The dynamic behaviour of an arrow in wind

2020 ◽  
Vol 234 (3) ◽  
pp. 268-277
Author(s):  
James L Park
Keyword(s):  
Dynamic Behaviour ◽  
Small Diameter ◽  
Weather Conditions ◽  
Target Distance ◽  
Target Face ◽  
Flexible Beam ◽  
Wind Drift ◽  
Four Score ◽  
Compound Bow ◽  
Lift And Drag

Target archery competitions are conducted outdoors, exposed to the prevailing weather conditions. Competition takes place over long target distances and wind drift of the arrows is a significant cause of score loss. In this article, the dynamic behaviour of an arrow in free flight and wind drift are modelled, allowing for both the arrow initially aligning itself with the resultant airflow and the arrow flexing. The arrow has been modelled as an inextensible flexible beam, and the resulting partial differential equations solved using a finite difference method. Lift and drag for the various arrow components have been calculated using the local angle of attack for those components. It is shown that archers should use small diameter arrow shafts with a high density in order to minimise wind drift. Even for the best arrows, the drift for a 3-m/s side wind is greater than four score rings for a recurve bow at a target distance of 70 m with a 1220-mm diameter target face and nearly two score rings for a compound bow at a target distance of 50 m with an 800-mm diameter target face.

On the dynamic behaviour of a flexible beam carrying a moving mass

1994 ◽  
Vol 5 (4) ◽  
pp. 493-513 ◽  
Author(s):  
F. Khalily ◽  
M. F. Golnaraghi ◽  
G. R. Heppler
Keyword(s):  
Dynamic Behaviour ◽  
Flexible Beam ◽  
Moving Mass

scholarly journals Similarity-based approaches in hydrogeology: proposal of a new concept for data-scarce groundwater resource characterization and prediction

2021 ◽  
Author(s):  
Roland Barthel ◽  
Ezra Haaf ◽  
Markus Giese ◽  
Michelle Nygren ◽  
Benedikt Heudorfer ◽  
...  
Keyword(s):  
Surface Water ◽  
Dynamic Behaviour ◽  
Groundwater Resources ◽  
Opportunity To Learn ◽  
Weather Conditions ◽  
Ungauged Catchments ◽  
Surface Water Hydrology ◽  
Community Effort ◽  
Predictions In Ungauged Basins ◽  
Main Ideas

AbstractA new concept is proposed for describing, analysing and predicting the dynamic behaviour of groundwater resources based on classification and similarity. The concept makes use of the ideas put forward by the “PUB” (predictions in ungauged basins) initiative in surface-water hydrology. One of the approaches developed in PUB uses the principle that similar catchments, exposed to similar weather conditions, will generate a similar discharge response at the catchment outlet. This way, models developed for well-observed catchments can be used to make predictions for ungauged catchments with similar properties (topography, land use, etc.). The concept proposed here applies the same idea to groundwater systems, with the goal to make predictions of the dynamic behaviour of groundwater in poorly observed systems using similarities to well-observed and understood systems. This paper gives an overview of the main ideas, the methodological background, the progress so far, and the challenges that the authors regard as most crucial for further development. One of the main goals of this article is thus to raise interest for this new concept within the groundwater community. There are a multitude of highly interesting aspects to investigate, and a community effort, as with PUB, is required. A second goal is to foster and exchange ideas between the groundwater and surface water research communities who, while often working on similar problems, have often missed the opportunity to learn from each other.

scholarly journals Aerodynamic Performance of a New Double-Flap Wing Sail

2019 ◽  
Vol 26 (4) ◽  
pp. 61-68
Author(s):  
Dongqin Li ◽  
Yili Zhang ◽  
Peng Li ◽  
Jingjing Dai ◽  
Guohuan Li
Keyword(s):  
Cfd Simulation ◽  
Energy Resource ◽  
Weather Conditions ◽  
Aerodynamic Performance ◽  
Natural Energy ◽  
New Type ◽  
Lift And Drag ◽  
Ocean Wind ◽  
Fuel Costs ◽  
Assisted Technologies

Abstract As a type of natural energy resource, wind power is used in the modern implementation of wind-assisted technologies as a method for reducing the fuel consumption and environmental pollution of ocean-going ships. In order to promote the full usage of ocean wind energy for cargo ships, an innovative type of ship propulsion-assisted wing sail is proposed in this paper. The propulsion efficiency of this new wing sail can be increased by enlarging its area in both the transverse and vertical directions in good weather conditions, and it can be folded up automatically in poor weather conditions, improving the sailing safety of the ship. The sail parameters relating to the gaps and rotation angles between different parts of the wing sail are compared, and the values giving the best aerodynamic performance are identified using CFD simulation technology. The results for the lift and drag coefficients for the new wing sail at different attack angles are also compared with those of traditional aerofoil sails, including an arc-shaped rigid sail and a variable-camber sail proposed in 2015. From the viewpoint of the sailing performance of the vessel, our results demonstrate that this new type of wing sail has good aerodynamic performance and can reduce fuel costs for commercial vessels.

