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Wave- and current-dominated combined orthogonal flows over fixed rough beds
Continental Shelf Research ( IF 2.3 ) Pub Date : 2021-03-19 , DOI: 10.1016/j.csr.2021.104403
Carla Faraci , Rosaria Ester Musumeci , Massimiliano Marino , Alessia Ruggeri , Lilia Carlo , Bjarne Jensen , Enrico Foti , Giuseppe Barbaro , Bjorn Elsaßer

Orthogonal wave-current interaction often occurs in coastal regions, when waves approach the shoreline near-orthogonally and longshore currents are present. Notwithstanding its wide relevance, this phenomenon is far from being understood to a full extent, especially in the presence of bed roughness. Indeed the effects on the apparent roughness due to the combination of steady currents and surface waves propagating at right angles are still a matter of debate, both in the current and in the wave dominated cases.

To this aim, the hydrodynamic effects of an orthogonal regular wave on a current propagating over a rough bed were investigated; two different rough beds, one sandy and one made of gravel, were considered. Both surface elevation and velocity profiles were acquired by means of an array of wave gauges and Micro Acoustic Doppler Velocimeters positioned within the tank. Here the range of the investigated parameters was significantly enlarged with respect to the existing literature studies.

The present paper focuses on the analysis of the mean velocity profiles. More specifically, observation of velocity profiles shows that the current to wave velocity ratio and the bed roughness play an important role, by impacting the value of the apparent roughness. Indeed it was found that as far as the flow is current dominated the addition of waves on the current increases the flow resistance. The opposite happens when the flow is wave dominated, irrespective of the bed roughness type. In particular, the apparent roughness increases as far as the wave plus current to current only friction velocity ratio increases. The increase is more rapid if the wave plus current prevails on the current only friction velocity.



中文翻译:

固定粗糙床上波和电流为主的正交流

正交波流相互作用经常发生在沿海地区,当波浪以近正交的方式接近海岸线且存在近岸流时。尽管它具有广泛的相关性,但仍未完全了解这种现象,尤其是在床面粗糙的情况下。实际上,无论是在稳定电流还是在以波浪为主的情况下,由于稳定​​电流和直角传播的表面波的结合,对表面粗糙度的影响仍然是一个争论的问题。

为了这个目的,研究了正交规则波对在粗糙床上传播的电流的流体动力作用。考虑了两张不同的粗糙床,一张是沙质床,另一张是砾石床。表面高度和速度剖面都是通过位于水箱内的一系列波谱仪和微声多普勒测速仪获得的。在此,相对于现有文献研究,所研究参数的范围显着扩大。

本文着重于平均速度分布图的分析。更具体地,对速度分布的观察表明,通过影响表观粗糙度的值,电流波速比和床的粗糙度起着重要的作用。实际上,已经发现,就电流而言,在电流上占主导地位的是,在电流上增加波会增加流动阻力。相反,当流动以波浪为主时,与床的粗糙度类型无关。特别地,表观粗糙度随着波加电流对电流的仅摩擦速度之比的增加而增加。如果波浪加电流仅作用于当前的摩擦速度,则增加会更快。

更新日期:2021-03-31
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