Fluid Behavior in an Auto-balancing Unit Without External Damping

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.

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Numerical simulation and experimental validation of cavitating flow in a multi-hole diesel fuel injector

International Journal of Engine Research ◽

10.1177/1468087421998631 ◽

2021 ◽

pp. 146808742199863

Author(s):

Aishvarya Kumar ◽

Ali Ghobadian ◽

Jamshid Nouri

Keyword(s):

Computational Cost ◽

Cavitating Flow ◽

Field Analysis ◽

Navier Stokes ◽

Fuel Injector ◽

Fluid Behavior ◽

Flow Field Analysis ◽

Charged Couple Device ◽

Biodiesel Fuels ◽

High Level

This study assesses the predictive capability of the ZGB (Zwart-Gerber-Belamri) cavitation model with the RANS (Reynolds Averaged Navier-Stokes), the realizable k-epsilon turbulence model, and compressibility of gas/liquid models for cavitation simulation in a multi-hole fuel injector at different cavitation numbers (CN) for diesel and biodiesel fuels. The prediction results were assessed quantitatively by comparison of predicted velocity profiles with those of measured LDV (Laser Doppler Velocimetry) data. Subsequently, predictions were assessed qualitatively by visual comparison of the predicted void fraction with experimental CCD (Charged Couple Device) recorded images. Both comparisons showed that the model could predict fluid behavior in such a condition with a high level of confidence. Additionally, flow field analysis of numerical results showed the formation of vortices in the injector sac volume. The analysis showed two main types of vortex structures formed. The first kind appeared connecting two adjacent holes and is known as “hole-to-hole” connecting vortices. The second type structure appeared as double “counter-rotating” vortices emerging from the needle wall and entering the injector hole facing it. The use of RANS proved to save significant computational cost and time in predicting the cavitating flow with good accuracy.

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Simplified Development Method of FEA Code for Sloshing of Floating Roof Tanks (Lagrangian Formulation for Axisymmetric Linear Problem)

Volume 2: Computer Technology and Bolted Joints ◽

10.1115/pvp2014-28117 ◽

2014 ◽

Author(s):

Shoichi Yoshida

Keyword(s):

Linear Problem ◽

Structural Integrity ◽

Three Dimensional ◽

Computational Time ◽

Storage Tanks ◽

Coupling Vibration ◽

Development Method ◽

Oil Storage ◽

Fluid Behavior ◽

Computer Codes

Floating roofs are widely used to prevent evaporation of content in large cylindrical aboveground oil storage tanks. The 2003 Hokkaido Earthquake caused severe damages to the floating roofs due to sloshing. These accidents became a cause to establish structural integrity of the floating roof tanks in sloshing. However, many designers do not have a solution for the sloshing of floating roof tanks except for three-dimensional FEA computer codes. The three-dimensional FEA requires a long computational time and expenses. The sloshing of floating roof tanks is a coupling vibration problem with fluid and structure. The simplified and convenient method has been desired for this solution. This paper presents a simplified development method of a FEA code in the axisymmetric linear problem. It is performed to modify an existing structural analysis code. The fluid behavior is formulated in terms of displacement as the Lagrangian approach.

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Near Critical Condensate Fluid Behavior in Porous Media- A Modeling Approach

SPE Reservoir Engineering ◽

10.2118/17137-pa ◽

1989 ◽

Vol 4 (02) ◽

pp. 221-227 ◽

Cited By ~ 5

Author(s):

John K. Williams ◽

Richard A. Dawe

Keyword(s):

Porous Media ◽

Modeling Approach ◽

Fluid Behavior

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The Onset of Turbulence: Insights Into the Navier-Stokes Equations

Volume 1A, Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Applications of Fluid Mechanics; Pumping Machinery ◽

10.1115/fedsm2017-69491 ◽

2017 ◽

Author(s):

Carl E. Rathmann

Keyword(s):

Stokes Equations ◽

Direct Consequence ◽

Reynolds Numbers ◽

Navier Stokes ◽

Navier Stokes Equation ◽

Navier Stokes Equations ◽

Fluid Behavior ◽

Onset Of Turbulence ◽

And Mathematics ◽

High Reynolds

For well over 150 years now, theoreticians and practitioners have been developing and teaching students easily visualized models of fluid behavior that distinguish between the laminar and turbulent fluid regimes. Because of an emphasis on applications, perhaps insufficient attention has been paid to actually understanding the mechanisms by which fluids transition between these regimes. Summarized in this paper is the product of four decades of research into the sources of these mechanisms, at least one of which is a direct consequence of the non-linear terms of the Navier-Stokes equation. A scheme utilizing chaotic dynamic effects that become dominant only for sufficiently high Reynolds numbers is explored. This paper is designed to be of interest to faculty in the engineering, chemistry, physics, biology and mathematics disciplines as well as to practitioners in these and related applications.

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