The unsteady viscous flow in the vicinity of an axisymmetric stagnation point of an infinite moving cylinder with time-dependent axial velocity is investigated. The impinging free stream is steady with a strain rate k. An exact solution of the Navier-Stokes equations is derived in this problem. A reduction of these equations is obtained by use of appropriate transformations. The general self-si...

We present an immersed boundary method based on volume penalization, with which pulsatile flow in a model cerebral aneurysm is simulated. The model aneurysm consists of a curved vessel merged with a spherical cavity. The dominant vortical structures arising in the time-dependent flow are discussed and the evolution of the maximal shear stress in the aneurysm is analyzed. We approximate flow pro...

A volume-penalizing immersed boundary method is presented that facilitates the computation of incompressible fluid flow in complex flow domains. We apply this method to simulate the flow in cerebral aneurysms, and focus on the accuracy with which the flow field and the corresponding shear stress field are computed. The method is applied to laminar, incompressible flow in curved cylindrical vess...

With the assumption that the bed shear stress fluctuates in a lognormal fashion, the probability density function (pdf) of the standardised bed shear stress is derived as a function of the relative shear stress intensity. The pdf is more skewed with larger relative intensities, but approaches a Gaussian function when the relative intensity is small. The computed pdf agrees well with the reporte...

The turbulent potential model is a RANS model that avoids modeling the Reynolds stress tensor. As a result it has the ability to obtain the physical accuracy of Reynolds stress transport equation models at a cost and complexity comparable to popular two equation models. The model’s ability to predict channel flow, free-shear layers, homogeneous shear flow, stagnation point flow, backward facing...

Numerical predictions of blood flow patterns and hemodynamic stresses in Abdominal Aortic Aneurysms (AAAs) are performed in a two-aneurysm, axisymmetric, rigid wall model using the spectral element method. Homogeneous, Newtonian blood flow is simulated under steady conditions for the range of Reynolds numbers 10 < or =Re < or =2265. Flow hemodynamics are quantified by calculating the distributi...

For H-type transition to turbulence in a flat-plate boundary layer, we identify dynamically important features resulting from direct numerical and large eddy simulations (DNS and LES, respectively). Even though LES coupled with a dynamic subgrid-scale model provides an accurate prediction of the transition location, it fails to predict initial overshoot and subsequent turbulent skin friction. D...

In this study the pressure-drop, mean and rms axial velocity data are measured using a differential pressure transducer and a laser Doppler anemometer for the flow of Newtonian and non-Newtonian fluids in a concentric annular pipe (radius ratio =0.5) at various Reynolds numbers encompassing the laminar, transitional and turbulent regimes. Three different fluids are utilized; a semi-rigid shear-...

A Galilean invariant weak-equilibrium hypothesis that is sensitive to streamline curvature is proposed. The hypothesis leads to an algebraic Reynolds stress model for curved ows that is fully explicit and self-consistent. The model is tested in curved homogeneous shear ow: the agreement is excellent with Reynolds stress closure model and adequate with available experimental data. This research ...

In this paper we report on (two-component) LDV experiments in a fully developed turbulent pipe flow with a drag-reducing polymer (partially hydrolyzed polyacrylamide) dissolved in water. The Reynolds number based on the mean velocity, the pipe diameter and the local viscosity at the wall is approximately 10000. We have used polymer solutions with three different concentrations which have been c...