A numerical investigation of the asymmetric wake mode of a squareback Ahmed body – effect of a base cavity

2017 ◽  
Vol 831 ◽  
pp. 675-697 ◽  
Author(s):  
J.-M. Lucas ◽  
O. Cadot ◽  
V. Herbert ◽  
S. Parpais ◽  
J. Délery
Keyword(s):  
Drag Reduction ◽  
Body Height ◽  
Power Spectra ◽  
Low Pressure ◽  
The Body ◽  
Frequency Resolution ◽  
Recirculation Region ◽  
Periodic Mode ◽  
Lateral Velocity ◽  
Base Cavity

Numerical simulations of the turbulent flow over the flat backed Ahmed model at Reynolds number $Re\simeq 4\times 10^{5}$ are conducted using a lattice Boltzmann solver to clarify the mean topology of the static symmetry-breaking mode of the wake. It is shown that the recirculation region is occupied by a skewed low pressure torus, whose part closest to the body is responsible for an extra low pressure imprint on the base. Shedding of one-sided vortex loops is also reported, indicating global quasi-periodic dynamics in conformity with the seminal work of Grandemange et al. (J. Fluid Mech., vol. 722, 2013, pp. 51–84). Despite the limited low frequency resolution of the simulation, power spectra of the lateral velocity fluctuations at different locations corroborate the presence of this quasi-periodic mode at a Strouhal number of $St=0.16\pm 0.03$. A shallow base cavity of $5\,\%$ of the body height reduces the drag coefficient by $3\,\%$ but keeps the recirculating torus and its interaction with the base mostly unchanged. The drag reduction lies in a global constant positive shift of the base pressure distribution. For a deep base cavity of $33\,\%$ of the body height, a drag reduction of $9.5\,\%$ is obtained. It is accompanied by a large elongation of the recirculation inside the cavity that considerably attenuates the low pressure sources therein together with a symmetrization of the low pressure torus. The global quasi-periodic mode is found to be inhibited by the cavity.

The effect of rear cavity modifications on the drag and flow field topology of a Square Back Ahmed Body

2021 ◽  
pp. 095440702199091
Author(s):  
Naveen Koppa Shivanna ◽  
Pritanshu Ranjan ◽  
Shibu Clement
Keyword(s):  
Drag Reduction ◽  
Reference Model ◽  
Lift Coefficient ◽  
Body Height ◽  
Power Spectra ◽  
The Body ◽  
Recirculation Region ◽  
Cavity Depth ◽  
The Mean ◽  
Ahmed Body

This work presents a numerical investigation of turbulent flow over a simplified vehicle model called the Square Back Ahmed Body (SBAB). The simulations are performed at Reynolds number 1 × 105 using the k − [Formula: see text] SSTSAS turbulence model. The numerical results for the standard reference model, that is, SBAB, have been validated against available experimental data and numerical simulations. The performance of a passive flow controller with four variants on the mean wake topology and the resultant drag reduction is evaluated. The four variants are; (i) straight cavity, (ii) straight cavity with rounded edges, (iii) C-shaped cavity, and (iv) tapered cavity. For a straight cavity with a depth equal to 33.33% of the body height, drag is lowered by 5.63%. With the same cavity depth, rounding the straight cavity edges reduces the drag by 10.67% owing to the streamlining and shortening of the recirculation region. For a C-shaped cavity, the amount of drag reduction increased slightly by 1% more than that off straight cavity with rounded edges, due to improvement in the base pressure distribution compared to that of the latter case. Tapering the cavity edges at an angle of 6° gave a significant drag reduction of 22.55% primarily due to a tremendous decrease in wake size. The drag reduction achieved in all the cases results from the modification in the mean wake topology induced by afterbody shape remodeling. The power spectra of the evolution of the lift coefficient over time reveal a noticeable decrement in the flow randomness with the inclusion of a cavity and its modifications, which interprets the mitigation of the chaotic nature in the wake. The cavity presence has also increased the vorticity spreading rate in the mixing layer and produced significant attenuation of Turbulent Kinetic Energy (TKE).

