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Nils Paul van Hinsberg

Bio: Nils Paul van Hinsberg is an academic researcher from German Aerospace Center. The author has contributed to research in topics: Reynolds number & Strouhal number. The author has an hindex of 6, co-authored 16 publications receiving 618 citations. Previous affiliations of Nils Paul van Hinsberg include Technische Universität Darmstadt & ETH Zurich.

Papers
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TL;DR: Experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented, finding a good agreement with the numerical predictions of the phenomena.
Abstract: In the present work experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented. The dynamics of drop impact on liquid surfaces, the shape of the cavity, the formation and propagation of a capillary wave in the crater, and the residual film thickness on the rigid wall are determined and analyzed. The shape of the crater within the film and the uprising liquid sheet formed upon the impact are observed using a high-speed video system. The effects of various influencing parameters such as drop impact velocity, liquid film thickness and physical properties of the liquids, including viscosity and surface tension, on the time evolution of the crater formation are investigated. Complementary to experiments the direct numerical simulations of the phenomena are performed using an advanced free-surface capturing model based on a two-fluid formulation of the classical volume-of-fluid (VOF) model in the framework of the finite volume numerical method. In this model an additional convective term is introduced into the transport equation for phase fraction, contributing decisively to a sharper interface resolution. Furthermore, an analytical model for the penetration depth of the crater is developed accounting for the liquid inertia, viscosity, gravity, and surface tension. The model agrees well with the experiments at the early times of penetration far from the wall if the impact velocity is high. Finally, a scaling analysis of the residual film thickness on the wall is conducted demonstrating a good agreement with the numerical predictions.

572 citations

Journal ArticleDOI
01 Oct 2010
TL;DR: Experimental and numerical investigations of single drop impacts onto liquid films of finite thickness investigating the dynamics of the drop impingement on liquid surface films, the shape of the cavity, the surface film dynamics and the residual film thickness are investigated and analysed.
Abstract: This paper presents experimental and numerical investigations of single drop impacts onto liquid films of finite thickness. The dynamics of the drop impingement on liquid surface films, the shape of the cavity, the surface film dynamics and the residual film thickness are investigated and analysed. The shape of the penetrating cavity within the surface film is observed experimentally using a high-speed video system. Additionally, the thickness of the liquid film between the expanding, receding and retracting cavity and the solid wall is monitored in time using an optical sensor based on chromatic confocal imaging. The effects of various influencing parameters, such as the drop impingement velocity, liquid properties (surface tension and viscosity) and the initial liquid film thickness, on the time evolution of the cavity and film dynamics are investigated. Complementary to the experiments direct numerical simulations of the drop impacts and cavity expansion are performed using a volume-of-fluid free-surface capturing model in the framework of the finite volume numerical method. The numerical predictions of the film thickness dynamics agree well with the experiments for most phases of the impingement process. Finally, a scaling analysis of the residual film thickness between the cavity and the solid wall is performed for various impingement parameters.

49 citations

Journal ArticleDOI
TL;DR: In this experimental and theoretical study a single drop impact onto a liquid layer of finite thickness is investigated, focused on the formation, expansion, receding, and merging of a cavity generated by the impact.
Abstract: In this experimental and theoretical study a single drop impact onto a liquid layer of finite thickness is investigated. It is focused on the formation, expansion, receding, and merging of a cavity generated by the impact. The shape of the cavity is observed and the evolution of its diameter is measured at various times after impact. The drop velocity, the initial film thickness, and the liquid properties are varied in the experiments. The propagation of the crater diameter in the liquid layer is described theoretically using the kinematic discontinuity approach. The mass and momentum balance equations of the liquid layer account for the inertial effects, surface tension, and gravity. A remote asymptotic solution for the temporal evolution of the crater diameter is obtained. The theoretical predictions agree well with the experimental data.

40 citations

Journal ArticleDOI
TL;DR: In this article, the spanwise-integrated unsteady aerodynamic forces and time-averaged local surface pressures on a 2D slightly rough circular cylinder were carried out over a wide range of Reynolds numbers in the high pressure wind tunnel in Gottingen.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of angle of incidence and corner radius on the aerodynamics of square-section cylinders is studied by means of wind tunnel experiments, and the results demonstrated that a decrease of the cylinder's bluffness induced lower maximum drag coefficients and r.m.s. values, as well as higher Strouhal numbers.

