Results are presented of laboratory experiments undertaken to study the dynamics of wave propagation and transformation within the surf zone. The study involved measuring the external flow characteristics of regular plunging waves propagating along a 20 m long flume fitted with a 1:20 plane slope. To achieve this, monochromatic waves of frequency 0.4 Hz and a deep water wave height of 12 cm were generated by a servo-controlled piston-type wave maker. A set of calibrated parallel-wire capacitive wave gauges were employed to measure statistics of the free surface elevation along the slope in order to get an insight into the wave breaking behavior. To characterize the wave field, free surface elevation measurements were made in the vicinity of the break point. The measured time series data were analyzed at each flume position to obtain statistics of the mean water level, wave height, and wave velocity along the flume. Results show that as the wave propagates from deep water towards shallow water, there is an increase in the wave height, reaching a maximum height of about 21.5 cm at the break point, and then decreases sharply thereafter. Wave phase velocity calculations at different flume positions were made from the measured time series. Cross correlation techniques were used to determine the phase difference between the reference wave near the generator and the wave at various points along the flume. The local wave velocity was obtained by taking the phase difference between two points spaced 0.2 m apart. A comparison was made between the measured wave phase velocity, its linear shallow water () approximation and the roller model concept wave velocity (), at various points along the flume. The measured wave velocity c was found to lie in the range for most of the positions except near the break point. After the break point, the measured wave velocity is up to 38% higher than the theoretical value predicted using the roller model concept. Also noted is the variability of the phase speed in the breaking region. The present experiments of quantifying the mean macroscopic properties of breaking waves are a necessary prerequisite for more detailed experiments involving internal fluid velocity measurements that will follow.
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June 2013
Research-Article
Wave Height and Wave Velocity Measurements in the Vicinity of the Break Point in Laboratory Plunging Waves
R. Mukaro,
R. Mukaro
1
College of Agriculture, Engineering, and Science,
School of Chemistry and Physics,
e-mail: mukaror@ukzn.ac.za
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000
, South Africa
e-mail: mukaror@ukzn.ac.za
1Corresponding author.
Search for other works by this author on:
K. Govender,
K. Govender
Honorary Research Fellow
Centre for Instrumentation Research,
Department of Electrical Engineering,
Cape Peninsula University of Technology,
College of Agriculture, Engineering and Science,
School of Chemistry and Physics,
e-mail: kessie.gov@gmail.com
Centre for Instrumentation Research,
Department of Electrical Engineering,
Cape Peninsula University of Technology,
P.O. Box 652
,Cape Town 8000
, South Africa
;College of Agriculture, Engineering and Science,
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000
, South Africa
e-mail: kessie.gov@gmail.com
Search for other works by this author on:
H. McCreadie
H. McCreadie
College of Agriculture, Engineering, and Science,
School of Chemistry and Physics,
e-mail: Mccreadie@ukzn.ac.za
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000,
South Africa
e-mail: Mccreadie@ukzn.ac.za
Search for other works by this author on:
R. Mukaro
College of Agriculture, Engineering, and Science,
School of Chemistry and Physics,
e-mail: mukaror@ukzn.ac.za
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000
, South Africa
e-mail: mukaror@ukzn.ac.za
K. Govender
Honorary Research Fellow
Centre for Instrumentation Research,
Department of Electrical Engineering,
Cape Peninsula University of Technology,
College of Agriculture, Engineering and Science,
School of Chemistry and Physics,
e-mail: kessie.gov@gmail.com
Centre for Instrumentation Research,
Department of Electrical Engineering,
Cape Peninsula University of Technology,
P.O. Box 652
,Cape Town 8000
, South Africa
;College of Agriculture, Engineering and Science,
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000
, South Africa
e-mail: kessie.gov@gmail.com
H. McCreadie
College of Agriculture, Engineering, and Science,
School of Chemistry and Physics,
e-mail: Mccreadie@ukzn.ac.za
School of Chemistry and Physics,
University of KwaZulu-Natal
,Private Bag X54001
,Durban 4000,
South Africa
e-mail: Mccreadie@ukzn.ac.za
1Corresponding author.
Manuscript received February 29, 2012; final manuscript received January 31, 2013; published online April 12, 2013. Assoc. Editor: Mark R. Duignan.
J. Fluids Eng. Jun 2013, 135(6): 061303 (13 pages)
Published Online: April 12, 2013
Article history
Received:
February 29, 2012
Revision Received:
January 31, 2013
Citation
Mukaro, R., Govender, K., and McCreadie, H. (April 12, 2013). "Wave Height and Wave Velocity Measurements in the Vicinity of the Break Point in Laboratory Plunging Waves." ASME. J. Fluids Eng. June 2013; 135(6): 061303. https://doi.org/10.1115/1.4023659
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