15th European Turbulence Conference 2015
August 25-28th, 2015, Delft, The Netherlands

Invited speakers:


Prof. Marc Brachet. Ecole Normale Superieure, Paris, France

Prof. Peter G. Frick, Institute of Continuous Media Mechanics, Perm, Russia

Prof. Bettina Frohnapfel,  Karlsruher Institut fur Technology, Germany

Prof. Andrea Mazzino, Dipartimento di Fisica, University of Genova, Italy

Prof. Bernhard Mehlig. Department of Physics, University of Gothenburg, Sweden

Prof. Lex Smits, Mechanical and Aerospace Engineering, Princeton University, USA

Prof. Chao Sun Physics of Fluids, University of Twente, The Netherlands

Prof. Steve Tobias, Applied Mathematics, University of Leeds, United Kingdom





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10:30   Acoustics 1
Chair: Christian Poelma
10:30
15 mins
UNCERTAINTY OF NOISE PREDICTION IN CASE OF FLOW OVER A OVER A FORWARD-FACING STEP
Alexander Kolb, Michael Gruenewald, Michael Manhart
Abstract: The demand of development and application of computational aeroacoustic (CAA) prediction tools for turbulence related noise is increasing to overcome the future requirements of low noise design. Fast and accurate prediction methods are necessary to be integrated into early design processes. Several numerical and experimental studies show that the complex flow physics even of simple geometries is still not fully understood. A great interest is the identification and quantification of noise sources. Hence, immense effort has to be spent for a detailed investigation of the capability of experimental and numerical methods with respect to industrial applications. In this context the uncertainty analysis of aeroacoustic computation is a key issue for the evaluation of low-noise design.
10:45
15 mins
Interaction between the shear layer, shock-wave and vortex ring in a starting free jet injecting into a plenum
Juan Jose Pena Fernandez, Jörn Sesterhenn
Abstract: While continuous free jets have been investigated and optimised during the last 60 years, the impulsively started jet is still relatively unexplored. We focus here upon the very first stage of a compressible free round jet, when the flow is only few diameters long and the vortex ring generated by the sudden expansion interacts with the shock-waves and the shear layer. Direct numerical simulations with more than 2*10^9 grid points are carried out, discretising the compressible Navier-Stokes equations to compute both the fluid flow and the noise radiated by the interaction of the shear layer, the shock-waves and the vortex ring in a compressible free round jet. As a result of the mentioned interaction, a sound level of 111[dB] at a distance of 100 diameters from the jet has been computed. An interaction between the shear layer, the shock-waves and the vortex ring has been investigated using numerical methods in an impulsively started supersonic free round jet and noise levels of order of the loudest acoustic phenomenon in the continuous jet have been identified and quantified.
11:00
15 mins
Towards Overset LES for Aeroacoustic Source Prediction
Paul Bernicke, Rinie Akkermans, Roland Ewert, Nadine Buchmann, Juergen Dierke
Abstract: In this contribution an application of a computational aeroacoustics code (CAA) as a hybrid Zonal DNS tool is presented. The here used hybrid approach is based on a novel implementation of the Non-Linear Perturbation Equations (NLPE) extended with viscous terms, denoted as overset since a perturbation analysis is performed on top of a background flow. It is found that Direct Noise Computation results of a cylinder in uniform flow show the dipolar sound radiation characteristic as well as the expected decay of sound pressure level with distance. The extension to LES is illustrated with isotropic decaying turbulence, where the expected -5/3 slope of the reference DNS data is recovered with the LES employing the classical Smagorinsky model.
11:15
15 mins
RELIABLE METHODS FOR PREDICTING THE SOUND FROM CLUSTERED ROCKET ENGINES
Gregory A. Mack, Charles E. Tinney, Joseph H. Ruf
Abstract: High area ratio rocket engines generate strong vibro-acoustic loads primarily during transient operations, like start-up and shut-down of the engine. These loads can adversely affect the launch vehicle and its payload. Thus, an accurate prediction of the loads produced during engine start-up is pertinent to the safety and reliability of the launch vehicle. The present work focuses on developing a robust framework for predicting these loads using laboratory scale rocket nozzles tested in the fully anechoic chamber at The Uni- versity of Texas at Austin. This encompasses corrections for the observer position relative to the prominent source region, as well as scaling factors to correct for geometric factors. The test campaign encompasses single, two, three and four nozzle clusters, as well as differences in nozzle geometry and operating conditions (nozzle pressure ratio).
11:30
15 mins
Direct numerical simulation of the flow in a flue pipe
Albert J. Baars
Abstract: The flow behavior of a geometrically simplified flue pipe has been investigated by direct numerical simulation for jet Reynolds numbers of Re = 368; 490; 613. The flow process starts with the formation of a planar ring vortex at the flue exit, which travels towards the upper lip of the pipe. In the following Kelvin-Helmholtz instability appears at both sides of the jet, vortices are formed and an oscillating lateral movement of the jet set in. The vortices interacts with the upper lip, which leads to the generation of further opposite rotating vortices. After resonance is established in the pipe, the frequency spectrum of the quasi periodic state shows the expected fundamental frequency as well as several harmonics.