Dynamic Behaviour of a Free Hanging Vertical Pipe Forced to Oscillate at the Top

2020 ◽  
Author(s):  
L. P. A. Sales ◽  
C. C. O. Trigo ◽  
L. C. Sevillano ◽  
C. K. Morooka
Keyword(s):  
Laboratory Experiments ◽  
Dynamic Behaviour ◽  
Optical Measurement ◽  
Small Diameter ◽  
Vertical Pipe ◽  
Pipe Length ◽  
Pipe Model ◽  
Diameter Pipe ◽  
Out Of Plane ◽  
As Stress

Abstract Vertical pipe configuration happens in subsea well re-entry operations for wellbore drilling, subsea equipment installations, deepwater intake risers, among other scenarios, usually by hanging the marine riser at the top from a platform or ship. The simple operational configuration justifies its wide application; however, there are some drawbacks such as stress concentration, fatigue, among other issues. The purpose of this study is to contribute for the overcoming of those problems by improving the understanding of hanging risers through investigations of a vertical pipe forced to oscillate horizontally at the top. For this purpose, laboratory experiments with small diameter pipe model have been developed with oscillatory motions applied at the top termination through a mechanical device. Displacements over time and along the pipe length were measured by an optical measurement system. In the present study, a numerical scheme has been implemented for simulations to support evaluations of the experimental results. A vertical pipe response depends on several parameters, such as pipe overall length, frequency and amplitude of oscillation itself, among others. Due to existing relative velocity between the oscillating pipe and the water surrounding it, vortex shedding occurs along the pipe length which influences riser motion behaviour. The results from experiment and numerical simulations bring important insights for describing and understanding oscillatory vertical pipe behaviour, in the plane and the out of plane of the forced top oscillation. The obtained results provide a further step toward the modelling of Vortex-Induced Vibration (VIV) in marine risers, aiming to contribute to relevant technological advancements.

Flight Speed and Directional Responses to Wind by Migrating Canada Geese

The Auk ◽  
1984 ◽  
Vol 101 (2) ◽  
pp. 342-348 ◽  
Author(s):  
Michael L. Wege ◽  
Dennis G. Raveling
Keyword(s):  
Metabolic Rate ◽  
Wind Direction ◽  
Time Of Flight ◽  
Weather Conditions ◽  
Canada Geese ◽  
Cost Of Transport ◽  
Wind Drift ◽  
Visual Reference ◽  
The Cost ◽  
Goal Direction

Abstract We monitored headings, flight speeds, and time of flight of nine transmittertagged giant Canada geese (Branta canadensis maxima) during 10 different autumn migration flights during which data on wind directions and speeds were also available. Destination of these individuals was known because of previous observations of the same birds. This enabled us to evaluate their headings with respect to wind drift. As the magnitude of the following component of the wind increased, air speeds of migrating geese declined while ground speeds were not significantly changed. Therefore, the cost of transport over the ground, and probably metabolic rate, were minimized. Headings of migrant geese varied systematically and significantly with wind direction, but track directions did not deviate significantly from the goal direction. Thus, the geese compensated for wind drift. Visual reference to landmarks may have been the cue used to correct for drift, as weather conditions were such that geese could see the ground.

scholarly journals Modeling wind drift and evaporation losses during sprinkler irrigation in arid areas (case of Touggourt - Algeria)

2022 ◽  
Author(s):  
Sofiane Gheriani ◽  
Noureddine MEZA ◽  
Djamel BOUTOUTAOU
Keyword(s):  
Mean Squared Error ◽  
Sprinkler Irrigation ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Coefficient Of Determination ◽  
Irrigation Performance ◽  
Water Losses ◽  
Wind Drift ◽  
Evaporation Losses ◽  
Complex Indicators

Abstract In recent years, agriculture development in South-eastern Algeria progressed rapidly which increased the demand for agricultural products. Given that this region is characterized by hard agro-climatic conditions, irrigation seems to be a necessary factor for ensuring optimal development and high agricultural production. Like many irrigation technics widely used, sprinkler irrigation performance was considerably affected by these conditions, mainly evaporation, which causes water losses. This study aims to propose an adequate mathematical model predicting wind drift and evaporation losses under different weather conditions resume by the complex indicator of climatic intensity (ɸ). Results showed that complex indicators of climatic intensity, were significant factors affecting the wind drift and evaporation losses, puissance relationship between wind drift and evaporation losses, and complex indicators of climatic intensity, obtained model are adopted can be useful tools in the determination of the overall losses in terms of environmental conditions (air temperature, relative humidity, and wind speed). Totally 25 measure samples were used for training the model, and 15 measure samples for testing and validation of the model. The developed model for the WDEL modeling shows high good performance with a coefficient of determination (R2) = 0.808, mean squared error (RMSE) = 3.39%, and Mean Absolute Error MAE = 8.41%.

