Dynamical Nuclei Measurement: On the Development and the Performance Evaluation of an Optimized Center-Body Meter

1997 ◽  
Vol 119 (4) ◽  
pp. 744-751 ◽  
Author(s):  
T. M. Pham ◽  
J. M. Michel ◽  
Y. Lecoffre
Keyword(s):  
Performance Evaluation ◽  
Bubble Dynamics ◽  
Acoustic Method ◽  
Operating Characteristics ◽  
Mean Flow ◽  
Viscous Effects ◽  
Design Concepts ◽  
Cavitation Nuclei ◽  
Novel Design ◽  
Center Body

This work is concerned with the development of a center-body venturi for nuclei measurements of novel design, the Venturix. Our project aims to: 1. Define a specially tailored geometry for cavitation nuclei measurement. This design study takes into consideration the following main aspects: the venturi mean flow in subcavitating regime, the viscous effects, the bubble dynamics. 2. Evaluate the performance of the meter: After testing the proposed design concepts, the venturi operating characteristics, in particular its operational limits, are assessed. Finally, the performance of the acoustic method used for detecting and counting the active nuclei in the venturi is discussed.

Tilting at wave beams: a new perspective on the St. Andrew’s Cross

2017 ◽  
Vol 830 ◽  
pp. 660-680 ◽  
Author(s):  
T. Kataoka ◽  
S. J. Ghaemsaidi ◽  
N. Holzenberger ◽  
T. Peacock ◽  
T. R. Akylas
Keyword(s):  
Wave Field ◽  
Finite Length ◽  
Line Source ◽  
Cutoff Frequency ◽  
Three Dimensional ◽  
Resonance Phenomenon ◽  
Buoyancy Frequency ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Viscous Effects

The generation of internal gravity waves by a vertically oscillating cylinder that is tilted to the horizontal in a stratified Boussinesq fluid of constant buoyancy frequency, $N$, is investigated. This variant of the widely studied horizontal configuration – where a cylinder aligned with a plane of constant gravitational potential induces four wave beams that emanate from the cylinder, forming a cross pattern known as the ‘St. Andrew’s Cross’ – brings out certain unique features of radiated internal waves from a line source tilted to the horizontal. Specifically, simple kinematic considerations reveal that for a cylinder inclined by a given angle $\unicode[STIX]{x1D719}$ to the horizontal, there is a cutoff frequency, $N\sin \unicode[STIX]{x1D719}$, below which there is no longer a radiated wave field. Furthermore, three-dimensional effects due to the finite length of the cylinder, which are minor in the horizontal configuration, become a significant factor and eventually dominate the wave field as the cutoff frequency is approached; these results are confirmed by supporting laboratory experiments. The kinematic analysis, moreover, suggests a resonance phenomenon near the cutoff frequency as the group-velocity component perpendicular to the cylinder direction vanishes at cutoff; as a result, energy cannot be easily radiated away from the source, and nonlinear and viscous effects are likely to come into play. This scenario is examined by adapting the model for three-dimensional wave beams developed in Kataoka & Akylas (J. Fluid Mech., vol. 769, 2015, pp. 621–634) to the near-resonant wave field due to a tilted line source of large but finite length. According to this model, the combination of three-dimensional, nonlinear and viscous effects near cutoff triggers transfer of energy, through the action of Reynolds stresses, to a circulating horizontal mean flow. Experimental evidence of such an induced mean flow near cutoff is also presented.

Rotational and Quasiviscous Cold Flow Models for Axisymmetric Hybrid Propellant Chambers

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Joseph Majdalani ◽  
Michel Akiki
Keyword(s):  
Rocket Engine ◽  
Navier Stokes ◽  
Mathematical Treatment ◽  
Hybrid Rocket ◽  
Mean Flow ◽  
Viscous Effects ◽  
Navier Stokes Equation ◽  
Flow Models ◽  
Hybrid Rocket Engine ◽  
Wall Injection

In this work, we present two simple mean flow solutions that mimic the bulk gas motion inside a full-length, cylindrical hybrid rocket engine. Two distinct methods are used. The first is based on steady, axisymmetric, rotational, and incompressible flow conditions. It leads to an Eulerian solution that observes the normal sidewall mass injection condition while assuming a sinusoidal injection profile at the head end wall. The second approach constitutes a slight improvement over the first in its inclusion of viscous effects. At the outset, a first order viscous approximation is constructed using regular perturbations in the reciprocal of the wall injection Reynolds number. The asymptotic approximation is derived from a general similarity reduced Navier–Stokes equation for a viscous tube with regressing porous walls. It is then compared and shown to agree remarkably well with two existing solutions. The resulting formulations enable us to model the streamtubes observed in conventional hybrid engines in which the parallel motion of gaseous oxidizer is coupled with the cross-streamwise (i.e., sidewall) addition of solid fuel. Furthermore, estimates for pressure, velocity, and vorticity distributions in the simulated engine are provided in closed form. Our idealized hybrid engine is modeled as a porous circular-port chamber with head end injection. The mathematical treatment is based on a standard similarity approach that is tailored to permit sinusoidal injection at the head end.

