Browsing by Author "Kessal, Mohand"

Now showing 1 - 8 of 8

Adiabatic expansion effect of natural gas at the downstream extremity of the pipeline
(AIP Publishing, 2017) Kessal, Mohand; Amara, Khadidja; Belaidi, Idir
Analysis of cavitating flow through a venturi
(2015) Zamoum, Mohammed; Kessal, Mohand
A dynamical study of a bubbly flows in a transversal varying section duct (Venturi), is modeled by the use of the mass and momentum phases equations, which are coupled with the Rayleigh-Plesset equation of the bubbles dynamics. The effects of the throat dimension and the upstream void fraction on flow parameters are investigated. The numerical resolution of the previous equations set let us found that the characteristics of the flow change dramatically with upstream void fraction. Two different flow regimes are obtained: a quasi-steady and a quasi-unsteady regimes. The former is characterized by a large spatial fluctuations downstream of the throat, which are induced by the pulsations of the cavitation bubbles. The quasi-unsteady regime corresponds to flashing flow in which occurs a bifurcation at the flow transition between these regimes. This transition occurs at Rc 4.3 which corresponds to s 4.710-3. An analytical expression for the critical bubble size at the flashing flow point is also obtained and compared with theoretical data
Local bifurcation analysis of one parameter in the greitzer’s model with a general compressor characteristic
(Springer, 2022) Naima Meskine, Naima; Kessal, Mohand; Seba, Djamila
Based on the Greitzer’s reduced model, an analytical study on the instabilities phenomena of the operating point is presented using some basic properties of the nonlinear dynamic system. Moreover, a proposal of a general compressor characteristic curve, that suits the stationary system, is given. The Routh–Hurwitz theorem is applied to determine the stability conditions on the model parameters. An analysis along with a discussion is presented when the compression system goes to the Hopf bifurcation point during surge. For the Hopf bifurcation case, an approximate expression, for the periodic cycle of the system’s solution from the equilibrium point, is obtained and the direction is determined using Lyapunov’s stability theory. A numerical simulation is executed to illustrate the theoretical results
Numerical investigation of cavitating flow in a horizontal converging-diverging nozzle
(2021) Zamoum, Mohammed; Boucetta, Rachid; Kessal, Mohand
The objective of this paper is to investigate the dynamic evolution of cavitating flow in a horizontal converging-diverging Venturi nozzle. A nonlinear continuum bubbly mixture model coupled with the dynamics equation of the bubble is used to investigate the effects of the throat dimension of converging-diverging nozzle. Equation set is numerically resolved by the use of a fourth order Runge-Kutta scheme. The numerical resolution of the previous equations set let us found that the bubble radius distribution, fluid velocity and fluid pressure change dramatically with the throat length of the Venturi and an instability appeared just after the passing the converging nozzle for an throat length greater than 4.2 cm which correspond to the critical bubble radius Rc= 6.85. Also, we found that, the throat dimension of converging diverging nozzle has strongly affected the bubble frequency and the characteristics of the flow
Numerical investigation of wax deposition features in a pipeline under laminar flow conditions
(Elsevier, 2022) Boucetta, Rachid; Haddad, Zoubida; Zamoum, Mohammed; Kessal, Mohand; Arıcı, Müslüm
Wax deposit inside pipelines continues to be a critical issue in the oil and gas industry. The available wax deposition data in the literature are currently insufficient to construct viable predictive numerical methods that capture all wax deposit features. Therefore, more research studies are required to improve our understanding of the physics of wax-deposition phenomena. In the present paper, a numerical study is performed to predict the temporal and spatial distribution of the porous wax deposit during laminar flow in a pipe. A mathematical model which combines the energy and momentum balance equations and molecular diffusion model by Fick's law is employed to better describe the wax deposit. Validation with experimental data as well as numerical results and characteristics of wax deposition are presented. The results revealed that an increase in the deposition time and porosity leads to a significant increase in the wax deposit content and pressure drop, and a decrease in the fluid temperature, heat transfer coefficient, and flow rate. However, an increase in porosity leads to larger variation of these parameters over a short period of time. Further, it is demonstrated that the wax deposit is concentrated over a short axial length, and its maximum which appears at X/L = 0.014 is kept unchanged with time and porosity variation
Numerical modeling of transients in gas pipeline
(Academic Journals, 2014) Kessal, Mohand; Boucetta, Rachid; Zamoum, Mohammed; Tikobaini, Mourad
A set of equations governing an isothermal compressible fluid flow is analytically and numerically analyzed. The obtained equations are written in characteristic from and resolved by a predictorcorrector lambda sceme for the interior mesh points. The method of characteristics (MOC) is used for the boundaries. Advantages of explicit form of these schemes and the flexibility of the MOC are used for an isothermal fast transient gas flow in short pipeline. The results, obtained for a simple practical application agree with those of other methods
Numerical study of unsteady flow regime in a natural gas pipe
(Politechnica University of Bucharest, 2023) Benzerhouda, Amar; Boucetta, Rachid; Khelifi Touhami, Mohamed Salah; Kessal, Mohand
In this study, isothermal gas flow characteristics in a long pipeline are monitored and controlled using two mathematical models and the finite difference approach. These models, which take into account continuity, motion, and the equation of state, are based on one-dimensional nonlinear partial differential equations. Results are consistent with the body of literature, supporting their applicability in the present. Higher inclinations have a noticeable impact on output flow rates when examining the effects of pipe inclination on gas flow under similar pressure. A significant contribution of this work is the analysis of stabilization time across inclinations, which reveals pressure shifts and flow steadying after 5000 s. These findings are useful for the energy sector because they help pipeline operators and engineers maintain a safe, effective gas flow.
On cauchy conditions for asymmetric mixed convection boundary layer flows : conditions de Cauchy pour une couche limite de convection mixte asymétrique
(Elsevier, 2003) Amaouche, Mustapha; Kessal, Mohand
The fundamental question of how and where does an asymmetric mixed convection boundary layer flow around a heated horizontal circular cylinder begin to develop is raised.We first transform the classical boundary layer equations by using an integral method of Karman– Pohlhausen type and obtain two coupled equations governing the evolutions of the dynamic and thermal boundary layers. Because of its global character, the implemented method allows to bypass the difficulty of downstream–upstream interactions. Cauchy conditions characterizing the starting of the boundary layers are found; they are obtained in a surprisingly simple manner for the limiting cases corresponding to Pr = 1, Pr→0 and Pr→∞. Otherwise, these conditions can be found by using a prediction correction algorithm. Some numerical experiments are finally performed in order to illustrate the theory