scholarly journals Numerical model predictions of autogenic fluvial terraces and comparison to climate change expectations

2016 ◽  
Vol 121 (3) ◽  
pp. 512-544 ◽  
Author(s):  
Ajay B. S. Limaye ◽  
Michael P. Lamb
Author(s):  
Athul Sasikumar ◽  
Arun Kamath ◽  
Onno Musch ◽  
Arne Erling Lothe ◽  
Hans Bihs

In coastal areas, climate change is causing mean sea level rise and more frequent storm surge events. This means the breakwaters are expected to withstand the action of more severe incident waves and larger overtopping rates than they were designed for. Therefore, these impacts may have a negative effect on the functionality such as overtopping above the acceptable limits, in addition to stability of these structures. A breakwater which has been partly damaged by a storm stronger than the design storm has weak spots that can easily be damaged further. One way of protecting these breakwaters subjected to climate change is to build a submerged breakwater on the seaward side. This study focuses on the use of numerical model for optimal dimension of a submerged breakwater to be used as a protective measure for an existing structure. Comparisons are made between transmission coefficient predicted in the numerical model and those calculated from different formulae in literature. The variation in transmission coefficient due to different relative submergence and relative width parameters for waves with different steepness is studied and curves showing the dependence of these parameters on wave transmission are made. These results are then used for a test case in Kiberg, Norway where a submerged breakwater is proposed in front of a existing damaged rubble mound breakwater. The optimal geometry generated on the basis of curves is then implemented in the local-scale finite element wave prediction model, CGWAVE.


Author(s):  
Yun-Hsiang Sun ◽  
Tao Chen ◽  
Christine Qiong Wu ◽  
Cyrus Shafai

In this paper, we provide not only key knowledge for friction model selection among candidate models but also experimental friction features compared with numerical predictions reproduced by the candidate models. A motor-driven one-dimensional sliding block has been designed and fabricated in our lab to carry out a wide range of control tasks for the friction feature demonstrations and the parameter identifications of the candidate models. Besides the well-known static features such as break-away force and viscous friction, our setup experimentally demonstrates subtle dynamic features that characterize the physical behavior. The candidate models coupled with correct parameters experimentally obtained from our setup are taken to simulate the features of interest. The first part of this work briefly introduces the candidate friction models, the friction features of interest, and our experimental approach. The second part of this work is dedicated to the comparisons between the experimental features and the numerical model predictions. The discrepancies between the experimental features and the numerical model predictions help researchers to judge the accuracy of the models. The relation between the candidate model structures and their numerical friction feature predictions is investigated and discussed. A table that summarizes how to select the most optimal friction model among a variety of engineering applications is presented at the end of this paper. Such comprehensive comparisons have not been reported in previous literature.


2019 ◽  
Vol 91 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Craig D. Tully ◽  
Jason A. Rech ◽  
T. Race Workman ◽  
Calogero M. Santoro ◽  
José M. Capriles ◽  
...  

AbstractA key concern regarding current and future climate change is the possibility of sustained droughts that can have profound impacts on societies. As such, multiple paleoclimatic proxies are needed to identify megadroughts, the synoptic climatology responsible for these droughts, and their impacts on past and future societies. In the hyperarid Atacama Desert of northern Chile, many streams are characterized by perennial flow and support dense in-stream wetlands. These streams possess sequences of wetland deposits as fluvial terraces that record past changes in the water table. We mapped and radiocarbon dated a well-preserved sequence of in-stream wetland deposits along a 4.3-km reach of the Río San Salvador in the Calama basin to determine the relationship between regional climate change and the incision of in-stream wetlands. The Río San Salvador supported dense wetlands from 11.1 to 9.8, 6.4 to 3.5, 2.8 to 1.3, and 1.0 to 0.5 ka and incised at the end of each of these intervals. Comparison with other in-stream wetland sequences in the Atacama Desert, and with regional paleoclimatic archives, indicates that in-stream wetlands responded similarly to climatic changes by incising during periods of extended drought at ~9.8, 3.5, 1.3, and 0.5 ka.


Forests ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 705 ◽  
Author(s):  
Ying Guo ◽  
Jing Guo ◽  
Xin Shen ◽  
Guibin Wang ◽  
Tongli Wang

Ginkgo (Ginkgo biloba L.) is not only considered a ‘living fossil’, but also has important ecological, economic, and medicinal values. However, the impact of climate change on the performance and distribution of this plant is an increasing concern. In this study, we developed a bioclimatic model based on data about the occurrence of ginkgo from 277 locations, and validated model predictions using a wide-ranging field test (12 test sites, located at the areas from 22.49° N to 39.32° N, and 81.11° E to 123.53° E). We found that the degree-days below zero were the most important climate variable determining ginkgo distribution. Based on the model predictions, we classified the habitat suitability for ginkgo into four categories (high, medium, low, and unsuitable), accounting for 9.29%, 6.09%, 8.46%, and 76.16% of China’s land area, respectively. The ANOVA results of the validation test showed significant differences in observed leaf-traits among the four habitat types (p < 0.05), and importantly the rankings of the leaf traits were consistent with our classification of the habitat suitability, suggesting the effectiveness of our classification in terms of biological and economic significance. In addition, we projected that suitable (high and medium) habitats for ginkgo would shrink and shift northward under both the RCP4.5 and RCP8.5 climate change scenarios for three future periods (the 2020s, 2050s, and 2080s). However, the area of low-suitable habitat would increase, resulting in a slight decrease in unsuitable habitats. Our findings contribute to a better understanding of climate change impact on this plant and provide a scientific basis for developing adaptive strategies for future climate.


1988 ◽  
Vol 43 (4) ◽  
pp. 309-343 ◽  
Author(s):  
J. R. Salmon ◽  
H. W. Teunissen ◽  
R. E. Mickle ◽  
P. A. Taylor

Author(s):  
P. Fede ◽  
G. Moula ◽  
A. Ingram ◽  
T. Dumas ◽  
O. Simonin

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.


1979 ◽  
Vol 101 (4) ◽  
pp. 232-238 ◽  
Author(s):  
S. D. Mahanty ◽  
R. B. Roemer

A probe which is capable of applying known, controlled pressures to the skin, and measuring the subsequent tissue deflections and skin surface temperatures has been designed and tested. This paper describes the design of the probe, with emphasis on the thermal aspects. The fin effect of the probe superstructure is compensated for by providing an appropriately sized reflective area on that portion of the probe which contacts the skin. Experimental calibration results and numerical model predictions are presented.


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