scholarly journals Radial Imbibition in Paper under Temperature Differences

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 86
Author(s):  
Abel López-Villa ◽  
Abraham Medina ◽  
F. J. Higuera ◽  
Jonatan R. Mac Intyre ◽  
Carlos Alberto Perazzo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Porous Material ◽  
Radial Temperature ◽  
Temperature Variations ◽  
One Dimensional ◽  
Blotting Paper ◽  
Dimensional Equation ◽  
The One ◽  
Account Temperature

Spontaneous radial imbibition into thin circular samples of porous material when they have been subjected to radial temperature differences was analyzed theoretically and experimentally. The use of the Darcy equation allowed us to take into account temperature variations in the dynamic viscosity and surface tension in order to find the one-dimensional equation for the imbibition fronts. Experiments using blotting paper showed a good fit between the experimental data and theoretical profiles through the estimation of a single parameter.

Two-Fluid CFD Model of Adiabatic Air-Water Upward Bubbly Flow Through a Vertical Pipe With a One-Group Interfacial Area Transport Equation

2009 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Chris Bailey ◽  
Martin Lopez de Bertodano ◽  
John R. Buchanan
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Bubbly Flow ◽  
Interfacial Area ◽  
Correct Prediction ◽  
Interfacial Area Transport ◽  
One Dimensional ◽  
Interfacial Area Transport Equation ◽  
The One ◽  
Two Fluid

This paper describes in detail the assessment of the CFD code CFX to predict adiabatic liquid-gas two-phase bubbly flow. This study has been divided into two parts. In the first exercise, the effect of Lift Force, Wall Force and the Turbulent Diffusion Force have been assessed using experimental data from the literature for air-water upward bubbly flows through a pipe. The data used here had a characteristic near wall void peaking which was largely influenced by the joint action of the three forces mentioned above. The simulations were performed with constant bubble diameter assuming no bubble interactions. This exercise resulted in selection of the most appropriate closure form and closure coefficients for the above mentioned forces for the range of flow conditions chosen. In the second exercise, the One-Group Interfacial Area Transport equation was introduced in the two-fluid model of CFX. The interfacial area density plays important role in the correct prediction of interfacial mass, momentum and energy transfer and is affected by bubble breakup and coalescence processes in adiabatic flows. The One-Group Interfacial Area Transport Equation (IATE) has been developed and implemented for one-dimensional models and validated using cross-sectional area averaged experimental data over the last decade by various researchers. The original one-dimensional model has been extended to multidimensional flow predictions in this study and the results are presented in this paper. The paper also discusses constraints posed by the commercial CFD code CFX and the solutions worked out to obtain the most accurate implementation of the model.

scholarly journals Assessment of CFD turbulence models for free surface flow simulation and 1-D modelling for water level calculations over a broad-crested weir floodway

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Ahmed M Helmi
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Water Level ◽  
Dimensional Analysis ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
One Dimensional ◽  
The Mean ◽  
The One

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

scholarly journals Numerical Simulation and Experimental Validation of an Oil Free Scroll Compressor

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5863
Author(s):  
Massimo Cardone ◽  
Bonaventura Gargiulo
Keyword(s):  
Experimental Data ◽  
Experimental Validation ◽  
Test Bench ◽  
Outlet Temperature ◽  
Analysis Software ◽  
Scroll Compressor ◽  
One Dimensional ◽  
Geometrical Features ◽  
The One ◽  
Semi Empirical

This paper presents a virtual model of a scroll compressor developed on the one-dimensional analysis software Simcenter Amesim®. The model is semi-empirical: it needs some physical details of the modelled machine (e.g., the cubic capacity), but, on the other hand, it does not require the geometrical features of the spirals, so it needs experimental data to calibrate it. The model also requires rotational speed and the outlet temperature as boundary conditions. The model predicts the power consumption and the mass flow rate and considers leakages and mechanical losses. After the model presentation, this paper describes the test bench and the obtained data used to calibrate and validate the model. At last, the calibration process is described, and the results are discussed. The calculated values fit the experimental data also in extrapolation, despite the model is simple and performs calculations within 7 s. Due to these characteristics, the model is suitable for being used in a larger model as a sub-component.

Effects of Boundary Conditions on the Stability of Slender Viscous Fibers

1984 ◽  
Vol 51 (1) ◽  
pp. 1-5 ◽  
Author(s):  
W. W. Schultz ◽  
S. H. Davis
Keyword(s):  
Surface Tension ◽  
Constant Velocity ◽  
Isothermal Flow ◽  
Constant Force ◽  
Instability Mechanism ◽  
One Dimensional ◽  
Draw Resonance ◽  
The Stability ◽  
The One ◽  
Gravity Surface

The one-dimensional isothermal flow of viscous-liquid fibers displays draw resonance instability when a constant-velocity winder condition is applied. This instability is removed when a constant-force condition occurs at the winder. The instability mechanism is examined and used to explain the stability trends when the effects of gravity, surface tension, inertia, and wind stress are included.

scholarly journals Effect of Pressure Fluctuations on the Temperature During Braking

