cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.4121/uuid:ddba6bb9-7437-4b6b-8ebe-30d90db7cc46
title: Bezinken van zand in hopperzuigers

description: Invloed van turbulentie en korrelverdeling op het bezinkproces. Voor het optimaal beladen van sleephopperzuigers is het belangrijk om inzicht te hebben in de processen die plaats hebben in het beun van een sleephopperzuiger. Een van de deel-processen is het bezinken van zand in een hoog geconcentreerd zandwater mengsel onder invloed van turbulentie. Het doel van dit rapport is om dit bezinkproces in kaart te brengen. Om dit doel te bereiken zijn er proeven uitgevoerd in een proefopstelling waarin bezinkproeven zijn uit te voeren. Gedurende de proeven is de mate van turbulentie in de kolom, de beginconcentratie van het mengsel en gradatie van het zand gevarieerd. Hierdoor is inzicht verkregen in de invloed van beide parameters op het bezinkgedrag van verschillende zandsoorten. Tijdens de proeven worden de concentraties op 12 punten over de hoogte gemeten. Uit deze data is vervolgens een concentratieprofiel over de hoogte bepaald. Tenslotte is er gekeken in hoeverre deze data overeenkomen met het gemaakte computermodel dat dit proces kan simuleren. Uit de proeven in water die dienden om het turbulentieniveau in kaart te brengen kwamen de volgende zaken naar voren: • Uit de proefresultaten is gebleken dat de turbulentie die in de kolom wordt opgewekt redelijk homogeen over de hoogte verdeeld is en in de x- en zrichting van dezelfde orde grootte is. De belangrijkste conclusies, die uit de proeven met de uniforme zandfracties volgen, zijn: • De werkelijke karakteristieke korreldiameter verschilt aanzienlijk van de volgens de leverancier opgegeven karakteristieke korreldiameter. • De verticale turbulente snelheidsintensiteit (Vz;rms) blijkt onafhankelijk van de concentratie te zijn en afhankelijk van het turbulentieinstellingen . • De gemeten valsnelheden verschillen duidelijk van de volgens theorieen berekende valsnelheden. De gecombineerde theorie van Ruby en AIDibouni geeft de beste benadering van de meetresultaten. • De turbulente diffusiecoefficient £: is niet eenvoudig uit de meetdata te berekenen. • Uit het door ons gemaakte model volgt dat de beginconcentratie, de zandsoort en het turbulentieniveau van invloed zijn op de grootte van de turbulente diffusiecoefficient. De proeven met de min of meer natuurlijke zandverdeling maakten het volgende duidelijk: • De valsnelheid van de karakteristieke korrels van het mengsel is ongeveer gelijk aan die van de karakteristieke karrels van een uniforme zandfractie met gelijke karakteristieke korrelgrootte. • Een relatief hoog turbulentieniveau in de kolom heeft tot gevolg dat de ontmenging minder groot zal zijn. Ook leidt een hoger turbulentieniveau tot een tragere ontmenging. • De beginconcentratie is niet van invloed op de mate van ontmenging. Wel leidt een hogere beginconcentratie tot een verlaging van de snelheid waarmee de ontmenging plaatsvindt.
DOI: 10.4121/uuid:24b71a45-6906-450e-8c23-c83528058faa
title: Veldproeven op steenzettingen in Zeeland

description: Het onderzoek beschrijft de trekproeven en schuifproeven die in het veld zijn uitgevoerd ter verificatie van het liggermodel voor geklemde steenzettingen. De proeven worden in Zeeland uitgevoerd. Er is gemeten aan Hydroblocks en Basalton zettingen met resp. 35 en 25 cm zuilhoogte. In totaal zijn er 61 trekproeven en 11 schuifproeven uitgevoerd. De meetkar bestaat uit een rijdende staalconstructie, die afgestempeld kan worden op vijzels om tijdens de proeven de belasting af te dragen. Die staalconstructie is de basis van de kar, waaraan ook het aluminium meetframe kan worden gehangen met een overspanning van 4x4 meter, waarbinnen de zetting niet anders belast wordt van via de getrokken steen. Voor de metingen zijn 40 verplaatsingssensoren en 3 druksensoren (=krachtsensor) ingezet. Alle data wordt met computerapparatuur geregistreerd, waardoor het mogelijk is iedere seconde de 43 sensoren af te lezen.
DOI: 10.4121/uuid:e78e5dd8-b2bd-4e0b-8f21-558741e53e4a
title: Mixing layers in open channel flow with abrupt bed roughness changes

