A multiple image photographic technique for recording the path and velocity of moving objects

Uhlherr, P. H. T.; Sinclair, C. G.; Baxter, Bill

doi:10.1016/0009-2509(65)80099-9

Cited by 8 publications

(1 citation statement)

References 5 publications

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“…Indeed, helical descents have been observed in Newtonian fluids and this is attributed to the rotation of the wake which eventually induces the sphere to follow a spiral trajectory; see Viets (1971), Achenbach (1974) and Clift, et al (1978). Direct measurement of the spiral motion of falling spheres has been documented by Uhlherr, Sinclair and Baxter (1965) as an example of their multiple image photographic technique for recording the path and velocity of moving objects. There are no details of the sphere diameters used in their experiment, nor of their densities, nor of the fluid used, which presumably was water for ease of photography.…”

Section: Discussionmentioning

confidence: 99%

On the Instability of Spheres Settling through a Vertical Pipe Filled with HPG

2012

JAFM

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An extensive set of experiments were performed to determine the stability boundary for the longitudinal oscillation of steel spheres settling through Hydroxy Propyl Guar (HPG) contained in long vertical tubes, a phenomenon first reported by Mollinger, et al. (1999). Results are reported in d/D-pH parameter space, where d is the sphere diameter and D is the internal diameter of a tube. Longitudinal oscillations, which owe their existence to the self-healing nature of the gel, occur over the region 0.48 < d/D < 0.86 and 8.31 < pH < 8.82. We discover that the upper pH limit of this stability domain is linked to the HPG gel point. During the course of experimentation, additional instabilities in the form of high-frequency transverse oscillations or helical motions were discovered and documented. The pure transverse oscillations found in the domain 8.035 < pH < 8.31 and 0.9 < d/D < 0.6 result from the elastic nature of the guar in this region. For 6.25 < pH < 8.035 transverse oscillations or stable descents are interspersed between bands of tight helical motion at large d/D and wide helical motion at low d/D. At the lowest value pH = 6.25 the guar is a Newtonian fluid, yet the spiral motion persists in small bands of d/D. We have verified, in the literature and through additional experiments using distilled water as the Newtonian liquid that the spiral motion of spheres falling inside vertical tubes does indeed exist. We undertook a repetition of the experiment reported in Mollinger, et al. (1999) to determine the entire region

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Section: Discussionmentioning

confidence: 99%

On the Instability of Spheres Settling through a Vertical Pipe Filled with HPG

2012

JAFM

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Geometry of bluff body wakes

Kalra

Uhlherr

1973

Can J Chem Eng

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The attached recirculating wake zone has been experimentally investigated for spheres, spherical caps and circular discs normal to the flow. Tracer photography in a water tunnel was employed for the measurements. Results are presented over the range of Reynolds number from 20 to 400. The following wake properties are presented as a function of Reynolds number: angle of separation for spheres; wake length for spheres and discs, wake volume for all three types of body. The results for separation angle are in good agreement with the data available from the literature, both experimental and theoretical. Wake length results for spheres are also in agreement with published values and with values obtained from published numerical solutions of the equations of motion. Wake volume results for spheres are similarly in agreement with values calculated from published wake dimensions obtained both experimentally and theoretically. Spherical caps are found to have the wake volume either of discs if they are thin (h/D <0.3) or of spheres if they are thick (h/D > 0.6). Caps of intermediate thickness to diameter ratio show a transition between sphere‐like and disc‐like behavior. This behavior is explained in terms of the separation angle on spheres.

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Wall effect for the fall of spheres in cylindrical tubes at high reynolds number

Uhlherr

Chhabra

1995

Can J Chem Eng

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New experimental results on the wall effect for sphere motion in cylindrical tubes are presented and discussed for the conditions dlD 5 0.9 and Re,,, I 2oooO. Extensive comparisons with previous studies have been carried out to evaluate their predictability and to demonstrate the utility of the present results.The wall factor, defined as the ratio of settling velocity in an unbounded medium to that measured in a cylindrical tube, is found to depend on sphere-to-tube diameter ratio and on sphere Reynolds number. However, for small values of the Reynolds number (Re 0.5), as well for large values (Re 2 loOO), the Reynolds number dependence of the wall factor disappears; in these regions, only the dependence on diameter ratio remains. De nouveaux rksultats exHrimentaux sur l'effet de paroi pour le dtplacement des sphbres dans des tubes cyclindriques sont prtsentks et analyds pour les conditions dlD s 0,9 Re,,, S 2000. On a effectue des c o m p s o n s ~OUS&S avec les ktudes antkrieures afin d'tvaluer la caractbre praictif du modble et de dtmontrer I'utilitk des prtsents r6sultats.On a trouvt que le facteur de paroi, dtfini c o m e le rapport entre la vitesse de dkantation dans un milieu infini et la vitesse dans un tube cylindrique, dtpendait du rapport de diamktre sphkres-tube et du nombre de Reynolds des sphtres. Cependant, pour le petites valeurs du nombre de Reynolds (Re s 0.5) c o m e pour les grands (Re I IOOO), la dtpendance du facteur de paroi par rapport au nombre: de Reynolds disparait; dans ces rkgions, seule subsiste la dkpendance par rapport au rapport des diambtres.Keywords: sphere drag, wall effect, terminal velocity. onfining walls are well known to exert a retarding C effect on a sphere in free fall. A knowledge of the wall

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A multiple image photographic technique for recording the path and velocity of moving objects

Cited by 8 publications

References 5 publications

On the Instability of Spheres Settling through a Vertical Pipe Filled with HPG

On the Instability of Spheres Settling through a Vertical Pipe Filled with HPG

Geometry of bluff body wakes

Wall effect for the fall of spheres in cylindrical tubes at high reynolds number

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