26 citations


Cited by
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TL;DR: OpenFoam as discussed by the authors is a CFD library for solving free surface Newtonian flows using the Reynolds averaged Navier-Stokes equations coupled with a volume of fluid method.
Abstract: SUMMARY The open-source CFD library OpenFoam® contains a method for solving free surface Newtonian flows using the Reynolds averaged Navier–Stokes equations coupled with a volume of fluid method. In this paper, it is demonstrated how this has been extended with a generic wave generation and absorption method termed ‘wave relaxation zones’, on which a detailed account is given. The ability to use OpenFoam for the modelling of waves is demonstrated using two benchmark test cases, which show the ability to model wave propagation and wave breaking. Furthermore, the reflection coefficient from outlet relaxation zones is considered for a range of parameters. The toolbox is implemented in C++, and the flexibility in deriving new relaxation methods and implementing new wave theories along with other shapes of the relaxation zone is outlined. Subsequent to the publication of this paper, the toolbox has been made freely available through the OpenFoam-Extend Community. Copyright © 2011 John Wiley & Sons, Ltd.

852 citations

Journal ArticleDOI
TL;DR: The performance of the open source multiphase flow solver, interFoam, is evaluated using a variety of verification and validation test cases, which include verification tests for pure advection (kinematics), dynamics in the high Weber number limit and dynamics of surface tension-dominated flows.
Abstract: The performance of the open source multiphase flow solver, interFoam, is evaluated in this work. The solver is based on a modified volume of fluid (VoF) approach, which incorporates an interfacial compression flux term to mitigate the effects of numerical smearing of the interface. It forms a part of the C + + libraries and utilities of OpenFOAM and is gaining popularity in the multiphase flow research community. However, to the best of our knowledge, the evaluation of this solver is confined to the validation tests of specific interest to the users of the code and the extent of its applicability to a wide range of multiphase flow situations remains to be explored. In this work, we have performed a thorough investigation of the solver performance using a variety of verification and validation test cases, which include (i) verification tests for pure advection (kinematics), (ii) dynamics in the high Weber number limit and (iii) dynamics of surface tension-dominated flows. With respect to (i), the kinematics tests show that the performance of interFoam is generally comparable with the recent algebraic VoF algorithms; however, it is noticeably worse than the geometric reconstruction schemes. For (ii), the simulations of inertia-dominated flows with large density ratios yielded excellent agreement with analytical and experimental results. In regime (iii), where surface tension is important, consistency of pressure–surface tension formulation and accuracy of curvature are important, as established by Francois et al (2006 J. Comput. Phys. 213 141–73). Several verification tests were performed along these lines and the main findings are: (a) the algorithm of interFoam ensures a consistent formulation of pressure and surface tension; (b) the curvatures computed by the solver converge to a value slightly (10%) different from the analytical value and a scope for improvement exists in this respect. To reduce the disruptive effects of spurious currents, we followed the analysis of Galusinski and Vigneaux (2008 J. Comput. Phys. 227 6140–64) and arrived at the following criterion for stable capillary simulations for interFoam: where . Finally, some capillary flows relevant to atomization were simulated, resulting in good agreement with the results from the literature.

648 citations

Journal ArticleDOI
TL;DR: Experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented, finding a good agreement with the numerical predictions of the phenomena.
Abstract: In the present work experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented. The dynamics of drop impact on liquid surfaces, the shape of the cavity, the formation and propagation of a capillary wave in the crater, and the residual film thickness on the rigid wall are determined and analyzed. The shape of the crater within the film and the uprising liquid sheet formed upon the impact are observed using a high-speed video system. The effects of various influencing parameters such as drop impact velocity, liquid film thickness and physical properties of the liquids, including viscosity and surface tension, on the time evolution of the crater formation are investigated. Complementary to experiments the direct numerical simulations of the phenomena are performed using an advanced free-surface capturing model based on a two-fluid formulation of the classical volume-of-fluid (VOF) model in the framework of the finite volume numerical method. In this model an additional convective term is introduced into the transport equation for phase fraction, contributing decisively to a sharper interface resolution. Furthermore, an analytical model for the penetration depth of the crater is developed accounting for the liquid inertia, viscosity, gravity, and surface tension. The model agrees well with the experiments at the early times of penetration far from the wall if the impact velocity is high. Finally, a scaling analysis of the residual film thickness on the wall is conducted demonstrating a good agreement with the numerical predictions.

572 citations

Journal ArticleDOI
TL;DR: In this article, the authors introduce OpenFOAM® as a tool to consider for coastal engineering applications as it solves 3D domains and considers two-phase flow, and demonstrate that active wave absorption is found to enhance stability by decreasing the energy of the system and correcting the increasing water level on long simulations.

482 citations

Journal ArticleDOI
TL;DR: A stable numerical scheme for modelling multiphase flow in porous media, where the characteristic size of the flow domain is of the order of microns to millimetres, and the accuracy and stability of the numerical method are verified, which indicate the potential of the method to predict multiphases flow processes.

412 citations