scholarly journals Discussion: “The Rate of Growth of Vapor Bubbles in Superheated Water” (Dergarabedian, P., 1953, ASME J. Appl. Mech., 20, pp. 537–545)

1954 ◽  
Vol 21 (2) ◽  
pp. 201-202
Author(s):  
J. T. Sinnette
Keyword(s):  
Superheated Water ◽  
Vapor Bubbles ◽  
Rate Of Growth

scholarly journals The Rate of Growth of Vapor Bubbles in Superheated Water

1953 ◽  
Vol 20 (4) ◽  
pp. 537-545
Author(s):  
Paul Dergarabedian
Keyword(s):  
Bubble Radius ◽  
Equation Of Motion ◽  
Heat Diffusion ◽  
Air Bubbles ◽  
Finite Range ◽  
Superheated Water ◽  
Vapor Bubbles ◽  
Bubble Wall ◽  
Air Content ◽  
Rate Of Growth

Abstract Calculations are presented for the dynamic stability of vapor and air bubbles in superheated water. These calculations indicate that the values of the bubble radii for which the equilibrium is unstable are restricted to a finite range of radii whose values are governed by the temperature of the water and the initial air content in the bubble. Two theoretical solutions for the rate of growth of these unstable bubbles are considered: (a) Solution of the equation of motion of the bubble radius with the assumption that there is no heat diffusion across the bubble wall; (b) solution which includes the effect of heat diffusion. The two solutions differ appreciably. These two solutions are then compared with the experimental data on the growth of the vapor bubbles in superheated water. This comparison shows agreement with the solution with the effect of heat diffusion included.

Characterization of a Superheated Water Jet Released Into Water Using Proper Orthogonal Decomposition Method

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Avick Sinha ◽  
Rajesh O. Chauhan ◽  
Sridhar Balasubramanian
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Water Jet ◽  
Orthogonal Decomposition ◽  
Superheated Water ◽  
Vapor Bubbles ◽  
Ambient Conditions ◽  
Mean Flow ◽  
The Mean ◽  
Proper Orthogonal ◽  
External Characteristics

The external characteristics of a superheated water jet released into water at ambient conditions are dominated by the vapor bubble formation, which results in an unsteady flow dynamics. This hinders the use of classical methods to assess the mean flow and the turbulence characteristics. Here, the proper orthogonal decomposition (POD) technique was employed on the velocity measurements obtained using particle image velocimetry (PIV) to quantify the external characteristics of a superheated water jet released into water. This was done at three different inlet pressure ratios. From the energy modes obtained using the POD technique, it was observed that the first mode well represents the mean flow, while subsequent higher modes show the fluctuating nature. The phase-averaged properties were calculated by considering only the first mode. Unlike a canonical jet, the maximum value of the mean centerline velocity for a superheated jet occurs far downstream from the nozzle, at x/D ≈ 15, due to the thermal nonequilibrium in the jet attributed to the formation of vapor bubbles. The turbulent kinetic energy (TKE), size of the coherent structures (CS), and swirling strength showed a nonmonotonic decrease in the downstream direction, indicating that the vapor formation has significant influence on the jet dynamics. The novel aspect of this work is the use of POD technique for phase averaging, using which dynamics of a superheated jet have been quantified. The distribution of vapor bubbles in the flow field was also measured using the Shadowgraphy technique to substantiate the above observations.

Economic Growth: New Problems and New Risks

2006 ◽  
pp. 20-37 ◽  
Author(s):  
M. Ershov
Keyword(s):  
Economic Growth ◽  
Foreign Exchange ◽  
Driving Force ◽  
Structural Changes ◽  
Rate Of Growth

The economic growth, which is underway in Russia, raises new questions to be addressed. How to improve the quality of growth, increasing the role of new competitive sectors and transforming them into the driving force of growth? How can progressive structural changes be implemented without hampering the rate of growth in general? What are the main external and internal risks, which may undermine positive trends of development? The author looks upon financial, monetary and foreign exchange aspects of the problem and comes up with some suggestions on how to make growth more competitive and sustainable.

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