Analysis of Cyclist’s Drag on the Aero Position Using Numerical Simulations and Analytical Procedures: A Case Study

Background: Resistance acting on a cyclist is a major concern among the cycling fraternity. Most of the testing methods require previous training or expensive equipment and time-consuming set-ups. By contrast, analytical procedures are more affordable and numerical simulations are perfect for manipulating and controlling inputs. The aim of this case study was to compare the drag of a cyclist in the aero position as measured using numerical simulation and analytical procedures. Methods: An elite male cyclist (65 kg in mass and 1.72 m in height) volunteered to take part in this research. The cyclist was wearing his competition gear, helmet and bicycle. A three-dimensional model of the bicycle and cyclist in the aero position was obtained to run the numerical simulations. Computational fluid dynamics (CFD) and a set of analytical procedures were carried out to assess drag, frontal area and drag coefficient, between 1 m/s and 22 m/s, with increments of 1 m/s. The t-test paired samples and linear regression were selected to compare, correlate and assess the methods agreement. Results: No significant differences (t = 2.826; p = 0.275) between CFD and analytical procedures were found. The linear regression showed a very high adjustment for drag (R2 = 0.995; p < 0.001). However, the drag values obtained by the analytical procedures seemed to be overestimated, even though without effect (d = 0.11). Conclusions: These findings suggest that drag might be assessed using both a set of analytical procedures and CFD.

Download Full-text

The Aerodynamics and Energy Cost Assessment of an Able-Bodied Cyclist and Amputated Models by Computer Fluid Dynamics

Medicina ◽

10.3390/medicina56050241 ◽

2020 ◽

Vol 56 (5) ◽

pp. 241 ◽

Cited By ~ 1

Author(s):

Pedro Forte ◽

Daniel A. Marinho ◽

Ricardo Silveira ◽

Tiago M. Barbosa ◽

Jorge E. Morais

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Linear Regression ◽

Numerical Simulations ◽

Energy Cost ◽

Computational Fluid Dynamics Cfd ◽

Computer Fluid Dynamics ◽

Analytical Procedures ◽

One Way Anova ◽

Very High

Background and Objectives: The aim of this study was to assess and compare the drag and energy cost of three cyclists assessed by computational fluid dynamics (CFD) and analytical procedures. Materials and methods: A transradial (Tr) and transtibial (Tt) were compared to a full-body cyclist at different speeds. An elite male cyclist with 65 kg of mass and 1.72 m of height volunteered for this research with his competition cloths, helmet and bicycle with 5 kg of mass. A 3D model of the bicycle and cyclist in the upright position was obtained for numerical simulations. Upon that, two more models were created, simulating elbow and knee-disarticulated athletes. Numerical simulations by computational fluid dynamics and analytical procedures were computed to assess drag and energy cost, respectively. Results: One-Way ANOVA presented no significant differences between cyclists for drag (F = 0.041; p = 0.960; η2 = 0.002) and energy cost (F = 0.42; p = 0.908; η2 = 0.002). Linear regression presented a very high adjustment for absolute drag values between able-bodied and Tr (R2 = 1.000; Ra2 = 1.000; SEE = 0.200) and Tt (R2 = 1.00; Ra2 = 1.000; SEE = 0.160). The linear regression for energy cost presented a very high adjustment for absolute values between able-bodied and Tr (R2 = 1.000; Ra2 = 1.000; SEE = 0.570) and Tt (R2 = 1.00; Ra2 = 1.00; SEE = 0.778). Conclusions: This study suggests that drag and energy cost was lower in the able-bodied, followed by the Tr and Tt cyclists.

Download Full-text

An Investigation into the Optimal Experience in Reading Journalistic Texts in Light of Instructing Fairclough’s and Van Dijk’s Model

International and Multidisciplinary Journal of Social Sciences ◽

10.17583/rimcis.2017.2848 ◽

2017 ◽

Vol 6 (3) ◽

pp. 232 ◽

Cited By ~ 1

Author(s):

Seyyed Alireza Hamedi ◽

Seyyedeh Mina Hamedi ◽

Seyyedeh Maryam Hamedi ◽

Seyyedeh Massoumeh Hamedi

Keyword(s):

