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Munich.
5th edition.
A NOVEL SYSTEM FOR THE COMBINED MEASUREMENT OF WAVE- AND FLOW-FIELDS BENEATH WIND
INDUCED WATER WAVES
Frank Hering
Gunther Balschbach
Bernd Jähne
Interdisciplinary Center for Scientific Computing
University of Heidelberg
Im Neuenheimer Feld 368
D-69120 Heidelberg
Federal Republic of Germany
fhering@giotto.iwr.uni-heidelberg.de
Institute for Environmental Physics
University of Heidelberg
Im Neuenheimer Feld 366
D-69120 Heidelberg
Federal Republic of Germany
Commision V, Working Group V/III
KEY WORDS: Camera,Optical,Sensor,Underwater,Experiment
ABSTRACT
At the same time and location, simultaneous time series of wave slope images and the flowfield beneath water waves were
obtained using an integrated set-up including particle-tracking and wave slope instruments. By an especially developed tracking
algorithm, hundreds of seeding particles can be traced automatically, measuring the flow field. At the the same location the
wave-field was measured with an illumination technique based on shape-from-refraction. Simultaneous flow- and wave-field
measurements allow the investigation of transport processes across the water surface.
1 INTRODUCTION
Figure 1: Experiments were conducted at the circular wind/wave
facility (perimeter 11.6 m, width 0.3 m, water depth 0.3 m) of the
Institute for Environmental Physics of the University of Heidelberg
(Germany).
In this paper a novel optical technique is described that com-
bines two spatially measuring systems in one setup: wave
slope imaging and flow visualization. Both systems have
already been used individually for some time, but are now
put together for the first time. The wave visualization pro-
vides all relevant parameters of the water wave: the lo-
cal wave number, the frequency, and the phase speed as
à function of the phase and amplitude of the long waves
[Balschbach et al., 95]. From the flow field measurements,
231
similar information is gained for the orbital velocities. In
addition, two dimensional velocity fields and later vorticity
fields can be derived, yielding mass flux and Reynolds stresses
[Hering, 96]. The aim of this paper is to describe the imag-
ing techniques for simultaneous flow field and wave measure-
ments. The instruments were mounted at Heidelbergs circular
wind/wave facility, see Fig. 1.
2 PARTICLE TRACKING
uum
ime aperture
camera cylindrical lens
halogen lamp
Figure 2: Scheme of the optical instrument as used for Particle
Tracking. Due to the integration time of the camera tracer particles
in the light sheet are visualized as streaks.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
