Detailed information about the flow field pattern is highly important in accurately predicting particle deposition sites in the human airway. Flow in the upper airway during heavy breathing can have a Reynolds number as high as 9300, and therefore presents turbulent features. Although turbulence is believed to have an important effect on the airflow and other transport processes in the bronchia...

Title of dissertation: DIRECT NUMERICAL SIMULATIONS OF TRANSITIONAL PULSATILE FLOWS IN STENOTIC VESSELS Nikolaos Beratlis Doctor of Philosophy, 2008 Dissertation directed by: Professor Elias Balaras Department of Mechanical Engineering In the present work a numerical study of transitional pulsatile flow through planar and cylindrical constrictions is presented. First, a simulation carefully coo...

We examine the characteristics of helical flow in a concentric annulus with radii ratios of 0.52 and 0.9, whose outer cylinder is stationary and inner cylinder is rotating. Pressure losses and skin friction coefficients are measured for fully developed flows of water and a 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), when the inner cylinder rotates at the speed of 0~62.82 rad/...

To evaluate a lattice Boltzmann method (LBM) for the three dimensional continuum to non-continuum transitional flow regimes, the results are compared with those of the molecular dynamics (MD) simulations by the Leonard-Jones potential. The flow field considered is in a modeled nanoporous medium whose porosity is 0.88 and consists of square cylinder rods. The equations used in the LBM are modifi...

In this paper we carry out computational studies of three-dimensional flow over flapping wings. The problems we have investigated include, firstly, three-dimensonal simulation of flow over an extruded SD7003 airfoil in plunging motion at transitional Reynolds number and, secondly, flow over a pair of flapping rectangle wings with constant NACA0012 cross-sectional airfoil profile at low Reynolds...

In this study, the effects of thermal and hydraulic characteristics of wavy fin and tube heat exchanger are investigated. Simulation has been carried out by a commercial computational fluid dynamics code, ANSYS CFX12.0. The main objective of this study is to investigate the flow characteristics in turbulent flow. Results are predicted for the turbulent flow regime (2100≤Re≤7000) and compared wi...

The transitional boundary layer flow over a flat plate is investigated. The boundary layer flow is known to develop unstable Tollmien-Schlichting waves above a critical value of the Reynolds number. However, it is also known that this transition can be observed for sub-critical Reynolds numbers. In that case the basin of attraction of the laminar state coexists with the sustained turbulence. In...

In the present work we follow the breakdown of pairs of counter-rotating vortices (CVP) and the consequence formation of packets of hairpins in uniform shear flows. We employ a recent developed method which is capable of following (numerically) the evolution of finite-amplitude localized vortical disturbances embedded in shear flows. The solution is carried out using Lagrangian variables in Fou...

Brown, R., and Pickering, D. (1974). Archives of Disease in Childhood, 49, 883. Persistent transitional circulation. Six infants presented within 24 hours of birth with cyanosis. The clinical findings, combined with catheter studies in 4 cases, led to the conclusion that there was a persistent fetal direction of ductus arteriosus flow with pulmonary hypertension, i.e. a 'persistent transitional...

Unsteady wake-blade interaction is an inevitable consequence of the relative motion between rotors and stators in turbomachines. The flow in a low-pressure stage has a relatively low Reynolds number, of order 10 5 , based on chord length, and a substantial proportion of the boundary layer on the blade surface is thus laminar or transitional. While the flow in a turbine accelerates, globally, th...