scholarly journals Appendix A: Dimensionless Groups

2007 ◽  
pp. 317-318
Keyword(s):  
Dimensionless Groups

Investigation of the Squeeze Film Dynamics Underneath a Microstructure With Large Oscillation Amplitudes and Inertia Effects

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Nadim A. Diab ◽  
Issam A. Lakkis
Keyword(s):  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Squeeze Film ◽  
Dsmc Method ◽  
Inertia Effects ◽  
Flow Parameters ◽  
Fluid Behavior ◽  
Dimensionless Groups ◽  
Simulation Monte Carlo ◽  
The Impact

This paper presents direct simulation Monte Carlo (DSMC) numerical investigation of the dynamic behavior of a gas film in a microbeam. The microbeam undergoes large amplitude harmonic motion between its equilibrium position and the fixed substrate underneath. Unlike previous work in literature, the beam undergoes large displacements throughout the film gap thickness and the behavior of the gas film along with its impact on the moving microstructure (force exerted by gas on the beam's front and back faces) is discussed. Since the gas film thickness is of the order of few microns (i.e., 0.01 < Kn < 1), the rarefied gas exists in the noncontinuum regime and, as such, the DSMC method is used to simulate the fluid behavior. The impact of the squeeze film on the beam is investigated over a range of frequencies and velocity amplitudes, corresponding to ranges of dimensionless flow parameters such as the Reynolds, Strouhal, and Mach numbers on the gas film behavior. Moreover, the behavior of compressibility pressure waves as a function of these dimensionless groups is discussed for different simulation case studies.

Dynamic Behavior of a Hydraulically Actuated Mechanism. Part 2: Nonlinear Character

1986 ◽  
Vol 108 (2) ◽  
pp. 250-254
Author(s):  
V. Venkatraman ◽  
R. W. Mayne
Keyword(s):  
Dynamic Response ◽  
Transient Response ◽  
Adequate Description ◽  
Linear Behavior ◽  
Transmission Angle ◽  
Dimensionless Groups ◽  
Hydraulically Actuated ◽  
Nonlinear Character ◽  
The Common ◽  
Nonlinear Nature

The first of these papers considering a hydraulically actuated mechanism presents the common oscillating cylinder arrangement and sets of equations which describe the dynamic system. It then defines dimensionless groups that characterize the actuator-mechanism and explores the quasi-linear behavior of the system. This present paper focuses on the nonlinear nature of the system. Effects of transmission angle, mechanism geometry and loading are considered as well as the range of operation in which the small perturbation behavior provides an adequate description of the dynamic response. The paper closes by identifying a new parameter which plays an important role in characterizing the dependence of the system transient response on mechanism geometry.

Atomization of Liquids by Means of a Rotating Cup

1950 ◽  
Vol 17 (2) ◽  
pp. 145-153 ◽  
Author(s):  
J. O. Hinze ◽  
H. Milborn
Keyword(s):  
Working Conditions ◽  
Drop Size ◽  
Film Formation ◽  
Angular Speed ◽  
The State ◽  
Experimental Results ◽  
Drop Formation ◽  
Dimensionless Groups ◽  
Different Types ◽  
Centrifugal Action

Abstract Liquid, supplied through a stationary tube to the inner part of a rotating cup widening toward a brim, flows viscously in a thin layer toward this brim and is then flung off, all by centrifugal action. The flow within this layer and the disintegration phenomena occurring beyond the brim have been studied, experimentally as well as theoretically. A formula has been derived for the thickness and for the radial velocity of the liquid layer within the cup, which proved to agree reasonably well with experimental results. Three essentially different types of disintegration may take place around and beyond the edge of the cup designated, respectively, by: (a) the state of direct drop formation; (b) the state of ligament formation; and (c) the state of film formation. Which one of these is realized depends upon working conditions. Transition from state (a) into (b), or of state (b) into state (c) is promoted by an increased quantity of supply, an increased angular speed, a decreased diameter of the cup, an increased density, an increased viscosity, and a decreased surface tension of the liquid. The experimental results have been expressed in relationships between relevant dimensionless groups. For the state of ligament formation a semiempirical relationship has been derived between the number of ligaments and dimensionless groups determining the working conditions of the cup. Results of drop-size measurements made for the state of ligament formation as well as for the state of film formation show that atomization by mere rotation of the cup is much more uniform than commonly achieved with pressure atomizers.

Study on the Intravenous Lung Assist Device (ILAD) Using PZT Actuators and PVDF Sensors

2008 ◽  
Vol 381-382 ◽  
pp. 353-356
Author(s):  
Gi Beum Kim ◽  
S.J. Kim ◽  
Y.C. Lee ◽  
C.U. Hong ◽  
H.S. Kang ◽  
...  
Keyword(s):  
Transfer Rate ◽  
Semipermeable Membrane ◽  
Gas Transfer ◽  
Scaling Analysis ◽  
Membrane Oxygenator ◽  
Assist Device ◽  
Dimensionless Groups ◽  
Membrane Vibrations ◽  
Insight Into ◽  
Membrane Vibration

The purpose of this study was to investigate the effect of vibration device in gas transfer rate for usage as intravenous lung assist device. Specific attention was focused on the effect of membrane vibration. Quantitative experimental measurements were performed to evaluate the performance of the device, and to identify membrane vibration dependence on hemolysis. Scaling analysis was then used to infer the dimensionless groups that correlate the performance of a vibrated hollow tube membrane oxygenator. The experimental design and procedure are then given for a device for assessing the effectiveness of membrane vibrations. This ILAD is used to provide some insight into how wall vibrations might enhance the performance of an intravascular lung assist device. The time and the frequency response of PVDF sensor were investigated through various frequencies in the ILAD. In these devices, the flow of blood and the source of oxygen were separated by a semipermeable membrane allows oxygen to diffuse into and out of the f1uid, respectively. The results of experiments have shown vibrating ILAD performs effectively.

