F. Durst

Friedrich-Alexander-Universität Erlangen-Nürnberg

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Günter Brenn

Graz University of Technology

M. Breuer

Helmut Schmidt University

A. Melling

Friedrich-Alexander-Universität Erlangen-Nürnberg

J. Jovanovíc

Friedrich-Alexander-Universität Erlangen-Nürnberg

J. H. Whitelaw

University of Strathclyde

H. Raszillier

Friedrich-Alexander-Universität Erlangen-Nürnberg

G. Brenner

Clausthal University of Technology

Dimosthenis Trimis

DVGW-Forschungsstelle am Engler-Bunte-Institut des Karlsruher Instituts für Technologie

Amir Naqwi

TSI (United States)

Joachim Domnick

Esslingen University of Applied Sciences

Cooperative Institutions

Friedrich-Alexander-Universität Erlangen-Nürnberg

228

Laboratoire de Chimie

Karlsruhe Institute of Technology

Centre National de la Recherche Scientifique

Imperial College London

Royal Aeronautical Society

FMP Technology (Germany)

University of Stuttgart

TCI College of Technology

Delft University of Technology

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Low-Reynolds-number flow around an oscillating circular cylinder at low Keulegan–Carpenter numbers

Journal of Fluid Mechanics (1998)

H. U. Dütsch F. Durst Stefan Becker H. Lienhart

Time-averaged LDA measurements and time-resolved numerical flow predictions were performed to investigate the laminar flow induced by the harmonic in-line oscillation of a circular cylinder in water at rest. The key parameters, Reynolds number Re and Keulegan–Carpenter number KC , were varied to study three parameter combinations in detail. Good agreement was observed for Re =100 and KC =5 between measurements and predictions comparing phase-averaged velocity vectors. For Re =200 and KC =10 weakly stable and non-periodic flow patterns occurred, which made repeatable time-averaged measurements impossible. Nevertheless, the experimentally visualized vortex dynamics was reproduced by the two-dimensional computations. For the third combination, Re =210 and KC =6, which refers to a totally different flow regime, the computations again resulted in the correct fluid behaviour. Applying the widely used model of Morison et al . (1950) to the computed in-line force history, the drag and the added-mass coefficients were calculated and compared for different grid levels and time steps. Using these to reproduce the force functions revealed deviations from those originally computed as already noted in previous studies. They were found to be much higher than the deviations for the coarsest computational grid or the largest time step. The comparison of several in-line force coefficients with results obtained experimentally by Kühtz (1996) for β=35 confirmed that force predictions could also be reliably obtained by the computations.

Vortex shedding

10.1017/s002211209800860x

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Citations (332)

Constraints On The Size And Shape Of The Receiving Aperture in a phase/doppler system

Particle & Particle Systems Characterization (1990)

Amir Naqwi F. Durst

Abstract Using computations based on Mie scattering theory, the influence of the size and shape of the receiving aperture on the signal properties of a phase/Doppler system is examined. For circular apertures exceeding a certain size limit, it is shown that the signal phase is non‐monotonic with respect to the particle diameter and exhibits abrupt changes of 180° at certain values of the diameter. This difficulty may be overcome by using rectangular apertures with appropriate aspect ratios.

Aperture (computer memory)

SIGNAL (programming language)

10.1002/ppsc.19900070121

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Experiments on the rise of air bubbles in clean viscous liquids

Journal of Fluid Mechanics (1996)

T. Maxworthy C. Gnann M. Kürten F. Durst

A number of new experiments have been performed on the rise of air bubbles in clean mixtures of distilled water and pure, reagent grade, glycerine covering a range of the relevant parameter, the Morton number, Mo = gv 4 ρ 3 /σ 3 , of 10 13 . Here g is the acceleration due to gravity, v the kinematic viscosity, ρ the density and σ the surface tension of the mixture. In these careful measurements several scaling regimes have been found that have not been discussed before in the extensive literature on the subject. The transitions between these regimes have been delineated and attempts made to discuss the dynamical processes that might be important in each of them.

Distilled water

10.1017/s0022112096007781

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Citations (179)

Analytical and numerical investigation of the optimum pressure distribution along a low-pressure axial fan blade

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science (2008)

Maria Pascu Mihai Miclea P. Epple Antonio Delgado F. Durst

In the field of axial flow turbomachines, the two-dimensional cascade model is often used experimentally or numerically to investigate fundamental flow characteristics and overall performance of the impeller. The core of the present work is a design method for axial fan cascades aiming to derive inversely the optimum blade shape based on the requirements of the impeller and not using any predefined aerofoil profiles. While most design strategies based on the aerofoil theory assume constant total pressure at all streamlines, i.e. free-vortex flow, this paper investigates the possibility of varying the total pressure along the blade and based on that, an analytical expression of the outlet blade angle is determined. When computing the blade profile at a specified radius, critical parameters reflecting on the flow characteristics are observed and adjusted (i.e. sufficient lift and controlled deceleration of the flow on the contour) so that the resulting profile is derived for minimum losses. The validation of this design strategy is given by the numerical results obtained when employed as an optimization tool for an industrial fan: 10–20 per cent absolute increase in the static efficiency of the optimized impeller.

