scholarly journals Rapid Filling Analysis of Pipelines with Undulating Profiles by the Method of Characteristics

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
A. Malekpour ◽  
B. W. Karney
Keyword(s):  
Experimental Data ◽  
Method Of Characteristics ◽  
Computational Grid ◽  
Filling Process ◽  
Pipe System ◽  
The Method Of Characteristics ◽  
Proposed Model ◽  
Water Conveyance ◽  
Filling Analysis ◽  
Transient Events

On the premise of water hammer theory, a numerical model is proposed for simulating the filling process in an initially empty water conveyance pipeline with an undulating profile. Assuming that the pipeline remains full and ignoring air and water interactions in the already filled pipeline, the ongoing filling is simulated using the method of characteristics on an adaptive computational grid. The performance of the model is verified using previously published experimental and rigid column data. The model nicely replicates published experimental data. The model shows that the movement of the filling front into the system can be assumed as a rigid column as long as the flow away from the filling front is undisturbed elsewhere. Furthermore, applying the model to a hypothetical pipe system with an inline-partially open valve shows that the proposed model is robust enough to capture the transient events initiated within the moving column, a vital capability that the existing rigid water column models lack.

MATHEMATICAL MODELING OF THERMOGASDYNAMIC PROCESSES IN PISTON ENGINES

2021 ◽  
pp. 12-17
Author(s):  
A. N. Berdnik ◽  
V. O. Remeslovskiy
Keyword(s):  
Mathematical Modeling ◽  
Experimental Data ◽  
Solitary Waves ◽  
Gas Flow ◽  
Method Of Characteristics ◽  
Finite Amplitude ◽  
Piston Engine ◽  
The Method Of Characteristics ◽  
Turbocharging System ◽  
Calculation Results

A method for calculating the non-stationary gas flow in the exhaust pipeline of a piston engine by the method of solitary waves of finite amplitude is presented. The comparison of experimental data and calculation results by the method of characteristics and obtained when considering the process of propagation of solitary waves through the exhaust pipeline of a piston engine equipped with a pulsed turbocharging system is shown.

Frictional Effects in Unsteady Turbulent Pipe Flows

1997 ◽  
Vol 50 (11S) ◽  
pp. S241-S244 ◽  
Author(s):  
E. B. Wylie
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Method Of Characteristics ◽  
Pipe Flows ◽  
The Method Of Characteristics ◽  
Viscous Losses ◽  
Oscillatory Response ◽  
Transient Events ◽  
Frictional Effects

In the simulation of rapid transient events in fluid-filled pipelines, the method of characteristics is recognized to provide reliable results during the first pressure excursion. However, if a long term oscillatory response of a rapid event is needed, traditional methods of evaluating viscous losses are inadequate in low Reynolds number turbulent flow events. This paper looks at a method to implement frequency-dependent viscous losses in the method of characteristics for turbulent flow and provides comparisons with experimental records.

Dual Release Model to Evaluate Dissolution Profiles from Swellable Drug Polyelectrolyte Matrices

2020 ◽  
Vol 17 (6) ◽  
pp. 511-522 ◽  
Author(s):  
Alicia Graciela Cid ◽  
María Verónica Ramírez-Rigo ◽  
María Celeste Palena ◽  
Elio Emilio Gonzo ◽  
Alvaro Federico Jimenez-Kairuz ◽  
...  
Keyword(s):  
Experimental Data ◽  
Drug Release ◽  
Inflection Point ◽  
Release Profile ◽  
Experimental Point ◽  
Extended Model ◽  
Release Process ◽  
Proposed Model ◽  
Dual Release ◽  
Release Model

Background: Mathematical modeling in modified drug release is an important tool that allows predicting the release rate of drugs in their surrounding environment and elucidates the transport mechanisms involved in the process. Objective: The aim of this work was to develop a mathematical model that allows evaluating the release profile of drugs from polymeric carriers in which the swelling phenomenon is present. Methods: Swellable matrices based on ionic complexes of alginic acid or carboxymethylcellulose with ciprofloxacin were prepared and the effect of adding the polymer sodium salt on the swelling process and the drug release was evaluated. Experimental data from the ciprofloxacin release profiles were mathematically adjusted, considering the mechanisms involved in each stage of the release process. Results: A proposed model, named “Dual Release” model, was able to properly fit the experimental data of matrices presenting the swelling phenomenon, characterized by an inflection point in their release profile. This entails applying the extended model of Korsmeyer-Peppas to estimate the percentage of drug released from the first experimental point up to the inflection point and then a model called Lumped until the final time, allowing to adequately represent the complete range of the drug release profile. Different parameters of pharmaceutical relevance were calculated using the proposed model to compare the profiles of the studied matrices. Conclusion: The “Dual Release” model proposed in this article can be used to predict the behavior of complex systems in which different mechanisms are involved in the release process.

Non-symmetric flow in Laval type nozzles

1972 ◽  
Vol 273 (1232) ◽  
pp. 185-235 ◽  
Keyword(s):  
Steady State ◽  
Combustion Chamber ◽  
Method Of Characteristics ◽  
Three Dimensions ◽  
Symmetric Flow ◽  
Gaseous Flow ◽  
The Method Of Characteristics ◽  
Lateral Forces

The equations of the steady state, compressible inviscid gaseous flow are linearized in a form suitable for application to nozzles of the Laval type. The procedure in the supersonic phase is verified by comparing solutions so obtained with those derived by the method of characteristics in two and three dimensions. Likewise, the solutions in the transonic phase are com pared with those obtained by other investigators. The linearized equation is then used to investigate the nat re of non-symmetric flow in rocket nozzles. It is found that if the flow from the combustion chamber into the nozzle is non-symmetric, the magnitude and direction of the turning couple produced by the emergent jet is dependent on the profile of the nozzle and it is possible to design profiles such that the turning couples or lateral forces are zero. The optimum nozzle so designed is independent of the pressure and also of the magnitude of the non-symmetry of the entry flow. The formulae by which they are obtained have been checked by extensive static and projection tests with simulated rocket test vehicles which are described in this paper.

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