Three dimensionality in the wake of the flow around a circular cylinder at Reynolds number 5000

The turbulent flow around a circular cylinder has been investigated at Re=5000Re=5000 using direct numerical simulations. Low frequency behavior, vortex undulation, vortex splitting, vortex dislocations and three dimensional flow within the wake were found to happen at this flow regime. In order to successfully capture the wake three dimensionality, different span-wise lengths were considered. It was found that a length LZ=2pDLZ=2pD was enough to capture this behavior, correctly predicting different aspects of the flow such as drag coefficient, Strouhal number and pressure and velocity distributions when compared to experimental values. Two instability mechanisms were found to coexist in the present case study: a global type instability originating in the shear layer, which shows a characteristic frequency, and a convective type instability that seems to be constantly present in the near wake. Characteristics of both types of instabilities are identified and discussed in detail. As suggested by Norberg, a resonance-type effect takes place in the vortex formation region, as the coexistence of both instability mechanisms result in distorted vortex tubes. However, vortex coherence is never lost within the wake.Peer ReviewedPostprint (author's final draft

Direct numerical simulation of the flow around an aerofoil in ramp-up motion

A detailed analysis of the flow around a NACA0020 aerofoil at Rec = 2 × 104 undergoing a ramp up motion has been carried out by means of direct numerical simulations. During the manoeuvre, the angle of attack is linearly varied in time between 0° and 20° with a constant rate of change of αrad = 0.12 U∞/c. When the angle of incidence has reached the final value, the lift experiences a first overshoot and then suddenly decreases towards the static stall asymptotic value. The transient instantaneous flow is dominated by the generation and detachment of the dynamic stall vortex, a large scale structure formed by the merging of smaller scales vortices generated by an instability originating at the trailing edge. New insights on the vorticity dynamics leading to the lift overshoot, lift crisis, and the damped oscillatory cycle that gradually matches the steady condition are discussed using a number of post-processing techniques. These include a detailed analysis of the flow ensemble average statistics and coherent structures identification carried out using the Q-criterion and the finite-time Lyapunov exponent technique. The results are compared with the one obtained in a companion simulation considering a static stall condition at the final angle of incidence α = 20°

Flow and turbulent structures around simplified car models

External car aerodynamics study has great importance in overall car efficiency and ride stability, being a key element in successful automotive design. The flow over car geometries shows three dimensional and unsteady turbulent characteristics. Additionally, vortex shedding, flow reattachment and recirculation bubbles are also found around the bluff body. These phenomena greatly influence the lift and drag coefficients, which are fundamental for ride stability and energy efficiency, respectively. The aim of the present study is focused on the assessment of different LES models (e.g. VMS or SIGMA models), as well as to show their capabilities of capturing the large scale turbulent flow structures in car-like bodies using relative coarse grids. In order to achieve these objectives, the flow around two model car geometries, the Ahmed and the Asmo cars, is simulated. These generic bluff bodies reproduce the basic fluid dynamics features of real cars. First, the flow over both geometries is studied and compared against experimental results to validate the numerical results. Then, different LES models are used to study the flow in detail and compare the structures found in both geometries.Peer ReviewedPreprin

Emotional abuse interacts with borderline personality in adolescent inpatients with binge-purging eating disorders

Purpose Childhood abuse is associated with an increased risk of developing eating disorders (EDs) as well as personality disorders (PDs). However, their interaction is still uncertain, particularly in adolescents. This study investigates the correlations between childhood emotional neglect (CEN), childhood emotional abuse (CEA), and obsessive-compulsive and borderline personality styles in female adolescent inpatients with eating disorders (EDs). Methods One hundred and twenty-eight inpatients (ages 14-18) were assessed, 54 were diagnosed with restricting-type anorexia nervosa (AN-R) and 33 with a binge-purging ED [BP-ED; comprising patients with binge-purging type anorexia nervosa (AN-BP), n = 15, and bulimia nervosa (BN), n = 18]. Fifty healthy participants made up the control group (CG). CEN and CEA were assessed with the Childhood Trauma Questionnaire, while the Personality Style and Disorder Inventory was implemented to determine personality styles. Results A MANOVA revealed a significant main effect of CEA on spontaneous-borderline personality style [F(8,119) = 17.1, p < 0.001, η2 = 0.126], as well as a main effect of ED group on spontaneous-borderline [F(2,119) = 3.1, p = 0.048, η2 = 0.050]. A significant interaction between ED group, CEA, and spontaneous-borderline was found [F(2,119) = 3.5, p = 0.034, η2 = 0.055] with BP-ED showing significantly higher scores in CEA (9.3 ± 4.0) and in spontaneous-borderline (14.2 ± 6.2). Conclusions Considering CEA and borderline personality style in adolescent inpatients with BN or AN-BP may help improve the understanding of the etiology and maintenance of BP-ED and provide more effective treatment targets. Level of evidence Level III, case–control analytic study

LES-based Study of the Roughness Effects on the Wake of a Circular Cylinder from Subcritical to Transcritical Reynolds Numbers

