Publications

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2009
Espa, S, Cenedese A, Mariani M, Carnevale GF.  2009.  Quasi-two-dimensional flow on the polar beta-plane: Laboratory experiments. Journal of Marine Systems. 77:502-510.   10.1016/j.jmarsys.2008.10.015   AbstractWebsite

Geophysical turbulence is strongly affected by the variation of the Coriolis parameter with latitude. This variation results in the so-called beta-effect, which forces energy from small-scales to be transferred preferentially into zonal motions. This effect results in the formation of narrow jet-like zonal flows that dominate the dynamics and act as transport barriers. Here, laboratory experiments are used to reproduce this effect in decaying turbulent flows. An electromagnetic cell is used to generate an initial field of vorticity in a rotating tank. Under conditions of quasigeostrophic flow, the beta-effect is produced by depth variation of the flow instead of variation of the Coriolis parameter. The effects of changing the container geometry and the overall fluid depth on the production of jets are investigated. The results suggest that this laboratory configuration can be used to model jet formation in the oceans and that increasing fluid depth is a practical way to decrease viscous effects. (C) 2008 Elsevier B.V. All rights reserved.

2008
Espa, S, Carnevale GF, Cenedese A, Mariani M.  2008.  Quasi-two-dimensional decaying turbulence subject to the effect. Journal of Turbulence. 9:1-18.   10.1080/14685240802464417   AbstractWebsite

Freely decaying quasi-2D turbulence under the influence of a meridional variation of the Coriolis parameter f ( effect) is experimentally and numerically modelled. The experimental flow is generated in a rotating electromagnetic cell where the variation of f is approximated by a nearly equivalent topographical effect. In the presence of a high effect, the initial disordered vorticity field evolves to form a weak polar anticyclonic circulation surrounded by a cyclonic zonal jet demonstrating the preferential transfer of energy towards zonal motions. In agreement with theoretical predictions, the energy spectrum becomes peaked near the Rhines wave number with a steep fall-off beyond, indicating the presence of a soft barrier to the energy transfer towards larger scales. DNS substantially confirmed the experimental observations.

2007
Dietrich, D, Carnevale GF, Orlandi P.  2007.  Flow over the Mid Adriatic Pit. Nuovo Cimento Della Societa Italiana Di Fisica C-Geophysics and Space Physics. 30:277-290.   10.1393/ncc/i2007-10242-x   AbstractWebsite

The influence of the Mid Adriatic Pit (MAP) on the general circulation of the Adriatic is explored through numerical simulations. The numerical code used is the DieCAST model specifically modified for application to the Adriatic Sea. A ten-year simulation is performed and the ability of the model to capture important features of the Adriatic circulation is demonstrated. A series of numerical experiments on the importance of the MAP on the general circulation is performed. It is demonstrated that the current over the northern flank of the MAP, which flows from the Croatian toward the Italian coast, is primarily a topographic current and that such a current would reverse direction if the gradient of the bathymetry were reversed.

1997
Carnevale, GF, Fuentes OUV, Orlandi P.  1997.  Inviscid dipole-vortex rebound from a wall or coast. Journal of Fluid Mechanics. 351:75-103.   10.1017/s0022112097007155   AbstractWebsite

A vortex approaching a no-slip wall 'rebounds' due to the creation of vorticity at the wall in a viscous boundary layer. Here it is demonstrated that a purely inviscid mechanism can also produce vortex rebound from a slip wall. In inviscid vortex rebound, vortex tube stretching generates the necessary vorticity to allow rebound, eliminating the need for viscous vorticity generation. This vortex stretching mechanism is demonstrated through numerical simulations and laboratory experiments on dipole-vortex rebound from a boundary. In an application to oceanography, numerical simulations of both quasi-geostrophic and shallow water dynamics are used to show that the beta-effect at an eastern boundary can produce this inviscid rebound. Through a series of numerical experiments in which the strength of the beta-effect is varied, a formula for predicting the point of separation of the vortices from the boundary in a dipole-coast collision is deduced. Through simulations, the flux of vorticity and fluid away from the boundary is measured as a function of beta and initial angle of incidence. It is found that, in contrast to viscous vortex rebound, which typically does not produce a flux of material away from the boundary farther than a distance comparable to the initial vortex radius, the beta-induced rebound does carry fluid far from the coast. Laboratory experiments in a rotating tank are used to show that a sloping bottom can also provide an inviscid mechanism for dipole-vortex rebound from the wall of the tank under certain conditions. A relation determining the conditions under which inviscid or viscous processes will dominate in the rebound of the dipole from a boundary is obtained.

1994
Carnevale, GF, Kloosterziel RC.  1994.  Lobe shedding from propagating vortices. Physica D. 76:147-167.   10.1016/0167-2789(94)90256-9   AbstractWebsite

Associated with intense propagating vortices is a separatrix defining a region of fluid that is transported with the vortex. The distortion of this separatrix, under external perturbations, leads to entrainment and detrainment of fluid. The detrained fluid is shed in lobes in the wake of the vortex. Examples of this phenomenon for a propagating monopole and dipole are provided from rotating-tank experiments and numerical simulations.