Colonization by Lotic Macroinvertebrates: A Review of Processes and Patterns

1992 ◽  
Vol 49 (3) ◽  
pp. 617-628 ◽  
Author(s):  
Rosemary J. Mackay
Keyword(s):  
Large Scale ◽  
Trophic Ecology ◽  
Experimental Studies ◽  
Life Cycles ◽  
Small Scale ◽  
Stream Communities ◽  
Stream Community ◽  
Lotic Habitats ◽  
Ecological Patterns ◽  
Filter Feeders

Ways in which invertebrates colonize lotic habitats are reviewed, tracing patterns in behaviour, trophic ecology, and life history that could lead to predictions concerning resilience of stream communities after disturbance. Patterns are described for small-scale experimental studies using introduced or natural substrates, for large-scale observations of new or rewatered channels, for rivers recovering from pollution, and for unstable rivers with fluctuating discharge. Colonization depends on invertebrate mobility (drift, swimming, crawling, and flight), substrate texture and associated food supplies, competition, and predation. Epilithon-browsers and filter feeders can use the resources of smooth stones; gatherers colonize as fine detritus accumulates; grazers increase as periphyton becomes established; shredders and predators tend to be late arrivals. Propagules for colonization are made more available by asynchronous and aseasonal life cycles, long oviposition periods, and refuges in the streambed or neighbouring waterbodies. Species in frequently disturbed streams benefit from these characteristics. Although disturbance may be due to stochastic factors, recovery is not due to chance. Recurring ecological patterns among early colonizers suggest that knowledge of the hydrologic regime, food resources, and dominant taxa can be used to predict the overall resilience of a stream community.

Dynamics of a Large Scale Hydraulic Capsule Pipeline System

1999 ◽  
Vol 124 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Hongliu Du ◽  
Satish S. Nair
Keyword(s):  
Large Scale ◽  
Control Method ◽  
Experimental Studies ◽  
Small Scale ◽  
Pipeline System ◽  
Centrifugal Pumps ◽  
Long Distance ◽  
Column Separation ◽  
In Series ◽  
Hydraulic Capsule Pipeline

The dynamics of a booster station, which is critical for the control of a novel, long distance, hydraulic capsule pipeline, is simulated mathematically for design studies and control of the hydraulic transients caused by the valve actuators in the system. Several modifications to the pump bypass station configuration of the booster station have been studied. With the objective of eliminating column separation and reducing flow reversals, a configuration with several centrifugal pumps connected in series, and a carefully sized air chamber is found to be a viable design. A valve control method is designed to eliminate column separation and the design results in acceptable flow reversal levels in the main pipe. The simulation results match with trends in limited experimental studies performed on a small scale experimental capsule pipeline system.

scholarly journals DIMPLE GENERATOR OF VORTEX STRUCTURES

2021 ◽  
pp. 95-102
Author(s):  
A. V. Voskobijnyk ◽  
V. M. Turick ◽  
O. A. Voskoboinyk ◽  
V. A. Voskoboinick
Keyword(s):  
Large Scale ◽  
Vortex Flow ◽  
Flat Surface ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Vortex Structures ◽  
Small Scale ◽  
Wall Pressure Fluctuations ◽  
Large Scale Vortex ◽  
Streamlined Surface

The paper presents the results of experimental studies of the space-time characteristics of the velocity and pressure field inside a hemispherical dimple on a flat surface. The features of the formation and development of vortex structures generated inside the dimple, as well as their interaction with the streamlined surface of the dimple and the boundary layer were established. Integral, spectral and correlation characteristics of the field of velocity, dynamic and wall pressure fluctuations were obtained. The velocities and directions of transfer of large-scale vortex structures and small-scale vortices inside the dimple were determined. The frequencies of rotations and ejections of large-scale vortices, the frequencies of oscillations of the vortex flow inside the dimple and self-oscillations of the vortex structures of the shear layer, their subharmonics and harmonics of higher orders were established.

