The mechanism of flow of gases through coniferous wood

1971 ◽  
Vol 177 (1047) ◽  
pp. 197-223 ◽  
Keyword(s):  
Gas Flow ◽  
Strong Support ◽  
Quadratic Function ◽  
Linear Functions ◽  
Modern Theory ◽  
Specific Flow ◽  
Permeability Constant ◽  
Bordered Pits ◽  
Flow Through ◽  
Coniferous Wood

The mechanism of flow of gases through coniferous wood has been examined and found to follow the viscous/slip régime. According to the general theory the specific flow K of a gas in this régime is a linear function of its mean pressure p̅. For coniferous wood, however, we have found that K is a quadratic function of p̅ approximating to a linear one at high enough values of p̅ . It is shown that this is because K is the sum of two linear functions of p̅ , k 1 and k 2 such that 1/ K = 1/ k 1 + 1/ k 2 where k 1 is believed to be the flow through the tracheids alone and k 2 the flow through the bordered pits. It is shown that the permeability constant for viscous flow K v calculated from gas flow is applicable to liquids so that liquid flow can be predicted from gas flow data. With some species the observed flow rate of a liquid differs greatly from the predicted value. Evidence has been obtained that this is because the torus and margo fibrils of the bordered pit are readily displaced by the surface tension and momentum forces developed on them by a liquid causing radical and erratic changes in permeability. Approximate values for the ‘diameter̕ of the smaller flow path have been calculated from the ratio of the viscous to the slip component of flow of k 2 . These were found to be about 1.4 to 1.7 μ m. This is the same order of size as the distances between the torus and the interior of the border of the pit and indicates that it is the geometry of this part of the structure, rather than that of the margo, that controls flow. These results provide strong support for the modern theory of pit structure based on electron microscope photographs.

Experiments on the Resistance Law for Non-Darcy Compressible Gas Flows in Porous Media

1974 ◽  
Vol 96 (4) ◽  
pp. 353-357 ◽  
Author(s):  
B. A. Masha ◽  
G. S. Beavers ◽  
E. M. Sparrow
Keyword(s):  
Reynolds Number ◽  
Porous Material ◽  
Incompressible Flow ◽  
Gas Flow ◽  
Strong Support ◽  
Reynolds Numbers ◽  
Gas Flows ◽  
Pressure Distributions ◽  
Flow Through ◽  
Compressible Gas

Experiments were performed to examine the resistance law for non-Darcy compressible gas flow through a porous material. A particular objective of the investigation was to determine whether a resistance law deduced from incompressible flow experiments could be applied to flows with significant density changes. To this end, the coefficients appearing in the Forchheimer resistance law were first determined from experiments in the incompressible flow regime. These values were then used in an analytical model employing the Forchheimer resistance law to predict streamwise pressure distributions for subsonic compressible flow through the porous material. Corresponding experimental pressure distributions were measured for flow Reynolds numbers up to 81.6. At the highest Reynolds number of the tests the density changed by about a factor of two along the length of the porous medium. The greatest discrepancy between experimental and predicted pressures at any Reynolds number was 2 percent. This agreement lends strong support to the validity of using the incompressible Forchheimer resistance law for subsonic flows in which density changes are significant.

Rarefied Gas Flow Through Long Square Tubes

1971 ◽  
Vol 93 (2) ◽  
pp. 751-754
Author(s):  
Mancil W. Milligan ◽  
Kerry E. Patterson
Keyword(s):  
Theoretical Model ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Molecular Transport ◽  
Rarefied Gas Flow ◽  
Specific Flow ◽  
Self Diffusion ◽  
Slip Boundary ◽  
Cylindrical Tubes ◽  
Flow Through

A theoretical model has been developed for gas flow through long square tubes. The continuum differential equation is solved with noncontinuum slip boundary conditions and the “self-diffusion” or normal molecular transport effect is obtained by numerical integration. Specific flow rates as predicted by this theoretical model are compared with experimental data which were obtained using a 0.0985-in-square tube with argon as the test gas. In addition, a comparison is made using a “hydraulic radius” in the equation which Weber developed for rarefied gas flow through cylindrical tubes. Good agreement between theory and experiment give a high confidence level to the theoretical model.

INVESTIGATION OF THE TIME OF GAS FLOW THROUGH A HOLE IN LONG PIPELINES UNDER HIGH PRESSURE

2020 ◽  
Vol 58 (1) ◽  
pp. 30-43
Author(s):  
N.D. Yakimov ◽  
◽  
A.I. Khafizova ◽  
N.D. Chichirova ◽  
O.S. Dmitrieva ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Flow ◽  
Flow Through

Free area for gas flow through sieve plates with a bubbled bed

1975 ◽  
Vol 40 (11) ◽  
pp. 3315-3318 ◽  
Author(s):  
M. Rylek ◽  
F. Kaštánek ◽  
L. Nývlt ◽  
J. Kratochvíl
Keyword(s):  
Gas Flow ◽  
Flow Through ◽  
Sieve Plates ◽  
Free Area

scholarly journals A Study on Liquid Leak Rates in Packing Seals

2021 ◽  
Vol 11 (4) ◽  
pp. 1936
Author(s):  
Abdel-Hakim Bouzid
Keyword(s):  
Environmental Protection ◽  
Liquid Flow ◽  
Environmental Protection Agency ◽  
Gas Flow ◽  
Outer Boundary ◽  
Health And Safety ◽  
Toxic Substances ◽  
Packing Materials ◽  
Thickness Change ◽  
Flow Through

The accurate prediction of liquid leak rates in packing seals is an important step in the design of stuffing boxes, in order to comply with environmental protection laws and health and safety regulations regarding the release of toxic substances or fugitive emissions, such as those implemented by the Environmental Protection Agency (EPA) and the Technische Anleitung zur Reinhaltung der Luft (TA Luft). Most recent studies conducted on seals have concentrated on the prediction of gas flow, with little to no effort put toward predicting liquid flow. As a result, there is a need to simulate liquid flow through sealing materials in order to predict leakage into the outer boundary. Modelling of liquid flow through porous packing materials was addressed in this work. Characterization of their porous structure was determined to be a key parameter in the prediction of liquid flow through packing materials; the relationship between gland stress and leak rate was also acknowledged. The proposed methodology started by conducting experimental leak measurements with helium gas to characterize the number and size of capillaries. Liquid leak tests with water and kerosene were then conducted in order to validate the predictions. This study showed that liquid leak rates in packed stuffing boxes could be predicted with reasonable accuracy for low gland stresses. It was found that internal pressure and compression stress had an effect on leakage, as did the thickness change and the type of fluid. The measured leak rates were in the range of 0.062 to 5.7 mg/s for gases and 0.0013 and 5.5 mg/s for liquids.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

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