scholarly journals Aerodynamic benefits for a cyclist by drafting behind a motorcycle

2020 ◽  
Vol 23 (1) ◽  
Author(s):  
Bert Blocken ◽  
Fabio Malizia ◽  
Thijs van Druenen ◽  
Stefanie Gillmeier
Keyword(s):  
Fluid Dynamics ◽  
Drag Reduction ◽  
Scientific Literature ◽  
Power Model ◽  
Or Groups ◽  
Television Broadcasting ◽  
Wind Tunnel Measurements ◽  
Calm Weather ◽  
Professional Cycling ◽  
International Cycling Union

AbstractMotorcycles are present in cycling races for reasons including television broadcasting. During parts of the race, these motorcycles ride in front of individual or groups of cyclists. Concerns have been expressed in the professional cycling community that these motorcycles can provide aerodynamic benefits in terms of drag reduction for the cyclists drafting behind them. However, to the best of our knowledge, no information about the extent of these benefits is present in the scientific literature. Therefore, this paper analyses the potential drag reduction for a cyclist by drafting behind a motorcycle. Wind tunnel measurements and numerical simulations with computational fluid dynamics were performed. It was shown that drafting at separation distances d = 2.64, 10, 30 and 50 m can reduce the drag of the cyclist down to 52, 77, 88 and 93% of that of an isolated cyclist, respectively. A cyclist power model is used to convert these drag reductions into potential time gains. For a non-drafting cyclist at a speed of 54 km/h on level road in calm weather, the time gains by drafting at d = 2.64, 10, 30 and 50 m are 12.7, 5.4, 2.7 and 1.6 s per km, respectively. These time differences can influence the outcome of cycling races. The current rules of the International Cycling Union do not prevent these aerodynamic benefits from occurring in races.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

scholarly journals Variable cant angle winglets for improvement of aircraft flight performance

Meccanica ◽  
2020 ◽  
Vol 55 (10) ◽  
pp. 1917-1947
Author(s):  
J. E. Guerrero ◽  
M. Sanguineti ◽  
K. Wittkowski
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Reduction ◽  
Fuel Efficiency ◽  
Aerodynamic Performance ◽  
Flight Performance ◽  
Sweep Angle ◽  
Aircraft Flight ◽  
Induced Drag ◽  
Aircraft Performance

Abstract Traditional winglets are designed as fixed devices attached at the tips of the wings. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving aircraft performance and fuel efficiency. However, because winglets are fixed surfaces, they cannot be used to control lift-induced drag reductions or to obtain the largest lift-induced drag reductions at different flight conditions (take-off, climb, cruise, loitering, descent, approach, landing, and so on). In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different flight phases. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle on the performance of a benchmark wing at Mach numbers of 0.3 and 0.8395. The results obtained demonstrate that by adjusting the cant angle, the aerodynamic performance can be improved at different flight conditions.

Computational Fluid Dynamics (CFD) Simulation of Drag Reduction by Riblets on Automobile

2010 ◽  
Author(s):  
N. N. N. Ghazali ◽  
Y. H. Yau ◽  
A. Badarudin ◽  
Y. C. Lim ◽  
Jane W. Z. Lu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Reduction ◽  
Cfd Simulation ◽  
Computational Fluid Dynamics Cfd

scholarly journals Remoras pick where they stick on blue whales

2020 ◽  
Vol 223 (20) ◽  
pp. jeb226654
Author(s):  
Brooke E. Flammang ◽  
Simone Marras ◽  
Erik J. Anderson ◽  
Oriol Lehmkuhl ◽  
Abhishek Mukherjee ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Reduction ◽  
Experimental Work ◽  
Ecological Monitoring ◽  
Video Recordings ◽  
Venturi Effect ◽  
Separating Flow ◽  
Dynamics Analyses ◽  
Blue Whales

ABSTRACTAnimal-borne video recordings from blue whales in the open ocean show that remoras preferentially adhere to specific regions on the surface of the whale. Using empirical and computational fluid dynamics analyses, we show that remora attachment was specific to regions of separating flow and wakes caused by surface features on the whale. Adhesion at these locations offers remoras drag reduction of up to 71–84% compared with the freestream. Remoras were observed to move freely along the surface of the whale using skimming and sliding behaviors. Skimming provided drag reduction as high as 50–72% at some locations for some remora sizes, but little to none was available in regions where few to no remoras were observed. Experimental work suggests that the Venturi effect may help remoras stay near the whale while skimming. Understanding the flow environment around a swimming blue whale will inform the placement of biosensor tags to increase attachment time for extended ecological monitoring.

