# Turbulence modification by periodically modulated scale-depending forcing

A.K. Kuczaj, B.J. Geurts, D. Lohse, W. van de Water

### Abstract

The response of turbulent flow to time-modulated forcing is studied by direct numerical simulation of the Navier-Stokes equations. The forcing is modulated via periodic energy input variations at a frequency $\omega$. Such forcing of the large-scales is shown to yield a response maximum at frequencies in the range of the inverse of the large-eddy turnover time. Time-modulated broad-band forcing is also studied in which a wide spectrum of length-scales is forced simultaneously. If smaller length-scales are explicitly agitated by the forcing, the response maximum is found to occur at higher frequencies and to become less pronounced. In case the forced spectrum is sufficiently wide, a response maximum was not observed. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as $1/ \omega$, consistent with theoretical predictions.
Original language English - 4 Published - 2006

### Fingerprint

turbulence
direct numerical simulation
turbulent flow
Navier-Stokes equation
kinetic energy
vortices
predictions
energy

• EWI-7521
• IR-63572
• METIS-236805

### Cite this

@conference{4d91c37d8f5b4a639d437b3a3db0075e,
title = "Turbulence modification by periodically modulated scale-depending forcing",
abstract = "The response of turbulent flow to time-modulated forcing is studied by direct numerical simulation of the Navier-Stokes equations. The forcing is modulated via periodic energy input variations at a frequency $\omega$. Such forcing of the large-scales is shown to yield a response maximum at frequencies in the range of the inverse of the large-eddy turnover time. Time-modulated broad-band forcing is also studied in which a wide spectrum of length-scales is forced simultaneously. If smaller length-scales are explicitly agitated by the forcing, the response maximum is found to occur at higher frequencies and to become less pronounced. In case the forced spectrum is sufficiently wide, a response maximum was not observed. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as $1/ \omega$, consistent with theoretical predictions.",
keywords = "EWI-7521, IR-63572, METIS-236805",
author = "A.K. Kuczaj and B.J. Geurts and D. Lohse and {van de Water}, W.",
year = "2006",
language = "English",
pages = "--",

}

2006. -.

TY - CONF

T1 - Turbulence modification by periodically modulated scale-depending forcing

AU - Kuczaj, A.K.

AU - Geurts, B.J.

AU - Lohse, D.

AU - van de Water, W.

PY - 2006

Y1 - 2006

N2 - The response of turbulent flow to time-modulated forcing is studied by direct numerical simulation of the Navier-Stokes equations. The forcing is modulated via periodic energy input variations at a frequency $\omega$. Such forcing of the large-scales is shown to yield a response maximum at frequencies in the range of the inverse of the large-eddy turnover time. Time-modulated broad-band forcing is also studied in which a wide spectrum of length-scales is forced simultaneously. If smaller length-scales are explicitly agitated by the forcing, the response maximum is found to occur at higher frequencies and to become less pronounced. In case the forced spectrum is sufficiently wide, a response maximum was not observed. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as $1/ \omega$, consistent with theoretical predictions.

AB - The response of turbulent flow to time-modulated forcing is studied by direct numerical simulation of the Navier-Stokes equations. The forcing is modulated via periodic energy input variations at a frequency $\omega$. Such forcing of the large-scales is shown to yield a response maximum at frequencies in the range of the inverse of the large-eddy turnover time. Time-modulated broad-band forcing is also studied in which a wide spectrum of length-scales is forced simultaneously. If smaller length-scales are explicitly agitated by the forcing, the response maximum is found to occur at higher frequencies and to become less pronounced. In case the forced spectrum is sufficiently wide, a response maximum was not observed. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as $1/ \omega$, consistent with theoretical predictions.

KW - EWI-7521

KW - IR-63572

KW - METIS-236805

M3 - Paper

SP - -

ER -