Prof. Richard Selescu
Department of Aerodynamics,
“Elie Carafoli” National Institute for Aerospace Research – INCAS
“Elie Carafoli” National Institute for Aerospace Research – INCAS
220, Bd. Iuliu Maniu, Code 061126, Sector 6, Bucharest, ROMANIA
Phone: +40 21 434 0083; Fax: +40 21 434 0082;
rselescu@aero.incas.ro web page: http://www.incas.ro
Abstract: The Aim of the Work: This intrinsic analytic study was done with the aim of improving and enriching the knowledge about the local physical phenomena encountered in both fluid mechanics and magneto-fluid dynamics, elaborating a new physical & mathematical model of fluid flow and magnetic field, by using a special type of coordinate system. It continues a series of works presented by the author at the 5th WCNA and at some WSEAS conferences in 2008, representing a real deep insight into the still hidden theory of isoenergetic flow, this one being a lesser known domain in the physical sciences (approaching some new special topics in classical potential theory, fluid mechanics, aerothermodynamics and magneto-hydrodynamics, including plasma). So far, to the best of the author’s knowledge, nowhere in the world literature a method to obtain the general case of first integrability for the vector equations of motion has been considered, but very particular cases only. These include the vector equation of motion in the steady and unsteady inviscid (or viscous) fluid mechanics (D. Bernoulli and D. Bernoulli-Lagrange integrals), the vector equation of motion and the “magnetic induction” one in magneto-hydrodynamics, as well as the system of these two simultaneous vector equations in magneto-hydrodynamics. As its title shows, this work is fully original.
Key-Words and Phrases: rotational flows, steady and unsteady flows, virtual “isentropic” (Bernoulli’s) surfaces, inviscid and viscous fluids, compressible fluids, flow of an electroconducting fluid in an external magnetic field; Selescu’s vectors, space curves (vector lines) and virtual “zero-work” surfaces
2000 Mathematics Subject Classification: 31 Potential theory; 70 Mechanics of particles and systems; 76 Fluid mechanics; 78 Optics, electromagnetic theory; 80 Classical thermodynamics, heat transfer
Extended Abstract: A model of the isoenergetic flow of an inviscid fluid was introduced, in order to establish a simpler form for the general PDE of the velocity potential. It consists mainly in using an intrinsic system of triorthogonal curvilinear coordinates (one of them being tied to the local specific entropy value). The choice of this system enables the treatment of any 3-D flow (rotational, steady and unsteady) as a potential 2-D one, introducing a 2-D velocity “quasi-potential”, specific to any isentropic surface. The dependence of the specific entropy on this velocity “quasi-potential” was also established. On the above surfaces the streamlines are orthogonal paths of a family of lines of equal velocity “quasi-potential”. This model can be extended to some special (but usual) cases in magneto-plasma dynamics (taking into account the flow vorticity effects, as well as those of the Joule–Lenz heat losses), considering a non-isentropic flow of an inviscid electroconducting fluid in an external magnetic field. There always are some space curves along which the motion equation admits a first integral, making evident a new physical quantity – Selescu’s magneto-hydrodynamic vector $. For a fluid with an infinite electric conductivity (like highly ionized plasma), these curves are the flow isentropic lines, also enabling the treatment of any 3-D flow as a “quasi-potential” 2-D one. The model was extended to the viscous Newtonian fluid flows and to visco-magnetic flows of conducting fluids respectively, introducing some “zero-work” (for the non-conservative terms) surfaces, some new physical quantities – Selescu’s vectors (roto-viscous Ş, Şi, roto-visco-magnetic §, and magnetic Şm), new intrinsic coordinate systems, and a 2-D magnetic “quasi-potential”, searching for and finding first integrals for the motion equation in viscous fluid mechanics and in MHD, and for the equation of magnetic induction (separately treated), the last one in a similar way to the vortex equation for a viscous Newtonian incompressible fluid. The new model was analyzed in order to find a case of first integrability in MHD for the system of motion and magnetic induction simultaneous equations, establishing a special procedure for finding such first integrals. In almost all cases treated, the newly found first integrals are similar to D. Bernoulli and D. Bernoulli–Lagrange ones, being obtained by a procedure for eliminating the non-conservative terms in the respective equations. The PDE of the velocity potential, that of the isentropic surfaces, as well as those of Selescu’s vector lines and zero-work surfaces, were also given.
Plenary Speakers' Brief Biography: Dr.Richard Selescu graduated as an engineer from the Polytechnic Institute Bucharest, the Faculty of Mechanics, Department of Aircraft Engineering in 1970. He is working in the National Institute for Aerospace Research “Elie Carafoli’’ – INCAS, Department of Aerodynamics, at the Trisonic Wind Tunnel Laboratory. He received his PhD degree in Aerodynamics and Fluid Mechanics at the Aerospace Engineering Faculty of the “Politehnica” University Bucharest in 1999. Among the research fields of interest, he approached the analytic modeling in aerodynamics, fluid mechanics and magnetofluid dynamics. Thus, he introduced the following nomenclature: the isentropic surfaces and a 2-D velocity quasi-potential function on these surfaces (in fluid mechanics); the zero-work surfaces for the non-conservative terms in the motion equation (in viscous fluid mechanics and magnetofluid dynamics); some new physical quantities – the roto-viscous vector (in Newtonian viscous fluid mechanics), the incompressible roto-viscous vector (in viscous incompressible fluid mechanics, for the vortex equation), the magneto-hydrodynamic vector (in inviscid magnetofluid dynamics), the roto-visco-magnetic vector (in viscous magnetofluid dynamics) and the magnetic vector (in visco-magnetic magnetofluid dynamics, for the equation of magnetic induction); a new shock-free axisymmetric supersonic flow – the tronconical flow (in supersonic aerogasdynamics); the similarity depth for satisfying the gas-hydrodynamic analogy (in supercritical hydrodynamics).
