Large-Eddy Simulation of Microvortex Generators in a Turbulent Boundary Layer

The present study investigates the flow physics on MicroVortex Generators (MVGs) in order to improve their performance in turbulent boundary layers (TBLs). TBLs can be a challenging environment for MVGs because of the streamwise length of the shedded vortex and its increased parasitic drag. Large-Eddy Simulation (LES) is used to properly resolve the turbulent boundary layer of a flat-plate with a zero-pressure gradient and MVG vane. Three different vane-types are investigated (e423-Mod, triangular, and rectangular vanes) in a single vane configuration. Important flow features such as a separation bubble on the leading edge of the rectangular vanes which introduced unsteadiness into the vortex formation and degraded the MVG's efficiency was observed. The e423-Mod and triangular vanes was observed to be more aerodynamically efficient. The triangular vane was found to be the most efficient when evaluated immediately downstream of the vane. However, the vortex from the triangular vane decayed very rapidly due to it being formed very close to the wall which degraded its efficiency further downstream. The e423-Mod vane avoided this problem but its drag was very high relative to the strength of the generated vortex and its vortex experienced a brief period of rapid decay immediately downstream decreasing its efficiency. Further downstream, the vortex of the rectangular vane at 16° became the most efficient through a combination of low vane drag and low vortex decay in the TBL, demonstrating the need to consider a range of issues when designing an MVG

Pressure Wave in Liquid Generated by Pneumatic Pistons and Its Interaction with a Free Surface

Numerical analysis of a pressure wave generated in a liquid [Formula: see text] upon impact of the pneumatic pistons and its interaction with a free surface has been performed for the geometry and parameters of the plasma compression system prototype constructed by General Fusion Inc. Stress wave developing in the hammer–anvil piston assembly is first simulated using high-fidelity structural mechanics research code, then propagated through the liquid [Formula: see text] with several solvers within OpenFOAM[Formula: see text] software and also with nonlinear acoustics in-house code based on the Westervelt equation. In the current system, a pressure wave transmitted into the liquid [Formula: see text] is characterized by a complex temporal double peak structure and strong spatial amplitude variation. An imprint of discrete pulses remains detectable during the entire propagation of the combined wave. An excellent agreement between the results produced with different numerical codes is obtained. Nonlinear effects associated with equation of state are found to be significant at impact velocities of [Formula: see text], while at lower velocities of [Formula: see text] the difference between the results obtained with linear and nonlinear equations of state is negligible. Liquid–gas interface dynamics during the compression process of a spherical gas cavity is captured very well by the compressibleInterFoam within OpenFOAM. </jats:p

Modulatory effect of fluoride and irradiation on rat molar rate of wear

The hypothesis was tested that fluoride (F-) modulates molar wear rate in the irradiated rat and that enamel solubility and dentin hardness are involved in this process. Seventy five 21 day-old rats were divided into 5 groups. Groups received either F-(25 ppm) in the drinking water or irradiation to the head (15 Gy in a single dose), or a combination of the two. The rate of occlusal wear was assessed by computerized planimetry.The amount of wear was significantly higher in the F- and irradiation monotreated rats, while under combined treatment it did nor differ significantly from the control values. Fluoridation or irradiation suppressed enamel solubility, as measured by calcium release in the etchant. Dentin microhardness, expressed in Vickers hardness number, was enhanced after either treatment, but remained unaffected when F- administration preceded irradiation. Enamel solubility and dentin microhardness did not correlate significantly with the rate of occlusal wear.L’hypothèse vérifiée dans cette recherche a été la modulation par le fluoré (F-) de l’usure des molaires du rat irradié et de l’éventuelle contribution de la solubilité de l’émail et de la dureté dentinaire dans ce processus. Soixante-dix rats âgés de 21 jours ont été divisés en 5 groupes. Les groupes ont reçu soit 25ppm F- dans l’eau de boisson, soit une dose unique d’irradiation (15 Gy) dans la sphère cranio-faciale, soit les deux traitements combinés. Le niveau d’usure occlusale des molaires a été déterminée par planimétrie computerisée.La quantité d’usure a été plus prononcée chez les animaux recevant uniquement du F- ou une irradiation tandis que les deux traitements combinés ont été suivis par des valeurs d’usure semblables a celles mesurées chez les témoins. La solubilité de l’émail, établie selon la quantité de calcium présente dans la solution corrosive et exprimée en mg/l Ca+ +, a été réduite par chacun des deux traitements. La dureté de la dentine, exprimée en unités Vickers, a été amplifiée par chaque traitement, restant toutefois inchangée uniquement chez les animaux recevant du F- avant l’irradiation. Les resultats de l’étude corrélative entre l’usure occlusale et la solubilité de l’émail ou la dureté dentinaire n’ont pas atteint des valeurs significatives

