摘要:

From the measurements of F. E. Giesecke on the flow of liquids through submerged orifices two definite laws have been deduced. When the diaphragm is completely closed, the liquid flows backwards along the wall of the tube, and forward in a central vein, the radius of which has been calculated for laminar and turbulent flow. The theory by v. Ka´rma´n for turbulent flow has been applied to a tube of circular cross section. It is shown that both the backward flow and the jet issuing from the orifice are unstable. By an experiment it is made evident that a jet may sometimes describe a spiral motion.

ISSN:0021-8979    

DOI:10.1063/1.1745276

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The viscosity of polyisobutylene (molecular weight about 4900) has been studied from 70°C to 175°C with a falling sphere viscometer and from −53°C to 24°C with a concentric cylinder viscometer. In the measurements with the latter apparatus, elastico‐viscous effects appeared, and the viscous behavior was non‐Newtonian. The apparent viscosities were accordingly extrapolated to zero torque to give values for the viscosity at zero shear. The viscosity ranges from 19 poises at 175°C to 1010poises at −53°C, showing a rather low temperature coefficient. At −76°C, the midpoint of the ``transition region'' for polyisobutylene glass, the viscosity has an extrapolated value of about 1013poises, in agreement with a general rule for glass‐forming materials. Macroscopic and microscopic interpretations of viscosity anomalies are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1745277

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The author recently suggested the introduction of a complex viscosity in the theory of vibrations of materials which lie between the purely crystalline and the liquid state. This conception is utilized here in the theory of compressional waves in an infinite medium. One of the conclusions, namely, the decrease of the attenuation factor with increasing frequency, is in agreement with observations. Another conclusion is an increase of the propagation velocity with frequency. Both changes occur in the neighborhood of a certain characteristic frequency, given by the reciprocal of the so‐called relaxation constant. Below this frequency range the material vibrates like a liquid; above this range like a crystal.

ISSN:0021-8979    

DOI:10.1063/1.1745278

出版商:AIP    

年代:1935

数据来源: AIP