scholarly journals The measurement of sand storms

1938 ◽  
Vol 167 (929) ◽  
pp. 282-291 ◽  
Keyword(s):  
Velocity Distribution ◽  
Ground Surface ◽  
Surface Irregularity ◽  
Surface Drag ◽  
Sand Surface ◽  
Air Density ◽  
Open Country ◽  
Sand Movement ◽  
Drag Velocity ◽  
Made In

In earlier papers (Bagnold 1936, 1937 a ) a description was given of experiments made in a wind tunnel 1 ft. sq. in cross-section to examine the conditions of wind and ground surface governing the mass flow q of sand across open country. It was found that: ( a ) The sand movement over a loose sand surface profoundly modifies the vertical velocity distribution of the wind, and that Prandtl's expression for the velocity distribution over a roughly surface of immobile grains v = 5.75 V log 30 z / k (1) (where the drag velocity V = √( T/p ), z is the height of measurement above the surface, k is the height above the surface at which v is zero―a height of the order of 1/30 of the dimension of the surface irregularity, i. e . the grain diameter, T is the surface drag and p the air density)

Ground reaction force and hoof deceleration patterns on two different surfaces at the trot

2006 ◽  
Vol 3 (4) ◽  
pp. 209-216 ◽  
Author(s):  
Pia Gustås ◽  
Christopher Johnston ◽  
Stig Drevemo
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
Force Plate ◽  
Ground Surface ◽  
Ground Reaction Forces ◽  
Triaxial Accelerometer ◽  
Loading Rates ◽  
Sand Surface ◽  
Reaction Forces ◽  
Force Data

AbstractThe objective of the present study was to compare the hoof deceleration and ground reaction forces following impact on two different surfaces. Seven unshod Standardbreds were trotted by hand at 3.0–5.7 m s− 1 over a force plate covered by either of the two surfaces, sandpaper or a 1 cm layer of sand. Impact deceleration data were recorded from one triaxial accelerometer mounted on the fore- and hind hooves, respectively. Ground reaction force data were obtained synchronously from a force plate, sampled at 4.8 kHz. The differences between the two surfaces were studied by analysing representative deceleration and force variables for individual horses. The maximum horizontal peak deceleration and the loading rates of the vertical and the horizontal forces were significantly higher on sandpaper compared with the sand surface (P < 0.001). In addition, the initial vertical deceleration was significantly higher on sandpaper in the forelimb (P < 0.001). In conclusion, it was shown that the different qualities of the ground surface result in differences in the hoof-braking pattern, which may be of great importance for the strength of the distal horse limb also at slow speeds.

Detection of Non-Metallic Cords Using Synthetic Aperture Acoustic Imaging

2012 ◽  
Author(s):  
John A. Judge ◽  
Joseph F. Vignola ◽  
Aldo A. J. Glean ◽  
Teresa J. Ryan ◽  
Chelsea E. Good ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Ground Surface ◽  
Acoustic Imaging ◽  
Acoustic Energy ◽  
Synthetic Aperture ◽  
Two Dimensional ◽  
Two Dimensional Image ◽  
Imaging Approach ◽  
Different Diameters ◽  
Made In

Synthetic aperture acoustic (SAA) imaging is a technique for remotely obtaining information about the location, geometry, and mechanical properties of objects based on the way they scatter incident acoustic energy. Results are presented for an experimental investigation of the use of SAA imaging to detect non-metallic cords of different sizes laid in various configurations on the ground surface in an outdoor urban environment. Interest in this application of SAA stems from the fact that non-metallic cords are not readily detectable with synthetic aperture radar (SAR) and that the SAA imaging approach represents a relatively inexpensive alternative or supplement to SAR. The measurement system is comprised of a mobile acoustic transceiver (a speaker and microphone) that broadcasts a burst chirp with a bandwidth of 2–15 kHz. The recorded signal is used to form a two-dimensional image of the distribution of acoustic scatterers within the scene. For this study, five different diameters (2–15mm) of nylon cord laid on the ground were imaged in different configurations. These measurements were made in the presence of urban ambient noise of varying levels. The goal of this study was to identify the effect of environmental noise and other parameters on detectability. The results demonstrate that non-metallic cords can be detected acoustically if the angle to the transceiver path is sufficiently small.

