scholarly journals Drag coefficient and frontal area of a solitary mature tree

2022 ◽  
Vol 220 ◽  
pp. 104854
Author(s):  
Casper C.A. Bekkers ◽  
Nikolas Angelou ◽  
Ebba Dellwik
Keyword(s):  
Drag Coefficient ◽  
Frontal Area ◽  
Mature Tree

Aerodynamics of Cyclist Posture, Bicycle and Helmet Characteristics in Time Trial Stage

2012 ◽  
Vol 28 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Vincent Chabroux ◽  
Caroline Barelle ◽  
Daniel Favier
Keyword(s):  
Statistical Analysis ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Drag Force ◽  
Time Trial ◽  
Frontal Area ◽  
Significant Gain ◽  
Upper Limbs ◽  
Force Coefficient ◽  
Coefficient Reduction

The present work is focused on the aerodynamic study of different parameters, including both the posture of a cyclist’s upper limbs and the saddle position, in time trial (TT) stages. The aerodynamic influence of a TT helmet large visor is also quantified as a function of the helmet inclination. Experiments conducted in a wind tunnel on nine professional cyclists provided drag force and frontal area measurements to determine the drag force coefficient. Data statistical analysis clearly shows that the hands positioning on shifters and the elbows joined together are significantly reducing the cyclist drag force. Concerning the saddle position, the drag force is shown to be significantly increased (about 3%) when the saddle is raised. The usual helmet inclination appears to be the inclination value minimizing the drag force. Moreover, the addition of a large visor on the helmet is shown to provide a drag coefficient reduction as a function of the helmet inclination. Present results indicate that variations in the TT cyclist posture, the saddle position and the helmet visor can produce a significant gain in time (up to 2.2%) during stages.

The Effect of Air Resistance on the Jumping Performance of Insects

1979 ◽  
Vol 82 (1) ◽  
pp. 105-121
Author(s):  
H. C. BENNET-CLARK ◽  
G. M. ALDER
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Optimal Condition ◽  
Scale Effect ◽  
Aerodynamic Drag ◽  
The Body ◽  
Frontal Area ◽  
Mass Ratio ◽  
Design Constraints ◽  
Air Resistance

A spring gun was constructed to propel objects at known velocities of between 1 and 4.5 m.s−1. This was used to project insects and various models in a vertical trajectory. By comparing the height attained in air by the insects or models with the height theoretically possible in vacuo, the energy lost against air resistance was observed. Small insects have a higher frontal area to mass ratio than larger ones so have relatively more aerodynamic drag and attain lower heights. The observed effect may be expressed in terms of the drag coefficient, CD. Fleas and locusts have CD of about 1 Winged flies have CD of about 1.5 which falls to about 1 when the wings are amputated and to about o-8 when the legs are amputated. Aptery is advantageous in jumping insects. From experiments with models, it appears that the optimal condition for small jumping insects is that the body should be as compact as possible to reduce the frontal area to mass ratio. Thus dense spherical bodies are favoured. Some species of jumping insect have densities of about 1 mg.mm−3 while some flying beetles and flies have densities between 0.3 and 0.8 mg.mm−3. The Reynolds number at which the experiments were performed was from 65–205 for fleas up to 740-2340 for locusts. The models operated in similar ranges. At a velocity which would propel a larger animal to a height of 1 m, fleas weighing 0.4 mg only reach about 0.4 m. At lower initial velocities, proportionately less energy is wasted against air resistance so the jump efficiency is higher. Most fleas jump to a height of about 0.1 m with an efficiency of 0.8 while locusts jump to a height of 0.35 m with an efficiency of over 0.9. Air resistance is thus an important scale effect in jumping insects and provides its own design constraints.

Bulk drag coefficient of a subaquatic vegetation subjected to irregular waves: Influence of Reynolds and Keulegan-Carpenter numbers

2020 ◽  
pp. 34-42
Author(s):  
Thibault Chastel ◽  
Kevin Botten ◽  
Nathalie Durand ◽  
Nicole Goutal
Keyword(s):  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Empirical Relationship ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Geometrical Parameters ◽  
Flume Experiments ◽  
Seagrass Meadows ◽  
Artificial Vegetation

Seagrass meadows are essential for protection of coastal erosion by damping wave and stabilizing the seabed. Seagrass are considered as a source of water resistance which modifies strongly the wave dynamics. As a part of EDF R & D seagrass restoration project in the Berre lagoon, we quantify the wave attenuation due to artificial vegetation distributed in a flume. Experiments have been conducted at Saint-Venant Hydraulics Laboratory wave flume (Chatou, France). We measure the wave damping with 13 resistive waves gauges along a distance L = 22.5 m for the “low” density and L = 12.15 m for the “high” density of vegetation mimics. A JONSWAP spectrum is used for the generation of irregular waves with significant wave height Hs ranging from 0.10 to 0.23 m and peak period Tp ranging from 1 to 3 s. Artificial vegetation is a model of Posidonia oceanica seagrass species represented by slightly flexible polypropylene shoots with 8 artificial leaves of 0.28 and 0.16 m height. Different hydrodynamics conditions (Hs, Tp, water depth hw) and geometrical parameters (submergence ratio α, shoot density N) have been tested to see their influence on wave attenuation. For a high submergence ratio (typically 0.7), the wave attenuation can reach 67% of the incident wave height whereas for a low submergence ratio (< 0.2) the wave attenuation is negligible. From each experiment, a bulk drag coefficient has been extracted following the energy dissipation model for irregular non-breaking waves developed by Mendez and Losada (2004). This model, based on the assumption that the energy loss over the species meadow is essentially due to the drag force, takes into account both wave and vegetation parameter. Finally, we found an empirical relationship for Cd depending on 2 dimensionless parameters: the Reynolds and Keulegan-Carpenter numbers. These relationships are compared with other similar studies.

