Dynamical model for the formation of patterned deposits at receding contact lines

We describe the formation of deposition patterns that are observed in many different experiments where a three-phase contact line of a volatile nanoparticle suspension or polymer solution recedes. A dynamical model based on a long-wave approximation predicts the deposition of irregular and regular line patterns due to self-organized pinning-depinning cycles corresponding to a stick-slip motion of the contact line. We analyze how the line pattern properties depend on the evaporation rate and solute concentration.     

Modelling the evaporation of thin films of colloidal suspensions using dynamical density functional theory

Recent experiments have shown that various structures may be formed during the evaporative dewetting of thin films of colloidal suspensions. Nanoparticle deposits of strongly branched 'flower-like', labyrinthine and network structures are observed. They are caused by the different transport processes and the rich phase behaviour of the system. We develop a model for the system, based on a dynamical density functional theory, which reproduces these structures. The model is employed to determine the influences of the solvent evaporation and of the diffusion of the colloidal particles and of the liquid over the surface. Finally, we investigate the conditions needed for 'liquid-particle' phase separation to occur and discuss its effect on the self-organized nanostructures.     

Convective instabilities in films of binary mixtures

We present a model for the evolution of films of isothermal binary liquid mixtures with a free evolving surface. The model is based on model-H supplemented by appropriate boundary conditions at the free surface and the solid substrate. The equations account for the coupled transport of the concentration of a component (convective Cahn-Hilliard equation) and the momentum (Korteweg-Navier-Stokes equation). The inclusion of convective motion makes surface deflections possible, i.e., the model allows to study couplings between the decomposition of the mixture and the evolving surface corrugations. We present selected steady layered film states for representative polymer mixtures, and show that convective motion favors their destabilization and qualitatively changes the linear instability modes in experimentally accessible ranges of parameters.     

Computergesteuertes Zeichnen stereographischer Projektionen von Kossel-Linien und ihre Anwendungen zum Studium tetragonaler Verzerrungen

Zur Ermittelung der Gitterkonstanten und der Symmetrieelemente sowie zur Orientierungsbestimmung von mikroskopisch kleinen Bereichen kompakter Proben wird die Kossel-Technik eingesetzt, wobei stereographische Projektionen von Kossel-Linien als Auswerte-Hilfsmittel herangezogen werden. Es werden Varianten eines Computerprogramms beschrieben, mit dem sich stereographische Projektionen von Kossel-Linien bzw. Ausschnittsstereogramme bei einem Minimum von Eingabewerten zeichnen lassen. Die Nützlichkeit der Stereogramme wird an Hand von Beispielen belegt, wobei besonders auf das Studium tetragonaler Verzerrungen in kubischen Substanzen eingegangen wird. Stereographic projection of Kossel-lines are often used to interprete Kosselpatterns for determination of lattice constants and orientation relations. This paper describes computer programs for plotting stereographic projections with a minimum of input data. The usefullness of such projections are shown on examples of tetragonal stressed FeAl-lattice ond α–β-transformation of Co.     

Comparison of computational aeroacoustics with theory using the benchmark case of sound waves excited from a semi‐infinite duct

In this paper the benchmark problem of radiation from a semi infinite duct is discussed. The duct is modeled by an infinitesimal thin wall. Comparisons are made between the analytic solutions of R. M. Munt and the 2^nd CAAWorkshop with our CAA‐code. In all cases a 3D axisymmetric approach is chosen to describe the propagation of a single mode. The procedure consists of two steps. Step 1 concerns a numerical simulation of the near‐field‐region. Step 2 calculates the farfield‐solution by means of the acoustic‐analogy of FfowcsWilliams and Hawkings. Since the wall is of infinitesimal thickness, the edge needs to be treated in a special way. Two different approaches are persecuted and the results are compared. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)