Tomographic and time resolved PIV measurements on a ﬁnite
cylinder mounted on a ﬂat plate
Rainer Hain Æ Christian J. Ka
Received: 17 November 2007 / Revised: 25 June 2008 / Accepted: 30 July 2008 / Published online: 30 August 2008
Ó Springer-Verlag 2008
Abstract Tomographic and time resolved PIV measure-
ments were performed to examine the 3D ﬂow topology
and the ﬂow dynamic above the upper surface of a low-
aspect ratio cylinder at Re & 1 9 10
. This generic
experiment is of fundamental interest because it represents
ﬂow features which are relevant to many applications such
as laminar separation bubbles and turbulent reattachment.
At Re & 1 9 10
, laminar separation bubbles arise on the
side of the cylinder. Furthermore, on the top of the cylinder
a separation with reattachment is of major interest. The
tomographic PIV measurement, which allows to determine
all three velocity components in a volume instantaneously,
was applied to examine the ﬂow topology and interaction
between the boundary layer and wake structures on the top
of the ﬁnite cylinder. In the instantaneous ﬂow ﬁelds the tip
vortices and the recirculation region becomes visible.
However, it is also observed that the ﬂow is quite unsteady
due to the large separation occurring on the top of the
cylinder. In order to study the temporal behaviour of the
separation, time resolved PIV was applied. This technique
allows capturing the dynamic processes in detail. The
development of vortices in the separated shear layer is
observed and in addition regions with different dominant
frequencies are identiﬁed.
The ﬂow around ﬁnite cylinders mounted on a ﬂat plate has
been subject of experiments and numerical simulations in
recent years. A summary can be found in Pattenden et al.
(2005). In this article measurements on a ﬁnite cylinder
with an aspect ratio of l/d = 1 are presented where l is the
cylinder length and d is the cylinder diameter. In addition
to pressure measurements they performed PIV measure-
ments at different positions in order to determine the mean
ﬂow topology. Their examination leads to the topological
structure which is shown in Fig. 1. Between the wall and
the cylinder stump a horseshoe vortex is developed.
Directly behind the cylinder stump an arch vortex occurs.
On the top of the cylinder a recirculation area is observed
and two tip vortices ﬂow off. The experiments from
Pattenden et al. (2005) were performed at Re = 2 9 10
In the overview given by Pattenden et al. (2005)itis
observed that many of the other investigations on the ﬁnite
cylinder have been performed at lower Reynolds numbers.
The Reynolds number regime ranges from 270 to 200,000.
The investigations at different Reynolds numbers indicate
that the vortex shedding behind the ﬁnite cylinder strongly
R. Hain Á C. J. Ka
Bienroder Weg 3, 38106 Brunswick, Germany
Deutsches Zentrum fu
r Luft- und Raumfahrt e.V. (DLR),
r Aerodynamik und Stro
Lilienthalplatz 7, 38108 Brunswick, Germany
C. J. Ka
mungsmechanik und Aerodynamik LRT-7,
t der Bundeswehr Mu
39, 85577 Neubiberg, Germany
LaVision GmbH, Anna-Vandenhoeck-Ring 19,
Exp Fluids (2008) 45:715–724