Malizia, Fabio
(2013)

*A numerical study of temperature effects on hot wire measurements inside turbulent channel flows.*
[Laurea magistrale], Università di Bologna, Corso di Studio in

Ingegneria aerospaziale [LM-DM270] - Forli'

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## Abstract

A way to investigate turbulence is through experiments where hot wire measurements are performed. Analysis of the in turbulence of a temperature gradient on hot wire measurements is the aim of this thesis work. Actually - to author's knowledge - this investigation is the first attempt to document, understand and ultimately correct the effect of temperature gradients on turbulence statistics.
However a numerical approach is used since instantaneous temperature and streamwise velocity fields are required to evaluate this effect. A channel flow simulation at Re_tau = 180 is analyzed to make a first evaluation of the amount of error introduced by temperature gradient inside the domain. Hot wire data field is obtained processing the numerical
flow field through the application of a proper version of the King's law, which connect voltage, velocity and temperature.
A drift in mean streamwise velocity profile and rms is
observed when temperature correction is performed by means of centerline temperature. A correct mean velocity pro�le is achieved correcting temperature through its mean value at each wall normal position, but a not negligible error is still present into rms. The key point to correct properly the sensed velocity from the hot wire is the knowledge of the instantaneous temperature field. For this purpose
three correction methods are proposed.
At the end a numerical simulation at Re_tau =590 is also evaluated in order to confirm the results discussed earlier.

Abstract

A way to investigate turbulence is through experiments where hot wire measurements are performed. Analysis of the in turbulence of a temperature gradient on hot wire measurements is the aim of this thesis work. Actually - to author's knowledge - this investigation is the first attempt to document, understand and ultimately correct the effect of temperature gradients on turbulence statistics.
However a numerical approach is used since instantaneous temperature and streamwise velocity fields are required to evaluate this effect. A channel flow simulation at Re_tau = 180 is analyzed to make a first evaluation of the amount of error introduced by temperature gradient inside the domain. Hot wire data field is obtained processing the numerical
flow field through the application of a proper version of the King's law, which connect voltage, velocity and temperature.
A drift in mean streamwise velocity profile and rms is
observed when temperature correction is performed by means of centerline temperature. A correct mean velocity pro�le is achieved correcting temperature through its mean value at each wall normal position, but a not negligible error is still present into rms. The key point to correct properly the sensed velocity from the hot wire is the knowledge of the instantaneous temperature field. For this purpose
three correction methods are proposed.
At the end a numerical simulation at Re_tau =590 is also evaluated in order to confirm the results discussed earlier.

Tipologia del documento

Tesi di laurea
(Laurea magistrale)

Autore della tesi

Malizia, Fabio

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Ordinamento Cds

DM270

Parole chiave

Turbulence, Channel flow, Hot wire, Correction, Temperature, Simulation

Data di discussione della Tesi

21 Marzo 2013

URI

## Altri metadati

Tipologia del documento

Tesi di laurea
(Tesi di laurea magistrale)

Autore della tesi

Malizia, Fabio

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Ordinamento Cds

DM270

Parole chiave

Turbulence, Channel flow, Hot wire, Correction, Temperature, Simulation

Data di discussione della Tesi

21 Marzo 2013

URI

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