A Cavitation Susceptibility Meter With Optical Cavitation Monitoring—Part One: Design Concepts

1991 ◽  
Vol 113 (2) ◽  
pp. 261-269 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Flow Velocity ◽  
Laser Doppler Velocimeter ◽  
Data Generation ◽  
Time Data ◽  
Local Flow ◽  
Potential Core ◽  
Operational Conditions ◽  
Design Concepts ◽  
Custom Made ◽  
Upstream Pressure

This work is concerned with the design of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The operation of the Cavitation Susceptibility Meter is analyzed and the main considerations leading to the proposed design are illustrated and critically discussed. The results of this analysis indicate that the operational range is mainly limited by nuclei interference, flow separation and saturation (choking), and suggest to develop a Cavitation Susceptibility Meter where: (a) the flow possesses a laminar potential core throughout the venturi throat section in all operational conditions; (b) the pressure at the venturi throat is determined from the upstream pressure and the local flow velocity; (c) the detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter; (d) a custom-made electronic Signal Processor incorporating a frequency counter is used for real time data generation and temporary storage; (e) a computerized system performs the final acquisition and reduction of the data.

scholarly journals A Cavitation Susceptibility Meter With Optical Cavitation Monitoring—Part Two: Experimental Apparatus and Results

1991 ◽  
Vol 113 (2) ◽  
pp. 270-277 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Flow Velocity ◽  
Water Samples ◽  
Tap Water ◽  
Laser Doppler Velocimeter ◽  
Viscous Effects ◽  
Time Data ◽  
Local Flow ◽  
Potential Core ◽  
Custom Made ◽  
Experimental Apparatus

This work is concerned with the development and operation of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The pressure at the venturi throat is determined from the upstream pressure and the local flow velocity without corrections for viscous effects because the flow possesses a laminar potential core in all operational conditions. The detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter. A custom-made electronic Signal Processor is used for real time data generation and temporary storage and a computerized system for final data acquisition and reduction. The implementation of the whole system is described and the results of the application of the Cavitation Susceptibility Meter to the measurement of the water quality of tap water samples are presented and critically discussed with reference to the current state of knowledge on cavitation inception.

scholarly journals Separation and Surface Nuclei Effects in a Cavitation Susceptibility Meter

1991 ◽  
Vol 113 (4) ◽  
pp. 695-698 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Laminar Flow ◽  
Flow Velocity ◽  
Flow Separation ◽  
Laser Doppler Velocimeter ◽  
Local Flow ◽  
Applied Tension ◽  
Upstream Pressure ◽  
Finished Glass ◽  
Cavitation Nuclei ◽  
Glass Surfaces

This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM’s with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.

scholarly journals Numerical Flow Characterization around a Type 209 Submarine Using OpenFOAM

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 66
Author(s):  
Ruben J. Paredes ◽  
Maria T. Quintuña ◽  
Mijail Arias-Hidalgo ◽  
Raju Datla
Keyword(s):  
Free Surface ◽  
Flow Velocity ◽  
Surface Effect ◽  
Surface Condition ◽  
Flow Characteristics ◽  
Scaled Model ◽  
Local Flow ◽  
Near Surface ◽  
Vortical Structures ◽  
Operational Conditions

The safety of underwater operation depends on the accuracy of its speed logs which depends on the location of its probe and the calibration thoroughness. Thus, probes are placed in areas where the flow of water is smooth, continuous, without high velocity gradients, air bubbles, or vortical structures. In the present work, the flow around two different submarines is numerically described in deep-water and near-surface conditions to identify hull zones where probes could be installed. First, the numerical setup of a multiphase solver supplied with OpenFOAM v7 was verified and validated using the DARPA SUBOFF-5470 submarine at scaled model including the hull and sail configuration at H/D=5.4 and Fr=0.466. Later, the grid sensitivity of the resistance was assessed for the full-scale Type 209/1300 submarine at H/D=0.347 and Fr=0.194. Free-surface effect on resistance and flow characteristics was evaluated by comparing different operational conditions. Results shows that the bow and near free-surface regions should be avoided due to high flow velocity gradient, pressure fluctuations, and large turbulent vortical structures. Moreover, free-surface effect is stronger close to the bow nose. In conclusion, the probe could be installed in the acceleration region where the local flow velocity is 15% higher than the navigation speed at surface condition. A 4% correction factor should be applied to the probe readings to compensate free-surface effect.