description: New measurements and a detailed Large Eddy Simulation model described in this report were used to investigate the underlying mixing layer processes and the corresponding development length scales. This may provide the basis to parameterize roughness heterogeneity. Measurements in a developed flow over a parallel smooth-to-rough bottom show a secondary circulation in vertical planes across the flow. This circulation causes a transverse momentum transport from the smooth to the rough side. The momentum transport by this mechanism has nearly the same order of magnitude as the transverse momentum exchange by turbulent mixing. The transverse momentum exchange enhances the effective friction. An example with a 2D model shows that this can not explain the entire increase in effective friction; additional friction is probably also caused by extra turbulence production near the smooth-to-rough interface, and bed shear stress in the spanwise direction. In the transition from a uniform flow to a compound flow over parallel roughness lanes, transverse volume transport occurs mainly in the first 4 meter (twice the width of the flume), with a maximum velocity at the start of the parallel roughness section. The development length of the velocity profiles can be scaled to the depth of flow. The vertical profiles outside the mixing layer develop in about 25 times the water depth; the mixing layer at mid depth in about 50 water depths. The secondary circulation was estimated to be fully developed after 80 water depths, but has already a significant momentum transport at half of this distance. Furthermore, the depth averaged transverse mass transport causes a gradient in the advected longitudinal momentum and therefore the water level slope is even more increased above the start of a parallel rough bottom. As a typical example of repetitive changing roughness, the flow over a roughness pattern resembling an elongated checkerboard pattern was tested. The flow appeared to develop much slower in each section than over a single parallel (infinitely long) roughness. The maximum velocity remains close to the smooth-to-rough interface and no secondary flow is observed in this configuration. Turbulent mixing is neither very effective since the vortices are changing direction not before 1 meter after a roughness change. Nevertheless, the effective friction is seriously increased by this configuration; about 30% additional friction is observed in comparison with a developed parallel flow without transverse interaction. This can be explained by the large adaptation length of the flow relative to the size of the checkerboard fields. The flow velocity is relatively large over the rough fields, and slow over the smooth fields, causing the additional drag.
DOI: 10.4121/uuid:fed501ae-c3b7-4084-9b0c-cf4cc5eee586
title: The Effects of Fluctuating Operation on Reverse Osmosis Membranes

description: Directly coupling renewable energy to reverse osmosis may be the most cost effective solution to supply potable water to remote and isolated areas that lack infrastructure and safe drinking water. These systems do not use batteries but rather operate only when sufficient energy is available and store any excess energy as water. Since reverse osmosis membranes are designed to be operated for continuous periods under constant power, it has been unclear how the fluctuating operation will affect the performance of the membranes. In these experiments, a small-scale reverse osmosis unit (maximum production 8 m3/day) was set up in the laboratory to continually recycle and treat a reservoir of artificial seawater (32 800 mg/L NaCl). The power of the high pressure pump feeding the reverse osmosis membranes is fluctuated corresponding to inputs of real wind data entered through an automated computer system. Measurements of pressure, permeate production and conductivity were continually recorded and used to determine if there were changes in the membrane permeability coefficient and salt rejection of the membrane resulting from fluctuating operation. After more than 650 hours of fluctuating operation, no deterioration of reverse osmosis membrane performance was observed.
DOI: 10.4121/uuid:44ac3fa0-c2e8-412b-9f16-b3119dc1ede9
title: Ecohydraulics in large shallow lakes: implications for management

description: Ecohydraulics in large shallow lakes: implications for management
DOI: 10.4121/uuid:2933cb88-9018-45b4-8791-dc31929827c8
title: measured wind-wave climatology Lake IJssel

description: Temperature, wind, wave and waterlevel data from IJsselmeer in period 1997-2006
DOI: 10.4121/uuid:aa7db920-aae6-4750-8975-cb739262f432
title: Mining Branching LSCs: CrossFTP, Columba traces and results

