Depletion and Retention of Fluid on a Rotating Disk

Abstract

Assuming that a dry circular center is present at which the contact angle between the liquid and solid phases remains constant at all times, the axisymmetric free surface of liquid on a flat disk is determined from the Laplace formula in which the radial gradient of the fluid pressure balances the centrifugal force. The depletion of a thin layer of fluid from a rotating finite disk is described quasi-statically. A remnant of residual fluid is determined to remain on the disk. For moderate rotating speed, this remnant fluid volume is retained on the disk without loss.

Flow of thin liquid film over a rough rotating disk in the presence of a transverse magnetic field

“…Case ii: smooth disk surface (h(r) = 0) and non-negligible liquid surface tension (γ = 0) . This case is an extension of the results presented by [6] and [14] and considers the magnetic effects on the rate of retention of the liquid lubricant. It is observed from Figure 4 that the current results agree with those presented by [6] when M = 0 and that the effect of the magnetic field is to increase the retention of the liquid lubricant for different initial distributions of the height of the lubricant (Figure 4) and for a fixed M( = 0) the effect of the surface tension is to decrease the rate of retention of the liquid lubricant on the smooth spinning disk.…”

“…1. The radius of the disk is large compared with the thickness of the film so that the edge effect is neglected ( [5], [6], [11], [14]). 2.…”

“…Using Laplace formula that relates the fluid pressurep , the surface tension γ and the mean curvature 1 R according to ([7] and [14])p = γ R , with…”

“…As has been pointed out by Tu [14] and Hwang and Ma [6], the boundary conditions at the edge of a finite disk cannot be prescribed in a simple mathematical form due to the complicated edge effect known as 'tea-pot effect'. For thin films, this effect is regarded as a local phenomenon occurring at the edge and is thought …”

“…The production of thin films on substrates placed in the grooves of a rotating disk is referred to as 'spin coating ' in literature and this process is used in the phosphor coatings on television screens, photoresist films on silicon wafers for integrated circuits, for magnetic storage disks, for magnetic paint coating on the substrates etc.. Several theoretical and experimental investigations have been considered by taking into account different aspects of this process ( [3], [5], [6], [8], [9], [11], [12], [14], [15]) and these have been sparked by the importance of the study of the detailed mechanism that retains the lubricant onto the surface of the rotating disk. As a first step towards resolving the discrepancy between the theoretical predictions and experimental results in the thinning of the lubricant layer by centrifugation, Hwang and Ma [6] have explored the effects of surface asperities on the retention of thin liquid films.…”