Study of turbulent eddies for wave against current

• Published in: Ocean engineering Vol. 150; pp. 176 - 193
• Main Authors: Roy, Sayahnya, Samantaray, Sidhartha Sankar, Debnath, Koustuv
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.02.2018
• Subjects: Against wave; Eddies; Joint pdf; pdf; Reynolds stress; Wavelet analysis; Reynolds stress; Wavelet analysis; pdf; Eddies; Joint pdf; Against wave
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2017.12.059

This paper shows the behaviour of different eddy scales that are modulated by the various frequencies of the superimposed wave acting against the current flow. It is observed that the mean velocity near the surface increases due to surface wave acting against current compared to the mean velocity of the only current flow. Moreover, flow under the influence of the higher frequency waves results in larger scale velocity fluctuations when compared to the lower frequency waves. The effect of the superimposed wave is more pronounced for velocity fluctuations in the vertical direction compare to that of the stream-wise direction. The peak value of the probability density function (pdf) of vertical velocity fluctuation decreases logarithmically with the increase in the elevation of the bed. Interestingly, the frequency of the superimposed waves is the major parameter in modulating the eddy scales. Further, it is observed that the frequency of the large-scale energy containing eddies obtained from the wavelet transform is similar to that of the frequency of the superimposed wave itself even after removal of wave potential component in the random velocity signal. •The Reynolds stress is maximum near the bed and gradually reduces towards the water surface.•The extreme value of stream-wise pdf decays logarithmically as a function of wave frequency.•The high-frequency wave has a greater effect on the joint probability density function.•The scale of eddies increases near the surface due to the superimposed surface waves.