Numerical Investigation of a Square Back Vehicle Equipped With a Single Cavity and Multi-Cavity

2020 ◽  
Author(s):  
Naveen Koppa Shivanna ◽  
Pritanshu Ranjan ◽  
Shibu Clement
Keyword(s):  
Drag Reduction ◽  
Numerical Investigation ◽  
Bluff Body ◽  
Body Height ◽  
The Body ◽  
Vehicle Model ◽  
Cavity Depth ◽  
Passive Flow ◽  
The Mean ◽  
Single Cavity

Abstract This work aims to investigate the comparative effect of two passive flow controls in modifying the mean wake topology around a simplified square back vehicle model. The two passive flow controls are (i) Single cavity and (ii) Multi-cavity. A straight cavity with an optimum depth at the rear base of a vehicle is a well-known technique used to alter the mean wake topology and achieve drag reduction[1]. For two dimensional bluff bodies, a multi-cavity is known to deliver better drag reduction at shorter cavity depths in comparison to a single cavity[2]. With this viewpoint, a numerical investigation is carried out to examine the performance of a multi-cavity over a single cavity in drag reduction for a three-dimensional bluff body vehicle model. The numerical simulations are performed at Reynolds Number (Re) = 1 × 105 using the k-ω SSTSAS turbulence model in a Finite volume open-source code OpenFOAM. The investigations revealed, for any cavity depth, a single cavity always performed better than multi-cavity in reducing drag. However, at optimum cavity depth equal to 33% of the body height, the drag reduction magnitude was identical for both the flow controls. The plausible mechanisms responsible for their relative difference in performance will be explored by analyzing the base pressure distribution, wake mean topology, and the temporal behavior of the wake.

The use of Body Surface Index as a Better Clinical Health indicators Compare to Body Mass Index and Body Surface Area for Clinical Application

2018 ◽  
pp. 131-136
Author(s):  
Shirazu I. ◽  
Theophilus. A. Sackey ◽  
Elvis K. Tiburu ◽  
Mensah Y. B. ◽  
Forson A.
Keyword(s):  
Surface Area ◽  
Body Surface Area ◽  
Clinical Application ◽  
Body Surface ◽  
Body Height ◽  
Health Indicators ◽  
The Body ◽  
Body Parameters ◽  
The Relationship ◽  
Individual Body

The relationship between body height and body weight has been described by using various terms. Notable among them is the body mass index, body surface area, body shape index and body surface index. In clinical setting the first descriptive parameter is the BMI scale, which provides information about whether an individual body weight is proportionate to the body height. Since the development of BMI, two other body parameters have been developed in an attempt to determine the relationship between body height and weight. These are the body surface area (BSA) and body surface index (BSI). Generally, these body parameters are described as clinical health indicators that described how healthy an individual body response to the other internal organs. The aim of the study is to discuss the use of BSI as a better clinical health indicator for preclinical assessment of body-organ/tissue relationship. Hence organ health condition as against other body composition. In addition the study is `also to determine the best body parameter the best predict other parameters for clinical application. The model parameters are presented as; modeled height and weight; modelled BSI and BSA, BSI and BMI and modeled BSA and BMI. The models are presented as clinical application software for comfortable working process and designed as GUI and CAD for use in clinical application.