description: Two sets of execution traces from two object-oriented applications: CrossFTP (an FTP client), Columba (an email client). An event in an execution trace denotes one method call from on object in the application (to itself or to another object). Each trace contains events of one execution of the application (from launch to termination). In addition, the dataset contains results of an experiment for mining linear-time and branching-time scenarios in the form of Live Sequence Charts (LSCs) using different parameters. An index file describes the data and the experiments.
DOI: 10.4121/uuid:c9f11ee5-afe4-47e1-868d-ba11afd07ab7
title: Planform changes of braided rivers

description: This study has focused on modelling techniques to predict planform changes of braided rivers and their relation with state-of-the-art knowledge on the physical processes and the availability of model input data - data link to models and satellite info
DOI: 10.4121/uuid:0d87effb-7ae1-44ac-85db-009b261a0afa
title: Stevin Outlet Sluices: wave impact under a beam

description: The research questions were: 1. How is the wave load on the northern gates depending on the presence of the military beam? 2. How large is a wave impact load on the bottom of the military beam in the Stevin outlet sluices? 3. How well can the numerical model ComFLOW and physical modelling be used to determine the wave impact on the bottom of the military beam in the Stevin outlet sluices? 2D scaled experiments were performed making use of a model with the (simplified) geometry of the Stevin outlet sluices and regular waves. It was found that the largest wave impacts occurred for water levels equal to the bottom plane of the beam or slightly under it. This happened for the shortest waves in the test domain. The largest pressure measured on the beam was approximately 50 kPa or 35H, with H representing the incident wave height in front of the model. It was also found that the spread in the peak pressures for one single experiment was large. The results of the measured impulse per peak showed far less spread. The effect of wave impacts under the beam was also found on the vertical wall under the beam. The actual pressures however were less and they were decreasing with increasing depth. Besides physical wave impact testing, a few experiments were performed with the beam removed from the model. This resulted in wave simply running up the vertical wall of the model. They did not cause a wave impact. The measurements of both type of experiments, with and without a beam, were compared. This revealed that the total wave impulse on the gate was not affected by the presence of the beam. However the distribution of the pressure within a single wave period was significantly different. In case of a beam, a large impact peak was observed, whereas the other wave only showed a small hump caused by the deflected flow against the vertical wall. When the calculated and measured wave impact results were compared it became clear that ComFLOW underestimated the peak pressures by a factor 2 to 20 for the pressures on the impact plane. The same was done for the peak impulse. This showed that the impulse of the peak on the impact plane were underestimated by a factor 2 at most. These results confirmed that the used grid was too coarse for the program to model the physics correctly. The main conclusions to the research questions were: 1. The presence of the military beam causes a different distribution of the force on the gate within a wave period. The total amount of impulse is more or less the same as for the situation without a beam. With the military beam, a wave impact results in a peak force on the gate. Without the beam, there will be no peak force. 2. The largest measured wave impact pressure is 35H. 3. Both ComFLOW and physical modelling can be used to predict wave impacts for the geometry of Stevin outlet sluices. Much care should be taken when modelling and much attention should go to the input parameters of the program.
DOI: 10.4121/uuid:a7560df6-36ff-48fd-a1f7-be7f13105ccf
title: Winnowing: Sub-surface entrainment of particles

description: The objective of this research is to examine under which conditions sub-surface entrainment (winnowing) of particles occurs and to estimate which parameters are governing the winnowing process. The investigation is executed with laboratory experiments. Laboratory tests has been performed with specific material types, namely M32 sand (D50 = 370 ìm) and Carara gravel (D90 = 23 mm). Model tests performed by Detert et al (2010), show that the lift intensity decreases exponentially vertically through the porous bed. According to Diplas and Parker (1992), the surface layer thickness can be estimated as 2-3 times of the surface material size D90. Applying this assumption, two values of the surface layer thickness are investigated, a surface layer thickness of 6.4 cm (2.8 D90) and of 4.6 cm (2.0 D90). The study of Cui (2007) shows that an increase of entrained fines can be achieved by generating a higher surface layer mobility. For this experiment, the layer thickness and surface layer mobility are varied to investigate their influence on the winnowing process.
DOI: 10.4121/uuid:7f4c6e00-4e51-4dc3-a304-57fc2f7f3b19
title: Measuring fast-temporal sediment fluxes with an analogue acoustic sensor: a wind tunnel study

