ENERGY EXCHANGE IN A CORN CANOPY

1975 ◽  
Vol 55 (3) ◽  
pp. 691-704
Author(s):  
J. H. McCAUGHEY ◽  
J. A. DAVIES
Keyword(s):  
Sweet Corn ◽  
Exponential Model ◽  
Source Strength ◽  
Net Radiation ◽  
Sources And Sinks ◽  
Transfer Equations ◽  
Solar Noon ◽  
Turbulent Transfer Coefficient ◽  
Source Sink ◽  
The Vertical Distribution

Results from a study of the energy balance within a sweet corn (Zea mays L.) canopy are presented. The downward depletion of hourly net radiation in the canopy is described by a modified exponential model. Temperature, humidity and energy source/sink profiles are discussed at two crop stages. The use of one-dimensional mass transfer equations for sensible and latent heat was satisfactory only under certain conditions of windspeed and wind direction. The vertical distribution of energy sources and sinks changed as the canopy aged. During both sample periods, evaporation was the principal energy user, and its source strength showed two maxima which were most pronounced around solar noon. As the attenuation of net radiation increased after solar noon, the source strength for evaporation returned to a single maximum. The diffusion for all levels in the canopy was turblent. Turblence did not decay exponentially in this canopy. Profiles of the computed turbulent transfer coefficient showed local increases at the base and the center of the canopy probably as a result of increased thermal convection.

scholarly journals Source capacity during flowering affects grain yield of amaranth (Amaranthus sp.)

2013 ◽  
Vol 59 (No. 10) ◽  
pp. 472-477 ◽  
Author(s):  
B. Roitner-Schobesberger ◽  
Kaul H-P
Keyword(s):  
Grain Yield ◽  
Dry Matter ◽  
Field Experiments ◽  
Growth Conditions ◽  
Yield Reduction ◽  
Sources And Sinks ◽  
Yield Level ◽  
Eastern Austria ◽  
Source Sink ◽  
Yield Formation

Amaranth is a promising C4-crop. However, for a wider spread of the crop a better understanding of factors that are influencing yield formation is crucial for optimizing the plant phenotype and enhancing yield. The present study wanted to clarify the effects of assimilate sources and sinks on yield formation by artificially altering source or sink size. Field experiments were conducted in Eastern Austria during three years with three genotypes, applying source-sink manipulation treatments at mid flowering (control, 50% of inflorescence removed, 50% or 100% of leaves removed). At maturity we measured shoot, inflorescence and grain dry matter, thousand kernel mass and number of seeds per plant. An average grain yield level of about 3.5 t/ha dry matter on control plots indicated favorable growth conditions for amaranth in general. The removal of all leaves had a strong detrimental effect on all parameters, but severity of yield reduction due to defoliation differed between genotypes, ranging from –49% to –73%. Contrastingly, 50% flower reduction did not have any significant effects. Also with 50% defoliation no significant yield reduction was observed. We conclude that source strength of amaranth during flowering is more yield limiting than its sink capacity.

scholarly journals A boundary-integral method applied to water coning in oil reservoirs

1991 ◽  
Vol 32 (3) ◽  
pp. 261-283 ◽  
Author(s):  
S. K. Lucas ◽  
J. R. Blake ◽  
A. Kucera
Keyword(s):  
Boundary Integral ◽  
Oil Reservoirs ◽  
Boundary Integral Method ◽  
Oil Well ◽  
Interface Shape ◽  
Pumping Rate ◽  
Sources And Sinks ◽  
Oil Water ◽  
Source Sink ◽  
Actual Geometry

AbstractIn oil reservoirs, the less-dense oil often lies over a layer of water. When pumping begins, the oil-water interface rises near the well, due to the suction pressures associated with the well. A boundary-integral formulation is used to predict the steady interface shape, when the oil well is approximated by a series of sources and sinks or a line sink, to simulate the actual geometry of the oil well. It is found that there is a critical pumping rate, above which the water enters the oil well. The critical interface shape is a cusp. Efforts to suppress the cone by using source/sink combinations are presented.

