Solution of the Boussinesq equations by means of the finite element method

A finite element method is presented for the computation of flows that are influenced by buoyancy forces. The accuracy of several finite elements is studied by solving the Bénard problem and determining the critical Rayleigh number. It is found that the accuracy is greatly enhanced if the shape functions satisfy a certain requirement that arises from the physical nature of the problem

Watermanagement met een Oranje tintje in de 19e eeuw : afleiding van water door onderaardse gangen

In dit artikel staat de opkomst en uitbreiding van de drainage met kleibuizen centraal. Dit gebeurde geheel handmatig. Bij de Groninger methode stond men zelf in de sleuf; bij de Zeeuwse methode legde men vanaf maaiveld de buizen. Het waren de provincies bij uitstek die voorop liepen met buisdrainage. In Zeeland was door de aanwezigheid van de Wilhelminapolder, in Groningen was dat de stimulans van de Commissie van Landbou

Describing the soil physical characteristics of soil samples with cubical splines

The Mualem-Van Genuchten equations have become very popular in recent decades. Problems were encountered fitting the equations¿ parameters through sets of data measured in the laboratory: parameters were found which yielded results that were not monotonic increasing or decreasing. Due to the interaction between the soil moisture retention and the hydraulic conductivity relationship, some data sets yield a fit that seems not to be optimal. So the search for alternatives started. We ended with the cubical spline approximation of the soil physical characteristics. Software was developed to fit the spline-based curves to sets of measured data. Five different objective functions are tested and their results are compared for four different data sets. It is shown that the well-known least-square approximation does not always perform best. The distance between the measured points and the fitted curve, as can be evaluated numerically in a simple way, appears to yield good fits when applied as a criterion in the optimization procedure. Despite an increase in computational effort, this method is recommended over the least square method

PAGV : een computerprogramma voor het verwerken van automatisch geregistreerde gegevens

Voor het verwerken van lange reeksen gegevens heeft het I.C.W. de computerprogramma's VAZAL en LOGGER ontwikkeld. Ten behoeve van het afvalwarmteproject, dat in samenwerking met het PAGV wordt uitgevoerd, is nu een computerprogramma PAGV geschreven, dat het verwerken van een variabel aantal waarnemingen per scan mogelijk maak