Turbomachinery

Lift (data mining)

Axial Compressor

Static pressure

Tip clearance

10.1243/09544062jmes1023

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Citations (16)

Reynolds stress under a change of frame of reference

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics (2001)

Yu-Ning Huang F. Durst

In this paper, we study the characteristics of the Reynolds stress under a change of frame, as defined by the Euclidean group of transformation. We show that being subject to the dynamical processes induced from the mean Navier-Stokes equations, the invariance group of the fluctuating velocity and the Reynolds stress is no longer the Euclidean group of transformation, which is merely a kinematical aspect, but reduces to the extended Galilean group of transformation. As a consequence, in contrast to developing the constitutive equations for the Cauchy stress in continuum mechanics, wherein the principle of material frame-indifference is a guiding principle, the frame-dependent kinematical quantities, e.g., the mean spin tensor, may be allowed to play an effective role as the constitutive variable in turbulence modeling.

Reynolds stress

Galilean transformation

10.1103/physreve.63.056305

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Citations (10)

Computation of wind-induced vibrations of flexible shells and membranous structures

Computational fluid and solid mechanics (2001)

Markus Glück M. Breuer F. Durst A. Halfmann E. Rank

10.1016/b978-008043944-0/50875-1

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Citations (1)

Tenth Symposium on Turbulent Shear Flows : the Pennsylvania State University, University Park, PA, U.S.A., August 14-16, 1995

F. Durst J. C. Wyngaard

Source

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Citations (0)

Laser-Doppler measurement of crosswind velocity

Applied Optics (1982)

F. Durst Bruce M. Howe Gresham T. Richter

There is a need for the remote sensing of local wind velocities over distances of hundreds of meters, and laser-Doppler anemometry (LDA) has been suggested as a suitable measuring technique. In this paper the major features of an LDA system optimized for crosswind velocity measurements are presented. Computer programs based on Mie scattering theory are used to predict the performance of such systems and to extend the experimentally verified information to larger distances. A complete system for the measurement of the crosswind velocity component is described, and measurements up to 106 m verifying its performance and corresponding predictions are presented and discussed. Suggestions for further studies and developments are given.

Crosswind

10.1364/ao.21.002596

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Citations (23)

Stability of evaporating two-layered liquid film in the presence of surfactant—III. Non-linear stability analysis

Chemical Engineering Science (1998)

Vesselin N. Paunov Krassimir D. Danov N. Alleborn H. Raszillier F. Durst

Disjoining pressure

10.1016/s0009-2509(98)00100-6

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Citations (46)

On the high contraction ratio anomaly of axisymmetric contraction of grid-generated turbulence

Physics of Fluids (2008)

Özgür Ertunç F. Durst

The present paper deals with the anomalous increase in second-order moments of longitudinal velocity fluctuations reported in experiments carried out to measure properties of axisymmetric strained turbulence when the strain is provided by axisymmetric contractions (nozzles). Experimental evidence is provided that the increase is due to inaccuracies in the measurements. It is shown that the imperfect spatial resolution of X-wire probes, the mass flow rate fluctuations in the flow facility, and the electronic noise contaminate the hot-wire measurements of not only the longitudinal but also the transverse velocity fluctuation components. These kinds of contaminations start to dominate the measurements, especially when the contraction ratio of the nozzle is high and/or the turbulence level is low and turbulence length scales are small. A series of measurement and correction methods is proposed employing two single normal wires and one inclined wire to detect and eliminate all three types of contaminations of longitudinal and transverse velocity fluctuation measurements. These methods are subsequently employed to carry out turbulence measurements of grid turbulence strained in a converging nozzle with a high contraction ratio. The resulting Reynolds stress developments along the nozzle do not involve an erroneous increase in longitudinal turbulent velocity fluctuations and are consistent with theoretical expectations such as the direct numerical simulations and the rapid distortion theory. The corrected results revealed that turbulence along the nozzle reaches the two-component axisymmetric state when looked at through the anisotropy of Reynolds stresses. Furthermore, the anisotropy of Reynolds stresses exhibits zero gradient at that state. For the first time in the literature, experimental confirmation of rapid distortion theory is supplied for the axisymmetric contraction of turbulence within nozzles having a contraction ratio higher than 9. Finally, a set of experimental data is provided for the validation of turbulence models.

Reynolds stress

10.1063/1.2837173

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Citations (16)