Steady state seepage flow through zoned earth structures affected by permeability defects

2010 ◽  
pp. 327-332
Keyword(s):  
Steady State ◽  
Seepage Flow ◽  
Earth Structures ◽  
Flow Through

Conservative and nonconservative inhibitors of gastric acid secretion

1987 ◽  
Vol 253 (3) ◽  
pp. G359-G368 ◽  
Author(s):  
E. B. Ekblad ◽  
V. Licko
Keyword(s):  
Steady State ◽  
Acid Secretion ◽  
Initial Step ◽  
No Net Loss ◽  
Apparent Loss ◽  
H2 Antagonist ◽  
Flow Through ◽  
Ph Stat ◽  
High Concentrations ◽  
Continuous Presence

Inhibitors of the initial step (H2-antagonist) and of the final step (thiocyanate, SCN-; and nitrite, NO2-) were used to study the dynamics of acid secretion in isolated frog gastric mucosa. Tissues were mounted in flow-through chambers, and the acid secretion rate (SR) was recorded on a pH-stat microprocessor. Continuous presence of H2-antagonist decreases the SR to a lower steady state, and on removal the SR returns to basal SR, causing a net loss of acid, the nonconservative effect. The amount of lost acid is a unique function of exposure, thus, independent of the patterns (pulses or steps) of inhibition. In contrast, continuous presence of SCN- or NO2- (below 3 mM) results in an undershoot in SR with a return to basal SR, whereas at higher concentrations there is no return. Removal of these inhibitors causes an overshoot in SR with return to basal SR. The rebound acid is equal to acid suppressed by NO2- and low concentration of SCN-, resulting in no net loss of acid, the conservative effect, whereas at high concentrations of SCN- there is an apparent loss of acid. In maximally secreting tissue the overshoot of SR is not observed. However, the acid is not lost, merely delayed. In resting tissue NO2- also merely delays the exit of the acid produced in response to forskolin. The rebound acid is proposed to reside in a sequestered "acid" pool that is stable for at least 120 min. Results with NO2- and SCN- suggest an effect on a saturable exit enzyme, possibly the K+-H+-ATPase.

scholarly journals Simulation and Modeling of Flow in a Gas Compressor

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Anna Avramenko ◽  
Alexey Frolov ◽  
Jari Hämäläinen
Keyword(s):  
Steady State ◽  
Mass Flow ◽  
Gas Flow ◽  
Simulation Method ◽  
High Mass ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Flow Through

The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.

Experimental, Numerical, and Statistical Investigation of Two Phase Flow in a Cylindrical Perforation Tunnel

2021 ◽  
Author(s):  
Ekhwaiter Abobaker ◽  
Abadelhalim Elsanoose ◽  
Mohammad Azizur Rahman ◽  
Faisal Khan ◽  
Amer Aborig ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Steady State ◽  
Statistical Analysis ◽  
Flow Rate ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Gas Flow Rate ◽  
Two Phase ◽  
Flow Through

Abstract Perforation is the final stage in well completion that helps to connect reservoir formations to wellbores during hydrocarbon production. The drilling perforation technique maximizes the reservoir productivity index by minimizing damage. This can be best accomplished by attaining a better understanding of fluid flows that occur in the near-wellbore region during oil and gas operations. The present work aims to enhance oil recovery by modelling a two-phase flow through the near-wellbore region, thereby expanding industry knowledge about well performance. An experimental procedure was conducted to investigate the behavior of two-phase flow through a cylindrical perforation tunnel. Statistical analysis was coupled with numerical simulation to expand the investigation of fluid flow in the near-wellbore region that cannot be obtained experimentally. The statistical analysis investigated the effect of several parameters, including the liquid and gas flow rate, liquid viscosity, permeability, and porosity, on the injection build-up pressure and the time needed to reach a steady-state flow condition. Design-Expert® Design of Experiments (DoE) software was used to determine the numerical simulation runs using the ANOVA analysis with a Box-Behnken Design (BBD) model and ANSYS-FLUENT was used to analyses the numerical simulation of the porous media tunnel by applying the volume of fluid method (VOF). The experimental data were validated to the numerical results, and the comparison of results was in good agreement. The numerical and statistical analysis demonstrated each investigated parameter’s effect. The permeability, flow rate, and viscosity of the liquid significantly affect the injection pressure build-up profile, and porosity and gas flow rate substantially affect the time required to attain steady-state conditions. In addition, two correlations obtained from the statistical analysis can be used to predict the injection build-up pressure and the required time to reach steady state for different scenarios. This work will contribute to the clarification and understanding of the behavior of multiphase flow in the near-wellbore region.

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