Velocity transformation for compressible wall-bounded turbulent flows with and without heat transfer.

In this work, a transformation, which maps the mean velocity profiles of compressible wall-bounded turbulent flows to the incompressible law of the wall, is proposed. Unlike existing approaches, the proposed transformation successfully collapses, without specific tuning, numerical simulation data from fully developed channel and pipe flows, and boundary layers with or without heat transfer. In all these cases, the transformation is successful across the entire inner layer of the boundary layer (including the viscous sublayer, buffer layer, and logarithmic layer), recovers the asymptotically exact near-wall behavior in the viscous sublayer, and is consistent with the near balance of turbulence production and dissipation in the logarithmic region of the boundary layer.

Dynamic slip wall model for large-eddy simulation.

Wall modelling in large-eddy simulation (LES) is necessary to overcome the prohibitive near-wall resolution requirements in high-Reynolds-number turbulent flows. Most existing wall models rely on assumptions about the state of the boundary layer and require prescription of tunable coefficients. They also impose the predicted wall stress by replacing the no-slip boundary condition at the wall with a Neumann boundary condition in the wall-parallel directions while maintaining the no-transpiration condition in the wall-normal direction.

Shoulder measurements on MRI: Statistical analysis of patients without and with rotator cuff tears and predictive modeling.

This study aims to determine significant differences between various measurements of shoulder structures and relationships in patients with and without rotator cuff tears and identify a subset of these measurements that may merit further investigation. Shoulder MRIs of 120 patients with rotator cuff tears (RCT group) and 80 patients with normal examinations (No RCT group) were retrospectively identified. Numerous measurements of shoulder anatomy and relationships and pathology characterization were performed for each study.

Using parabolized stability equations to model boundary-layer transition in direct and large-eddy simulations.

We examine the potential of the nonlinear parabolized stability equations (PSE) to provide an accurate yet computationally efficient treatment of the growth of disturbances in H-type transition to turbulence. The PSE capture the nonlinear interactions that eventually induce breakdown to turbulence, and can as such identify the onset of transition without relying on empirical correlations. Since the local PSE solution at the onset of transition is a close approximation of the Navier-Stokes equations, it provides a natural inflow condition for direct numerical simulations (DNS) and large-eddy simulations (LES) by avoiding nonphysical transients.

Modeling boundary-layer transition in direct and large-eddy simulations using parabolized stability equations.

We examine the potential of the nonlinear parabolized stability equations (PSE) to provide an accurate yet computationally efficient treatment of the growth of disturbances in H-type transition to turbulence. The PSE capture the nonlinear interactions that eventually induce breakdown to turbulence and can as such identify the onset of transition without relying on empirical correlations. Since the local PSE solution at the onset of transition is a close approximation of the Navier-Stokes equations, it provides a natural inflow condition for direct numerical simulations (DNS) and large-eddy simulations (LES) by avoiding nonphysical transients.

Turbulence intensities in large-eddy simulation of wall-bounded flows.

A persistent problem in wall-bounded large-eddy simulations (LES) with Dirichlet no-slip boundary conditions is that the near-wall streamwise velocity fluctuations are overpredicted, while those in the wall-normal and spanwise directions are underpredicted. The problem may become particularly pronounced when the near-wall region is underresolved. The prediction of the fluctuations is known to improve for wall-modeled LES, where the no-slip boundary condition at the wall is typically replaced by Neumann and no-transpiration conditions for the wall-parallel and wall-normal velocities, respectively.

Large-Eddy Simulation of Thermally Stratified Atmospheric Boundary-Layer Flow Using a Minimum Dissipation Model.

A generalized form of a recently developed minimum dissipation model for subfilter turbulent fluxes is proposed and implemented in the simulation of thermally stratified atmospheric boundary-layer flows. Compared with the original model, the generalized model includes the contribution of buoyant forces, in addition to shear, to the production or suppression of turbulence, with a number of desirable practical and theoretical properties. Specifically, the model has a low computational complexity, appropriately switches off in laminar and transitional flows, does not require any ad hoc shear and stability corrections, and is consistent with theoretical subfilter turbulent fluxes.

Log-layer mismatch and modeling of the fluctuating wall stress in wall-modeled large-eddy simulations.

Log-layer mismatch refers to a chronic problem found in wall-modeled large-eddy simulation (WMLES) or detached-eddy simulation, where the modeled wall-shear stress deviates from the true one by approximately 15%. Many efforts have been made to resolve this mismatch. The often-usedfixes, which are generally , include modifying subgridscale stress models, adding a stochastic forcing, and moving the LES-wall-model matching location away from the wall.

Transitional-turbulent spots and turbulent-turbulent spots in boundary layers.