An Advanced Software to Manage a Smart Water Network with Innovative Metrics and Tools Based on Social Network Theory

10.29007/gvnz ◽  
2018 ◽  
Author(s):  
Armando Di Nardo ◽  
Michele Di Natale ◽  
Anna Di Mauro ◽  
Eva Martínez Díaz ◽  
Jose Antonio Blázquez Garcia ◽  
...  
Keyword(s):  
Social Network ◽  
Network Theory ◽  
Water Distribution ◽  
Distribution Networks ◽  
Social Network Theory ◽  
Geographical Information ◽  
Water Network ◽  
Time Data ◽  
Water Losses ◽  
Operational Conditions

The recent development and applications of social network theory in many fields of engineering (electricity, gas, transport, water, etc.) allows both the understanding of networks and to improve their management. Social network theory coupled to the availability of real time data and big data analysis techniques can change drastically the traditional approaches to manage civil networks. Recently, some authors are working to apply this novel approach, based on social network theory, on the water distribution networks using: a) graph partitioning algorithms to define optimal district meter areas both for water losses identification and for water network protection, b) innovative topological, energy and hydraulic indices to analyze performance; and c) GIS (Geographical Information System) to provide a more effective display of results and to improve network behavior in specific operational conditions. In this paper, a novel release 3.5 of SWANP software, that implements all these features, was tested on a real large water network in Alcalá de Henares, Spain.

Using novel methodologies to support burden of disease estimates

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
T Hald
Keyword(s):  
International Development ◽  
Traditional Approach ◽  
Source Population ◽  
Surveillance Systems ◽  
Data Generation ◽  
Time Data ◽  
African Countries ◽  
Indirect Measure ◽  
True Incidence ◽  
Laboratory Capacity

Abstract A challenge to estimating burden of diarrheal diseases, particularly in LMICs, where laboratory capacity and surveillance systems are limited, is obtaining valid estimates of etiology proportions of cases. A commonly used method is systematic review of studies reporting pathogen isolation in diarrhea cases. However, studies often differ in design, source population, timeframe, and pathogens included, hampering extrapolation to the target population. In a study co-funded by the Bill and Melinda Gates Foundation and the UK Department for International Development, we explore a novel approach for estimating diarrhea etiology proportions in urban and rural populations in four African countries. We analyse sewage samples using short-read next-generation sequencing (NGS) to determine abundance of genes that can be mapped to specific bacterial genera, providing an estimate of the relative abundance of specific pathogens in each sample. In parallel to collecting sewage samples, a questionnaire-based population survey will estimate diarrheal incidence. By combining results, pathogen-specific incidence will be estimated and compared with incidence estimates from the traditional approach. The application NGS to human sewage has great potential for surveillance of foodborne infections, particularly in resource-poor settings where laboratory capacity for bacterial isolation is limited. First, NGS is a one method takes all approach, as it is based on detection of RNA/DNA, a language common across pathogens. Second, it is culture independent, allowing for real-time data generation and standardized sharing. Finally, few samples are needed to survey large populations for several pathogens at the same time. Thus, surveillance based on NGS of sewage may prove to be an indirect measure of incidence. Although it will not provide an estimate for the true incidence in the population, it will increase our understanding of the burden and as such be a proxy and novel way of ranking diseases.

scholarly journals Evaluation of the SteamVR Motion Tracking System with a Custom-Made Tracker

2021 ◽  
Vol 11 (14) ◽  
pp. 6390
Author(s):  
Marcin Maciejewski
Keyword(s):  
Motion Tracking ◽  
Tracking System ◽  
Training System ◽  
Random Errors ◽  
Operational Conditions ◽  
Custom Made ◽  
Systematic And Random Errors ◽  
Position And Orientation ◽  
Motion Tracking System ◽  
System Operating

The paper presents the research of the SteamVR tracker developed for a man-portable air-defence training system. The tests were carried out in laboratory conditions, with the tracker placed on the launcher model along with elements ensuring the faithful reproduction of operational conditions. During the measurements, the static tracker was moved and rotated in a working area. The range of translations and rotations corresponded to the typical requirements of a shooting simulator application. The results containing the registered position and orientation values were plotted on 3D charts which showed the tracker’s operation. Further analyses determined the values of the systematic and random errors for measurements of the SteamVR system operating with a custom-made tracker. The obtained results with random errors of 0.15 mm and 0.008° for position and orientation, respectively, proved the high precision of the measurements.