Critical Discourse Analysis ◽

Community Sample ◽

Three Dimensional ◽

Treatment Phase ◽

Critical Discourse ◽

Optimal Experience ◽

Flow Experience ◽

Three Dimensional Model ◽

Paired Samples ◽

Proficiency Level

The present study aims at exploring the extent to which Critical Discourse Analysis (CDA) familiarity may have an impact on flow experience. In so doing, the community sample of 60 students comprising 16 males and 44 females participated in the study. Initially, the pretest was conducted to ensure the homogeneity of their proficiency level. Besides, the participants were asked to reflect on their flow experience while reading three distinct genres of journalistic texts prior to the application of the treatment. During the treatment phase, they were instructed how to critically examine other journalistic texts relying on Fairclough’s (1989) three dimensional model along with Van Dijk’s (1995) theoretical framework of CDA over 10 successive sessions. Finally, utilizing paired- samples t-tests, the results of the posttests on the very three texts which were conducted at the pretest stage, indicated that the application of CDA has a significant influence on the students’ optimal experience while reading descriptive, expository, and narrative genres of journalistic texts.

Download Full-text

A Mixing Behavior Study of Biomass Particles and Sands in Fluidized Bed Based on CFD-DEM Simulation

Energies ◽

10.3390/en12091801 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1801 ◽

Cited By ~ 2

Author(s):

Heng Wang ◽

Zhaoping Zhong

Keyword(s):

Fluidized Bed ◽

Three Dimensional ◽

Vertical Direction ◽

Gas Velocity ◽

Three Dimensional Model ◽

Large Size ◽

Behavior Study ◽

Mixing Behavior ◽

Computational Fluid Dynamics Cfd ◽

Biomass Particles

The present paper studied the mixing characteristics of biomass and sands in a fluidized bed. A three dimensional model is calculated on the basis of computational fluid dynamics (CFD) and the discrete element method (DEM), while the lab-scale experiments under similar conditions are conducted. To investigate the mixing behavior of biomass and sands, particle distribution, particles time averaged kinetic motion and the Lacey index are analyzed and the effects of gas velocity and biomass size are discussed. Gas velocity provides the basic motion for particle movement and biomass particles gain a lot more kinetic motion than sands due to their large size. The biomass mixing process in a horizontal direction is more sensitive to gas velocity than in a vertical direction. Biomass size could slightly affect the mixing quality and a well mixing in fluidized bed could be reached if the size of biomass to sands is smaller than 4 times.

Download Full-text

Disassembly Sequence Planning (DSP) Applied to a Gear Box: Comparison between Two Literature Studies

Applied Sciences ◽

10.3390/app10134591 ◽

2020 ◽

Vol 10 (13) ◽

pp. 4591 ◽

Cited By ~ 2

Author(s):

Leonardo Frizziero ◽

Alfredo Liverani

Keyword(s):

Three Dimensional ◽

Evaluation Criteria ◽

Three Dimensional Model ◽

Specific Component ◽

Disassembly Sequence Planning ◽

Sequence Planning ◽

New Methods ◽

Disassembly Sequence ◽

Mechanical Products

This work aims to analyze the characteristics and importance that design techniques for disassembly assume in the modern design phase of a mechanism. To this end, the study begins by considering a three-dimensional model of a gear motor, taken from the components of which the overall drawings are arranged and from the relief of those not available. Once the mechanism has been digitally reconstructed, the activity focuses on the study of the optimal disassembly sequence by comparing different methodologies, according to two evaluation criteria—minimizing the time taken and minimizing the number of tool changes necessary to complete the sequence. The main results of the work are (1) defining a standard methodology to improve disassembly sequence planning, (2) finding the best disassembly sequence for the specific component among the literature and eventually new methods, and (3) offering to the industrial world a way to optimize maintenance operations in mechanical products. Referring to the limitation of the present works, it can be affirmed that the results are limited to the literature explored and to the case study examined.

Download Full-text

Influence of airflow dynamics on vortices in the human nasal cavity

Engineering Computations ◽

10.1108/ec-08-2018-0335 ◽

2019 ◽

Vol 36 (9) ◽

pp. 3164-3179

Author(s):

Punjan Dohare ◽

Amol P. Bhondekar ◽

Anupma Sharma ◽

C. Ghanshyam

Keyword(s):