Two observations drawn from a thoroughly validated direct numerical simulation of the canonical spatially developing, zero-pressure gradient, smooth, flat-plate boundary layer are presented here. The first is that, for bypass transition in the narrow sense defined herein, we found that the transitional-turbulent spot inception mechanism is analogous to the secondary instability of boundary-layer natural transition, namely a spanwise vortex filament becomes a [Formula: see text] vortex and then, a hairpin packet. Long streak meandering does occur but usually when a streak is infected by a nearby existing transitional-turbulent spot.

Space-time characteristics of wall-pressure and wall shear-stress fluctuations in wall-modeled large eddy simulation.

We report the space-time characteristics of the wall-pressure fluctuations and wall shear-stress fluctuations from wall-modeled large eddy simulation (WMLES) of a turbulent channel flow at Re = 2000. Two standard zonal wall models (equilibrium stress model and nonequilibrium model based on unsteady RANS) are employed, and it is shown that they yield similar results in predicting these quantities. The wall-pressure and wall shear-stress fields from WMLES are analyzed in terms of their r.

Osborne Reynolds pipe flow: Direct simulation from laminar through gradual transition to fully developed turbulence.

The precise dynamics of breakdown in pipe transition is a century-old unresolved problem in fluid mechanics. We demonstrate that the abruptness and mysteriousness attributed to the Osborne Reynolds pipe transition can be partially resolved with a spatially developing direct simulation that carries weakly but finitely perturbed laminar inflow through gradual rather than abrupt transition arriving at the fully developed turbulent state. Our results with this approach show during transition the energy norms of such inlet perturbations grow exponentially rather than algebraically with axial distance.

The effects of vitamin E and omega-3 PUFAs on endothelial function among adolescents with metabolic syndrome.

Aim: The present study aims to explore the effects of vitamin E and omega-3 on endothelial function indicators among adolescents with metabolic syndrome.

Method: In a randomized, double blind, and placebo-controlled trial, 90 young individuals, aged 10 to 18 years, with metabolic syndrome were randomly assigned to receive either vitamin E tablets (400 IU/day) or omega-3 tablets (2.4 gr/day) or placebo.

First National Report on Aminotransaminases' Percentiles in Children of the Middle East and North Africa (MENA): the CASPIAN-III Study.

Background: By the current global obesogenic environment, non-alcoholic fatty liver disease is becoming an important health problem in the pediatric age group.

Objectives: This study aimed to determine the first age-and gender-specific percentiles and upper limit normal limit (ULN) of alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) among a nationally-representative sample of children and adolescents in the Middle East and North Africa (MENA). The second objective was to determine the linear association of obesity indexes and age with serum ALT and AST levels.

What the radiologist needs to know about urolithiasis: part 2--CT findings, reporting, and treatment.

Objective: This article reviews types of urinary calculi and their imaging appearances, presents direct and secondary imaging findings of urolithiasis, and provides an overview of treatment methods. Pertinent imaging findings that affect clinical management are highlighted. The implications of complex or variant genitourinary anatomy are reviewed.

What the radiologist needs to know about urolithiasis: part 1--pathogenesis, types, assessment, and variant anatomy.

Objective: This article reviews types of urinary calculi and their imaging appearances, presents direct and secondary imaging findings of urolithiasis, and provides an overview of treatment methods. Pertinent imaging findings that impact clinical management are highlighted. The implications of complex or variant genitourinary anatomy are reviewed.

An observer study for a computer-aided reading protocol (CARP) in the screening environment for digital mammography.

Rationale And Objectives: The aims of this study were to investigate improving work flow efficiency by shortening the reading time of digital mammograms using a computer-aided reading protocol (CARP) in the screening environment and to increase detection sensitivity using CARP, compared to the current protocol, commonly referred to as the quadrant view (QV).

Materials And Methods: A total of 200 cases were selected for a receiver-operating characteristic (ROC) study to evaluate two image display work flows, CARP and QV, in the screening environment. A Web-based tool was developed for scoring, reporting, and statistical analysis.

Converting three general-cognitive function scales into persian and assessment of their validity and reliability.

Objectives: Glasgow Outcome Scale Extended (GOSE), Galveston Amnesia and orientation Test (GOAT) and Disability Rating Scale (DRS) are three popular outcome measure tools used principally in traumatic brain injury (TBI) patients. We conducted this study to provide a Farsi version of these outcome scales for use in Iran.

Methods: Following a comprehensive literature review, Farsi transcripts were prepared by "forward-backward" translation and reviewed by subject experts.

Statistical description of the free-space propagation of highly aberrated optical beams.

The free-space propagation of initially aberrated optical beams is considered with an emphasis on aero-optical applications. An exact statistical solution of the paraxial wave equation is derived that can be used to obtain statistics of the beam such as beam center, spread, and higher-order statistics as algebraic functions of propagation distance, wavelength, and statistics of the initial wavefront. Correlations between the proposed description and intensity-based statistics, such as the Strehl ratio, are investigated.