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In many cases, journal vibrations in the radial direction have been observed in the various rotating machinery using journal bearing. In this investigation the effects of forced oscillation of a journal on the hydrodynamic pressure profile of a two dimensional plain journal bearing are evaluated. Gambit and ANSYS- Fluent software are used to produce mesh and simulate the flow field respectively. Fluid is Newtonian and viscosity is constant. Also, flow is laminar, isothermal, and heat transfer is neglected. It is assumed that there is no phase change and cavitation does not exist. A user defined function is written in C language and compiled by Fluent to apply the oscillation motion to the journal. Results are obtained for three non-dimensional vibration frequencies of journal (0.001, 0.1 and 1), and two eccentricity ratios (0.54 and 0.8). Results show that the hydrodynamic pressure profile is significantly dependent on the oscillation frequency of journal. It can be observed that the pressure distribution variations are independent of frequency when oscillation frequency is low. However, the pressure distribution is considerably affected by increasing oscillation frequency which leads to appearing different hydrodynamic pressure distribution. These influences become more and more intense by rising non-dimensional vibration frequency ratios specially when it is 1.

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When a Horizontal axis wind turbine works under yaw condition, each blade element can be considered as an oscillating pitch airfoil while the free stream velocity oscillates horizontally. The unsteady free stream velocity, which is usually ignored, oscillates with the same frequency as the airfoil oscillations and has a great impact on the periodic forces produced by the airfoil oscillation. In order to study the effects of unsteady free stream
velocity on the aerodynamic loads, a 2D NACA0012 oscillating airfoil at Reynolds number of 135000 has been simulated. In this simulation, reduced frequency, reduced amplitude and the phase difference between the free stream velocity oscillation and the airfoil angle of attack oscillation are 0.1≤k≤0.25 ، 0.2≤λ≤0.8 و ϕ=0 ,π, respectively. Results show that free stream oscillations affect the aerodynamic loads, vortex strengths
and dynamic stall characteristics. The lift force can be increased by more than 7 times than that of static case and 3 times compared to the load from steady free stream velocity. Depending on 𝜙 value, the dynamic stall angle of attack can be advanced 1 degree or delayed by more than 7 degrees by increase of reduced amplitude. Also, increase of k always causes delay in leading edge vortex formation and consequently delay in dynamic stall occurrence.

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A wind turbine airfoil was analysed, using computational fluid dynamics (CFD) to study the oscillating effects and slip boundary conditions. The slip boundary condition is due to applying superhydrophobic surface. Fluids on these surfaces are repelled. The superhydrophobic surface can delay the icing on blades. The surfaces is assumed at the leading edge; the icing can occur on this region. The chosen oscillation parameters was enough for modelling dynamic stall. The dynamic stall cause a severe loading on the blade. This phenomenon is depicted by two vortices: leading edge vortex and trailing edge vortex. Three reduced frequencies are considered:  in a range of  slip lengths. In this regard, the Transition-SST model is applied for SD7037 airfoil with. The results showed that applying a superhydrophobic surface with low values of the slip length cannot be appropriate during the oscillating motion; but at the slip lengths larger than 100 microns, the aerodynamic coefficients are significantly changed. At the highest reduced frequency, the lift and drag coefficients are reduced about 12% and 40%, respectively. Increasing the slip length postponed the vortex formation and stall angle.