Jonas Steigerwald

• Master of Science
• University of Stuttgart

We investigate numerically the influence of thixotropic effects on the impact of a drop onto a thin film, a fundamental process in many technical systems. Direct numerical simulations are performed with a Volume-of-Fluid (VOF) method based multiphase flow solver whose capabilities are expanded in order to enable simulations of a thixotropic liquid....

This work presents a systematic experimental study of droplet impact onto a wet substrate. Four different silicone oils are used, covering a range of Reynolds number between $$116< \text{Re} <1106$$ 116 < Re < 1106 at two different initial wall film heights. The objective is to characterize the temporal and radial evolution of the velocity field wi...

In-air microfluidics became a new method for technical production processes with ultra-high throughput formerly performed in micro channels. Direct Numerical Simulations (DNS) provide a valuable contribution for the fundamental understanding of multiphase flow and later application design. This chapter presents a feasibility study with first DNS re...

We experimentally observe a new phenomenon, the formation of a toroidal region of lower film thickness in the center of the lamella formed during high Weber number water droplet impacts onto smooth heated walls. This region forms around the air bubble, which is entrapped during the initial impact phase at the impact center. Our study encompasses a...

Single droplet impacts onto thin wall-films are a common phenomenon in many applications. For sufficiently high impact velocities, the droplet impact process consists of three phases, i.e., initial contact stage, droplet deformation with radial momentum transfer inducing an upward rising lamella, and crown propagation. Here, we present the results...

In multiphase flows, the evolution of fluid-fluid interfaces is of interest in many applications. In addition to fluid dynamic forces governing the flow in the entire volume, surface tension determines droplet interfaces. Here, the analysis of interface kinematics can help in the investigation of interface deformation and the identification of pote...

Liquids with a non-Newtonian rheological behavior are frequently encountered in engineering applications, where multiple phases can be involved. A rather scarcely investigated non-Newtonian behavior is thixotropy, in which the fluid's viscosity depends on the shear rate as well as on the deformation history. In this study, a fundamental case of an...

Water ingestion in gas turbines is used in industrial applications to improve the thermal efficiency by cooling the air before and throughout compression. However, this also leads to interactions between the liquid droplets and the compressor parts, which cause a faster degradation of the structure. The current work addresses the numerical investig...

In-air microfluidics became a new method for technical production processes with ultra-high throughput formerly performed in micro channels. Direct Numerical Simulations (DNS) provide a valuable contribution for the fundamental understanding of multiphase flow and later application design. This chapter presents a feasibility study with first DNS re...

The impact of a drop onto a liquid film is a highly relevant process which occurs in many technical systems and has been well studied for pure Newtonian liquids. Drop film interactions with non-Newtonian liquids are, however, comparatively seldom investigated, even though such complex fluids are used in many real applications. In this study, we inv...

Accurate numerical simulations of multiphase flow phenomena like jet breakup or drop film interactions require an accurate advection of the disperse phase. A proper validation of the used numerical advection scheme is therefore of key importance. In order to validate these schemes, it is standard practice to perform advection tests in which simple...

When a drop impacts onto a liquid film the outcome can differ very much and is in general difficult to parameterize due to the many influencing parameters. A parameter often idealized when studying drop film interactions is the shape of the impacting drop. Whereas for one-component interactions its influence on the impact outcome is known to some e...

A simultaneous impact of three water drops (aligned with equidistant spacing) onto a solid wall covered by a thin liquid film is predicted by direct numerical simulation using the multiphase code Free Surface 3D (FS3D) which is based on the volume-of-fluid (VOF) method and uses the piecewise linear interface calculation (PLIC) method to reconstruct...

The interaction between an airflow and a water surface influences many environmental processes. For example in a rough ocean, entrained droplets from the water surface enhance transport processes above the ocean surface which can lead to the formation of hurricanes. In order to get a better understanding of the fundamental processes we perform dire...

The scenario of an impacting drop onto a film is highly relevant in many natural and technical systems. A fundamental and often required parameter of these interactions is the so called splashing threshold above which secondary droplets are generated. For interactions with differing liquid properties for the film and the impacting drop a general sp...

The scenario of an impacting drop onto a film is highly relevant in many natural and technical systems. A fundamental and often required parameter of these interactions is the so called splashing threshold above which secondary droplets are generated. For situations in which the liquids of drop and film differ, a general threshold correlation is un...

The scenario of an impacting droplet onto a wall-film is highly relevant in many technical systems. In combustion engines, for example, the interaction of fuel drops with oil wall-films can alter the pollutant emissions. In order to make reliable predictions for these systems, it is of crucial importance to gain a deeper insight into the underlying...