Physical fitness of people with moderate and considerable intellectual disabilities

Physiotherapy ◽  
2013 ◽  
Vol 21 (3) ◽  
Author(s):  
Marzena Ślężyńska ◽  
Grzegorz Mięsok ◽  
Kamila Mięsok
Keyword(s):  
Physical Activity ◽  
Intellectual Disability ◽  
Physical Fitness ◽  
Body Mass ◽  
Body Height ◽  
Abdominal Muscle ◽  
The Body ◽  
Intellectually Disabled ◽  
Fitness Tests ◽  
Abdominal Muscle Strength

AbstractIntroduction: The aim of the physical activity of the intellectually disabled is the strengthening of health, creating movement habits, promoting active recreation, and maintaining exercise capacity. Skillfully applied physical activity allows to mitigate the effects of pathology and create the compensations to enable the intellectually disabled people to live relatively independently. Physical activity and sport also increase their chances to integrate with their families, peers, and social environment.Materials and methods: The research targeted a group of 134 people with moderate or considerable intellectual disability (65 women and 69 men), aged 20-53 years, who participated in occupational therapy workshops in Jastrzębie Zdrój, Rybnik, and Żory. Physical fitness was assessed using the “Eurofit Special” test and balance tests. Measurements of body height and mass were also taken and then used to calculate the body mass index (BMI).Results: A salient somatic trait was the greater body mass relative to height among the persons with considerable disability, clearly illustrated by the BMI. This explained their greater heaviness in performing physical exercises. An even greater difference between participants with moderate and considerable intellectual disability was visible in physical fitness. Obviously, older persons did not achieve as good results in fitness tests as the younger ones, yet the participants were more differentiated by the level of disability than age. Most symptomatic differences to the disadvantage of the considerably disabled were observed in explosive strength, speed, abdominal muscle strength, and flexibility.Conclusions: Significant differences in fitness between the compared groups make it necessary to take into account the level of intellectual disability in the course of physical education and sport, at work, and in household duties.

Incipient Separation Near Corners

2018 ◽  
Author(s):  
Anatoly I. Ruban
Keyword(s):  
Corner Point ◽  
Analytic Form ◽  
The Body ◽  
Recirculation Region ◽  
Body Contour ◽  
Concave Corner ◽  
Attached Flow ◽  
Surface Deflection ◽  
Interaction Problem ◽  
Incipient Separation

Chapter 4 analyses the transition from an attached flow to a flow with local recirculation region near a corner point of a body contour. It considers both subsonic and supersonic flow regimes, and shows that the flow near a corner can be studied in the framework of the triple-deck theory. It assumes that the body surface deflection angle is small, and formulates the linearized viscous-inviscid interaction problem. Its solution is found in an analytic form. It also presents the results of the numerical solution of the full nonlinear problem. It shows how, and when, the separation region forms in the boundary layer. In conclusion, it suggests that in the subsonic flow past a concave corner, the solution is not unique.

scholarly journals Growth and development of children under 5 years of age with tetralogy of Fallot in a Chinese population

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xin Li ◽  
Jin Zhu ◽  
Jun An ◽  
Yuqing Wang ◽  
Yili Wu ◽  
...  
Keyword(s):  
Body Weight ◽  
Tetralogy Of Fallot ◽  
Growth Retardation ◽  
Growth And Development ◽  
Heart Defects ◽  
Body Height ◽  
Child Growth ◽  
The Body ◽  
Early Age ◽  
Local Conditions

AbstractCongenital Heart Defects (CHDs) are associated with different patterns of malnutrition and growth retardation, which may vary worldwide and need to be evaluated according to local conditions. Although tetralogy of Fallot (TOF) is one of the first described CHDs, the etiology outcomes in growth and development of TOF in early age child is still unclear in most cases. This study was designed to investigate the growth retardation status of Chinese pediatric TOF patients under 5 years old. The body height, body weight and body mass index (BMI) of 262 pediatric patients (138 boys and 124 girls) who underwent corrective surgery for TOF between 2014 and 2018 were measured using conventional methods. The average body height, body weight and BMI of the patients were significantly lower than WHO Child Growth Standards, while the most affected was body height. Meanwhile, higher stunting frequency and greater deterioration of both the body height and weight happened in elder age (aged 13–60 months) rather than in infant stage (aged 0–12 months) among these patients. Our results confirmed that intervention should be given at early age to prevent the growth retardation of TOF patients getting severer.