Numerical Comparison of Drag Coefficient between Nacelle Lip-Skin with and without Bias Acoustic Liner

2016 ◽  
Vol 10 (6) ◽  
pp. 390 ◽  
Author(s):  
Qummare Azam ◽  
Mohd Azmi Ismail ◽  
Nurul Musfirah Mazlan ◽  
Musavir Bashir
Keyword(s):  
Drag Coefficient ◽  
Numerical Comparison ◽  
Acoustic Liner

Cyclanilide Spray Increases Branching in Containerized Whip Production

2007 ◽  
Vol 25 (4) ◽  
pp. 221-228
Author(s):  
Petra Sternberg ◽  
Daniel K. Struve
Keyword(s):  
Shoot Elongation ◽  
Major Goal ◽  
Mature Tree ◽  
Lateral Branching ◽  
Reduced Height ◽  
Second Year ◽  
One Year ◽  
Tree Quality ◽  
Tree Pruning ◽  
Number Of Branches

Abstract A major goal in the production of tree whips is to produce appropriately sized, well-branched liners with a crown form similar to that of a mature tree. Pruning is used to induce lateral branching. This can result in poor tree quality, reduced growth and the practice is labor intensive. An alternative to mechanical pruning, foliar Cyclanilide® (CYC) sprays at 0, 56, 1 12 and 223 ppm were applied to container grown whips to determine its effect on branching of Amelanchier; Cercis, Malus and Tilia whips. Most species responded to CYC sprays with increased lateral branching if treated during active shoot elongation. Cyclanilide® sprays of 1 12 ppm produced the greatest number of branches. Sprays at 56 ppm resulted in reduced branching (relative to 112 ppm), while sprays of 223 ppm did not increase the number of branches, relative to sprays of 112 ppm, but reduced growth. Cyclanilide® sprays reduced height growth, relative to untreated whips, but did not alter height diameter growth. Cyclanilide® foliar applications to container -grown whips during periods of active shoot elongation increased branching in one-year-old whips that normally do not branch until the second year of production. Further, the origin of lateral branching can be controlled by timing of CYC application. The results indicate that CYC foliar sprays can be an important tool in the production of one-year-old branched whips.

EFFECT OF THE MACRO-SCALE TOPOLOGY OVER THE EFFECTIVE DRAG COEFFICIENT IN DENSE GAS-SOLID FLUIDIZED FLOWS

2018 ◽  
Author(s):  
Seyed Reza Amini Niaki ◽  
Joseph Mouallem ◽  
Christian Milioli ◽  
Fernando Milioli
Keyword(s):  
Drag Coefficient ◽  
Dense Gas ◽  
Macro Scale

The frontal longitudinal system as revealed through the fiber microdissection technique: structural evidence underpinning the direct connectivity of the prefrontal-premotor circuitry

2020 ◽  
Vol 133 (5) ◽  
pp. 1503-1515 ◽  
Author(s):  
Spyridon Komaitis ◽  
Aristotelis V. Kalyvas ◽  
Georgios P. Skandalakis ◽  
Evangelos Drosos ◽  
Evgenia Lani ◽  
...  
Keyword(s):  
Primary Motor Cortex ◽  
Premotor Cortex ◽  
Frontal Area ◽  
Frontal Pole ◽  
Fiber System ◽  
Dorsolateral Prefrontal ◽  
Anterior Extension ◽  
Brodmann Areas ◽  
Longitudinal Fiber ◽  
Long Fibers

OBJECTIVEThe purpose of this study was to investigate the morphology, connectivity, and correlative anatomy of the longitudinal group of fibers residing in the frontal area, which resemble the anterior extension of the superior longitudinal fasciculus (SLF) and were previously described as the frontal longitudinal system (FLS).METHODSFifteen normal adult formalin-fixed cerebral hemispheres collected from cadavers were studied using the Klingler microdissection technique. Lateral to medial dissections were performed in a stepwise fashion starting from the frontal area and extending to the temporoparietal regions.RESULTSThe FLS was consistently identified as a fiber pathway residing just under the superficial U-fibers of the middle frontal gyrus or middle frontal sulcus (when present) and extending as far as the frontal pole. The authors were able to record two different configurations: one consisting of two distinct, parallel, longitudinal fiber chains (13% of cases), and the other consisting of a single stem of fibers (87% of cases). The fiber chains’ cortical terminations in the frontal and prefrontal area were also traced. More specifically, the FLS was always recorded to terminate in Brodmann areas 6, 46, 45, and 10 (premotor cortex, dorsolateral prefrontal cortex, pars triangularis, and frontal pole, respectively), whereas terminations in Brodmann areas 4 (primary motor cortex), 47 (pars orbitalis), and 9 were also encountered in some specimens. In relation to the SLF system, the FLS represented its anterior continuation in the majority of the hemispheres, whereas in a few cases it was recorded as a completely distinct tract. Interestingly, the FLS comprised shorter fibers that were recorded to interconnect exclusively frontal areas, thus exhibiting different fiber architecture when compared to the long fibers forming the SLF.CONCLUSIONSThe current study provides consistent, focused, and robust evidence on the morphology, architecture, and correlative anatomy of the FLS. This fiber system participates in the axonal connectivity of the prefrontal-premotor cortices and allegedly subserves cognitive-motor functions. Based in the SLF hypersegmentation concept that has been advocated by previous authors, the FLS should be approached as a distinct frontal segment within the superior longitudinal system.

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