<b><i>Background:</i></b> Cerebral aneurysms carry a high risk of rupture and so present major threat to the patient’s life. Accurate criteria for predicting aneurysm are important therapeutic decision-making, some clinical morphological factors may help predict unruptured aneurysms, such as sex, size location. Hemodynamic forces considered be key in natural history cerebral but effect on is uncertain, whether low or wall shear stress (WSS) most critical promoting...

Preeclampsia (PE) is a pregnancy-induced hypertension with proteinuria that typically develops after 20 weeks of gestation. A reduction in uterine blood flow causes placental ischemia and release anti-angiogenic factors such as sFlt-1 followed by PE. Although the reduced perfusion pressure (RUPP) model widely used rats, investigating role genes on PE using genetically engineered animals has been problematic because it difficult to make useful RUPP mice. To establish mice, we bilaterally...

A direct numerical simulation of a temporally developing mixing layer with passive scalar transport is performed for various Schmidt numbers (Sc = 0.25, 1, 4, and 8). Turbulent investigated near the turbulent/non-turbulent interface (TNTI), which consisting turbulent sublayer (TSL) viscous superlayer (VSL). The irrotational boundary, close to outer edge TNTI layer, detected as isosurface small vorticity magnitude. movement fluid elements relative boundary analyzed. Once non-turbulent...

Experimental and numerical studies are conducted on the aerodynamic characteristics of a flapping wing an insect in forward flight. Unsteady forces flow patterns measured using dynamically scaled mechanical model water tunnel. The design is based bumblebee. also computed three-dimensional Navier-Stokes code. Comparisons between experimental results show good agreement time histories both hovering Aerodynamic mechanisms flight, such as delayed stall, rotational effect, wake capture examined...

The enstrophy (ω2/2) and passive scalar (ϕ) transport near the turbulent/non-turbulent (T/NT) interface is investigated using direct numerical simulation of a planar jet with transport. To take into account movement, we derive equations for in local coordinate system moving T/NT interface. characteristics are analyzed three orientations. cross-streamwise edge leading face streamwise directions, respectively, trailing opposite to edge. propagation velocity derived from equation system....

Abstract Vortex stretching and compression, which cause enstrophy production by inviscid processes, are investigated near the turbulent/non-turbulent (T/NT) interface in a planar jet using direct numerical simulation (DNS). The is analysing relationship among vorticity vector, strain-rate eigenvectors eigenvalues. statistics calculated individually for three different orientations. T/NT oriented tangential direction to interface. affected orientation because intensity of vortex depends on...

Direct numerical simulations were carried out to study the turbulence generated by a fractal square grid at Reynolds number of \documentclass[12pt]{minimal}\begin{document}$Re_{L_0}$\end{document}ReL0 = 20000 (based on inlet velocity Uin and length largest bar L0). We found that in near-field region, can generate much higher levels has better mixing performance than single grid. However, current results show produce intensity turbulent end simulation region (i.e., X/L0 ≃ 13) comparable those...

A numerical study has been performed for the flow and heat transfer in space between a pair of coaxial cylinders with outer one fixed inner rotating. Of special interest is case where either an axially grooved surface resulting twelve circumferentially periodic cavities embedded it. The ends cylinder are bounded by flat impermeable walls that to or rotate one. Such geometry common electric motors improved understanding thermophysical phenomena essential analysis design. Discretized transport...

In vitro blood vessel biomodeling with realistic mechanical properties and geometrical structures is helpful for training in surgical procedures, especial those used endovascular treatment. Poly (vinyl alcohol) hydrogel (PVA-H), which made of (PVA) water, may be useful as a material due to its low surface friction resistance good transparency. order simulate the vessels, measurements PVA-H were carried out dynamic analyzer, storage modulus (G') loss (G") obtained. PVA-Hs prepared by...

Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, located downstream channel entrance, and it numerically constructed staggered mesh arrangement using immersed boundary method. The grid types are: (a) square-mesh biplane (b) single-plane (c) composite consisting parallel square-bars (d) fractal grid. Two fluids with different...

We simulate fractal-generated turbulence (Hurst and Vassilicos 2007 Phys. Fluids 19 035103)) by means of a direct numerical simulation address its fundamental characteristics. examine whether the in upstream region has nature similar to that wake. propose an equation for predicting peak values velocity fluctuation intensity devise method formulating functional form quantity interest focusing on time scale decaying turbulence, we those forms turbulent kinetic energy rms pressure through this...

