A new method for density gradient measurements in compressible flows

AIAA Journal ◽  
1982 ◽  
Vol 20 (6) ◽  
pp. 820-823 ◽  
Author(s):  
J. Stricker ◽  
O. Kafri
Keyword(s):  
Density Gradient ◽  
Compressible Flows ◽  
New Method ◽  
Gradient Measurements

Density gradient measurements of F2 dissociation rates in shock waves

1973 ◽  
Vol 58 (11) ◽  
pp. 5176-5177 ◽  
Author(s):  
W. Dale Breshears ◽  
Paul F. Bird
Keyword(s):  
Shock Waves ◽  
Density Gradient ◽  
Gradient Measurements

Density Gradient Measurements of O2 Dissociation in Shock Waves

1971 ◽  
Vol 55 (8) ◽  
pp. 4017-4026 ◽  
Author(s):  
W. D. Breshears ◽  
P. F. Bird ◽  
John H. Kiefer
Keyword(s):  
Shock Waves ◽  
Density Gradient ◽  
Gradient Measurements ◽  
O2 Dissociation

Experimental Study Regarding Compressing Process with Assisted Friction Force

2007 ◽  
Vol 23 ◽  
pp. 177-180 ◽  
Author(s):  
Monica Sas-Boca
Keyword(s):  
Experimental Study ◽  
Density Gradient ◽  
Friction Force ◽  
Experimental Results ◽  
New Method ◽  
Powder Flow ◽  
Cold Compaction ◽  
Pressing Force ◽  
Punch Speed ◽  
Specimen Height

Friction between powder and tools plays a major role during cold compaction of PM components with results on the inhomogeneous densification. The present work deals with a new method of compaction for PM components by using the friction force between die and compacts as an active pressing force in order to reduce the density gradient. The proposal technique consists in moving the container of the die, during pressing stage to the punch direction with a well determined speed. As a result, the friction force acts in the same sense as the pressing load with better distribution of powder flow during compaction. The experimental results of compaction parameters versus density have proved the decreasing of the density gradient by increasing die/punch speed rate. A sharp density gradient on the specimen height moving container contrarily to the punch.

scholarly journals Study of Homogeneous Bubble Nucleation in Liquid Carbon Dioxide by a Hybrid Approach Combining Molecular Dynamics Simulation and Density Gradient Theory

2018 ◽  
Author(s):  
Kai Langenbach ◽  
Manfred Heilig ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Density Gradient ◽  
Molecular Model ◽  
Bubble Nucleation ◽  
New Method ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Gradient Theory ◽  
Density Gradient Theory

A new method for predicting homogeneous bubble nucleation rates of pure compounds from vapor-liquid equilibrium (VLE) data is presented. It combines molecular dynamics simulation on the one side with density gradient theory using an equation of state (EOS) on the other. The new method is applied here to predict bubble nucleation rates in metastable liquid carbon dioxide (CO2). The molecular model of CO2 is taken from previous work of our group. PC-SAFT is used as an EOS. The consistency between the molecular model and the EOS is achieved by adjusting the PC-SAFT parameters to VLE data obtained from the molecular model. The influence parameter of density gradient theory is fitted to the surface tension of the molecular model. Massively parallel molecular dynamics simulations are performed close to the spinodal to compute bubble nucleation rates. From these simulations, the kinetic prefactor of the hybrid nucleation theory is estimated, whereas the nucleation barrier is calculated from density gradient theory. This enables the extrapolation of molecular simulation data to the whole metastable range including technically relevant densities. The results are tested against available experimental data and found to be in good agreement. The new method does not suffer from typical deficiencies of classical nucleation theory concerning the thermodynamic barrier at the spinodal and the bubble size dependence of surface tension, which is typically neglected in classical nucleation theory. In addition, the density in the center of critical bubbles and their surface tension is determined as a function of their radius. The usual linear Tolman correction to the capillarity approximation is found to be invalid.

Density gradient measurements of Cl2 dissociation in shock waves

1977 ◽  
Vol 67 (3) ◽  
pp. 881 ◽  
Author(s):  
Robert J. Santoro ◽  
Gerald J. Diebold ◽  
George J. Goldsmith
Keyword(s):  
Shock Waves ◽  
Density Gradient ◽  
Gradient Measurements

GRAVITY VERTICAL GRADIENT MEASUREMENTS FOR THE DETECTION OF SMALL GEOLOGIC AND ANTHROPOGENIC FORMS

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 1016-1030 ◽  
Author(s):  
Zbigniew J. Fajklewicz
Keyword(s):  
Detailed Analysis ◽  
Research Work ◽  
Vertical Gradient ◽  
Industrial Applications ◽  
New Method ◽  
Topographic Correction ◽  
Engineering Problems ◽  
Mine Workings ◽  
The Difference ◽  
Gradient Measurements

The gravity tower vertical gradient has been applied to the solution of a number of important geologic, mining, and engineering problems, particularly to the search for and investigation of geologic structures and the detection of caverns and old mine workings. The effective application of the method depends upon recognizing the difference between the theoretical gravity vertical gradient [Formula: see text] and the gradient [Formula: see text] measured by means of a tower and gravimeter. The former is a derivative of the function g, the latter its differential quotient. Consequently, the differences between [Formula: see text] and [Formula: see text] in the same point may attain high values. Thus, e.g., for a sphere with a radius of 1 m, a density of 2.0 gm/cc and the depth of occurrence of its center equaling 1.2 m, the difference of the theoretical absolute amplitudes [Formula: see text] Eötvös units. Application of the method of the gravity tower vertical gradient on an industrial scale was possible due to the introduction of (1) a new design of the measuring tower, (2) detailed analysis of errors, and (3) a new method of calculating the topographic correction of the gravity vertical gradient. The paper sums up the results of five years of research work and industrial applications. During that period several thousand measurements of the gravity vertical gradient were made.

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