XXIV.—The Scattering of Light

1914 ◽  
Vol 33 ◽  
pp. 264-281
Author(s):  
James Robert Milne
Keyword(s):  
Light Scattering ◽  
Systematic Study ◽  
Ground Surface ◽  
Single Layer ◽  
The Other ◽  
Total Emission ◽  
Special Apparatus ◽  
The Many ◽  
The One ◽  
Made In

SummaryThe present paper describes a number of experiments made in connection with Christiansen's experiment in which a beam of light is passed through a transparent insoluble powder immersed in a liquid, with the result that light of the particular colour for which the indices of powder and liquid are the same passes unaffected, while light of all other colours is scattered. In this communication only the simplest case of the above is dealt with, that, namely, in which a flat piece of glass, ground on one side, takes the place of the powder, the rugosities of the ground surface representing a single layer of grains, and air takes the place of the liquid. In such a case there is, of course, no colour of light for which the indices of solid and liquid are alike, and indeed it was found that the colour of the light made very little difference to the results. On the other hand, however, it soon became apparent that different ways of grinding the glass surface led to very different effects. Accordingly, as no previous work appears to have been done in this field, and as it seemed a promising one, it was decided to make a systematic study of the various cases. Each specimen of glass employed was photomicrographed, and had its polar light distribution measured by a photometer. Two methods of characterising the particular scattering power of a screen soon suggested themselves and have been formally defined—the one connected with the Angle of Maximum Total Emission, and the other with the Equivalent Cavity.It is hoped to continue the investigation not only on the above lines, but also in the direction of ascertaining the effect of a number of plates, i.e. of successive layers of light-scattering particles; and in investigating the polarisation effects, which some rough preliminary experiments have shown to be marked.I am glad of this opportunity of acknowledging the help I have received from the Trustees of the Carnegie Trust in the form of grants for the construction of the special apparatus necessary; and desire to tender my grateful thanks to Professor MacGregor for the many facilities for carrying on the work which he kindly placed at my disposal.

Evidence for nondiffusive transport of 86Rn in the ground and a new physical model for the transport

Geophysics ◽  
1982 ◽  
Vol 47 (10) ◽  
pp. 1444-1452 ◽  
Author(s):  
Krister Kristiansson ◽  
Lennart Malmqvist
Keyword(s):  
Diffusion Length ◽  
Ground Surface ◽  
Constant Depth ◽  
Physical Conditions ◽  
Transport Length ◽  
Carrier Mechanism ◽  
Flow Transport ◽  
And Migration ◽  
Radon Measurements ◽  
Made In

Concentration of radon has been measured in the soil near the ground surface with solid‐state, nuclear track detectors with the inverted cup technique. Measurements were made in the overburden at depth intervals 0.1–0.7 m, at 0.1–6 m, and at a constant depth of 0.2 m, in a narrow rectangular matrix. The results disagree with the hypothesis that radon concentration only depends upon local production and migration by diffusion with a diffusion length of about 1 m. A transport length of 0.1–0.2 m is observed near the ground surface and the transport is dominated by a flow component. Radon measurements in the ground surface over the Laisvall lead mine have given evidence of radon transport through rock exceeding a distance of 100 m, which is possible only if the migration is a flow transport with a characteristic transport length larger than about 10 m/day. To explain the radon transport in the overburden and through the rock with a common transport system, the existence of a general upward flow of geo‐gas is proposed. This geo‐gas works as a carrier mechanism for radon. The physical conditions for the existence of a flow transport of radon are discussed.

