• International Journal of Aerospace System Engineering
• /
• v.8 no.1
• /
• pp.1-13
• /
• 2021

Contra-rotating fan is comprised of two rotors which are rotating in the opposite direction. The fan stages are named rotor-1 and rotor-2. Benefits from the use of contra rotation are in terms of better efficiency and improved thrust to weight ratio. Failure of contra-rotating fan stage blade in-service results in safety risks, repair costs, and revenue losses. This paper focuses on the vibration analysis and one way fluid-structure interaction of high aspect ratio, low speed contrarotating fan rotors. Modal analysis and modal pre-stress analysis of contra-rotating fan rotors were carried out to calculate the natural frequencies, One way fluid-structure interaction (FSI) was carried out where the computational analysis of the blades was performed using ANSYS CFX. The boundary conditions for CFD analysis were considered from the actual experimental velocity flow field at the inlet and pressure outlet. Based on the results obtained from the CFD analysis, the structural analysis such as deformation and Von-Misses stresses was carried out by using the finite element method (FEM) with ANSYS. The results provide necessary guidelines for the safe running of the contra-rotating fan. The analysis also will be helpful to understand the change of flow behavior due to a rotor deformation.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.32 no.1
• /
• pp.38-46
• /
• 2016

Purpose: study for discriminating method of origin side vibration from non-symptomatic clicking group. Materials and Methods: 60 joints vibrations of 30 subjects in non-symptomatic clicking group was recorded via subject's awareness, examiner's palpation and JVA analysis. Origin side vibration was discriminated with consideration for frequency spectrum, time delay and phase shift of waveforms, analysis of numeric values. Results: There were all unilateral vibrations with JVA analysis and number of origin vibrations were 42. 11 pairs of vibrations showed time delay and phase shift and transferred side vibrations showed smaller values of total integral and bigger values of > 300 / < 300 ratio than origin side vibrations except one pair of vibrations. Also as the ipsi-lateral joint vibrations with smaller values of total integral showed bigger values of > 300 / < 300 ratio than the contra-lateral joint vibrations and there all ipsi-lateral vibrations were showed small values of total integral below 10 and hard to detect time delay and phase shift. So the features were used in discrimination of origin side vibrations. Conclusion: There should be all-around considerations for discrimination of origin side vibrations that is frequency spectrum, phase shift and time delay and analysis of numeric values.

• Journal of Korean Association for Spatial Structures
• /
• v.11 no.4
• /
• pp.79-88
• /
• 2011

Recently, complex-shaped tall buildings represented by 3T(Twisted, Tapered, Tilted) are planed largely. A diagrid structural system is one of the most widely used structural system for complex-shaped tall buildings because of its structural efficiency and formativeness. Plans for tilted tall buildings are largely presented because of beauty of a sculpture and many of buildings use diagrid structural systems. Lateral displacements of tilted tall buildings are induced by not only lateral loads but also self weight. Therefore, reduction of lateral responses of tilted tall buildings is as important as typical tall buildings. In this study, a smart TMD is introduced to reduce seismic responses of tilted diagrid tall buildings and its control performance is evaluated. MR damper is employed for the smart TMD and ground-hook controller is used as a control algorithm for the smart TMD. 100-story tall building is used as an example structure. Control performances of uncontrolled case, controlled case with TMD and controlled case with smart TMD are compared and investigated. Numerical simulation has shown that smart TMD presented good control performance for displacement response but acceleration response was not controlled well.