Fiber-coupled self-mixing diode-laser Doppler velocimeter: technical aspects and flow velocity profile disturbances in water and blood flows

1994 ◽  
Vol 33 (24) ◽  
pp. 5628 ◽  
Author(s):  
M. H. Koelink ◽  
F. F. M. de Mul ◽  
A. L. Weijers ◽  
J. Greve ◽  
R. Graaff ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Diode Laser ◽  
Laser Doppler ◽  
Laser Doppler Velocimeter ◽  
Technical Aspects ◽  
Blood Flows ◽  
Flow Velocity Profile

Unsteady critical liquid sheet flows

2017 ◽  
Vol 821 ◽  
pp. 219-247 ◽  
Author(s):  
M. Girfoglio ◽  
F. De Rosa ◽  
G. Coppola ◽  
L. de Luca
Keyword(s):  
Flow Velocity ◽  
Weber Number ◽  
Liquid Sheet ◽  
Global Dynamics ◽  
Equivalent Stiffness ◽  
Supercritical Regime ◽  
Local Flow ◽  
System Perspective ◽  
Linear Approach ◽  
Small Disturbances

The unsteady global dynamics of a gravitational liquid sheet interacting with a one-sided adjacent air enclosure (commonly referred to as nappe oscillation configuration) is addressed under the assumptions of potential flow and the presence of surface tension effects. From a theoretical viewpoint the problem is challenging, because from previous literature it is known that the equation governing the evolution of small disturbances exhibits a singularity at the vertical station where the local flow velocity equals the capillary wave velocity (local critical condition), although the solution to the problem has not yet been found. The equation governing the local dynamics resembles one featuring the forced vibrations of a string of finite length, formulated in the reference frame moving with the flow velocity, and exhibits both slow and fast characteristic curves. From the global system perspective the nappe behaves as a driven damped spring–mass oscillator, where the inertial effects are linked to the liquid sheet mass and the spring is represented by the equivalent stiffness of the air enclosure acting on the displacement of the compliant nappe centreline. A suited procedure is developed to remove the singularity of the integro-differential operator for Weber numbers less than unity. The investigation is carried out by means of a modal (i.e. time asymptotic) linear approach, which is corroborated by numerical simulations of the governing equation and supported by systematic comparisons with experimental data from the literature, available in the supercritical regime only. As regards the critical regime for the unit Weber number, the major theoretical result is a sharp increase in oscillation frequency as the flow Weber number is gradually reduced from supercritical to subcritical values due to the shift of the prevailing mode from the slow one to the fast one.

Statistical Methods for Creep, Fatigue and Fracture Data Analysis

1979 ◽  
Vol 101 (4) ◽  
pp. 344-348 ◽  
Author(s):  
G. J. Hahn
Keyword(s):  
Statistical Methods ◽  
Failure Time ◽  
High Stress ◽  
Problem Definition ◽  
Time Data ◽  
Design Concepts ◽  
Fracture Data ◽  
Fatigue And Fracture ◽  
Creep Fatigue

Statistical methods can play an important role in the proper collection and analysis of creep, fatigue and fracture data. This article deals with what statistics has to offer in this area. The following subjects are considered: The role of statistics in problem definition; the use of stress versus time as the dependent variable in the data fitting; treatment of variability between heats; analysis of data with run-outs; exclusion of extreme high stress-low failure time data from the analysis; experimental design concepts for obtaining the most useful data. The article is based upon a paper prepared at Bob Goldhoff’s suggestion and with his substantial assistance. This paper was originally presented to a 1977 NASA/EPRI/MPC Workshop.

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