Stabilizing the thermal lattice Boltzmann method by spatial filtering

We propose to stabilize the thermal lattice Boltzmann method by filtering the second- and third-order moments of the collision operator. By means of the Chapman-Enskog expansion, we show that the additional numerical diffusivity diminishes in the low-wavnumber limit. To demonstrate the enhanced stability, we consider a three-dimensional thermal lattice Boltzmann system involving 33 discrete velocities. Filtering extends the linear stability of this thermal lattice Boltzmann method to 10-fold smaller transport coefficients. We further demonstrate that the filtering does not compromise the accuracy of the hydrodynamics by comparing simulation results to reference solutions for a number of standardized test cases, including natural convection in two dimensions

Two-Dimensional Decaying Elastoinertial Turbulence

We numerically simulate two-dimensional, decaying elastoinertial turbulence using the finitely extensible, nonlinear, elastic spring model. We vary the polymer concentration over seven decades, and observe two turbulent elastoinertial regimes. In the weakly coupled regime only the small scale structures change, while in the strongly coupled regime all structures change. This regime is dominated by elastoinertial shock waves with drag reduction properties; i.e., the energy decay rate decreases when the polymer concentration increases

Impacts of project attributes on investment preferences : an empirical cluster analysis of energy conservation investment attitudes

Investment attitude refers to the way managements of firms value attributes of investmentproposals and weigh them in their final appraisal. It seems that among firms in the Netherlands an investment attitude exists that hinders theimplementation of energy conservation projects. Using paired comparison results from a survey on energy conservation, this paper evaluates investmentpreferences of firms by applying a Bradley-Terry model. The impact of project attributes on the investment preference is analysed in order to disclosethe underlying investment attitude and to identify barriers to the advance of energy conservation technologies. A latent class approach is used todetect clusters of firms for which specific barners play a dominant role

Test Results of DIA: A Real-Time Adaptive Integrity Monitoring Procedure, Used in an Integrated Naviation System

A practical method for real-time kinematic position determination and Quality Control (QC) in (integrated) navigation systems is presented as a combination of an extended iterated Kalm an Filter (KF) and the Detection, Identification and Adaptation (DIA) testing procedure for integrity monitoring as developed by the Delft University of Technology. DIA is a real-time recursive QC tool which can be used on multi-sensor integration. There will be no degradation in the number of sensors used by the navigation system, when applying the DIA theory to possible arising errors. Test results are presented of the KF&DIA procedure, which was implemented in the software of the survey vessel HNIMS BUYSKES of the Royal Netherlands Navy. The results of DIA are evaluated by comparing the position quality (precision and reliability) of the KF&DIA procedure with the solution of a standard integrated Least Squares (LS) position with F-test and w-test (DataSnooping, DS) as QC-tools. This analysis shows that the use of a Ka lm a n Filter in combination with DIA gives more precise results (factor = 1½) when compared to the Least Squares method with F-test and w-test. The reliability also increases, especially in cases where multiple errors in observations at one epoch occur. In general the quality of the KF&DIA solution is less influenced by errors than the LS&DS solution

Schatting van in situ fluxen van organische microverontreinigingen uit waterbodems

Dit rapport beschrijft de resultaten van een onderzoek naar naleveringsfluxen van organische microverontreinigingen, ten behoeve van het Deltares koploperproject “Biobeschikbaarheid en gedrag van stoffen”, deelproject A “Nalevering van stoffen uit waterbodems”. Hierin wordt het belang van nalevering voor de kwaliteit van het oppervlaktewater onderzocht. Dit project moet leiden tot inzicht in de situaties waarin nalevering van stoffen uit de waterbodem naar het oppervlaktewater een significante (secundaire) verontreinigingbron vormt. Dit met het oog op normoverschrijding in het oppervlaktewater (chemische doelstelling KRW), of het niet bereiken van een goede ecologische toestand (ecologische doelstelling KRW). In het voorliggende rapport worden de resultaten van kolom flux-experimenten besproken. Aan de orde komen: (a) opzet meetprogramma voor zover afwijkend van het meetplan, (b) informatie met betrekking tot kwaliteitscontrole, (c) specificatie van gebruikte analysevoorschriften (d) analyseresultaten met korte toelichtin