scholarly journals Detection of 15-bp Deletion Mutation within PLAG1 Gene and Its Effects on Growth Traits in Goats

Animals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 2064
Author(s):  
Zhenyu Wei ◽  
Ke Wang ◽  
Hui Wu ◽  
Zhen Wang ◽  
Chuanying Pan ◽  
...  
Keyword(s):  
Body Weight ◽  
Growth Traits ◽  
Body Height ◽  
The Body ◽  
Chest Circumference ◽  
Dairy Goat ◽  
Cashmere Goat ◽  
Indel Mutation ◽  
Body Stature ◽  
Body Index

Stature and weight are important growth and development traits for animals, which also significantly affect the productivity of livestock. Polymorphic adenoma gene 1 (PLAG1) is located in the growth-related quantitative trait nucleotides (QTN), and its variation has been determined to significantly affect the body stature of bovines. This study found that novel 15-bp InDel could significantly influence important growth traits in goats. The frequencies of genotypes of the 15-bp mutation and relationship with core growth traits such as body weight, body height, height at hip cross, chest circumference, hip width and body index were explored in 1581 individuals among 4 Chinese native goat breeds. The most frequent genotypes of Shaanbei white Cashmere goat (SWCG), Inner Mongolia White Cashmere goat (IMCG) and Guanzhong Dairy goat (GZDG) were II genotypes (insertion/insertion), and the frequency of ID genotype (insertion/deletion) was found to be slightly higher than that of II genotype in Hainan Black goat (HNBG), showing that the frequency of the I allele was higher than that of the D allele. In adult goats, there were significant differences between 15-bp variation and body weight, chest circumference and body height traits in SWCG (p < 0.05). Furthermore, the locus was also found to be significantly correlated with the body index of HNBG (p = 0.044) and hip width in GZDG (p = 0.002). In regard to lambs, there were significant differences in height at the hip cross of SWCG (p = 0.036) and hip width in IMWC (p = 0.005). The corresponding results suggest that the 15-bp InDel mutation of PLAG1 is associated with the regulation of important growth characteristics of both adult and lamb of goats, which may serve as efficient molecular markers for goat breeding.

scholarly journals Biomechanical Aspects of the Foot Arch, Body Balance and Body Weight Composition of Boys Training Football

2021 ◽  
Vol 18 (9) ◽  
pp. 5017
Author(s):  
Joanna M. Bukowska ◽  
Małgorzata Jekiełek ◽  
Dariusz Kruczkowski ◽  
Tadeusz Ambroży ◽  
Jarosław Jaszczur-Nowicki
Keyword(s):  
Body Composition ◽  
Body Height ◽  
Study Groups ◽  
The Body ◽  
Whole Body ◽  
Training Methods ◽  
Training Experience ◽  
Mean Values ◽  
Significance Level ◽  
Body Balance

Background: The aim of the study is to assess the body balance and podological parameters and body composition of young footballers in the context of the control of football training. Methods: The study examined the distribution of the pressure of the part of the foot on the ground, the arch of the foot, and the analysis of the body composition of the boys. The pressure center for both feet and the whole body was also examined. The study involved 90 youth footballers from Olsztyn and Barczewo in three age groups: 8–10 years, 11–13 years old, and 14–16 years. The study used the Inbody 270 body composition analyzer and the EPSR1, a mat that measures the pressure distribution of the feet on the ground. Results: The results showed statistically significant differences in almost every case for each area of the foot between the groups of the examined boys. The most significant differences were observed for the metatarsal area and the left heel. In the case of stabilization of the whole body, statistically significant differences were noted between all study groups. In the case of the body composition parameters, in the examined boys, a coherent direction of changes was noticed for most of them. The relationships and correlations between the examined parameters were also investigated. The significance level in the study was set at p < 0.05. Conclusions: Under the training rigor, a statistically significant increase in stability was observed with age. The total length of the longitudinal arch of both feet of the examined boys showed a tendency to flatten in direct proportion to the age of the examined boys. Mean values of the body composition parameters reflect changes with the ontogenetic development, basic somatic parameters (body height and weight) and training experience, and thus with the intensity and volume of training. This indicates a correct training process that does not interfere with the proper development of the body in terms of tissue and biochemical composition.

