University of Tehran Press Journal of Computational Applied Mechanics 2423-6713 51 1 2020 06 01 Investigation of instable fluid velocity in pipes with internal nanofluid flow based on Navier-Stokes equations 122 128 76984 10.22059/jcamech.2020.300244.496 EN Mohammad Hosein Fakhar Department of Mechanical Engineering, Kashan Branch, Islamic Azad University, Kashan, Iran Ahmad Fakhar Department of Mechanical Engineering, Kashan Branch, Islamic Azad University, Kashan, Iran Hamidreza Tabatabaei Department of Mechanical Engineering, Kashan Branch, Islamic Azad University, Kashan, Iran Hossein Nouri-Bidgoli Department of Mechanical Engineering, Kashan Branch, Islamic Azad University, Kashan, Iran Journal Article 2020 04 01 In this article, the instable fluid velocity in the pipes with internal nanofluid is studied. The fluid is mixed by SiO2, AL2O3, CuO and TiO2 nanoparticles in which the equivalent characteristic of nanofluid is calculated by rule of mixture. The force induced by the nanofluid is assumed in radial direction and is obtained by Navier-Stokes equation considering viscosity of nanofluid. The displacements of the structure are described by first order shear deformation theory (FSDT). The final equations are calculated by Hamilton's principle. Differential quadrature method (DQM) is utilized for presenting the instable fluid velocity. The influences of length to radius ratio of pipe, volume fraction, diameter and type of nanoparticles are shown on the instable fluid velocity. The outcomes are compared with other published articles where shows good accuracy. Numerical results indicate that with enhancing the volume fraction of nanoparticles, the instable fluid velocity is increased. In addition, the instable fluid velocity of SiO2-water is higher than other types of nanoparticles assumed in this work. https://jcamech.ut.ac.ir/article_76984_65a00b41ce2eb548caadd9d57d96602e.pdf