"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:731efb55-25dc-4cfd-b972-368cea65a2e4","http://resolver.tudelft.nl/uuid:731efb55-25dc-4cfd-b972-368cea65a2e4","Numerical modelling of sedimentation in Trailing Suction Hopper Dredgers","Sloof, Ben (TU Delft Mechanical, Maritime and Materials Engineering)","Keetels, Geert (mentor); Delft University of Technology (degree granting institution)","2017","Damen Dredging Equipment is a yard dedicated to the dredging industry. The yard specializes in the design, manufacture and supply of a wide variety of dredging tools. One of the tools Damen offers is the Trailing Suction Hopper Dredger(TSHD).
The performance of such a TSHD is described by its production: the amount of sediment loaded in the hopper per unit time. The overflow loss, the material lost overboard, can easily reach up to 30%, which causes a significant decrease of the production. In addition, the turbidity plume caused by these overflow losses can have a negative environmental impact. This turbidity plume reduces light penetration, clogs filter feeders, and disperses contaminants which can be attached to the sediment. Damen is interested in estimating and reducing these overflow losses. Different models to estimate the amount of material lost overboard exist. All these models have their pros and cons. The analytical model of Miedema & Vlasblom(1996) gives a quick and good estimate of the overflow losses, but gives no insight in the flow inside the hopper. The 2DV model of Van Rhee(2002) is able to accurately simulate the flow inside the hopper, but has a large computation time. The 2DV model of this thesis gives a good estimate of the overflow losses, gives insight in the flow inside the hopper, and has an acceptable computation time.
The new 2DV model was developed in OpenFOAM. At the start of this thesis, it was possible to model mixture flow in OpenFOAM, but a sand bed could not be modelled yet. Several features had to be added to OpenFOAM to overcome this problem. The sand bed was regarded as a solid body inside the computational domain. To simulate the influence of this solid body on the mixture flow, boundary conditions were added at the bed interface. Sedimentation was modelled by adding a moving mesh. The closed flume experiments of Van Rhee(2002) have been used to validate that sedimentation is simulated accurately. By comparing hopper simulations with the hopper experiments of Van Rhee(2002), it was shown that the flow in the hopper was also simulated accurately. The computed overflow losses are, however, on the low side. The current version of OpenFOAM can calculate with only one particle fraction. In reality, the smaller fractions of the Particle Size Distribution are pushed upwards, causing the overflow losses to be higher. The 2DV-model gave a deeper insight to the phenomena in the hopper. It was possible to derive several equations which describe the flow in the hopper. With these new formulas, a simple phenomenological model was developed, which was named the 'Layer Model'.","sedimentation; hopper; OpenFOAM; CFD; overflow losses","en","master thesis","","","","","","","","2019-12-31","","","","Offshore and Dredging Engineering","OpenFOAM",""
"uuid:a9de6753-8103-49d7-8eb2-7f85ed7d88e9","http://resolver.tudelft.nl/uuid:a9de6753-8103-49d7-8eb2-7f85ed7d88e9","Luminescence Properties of NaI:Tl and CeBr3 with New Codopants","Sloof, R.W.","Dorenbos, P. (mentor); Awater, R.H.P. (mentor)","2016","The effect of new dopants on the luminescence properties of two types of scintillator crystals have been investigated. First, the luminescence properties of sodium iodine (NaI) crystals doped with thallium (Tl) and co-doped with Sulpher (S) and selenium (Se) were determined. Tl occupies cation sites whereas S and Se are supposed to occupy anion sites in the NaI crystal lattice. Doping with both S and Se led to colouring of the crystals and were not dissolved into the NaI crystal. The light yield and resolution of these crystals were reduced compared with NaI doped with only Tl (NaI:Tl). A fast light intensity decay component was observed for low temperatures (77 – 150 K) when exciting the NaI:Tl crystal with relatively low energy X-rays ($<$40 keV). This fast component may be responsible for the increase in light yield when going from 150 to 77 K. Next, the luminescence properties of cerium bromide (CeBr$_3$) crystals co-doped with cadmium (Cd), yttrium (Y), lutetium (Lu), and double co-doped with strontium (Sr) and sodium (Na), and strontium (Sr) and calcium (Ca). All co-dopants when dissolved occupy cation sites in the CeBr$_3$ crystal lattice. The Ce$^{3+}$ cations act as a luminescence centre. The CeBr$_3$ with isovalent co-dopants (Y, Lu), showed perturbation of the Ce$^{3+}$ doublet and light traps where this was not expected. The improvement of the light yield at low temperatures is stronger for the CeBr3:Lu crystal compared