description: Research objective In this study, we test two passive traps (BEST sampler and MWAC sampler) and one acoustic device (saltiphone) in an aeolian sand wind tunnel to investigate how the experimental setup and the subsequent data processing affect the quantification of the aeolian sand flux. Type of research: Empirical research Method of data collection: Wind tunnel experiments Data comprises: - Wind velocity - Mass transport per height for different samplers - Analogue output of Saltiphone - Mass measured by balance
DOI: 10.4121/uuid:fc054477-e113-45a6-bca4-8a21116641be
title: Clogging of permeable pavements in semi-arid areas

description: In order to investigate the effect of semi-arid climate on clogging of the permeable pavements, porous concrete was chosen in this research as the proper type to apply in these areas. As the fine dust in these areas is the main cause of clogging, the pavement behavior under this condition was evaluated by the lab experiment. During the lab experiment different sub-bases (sand and stone) were also examined to see the differences in clogging process under various conditions. The results from this research shows that the wind suspended particles, as the main cause of clogging in semi-arid areas, can be washed through the pavement and cause a very slow clogging process. Comparison the results of different sub-bases shows the significant effect of the pores size in the sub-base on the clogging process. In case of higher porous sub-base, sediments can be migrated from the pavement to the sub-base easily. But in case of less porous sub-base the blocking of the interface and first layers of the sub-base can create more resistance through the flow migration. As the clogging in case of larger particles happens rapidly, therefore in order to design the pavement, average size of particles that can go through it should be taken into account.
DOI: 10.4121/uuid:ff67b0cb-91e0-4c14-a622-73219b9a8fc2
title: Reduction and Solving of Parity Games

description: Data created for investigating whether several reductions speed up the solving of parity games. Parity games were generated, reduced and solved. Reduction and solving times, as well as structural characteristics of the parity games were collected.
DOI: 10.4121/uuid:9f8c7c0e-7ed2-41fe-98c3-dd7b1d210cbc
title: Odiflocs (software)

description: Software to calculate wave-structure interaction for a porous structure (i.e a breakwater or a revetment).
DOI: 10.4121/uuid:f3d0c8ff-378e-47d4-9ed5-4da378f22ca1
title: Die Gestalt von natürlichen Steinen und ihr Fallverhalten in Wasser

description: Database with different shapes of rock plus a computer program to visualize the stones and compute falling behaviour
DOI: 10.4121/uuid:aeaf6455-7cfd-4470-b3c5-fb2aa46ff7c9
title: Drukbestanden Steenzettingen

description: dataset with pressure data under a block revetment measured during wave attack in the Deltagoot; used to calibrate the program ZSteen. Work commissioned bij Rijkswaterstaat.
DOI: 10.4121/uuid:34eb435d-4c2e-4697-8109-0f7c3457cb69
title: The Effects of Groundwater and Surface Water Use

description: This dataset contains the following data: - A water balance model for Lake Naivasha, Kenya (data/LNmodel_vanOel_etal.xlsx) as described in the publication linked to this dataset (van Oel et al., 2013) - The data files used as input data for simulations with the water balance model for the periods 1965-1979 and 1999-2010 (data/data_files.xlsx) - The monthly water abstractions for irrigation from surface water and groundwater as obtained from the Lake Naivasha Growers Group (LNGG) and the Flower Business Park (FBP), respectively (data/monthly_abstractions_irrigation.xls) - User guide LNmodel
DOI: 10.4121/uuid:3e9eb1f5-a903-4e7d-8bf7-53fb7b4a02a0
title: Experimental study on entrainment of large wood in lowland rivers

description: Wood transport in rivers, typically occurring during flood events, represents a relevant hazard for its potential to create obstruction at bridges and narrow cross-sections. Therefore, the understanding and prediction of entrainment and transport dynamics of woody material of different shapes, density and dimensions is of great interest for river managers. The paper presents results from laboratory experiments carried out to assess the entrainment conditions of large wood in lowland rivers, i.e. with negligible longitudinal slopes, relatively smooth bed and low flow Froude numbers. The tests were performed in a straight flume with fixed bed and smooth side walls for several flow conditions. Entrainment was studied for circular and square logs having different initial orientation. Integrating the results with other data available in the literature allowed to derive a semi-empirical entrainment threshold based on a force balance. This threshold is based on simple parameters, such as normal flow characteristics, log size and density as well as median diameter of bed sediments.
DOI: 10.4121/uuid:042d0fa4-bdfe-4f4b-885c-9731e80c1ed2
title: Turbulence in the wake of a roughness patch

