Drag analysis with a self-propelled flexible swimmer

2021 ◽  
Vol 6 (5) ◽  
Author(s):  
David Gross ◽  
Yann Roux ◽  
Christophe Raufaste ◽  
Argentina Médéric
Keyword(s):  
Drag Analysis

Gliding Flight of the Dog-Faced Bat Rousettus Aegyptiacus Observed in a Wind Tunnel

1971 ◽  
Vol 55 (3) ◽  
pp. 833-845 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Trailing Edge ◽  
Number Range ◽  
High Speeds ◽  
Gliding Flight ◽  
Speed Range ◽  
Simple Regression Analysis ◽  
Drag Analysis ◽  
Very High

1. A bat was trained to fly in a tilting wind tunnel. Stereoscopic photographs were taken, both by reflected and by transmitted light, and measurements of best gliding angle were made. 2. Variation of wing span and area at different speeds was much less than in birds. This is attributed to the construction of the wing, which prevents the bat from folding back the manus in flight, because this would lead to collapse of the plagiopatagium. 3. The trailing edge of the wing is normally deflected upwards in flight, at least in the distal parts. This is interpreted as providing longitudinal stability. The plagiopatagialis proprii muscles appear to act as an elevator, by deflecting the trailing edge of the plagiopatagium upwards. 4. The speed range over which the bat could glide was 5·3-11·0 m/s. Its maximum lift coefficient was 1·5, and its best glide ratio 6·8:1. The Reynolds number range, based on mean chord, was 3·26 x 104 to 6·79 x 104. 5. A simple regression analysis of the glide polar indicated a very high span efficiency factor (k) and low wing profile drag coefficient (Cdp). On the other hand, a drag analysis on the assumption that k = 1 leads to an improbably large increase in the estimated Cdp at low speeds. It is suggested that the correct interpretation probably lies between these extremes, with k ≊ 1·5; Cdp would then be about 0·02 at high speeds, rising to somewhat over 0·1 at the minimum speed. 6. It would appear that the bat is not so good as a pigeon at fast gliding, but better at low-speed manoeuvring. On most points of performance, however, the two are remarkably similar.

Theoretical Drag Analysis of a Skier in the Downhill Speed Lace

1989 ◽  
Vol 5 (1) ◽  
pp. 26-39 ◽  
Author(s):  
Sauli Savolainen
Keyword(s):  
Potential Theory ◽  
Velocity Potential ◽  
Theoretical Calculations ◽  
Aerodynamic Characteristics ◽  
Tangential Direction ◽  
Optimum Shape ◽  
Drag Forces ◽  
Postural Changes ◽  
Drag Analysis ◽  
Base Drag

The aerodynamics of the skier’s equipment and the effect of postural changes on the aerodynamic forces acting on the skier during downhill speed racing have been studied theoretically. The aerodynamic characteristics of skier and equipment have been determined by a source panel method based on the velocity potential theory. The calculations indicate that the skier’s torso should be slightly lifted from the tangential direction of downhill during skiing, thus causing a lift force and reducing the friction between the skis and snow. The drag of the torso—tilted by a few degrees—will remain almost the same as the drag of the torso in strict tangential direction. The force acting on the skier’s legs can be directed according to individual needs. The shape of the leg spoilers will give the wanted drag/lift ratio. The optimum shape of the helmet depends on the skiing style. The results introduced here are obtained from theoretical calculations, and their validity should first be tested in a wind tunnel and finally during the normal skiing performance. The calculated drag forces, which are based on the velocity potential theory, do not include the base drag of the skier’s body.

scholarly journals On-site cycling drag analysis with the Ring of Fire

2019 ◽  
Vol 60 (6) ◽  
Author(s):  
Alexander Spoelstra ◽  
Luigi de Martino Norante ◽  
Wouter Terra ◽  
Andrea Sciacchitano ◽  
Fulvio Scarano
Keyword(s):  
Drag Analysis

Skin-friction drag analysis from the forced convection modeling in simplified underwater swimming

2006 ◽  
Vol 39 (13) ◽  
pp. 2535-2541 ◽  
Author(s):  
G. Polidori ◽  
R. Taïar ◽  
S. Fohanno ◽  
T.H. Mai ◽  
A. Lodini
Keyword(s):  
Skin Friction ◽  
Forced Convection ◽  
Friction Drag ◽  
Drag Analysis

Real-Time Software to Estimate Friction Coefficient and Downhole Weight on Bit During Drilling of Horizontal Wells

2014 ◽  
Author(s):  
Mazeda Tahmeen ◽  
Geir Hareland ◽  
Bernt S. Aadnoy
Keyword(s):  
Friction Coefficient ◽  
Real Time ◽  
Information Transfer ◽  
Horizontal Wells ◽  
Drill String ◽  
Surface Measurement ◽  
Drilling Process ◽  
Drilling Data ◽  
Weight On Bit ◽  
Drag Analysis

The increasing complexity and higher drilling cost of horizontal wells demand extensive research on software development for the analysis of drilling data in real-time. In extended reach drilling, the downhole weight on bit (WOB) differs from the surface seen WOB (obtained from on an off bottom hookload difference reading) due to the friction caused by drill string movement and rotation in the wellbore. The torque and drag analysis module of a user-friendly real-time software, Intelligent Drilling Advisory system (IDAs) can estimate friction coefficient and the effective downhole WOB while drilling. IDAs uses a 3-dimensional wellbore friction model for the analysis. Based on this model the forces applied on a drill string element are buoyed weight, axial tension, friction force and normal force perpendicular to the contact surface of the wellbore. The industry standard protocol, WITSML (Wellsite Information Transfer Standard Markup Language) is used to conduct transfer of drilling data between IDAs and the onsite or remote WITSML drilling data server. IDAs retrieves real-time drilling data such as surface hookload, pump pressure, rotary RPM and surface WOB from the data servers. The survey data measurement for azimuth and inclination versus depth along with the retrieved drilling data, are used to do the analysis in different drilling modes, such as lowering or tripping in and drilling. For extensive analysis the software can investigate the sensitivity of friction coefficient and downhole WOB on user-defined drill string element lengths. The torque and drag analysis module, as well as the real-time software, IDAs has been successfully tested and verified with field data from horizontal wells drilled in Western Canada. In the lowering mode of drilling process, the software estimates the overall friction coefficient when the drill bit is off bottom. The downhole WOB estimated by the software is less than the surface measurement that the drillers used during drilling. The study revealed verification of the software by comparing the estimated downhole WOB with the downhole WOB recorded using a downhole measuring tool.

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