Nils van Velzen

Nils van Velzen
Delft University of Technology | TU · Department of Applied Mathematics

PhD

About

24
Publications
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750
Citations

Publications

Publications (24)
Conference Paper
Full-text available
As the effects of climate change are becoming more and more evident, the correlation between climate and consumption of energy has become a growing concern in the world. Researchers have been exploring possibilities to include weather influence on electricity consumption forecasts. However, no published approaches have been applied to produce accur...
Article
Full-text available
The development and application of chemistry transport models has a long tradition. Within the Netherlands the LOTOS–EUROS model has been developed by a consortium of institutes, after combining its independently developed predecessors in 2005. Recently, version 2.0 of the model was released as an open-source version. This paper presents the curric...
Article
Full-text available
The development and application of chemistry transport models has a long tradition. Within the Netherlands the LOTOS-EUROS model has been developed by a consortium of institutes, after combination of its independently developed predecessors in 2005. Recently, version 2.0 of the model was released as an open source version. This paper presents the c...
Article
Full-text available
In this study, we investigate a strategy to accelerate the data assimilation (DA) algorithm. Based on evaluations of the computational time, the analysis step of the assimilation turns out to be the most expensive part. After a study of the characteristics of the ensemble ash state, we propose a mask-state algorithm which records the sparsity infor...
Article
Full-text available
Data assimilation methods provide a means to handle the modeling errors and uncertainties in sophisticated ocean models. In this study, we have created an OpenDA-NEMO framework unlocking the data assimilation tools available in OpenDA for use with NEMO models. This includes data assimilation methods, automatic parallelization, and a recently implem...
Conference Paper
Full-text available
Title: Autolocalization techniques for ocean modelling using OpenDA Presenter: Nils van Velzen Author(s): Nils van Velzen (TU-Delft/VORtech) Umer Altaf (TU-Delft) Martin Verlaan (TU-Delft/Deltares) Preference for Oral or Poster: Oral Data assimilation method provide a mean to handle the modelling errors and uncertainties in sophisticated ocean...
Conference Paper
Full-text available
A flexible open data assimilation framework Nils van Velzen, Marc E. Ridler, Umer Altaf, Henrik Madsen, Arnold Heemink Accurate and reliable real-time hydrological forecasts are essential for protection against water-related hazards, operation of infrastructure, and water resources management. Recent advances in radar rainfall estimation and foreca...
Article
Data assimilation optimally merges model forecasts with observations taking into account both model and observational uncertainty. This paper presents a new data assimilation framework that enables the many Open Model Interface (OpenMI) 2.0 .NET compliant hydrological models already available, access to a robust data assimilation library. OpenMI is...
Conference Paper
Full-text available
Accurate and reliable real-time hydrological forecasts are essential for protection against water-related hazards, operation of infrastructure, and water resources management. Recent advances in radar rainfall estimation and forecasting, numerical weather predictions, satellite and in- situ monitoring, and faster computing facilities are opening up...
Article
Full-text available
Grondwatermodellen worden gevoed met bodemparameters, maar hoe bepaal je nu die parameterwaarden? In dit artikel worden de drukmetingen in de pompputten van een winveld gebruikt om kD, c en S-waarde te bepalen. Eerst wordt het programma MLU gebruikt, waarna de uitwerking geschikt wordt gemaakt voor MODFLOW. De optimalisatie wordt dan uitgevoerd met...
Article
Full-text available
An open-source data assimilation framework is proposed for hydrological modeling. Data assimilation (DA) in hydrodynamic and hydrological forecasting systems has great potential to improve predictions and improve model result. The basic principle is to incorporate measurement information into a model with the aim to improve model results by error m...
Article
Full-text available
Data assimilation (DA) holds considerable potential for improving hydrologic predictions as demonstrated in numerous research studies. However, advances in hydrologic DA research have not been adequately or timely implemented in operational forecast systems to improve the skill of forecasts for better informed real-world decision making. This is du...
Article
Data assimilation (DA) holds considerable potential for improving hydrologic predictions as demonstrated in numerous research studies. However, advances in hydrologic DA research have not been adequately or timely implemented into operational forecast systems to improve the skill of forecasts to better inform real-world decision making. This is due...
Article
Data Assimilation techniques are essential elements in state-of-the-art development of models and their use in operational forecasting and real-time control in the fields of groundwater, surface water and soil systems. In meteorological and atmospheric sciences, steady improvements in numerical weather forecasting and climate prediction over the la...
Article
Full-text available
The accuracy of dynamic simulation models can be increased by using observations in conjunction with a data assimilation or model calibration algorithm. However, implementing such algorithms usually increases the complexity of the model software significantly. By using concepts from object oriented programming, this thesis proposes a software frame...
Article
A generic toolbox for data assimilation called COSTA (COmmon Set of Tools for the Assimilation of data) makes it possible to simplify the application of data assimilation to models and to try out various methods for a particular model. Concepts of object oriented programming are used to define building blocks for data assimilation systems that can...
Chapter
To understand and predict the behavior of a system one can use measurements or one can develop physically based numerical models. In many applications however neither of these approaches is able to provide an accurate description of the dynamic behavior of the system. A model is always a simplification of the real world while measurements seldom pr...
Article
Full-text available
A problem solving environment for data assimilation called COSTA is developed at Delft University of Technology. The goal of COSTA is to offer a modular framework where simulation models can be combined with various data assimilation methods. COSTA defines a number of building blocks called components. Examples of components are model, method, stoc...
Article
Full-text available
This paper presents COSTA, a Problem Solving Environment for data assimilation and model calibration. Dierent data assimilation techniques have been developed and implemented over the years. Unfortunately it is very hard to reuse these implementations and quickly try out new methods. COSTA oers a modular framework for data assimilation and model ca...
Article
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This paper reports the equation-based SPYRO ® model, including its optimisation features. A flexible equation-based SPYRO ® model and solver for the simulation of the steam cracking process was the basis for the creation of a program with optimisation capabilities. This is now feasible because of the nowadays available computer power. The optimiser...
Article
The explicit SPYRO® model is transformed into the residual form using orthogonal collocation on finite elements. An effective and flexible system of sub-models is developed for the Open Spyro model. The Open Spyro model is solved using a fast and globally converging quasi-Newton method based on the update proposed by Broyden. The simulation gives t...
Thesis
Full-text available
Steam pyrolysis of ethane and naphtha is an important chemical bulk process. It produces ethylene and propylene, which are important base chemicals. In order to be competitive, crackers have to be operated at near optimal conditions. Hence, a simulation program of the process, particularly of the pyrolysis is very helpful. KTI uses and licenses suc...

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