Mohammed Debiane - Academia.edu (original) (raw)
Uploads
Papers by Mohammed Debiane
Comptes Rendus. Mécanique
The effects of inert assisting gas nature and velocity on laser cut qual- ity are investigated. A... more The effects of inert assisting gas nature and velocity on laser cut qual- ity are investigated. A pure fusion cutting process just above melting point is con- sidered, where the molten steel velocity is given as a function of the two acting forces represented by the pressure gradient and the frictional forces applied by the laminar gas flow. In the case of nitrogen assisting gas, the stainless steel melt film exhibits a visible separation point. The point where the melt flow is separated out from the solid wall depends strongly on the gas velocity. It is pushed down the cut surface when the gas velocity is increased. Furthermore, we have investgated the use of different inert gases (nitrogen, argon and helium) to blow the molten material out of the kerf, and it was noted that the argon and the nitrogen gases evacuate more easily the molten metallic film, compared to the helium gas from their cooling rates point of view. It is concluded that the two first gases are more efficient in ...
Comptes Rendus. Mécanique
Comptes Rendus Mécanique, 2006
Comptes Rendus Mécanique, 2004
European Journal of Mechanics - B/Fluids
The method developed by M. S. Longuet-Higgins [J. Inst. Math. Appl. 22, 261-273 (1978; Zbl 0391.7... more The method developed by M. S. Longuet-Higgins [J. Inst. Math. Appl. 22, 261-273 (1978; Zbl 0391.76018)] for the calculation of steady gravity waves is extended to steady capillary-gravity waves in deep water. Introduction of surface tension provides an additional term in the quadratic identities between the Fourier coefficients in Stokes’s expansion. This term is reduced to a simple function of the slope of the local tangent to the profile of the free surface. A set of nonlinear algebraic equations is derived and solved using Newton’s method. Good agreement is found between the present results and those given by previous methods. Limiting profiles of gravity-like waves are accurately calculated, and a new family of limiting gravity waves is found.
Les résonances posent le problème de l'unicité des solutions d'un champ de vagues et pa... more Les résonances posent le problème de l'unicité des solutions d'un champ de vagues et par conséquent celui de leur recherche. Plus généralement elles donnent lieu à des difficultés pour les applications que l'on peut faire de la mesure des vagues afin de mieux quantifier ...
L’etude des champs tridimensionnels est essentielle pour une description realiste des ondes inter... more L’etude des champs tridimensionnels est essentielle pour une description realiste des ondes internes. La forme la plus simple de ces vagues est celle des ondes a courtes cretes. La methode que nous proposons pour leur calcul est basee sur celle du lagrangien moyen de Whitham. Cette technique nous a permis de calculer leurs profils et d’effectuer une etude de leurs caracteristiques fondamentales.
a. Département de Physique, Université M’Hamed Bougara de Boumerdes, Avenue de l’Independance, Bo... more a. Département de Physique, Université M’Hamed Bougara de Boumerdes, Avenue de l’Independance, Boumerdes 35000, Algeria b. Faculté de Physique, Université des Sciences et de la Technologie Houari Boumedienne, B.P. 32 El Alia, Algiers 16111, Algeria c. Institut de Recherche sur les Phénomènes Hors Equilibre ,Technopole de Chateau-Gombert, 49 rue F.Joliot-Curie, B.P.146,13384 Marseille Cedex 13, France
European Journal of Mechanics - B/Fluids, 2016
Abstract Linear superharmonic stability analysis of nonlinear short-crested gravity interfacial w... more Abstract Linear superharmonic stability analysis of nonlinear short-crested gravity interfacial waves between two semi-infinite fluids is numerically investigated. Like short-crested free surface waves, superharmonic instabilities correspond to the harmonic resonance phenomenon. The basic flow is calculated with a perturbation method and expansions are summed using Pade approximants. It is found that these instabilities develop near the poles due to harmonic resonance. The obtained results show that the instability of maximal growth rate develops for a density ratio μ = 0.08 and occurs sporadically. In addition, for μ = 0.34 , the maximum growth rate is negligible and hence, for this value the short-crested interfacial waves are stable to superharmonic perturbations.