An investigation on the rheodynamics of human red blood cells using high performance computations

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Studies on the haemodynamics of human circulation are clinically and scientifically important. The flow of human blood is extremely complex due to the existence of the highly deformable red blood cells (RBCs), which are able to pass through capillaries smaller than their size. To investigate the effect of deformation and aggregation in blood flow, a computational technique has been developed by coupling the interaction between the fluid and the deformable solids. The flow of 49,512 RBCs at 45% concentration and under the influence of aggregating forces was examined to improve the existing knowledge on how to simulate and study the blood flow and its structural characteristics of blood at a large scale. The simulation was carried out with full parallelization of the coupled fluid-solid code using spatial decomposition and high performance supercomputers. The large scale feature of the simulation has enabled a macroscale verification and investigation of the overall characteristics of RBC aggregations to be carried out. The results are in excellent agreement with experimental studies and, more specifically, both the experimental and the simulation results show uniform RBC distributions under high shear rates (60-100/s) whereas large aggregations were observed under a lower shear rate of 10/s. The statistical analysis of the simulation data also shows that the shear rate has significant influence on both the flow velocity profiles and the frequency distribution of the RBC orientation angles. The flow under the low shear rate also tended to have bi-phasic velocity profile which is mainly due to the formation of large scale aggregation clusters

Direct numerical simulation of sediment entrainment in turbulent channel flow

This research was supported by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (Grant No. PIIF-GA-2009-236457). The first author acknowledges the financial support of the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 51021004), National Natural Science Foundation of China (Grant Nos. 50809047 and 51009105), and Natural Science Foundation of Tianjin (Grant No. 12JCQNJC02600)

Saltation of particles in turbulent channel flow.

This paper numerically investigates particle saltation in a turbulent channel flow having a rough bed consisting of two to three layers of densely packed spheres. The Shields function is 0.065 which is just above the sediment entrainment threshold to give a bed-load regime. The applied methodology is a combination of three technologies, i.e., the direct numerical simulation of turbulent flow; the combined finite-discrete element modeling of the deformation, movement, and collision of the particles; and the immersed boundary method for the fluid-solid interaction. It is shown that the presence of entrained particles significantly modifies the flow profiles of velocity, turbulent intensities, and shear stresses in the vicinity of a rough bed. The quasi-streamwise-aligned streaky structures are not observed in the near-wall region and the particles scatter on the rough bed owing to their large size. However, in the outer flow region, the turbulent coherent structures recover due to the weakening rough-bed effects and particle interferences. First- and second-order statistical features of particle translational and angular velocities, together with sediment concentration and volumetric flux density profiles, are presented. Several key parameters of the particle saltation trajectory are calculated and agree closely with published experimental data. Time histories of the hydrodynamic forces exerted upon a typical saltating particle, together with those of the particle's coordinates and velocities, are presented. A strong correlation is shown between the abruptly decreasing streamwise velocity and increasing vertical velocity at collision which indicates that the continuous saltation of large-grain-size particles is controlled by collision parameters such as particle incident angle, local bed packing arrangement, and particle density, etc.This work was supported by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (Grant No. PIIF-GA-2009-236457). The first author acknowledges the financial support of the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 51321065), National Natural Science Foundation of China (Grants No. 50809047, No. 51109157, and No. 51009105), and Natural Science Foundation of Tianjin (Grants No. 12JCQNJC02600, No. 12JCQNJC04900, and No. 12JCQNJC05600

