Time evolution of accreting magnetofluid around a compact object-Newtonian analysis

2015 ◽  
Vol 24 (10) ◽  
pp. 1550077 ◽  
Author(s):  
Fahimeh Habibi ◽  
Mahboobeh Shaghaghian ◽  
Reza Pazhouhesh

Time evolution of a thick disc with finite conductivity around a nonrotating compact object is presented. Along with the Maxwell equations and the Ohm's law, the Newtonian limit of the relativistic fluid equations governing the motion of a finitely conducting plasma is derived. The magnetofluid is considered to possess only the poloidal components of the electromagnetic field. Moreover, the shear viscous stress is neglected, as well as the self-gravity of the disc. In order to solve the equations, we have used a self-similar solution. The main features of this solution are as follows. The azimuthal velocity is somewhat increased from the Keplerian value in the equator plane to the super-Keplerian values at the surface of disc. Moreover, the radial velocity is obtained proportional to the meridional velocity. Magnetofluid does not have any nonzero component of the current density. Subsequently, the electromagnetic force is vanished and does not play any role in the force balance. While the pressure gradient maintains the disc structure in latitudinal direction, magnetofluid has no accretion on the central compact object. Analogously to the parameter α in the standard model, our calculations contain one parameter η0 which specifies the size of the electrical resistivity.

1992 ◽  
Vol 3 (4) ◽  
pp. 319-341 ◽  
Author(s):  
S. P. Hastings ◽  
L. A. Peletier

We discuss the self-similar solutions of the second kind associated with the propagation of turbulent bursts in a fluid at rest. Such solutions involve an eigenvalue parameter μ, which cannot be determined from dimensional analysis. Existence and uniqueness are established and the dependence of μ on a physical parameter λ in the problem is studied: estimates are obtained and the asymptotic behaviour as λ → ∞ is established.


1972 ◽  
Vol 40 (3) ◽  
pp. 484-486 ◽  
Author(s):  
K. E. Lonngren ◽  
W. F. Ames ◽  
H. C. S. Hsuan ◽  
I. Alexeff ◽  
William Wing

1993 ◽  
Vol 251 ◽  
pp. 355-375 ◽  
Author(s):  
Laurence Armi ◽  
Richard Williams

The steady hydraulics of a continuously stratified fluid flowing from a stagnant reservoir through a horizontal contraction was studied experimentally and theoretically. As the channel narrows, the flow accelerates through a succession of virtual controls, at each of which the flow passes from sub-critical to supercritical with respect to a particular wave mode. When the narrowest section acts as a control, the flow is asymmetric about the narrowest section, supercritical in the divergent section and self- similar throughout the channel. With increased flow rate a new enclosed self-similar solution was found with level isopycnals and velocity uniform with depth. This flow is only symmetric in the immediate neighbourhood of the narrowest section, and in the divergent section remains supercritical with respect to higher internal modes, has separation isopycnals and splits into one or more jets separated by regions of stagnant, constant-density fluid. Flows which are subcritical with respect to lowest modes can also be asymmetric about the narrowest section for higher internal modes. The experiments are interpreted using steady, inviscid hydraulic theory. Solutions require separation isopycnals and regions of stationary, constant-density fluid in the divergent section.


2008 ◽  
Vol 617 ◽  
pp. 283-299 ◽  
Author(s):  
E. S. BENILOV ◽  
V. S. ZUBKOV

We consider an infinite plate being withdrawn (at an angle α to the horizontal, with a constant velocity U) from an infinite pool of viscous liquid. Assuming that the effects of inertia and surface tension are weak, Derjaguin (C. R. Dokl. Acad. Sci. URSS, vol. 39, 1943, p. 13.) conjectured that the ‘load’ l, i.e. the thickness of the liquid film clinging to the plate, is l=(μU/ρgsinα)1/2, where ρ and μ are the liquid's density and viscosity, and g is the acceleration due to gravity.In the present work, the above formula is derived from the Stokes equations in the limit of small slopes of the plate (without this assumption, the formula is invalid). It is shown that the problem has infinitely many steady solutions, all of which are stable – but only one of these corresponds to Derjaguin's formula. This particular steady solution can only be singled out by matching it to a self-similar solution describing the non-steady part of the film between the pool and the film's ‘tip’.Even though the near-pool region where the steady state has been established expands with time, the upper, non-steady part of the film (with its thickness decreasing towards the tip) expands faster and, thus, occupies a larger portion of the plate. As a result, the mean thickness of the film is 1.5 times smaller than the load.


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