Generation of inflow data for inhomogeneous turbulence

Johansson, Peter S.; Andersson, Helge I.

doi:10.1007/s00162-004-0147-z

Cited by 43 publications

(26 citation statements)

References 30 publications

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“…The method has been validated in Reference [9] for a DNS and a LES of plane channel ows of di erent Reynolds numbers. In Figure 2, the turbulent root-mean-square (rms) and shear-stress proÿles downstream of a plane channel with generated velocities at the inlet are shown.…”

Section: Background and Methodsmentioning

confidence: 99%

“…See Reference [9] for a short and recent review on di erent in ow generation methods. The most realistic turbulent in ow is generally achieved by performing an auxiliary simulation which typically uses periodic boundary conditions.…”

Section: Background and Methodsmentioning

confidence: 99%

“…Less energetic modes, which are not included in the basis, are randomly superimposed in order to have some energy in the small scales. These modes are essential in order to hinder excessive growth of the large scales downstream of the inlet [9]. The amplitudes of the modes, which are added randomly, are generated by a random-number-generator with the distribution…”

Section: Background and Methodsmentioning

confidence: 99%

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Reduced basis simulations as a tool for generating turbulent inlet‐data for two opposing jets

Johansson

Andersson

2005

Numerical Methods in Fluids

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SUMMARYReduced basis simulations are used in order to generate turbulent inlet boundary conditions for a direct numerical simulation of two opposing wall jets. The two entering jets are fully turbulent channel ows of Reynolds number 180, based on friction velocity and half channel height. The in ow turbulence is generated by solving dynamical equations for the large scales only, while less energetic small scales are added randomly. The proper orthogonal decomposition method is used to identify the large scale modes used in the basis set. Mean velocity and turbulence statistics have been reported in various planes of the interaction region and the outwash jet. The increase in maximum turbulence energy from the inlet jet to the stagnation region is about 500%. The spreading rate of the merged jet was found to be 0.125.

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Section: Background and Methodsmentioning

confidence: 99%

Section: Background and Methodsmentioning

confidence: 99%

Section: Background and Methodsmentioning

confidence: 99%

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Reduced basis simulations as a tool for generating turbulent inlet‐data for two opposing jets

Johansson

Andersson

2005

Numerical Methods in Fluids

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“…Procedures based on proper orthogonal decomposition (POD) (Johansson & Andersson, 2004;Druault et al, 2004;Perret et al, 2006) are probably less expensive for the generation of inflow data than the above methods, provided there are appropriate DNS/LES (Johansson & Andersson, 2004) or experimental datasets (Druault et al, 2004;Perret et al, 2006) available for processing to obtain the most energetic modes, with an appropriate set of time dependent projection coefficients which provide the phase information. The reconstructed inflow data for later LES/DNS are 'almost realistic'.…”

Section: Introductionmentioning

confidence: 99%

Efficient Generation of Inflow Conditions for Large Eddy Simulation of Street-Scale Flows

Xie

Castro

2008

Flow Turbulence Combust

333

218

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Abstract. Using a numerical weather forecasting code to provide the dynamic large-scale inlet boundary conditions for the computation of small-scale urban canopy flows requires a continuous specification of appropriate inlet turbulence. For such computations to be practical, a very efficient method of generating such turbulence is needed.Correlation functions of typical turbulent shear flows have forms not too dissimilar to decaying exponentials. A digital-filter-based generation of turbulent inflow conditions exploiting this fact is presented as a suitable technique for LES computation of spatially developing flows. The artificially generated turbulent inflows satisfy the prescribed integral length scales and Reynolds-stress-tensor. The method is much more efficient than, for example, Klein's or Kempf et al.'s (2005) methods because at every time step only one set of two-dimensional (rather than three-dimensional) random data is filtered to generate a set of two-dimensional data with the appropriate spatial correlations. These data are correlated with the data from the previous time step by using an exponential function based on two weight factors. The method is validated by simulating plane channel flows with smooth walls and flows over arrays of staggered cubes (a generic urban-type flow). Mean velocities, the Reynolds-stress-tensor and spectra are all shown to be comparable with those obtained using classical inlet-outlet periodic boundary conditions. Confidence has been gained in using this method to couple weather scale flows and street scale computations.

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“…In order to avoid this rather expensive method the dynamics of the in-flowing turbulence can be represented by a kinematic velocity field. With the proper prescription of turbulent kinetic energy, length and time scales the inflow conditions can be made rather realistic saving substantial computational efforts [17].…”

Section: As Inflow Conditionmentioning

confidence: 99%

The Relevance of a Back-Scatter Model for Depth-Averaged Flow Simulation

Prooijen

Uijttewaal

2008

Flow Turbulence Combust

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This study demonstrates the importance of a sophisticated sub-grid model when performing a depth-averaged unsteady RANS simulation of a shallow flow. The reduction of resolution and the spatial dimensions exclude important physical processes as present in three-dimensional turbulence. Especially the effect of the bottom turbulence on the formation of horizontal eddies appears of key importance. A method is proposed to incorporate these effects by means of a kinematic simulation that mimics the residual turbulent fluctuations in a straight channel flow after depthaveraging. This method is developed in the context of the evolution of large eddies in a shallow mixing layer. A comparison with experiments shows that the proposed method works satisfactory. Naturally, it does not fully account for the omission of all 3D-effects.

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Generation of inflow data for inhomogeneous turbulence

Cited by 43 publications

References 30 publications

Reduced basis simulations as a tool for generating turbulent inlet‐data for two opposing jets

Reduced basis simulations as a tool for generating turbulent inlet‐data for two opposing jets

Efficient Generation of Inflow Conditions for Large Eddy Simulation of Street-Scale Flows

The Relevance of a Back-Scatter Model for Depth-Averaged Flow Simulation

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