Possible Systematic Error in the Measurement of Normal Stress Differences in Polymer Solutions in Steady Shear Flow

The measurement of normal stresses by means of liquid-filled holes in a surface

“…The work is closely related to some recent measurements of Broadbent et al (1968) and of who first proposed that such errors may be important in determining the normal-stress differences of fluids in steady shear flows. Some dimensional arguments are presented to show how our estimate of $he normal stress at the surface may be affected by the measuring technique and by the particular kind of curvilinear shear flow in which the measurements are being made.…”

“…An explanation of these anomalies ~) questions the validity of the technique of using fluid-filled cavities to measure the normal stress at a surface. Thus KLV suggest that their measurements of the normal-stress distribution, as a function of the radius, in the cone-and-plate and plate-and-plate systems are doubtful and this contention is supported by anomalous results for flows in concentric cylinders in which the same measuring technique was employed (see Broadbent et al 1968).…”

Cancellation of errors in the Higashitani-Pritchard treatment of hole pressures generated by viscoelastic liquids in creeping flow past a transverse slot

“…By the Tanner-Giesekus theorem, the Stokes solution for the velocity ~ with a modified pressure p satisfies the second-order fluid equations [14,15,23] 2) The hole-pressure error 1 .02 P* = -?221q~ = ~-U T(Yw) = N~lw/4 , (3.18) where "0 Yw and NOw are the values of disturbed 9 and N 1 at wall and ~ opposite to the slot. Result 2) applies when the depth of pressure-hole d is great enough• According to the numerical evidence presented in [17], the streamwise derivative 02t~l/0q 2 is, in general, non-zero on ~.…”

The application of molecular theories to the behaviour of bulk polymers in steady shear and recovery

“…Rheologica Acta, Band 9, Heft 4 (1970) Total force measurement was employed in this investigation thereby eliminating the uncertainties associated with many of the techniques of pressure measurement in the latter (13).…”