The main aim of this research was to understand the influence of vibration of machine components on lubricating films formed in high-pressure contacts. In the current investigation Spacer Layer Imaging Method has been used to monitor the response of elastohydrodynamic films subjected to lateral and vertical vibrations. For both cases the EHL contact was produced by steel or tungsten carbide ball and a transparent disc which was made of glass or sapphire, loaded against each other. The contacting side of the disc was sputtered with a thin chromium layer and a silica spacer layer. White light was shown onto the contact through a specially built microscope. The interferometric fringes formed by the rays reflected by the chromium layer and by the ball's surface are captured by a high speed CCD camera. The images were subsequently analyzed and converted to film thickness maps according to calibration curves. During the tests conducted under lateral vibrations the effect of several parameters including the frequency of lateral motion, Hertzian pressure, temperature variation and the main entrain speed were investigated. Results have shown that lateral oscillations create ripples through the lubricant film only at highest lateral frequency and low entraining speeds. The parameter which influences the formation of the perturbations in the film is the ratio between the main rolling speed and the lateral speed of the contact. The smaller the ratio the larger the transient phenomena can be identified. It has also been found that temperature change has no significant influence upon the film behaviour. The effect of vertical vibrations on the film thickness was also investigated. The analysis of the film thickness has shown that a sudden increase of load had an effect of increasing the contact diameter and at the same time modified the convergence in the inlet, an enhanced film thickness was produced at the inlet periphery of the initial contact zone and travel through the contact at a velocity equal to the average speed of the contacting surfaces.

The torque associated with overcoming the losses on a rotating disc is of particular importance to the designers of gas turbine engines. Not only does this represent a reduction in useful work, but it also gives rise to unwanted heating of metal surfaces and the adjacent fluid. This research presents a numerical study on the effect of rotor-mounted bolts on the moment coefficient and flow structure within a rotor–stator cavity under conditions representative of modern gas turbine engine design. Steady-state, two-dimensional and three-dimensional, computational fluid dynamics simulations are obtained using the FLUENT commercial code with a standard (k–ω) turbulence model. The model is firstly validated against experimental data and then used to study the effects of presence of rotormounted hexagonal bolts in the rotor-stator cavity under investigation using different dimensionless flow parameters. Also investigated were the effects of changing the number and size of rotor-mounted bolts on the flow structure and amount of losses for two test cases; one corresponding a throughflow dominated condition and the other corresponding a rotationally dominated one. The simulation results showed that decreasing the throughflow rate reduces the area of the wake region causing the wakes to become more circumferential in their path around the bolts. Also it was found that increasing the number and diameter of bolts respectively reduces and increases the area of the wake region. For N>18 a separation bubble forms above the bolt which its length increases with increasing the number of bolts. The total moment coefficient of all bolts in the system increases with increasing the number of bolts. However, the rate of this increase reduces by mounting more bolts. While increasing the diameter of the bolts consistently increases the moment and drag coefficients for the rotationally dominated condition, for the throughflow dominated case an increase and a reduction was observed for respectively the moment and drag coefficients.