Silvio Tschisgale

Institut für Luft- und Kältetechnik · Luft- und Klimatechnik

The article proposes an algorithm to model the collision between arbitrary ellipsoids in viscous fluid. It is composed of several steps, each improving upon the standard procedure employed in the current literature. First, an efficient contact detection algorithm is presented. Then, the semi-implicit Immersed Boundary Method of Tschisgale et al. (2...

The paper addresses a fluid-structure problem involving a trapezoidal ribbon which undergoes large static reconfiguration, yielding a drag force independent of the velocity over a sizable velocity range. With experimental reference data on shape and drag available in the literature, the paper reports on Large Eddy Simulations of the configuration p...

Custom-designed nanoparticles offer the possibility of influencing the thermo-physical properties of heat carriers, such as water and transformer oil. The present study aims to clarify to what extent such nanofluids may improve convective heat transfer under turbulent flow conditions. The applied assessment methodology is based on wall-resolving la...

The paper addresses the fluid–structure interaction of submerged aquatic canopies, with particular focus on the complex interplay between coherent flow structures and the motion of vegetation elements. New insights into the underlying mechanisms are gained from a large eddy simulation of a submerged model canopy flow. The model canopy is made up of...

The paper reports on three direct numerical simulations of sediment transport with different prototypical non-spherical particle shapes, ranging from prolate to oblate to a triaxial ellipsoidal shape, and a fourth simulation with spherical particles. All physical and numerical parameters of these simulations are identical, including bulk Reynolds n...

This paper treats the separation of particles in microchannels relevant to biological and industrial process engineering. To elucidate the mechanisms creating uneven distribution of particles over the cross section, simulations are conducted with the particles being geometrically resolved and coupled to the fluid by an immersed-boundary method. In...

This paper presents a numerical method for the simulation of fluid-structure interaction specifically tailored to interactions between Newtonian fluids and a large number of slender viscoelastic Cosserat rods. Because of their high flexibility and low weight the rods considered here exhibit large deflections, even under moderate fluid loads. Their...

This paper presents a numerical method for the simulation of fluid-structure interaction specifically tailored to interactions between Newtonian fluids and a large number of slender viscoelastic Cosserat rods. Because of their high flexibility and low weight the rods considered here exhibit large deflections, even under moderate fluid loads. Their...

The paper presents four direct numerical simulations of an open channel flow with geometrically resolved particles heavier than the fluid. In each simulation the same number of mono-disperse particles is considered, with the shape of the particles varied between the simulations, while conserving the volume. Three simulations are reported with non-s...

The article proposes an algorithm to model the collision between arbitrary ellipsoids in viscous fluid. It is composed of several steps, each improving upon the standard procedure employed in the current literature. First, an efficient contact detection algorithm is presented. Then, the semi-implicit Immersed Boundary Method of Tschisgale et al., 2...

The present paper provides a collision model for Cosserat rods, able to represent a very general collision response, including frictional effects as well as multiple simultaneous collisions of a large number of rods. The proposed collision model falls into the category of constraint-based collision models. This concept is extended to a general clas...

This paper presents a new immersed boundary method for rigid particles of arbitrary shape and arbitrary density, which can be exactly zero. Especially in the latter case, the coupling of the fluid and the solid part requires special numerical techniques to obtain stability. Exploiting the direct forcing approach an algorithm with strong coupling be...

This work presents numerical simulations and selected results of the flow over aquatic canopies, consisting of artificial flexible rectangular blades, arranged in a well-defined order. The results obtained with three different Reynolds and Cauchy numbers are compared with experimental data achieving good agreement. The considered range of Cauchy nu...

This work presents a numerical method for fluid structure interactions which is well suited for simulations of abstracted aquatic canopy flows in the framework of a Large Eddy Simulation. The long-term aim is to develop a deeper understanding of the physics of flow-biota interaction in submerged canopy flows. The proposed numerical method is especi...

In this work, a method to increase the residence time of bubbles in tubes or pipes filled with liquid metal is investigated. Imposing a horizontal electric current and a perpendicular horizontal magnetic field generates an upward-directed Lorentz force. This force can counteract gravity and cause floating of bubbles. Even with homogeneous electric...

In this paper an immersed boundary method with semi-implicit fluid-solid coupling for mobile particles of arbitrary density ratio is developed. The new scheme does not require any iterations to balance fluid forces and particle forces at the interface. A new formulation of the particle equations of motion is proposed which not only accounts for the...

A vast number of numerical schemes for the simulation of disperse particle-laden or bubble-laden flows has been developed in recent years. Especially for small density ratios the strong coupling of the fluid and the solid part requires special numerical techniques to reach numerical stability. Usually, an iterative procedure is applied to balance f...

An immersed boundary method for complex-shaped bubbles is proposed. Each bubble is represented by a series of spherical harmonic functions, which covers all shapes of simply connected bubble geometries occurring in the various regimes of bubbly flow. Due to the analytical representation of the bubble surface, curvatures and normal vectors can easil...

The dynamic behaviour of a long slender structure in turbulent flow can vary considerably, depending on the particular excitation. Regimes from simple static deformation, over periodic to irregular and chaotic behaviour are observed. An example is the self-excited periodic motion of a long slender structure in cross flow. In such cases, the fluid f...

The sensitivity of a flow that is driven by a travelling magnetic field (TMF) with respect to a shift between the axes of the cylindrical liquid metal column and of the TMF was studied both experimentally and by numerical simulation. In the physical modelling, the TMF is generated by six equidistantly spaced cylindrical coils loaded with ac current...