Design of Cascades for Incompressible Plane Potential Flows With Prescribed Velocity Distribution

1971 ◽  
Vol 93 (3) ◽  
pp. 321-331 ◽  
Author(s):  
W. Schwering
Keyword(s):  
Velocity Distribution ◽  
Surface Velocity ◽  
Two Dimensional ◽  
Blade Profile ◽  
Method Of Calculation ◽  
Potential Flows ◽  
Loss Coefficients ◽  
Optimum Velocity ◽  
Made In

A method of calculation in designing two-dimensional cascades with given velocity distribution is described. An iterative method of the solution for the integral equation to determine the coordinate function for the blade profile is presented. A parametric formulation for the surface velocity distribution is developed. Some design examples for deceleration cascades with given flow angles and prescribed velocity distribution are discussed. Calculations of the boundary layers along the surfaces of the airfoil and cascade loss coefficients are made in order to obtain information on the quality of cascades designed by this method. Proceeding from the results of boundary layer calculations, it should be possible to further improve the parametric formulation for the surface velocity distribution and in this way prescribe better or even “optimum” velocity distributions.

scholarly journals A Steady Flow of The Viscous Compressible Liquid in Vertical Pipe

2021 ◽  
Vol 89 (2) ◽  
pp. 150-159
Author(s):  
Farman Mamedov ◽  
Nazire Memmedzade
Keyword(s):  
Velocity Distribution ◽  
Cross Section ◽  
Stokes Equations ◽  
Ground Surface ◽  
Ground Level ◽  
Compressible Liquid ◽  
Navier Stokes ◽  
Deep Zone ◽  
Vertical Pipe ◽  
Emden Equation

In the study of the flow of gas-liquid mixture over circular vertical pipe rising from the deep zone to ground level, it is observed that, the velocity on surface of tube is much more than in the center of flow. Such a picture is seen also in the water filtration process in sands ordering from high permeability zone to lower. Same phenomena occur in transportation of the water carbon nana-tubes. In order to predict behavior of those processes in this paper, we have studied the compressible liquid flow over the circular vertical pipe ordered from the deep zone to the ground surface for some concrete inlet and outlet regimes of the pipe. The Navier-Stokes equations system as a model of study. For certain inlet and outlet regimes of the flow splitting the equation into the cross section and axes variables, the pressure and velocity distribution are found. The Lane-Emden equation arises for determining the pipe cross section velocity distribution, which is also justified by our calculations on the used model.

scholarly journals A study of atmospheric boundary layer characteristics with ground snow cover - numerical method

MAUSAM ◽  
2021 ◽  
Vol 48 (3) ◽  
pp. 397-404
Author(s):  
N. RAMANATHAN ◽  
K. SRINIVASAN
Keyword(s):  
Snow Cover ◽  
Mesoscale Model ◽  
Potential Temperature ◽  
Specific Humidity ◽  
Wave Radiation ◽  
Surface Drag ◽  
Dimensional Version ◽  
Atmospheric Variables ◽  
Made In

ABSTRACT. A one-dimensional version of a mesoscale model was used to simulate the atmospheric variables over ground snow cover after incorporating suitable modifications. Modifications to include the effect of cloud on shortwave and long wave radiation were also made in the model. The model takes into account both the heat balance at the snow surface and at various layers of the snow pack and calculates the melt rate in situ. Srinagar (Jammu & Kashmir) winter data was used for the simulations. The diurnal variation of snowmelt rate and other atmospheric variables were simulated simultaneously by the model. Melt rate values were verified with the values obtained from standard empirical formula. The model-simulated profiles of potential temperature, specific humidity and wind speed were found to be in reasonable agreement with available observations. The results were found to be insensitive to changes in surface drag coefficients.      

scholarly journals On the meteorology of the Lake District of Cumberland and Westmoreland, with a continuation of the results of experiments on the fall of rain at various heights, up to 3166 feet above the sea-level