Egs General Assembly Conference Abstracts, 2002
A new type of steady steep two-dimensional irrotational symmetric periodic gravity waves on invis... more A new type of steady steep two-dimensional irrotational symmetric periodic gravity waves on inviscid incompressible fluid of infinite depth is revealed. The Bernoulli equation is quadratic in velocity and admits two values of the particle speed at the crest. The first one is smaller than the wave phase speed c and corresponds to the Stokes branch. The second one is greater than c and should correspond to a new type of waves. These waves are found to have sharper crests in comparison with the Stokes waves of the same wavelength and steepness. Because of this we named them "the spike waves". To give numerical evidence we used several independent methods: (i) Fourier approximations. The elevation (x) of a free surface and the velocity po- tential (x, y) are looked for in the form of series in terms of the basis functions exp(inx) and exp n(y + ix) , respectively, x and y being the horizontal and vertical coordinates, and n being a positive integer. (ii) Fourier approximations with singularities. The basis functions for the velocity po- n tential are 1/ 1 - exp(y0 - y - ix) , y0 being a free parameter. Herein a countable number of isolated singular points at y = y0 are to be located outside the flow do- main for calculating potential periodic progressive waves. Otherwise, the local vortex structures may be studied. (iii) Inverse Fourier approximations. The velocity potential and the stream function are used as independent variables. The spatial coordinates are expanded into series in terms of the functions exp n(-/c + i/c) . For the almost-highest spike waves, the routine may converge to different sets of val- ues for the unknowns depending on starting conditions. This non-uniqueness is pos- sibly caused by the superharmonic or crest instabilities, which were investigated in detail by Longuet-Higgins et al. for the Stokes branch. The results obtained for the almost-highest Stokes waves are in sufficient agreement with the high accuracy calcu- lations by the program of Prof. M. Tanaka, which he kindly placed at our disposal. This research has been supported by INTAS Grant 99-1637.
Comptes Rendus Mécanique, 2016
The effects of the nature and velocity of inert assisting gas on the cut quality of a 4 mm stainl... more The effects of the nature and velocity of inert assisting gas on the cut quality of a 4 mm stainless steel plate are presented in this study. It is assumed that the whole absorbed laser energy is used in melting the kerf volume, which means that we deal with a pure fusion cutting process. The velocity of molten steel is given as a function of the two acting forces on it: the pressure gradient and the frictional forces of gas flow. In the case of nitrogen assisting gas, the stainless steel melt film exhibits a clear separation point which depends strongly on the gas velocity. Indeed, we have obtained a displacement of its position when the gas velocity is increased. The influence of the nature of the inert gas on the quality of the cut surface is also investigated. For that, various inert gases (nitrogen, argon and helium) are used to blow the molten material out of the kerf without taking into account the transverse movement of the treated workpiece. We have noted that argon and nit...
Convective, conductive and radiative exchanges are investigated for the case of heat transfer in ... more Convective, conductive and radiative exchanges are investigated for the case of heat transfer in a pipe subjected to a nonuniform circumferential flux, and a semianalytical solution for the resulting wall temperature is developed. A discussion of the influence of such prominent parameters as Reynolds number, wall thickness and temperature level is undertaken to determine the relative importance of all the heat transfer processes involved.
L’étude des champs tridimensionnels est essentielle pour une description réaliste des ondes inter... more L’étude des champs tridimensionnels est essentielle pour une description réaliste des ondes internes. La forme la plus simple de ces vagues est celle des ondes à courtes crêtes. La méthode que nous proposons pour leur calcul est basée sur celle du lagrangien moyen de Whitham. Cette technique nous a permis de calculer leurs profils et d’effectuer une étude de leurs caractéristiques fondamentales.
