Article contents
Space–time pressure–velocity correlations in a turbulent boundary layer
Published online by Cambridge University Press: 22 April 2015
Abstract
The spatio-temporal pressure–velocity correlation in a turbulent boundary layer is investigated so as to understand the link between pressure fluctuations and turbulent coherent structures. A new experimental set-up is developed to measure the pressure fluctuations at the wall and in the field and, simultaneously, the velocity field by stereoscopic particle image velocimetry. The present measurement area covers the whole boundary layer thickness, and the spatial resolution of the measurement is good enough to assess the representative length scales of the flow. The Reynolds number effect is quantified from the data at $\mathit{Re}_{{\it\theta}}=7300$, 10 000, 18 000. The spatio-temporal three-dimensional structures of the pressure–velocity correlations,
$\boldsymbol{R}_{pu}$,
$\boldsymbol{R}_{pv}$ and
$\boldsymbol{R}_{pw}$, are evaluated. The wall pressure fluctuations are closely coupled with coherent structures which occupy a large region of the boundary layer in the wall-normal and spanwise directions and up to
$10{\it\delta}/U_{e}$ in time, where
${\it\delta}$ and
$U_{e}$ denote the boundary layer thickness and the free stream velocity. Reynolds number effects are mainly observed on the size and intensity of the pressure–velocity correlations. Conditioning the correlations on the pressure signal sign shows different types of flow phenomena linked to the positive and negative pressure events. For the wall pressure, positive pressure fluctuations appear to be correlated with the leading edge of a large sweeping motion of splatting type followed by a large ejection. The negative pressure fluctuations are linked to a localized ejection upstream, followed by a large sweeping motion downstream. For the pressure fluctuations in the field, in addition to the structures observed with the wall pressure, the pressure–velocity correlations exhibit a significant correlation in a region very extended in time. Such long structures appear to be independent of the one observed at the wall and to grow significantly in time with the Reynolds number when scaling with external variables. When conditioned by the pressure sign, clear ejection and sweeping motions are observed with associated streamwise vortical structures at a scale of the order of
$0.2{\it\delta}$. These structures can be linked to the large-scale motion and very-large-scale motion previously observed by different authors and seem to organize in a scheme analogous to the near-wall cycle, but at a much larger scale.
- Type
- Papers
- Information
- Copyright
- © 2015 Cambridge University Press
References
![](https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20170721070605003-0108:S0022112015001585:S0022112015001585_inline780.gif?pub-status=live)
Naka et al. supplementary movie
3D view of conditional wall pressure-streamwise velocity correlation Rpu for p>0 at Re_Į=10 000. The movie shows the 3D structure of the correlation as follows: 1. oblique view of positive and negative isosurfaces; 2. cut in Ģt-y plane scanning through spanwise locations; 3. cut in y-z plane at Ģt=0; 4. changing the values of isosurfaces; 5. showing the isosurfaces in different angles.
Naka et al. supplementary movie
3D view of conditional wall pressure-streamwise velocity correlation Rpu for p>0 at Re_Į=10 000. The movie shows the 3D structure of the correlation as follows: 1. oblique view of positive and negative isosurfaces; 2. cut in Ģt-y plane scanning through spanwise locations; 3. cut in y-z plane at Ģt=0; 4. changing the values of isosurfaces; 5. showing the isosurfaces in different angles.
Naka et al. supplementary movie
3D view of conditional wall pressure-streamwise velocity correlation Rpu for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-streamwise velocity correlation Rpu for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-wall normal velocity correlation Rpv for p>0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-wall normal velocity correlation Rpv for p>0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-wall normal velocity correlation Rpv for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-wall normal velocity correlation Rpv for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-spanwise velocity correlation Rpw for p>0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-spanwise velocity correlation Rpw for p>0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-spanwise velocity correlation Rpw for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of conditional wall pressure-spanwise velocity correlation Rpw for p<0 at Re_Į=10 000. The representation is the same as movie 1.
Naka et al. supplementary movie
Three components of conditional wall pressure-velocity correlations represented by color (Rpu) and vectors (Rpv and Rpw) for p>0 at Re_ƒÆ=10 000. Distribution in $y-z$ plane is scanned within -1.5 < ƒ¢tUe/ƒÂ < 1.
Naka et al. supplementary movie
Three components of conditional wall pressure-velocity correlations represented by color (Rpu) and vectors (Rpv and Rpw) for p>0 at Re_ƒÆ=10 000. Distribution in $y-z$ plane is scanned within -1.5 < ƒ¢tUe/ƒÂ < 1.
Naka et al. supplementary movie
Three components of conditional wall pressure-velocity correlations represented by color (Rpu) and vectors (Rpv and Rpw) for p<0 at Re_ƒÆ=10 000. Distribution in y-z plane is scanned within -1 < ƒ¢tUe/ƒÂ < 1.5.
Naka et al. supplementary movie
Three components of conditional wall pressure-velocity correlations represented by color (Rpu) and vectors (Rpv and Rpw) for p<0 at Re_ƒÆ=10 000. Distribution in y-z plane is scanned within -1 < ƒ¢tUe/ƒÂ < 1.5.
Naka et al. supplementary movie
3D view of field pressure-streamwise velocity correlation Rpu at probe position (b: yp+=48) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of field pressure-streamwise velocity correlation Rpu at probe position (b: yp+=48) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of field pressure--spanwise velocity correlation Rpw at probe position (b: yp+=48) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of field pressure--spanwise velocity correlation Rpw at probe position (b: yp+=48) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of field pressure--spanwise velocity correlation Rpw at probe position (h: yp/ƒÂ=0.55) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
3D view of field pressure--spanwise velocity correlation Rpw at probe position (h: yp/ƒÂ=0.55) at Re_ƒÆ=10 000. The correlation is Gaussian filtered with a width of ƒÐ+=18.9. The representation is the same as movie 1.
Naka et al. supplementary movie
Three components of conditional field pressure-velocity correlations at the probe position (c) represented by color (Rpu) and vectors (Rpv and Rpw) for p>0 at Re_ƒÆ=10 000. Distribution in $y-z$ plane is scanned within -2 < ƒ¢tUe/ƒÂ < 9.
Naka et al. supplementary movie
Three components of conditional field pressure-velocity correlations at the probe position (c) represented by color (Rpu) and vectors (Rpv and Rpw) for p>0 at Re_ƒÆ=10 000. Distribution in $y-z$ plane is scanned within -2 < ƒ¢tUe/ƒÂ < 9.
- 28
- Cited by