SUMMARY We attempt to improve accuracy in the high‐wavenumber region DNS of incompressible wall turbulence such as found fully developed turbulent channel flow. In particular, it is shown that improvement viscous terms Navier–Stokes equations leads higher‐order statistics and various spectra. It emphasized increase required computational cost will not be crucial when flow simulated, because introduction a scheme into does for solving Poisson equation. introduced fourth‐order eighth‐order...

In this paper, direct numerical simulations are carried out to study single-square grid-generated turbulence at a Reynolds number \documentclass[12pt]{minimal}\begin{document}$Re_{L_0}$\end{document}ReL0 = 20 000 (based on the inlet velocity Uin and length of grid bar L0). Different from regular multiscale/fractal grid, here only single large square is placed center near inlet. First, we investigate evolutions characteristics (e.g., mean streamwise velocity, intensity, Taylor microscale,...

Lagrangian statistics obtained from direct numerical simulations of turbulent planar jets and mixing layers are reported for the separation distance between tracer particles at outer edge turbulent/non-turbulent interface layer, entrained fluid particles. In viscous superlayer (VSL) mean square particle exhibits a ballistic evolution, while Richardson-like scaling relative dispersion prevails inside sublayer (TSL). The results further support existence two different regimes within where...

Obtaining real flow information is important in various fields, but a difficult issue because measurement data are usually limited time and space, computational results do not represent the exact state of flows. Problems inherent realization numerical simulation real-world flows include difficulty representing initial boundary conditions unstable characteristics. This article reviews studies dealing with these problems. First, an overview basic methodologies interpolation/approximation...

This paper deals with a state estimator or simply an observer of flow field. The observer, being fundamental concept in the control system theory, also has potential analysis related problems as integrated computational method aid experiment. In framework physical is estimated from mathematical model feedback on-line experimental measurement. A SIMPLER based simulation algorithm used real and partial measurement fed back to boundary condition through controller. existence feedback-loop...

Turbulent mixing in regular and fractal grid turbulence is investigated this work by using direct numerical simulation (DNS). Two types of turbulence-generating grids are used: a biplane square (regular grid) grid. The thickness ratios tr the set at 5.0 8.5. solidity maintained σ=0.36 for all grids. mesh Reynolds number, ReM=U0Meff/ν, 2500 cases, where U0 cross-sectionally averaged mean velocity; Meff, effective size; ν, kinematic viscosity. numerically generated immersed boundary method...

Acoustic liposomes (AL) have their inherent echogenicity and can add functionality in serving as drug carriers with tissue specificity. Nonuniform vascular structures branches/bends are evaluated by imaging the intravascular movement locus of ALs high-frequency ultrasound (HF-US) imaging. However, evaluation antitumor effects on angiogenesis HF-US has not been reported. Here, we show that combination an system is capable noninvasively evaluating volumetric angiogenic preclinical mouse models...

In this study, we performed a direct numerical simulation (DNS) of spatially developing shear mixing layer covering both and developed regions. The aim study is to clarify the driving mechanism vortical structure partial counter-gradient momentum transport (CGMT) appearing in quasi self-similar region. present DNS, self-similarity confirmed x/L ≥ 0.67 (x/δU0 137), where L δU0 are vertical length computational domain initial thickness, respectively. However, trend CGMT observed at around kδU...

A modern technique for the treatment of cerebral aneurysms involves insertion a flow diverter stent. Flow stagnation, produced by fine mesh structure diverter, is thought to promote blood clotting in an aneurysm. However, apart from its effect on reduction, metal device poses risk occlusion parent artery. One strategy avoiding arterial use with higher porosity. To aid development optimal stents view point reduction maintaining high porosity, we used lattice Boltzmann simulations and...

This paper deals with a new flow analysis system, namely the hybrid wind tunnel, which integrates experimental measurement tunnel and corresponding numerical simulation computer. Analysis here is performed for fundamental Karman vortex street in wake of square cylinder. A specific feature existence feedback signal to compensate error pressure on side walls cylinder feed-forward adjust upstream velocity boundary condition. Investigation focused evaluating as methodology respect ordinary...