11130

10246

كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مهندسي مكانيك

1394

سيزده، 79ص.: مصور

حميدرضا ميردامادي

سعيد ضيايي راد

رضا تكيني، ساره گلي

1395/01/18

مهندسي مكانيك

ID10246

Vibrations and Probabilistic Stability Analysis of Carbon Nano Tubes Conveying Fluid Based on Stochastic Flow Velocity Mehdi Rahmati mehdi rahmati@me iut ac ir Date of Submission 2016 1 17 Department of Mechanical Engineering IsfahanUniversity of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Hamidreza Mirdamadi hrmirdamadi@cc iut ac irAbstract In most of fluid structure interaction analysis in engineering systems velocity of the fluid flow isassumed constant and deterministic as time passes while in this study the flow velocity is modeled as arandom process In this thesis the strain inertia gradient theory and knudsen number are employed in orderto consider the effects of nano structure and nano flow respectively In continuation the Hamiltonianfunction symplectic transformation and polar conversion are utilized in order to reach a standard form Now by assuming a stationary Gaussian random process for the velocity of fluid flow the stochasticaveraging method is used Then the drift and diffusion coefficients of It s equations are calculated andthereafter the stability of second moment of vibration amplitude is investigated In the sequel the mean andstandard deviation of vibration amplitude of system are obtained by solving the Fokker Planck Kolmogorovequation In this thesis the symplectic transformation is obtained by means of the Genetic algorithm whichis employed to decouple the equations of model without the effects of perturbation on system and only thefirst mode divergence instability has been studied due to ineffectiveness of this transformation for flowvelocities greater than the critical velocity corresponding to divergence of the first mode The results of thepresent study show that structural damping and mass per unit length of fluid are more effective in thestochastic instability analysis rather than the deterministic one In addition for non zero values of spectraldensity the strain inertia gradient theory predicts a higher mean flow velocity rather than strain gradienttheory On the other hand by enhancing the mean flow velocity the maximum safe value of spectraldensity decreases for stability In both deterministic and stochastic instability analysis considering slipregime for liquid fluid causes insignificant changes in unstable mean flow velocity while noticing thiseffect for gas fluid causes a sharp decrease of unstable mean flow velocity Keywords Nanotube conveying fluid Strain inertia gradient theory Slip flow regime Stochasticflow velocity Stochastic averaging method Fokker Planck Kolmogorov equation

حميدرضا ميردامادي

سعيد ضيايي راد

رضا تكيني، ساره گلي