An improved active drag reduction system for formula race cars

2019 ◽  
Vol 234 (5) ◽  
pp. 1460-1471
Author(s):  
Mauro Dimastrogiovanni ◽  
Giulio Reina ◽  
Andrea Burzoni
Keyword(s):  
Fluid Dynamics ◽  
Drag Reduction ◽  
Manufacturing Costs ◽  
The Public ◽  
Reduction System ◽  
Rear Wing ◽  
Race Cars ◽  
Full Design ◽  
Main Formula ◽  
System Mechanism

Drag reduction systems are largely employed in racing car competitions to help drivers in overtaking manoeuvres, ensuring a good show to the public. This paper presents a full-design approach to drag reduction systems that includes the computational fluid dynamics estimation of the forces acting on the rear wing, the dynamic analysis of the drag reduction system mechanism and the whole vehicle behaviour through the simulation of an overtaking manoeuvre. For the purposes of this work, a novel drag reduction system mechanism is proposed that features lower aerodynamic disturbance and comparable manufacturing costs than those of drag reduction systems of the main Formula categories.

scholarly journals Intergenerational leisure and family reconciliation

2021 ◽  
Vol 13 (3) ◽  
pp. 1-13
Author(s):  
Mª Ángeles Valdemoros San Emeterio ◽  
Rosa Ana Alonso Ruiz ◽  
Magdalena Sáenz de Jubera Ocón ◽  
Ana Ponce de León Elizondo ◽  
Eva Sanz Arazuri
Keyword(s):  
Scientific Literature ◽  
Descriptive Study ◽  
Residential Area ◽  
Current Situation ◽  
Intermediate Position ◽  
Northern Spain ◽  
Inclusive Language ◽  
Or Groups ◽  
Shared Practice ◽  
Inferential Analysis

Scientific literature suggests the contribution to family reconciliation as a motivation for leisure shared by grandparents and grandchildren. However, there are some discrepant results. The study aimed to examine the need for family reconciliation as a practical motivation for grandparents’ and grandchildren’s shared leisure, and its linkage with its frequency, the geographical residential area, and the cohabitation of both generations in the same home. A questionnaire was administered to 357 grandparents of children aged 6 to 12 years residing in northern Spain, and a descriptive study and inferential analysis of the data were performed. The results placed the need for family reconciliation in an intermediate position, below the motivations of entertainment and emotional motivations, but above those related to co-learning and the absence of other people to perform such activities. The need for family reconciliation is associated with the frequency of shared practice, but not with the geographical residential area or the fact that both generations cohabitate at the same address. The possible exceptionality of the current situation, within the framework of COVID-19, which may have produced significant alterations in the grandparent-grandchildren relationship, is discussed, with the consequent need to continue this line of inquiry. [1] Throughout the document, an attempt will be made to use inclusive language, although "under Law 3/2007 of 22 March, for the effective equality of women and men, any reference to positions, persons, or groups included in this document in the masculine, are to be understood as including both women and men.”

scholarly journals Variable Cant Angle Winglets for Improvement of Aircraft Flight Performance

2019 ◽  
Author(s):  
Joel Guerrero ◽  
Kevin Wittkowski ◽  
Marco Sanguineti
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Reduction ◽  
Fuel Efficiency ◽  
Aerodynamic Performance ◽  
Flight Performance ◽  
Sweep Angle ◽  
Aircraft Flight ◽  
Induced Drag ◽  
Aircraft Performance

Traditional winglets are designed as fixed devices attached at the tips of the wings. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving aircraft performance and fuel efficiency. However, because winglets are fixed surfaces, they cannot be used to control lift-induced drag reductions or to obtain the largest lift-induced drag reductions at different flight conditions (take-off, climb, cruise, loitering, descent, approach, landing, and so on). In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different flight phases. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle on the performance of a benchmark wing at Mach numbers of 0.3 and 0.8395. The results obtained demonstrate that by adjusting the cant angle, the aerodynamic performance can be improved at different flight conditions.

scholarly journals CFD Study of the Impact of Variable Cant Angle Winglets on Total Drag Reduction

Aerospace ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 126 ◽  
Author(s):  
Joel Guerrero ◽  
Marco Sanguineti ◽  
Kevin Wittkowski
Keyword(s):  
Fluid Dynamics ◽  
Drag Reduction ◽  
Fuel Efficiency ◽  
Aerodynamic Performance ◽  
Fuel Saving ◽  
Sweep Angle ◽  
Total Drag ◽  
Induced Drag ◽  
Aircraft Performance ◽  
The Impact

Winglets are commonly used drag-reduction and fuel-saving technologies in today’s aviation. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving fuel efficiency and aircraft performance. Traditional winglets are designed as fixed devices attached at the tips of the wings. However, because they are fixed surfaces, they give their best lift-induced drag reduction at a single design point. In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different angle-of-attack values. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle in the performance of a benchmark wing at a Mach number of 0.8395. The results obtained demonstrate that by carefully adjusting the cant angle, the aerodynamic performance can be improved at different angles of attack.

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