Vol.3, No 15, 2003 pp.1007-1015
UDC 532
Invited Paper

UNIVERSAL EQUATIONS OF UNSTEADY MHD INCOMPRESSIBLE FLUID FLOW WITH VARIABLE
ELECTRO-CONDUCTIVITY ON HEATED MOVING PLATE
Zoran Boričić, Dragiša Nikodijević,
Dragica Milenković, Živojin Stamenković
Faculty of Mechanical Engineering, University of Nis
Aleksandra Medvedeva 14, 18000 Nis, Serbia and Montenegro
Tel.: (+381) 18 524 915, Fax: (+381) 18 524 930, E-mail: dragisan@masfak.ni.ac.yu

Abstract. The laminar, unsteady flow of viscous incompressible fluid caused by moving of semi-infinite flat plate with variable velocity is considered in this paper. The electro-conductivity is assumed as the linear function of velocities ratio. The present external magnetic field is perpendicular to the plate. The fluid properties, except the electro-conductivity, are isotropic and constant. The plate is warmed up (cool down). Dissipation and Joule heat are neglected. For the investigation of described problem the method of "universalisation" is used which has been formulated by L.G.Lojcijanski for boundary layer problems. The universal equations of described problem have been obtained by using this method. The momentum equation of problem is introduced firstly, in order to obtain the universal equations of the described problem. The approximate universal equations of mentioned problem are also given in the paper.
Key words:  MHD incompressible fluid flow, universal equations,
general similarity method.

UNIVERZALNE JEDNAČINE NESTACIONARNOG
MHD STRUJANJA NESTIŠLJIVOG FLUIDA PROMENLJIVE ELEKTROPROVODNOSTI NA ZAGREJANOJ PLOČI
U radu se razmatra laminarno, nestacionarno strujanje, viskoznog, nestišljivog fluida izazvanog kretanjem ravne ploče, promenljivom brzinom. Pretpostavlja se da je elektroprovodnost fluida linearna funkcija odnosa brzina. Prisutno je spoljašnje magnetno polje koje je upravno na ploču. Sve karakteristike fluida, osim elektroprovodnosti su izotropne i konstantne. Ploča je zagrejana (hlađena). Disipacija i Džulova toplota se zanemaruju. Za razmatranje opisanog problema primenjuje se metoda "univerzalizacije" jednačina laminarnog graničnog sloja koju je formulisao L.G. Lojcijanski. Univerzalne jednačine ovog problema su dobijene korišćenjem opisane metode. Pri dobijanju jednačina najpre se uvodi impulsna jednačina opisanog problema. Pridbližne univerzalne jednačine, za dato strujanje takođe su date u ovom radu.