scholarly journals UPLIFT FORCES ON WAVE EXPOSED JETTIES: SCALE COMPARISON AND EFFECT OF VENTING

2012 ◽  
Vol 1 (33) ◽  
pp. 34 ◽  
Author(s):  
Maria Gabriella Gaeta ◽  
Luca Martinelli ◽  
Alberto Lamberti
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Time Correlation ◽  
Irregular Waves ◽  
Small Scale ◽  
Static Loads ◽  
Convective Processes ◽  
Wave Celerity ◽  
Wave Induced ◽  
Uplift Forces

The large-scale experiments described herein were carried out at Forschungs-Zentrum Küste (FZK), Hannover (Germany) by a research team composed by the Universities of Bologna, Edinburgh, Southampton, Plymouth and the Coast & Harbor Engineering Inc (USA). Wave-induced loads on close-to-prototype jetties were measured. Experimental evidence indicates the presence of force peaks with a short space-time correlation structure, carried by convective processes with a velocity of the order of the wave celerity. After a 100 Hz sampling, forces on the deck bays and front induced by regular and irregular waves are analyzed, focusing the effects on the wave-in-deck loads of (i) wave irregularity, (ii) air venting and (iii) experiment scale in the evaluation of maximum and quasi-static loads. A comparison with the small-scale results is carried out, but differences could not be directly ascribed to scale effects only.

scholarly journals Micromechanical study of potential scale effects in small-scale modelling of sinker tree roots

2021 ◽  
Author(s):  
Xingyu Zhang ◽  
◽  
Matteo Ciantia ◽  
Jonathan Knappett ◽  
Anthony Leung ◽  
...  
Keyword(s):  
Particle Size ◽  
Large Scale ◽  
Scale Effects ◽  
Distinct Element ◽  
Scaling Law ◽  
Scale Model ◽  
Small Scale ◽  
Tree Roots ◽  
Scale Modelling ◽  
Element Method

When testing an 1:N geotechnical structure in the centrifuge, it is desirable to choose a large scale factor (N) that can fit the small-scale model in a model container and avoid unwanted boundary effects, however, this in turn may cause scale effects when the structure is overscaled. This is more significant when it comes to small-scale modelling of sinker root-soil interaction, where root-particle size ratio is much lower. In this study the Distinct Element Method (DEM) is used to investigate this problem. The sinker root of a model root system under axial loading was analysed, with both upward and downward behaviour compared with the Finite Element Method (FEM), where the soil is modelled as a continuum in which case particle-size effects are not taken into consideration. Based on the scaling law, with the same prototype scale and particle size distribution, different scale factors/g-levels were applied to quantify effects of the ratio of root diameter (𝑑𝑟) to mean particle size (𝐷50) on the root rootsoil interaction.

scholarly journals LARGE VERIFICATION TESTS ON ROCK SLOPE STABILITY

1988 ◽  
Vol 1 (21) ◽  
pp. 157
Author(s):  
J.W. Van der Meer ◽  
K.W. Pilarczyk
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Rock Slope Stability ◽  
Small Scale ◽  
Rock Slopes ◽  
Ripple Formation ◽  
Scale Test ◽  
Gravel Beaches ◽  
The Stability ◽  
Large Scale Tests

A number of large scale tests on stability of rock slopes and gravel beaches is described and compared with small scale test results. The following topics are treated: the stability of a rock armour layer, the profile formation of a berm breakwater, the profile formation of gravel beaches, including ripple formation, and reflection and overtopping on rock slopes. The general conclusion is that scale effects could not be found.

scholarly journals Effects of clouds on the UV Absorbing Aerosol Index from TROPOMI

2020 ◽  
Vol 13 (12) ◽  
pp. 6407-6426
Author(s):  
Maurits L. Kooreman ◽  
Piet Stammes ◽  
Victor Trees ◽  
Maarten Sneep ◽  
L. Gijsbert Tilstra ◽  
...  
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Cloud Model ◽  
Structural Features ◽  
Homogeneous Distribution ◽  
Small Scale ◽  
Retrieval Models ◽  
Cloud Models ◽  
Absorbing Aerosols ◽  
Aerosol Index