INVESTIGATION INTO THE INFLUENCE OF IMPREGNATION ON PINE TIMBER COMBUSTION USING A CONE CALORIMETER AND LARGE SCALE TESTS

2011 ◽  
Vol 3 (3) ◽  
pp. 91-104 ◽  
Author(s):  
Jerzy Gałaj ◽  
Zbignev Karpovič ◽  
Waldemar Jaskółowski
Keyword(s):  
Cone Calorimeter ◽  
Large Scale ◽  
Experimental Studies ◽  
Fire Retardant ◽  
Full Scale ◽  
Lower Amount ◽  
Small Scale ◽  
Fire Retardants ◽  
Co Concentration ◽  
Piloted Ignition

Fire safety is one of the main requirements with respect to the regulations on the buildings involved into the category of human hazards. Human safety measures are applied equally to inhabitants, users, customers, spectators, etc., as well as to fire brigades taking part in the activities connected with rescue actions. Methods for emission research were applied to estimate thermo-kinetic parameters related to smoke and toxic gases. The methods fall into two types: full scale methods reflect fire conditions and small laboratory scale methods having a significantly lower degree of reflection. This paper presents the results of studies on the influence of BAK-1 and Flamasepas-2 fire retardants produced in Lithuania and applied for timber on the selected parameters of the fire environment. Experimental studies were conducted using a cone calorimeter (small scale) in the closed compartment equipped with measuring devices (full scale). The undertaken studies have demonstrated that considering some parameters, such as heat release rate (HRR), a positive effect of the lower amount of the released heat can be obtained. Unfortunately, in case of the major part of the studied parameters, including time to ignition, CO concentration and extinction parameter reflecting smokiness, worse results (shorter time, higher CO values and higher extinction coefficient) have been observed for the treated timber rather than for the non-impregnated one. The obtained results have showed combustion with piloted ignition. In case of no piloted ignition, the results were slightly different. For all studied specimens treated with fire retardants, no ignition was observed and tests were terminated following 15 minutes. CO concentration and extinction parameter (smokiness) were higher for non-impregnated timber. Full scale experiments have confirmed the above provided information; moreover, it has been found that the application of fire retardant has no significant impact on temperatures in the compartment.

Compressive Behavior of Large-Scale Hybrid FRP-Concrete-Steel Double-Skin Tubular Columns

2011 ◽  
Vol 243-249 ◽  
pp. 1138-1144 ◽  
Author(s):  
Pan Xie ◽  
T Yu ◽  
Y.L. Wong ◽  
J.G. Teng
Keyword(s):  
Large Scale ◽  
Experimental Studies ◽  
Steel Tube ◽  
Small Scale ◽  
Structural Members ◽  
Compression Tests ◽  
Tubular Columns ◽  
Compressive Response ◽  
Double Skin ◽  
Frp Tube

Hybrid FRP-concrete-steel double-skin tubular columns (DSTCs) are a new form of hybrid structural members. A hybrid DTSC consists of an inner steel tube, an outer FRP tube and a concrete infill between them. Hybrid DSTCs possess many important advantages over conventional structural members, including their excellent corrosion resistance as well as excellent ductility and seismic resistance. A large amount of research has been conducted on hybrid DSTCs, but the existing experimental studies have been limited to the testing of small-scale columns. This paper presents preliminary results from the first series of large-scale axial compression tests on hybrid DSTCs, which forms part of a larger experimental study currently under way at The Hong Kong Polytechnic University. These test results confirm the excellent axial compressive response of hybrid DSTCs as initially expected.

scholarly journals HYDRODYNAMICS UNDER LARGE-SCALE REGULAR AND BICHROMATIC BREAKING WAVES

2018 ◽  
pp. 90
Author(s):  
Dominic Van der A ◽  
Joep Van der Zanden ◽  
Ming Li ◽  
James Cooper ◽  
Simon Clark ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Surf Zone ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Small Scale ◽  
Breaking Wave ◽  
Wave Flume ◽  
Cfd Models