Determination of Discharge Coefficient for Ball Valves With Calibrated Inserts

2004 ◽  
Author(s):  
Gino James Rouss ◽  
William S. Janna
Keyword(s):  
Discharge Coefficient ◽  
Polynomial Equation ◽  
The Body ◽  
Orifice Diameter ◽  
Flow Parameters ◽  
Dimensionless Groups ◽  
Order Polynomial ◽  
Experimental Process ◽  
Power Law Equation

The valve coefficient was measured for 1, 1-1/4, 1-1/2 and 2 nominal ball valves. A recently designed orifice insert was used with these valves to obtain smaller valve coefficients. Orifice inserts were threaded into the body of a ball valve just upstream of the ball itself. The valve coefficient was measured for every insert used with these valves, and an expression was determined to relate the orifice diameter to other pertinent flow parameters. Two dimensionless groups were chosen to correlate the collected data, and expressions were developed that can be used as aids in sizing the orifice insert needed to obtain the desired valve coefficient. The study has shown that a 2nd order polynomial equation as well as a power law equation can both be used to predict the desired results. Knowing pipe size and schedule, the diameter of the orifice insert needed to obtain the required valve coefficient can be approximated with minimum error. An error analysis performed on the collected data shows that the results are highly accurate, and that the experimental process is repeatable.

The graphical evaluation of ionic dye sorption isotherms using dimensionless groups

1987 ◽  
Vol 34 (8) ◽  
pp. 2777-2791 ◽  
Author(s):  
Ralph McGregor ◽  
Keiko Tamura ◽  
Toshiro Iijima
Keyword(s):  
Sorption Isotherms ◽  
Dimensionless Groups ◽  
Dye Sorption

scholarly journals Dimensional analysis on forest fuel bed fire spread

2018 ◽  
Vol 48 (1) ◽  
pp. 105-110
Author(s):  
Jiann C. Yang
Keyword(s):  
Dimensional Analysis ◽  
Fire Spread ◽  
Fuel Particle ◽  
Wind Condition ◽  
Spread Rate ◽  
Fuel Loading ◽  
Rate Of Spread ◽  
Dimensionless Groups ◽  
Dimensionless Correlations ◽  
Fuel Moisture Content

A dimensional analysis was performed to correlate the fuel bed fire rate of spread data previously reported in the literature. Under wind condition, six pertinent dimensionless groups were identified, namely dimensionless fire spread rate, dimensionless fuel particle size, fuel moisture content, dimensionless fuel bed depth or dimensionless fuel loading density, dimensionless wind speed, and angle of inclination of fuel bed. Under no-wind condition, five similar dimensionless groups resulted. Given the uncertainties associated with some of the parameters used to estimate the dimensionless groups, the dimensionless correlations using the resulting dimensionless groups correlate the fire rates of spread reasonably well under wind and no-wind conditions.

scholarly journals Oxygen Regime Control in Water Body Amelioration

2019 ◽  
Vol 97 ◽  
pp. 05029
Author(s):  
Valery Borovkov ◽  
Ivan Karaichev
Keyword(s):  
Water Body ◽  
Water Mass ◽  
Practical Importance ◽  
Water Bodies ◽  
World Health ◽  
Polluted Water ◽  
Air Bubbles ◽  
Oxygen Regime ◽  
Discharge Velocity ◽  
Dimensionless Groups

An important aspect of water body amelioration is the control of the oxygen regime in water mass. Pollution of water bodies deteriorates their oxygen regime, and the natural inflow of oxygen through the free surface is not enough to compensate for oxygen consumption for pollutant oxidation. Water pollution by various substances causes damage resulting from a decrease in the ecological safety of urban water bodies. Data of World Health Organization (WHO) show that the contact of the population with polluted water bodies causes spreading of deceases, such as cholera, diarrhea, dysentery, hepatitis A, typhoid, and poliomyelitis, and creates considerable health risks. In this context, the artificial aeration of water mass with the use of aeration systems, which improve water quality, is gaining in importance. Most widespread among such aeration systems are diffused-air aerators, in which air supplied by a compressor passes through perforated diffuser plates. The size of the perforation is often chosen with no appropriate hydraulic substantiation. The size of the resulting air bubbles, no doubt, depends on the size of perforation holes; however, the available design relationships give contradictory results depending on the immersion depth of the diffuser plate and the working pressure, which determines air discharge velocity from diffuser plate perforations. This shows that the studies along this line are of scientific and practical importance. This article presents the analysis of the existing relationships for determining the size of air bubbles that form when air is pumped into water through nozzles of different diameters at different pumping rates; the analysis has shown the results of such calculations to differ considerably. Buckingham π-theorem was used to construct dimensionless groups, determining the relationship between the size of bubbles and the factors that govern the outflow of air into water. Dimensionless groups were used to obtain a formula for calculating the size of air bubbles at the aeration of water mass.

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