Drosophila comes of age as a model system for understanding the function of cytoskeletal proteins in cells, tissues, and organisms

available in PMC 2016 June 30For the last 100 years, Drosophila melanogaster has been a powerhouse genetic system for understanding mechanisms of inheritance, development, and behavior in animals. In recent years, advances in imaging and genetic tools have led to Drosophila becoming one of the most effective systems for unlocking the subcellular functions of proteins (and particularly cytoskeletal proteins) in complex developmental settings. In this review, written for non-Drosophila experts, we will discuss critical technical advances that have enabled these cell biological insights, highlighting three examples of cytoskeletal discoveries that have arisen as a result: (1) regulation of Arp2/3 complex in myoblast fusion, (2) cooperation of the actin filament nucleators Spire and Cappuccino in establishment of oocyte polarity, and (3) coordination of supracellular myosin cables. These specific examples illustrate the unique power of Drosophila both to uncover new cytoskeletal structures and functions, and to place these discoveries in a broader in vivo context, providing insights that would have been impossible in a cell culture model or in vitro. Many of the cellular structures identified in Drosophila have clear counterparts in mammalian cells and tissues, and therefore elucidating cytoskeletal functions in Drosophila will be broadly applicable to other organisms.National Institutes of Health (U.S.) (NIH/NINDS (DP2 NS082127))Pew Scholars Program in the Biomedical SciencesNational Institutes of Health (U.S.) (NIH/NIGMS (R01-GM084947))American Cancer Society (Research Scholar Award

A novel mode of capping protein-regulation by Twinfilin

Cellular actin assembly is controlled at the barbed ends of actin filaments, where capping protein (CP) limits polymerization. Twinfilin is a conserved in vivo binding partner of CP, yet the significance of this interaction has remained a mystery. Here, we discover that the C-terminal tail of Twinfilin harbors a CP-interacting (CPI) motif, identifying it as a novel CPI-motif protein. Twinfilin and the CPI-motif protein CARMIL have overlapping binding sites on CP. Further, Twinfilin binds competitively with CARMIL to CP, protecting CP from barbed-end displacement by CARMIL. Twinfilin also accelerates dissociation of the CP inhibitor V-1, restoring CP to an active capping state. Knockdowns of Twinfilin and CP each cause similar defects in cell morphology, and elevated Twinfilin expression rescues defects caused by CARMIL hyperactivity. Together, these observations define Twinfilin as the first \u27pro-capping\u27 ligand of CP and lead us to propose important revisions to our understanding of the CP regulatory cycle

Measuring Cognitive Errors: Initial Development of the Cognitive Distortions Scale (CDS)

The ability to assess and correct biases in thinking is central to cognitive-behavioral therapy. Although measures of cognitive distortions exist, no measure comprehensively assesses the cognitive errors that are typically cited in the literature. The development and initial validation of the Cognitive Distortions Scale (CDS), a questionnaire that measures the tendency to make 10 cognitive distortions (e.g., mindreading, catastrophizing, all-or-nothing thinking) as they occur in interpersonal and achievement domains, is described. Across two studies, undergraduate students (n = 318) completed the CDS and other clinically relevant measures. The CDS and its two subscales appear to exhibit good psychometric properties; however, a factor analysis supported the use of a one-factor solution. Additional analyses suggested that some errors occur more frequently in some domains than others and that some errors may have more clinical significance than others. Notwithstanding issues inherent in measuring cognitive errors, and study limitations, the CDS appears to be a promising new measure of cognitive distortion, with good research and clinical potential