Multiphase CFD models recently have proved promising in modelling cross‐shore sediment transport and morphodynamics (Jacobsen et al 2014). However, modelling breaking wave turbulence remains a major challenge for these models, because it occurs at very different spatial and temporal length scales and involves the interaction between surface generated turbulence and turbulence generated in the bottom boundary layer. To an extent these challenges arise from a lack of appropriate experimental data, since most previous experimental studies involved breaking waves at small-scale, and have not permitted investigation of the turbulent boundary layer processes. Moreover, most existing studies have concentrated on regular waves, thereby excluding the flow and turbulence dynamics occurring at wave group time-scales under irregular waves within the surf zone. These limitations motivated a new experiment in the large-scale CIEM wave flume in Barcelona involving regular and irregular waves. The experiment was conducted in May-July 2017 within the HYDRALAB+ Transnational Access project HYBRID.

scholarly journals What Can We Learn from Experiments? Understanding the Threats to the Scalability of Experimental Results

2017 ◽  
Vol 107 (5) ◽  
pp. 282-286 ◽  
Author(s):  
Omar Al-Ubaydli ◽  
John A. List ◽  
Dana L. Suskind
Keyword(s):  
Large Scale ◽  
Treatment Effects ◽  
Experimental Studies ◽  
Experimental Results ◽  
Small Scale ◽  
Sources Of Information ◽  
Common Occurrence

Policymakers often consider interventions at the scale of the population, or some other large scale. One of the sources of information about the potential effects of such interventions is experimental studies conducted at a significantly smaller scale. A common occurrence is for the treatment effects detected in these small-scale studies to diminish substantially in size when applied at the larger scale that is of interest to policymakers. This paper provides an overview of the main reasons for a breakdown in scalability. Understanding the principal mechanisms represents a first step toward formulating countermeasures that promote scalability.

Survey of trematodes in intertidal snails from Patagonia, Argentina: new larval forms and diversity assessment

2018 ◽  
Vol 93 (3) ◽  
pp. 342-351 ◽  
Author(s):  
C. Gilardoni ◽  
G. Di Giorgio ◽  
E. Bagnato ◽  
F. Cremonte
Keyword(s):  
Large Scale ◽  
Community Dynamics ◽  
Life Cycles ◽  
Trematode Species ◽  
Small Scale ◽  
Intermediate Hosts ◽  
Scale Factors ◽  
Diversity Assessment ◽  
Southern Patagonia ◽  
Population And Community Dynamics

AbstractLarval trematodes are the main parasites of snails, and they play a crucial role because they usually castrate their snail hosts and can thus alter their population and community dynamics. This study involved a survey of seven gastropod species (Crepipatella dilatata,Fissurella radiosa,Nacella magellanica,Pareuthria fuscata,Siphonaria lessonii, S. lateralisandTrophon geversianus) parasitized by 12 trematode species (one hemiurid, one gymnophallid, two lepocreadiids, two microphallids, one notocotylid, two renicolids, one philophtalmid, one schistosomatid and one zoogonid) from southern Patagonia (47°S, 65°W), Argentina. OnlyF. radiosawas free of parasites. The study included the description of five new larvae, based on morphological and molecular information, and a comparison of the parasite diversity with that of a northern locality (42°S, 64°W), characterized by a lower mollusc diversity. Species richness and diversity of parasites were higher in the southern site. This suggests a correlation between the level of parasitism and the diversity of molluscs (first intermediate hosts), which is higher at the high-latitude site and seems to attract shorebirds, which disperse the digenean eggs and facilitate the completion of their life cycles. These results support the notion that parasitism is influenced by large-scale factors such as biogeographical patterns, and small-scale factors such as diversity or abundance of intermediate and definitive hosts.