Source–sink turbulence in a rotating stratified fluid

1995 ◽  
Vol 298 ◽  
pp. 81-112 ◽  
Author(s):  
P. F. Linden ◽  
B. M. Boubnov ◽  
S. B. Dalziel
Keyword(s):  
Large Scale ◽  
Baroclinic Instability ◽  
Stratified Fluid ◽  
Energy Cascade ◽  
Density Level ◽  
Sources And Sinks ◽  
Inverse Cascade ◽  
Inverse Energy Cascade ◽  
Flow Domain ◽  
Source Sink

In a recent paper Boubnov, Dalziel & Linden (1994) described the response of a stratified fluid to forcing produced by an array of sources and sinks. The sources and sinks were located in a horizontal plane and the flow from the sources was directed horizontally so that fluid was withdrawn from, and re-injected at, its own density level. As a result vertical vorticity was imparted to the fluid with a minimum of vertical mixing. It was found that when the stratification was strong enough to suppress vertical motions an inverse energy cascade was observed leading to the establishment of a large-scale circulation in the fluid. Those experiments were restricted to eight source-sink pairs. The present paper extends this work in two ways. First, up to forty source-sink pairs are used to force the flow, thereby producing a much wider separation of scales between the forcing and the flow domain. An inverse cascade is again found, but in this case the energy transfer to large scales is more rapid. The basic pattern of the large-scale flow is independent of the number of sources but the detailed structure depends on the energy input scale. Second, the effects of rotation about a vertical axis are investigated. It is found that when the Rossby deformation radius exceeds the size of the flow domain, the inverse energy cascade still occurs. However, for smaller values of the deformation scale, which in these experiments are comparable to or smaller than the forcing scale, the inverse cascade is altered by baroclinic instability. When flow structures develop on a scale larger than the deformation scale, usually by the merging of vortices of like sign, these structures are observed to split into smaller vortices of a scale comparable to the deformation scale. The flow appears to evolve with a balance between an anticascade produced by the two-dimensionality of the flow and a cascade due to baroclinic instability. For Rossby radii much smaller than the domain size the flow evolves into finite clumps of vorticity and an asymmetry between anticyclones and cyclones develops. A predominance of coherent anticyclones is observed, and the cyclonic vorticity is contained in more diffuse structures.

Notes on the Linear Theory of Incompressible Flow Round Symmetrical Swept-Back Wings at Zero Lift

1949 ◽  
Vol 1 (1) ◽  
pp. 101-122 ◽  
Author(s):  
F. Ursell
Keyword(s):  
Incompressible Fluid ◽  
Recent Work ◽  
Linear Theory ◽  
Incompressible Flow ◽  
Point Of View ◽  
Source Strength ◽  
Small Thickness ◽  
Sources And Sinks ◽  
Wing Profile ◽  
Flow Round

SummaryIn much of the recent work on the flow of an incompressible fluid past a swept-back symmetrical wing of small thickness at zero incidence it has been assumed that the disturbance introduced by the wing can be represented by means of a distribution of sources and sinks over the centre plane of the wing, the source strength being determined from the equation of the wing profile. It was found by Neumark that on the wing itself this procedure was liable to lead to serious errors. Neumark and Kuchemann studied certain special types of wings for which they were able to find the correct value of the pressure at the surface by evaluation of the pressure at points off the wing and continuity considerations. This process is rather cumbersome; it may therefore be convenient to regard the problem from a rather different point of view.

Quantitative carbon distribution in clonal plants of white clover (Trifolium repens): source-sink relationships during undisturbed growth

1991 ◽  
Vol 116 (2) ◽  
pp. 229-238 ◽  
Author(s):  
D. F. Chapman ◽  
M. J. Robson ◽  
R. W. Snaydon
Keyword(s):  
White Clover ◽  
Parental Support ◽  
Clonal Plants ◽  
Unit Weight ◽  
Sink Strength ◽  
Sources And Sinks ◽  
Mature Leaves ◽  
Specific Source ◽  
Source Sink ◽  
Subtending Leaves