description: Little research was done in the past concerning the propagation of three dimensional effect in shallow wake flow caused by a roughness patch. To get a better understanding of the consequences of the three dimensionality of the flow structures, experiments are performed in a wide shallow flume to examine these structures. The main objective is to examine whether the wake structure of a roughness patch can be treated as (quasi)-two-dimensional. The objective has been answered by a combination of a literature study and an experiment performed at the faculty’s laboratory. The results show four dominant mechanisms in the wake of a roughness patch: transverse mass flux, bottom friction, mixing layer and the secondary circulation. Based on a momentum balance the transverse mass flux and the bottom friction are the largest contributions to this balance. Although the contribution of the mixing layer and the secondary circulation to the recovery of the wake are of the order of 10%, their influence on the flow structure is more pronounced. The mixing layer is shifted towards the wake centerline due to the presence of a transverse mass flux forming a misalignment between the maximum spanwise Reynolds stress and the position of the wake half width. Since this shift is of limited influence on the position of the secondary circulation, a misalignment if formed between the maximum momentum transport by the secondary circulation and the mixing layer causing a lower streamwise velocity at the edge of wake with respect to the wake of an emerging obstruction. The secondary circulation is responsible for the transport of low momentum fluid towards the edge of the wake near the bottom, and high momentum fluid towards the wake centerline near the surface. This behavior is responsible for the cross gradient in the streamwise velocity profiles as shown by the data obtained. For modeling purposes of well mixed quantities, a (quasi)-two-dimensional approach only holds if the weaker streamwise velocity near the edge of the wake is taken into account. In the case a prediction of depth varying quantities is desired, the cross gradient caused by the secondary circulation needs to be implemented as well which results in the need of a three-dimensional modeling approach.
DOI: 10.4121/uuid:10939010-c4f9-4046-b72f-4bf06cc39adf
title: Modelling the equalizing process of rockfill dumps with a plough: subsea cut and transport processes

description: This master thesis gives an analytical model for cutting rockfill larger than medium coarse sand with straight cutting blades (Chapter 4.2). The analytical model is verified by performing a physical scale model. The scale model is used to attempt to simulate the process in a discrete element computer model EDEM.
DOI: 10.4121/uuid:19b5319d-b8bf-43b5-ae76-926533d9d917
title: Effectiveness of Silt Screens

description: A large series of numerical simulations with varying flow velocity, screen height, screen width, settling velocity of the sediment, water depth and upstream sediment concentration profile is conducted. The process of vertical diversion is investigated in a 3D modeling approach using large eddy simulation (LES). Performance of this numerical model is validated by means of laboratory experiments. The process of horizontal diversion is assessed with a two-dimensional horizontal (2DH) modelling approach.
DOI: 10.4121/uuid:1a1fb7ac-3f58-40f3-94de-5b03251f06ab
title: Stability of wide-graded rubble mounds

description: The Delft University of Technology provided the laboratory facilities to carry out physical model tests on a wide graded rubble mound structure representative of the core of a breakwater. The parameter D85/D15, describing the stone-size gradation of the construction material, was varied between the values 2.71 and 17.7, and two different seaward slopes of the model structure were also tested. The reshaped cross-shore profiles measured during the tests showed how if the grading increases the stability of the structure is reduced. In conclusion, this research points out how the formulas provided by the technical literature are not reliable in representing the effects of a very wide stone-size gradation in the stability of a rubble mound structure. Physical model tests proved to be a suited way to investigate these effects, as the nature of the phenomena who play a role in the stability does not allow a simple analytical representation. The tests carried out within the present study lead to the implementation of a numerical model of practical use for engineers and contractors: further investigations through laboratory tests are recommended to validate and extend the findings of this study. Another proposed direction for further research is the comparison between the results of physical model tests and the output of numerical models.