The wake of a three-dimensional underwater obstacle: Effect of bottom boundary conditions

Puthan, Pranav; Jalali, Masoud; Ortiz-Tarin, Jose Luis; Chongsiripinyo, Karu; Pawlak, Geno; Sarkar, Sutanu

doi:10.1016/j.ocemod.2020.101611

Cited by 13 publications

(10 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Possible mixing mechanisms are therefore to some extent breaking internal lee waves due to flow over bathymetric features, but more importantly, lee vortices or wake eddies due to flow around them and nonlinear hydraulic effects due to topographic blocking. Our observations show similarities to model studies of wake eddies from Puthan et al (2020 and, carried out at a topographic Froude number of 0.2 and 0.15, respectively but for a single hill and at a much larger Rossby number where rotation is less important. Puthan et al (2022) pointed out that consistently higher dissipation rates are observed inside the thin hydraulic jet evolving at the apex of an obstacle for low Fr (see their figure 7).…”

Section: Mixing Mechanismssupporting

confidence: 76%

Diapycnal Mixing Induced by Rough Small-Scale Bathymetry

Muchowski

Arneborg

Umlauf

et al. 2022

Preprint

View full text Add to dashboard Cite

We investigate the effect of extremely rough bathymetry on energy dissipation and mixing in a coastal region characterized by small-scale seafloor features penetrating a strongly-stratified density interface of comparable vertical scale. Our data from the non-tidal Baltic Sea include shear microstructure measurements and observations from a broadband echosounder, here used to resolve the extreme variability and intermittency of stratified turbulence in the vicinity of obstacles. Scale analysis and acoustic imaging of small-scale turbulent motions suggest that the underlying mixing mechanisms are related to topographic wake eddies and, to a smaller extent, to breaking internal waves near the bathymetric features. Vertical diffusivities exceed those at a nearby reference station with smooth bathymetry by up to two orders of magnitude. Our study emphasizes the importance of rough small-scale (< 1 km) bathymetric features for energy dissipation and vertical turbulent transport in coastal areas shaped by e.g., glacial, tectonic, or volcanic processes.

show abstract

Section: Mixing Mechanismssupporting

confidence: 76%

Diapycnal Mixing Induced by Rough Small-Scale Bathymetry

Muchowski

Arneborg

Umlauf

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…In the absence of tidal flow, the body-generated lee waves are steady at Froude numbers of O(0.1) as shown in experiments (Dalziel et al, 2011;Hunt & Snyder, 1980) and numerical simulations (Ding et al, 2003;Puthan et al, 2020). However, tidal oscillation leads to transient lee waves (Bell, 1975).…”

Section: Overall Flow Characteristicsmentioning

confidence: 90%

Tidal Synchronization of Lee Vortices in Geophysical Wakes

Puthan

Sarkar

Pawlak

2021

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

Wake vortices in tidally modulated currents past a conical hill in a stratified fluid are investigated using large‐eddy‐simulation. The vortex shedding frequency is altered from its natural steady‐current value leading to synchronization of wake vortices with the tide. The relative frequency (f*), defined as the ratio of natural shedding frequency (fs,c) in a current without tides to the tidal frequency (ft), is varied to expose different regimes of tidal synchronization. When f* increases and approaches 0.25, vortex shedding at the body changes from a classical asymmetric Kármán vortex street. The wake evolves downstream to restore the Kármán vortex‐street asymmetry but the discrete spectral peak, associated with wake vortices, is found to differ from both ft and fs,c, a novel result. The spectral peak occurs at the first subharmonic of the tidal frequency when 0.5 ≤ f* < 1 and at the second subharmonic when 0.25 ≤ f* < 0.5.

show abstract

“…To quantitatively compare the two cases, instantaneous ɛ * is integrated in the y * = 0 plane from z * = 0 to 1 and plotted along the streamwise direction in Figures 5e and 5f. In the near wake (0 < x * < 2), the dissipation rate remains elevated in both cases, with vertical shear (Puthan et al., 2020) being a major contributor. However, the integrated dissipation rate is 3 times larger at R = 1 compared to R = 0.05 in the near wake.…”

Section: Downstream Dissipation Ratementioning

confidence: 96%

“…The flow is illustrated with instantaneous snapshots of the velocity field in the midcenter plane (Figure 1a) and vertical vorticity in the horizontal plane (Figure 1b). The flow features such as transient lee waves (Jalali & Sarkar, 2017; Jalali et al., 2014; Legg & Klymak, 2008), downstream wake (Dong et al., 2006; Perfect et al., 2020a; Puthan et al., 2020), blocked fluid upstream (Baines, 1987, 1995), and coherent lee vortices (Perfect et al., 2018; Puthan et al., 2021) are prominent. These features must be resolved in simulations to quantify the contribution from the turbulent processes accurately.…”

Section: Computational Modelmentioning

confidence: 99%

Wake Vortices and Dissipation in a Tidally Modulated Flow Past a Three‐Dimensional Topography

2022

Self Cite

View full text Add to dashboard Cite

there is direct wave breaking at the ridge with enhanced turbulence dissipation at the seafloor while at topographies with shallow slopes like Brazil Basin, wave-wave interactions cascade energy to high wave numbers, and ultimately to turbulence (e.g., St. Laurent & Garrett, 2002). Recent measurements of MacKinnon et al. (2019) andVoet et al. (2020) show significant energy loss associated with vertically sheared wake eddies at the northern end of the Palau island

show abstract

The wake of a three-dimensional underwater obstacle: Effect of bottom boundary conditions

Cited by 13 publications

References 52 publications

Diapycnal Mixing Induced by Rough Small-Scale Bathymetry

Diapycnal Mixing Induced by Rough Small-Scale Bathymetry

Tidal Synchronization of Lee Vortices in Geophysical Wakes

Wake Vortices and Dissipation in a Tidally Modulated Flow Past a Three‐Dimensional Topography

Contact Info

Product

Resources

About