Numerical Simulations ◽

Nasal Cavity ◽

Three Dimensional ◽

Nasal Airflow ◽

Nasal Valve ◽

Dimensional Model ◽

Three Dimensional Model ◽

Flow Rates ◽

Content Type ◽

Human Nose

Purpose The purpose of this paper is to understand the effect of airflow dynamics on vortices for different flow rates using the human nose three-dimensional model. Design/methodology/approach Olfaction originates with air particles travelling from an external environment to the upper segment of the human nose. This phenomenon is generally understood by using the nasal airflow dynamics, which enhances the olfaction by creating the vortices in the human nose. An anatomical three-dimensional model of the human nasal cavity from computed tomography (CT) scan images using the MIMICS software (Materialise, USA) was developed in this study. Grid independence test was performed through volume flow rate, pressure drop from nostrils and septum and average velocity near the nasal valve region using a four computational mesh model. Computational fluid dynamics (CFD) was used to examine the flow pattern and influence of airflow dynamics on vortices in the nasal cavity. Numerical simulations were conducted for the flow rates of 7.5, 10, 15 and 20 L/min using numerical finite volume methods. Findings At coronal cross-sections, dissimilar nasal airflow patterns were observed for 7.5, 10, 15 and 20 L/min rate of fluid flow in the human nasal cavity. Vortices that are found at the boundaries with minimum velocity creates deceleration zone in the nose vestibule region, which is accompanied by flow segregation. Maximum vortices were observed in the nasal valve region and the posterior end of the turbinate region, which involves mixing and recirculation and is responsible for enhancing the smelling process. Practical implications The proposed analysis is applicable to design the sensor chamber for electronic noses. Originality/value In this paper, the influence of airflow dynamics on vortices in the human nasal cavity is discussed through numerical simulations.

Download Full-text

Effect of Blade Numbers on Pressure Drop of Axial Cyclone Separators by CFD

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.55-57.343 ◽

2011 ◽

Vol 55-57 ◽

pp. 343-347 ◽

Cited By ~ 2

Author(s):

Yi Gang Luan ◽

Hai Ou Sun

Keyword(s):

Pressure Drop ◽

Stokes Equations ◽

Three Dimensional ◽

Navier Stokes ◽

Three Dimensional Model ◽

Navier Stokes Equations ◽

Pressure Drops ◽

Computational Fluid Dynamics Cfd ◽

Cfd Method ◽

Resistance Performance

In this article, computational fluid dynamics(CFD) method is used to predict the effect of blade numbers on the pressure drop of axial cyclone separators. A three-dimensional model is built to acquire the resistance of axial cyclone separators with different blade numbers. The flow field inside cyclone separators is calculated using 3D Reynolds-averaged Navier-Stokes equations. And turbulence model is used to simulate the Reynold stress. Also pressure drop of cyclone separators with different blade numbers is expressed as a function of different inlet velocities. At the same inlet velocity with increasing the blade numbers, pressure drops of cyclones reduce greatly. And changing the blade number of cyclone separator is an effective method to improve its resistance performance.

Download Full-text

Calibration of a Three-dimensional slope stability evaluation in Brazilian iron open pit mine

10.21203/rs.3.rs-337958/v1 ◽

2021 ◽

Author(s):

Vidal Félix Navarro Torres ◽

Rodrigo Dockendorff ◽

Juan Manuel Girao Sotomayor ◽

Cristian Castro ◽

Aristotelina Ferreira da Silva

Keyword(s):

Three Dimensional ◽

Structural Features ◽

Open Pit ◽

Dimensional Model ◽

Three Dimensional Model ◽

Strength Parameters ◽

Dimensional Section ◽

The Stability ◽

Evaluation Techniques

Abstract It has historically been frequent among geotechnical practitioners, that the stability analysis of the slopes of an open pit is performed using a two dimensional section representing the highest and steepest walls within a certain geological setting. However, the literature shows that to predict rupture events in an open pit, a three-dimensional analysis would better represent the actual conditions, as the spatial distribution of the lithology and the structural features play an important role when defining the stability of the slopes. This paper presents the case study of an open it located in Brazil, which experienced instabilities between the years 2001-2019. An evaluation of the behavior of the open pit was performed by calibrating the strength parameters to represent the best documented rupture events. The three-dimensional model was made using the FLAC3D software. The results show that there is a good correlation between the results of the model and the reports of past instabilities. Finally, recommendations are presented for the inter-ramp angles for each lithology based on the calibrated stability analyzes performed. This work seeks to contribute to the knowledge in evaluation techniques for the three-dimensional behavior of open pits.