Numerical Simulation on Vortex-Induced Vibration of an Elastically Mounted Circular Cylinder With Two Degrees-of-Freedom

2011 ◽  
Author(s):  
Zhiyong Huang ◽  
Carl M. Larsen
Keyword(s):  
Numerical Simulation ◽  
Circular Cylinder ◽  
Degrees Of Freedom ◽  
Cross Flow ◽  
Flexible Beam ◽  
Vortex Induced Vibration ◽  
Two Degrees Of Freedom ◽  
Drag Forces ◽  
Strip Theory ◽  
Lift And Drag

A two-dimensional numerical simulation is applied to study the forces and responses associated with vortex-induced vibration of an elastically mounted circular cylinder with two degrees-of-freedom, i.e. the cylinder vibrates in in-line and cross-flow directions. This work could be regarded as a first step to carry out the prediction of vortex-induced-vibration responses of a long flexible beam with a number of two-dimension sections along the spanwise based on strip theory. A direct comparison has been made between the numerical results and measured data from the experiment by Jauvtis and Williamson in 2004. The peak cross flow response reaches 1.28 diameters in the present simulations. The profiles between the displacement and transverse force are found to have a good match with the experimental results, and a typical figure of ‘8’ trace is observed between the lift and drag forces in the initial and super-upper branches. Two typical in-line wake structures SS mode and AS mode are well reproduced in the low reduced velocity range. The newly discovered wake pattern 2T mode corresponds to the super-upper branch is also recaptured. Comparison shows that most features of the experiment can be reproduced by the present numerical model, and this model can be regarded a robust tool to investigate the responses, forces and the basic mechanics of vortex induced vibrations of an elastically mounted cylinder with two degrees-of-freedom.

A Replica Technique for the Inside Surfaces of Small Diameter Pipes and Tubes

1967 ◽  
Vol 25 ◽  
pp. 352-353
Author(s):  
T. G. Gregory
Keyword(s):  
Polyvinyl Chloride ◽  
Small Diameter ◽  
Replica Technique ◽  
Tube Size ◽  
Inside Diameter ◽  
Complete Inspection ◽  
Operating Limits

A nondestructive replica technique permitting complete inspection of bore surfaces having an inside diameter from 0.050 inch to 0.500 inch is described. Replicas are thermally formed on the outside surface of plastic tubing inflated in the bore of the sample being studied. This technique provides a new medium for inspection of bores that are too small or otherwise beyond the operating limits of conventional inspection methods.Bore replicas may be prepared by sliding a length of plastic tubing completely through the bore to be studied as shown in Figure 1. Polyvinyl chloride tubing suitable for this replica process is commercially available in sizes from 0.037- to 0.500-inch diameter. A tube size slightly smaller than the bore to be replicated should be used to facilitate insertion of the plastic replica blank into the bore.

Structural Organization and Distribution of Fiber Types in Extraocular Muscles of Cats

1972 ◽  
Vol 30 ◽  
pp. 34-35
Author(s):  
Asish C. Nag ◽  
Lee D. Peachey
Keyword(s):  
Fiber Type ◽  
Light And Electron Microscopy ◽  
Small Diameter ◽  
Extraocular Muscles ◽  
Fiber Types ◽  
Distinctive Features ◽  
Superior Rectus ◽  
Adult Cats ◽  
Different Diameters ◽  
Orbital Region

Cat extraocular muscles consist of two regions: orbital, and global. The orbital region contains predominantly small diameter fibers, while the global region contains a variety of fibers of different diameters. The differences in ultrastructural features among these muscle fibers indicate that the extraocular muscles of cats contain at least five structurally distinguishable types of fibers.Superior rectus muscles were studied by light and electron microscopy, mapping the distribution of each fiber type with its distinctive features. A mixture of 4% paraformaldehyde and 4% glutaraldehyde was perfused through the carotid arteries of anesthetized adult cats and applied locally to exposed superior rectus muscles during the perfusion.

Prospects for convergent beam electron diffraction with a 200kV cold field-emission transmission electron microscope

1991 ◽  
Vol 49 ◽  
pp. 466-467
Author(s):  
J W Steeds ◽  
R Vincent
Keyword(s):  
Field Emission ◽  
High Performance ◽  
Small Diameter ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Good Crystallinity ◽  
Special Modification ◽  
Convergent Beam

We review the analytical powers which will become more widely available as medium voltage (200-300kV) TEMs with facilities for CBED on a nanometre scale come onto the market. Of course, high performance cold field emission STEMs have now been in operation for about twenty years, but it is only in relatively few laboratories that special modification has permitted the performance of CBED experiments. Most notable amongst these pioneering projects is the work in Arizona by Cowley and Spence and, more recently, that in Cambridge by Rodenburg and McMullan.There are a large number of potential advantages of a high intensity, small diameter, focussed probe. We discuss first the advantages for probes larger than the projected unit cell of the crystal under investigation. In this situation we are able to perform CBED on local regions of good crystallinity. Zone axis patterns often contain information which is very sensitive to thickness changes as small as 5nm. In conventional CBED, with a lOnm source, it is very likely that the information will be degraded by thickness averaging within the illuminated area.

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