Tapered land bearings, unlike the tilting pad bearings, have the pad fixed to the bearing base. The pad is tapered in order to create the natural oil wedge. Because of the fixed thickness profile, these bearings are designed for specific conditions. A typical pad of a tapered land bearing is shown in the Figure 7-20.

The hatched area in the figure is the tapered area and rest of the area is flat. The flat areas near the inner and outer diameter edges are called the inner and outer dam. The width of the inner and outer dams are d1 and d2, respectively. The arc angle for the tapered area is denoted γt ri and ro are the inner and outer radius of the pad, respectively. Two types of grooves are usually used in the tapered bearings: one in which the groove makes a constant arc angle about the center as shown in the Figure 7-20 and the second in which the groove is of constant width as shown in Figure 7-21. On the tapered area, a linear variation of the thickness is assumed.

The local y direction in the constant arc groove bearing is considered to be passing through the leading edge of the pad. If the initial clearance at the outer diameter side of the trailing edge is hte, and the tapered depth on inner and outer diameter side is hi and ho, respectively, then the film thickness in the tapered area can be approximated as

where Θit,te is the azimuthal angle of the trailing edge side of the tapered area of the ith pad from the local y direction, defined as

In the tapered land bearing, part of the area near the inner diameter and outer diameter is in general used as dam. Also, the complete area in the circumferential direction is not tapered, rather some area near the trailing edge is left flat. Therefore, the film thickness variation on the ith sector of symmetry can be given as

where hg is the depth of the groove.

Determination of the film thickness profile in a constant width groove bearing requires the determination of the coordinates of various points on the pad surface. Figure 7-22 shows the geometry of the pad in a constant width groove bearing in more detail.

The local y direction is in this case considered to pass from the center of the groove as opposed to the leading edge of the pad in other cases.

From the triangle formed by the radial directions rp and r

In the above expression, r can vary from the inner radius ri to outer radius ro. Since the pad depths at trailing edge outer diameter, and the relative depth of the pad from this location to the leading edge outer and inner diameter are known, the film thickness variation in the tapered area can be calculated by assuming a linear variation in radial and circumferential directions:

The thicknesses h0, hr, and hθ are yet unknown. They can be determined by the following information:

Using this information, the height variation in the tapered area of the ith pad is calculated as