Comptes Rendus. Mécanique
The effects of inert assisting gas nature and velocity on laser cut qual- ity are investigated. A... more The effects of inert assisting gas nature and velocity on laser cut qual- ity are investigated. A pure fusion cutting process just above melting point is con- sidered, where the molten steel velocity is given as a function of the two acting forces represented by the pressure gradient and the frictional forces applied by the laminar gas flow. In the case of nitrogen assisting gas, the stainless steel melt film exhibits a visible separation point. The point where the melt flow is separated out from the solid wall depends strongly on the gas velocity. It is pushed down the cut surface when the gas velocity is increased. Furthermore, we have investgated the use of different inert gases (nitrogen, argon and helium) to blow the molten material out of the kerf, and it was noted that the argon and the nitrogen gases evacuate more easily the molten metallic film, compared to the helium gas from their cooling rates point of view. It is concluded that the two first gases are more efficient in ...
Comptes Rendus. Mécanique
Comptes Rendus Mécanique, 2006
Comptes Rendus Mécanique, 2004
European Journal of Mechanics - B/Fluids
The method developed by M. S. Longuet-Higgins [J. Inst. Math. Appl. 22, 261-273 (1978; Zbl 0391.7... more The method developed by M. S. Longuet-Higgins [J. Inst. Math. Appl. 22, 261-273 (1978; Zbl 0391.76018)] for the calculation of steady gravity waves is extended to steady capillary-gravity waves in deep water. Introduction of surface tension provides an additional term in the quadratic identities between the Fourier coefficients in Stokes’s expansion. This term is reduced to a simple function of the slope of the local tangent to the profile of the free surface. A set of nonlinear algebraic equations is derived and solved using Newton’s method. Good agreement is found between the present results and those given by previous methods. Limiting profiles of gravity-like waves are accurately calculated, and a new family of limiting gravity waves is found.
Les résonances posent le problème de l'unicité des solutions d'un champ de vagues et pa... more Les résonances posent le problème de l'unicité des solutions d'un champ de vagues et par conséquent celui de leur recherche. Plus généralement elles donnent lieu à des difficultés pour les applications que l'on peut faire de la mesure des vagues afin de mieux quantifier ...
L’etude des champs tridimensionnels est essentielle pour une description realiste des ondes inter... more L’etude des champs tridimensionnels est essentielle pour une description realiste des ondes internes. La forme la plus simple de ces vagues est celle des ondes a courtes cretes. La methode que nous proposons pour leur calcul est basee sur celle du lagrangien moyen de Whitham. Cette technique nous a permis de calculer leurs profils et d’effectuer une etude de leurs caracteristiques fondamentales.
a. Département de Physique, Université M’Hamed Bougara de Boumerdes, Avenue de l’Independance, Bo... more a. Département de Physique, Université M’Hamed Bougara de Boumerdes, Avenue de l’Independance, Boumerdes 35000, Algeria b. Faculté de Physique, Université des Sciences et de la Technologie Houari Boumedienne, B.P. 32 El Alia, Algiers 16111, Algeria c. Institut de Recherche sur les Phénomènes Hors Equilibre ,Technopole de Chateau-Gombert, 49 rue F.Joliot-Curie, B.P.146,13384 Marseille Cedex 13, France
European Journal of Mechanics - B/Fluids, 2016
Abstract Linear superharmonic stability analysis of nonlinear short-crested gravity interfacial w... more Abstract Linear superharmonic stability analysis of nonlinear short-crested gravity interfacial waves between two semi-infinite fluids is numerically investigated. Like short-crested free surface waves, superharmonic instabilities correspond to the harmonic resonance phenomenon. The basic flow is calculated with a perturbation method and expansions are summed using Pade approximants. It is found that these instabilities develop near the poles due to harmonic resonance. The obtained results show that the instability of maximal growth rate develops for a density ratio μ = 0.08 and occurs sporadically. In addition, for μ = 0.34 , the maximum growth rate is negligible and hence, for this value the short-crested interfacial waves are stable to superharmonic perturbations.