Abstract. The ultraviolet (UV) Absorbing Aerosol Index (AAI) is widely used as an indicator for the presence of absorbing aerosols in the atmosphere. Here we consider the TROPOMI AAI based on the 340 nm/380 nm wavelength pair. We investigate the effects of clouds on the AAI observed at small and large scales. The large-scale effects are studied using an aggregate of TROPOMI measurements over an area mostly devoid of absorbing aerosols (Pacific Ocean). The study reveals that several structural features can be distinguished in the AAI, such as the cloud bow, viewing zenith angle dependence, sunglint, and a previously unexplained increase in AAI values at extreme viewing and solar geometries. We explain these features in terms of the bidirectional reflectance distribution function (BRDF) of the scene in combination with the different ratios of diffuse and direct illumination of the surface at 340 and 380 nm. To reduce the dependency on the BRDF and homogenize the AAI distribution across the orbit, we present three different AAI retrieval models: the traditional Lambertian scene model (LSM), a Lambertian cloud model (LCM), and a scattering cloud model (SCM). We perform a model study to assess the propagation of errors in auxiliary databases used in the cloud models. The three models are then applied to the same low-aerosol region. Results show that using the LCM and SCM gives on average a higher AAI than the LSM. Additionally, a more homogeneous distribution is retrieved across the orbit. At the small scale, related to the high spatial resolution of TROPOMI, strong local increases and decreases in AAI are observed in the presence of clouds. The BRDF effect presented here is a first step – more research is needed to explain the small-scale cloud effects on the AAI.

scholarly journals Non-Repeatability, Scale- and Model Effects in Laboratory Measurement of Impact Loads Induced by an Overtopped Bore on a Dike Mounted Wall

2019 ◽  
Author(s):  
Maximilian Streicher ◽  
Andreas Kortenhaus ◽  
Corrado Altomare ◽  
Steven Hughes ◽  
Krasimir Marinov ◽  
...  
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Vertical Wall ◽  
Scale Factor ◽  
Scale Model ◽  
Small Scale ◽  
Length Scale ◽  
Force Measurements ◽  
Impact Forces ◽  
Small Scale Model

Abstract Overtopping bore impact forces on a dike mounted vertical wall were measured in similar large-scale (Froude length scale factor 1-to-4.3) and small-scale (Froude length scale factor 1-to-25) models. The differences due to scale effects were studied, by comparing the up-scaled force measurements from both models in prototype. It was noted that if a minimum layer thickness, velocity of the overtopping flow and water depth at the dike toe were maintained in the small-scale model, the resulting differences in impact force due to scale effects are within the range of differences due to non-repeatability and model effects.

scholarly journals Emergent Behavior and Uncertainty in Multimodel Climate Projections of Precipitation Trends at Small Spatial Scales

2006 ◽  
Vol 19 (21) ◽  
pp. 5554-5569 ◽  
Author(s):  
P. Good ◽  
J. Lowe
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Scale Effects ◽  
Spatial Scales ◽  
Regional Scale ◽  
Emergent Behavior ◽  
Small Scale ◽  
Climate Projections ◽  
New Methods ◽  
Precipitation Trends

Abstract Aspects of model emergent behavior and uncertainty in regional- and small-scale effects of increasing CO2 on seasonal (June–August) precipitation are explored. Nineteen different climate models are studied. New methods of comparing multiple climate models reveal a clearer and more impact-relevant view of precipitation projections for the current century. First, the importance of small spatial scales in multimodel projections is demonstrated. Local trends can be much larger than or even have an opposing sign to the large-scale regional averages used in previous studies. Small-scale effects of increasing CO2 and natural internal variability both play important roles here. These small-scale features make multimodel comparisons difficult for precipitation. New methods that allow information from small spatial scales to be usefully compared across an ensemble of multiple models are presented. The analysis philosophy of this study works with statistical distributions of small-scale variations within climatological regions. A major result of this work is a set of emergent relationships coupling the small- and regional-scale effects of CO2 on precipitation trends. Within each region, a single relationship fits the ensemble of 19 different climate models. Using these relationships, a surprisingly large part of the intermodel variance in small-scale effects of CO2 is explainable simply by the intermodel variance in the regional mean (a form of pattern scaling). Different regions show distinctly different relationships. These relationships imply that regional mean results are still useful, as long as the interregional variation in their relationship with impact-relevant extreme trends is recognized. These relationships are used to present a clear but rich picture of an aspect of model uncertainty, characterized by the intermodel spread in seasonal precipitation trends, including information from small spatial scales.