with that of the undoped and the Y co-doped CeBr$_3$ crystals, suggesting that Lu is better dissolved than Y into the CeBr$_3$ crystal. The divalent co-dopant Cd results in a strong perturbation of the Ce$^{3+}$ doublet and so-called deep traps in the CeBr$_3$ crystal. This causes a weak thermoluminescence intensity as well as low light yield, which strongly improve with decreasing temperature. The double co-doped CeBr$_3$:Sr,Ca crystal showed the strongest perturbation of the Ce$^{3+}$ doublet and highest thermoluminescence below 200 K. This is reflected by the decrease of the light yield in the temperature range of 77 to 200 K. The double co-doped CeBr3:Sr,Na crystal show a weak perturbation of the Ce$^{3+}$ doublet and a weak thermoluminescence due to a low trapping probability for electrons. The CeBr$_3$ crystal with Sr,Ca displays the most proportional behaviour and the highest resolution as well as light yield. The crystal with Sr,Na as co-dopants, on the contrary, has a low resolution and low light yield. The isolvalent co-dopants Y and Lu both showed a moderate proportional behaviour and a low resolution, but Y resulted in a low whereas Lu in a high light yield. The CeBr$_3$ with Lu as co-dopant shows an anomaly at 8 keV in the non-proportionality response curve (proportionality equals 40\%). Cd as a co-dopant displayed the lowest light yield and a low resolution, but a reasonable proportionality. The low resolution of all co-dopants except for Sr,Ca were caused by inhomogeneity of the crystals.","","en","master thesis","","","","","","","","","Applied Sciences","Applied Physics","","","",""
"uuid:0c792beb-f1a0-4e27-ad45-d37ab4d45887","http://resolver.tudelft.nl/uuid:0c792beb-f1a0-4e27-ad45-d37ab4d45887","Process and stability of slow moving landslides","Sloof, E.J.","Hicks, M.A. (mentor); Molenkamp, F. (mentor); Brinkgreve, R.B.J. (mentor); Kringos, N. (mentor)","2010","The stability of the slow moving Big Rock Mesa (BRM) landslide located in California (USA) was analysed. A detailed description of its geometry and soil structure is presented. For the stability vital shear zone and unsaturated zone were identified. The strength and permeability of the different layers that exist in the BRM were determined using computational methods and from literature data. The stability of landslides is susceptible to rainfall and changes to the groundwater level. The corresponding pressure changes cause slopes to become unstable. In dry periods the landslide is stable and in wet periods displacements by deformations occur. For the BRM landslide the rainfall data and displacements recorded with inclinometers were analysed. A water balance was made for a critical and stable period to evaluate the hydraulic flow. Besides rainwater it is likely that also water from adjacent areas flows into the BRM mass. Most of the rainwater is stored in the unsaturated zone of the BRM, which has an average thickness of about 42.5 m. Only a part of this water disappears by run-off and dewatering. The water pulse in the unsaturated zone is slowly drained by the evapotranspiration. The groundwater level profile of BRM was determined from measurements and computed with a statistical program called Surfer. The infiltration of water into the unsaturated zone reduces the suction. This suction is smallest over the vertical infiltration length of the water pulse. The water pulse propagates deeper into the unsaturated zone when rainfall increases. The reduction suction weakens the soil. Consequently, the stability of a slide increases with evapotranspiration and decreases with water infiltration. The stability of the BRM and the flow through the unsaturated zone was analysed with the finite element program Plaxis. However, due to the size of the BRM a full coupled analysis of deformations and hydraulic flow was not possible. Instead steady state calculations were performed. The flow through the unsaturated zone was compared with results from the one-dimensional flow program called SWAP. For the conditions of steady state calculation with suction the BRM is stable with a safety factor of 1.17. The safety factor of the BRM decreases slightly with increasing head on the hill side of the geometry. Suction in the unsaturated zone increases the safety factor by only 0.01. This suction decreases when water infiltrates. The calculated small influence of increasing groundwater table corresponds with inclinometer readings.","stability; landslides","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","Geo-Engineering","",""
"uuid:2efa55f0-52de-48b7-9304-10753e477fd7","http://resolver.tudelft.nl/uuid:2efa55f0-52de-48b7-9304-10753e477fd7","Karakterisering van dunne titaancarbide lagen door middel van röntgendiffractie","Sloof, W.G.","Delhez, R. (mentor)","1984","","","nl","master thesis","","","","","","","","","Applied Sciences","Technische Materiaalwetenschappen","","","",""