Egs General Assembly Conference Abstracts, 2002
A new type of steady steep two-dimensional irrotational symmetric periodic gravity waves on invis... more A new type of steady steep two-dimensional irrotational symmetric periodic gravity waves on inviscid incompressible fluid of infinite depth is revealed. The Bernoulli equation is quadratic in velocity and admits two values of the particle speed at the crest. The first one is smaller than the wave phase speed c and corresponds to the Stokes branch. The second one is greater than c and should correspond to a new type of waves. These waves are found to have sharper crests in comparison with the Stokes waves of the same wavelength and steepness. Because of this we named them "the spike waves". To give numerical evidence we used several independent methods: (i) Fourier approximations. The elevation (x) of a free surface and the velocity po- tential (x, y) are looked for in the form of series in terms of the basis functions exp(inx) and exp n(y + ix) , respectively, x and y being the horizontal and vertical coordinates, and n being a positive integer. (ii) Fourier approximations with singularities. The basis functions for the velocity po- n tential are 1/ 1 - exp(y0 - y - ix) , y0 being a free parameter. Herein a countable number of isolated singular points at y = y0 are to be located outside the flow do- main for calculating potential periodic progressive waves. Otherwise, the local vortex structures may be studied. (iii) Inverse Fourier approximations. The velocity potential and the stream function are used as independent variables. The spatial coordinates are expanded into series in terms of the functions exp n(-/c + i/c) . For the almost-highest spike waves, the routine may converge to different sets of val- ues for the unknowns depending on starting conditions. This non-uniqueness is pos- sibly caused by the superharmonic or crest instabilities, which were investigated in detail by Longuet-Higgins et al. for the Stokes branch. The results obtained for the almost-highest Stokes waves are in sufficient agreement with the high accuracy calcu- lations by the program of Prof. M. Tanaka, which he kindly placed at our disposal. This research has been supported by INTAS Grant 99-1637.
Comptes Rendus Mécanique, 2016
The effects of the nature and velocity of inert assisting gas on the cut quality of a 4 mm stainl... more The effects of the nature and velocity of inert assisting gas on the cut quality of a 4 mm stainless steel plate are presented in this study. It is assumed that the whole absorbed laser energy is used in melting the kerf volume, which means that we deal with a pure fusion cutting process. The velocity of molten steel is given as a function of the two acting forces on it: the pressure gradient and the frictional forces of gas flow. In the case of nitrogen assisting gas, the stainless steel melt film exhibits a clear separation point which depends strongly on the gas velocity. Indeed, we have obtained a displacement of its position when the gas velocity is increased. The influence of the nature of the inert gas on the quality of the cut surface is also investigated. For that, various inert gases (nitrogen, argon and helium) are used to blow the molten material out of the kerf without taking into account the transverse movement of the treated workpiece. We have noted that argon and nit...
Convective, conductive and radiative exchanges are investigated for the case of heat transfer in ... more Convective, conductive and radiative exchanges are investigated for the case of heat transfer in a pipe subjected to a nonuniform circumferential flux, and a semianalytical solution for the resulting wall temperature is developed. A discussion of the influence of such prominent parameters as Reynolds number, wall thickness and temperature level is undertaken to determine the relative importance of all the heat transfer processes involved.
L’étude des champs tridimensionnels est essentielle pour une description réaliste des ondes inter... more L’étude des champs tridimensionnels est essentielle pour une description réaliste des ondes internes. La forme la plus simple de ces vagues est celle des ondes à courtes crêtes. La méthode que nous proposons pour leur calcul est basée sur celle du lagrangien moyen de Whitham. Cette technique nous a permis de calculer leurs profils et d’effectuer une étude de leurs caractéristiques fondamentales.