2020 ◽  
Vol 14 (2) ◽  
pp. 103-107
Author(s):  
Katarzyna Topczewska ◽  
Przemysław Zamojski
Keyword(s):  
Frictional Heating ◽  
Pressure Fluctuations ◽  
Time Dependent ◽  
Maximum Temperature ◽  
Thermal Problem ◽  
Temperature Variations ◽  
One Dimensional ◽  
Metal Ceramic ◽  
The One ◽  
Calculate Temperature Distribution

AbstractThe aim of this study is to develop the numerical–analytical model of frictional heating in a pad/disc system during braking including the pressure fluctuations, engendered by the pump in an anti-skid braking operation. For this purpose, the problem of motion and the one-dimensional thermal problem of friction for a semi-space/semi-space tribosystem were formulated and solved. Obtained solutions allow to calculate temperature distribution on the contact surface and inside the friction elements. Thermal analysis was performed for a metal–ceramic pad and a cast iron disc during one-time braking including the time-dependent, oscillating pressure. The influence of amplitude of pressure fluctuations on the temperature variations was investigated, especially on the value of maximum temperature achieved during braking.

Comparison Between Exact and One-Dimensional Theories for Incipient Melting in Reentry Simulation

1966 ◽  
Vol 88 (4) ◽  
pp. 428-434 ◽  
Author(s):  
Richard A. Matula
Keyword(s):  
Temperature Distribution ◽  
Transient Temperature ◽  
Stagnation Temperature ◽  
Free Flight ◽  
Dimensional Solution ◽  
Radial Temperature ◽  
One Dimensional ◽  
Flight Range ◽  
Wide Range ◽  
The One

The exact transient temperature distribution in a spherical region subjected to an axisymmetric reentry heat flux has been evaluated. The results are presented in terms of nondimensional parameters, therefore they are valid for a wide range of materials, flight conditions, and nose radii. The angular dependence of the surface temperature is given as a function of time. It is also shown that the true radial temperature distribution can be represented by an exponential function. Finally, the solution is applied to reentry ablation onset studies that are being conducted in the free-flight range of the GM Defense Research Laboratories. The exact solution and the one-dimensional theory for the stagnation temperature rise of a model simulating reentry conditions in the free-flight range are compared. It is shown that the validity of the one-dimensional solution is dependent on the flight time, material properties, and nose radius of the model. Assuming that a temperature can be assigned which corresponds to incipient ablation, the present analysis is particularly useful in the prediction of ablation onset.

Large Amplitude Pulsatile Water Flow Across an Orifice

1975 ◽  
Vol 97 (1) ◽  
pp. 92-95 ◽  
Author(s):  
E. L. Yellin ◽  
C. S. Peskin
Keyword(s):  
Large Amplitude ◽  
Heart Valves ◽  
Equation Of Motion ◽  
Separated Flows ◽  
Prosthetic Heart Valves ◽  
One Dimensional ◽  
Water Flows ◽  
Lumped Parameter ◽  
Dimensional Equation ◽  
The One

The pressure-flow relations of large amplitude pulsatile water flows across an orifice have been investigated theoretically and experimentally. By retaining the unsteady term in the one-dimensional equation of motion, and by allowing the jet area to be a function of distance in the continuity equation, a lumped parameter relationship between pressure drop and flow has been developed which reflects the influence of inertia and dissipation. The results are applicable to the analysis of natural and prosthetic heart valves under normal and pathologic conditions. Within the physiologically possible conditions of frequency and flow rate, unsteady separated flows exhibit the same energy losses as comparable steady separated flows. Thus, the flow is quasi-steady, even when the waveforms and temporal relations indicate a significant inertial influence.

Numerical Solution for Two-Dimensional Elastic Wave Propagation in Finite Bars

1967 ◽  
Vol 34 (3) ◽  
pp. 725-734 ◽  
Author(s):  
L. D. Bertholf
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Numerical Solutions ◽  
Step Change ◽  
Two Dimensional ◽  
One Dimensional ◽  
Elastic Bar ◽  
The One ◽  
The Impact

Numerical solutions of the exact equations for axisymmetric wave propagation are obtained with continuous and discontinuous loadings at the impact end of an elastic bar. The solution for a step change in stress agrees with experimental data near the end of the bar and exhibits a region that agrees with the one-dimensional strain approximation. The solution for an applied harmonic displacement closely approaches the Pochhammer-Chree solution at distances removed from the point of application. Reflections from free and rigid-lubricated ends are studied. The solutions after reflection are compared with the elementary one-dimensional stress approximation.

Flow Through a Deformable Porous Material

1975 ◽  
Vol 42 (3) ◽  
pp. 598-602 ◽  
Author(s):  
G. S. Beavers ◽  
T. A. Wilson ◽  
B. A. Masha
Keyword(s):  
Porous Material ◽  
Incompressible Fluid ◽  
Applied Pressure ◽  
Local Stress ◽  
Darcy Law ◽  
Stress Dependence ◽  
One Dimensional ◽  
Flow Through ◽  
Incompressible Media ◽  
The One

A model is presented to describe the one-dimensional flow of an incompressible fluid through a deformable porous material. The model is based on the Forchheimer extension of the Darcy law for flows through incompressible media, where the Forchheimer coefficients are functions of the local stress. Experiments to determine the stress-dependence of the coefficients for polyurethane foam specimens are described. The coefficients are then used in the model to predict the mass flow rate through long polyurethane specimens as a function of the applied pressure difference across the material. The predictions of the model are compared with experimental observations.

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