This paper investigates the effects of surface roughness on the flow past a circular cylinder at subcritical to transcritical Reynolds numbers. Large eddy simulations of the flow for sand grain roughness of size k/D = 0.02 are performed (D is the cylinder diameter). Results show that surface roughness triggers the transition to turbulence in the boundary layer at all Reynolds numbers, thus leading to an early separation caused by the increased momentum deficit, especially at transcritical Reynolds numbers. Even at subcritical Reynolds numbers, boundary layer instabilities are triggered in the roughness sublayer and eventually lead to the transition to turbulence. The early separation at transcritical Reynolds numbers leads to a wake topology similar to that of the subcritical regime, resulting in an increased drag coefficient and lower Strouhal number. Turbulent statistics in the wake are also affected by roughness; the Reynolds stresses are larger due to the increased turbulent kinetic energy production in the boundary layer and separated shear layers close to the cylinder shoulders.We acknowledge “Red Española de Surpercomputación” (RES) for awarding us access to the MareNostrum III machine based in Barcelona, Spain (Ref. FI-2015-2-0026 and FI-2015-3-0011). We also acknowledge PRACE for awarding us access to Fermi and Marconi Supercomputers at Cineca, Italy (Ref. 2015133120). Oriol Lehmkuhl acknowledges a PDJ 2014 Grant by AGAUR (Generalitat de Catalunya). Ugo Piomelli acknowledges the support of the Natural Sciences and Engineering Research Council (NSERC) of Canada under the Discovery Grant Programme (Grant No. RGPIN-2016-04391). Ricard Borrell acknowledges a Juan de la Cierva postdoctoral grant (IJCI-2014-21034). Ivette Rodriguez, Oriol Lehmkuhl, Ricard Borrell and Assensi Oliva acknowledge Ministerio de Economía y Competitividad, Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain (ref. ENE2014-60577-R).Peer ReviewedPostprint (author's final draft

Influence of rotation on the flow over cylinder at RE=5000

Peer ReviewedPreprin

Emotional abuse interacts with borderline personality in adolescent inpatients with binge-purging eating disorders

Purpose: Childhood abuse is associated with an increased risk of developing eating disorders (EDs) as well as personality disorders (PDs). However, their interaction is still uncertain, particularly in adolescents. This study investigates the correlations between childhood emotional neglect (CEN), childhood emotional abuse (CEA), and obsessive-compulsive and borderline personality styles in female adolescent inpatients with eating disorders (EDs). Methods: One hundred and twenty-eight inpatients (ages 14-18) were assessed, 54 were diagnosed with restricting-type anorexia nervosa (AN-R) and 33 with a binge-purging ED [BP-ED; comprising patients with binge-purging type anorexia nervosa (AN-BP), n = 15, and bulimia nervosa (BN), n = 18]. Fifty healthy participants made up the control group (CG). CEN and CEA were assessed with the Childhood Trauma Questionnaire, while the Personality Style and Disorder Inventory was implemented to determine personality styles. Results: A MANOVA revealed a significant main effect of CEA on spontaneous-borderline personality style [F(8,119) = 17.1, p < 0.001, eta(2) = 0.126], as well as a main effect of ED group on spontaneous-borderline [F(2,119) = 3.1, p = 0.048, eta(2) = 0.050]. A significant interaction between ED group, CEA, and spontaneous-borderline was found [F(2,119) = 3.5, p = 0.034, eta(2) = 0.055] with BP-ED showing significantly higher scores in CEA (9.3 +/- 4.0) and in spontaneous-borderline (14.2 +/- 6.2). Conclusions: Considering CEA and borderline personality style in adolescent inpatients with BN or AN-BP may help improve the understanding of the etiology and maintenance of BP-ED and provide more effective treatment targets

Neonatal Ovine Pulmonary Dendritic Cells Support Bovine Respiratory Syncytial Virus Replication with Enhanced Interleukin (IL)-4 And IL-10 Gene Transcripts

The lung microenvironment is constantly exposed to microorganisms and particulate matter. Lung dendritic cells (DCs) play a crucial role in the uptake and processing of antigens found within the respiratory tract. Respiratory syncytial virus (RSV) is a common respiratory tract pathogen in children that induces an influx of DCs to the mucosal surfaces of the lung. Using a neonatal lamb model, we examined the in vivo permissiveness of DCs to RSV infection, as well as overall cell surface changes and cytokine responses of isolated lung DCs after bovine RSV (BRSV) infection. We report that isolated lung DCs and alveolar macrophages support BRSV replication. Isolated lung DCs were determined to be susceptible to BRSV infection as demonstrated by quantification of BRSV non-structural protein 2 mRNA. BRSV infection induced an initial upregulation of CD14 expression on lung DCs, but by 5 d postinfection expression was similar to that on control cells. No significant changes in CD80/86 or MHC class I expression were seen on lung DCs after BRSV infection. Low to moderate expression of MHC class II and DEC-205 was detected by day 5 postinfection. Initially, on day 3 postinfection, lung DCs from BRSV-infected lambs had decreased endocytosis of fluorescein isothiocyanate (FITC)–ovalbumin (OVA). The amount of FITC–OVA endocytosed by lung DCs isolated on day 5 postinfection was similar to that of controls. The most interesting observation was the induction of immunomodulatory interleukin (IL)-4 and IL-10 cytokine gene transcription in lung DCs and alveolar macrophages after in vivo infection with BRSV. Overall, these findings are the first to demonstrate that neonatal lung DCs support in vivo BRSV replication and produce type II cytokines after viral infection