H. Petermeier

Technische Universität München, München, Bavaria, Germany

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Publications (11)12.71 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: An experiment on living microorganisms is conducted to gain insight into their motion and fluid exchange characteristics. Biocompatible microscopic particle image velocimetry (PIV)-systems are used to capture images of seeded particles in the induced fluid flows. To enhance the abilities of these devices we present a model-based approach for the reconstruction of admissible flow fields from captured images. A priori knowledge of the physical model of the flow is used to iteratively refine a predicted flow field. A physics-based filter operation generates a velocity field that is consistent with the model of incompressible laminar flows described by the Navier–Stokes equations. Interactive steering of the reconstruction process is achieved by exploiting programmable graphics hardware as a co-processor for numerical computations. To validate our method, we estimate velocity vector fields from synthetic image pairs of flow scenarios for which ground truth velocity fields exist and real-world image sequences of the flow induced by sessile microorganisms.
    Experiments in Fluids 07/2008; 45(2):203-222. · 1.57 Impact Factor
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    ABSTRACT: In contrast to the static chemoreceptor-related flavour perception, texture of food capable of flow is detected dynamically with oral mechanoreceptors while the food is manipulated in the mouth. The resulting sensation called mouthfeel strongly depends on the different physical properties of food. Aim of the current study is to determine numerically the occurring fluid mechanical forces in food suspensions using a simplified tongue-palate model system consisting of two parallel plates. For this purpose, the equations of fluid and particle motion are numerically solved by using structured overlapping grids. In the computational experiment, a density neutral fluid system between the plates is compressed by moving the upper plate with constant velocity down to the other one. It has been found that suspended particles move with the fluid flow but have only minor effect on the global flow field in the applied concentration.
    International Journal of Food Science & Technology 05/2007; 42(6):739 - 745. · 1.24 Impact Factor
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    ABSTRACT: In biological fluid mechanics powerful imaging methods for flow analysis are required for making progress towards a better understanding of natural phenomena being optimised in the course of evolution. At the same time it is of crucial importance that the measuring and flow visualisation techniques employed guarantee biocompatibility, i.e. they do not distort the behaviour of biosystems. Unfortunately, this restricts seriously the measures for optimising the image generation in comparison to other flow fields in which no biological systems are present. As a consequence, images of lower quality leading to erroneous artefacts are obtained. Thus, either novel detection techniques that are able to overcome these disadvantages or advanced evaluation methods enabling the sophisticated analysis and description of flow fields are essential. In the present contribution, both areas are covered. A novel so-called neuronumerical hybrid allows to detect artefacts in conventional experimental particle image velocimetry (PIV) data of microorganismic flow fields generated by ciliates. The handling of artefacts is performed by the hybrid using a priori knowledge of the flow physics formulated in numerical expressions and the enormous potential of artificial neural networks in predicting artefacts and correcting them. In fact, the neuronumerical hybrid based on the physical knowledge provided by the Taylor’s hypothesis can detect not only spurious velocity vectors but also additional phenomena like a moving boundary, in the present case caused by the contraction of the zooid of a microorganism. Apart from the detection of the artefacts, a correction of the spurious velocity vectors is possible. Furthermore, a method to detect microscopic velocity fields based on nonlinear optical filtering, optical novelty filter (ONF) is presented. On the one hand, it can be employed to expose phase changes in flow fields directly from the nonlinear response and without additional tracers. On the other hand, it can be used to preprocess low quality images of flow fields loaded with particles and extract the motion of particles with an enhanced contrast. The flow fields obtained by the correlation based PIV method of the ONF filtered and unfiltered image sequences are compared and discussed.
    Experiments in Fluids 04/2007; 42(4):611-623. · 1.57 Impact Factor
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    ABSTRACT: The feeding mechanism of the sessile protozoon Opercularia asymmetrica (Oligohymenophorea, Peritrichia) relies on the cilia beat generating a flow field that convectively transports suspended particles and dissolved substances to the oral cavity of the organism. By use of optical micro-flow measurement and theoretical methods the flow environment of two neighbouring peritrichous ciliate cells is studied. Both, yeast cells (Saccharomyces cerevisiae) and artificial flow tracers are used for the visualisation of the flow field. Artificial tracers are rejected by the protozoa and deviate from the fluid path lines, while yeast cells follow the flow almost perfectly. This is shown through a dimensional analysis of the involved hydrodynamic forces on the tracers. The measured flow field exhibits maximum velocities of 25 microm/s at around 20 microm distance ahead of an individual ciliate. The flow field extends 200 microm from the location of the ciliate. A nicking motion of the protozoon is observed and found not to obey any periodic law. Multiples of protozoa exhibit most commonly an alternating cilia beat regime generating a non-stationary flow field. It can be shown through theoretical methods that fluid exchange is enhanced in this alternating regime compared to a flow field generated by a single ciliate. Fluid exchange depends on the distance of the ciliates from each other and on the alteration frequency of the cilia beat. The comparison of an analytical Stokes' flow solution with the observed fluid flow serves to determine the force required to maintain the flow field against viscous dissipation. The force magnitude is in the order of magnitude of 10-100 pN.