Bubble Dynamics and Cavitation Inception in Cavitation Susceptibility Meters

1986 ◽  
Vol 108 (4) ◽  
pp. 444-452 ◽  
Author(s):  
G. L. Chahine ◽  
Y. T. Shen
Keyword(s):  
Bubble Dynamics ◽  
Scaling Effects ◽  
Mean Flow ◽  
Cavitation Inception ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
Tentative Explanation ◽  
Bursting Events ◽  
Acoustic Device ◽  
The Relationship

To improve the understanding of the scaling effects of nuclei on cavitation inception, bubble dynamics, multibubble interaction effects, and bubble-mean flow interaction in a venturi Cavitation Susceptibility Meter are considered theoretically. The results are compared with classical bubble static equilibrium predictions. In a parallel effort, cavitation susceptibility measurements of ocean and laboratory water were carried out using a venturi device. The measured cavitation inception indices were found to relate to the measured microbubble concentration. The relationship between the measured cavitation inception and bubble concentration and distribution can be explained by using the theoretical predictions. A tentative explanation is given for the observation that the number of cavitation bursting events measured by an acoustic device is sometimes an order of magnitude lower than the number of microbubbles measured by the light scattering detector. The questions addressed here add to the fundamental knowledge needed if the cavitation susceptibility meter is to be used effectively for the measurement of microbubble size distributions.

Novel Design Concepts of Efficient Mg-Ion Electrolytes toward High-Performance Magnesium-Selenium and Magnesium-Sulfur Batteries

2017 ◽  
Vol 7 (11) ◽  
pp. 1602055 ◽  
Author(s):  
Zhonghua Zhang ◽  
Zili Cui ◽  
Lixin Qiao ◽  
Jing Guan ◽  
Huimin Xu ◽  
...  
Keyword(s):  
High Performance ◽  
Design Concepts ◽  
Novel Design

Novel design concepts of widely tunable germanium terahertz lasers

1999 ◽  
Vol 40 (3) ◽  
pp. 141-151 ◽  
Author(s):  
E. Bründermann ◽  
D.R. Chamberlin ◽  
E.E. Haller
Keyword(s):  
Design Concepts ◽  
Terahertz Lasers ◽  
Novel Design

Novel Design Concepts of a Compressed Gas HVDC Transmission Line

1982 ◽  
Vol PER-2 (7) ◽  
pp. 57-58
Author(s):  
M. Ouyang ◽  
M. A. Baker ◽  
T. F. Garrity
Keyword(s):  
Transmission Line ◽  
Hvdc Transmission ◽  
Design Concepts ◽  
Compressed Gas ◽  
Novel Design

A theoretical study of viscous effects in peristaltic pumping

1994 ◽  
Vol 279 ◽  
pp. 177-195 ◽  
Author(s):  
Alden M. Provost ◽  
W. H. Schwarz
Keyword(s):  
Wave Propagation ◽  
Pressure Gradient ◽  
Flow Rate ◽  
Mean Flow ◽  
Viscous Effects ◽  
Transverse Waves ◽  
Peristaltic Pumping ◽  
Mean Pressure ◽  
Flow Through ◽  
The Mean

Intuition and previous results suggest that a peristaltic wave tends to drive the mean flow in the direction of wave propagation. New theoretical results indicate that, when the viscosity of the transported fluid is shear-dependent, the direction of mean flow can oppose the direction of wave propagation even in the presence of a zero or favourable mean pressure gradient. The theory is based on an analysis of lubrication-type flow through an infinitely long, axisymmetric tube subjected to a periodic train of transverse waves. Sample calculations for a shear-thinning fluid illustrate that, for a given waveform, the sense of the mean flow can depend on the rheology of the fluid, and that the mean flow rate need not increase monotonically with wave speed and occlusion. We also show that, in the absence of a mean pressure gradient, positive mean flow is assured only for Newtonian fluids; any deviation from Newtonian behaviour allows one to find at least one non-trivial waveform for which the mean flow rate is zero or negative. Introduction of a class of waves dominated by long, straight sections facilitates the proof of this result and provides a simple tool for understanding viscous effects in peristaltic pumping.

Novel design concepts for network intrusion systems based on dendritic cells processes

2013 ◽  
Vol 20 (8) ◽  
pp. 2175-2185
Author(s):  
M. R. Richard ◽  
Guan-zheng Tan ◽  
P. N. F. Ongalo ◽  
W. Cheruiyot
Keyword(s):  
Dendritic Cells ◽  
Design Concepts ◽  
Network Intrusion ◽  
Novel Design
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