scholarly journals Optimal nonlinear eddy viscosity in Galerkin models of turbulent flows

2015 ◽  
Vol 766 ◽  
pp. 337-367 ◽  
Author(s):  
Bartosz Protas ◽  
Bernd R. Noack ◽  
Jan Östh
Keyword(s):  
Turbulent Flows ◽  
High Speed ◽  
Eddy Viscosity ◽  
Broad Class ◽  
Constitutive Relations ◽  
Body Height ◽  
Mixing Layer ◽  
The Body ◽  
Stream Velocity ◽  
Initial Vorticity

AbstractWe propose a variational approach to the identification of an optimal nonlinear eddy viscosity as a subscale turbulence representation for proper orthogonal decomposition (POD) models. The ansatz for the eddy viscosity is given in terms of an arbitrary function of the resolved fluctuation energy. This function is found as a minimizer of a cost functional measuring the difference between the target data coming from a resolved direct or large-eddy simulation of the flow and its reconstruction based on the POD model. The optimization is performed with a data-assimilation approach generalizing the 4D-VAR method. POD models with optimal eddy viscosities are presented for a 2D incompressible mixing layer at $\mathit{Re}=500$ (based on the initial vorticity thickness and the velocity of the high-speed stream) and a 3D Ahmed body wake at $\mathit{Re}=300\,000$ (based on the body height and the free-stream velocity). The variational optimization formulation elucidates a number of interesting physical insights concerning the eddy-viscosity ansatz used. The 20-dimensional model of the mixing-layer reveals a negative eddy-viscosity regime at low fluctuation levels which improves the transient times towards the attractor. The 100-dimensional wake model yields more accurate energy distributions as compared to the nonlinear modal eddy-viscosity benchmark proposed recently by Östh et al. (J. Fluid Mech., vol. 747, 2014, pp. 518–544). Our methodology can be applied to construct quite arbitrary closure relations and, more generally, constitutive relations optimizing statistical properties of a broad class of reduced-order models.

scholarly journals A Two Joint Neck Model to Identify Malposition of the Head Relative to the Thorax

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3297
Author(s):  
Philipp M. Schmid ◽  
Christoph M. Bauer ◽  
Markus J. Ernst ◽  
Bettina Sommer ◽  
Lars Lünenburger ◽  
...  
Keyword(s):  
Neck Pain ◽  
Body Height ◽  
Biomechanical Model ◽  
The Body ◽  
Head Orientation ◽  
Neck Length ◽  
Proposed Model ◽  
Biofeedback System ◽  
Simple Measurement ◽  
The Impact

Neck pain is a frequent health complaint. Prolonged protracted malpositions of the head are associated with neck pain and headaches and could be prevented using biofeedback systems. A practical biofeedback system to detect malpositions should be realized with a simple measurement setup. To achieve this, a simple biomechanical model representing head orientation and translation relative to the thorax is introduced. To identify the parameters of this model, anthropometric data were acquired from eight healthy volunteers. In this work we determine (i) the accuracy of the proposed model when the neck length is known, (ii) the dependency of the neck length on the body height, and (iii) the impact of a wrong neck length on the models accuracy. The resulting model is able to describe the motion of the head with a maximum uncertainty of 5 mm only. To achieve this high accuracy the effective neck length must be known a priory. If however, this parameter is assumed to be a linear function of the palpable neck length, the measurement error increases. Still, the resulting accuracy can be sufficient to identify and monitor a protracted malposition of the head relative to the thorax.

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