    Journal of Biomechanics 02/2007; 40(1):137-48. · 2.72 Impact Factor
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    ABSTRACT: Summary In contrast to the static chemoreceptor-related flavour perception, texture of food capable of flow is detected dynamically with oral mechanoreceptors while the food is manipulated in the mouth. The resulting sensation called mouthfeel strongly depends on the different physical properties of food. Aim of the current study is to determine numerically the occurring fluid mechanical forces in food suspensions using a simplified tongue-palate model system consisting of two parallel plates. For this purpose, the equations of fluid and particle motion are numerically solved by using structured overlapping grids. In the computational experiment, a density neutral fluid system between the plates is compressed by moving the upper plate with constant velocity down to the other one. It has been found that suspended particles move with the fluid flow but have only minor effect on the global flow field in the applied concentration.
    International Journal of Food Science & Technology 01/2007; 42(6). · 1.24 Impact Factor
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    ABSTRACT: To overcome the lack of a selfcontained description of the fouling process in dairy industry, a fuzzy system is integrated in a process model using wellknown numerics thus resulting in a numero-fuzzy hybrid model. Results concerning the simulation of a dairy plant and a new approach for the study of the applied fuzzy systems are presented.
    PAMM 01/2003; 3(1):470-471.
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    ABSTRACT: The main purpose of this study is the optimization of the heat exchange process in the dairy industry. A tool for simulating heat exchanger performance was fed with technical data of various heat exchanger confi gurations and process variables. Individual plant sections, like the preheater or ultra-high-temperature (UHT) heater, were simulated with modified variables, e.g. water temperatures or heat transfer areas. One modification, developed by simulation, was successfully implemented in a dairy plant. This proved the potential of the simulation software as a tool for design of new plants or the modification of existing plants. Performance rating was done by comparing pressure differences and overall heat transfer coefficients of the original setup and the modification. Improvements of simulated model running times for individual sections of up to 50% were achieved. Advantageous modifications were embedded in a simulation of the complete plant, additionally testing its effects upon milk quality. The main parameters for evaluation of plant performance were the pressure loss over the complete plant as well as the inlet temperature of the UHT heating water while milk quality primarily was rated by inactivation of thermophilic spores and loss of thiamine.
    Food and Bioproducts Processing - FOOD BIOPROD PROCESS. 01/2003; 81(3):266-274.
  • Chemie Ingenieur Technik 01/2003; 75(8):1072-1073. · 0.70 Impact Factor
  • Chemie Ingenieur Technik 01/2002; 74(10):1492-1496. · 0.70 Impact Factor
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    ABSTRACT: A simulation model of the fouling behaviour of an arbitrary heat treatment device for milk, instancing tubular heat exchangers, is described. The final target is to examine new processing technologies in order to lengthen the processing time between two cleaning cycles whilst maintaining product quality. For this purpose a hybrid model of the fouling process in tubular heat exchangers was developed, combining deterministic differential equations with cognitive elements. The model allows the calculation of both processing and product behaviour throughout the whole heat exchanger. Pressure drop, temperature distribution and the chemical and biological effects of the heat treatment on the product can be calculated, so that the fouling behaviour and the expected product quality can be estimated. In order to validate the process model measured data from an industrial UHT plant were used. The calculated temperature profiles and pressure drops were in reasonable agreement with the experimental data. The deviation of calculated to measured values ranges between 10% and 20% for pressure, between 5% and 10% for temperature.
    Journal of Food Engineering 01/2002; · 2.28 Impact Factor
  • H. Petermeier, R. Benning, T. Becker, A. Delgado
    Chemie Ingenieur Technik 01/2000; 72(9):1079-1079. · 0.70 Impact Factor