1 and 2.5:1.
This means each polymer has a different drawdown ratio
. Thermoplastics such as PP and LDPE are crystalline with a high specific heat and require greater drawdown than an amorphous material such as rigid PVC.
3 as a function of a drawdown ratio
. The spinline stress vs.
The two most critical dimensions, however are land length and drawdown ratio
The melt strength and drawdown ratio
(DDR) for the samples at 230 C are shown in Fig.
It suggests the following empirical dimensionless relations between die line sizes and take-off speed (or drawdown ratio
Considering our processing conditions, the time for extension is about 2 s when the drawdown ratio
is 1 and decreases for higher drawdown ratios
Crystalline orientation and birefringence were found to correlated with spinline stress better than drawdown ratio
. Crystalline orientation development was strongly dependent on spinline stress.