scholarly journals The application of science to the management of Atlantic salmon (Salmo salar): integration across scales

1998 ◽  
Vol 55 (S1) ◽  
pp. 303-311 ◽  
Author(s):  
John D Armstrong ◽  
James WA Grant ◽  
Harvey L Forsgren ◽  
Kurt D Fausch ◽  
Richard M DeGraaf ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Life Histories ◽  
Large Scale ◽  
Scale Effects ◽  
Spatial Scales ◽  
Small Scale ◽  
Spatial And Temporal Scales ◽  
Management Plans ◽  
Broad Scale ◽  
The Way

The need for integration across spatial and temporal scales in applying science to the management of Atlantic salmon is considered. The factors that are currently believed to affect the production of anadromous adult Atlantic salmon (synthesized from recent reviews) are arranged in a hierarchy in which any given process overrides those processes at lower levels. There is not a good correlation between levels in the process hierarchy and levels in hierarchies of scale. This demonstrates the importance of integrating across scales in identifying the optimum foci for targeting management action. It is not possible to generalize on the need for integration across scales within management plans. This is because of the complex ecology of salmon, the broad range of characteristics of the systems of which they are a part, and the fact that both local scale and broad scale management can have broad scale effects. Many uncertainties remain regarding the large-scale components of the ecology of salmon, the way that small-scale mechanisms interact with life histories, and the way that different factors interact to limit production of fish. When more is understood of these processes, it is likely that generalized rules might be developed to predict the management requirements for stream systems. In the meantime, it is essential that there is good integration among managers working at different scales and it is important that management systems operating at all spatial scales include high-calibre expertise to compensate for the present paucity of general rules.

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.

Dune Erosion Behind Revetments due to Overtopping of Irregular Waves With Different Angles of Wave Incidence

2016 ◽  
Author(s):  
Lisham Bonakdar ◽  
Hocine Oumeraci ◽  
Frank Thorenz ◽  
Holger Blum
Keyword(s):  
Laboratory Tests ◽  
Irregular Waves ◽  
Small Scale ◽  
Wave Overtopping ◽  
Dune Erosion ◽  
Erosion Processes ◽  
Wave Basin ◽  
Wave Induced ◽  
Wave Incidence ◽  
Water Depths

The wave-induced erosion processes involved in the interaction of revetments and dunes are investigated by means of small scale experiments performed in the 3D wave basin of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI) in Braunschweig, Germany. Two adjacent revetments (R1 and R2) were constructed with an angle of δ = 22° in plane. Irregular JONSWAP waves were generated at two water depths, which resulted in two different wave overtopping rates. The influences of the wave attack angle and wave overtopping rate on dune erosion behind the revetments are investigated by means of laboratory tests and the results are discussed.

Predicting the effects of grazing management on moorland bird abundance

2005 ◽  
Vol 2005 ◽  
pp. 69-69
Author(s):  
S. M. Gardner ◽  
G. M. Buchanan ◽  
J. W. Pearce-Higgins ◽  
M. C. Grant
Keyword(s):  
Large Scale ◽  
Vegetation Change ◽  
Scale Effects ◽  
Plant Competition ◽  
Bird Species ◽  
Field Studies ◽  
Grazing Management ◽  
Small Scale ◽  
Ecological Processes ◽  
Bird Abundance

Field studies of grazing management have frequently concluded that the magnitude and direction of vegetation response is dependent on initial vegetation condition. On upland heath, this dependence reflects the importance of small-scale ecological processes (e.g. plant competition), and local neighbourhood effects (e.g. spatial distribution of plant species), in driving the vegetation dynamics. These small-scale effects, together with variation in grazing patterns, increase the difficulty of deriving general rules about the effect of grazing on vegetation change from field studies. However, we need to determine the impacts of such grazing-related vegetation change upon biodiversity, (e.g. birds). For many bird species it is impractical to use experimental approaches due to low breeding densities, and the influence of other site and management effects (e.g. predator control). To predict the effect of management changes on them requires an accurate assessment of the large-scale effects of grazing management on the ecological landscape using data from small-scale field studies. This paper sets out an approach that integrates field studies with theoretical models to investigate the large-scale effects of grazing management on plant and bird communities on upland heath.

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