Reynolds Stress in Surf Zone

Abstract

The on-offshore and the vertical components u, w of the velocity in a surf zone on a uniformly sloping beach in a wave tank were measured simultaneously with a laser-doppler velocimeter under two conditions.The time variation of the Reynolds stress -u'w' during one wave period is discussed.The Reynolds stress behaves as that in the oscillatory pipe flow does.The magnitude of the terms including the Reynolds stress terms in the on-offshore momentum equation is estimated.The Reynolds stress terms does not play any important role in the on-offshore momentum transfer during one wave period in the surf zone.

Investigation of Turbulence in a Plunging Breaking Wave

“…The results obtained from the calculation of the Reynolds stresses in the present study are in good agreement with the results of Sakai et al [ 12 ] for the plunging breaker. They measured the flow velocities of the breaking waves on a bed with a slope of 1 : 20, with a wave period of 1.82 s. According to the results, Reynolds stresses reache maximum value when the ensemble-averaged flow decreases.…”

“…This can be done by estimating the magnitude of each term using experimental data. Sakai et al [ 12 ] established that the local acceleration term was several orders of magnitude larger than other terms in the equation. The actual order depended on time.…”

“…The main conclusion was that the turbulent wave theory does not give a reasonable answer to the variation of Reynolds stress in the surf zone and more investigations are needed. Later, Sakai et al [ 12 ] found that the magnitude of the Reynolds stress term in the on-offshore momentum equation during one wave period is small compared with the local acceleration and convection terms.…”

Velocity Field under Plunging Waves

“…The velocity field there is rather complicated because of its non-uniformities in time and space. However, with the recent development of the velocity measurement techniques, many researches have been carried out to clarify the structure of the turbulent velocity field in the surf zone by measuring the velocity itself [Sakai et al(1984), Aono and Hattori (1984), Nadaoka et al(1986) and Mizuguchi (1986)]. Svendsen et al(1978) separated the surf zone into three regions which were an outer, inner and run-up region.…”

Velocity Field Under Plunging Waves

“…The velocity field there is rather complicated because of its non-uniformities in time and space. However, with the recent development of the velocity measurement techniques, many researches have been carried out to clarify the structure of the turbulent velocity field in the surf zone by measuring the velocity itself [Sakai et al(1984), Aono and Hattori (1984), Nadaoka et al(1986) and Mizuguchi (1986)]. Svendsen et al(1978) separated the surf zone into three regions which were an outer, inner and run-up region.…”