Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.

Brownian particle deposition in a directly simulated turbulent channel flow

Abstract: Diffusion of submicron particles in a simulated turbulent channel flow field is studied. The turbulent flow velocity field is generated by a direct numerical integration of the Navier–Stokes equation with the pseudospectral method. The equation of motion of particles including the Brownian effects is used and ensembles of particle trajectories are numerically evaluated and statistically analyzed. A uniform initial concentration of particles is used in the analysis. Effects of size on particle dispersion and wall deposition processes are studied. The results are compared with the existing models for the submicron particle deposition rate.

Simulations of extensional flow in microrheometric devices

Abstract: We present a detailed numerical study of the flow of a Newtonian fluid through microrheometric devices featuring a sudden contraction–expansion. This flow configuration is typically used to generate extensional deformations and high strain rates. The excess pressure drop resulting from the converging and diverging flow is an important dynamic measure to quantify if the device is intended to be used as a microfluidic extensional rheometer. To explore this idea, we examine the effect of the contraction length, aspect ratio and Reynolds number on the flow kinematics and resulting pressure field. Analysis of the computed velocity and pressure fields show that, for typical experimental conditions used in microfluidic devices, the steady flow is highly three-dimensional with open spiraling vortical structures in the stagnant corner regions. The numerical simulations of the local kinematics and global pressure drop are in good agreement with experimental results. The device aspect ratio is shown to have a strong impact on the flow and consequently on the excess pressure drop, which is quantified in terms of the dimensionless Couette and Bagley correction factors. We suggest an approach for calculating the Bagley correction which may be especially appropriate for planar microchannels.

Entropy Generation Minimization of Fully Developed Internal Flow With Constant Heat Flux

Abstract: We use the entropy generation minimization (EGM) method to optimize a single-phase, convective, fully developed flow with uniform and constant heat flux. For fixed mass flow rate and fixed total heat transfer rate, and the assumption of uniform and constant heat flux, an optimal Reynolds number for laminar and turbulent flow is obtained. The study also compares optimal Reynolds number and minimum entropy generation for cross sections: square, equilateral triangle and rectangle with aspect ratios of two and eight. The rectangle with aspect ratio of eight had the smallest optimal Reynolds number the smallest entropy generation number, and the smallest flow length

The role of activation energy and reduced viscosity on the enhancement of water flow through carbon nanotubes

Abstract: Molecular dynamics simulations are carried out to study the pressure driven fluid flow of water through single walled carbon nanotubes. A method for the calculation of viscosity of the confined fluid based on the Eyring theory of reaction rates is proposed. The method involves the calculation of the activation energy directly from the molecular dynamics trajectory information. Computations are performed using this method to study the effect of surface curvature on the confined fluid viscosity. The results indicate that the viscosity varies nonlinearly with the carbon nanotube diameter. It is concluded that the reason behind the observed enhancement in the rate of fluid flow through carbon nanotubes could be the nonlinear variation of viscosity.