SUMMARYThe assimilation and distribution of carbon in laterally spreading white clover plants was quantified in a controlled environment using CO2 exchange rate measurements and 14C as a tracer. Plants were restricted to three mature leaves on the main stolon apex, and the movement of 14C from these leaves (and one immature, but carbon-exporting, leaf) to meristematic zones throughout the plant was determined by detailed plant dissection.Sinks throughout the plant drew small to moderate proportions (typically 1–8%) of the 14C exported by all mature leaves. The three mature leaves displayed similar export patterns, and no specific source-sink relationships involving any of these leaves were observed. However, 14C exported by the developing leaf moved predominantly to the main stolon apex, and to adjacent young stolon tissue. Estimated respiratory losses over 24 h accounted for 40–49% of the 14C fixed. Of the total amount of C exported by all four leaves and utilized in new growth or reserve storage, 22% moved to the main stolon apex, 16% to stolon tissue of the main stolon, 34% to adventitious roots on the main stolon (most of which was utilized in older, nodulated roots) and 29% to branches. The apex received the greatest amount of C/unit weight, reflecting its high sink activity, its proximity to the source leaves and, possibly, apical dominance. Subtending leaves provided 46–51% of the C utilized by young branches. Older branches continued to import significant quantities of C from parent stolon leaves despite having their own C sources, though parental support for branches was seen to decrease as branches aged, when the quantity of C they imported was expressed as a function of their weight.Relative sink strength and distance between sources and sinks contributed to the observed patterns of C distribution. No apparent restriction on C movement was imposed by the vascular architecture of stolons.

scholarly journals Technical note: Facilitating the use of low-cost methane (CH<sub>4</sub>) sensors in flux chambers – calibration, data processing, and an open source make-it-yourself logger

2020 ◽  
Author(s):  
David Bastviken ◽  
Jonatan Nygren ◽  
Jonathan Schenk ◽  
Roser Parellada Massana ◽  
Nguyen Thanh Duc
Keyword(s):  
Data Processing ◽  
Greenhouse Gas ◽  
Low Cost ◽  
Technical Note ◽  
Calibration Data ◽  
Sources And Sinks ◽  
Major Bottleneck ◽  
Flux Chambers ◽  
Carbon Dioxide Co2 ◽  
Source Sink

Abstract. A major bottleneck regarding the efforts to better quantify greenhouse gas fluxes, map sources and sinks, and understand flux regulation, is the shortage of low-cost and accurate-enough measurement methods. The studies of methane (CH4) – a long-lived greenhouse gas increasing rapidly but irregularly in the atmosphere for unclear reasons, and with poorly understood source-sink attribution – suffer from such method limitations. This study present new calibration and data processing approaches for use of a low-cost CH4 sensor in flux chambers. Results show that the change in relative CH4 levels can be determined at rather high accuracy in the 2–700 ppm range, with modest efforts of collecting reference samples in situ, and without continuous access to expensive reference instruments. These results open for more affordable and time-effective measurements of CH4 in flux chambers. To facilitate such measurements, we also provide a description for building and using an Arduino logger for CH4, carbon dioxide (CO2), humidity, and temperature.

Consequences of phloem pathway unloading/reloading on equilibrium flows between source and sink: a modelling approach

2017 ◽  
Vol 44 (5) ◽  
pp. 507 ◽  
Author(s):  
Peter E. H. Minchin ◽  
André Lacointe
Keyword(s):  
Large Fraction ◽  
Phloem Transport ◽  
Solute Concentration ◽  
Sources And Sinks ◽  
Pressure Profiles ◽  
Flow Mechanisms ◽  
Source Sink ◽  
Pressure Driven Flow ◽  
Source And Sink ◽  
Modelling Approach

It is now accepted that the transport phloem, linking major sources and sinks, is leaky, and this leakage can be considerable. Hence for phloem transport to function over the long distances observed, a large fraction of this unloaded photosynthate must be reloaded. A fraction of this unloaded solute is used to maintain tissues surrounding the phloem, as well as being stored. Also, pathway unloading/reloading acts as a short-term buffer to source and sink changes. In this work we present the first attempt to include both pathway unloading and reloading of carbohydrate in the modelling of pressure driven flow to determine if this has any significant effect upon source–sink dynamics. Our results indicated that the flow does not follow Poiseuille dynamics, and that pathway unloading alters the solute concentration and hydrostatic pressure profiles. Hence, measurement of either of these without considerable other detail tells us very little about the flow mechanisms. With adequate reloading along the pathway, the effects of pathway unloading can completely compensate for, making the entire system look like one with no pathway unloading.

scholarly journals Net radiation within a canopy of sweet corn during drought

1981 ◽  
Vol 23 ◽  
pp. 143-150 ◽  
Author(s):  
R.B. Campbell ◽  
D.C. Reicosky ◽  
C.W. Doty
Keyword(s):  
Sweet Corn ◽  
Net Radiation
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