Application of a Fractional-Step Method to Incompressible Navier-Stokes Equations

Preface Part I. Turbulence: 1. Introduction 2. Coherent structures 3. Proper orthogonal decomposition 4. Galerkin projection Part II. Dynamical Systems: 5. Qualitative theory 6. Symmetry 7. One-dimensional 'turbulence' 8. Randomly perturbed systems Part III. 9. Low-dimensional Models: 10. Behaviour of the models Part IV. Other Applications and Related Work: 11. Some other fluid problems 12. Review: prospects for rigor Bibliography.

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Turbulence, Coherent Structures, Dynamical Systems and Symmetry

A spectral element method for fluid dynamics: Laminar flow in a channel expansion

Laser-Doppler measurements of velocity distribution and reattachment length are reported downstream of a single backward-facing step mounted in a two-dimensional channel. Results are presented for laminar, transitional and turbulent flow of air in a Reynolds-number range of 70 < Re < 8000. The experimental results show that the various flow regimes are characterized by typical variations of the separation length with Reynolds number. The reported laser-Doppler measurements do not only yield the expected primary zone of recirculating flow attached to the backward-facing step but also show additional regions of flow separation downstream of the step and on both sides of the channel test section. These additional separation regions have not been previously reported in the literature.Although the high aspect ratio of the test section (1:36) ensured that the oncoming flow was fully developed and two-dimensional, the experiments showed that the flow downstream of the step only remained two-dimensional at low and high Reynolds numbers.The present study also included numerical predictions of backward-facing step flow. The two-dimensional steady differential equations for conservation of mass and momentum were solved. Results are reported and are compared with experiments for those Reynolds numbers for which the flow maintained its two-dimensionality in the experiments. Under these circumstances, good agreement between experimental and numerical results is obtained.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112083002839

Experimental and Theoretical Investigation of Backward-Facing Step Flow

The dynamic subgrid-scale (SGS) model of Germano et al. (1991) is generalized for the large eddy simulation (LES) of compressible flows and transport of a scalar. The model was applied to the LES of decaying isotropic turbulence, and the results are in excellent agreement with experimental data and direct numerical simulations. The expression for the SGS turbulent Prandtl number was evaluated using direct numerical simulation (DNS) data in isotropic turbulence, homogeneous shear flow, and turbulent channel flow. The qualitative behavior of the model for turbulent Prandtl number and its dependence on molecular Prandtl number, direction of scalar gradient, and distance from the wall are in accordance with the total turbulent Prandtl number from the DNS data.

A dynamic subgrid‐scale model for compressible turbulence and scalar transport

In this contribution a partitioned, but fully implicit coupling algorithm was applied to the numerical prediction of fluid-structure interactions occuring at lightweight membranes in civil engineering. The first test case was the steady deformation of a mobile umbrella. The second application was concerned with an unsteady wind gust exciting a membranous roof to perform structural oscillations.★

Numerical Prediction of Deformations and Oscillations of Wind-Exposed Structures

Diffusionsprozesse spielen in vielen verfahrenstechnischen Bereichen eine wichtige Rolle, allerdings stehen geeignete Messverfahren zur lokalen Konzentrationsbestimmung nur in beschränktem Umfang zur Verfügung. Ein Diodenlaser-Absorptionsspektrometer wurde entwickelt, welches entlang dem kurzen, kollimierten Messstrahl integrierte Wasserdampf-Konzentrationsmessungen mit einer lateralen Auflösung von 200μm ermöglicht. Es wurden Konzentrationsprofile in teilweise mit Wasser gefüllten Standardküvetten vermessen und daraus der Stoffstrom berechnet. Weiterhin werden Messungen der Feuchteprofile ober- und unterhalb einer Polymerfolie vorgestellt, welche die direkte Bestimmung der Permeabilität der Folie erlauben.

Spektrometer für experimentelle Untersuchungen der Wasserdampfdiffusion in Gasen (Spectrometer for Experimental Investigation of Water Vapour Diffusion in Gases)

Verfahren und Vorrichtung zur Umwandlung von Wärme in Arbeit Method and apparatus for the conversion of heat into work

Periodical Laminar Flow in an Expanded Pipe

Thermal spraying is an expanding technology with still growing markets. Especially the variety of plasma spraying techniques offers a number of possibilities for new and advanced applications. The spraying of sophisticated materials, the demand of generating coating structures or substrate/coating combinations with novel properties and the improvement of the spraying efficiency require a more detailed understanding of the physical and chemical reactions inside the plasma, in order to achieve an appropriate process control. The present paper demonstrates that phase-Doppler anemometry (PDA) is applicable as a powerful tool for process diagnostics in plasma spraying. Yielding simultaneous measurements of particle size and velocity at discrete locations, the PDA-technique generates new possibilities to characterize and further improve the spraying process.

Franz Durst

Papers

Numerical Prediction of Deformations and Oscillations of Wind-Exposed Structures

Spektrometer für experimentelle Untersuchungen der Wasserdampfdiffusion in Gasen (Spectrometer for Experimental Investigation of Water Vapour Diffusion in Gases)

Verfahren und Vorrichtung zur Umwandlung von Wärme in Arbeit Method and apparatus for the conversion of heat into work

Periodical Laminar Flow in an Expanded Pipe

Phase-Doppler Anemometry (PDA) a New Tool for Monitoring Thermal Spraying