scholarly journals Experimental Study of Flow Field Characteristics in Tidal Stream Turbine Arrays

2016 ◽  
Author(s):  
Martin Nuernberg ◽  
Longbin Tao
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Water Channel ◽  
Experimental Studies ◽  
Energy Resource ◽  
Small Scale ◽  
Large Set ◽  
Flow Field Characteristics ◽  
Tidal Turbine ◽  
Turbine Arrays

Tidal currents at many locations around the world have great potential to be used as a large scale renewable energy resource in the future. For large tidal turbine arrays to be commercially viable, the interactions of large devices operating in a confined operating environment need to be understood to optimise the layout of arrays to maximise electricity generation. This study presents results from a comprehensive experimental investigation of the flow field characteristics within tidal turbine arrays across a number of array layout configurations and current velocities. Up to four small scale turbines were placed in a circulating water channel to investigate the effects of changing array configuration and wake interaction on the flow velocity and turbulence characteristics in small array layouts. Detailed account of the resulting flow field characteristics has been taken by particle image velocimetry measurements at a number of locations within the wake of the array thus providing a large set of instantaneous flow recordings for further analysis of flow features and wake characteristics. Results are shown for experimental studies of single, three and four turbine arrays and some preliminary comparison between experimental measurements and numerical results are made.

scholarly journals Diagnosis of cirrus cloud occurrence using large-scale analysis data and a cloud-scale model

1996 ◽  
Vol 14 (7) ◽  
pp. 753-766
Author(s):  
G. Cautenet ◽  
D. Gbe
Keyword(s):  
Large Scale ◽  
Cloud Model ◽  
Analysis Data ◽  
Life Cycles ◽  
Environmental Data ◽  
Scale Model ◽  
Small Scale ◽  
Cirrus Cloud ◽  
Large Scale Model ◽  
Convergence Zones

Abstract. The development of cirrus clouds is governed by large-scale synoptic movements such as updraft regions in convergence zones, but also by smaller scale features, for instance microphysical phenomena, entrainment, small-scale turbulence and radiative field, fall-out of the ice phase or wind shear. For this reason, the proper handling of cirrus life cycles is not an easy task using a large-scale model alone. We present some results from a small-scale cirrus cloud model initialized by ECMWF first-guess data, which prove more convenient for this task than the analyzed ones. This model is Starr\\'s 2-D cirrus cloud model, where the rate of ice production/destruction is parametrized from environmental data. Comparison with satellite and local observations during the ICE89 experiment (North Sea) shows that such an efficient model using large-scale data as input provides a reasonable diagnosis of cirrus occurrence in a given meteorological field. The main driving features are the updraft provided by the large-scale model, which enhances or inhibits the cloud development according to its sign, and the water vapour availability. The cloud fields retrieved are compared to satellite imagery. Finally, the use of a small-scale model in large-scale numerical studies is examined.

scholarly journals Air Round Microjet Interaction with Coaxial Air Jet for Supersonic Speed Jets Efflux

2019 ◽  
Vol 14 (3) ◽  
pp. 39-52
Author(s):  
A. S. Tambovtsev ◽  
G. R. Grek ◽  
V. V. Kozlov ◽  
M. V. Litvinenko ◽  
Yu. A. Litvinenko ◽  
...  
Keyword(s):  
Large Scale ◽  
Experimental Studies ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Supersonic Speed ◽  
Air Jets ◽  
Air Jet ◽  
Exit Nozzle

Results of experimental studies of the round hydrogen microjet interaction with a coaxial air for supersonic speed jets efflux are presented in this work. It is shown that interaction of round and coaxial air jets at their supersonic efflux leads to appearance of a train small/large-scale and, on the contrary, large/small-scale supersonic cells on a resultant jet with growth and reduction of speed of its efflux, respectively. It is found that the result of the round and coaxial air jets interaction at their supersonic efflux does not depend on geometrical parameters of a round and coaxial exit nozzle.

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