1851 ◽  
Vol 5 ◽  
pp. 952-953
Keyword(s):  
Sea Level ◽  
Lake District ◽  
The Past ◽  
Equable Climate ◽  
Open Country ◽  
Made In

In this communication are given the results of the observations of the quantity of rain which has fallen during the year 1849 at twenty stations in the valleys, and six mountain statious, varying in altitude above the sea from 500 feet to 3166 feet. There is also given a table of the temperature at Seathwaite in Borrowdale during the year 1849. With reference to the mountain gauges, the author observes that, on the whole, the results are similar to those of the three preceding years, but, as might be looked for in a dry year like the past, the quantities of rain deposited at the various stations are more nearly equal than usual. With respect to the temperature, he observes that the statement he made in his last communication, that “the inhabitants of the Lake District valleys enjoyed a milder and more equable climate than the residents in the open country, and particularly in the winter months,” is confirmed by the thermometrical results of the present winter (1849-50).

scholarly journals Effect of Sand Relative Density on Response of a Laterally Loaded Pile and Sand Deformation

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Bingxiang Yuan ◽  
Rui Chen ◽  
Jun Teng ◽  
Yixian Wang ◽  
Wenwu Chen ◽  
...  
Keyword(s):  
Relative Density ◽  
Ground Surface ◽  
Scale Model ◽  
Loose Sand ◽  
Dense Sand ◽  
Laterally Loaded Pile ◽  
Toyoura Sand ◽  
Sand Movement ◽  
Sand Particles ◽  
Laterally Loaded

Two scale-model tests were separately conducted in standard Toyoura sand with relative density of 50% and 80%. The effect of sand relative density on pile-soil interaction was investigated through the response of a laterally loaded pile and the sand movement around the pile. At a displacement of 3.6 mm of the loading point, the applied loads in loose and dense sand were 4.775 N and 21.025 N, respectively, and the maximum moment and soil resistance of the pile in dense sand were over 4 times those in loose sand. However, the deflection of the pile in dense sand was less than that in loose sand; additionally, the depth of zero deflection in dense sand was also less than that in loose sand. At the same time, the maximum displacements of loose sand in the vertical profile and ground surface were over 1.5 times those of dense sand. These characteristics occurred because the relative stiffness ratio of soil and pile increased as the relative density increased, which caused the behavior of the pile in dense sand to be elastic rather than rigid. In addition, the compacted sand particles did not move as easily as the loose sand particles.

Underwater Observations on Tracks of Dredges and Trawls and Some Effects of Dredging on a Scallop Ground

1973 ◽  
Vol 30 (2) ◽  
pp. 173-180 ◽  
Author(s):  
J. F. Caddy
Keyword(s):  
Bottom Sediments ◽  
Fishing Gear ◽  
Fine Sediments ◽  
Sand Surface ◽  
Order Of Magnitude ◽  
Harvesting Efficiency ◽  
Made In

Tracks of three types of fishing gear in bottom sediments were observed from a submersible in Chaleur Bay (Gulf of St. Lawrence). Tracks left by past otter trawling activities covered at least 3% of the bottom by area and were considered to have been made by trawl doors.Shallow tracks made by inshore and offshore scallop dredges during the course of the study could be distinguished from each other and from trawl tracks.Scallop dredging lifts fine sediments into suspension, buries gravel below the sand surface, and overturns large rocks embedded in the sediment, appreciably roughening the bottom. The inshore Alberton dredge is inefficient, dumping its contents back onto bottom at intervals during the tow.Dredging causes appreciable lethal and sublethal damage to scallops left in the track, this damage being greatest on rough bottom. Incidental mortalities to scallops with an offshore dredge of at least 13–17% per tow are of the same order of magnitude as estimates of harvesting efficiency made in earlier studies.Predatory fish and crabs were attracted to the dredge tracks within 1 hr of fishing and were observed in the tracks at densities 3–30 times those observed outside the tracks.

Sign in / Sign up

Export Citation Format

Share Document