New Corrected Reynolds Equation And Its Numerical Simulation In The Interface Of Head/Disk

The hard disk drive (HDD) has achieved extraordinary growth in areal density of data storage in the past few years. One of the key factors for this explosive growth in storage capacity is the substantially reduced and tiny spacing (flying height) between the read/write head and recording media and the resulting more complex slider design. When the spacing between the flying head and the rotating disk approximates the molecular mean-free path or less, the gas dynamics cannot be described directly from the continuum transport theory, i.e., continuum Reynolds equation, and the gaseous rarefaction effects must be taken into account in this case.Based the FK models of corrected Reynolds that has been used widely in calculating pressure profiles of the interface of head/disk in HDD, a new model of corrected Reynolds considered the gaseous rarefaction effects is proposed, i.e., the model of linearized flow rate (LFR). The implementation of this new model is arrived by using a piecewise linear function to fit the flow rate function of the FK model, and the mathematical formation of the FLR model is simpler more than that of FK model. Moreover, the pressure distribution and the computational speed of FLR model are numerically compared with those of FK model, the results show that the pressure profiles of these two models are almost the same but the computational speed of FLR model is much faster than that of FK model.Due to the non-linearity of Reynolds equation and the complex shape of head slider, numerical methods are used to solve the equations of these two models. Therefore, finite difference method (FDM), least square finite difference (LSFD) method, finite volume method (FVM), meshless local Peterov-Galerkin method (MLPG), and least-square collocation meshless method based reproducing kernel particle idea, are stated detailedly and employed to solve the FLR model of corrected Reynolds equation for different number of discretized nodes, respectively. The resulting pressure distributions and computational speeds are obtained. The pressure profile with a small relative error value can be obtained in the case of the definitive area with a few discretized nodes by using MLPG method, but the computational speed of this method is slow comparing with other several numerical methods. The computational speed and accuracy of LSFD are relatively good in the condition of the definitive area with enough amounts of discretized nodes, unless the computational process is not proceeding. The FDM possesses the fastest computational speed but the accuracy of it is also the worst. The least-square collocation meshless method based reproducing kernel particle idea has a good accuracy with a relatively slow computational speed, noting that the refining parameter should be selected carefully. The FVM is the best numerical method with a fast computational speed and a high accuracy.To more closely test availability of the LFR model, the pressure distributions of the FK model and the LFR model are numerically obtained for the plane inclined slider in two-dimesional case. The computational time of two models in this case are also compared. The numerical reslults show that the pressure distributions of two models have little difference but the computational time of LFR model is less than that of FK model. Than, based on the LFR model, the two-dimensional pressure distributions of several typical positive pressure slider and two negative pressure slider with complex geometry shapes and great pressure gradients are obtained numerically. Some interesting results are found. For the slider having the same geometry shape, under the changing of its sizes and parameters of flying, it may possess entirely different pressure profiles. To obtain the pressure distributions of slider with complex geometry shape and great pressure gradients, it will result in a long computational time or even the failure of computational proceed, unless techniques of the local refining nodes must be implemented. With the reducing of flying height, more numbers of discretized nodes are used to obtain the pressure profiles of the interface of head/disk.