Download Full-text

ASSESSMENT OF THE ACCURACY OF DEM FROM PANCHROMATIC PLEIADES IMAGERY (CASE STUDY: BANDUNG CITY. WEST JAVA)

International Journal of Remote Sensing and Earth Sciences (IJReSES) ◽

10.30536/j.ijreses.2020.v17.a3329 ◽

2020 ◽

Vol 17 (1) ◽

pp. 34

Author(s):

Rian Nurtyawan ◽

Nadia Fiscarina

Keyword(s):

Accuracy Assessment ◽

Three Dimensional ◽

Extraction Process ◽

Srtm Dem ◽

Ground Control Points ◽

Rational Polynomial ◽

Digital Elevation ◽

Dem Accuracy ◽

Very High

Pleiades satellite imagery is very high resolution. with 0.5 m spatial resolution in the panchromatic band and 2.5 m in the multispectral band. Digital elevation models (DEM) are digital models that represent the shape of the Earth's surface in three-dimensional (3D) form. The purpose of this study was to assess DEM accuracy from panchromatic Pleaides imagery. The process conducted was orthorectification using ground control points (GCPs) and the rational function model with rational polynomial coefficient (RFC) parameters. The DEM extraction process employed photogrammetric methods with different parallax concepts. Accuracy assessment was made using 35 independent check points (ICPs) with an RMSE accuracy of ± 0.802 m. The results of the Pleaides DEM image extraction were more accurate than the National DEM (DEMNAS) and SRTM DEM. Accuracy testing of DEMNAS results showed an RMSE of ± 0.955 m. while SRTM DEM accuracy was ± 17.740 m. Such DEM extraction from stereo Pleiades panchromatic images can be used as an element on base maps with a scale of 1: 5.000.

Download Full-text

Numerical Simulation of Iridectomy for Surgical Treatment of Glaucoma

Volume 4 ◽

10.1115/ht-fed2004-56661 ◽

2004 ◽

Author(s):

Satish Kumar ◽

Sumanta Acharya

Keyword(s):

Three Dimensional ◽

Elevated Pressure ◽

Angle Closure Glaucoma ◽

Angle Closure ◽

Posterior Chamber ◽

Three Dimensional Model ◽

Pupillary Block ◽

Flow Simulations ◽

Outflow Pathway ◽

Very High

Pupillary block can lead to a convex bowing of the iris surface due to the increased posterior chamber pressures, and this, in turn, can partially block the outflow pathway through the Trabecular Meshwork (TM). This condition leads to Angle-closure glaucoma by elevating the Intraocular Pressure (IOP) of the eye to very high levels. To alleviate this condition, a surgical process called iridectomy can be performed to create an opening on the iris surface that enables an alternate route for the flow from the posterior chamber to the anterior chamber. This, in turn, reduces the elevated pressure in the eye. In the present work, flow simulations are performed in a three-dimensional model of the human eye, with reduced irido-lenticular gap and partial-blockage of the TM, to model the flow and pressure distribution associated with pupillary block and angle-closure glaucoma. Iridectomy is simulated by creating holes on the iris surface at different locations. The effect of angular locations of the iridectomy holes on the pressure and flow distributions are analyzed.

Download Full-text

Developing of a Simscape Multibody Contact Library for Gothic Arc Ball Screws: A Three-Dimensional Model for Internal Sphere/Grooves Interactions

Volume 4: Dynamics, Vibration, and Control ◽

10.1115/imece2019-10709 ◽

2019 ◽

Author(s):

Antonio Carlo Bertolino ◽

Giovanni Jacazio ◽

Stefano Mauro ◽

Massimo Sorli

Keyword(s):

Complex Geometry ◽

Three Dimensional ◽

Ball Screw ◽

Mechanical Modeling ◽

Three Dimensional Model ◽

Simulation Tools ◽

First Case ◽

Multibody Contact ◽

Helical Grooves

Abstract The Simscape Multibody software is a set of libraries and mechanical modeling and simulation tools for use with Simulink®. For what concerns the contact library, currently it contains only the models to describe impacts between simple geometries, such as spheres, cylinders and planes. When this environment is intended to be used to simulate the 3D dynamics of a system with a complex geometry, such as a ball screw, the built-in blocks are not sufficient. This paper presents a new contact library, containing blocks specifically designed to handle the contacts between a sphere and the two gothic arc helical grooves of a ball screw, as well as the interaction between adjacent spheres. The developed blocks are exploited to create a first case study dynamic model of a single nut not preloaded ball screw in presence of internal backlash. The results highlight the superiority of this multibody approach with respect to the quasi-static or lumped parameters models in terms of extracted information and understanding of the internal mechanics.

Download Full-text