Showing papers on "Secondary circulation published in 2013"

Large-Eddy Simulations of Surface Heterogeneity Effects on the Convective Boundary Layer During the LITFASS-2003 Experiment

Abstract: We investigate the impact of observed surface heterogeneities during the LITFASS-2003 experiment on the convective boundary layer (CBL). Large-eddy simulations (LES), driven by observed near-surface sensible and latent heat fluxes, were performed for the diurnal cycle and compare well with observations. As in former studies of idealized one- and two-dimensional heterogeneities, secondary circulations developed that are superimposed on the turbulent field and that partly take over the vertical transport of heat and moisture. The secondary circulation patterns vary between local and roll-like structures, depending on the background wind conditions. For higher background wind speeds, the flow feels an effective surface heat-flux pattern that derives from the original pattern by streamwise averaging. This effective pattern generates a roll-like secondary circulation with roll axes along the mean boundary-layer wind direction. Mainly the upstream surface conditions control the secondary circulation pattern, where the fetch increases with increasing background wind speed. Unlike the entrainment flux that appears to be slightly decreased compared to the homogeneously-heated CBL, the vertical flux of sensible heat appears not to be modified in the mixed layer, while the vertical flux of latent heat shows different responses to secondary circulations. The study illustrates that sufficient time averaging and ensemble averaging is required to separate the heterogeneity-induced signals from the raw LES turbulence data. This might be an important reason why experiments over heterogeneous terrain in the past did not give any clear evidence of heterogeneity-induced effects.

Effects of Vertical Shears and Midlevel Dry Air on Tropical Cyclone Developments

Abstract: A set of idealized experiments using the Weather Research and Forecasting model (WRF) were designed to investigate the impacts of a midlevel dry air layer, vertical shear, and their combined effects on tropical cyclone (TC) development. Compared with previous studies that focused on the relative radial position of dry air with no mean flow, it is found that the combined effect of dry air and environmental vertical shear can greatly affect TC development. Moreover, this study indicates the importance of dry air and vertical shear orientations in determining the impact. The background vertical shear causes the tilting of an initially vertically aligned vortex. The shear forces a secondary circulation (FSC) with ascent (descent) in the downshear (upshear) flank. Hence, convection tends to be favored on the downshear side. The FSC reinforced by the convection may overcome the shear-induced drifting and “restore” the vertical alignment. When dry air is located in the downshear-right quadrant of the ini...

Dynamics of upwelling in the Alaskan Beaufort Sea and associated shelf–basin fluxes

Abstract: Data from a high-resolution mooring array deployed across the Alaskan Beaufort shelfbreak and slope, together with an idealized numerical model, are used to investigate the dynamics of wind-driven upwelling and the magnitude of the resulting shelf–basin exchange. The analysis focuses on a single storm event in November 2002 when the sea-ice concentration was 50–70%. The normally eastward-flowing shelfbreak jet was reversed to the west, and the secondary circulation near the shelfbreak was characterized by offshore flow in the upper layer and a nearly equal amount of onshore flow at depth. Ekman theory accurately predicts the strength of the secondary circulation when one takes into account the ice–ocean stress. The depth-integrated alongstream momentum balance reveals that, near the shelf edge, the reversed jet is driven by a combination of the surface stress and divergence of cross-stream momentum flux. The reversed jet is primarily spun-down – before the winds subside – by the alongstream pressure gradient that likely results from the variation in sea surface height. The shelf–basin fluxes of heat, freshwater, and nitrate resulting from the storm are substantial. Much of the yearly supply of heat to the Beaufort shelf from the inflowing Pacific water through Bering Strait was fluxed offshore, and the amount of freshwater transported into the basin represents a substantial fraction of the year-to-year variation in the freshwater inventory of the Beaufort Gyre. The on-shelf flux of nitrate from 4 to 5 such storms could account for most of the net annual primary production that occurs on the Beaufort shelf.

The structure of sidewall boundary layers in confined rotating Rayleigh-Bénard convection

Abstract: Turbulent rotating convection is usually studied in a cylindrical geometry, as this is its most convenient experimental realization. In our previous work (Kunnen et al., J. Fluid Mech., vol. 688, 2011, pp. 422–442) we studied turbulent rotating convection in a cylinder with the emphasis on the boundary layers. A secondary circulation with a convoluted spatial structure has been observed in mean velocity plots. Here we present a linear boundary-layer analysis of this flow, which leads to a model of the circulation. The model consists of two independent parts: an internal recirculation within the sidewall boundary layer, and a bulk-driven domainfilling circulation. Both contributions exhibit the typical structure of the Stewartson boundary layer near the sidewall: a sandwich structure of two boundary layers of typical thicknesses E1=4 and E1=3, where E is the Ekman number. Although the structure of the bulk-driven circulation may change considerably depending on the Ekman number, the boundary-layer recirculation is present at all Ekman numbers in the range $0.72\times 10^{-5} \leq E \leq 5.76 \times 10^{-5}$ considered here.

An examination of two pathways to tropical cyclogenesis occurring in idealized simulations with a cloud-resolving numerical model

Abstract: . Simulations are conducted with a cloud-resolving numerical model to examine the transformation of a weak incipient mid-level cyclonic vortex into a tropical cyclone. Results demonstrate that two distinct pathways are possible and that development along a particular pathway is sensitive to model physics and initial conditions. One pathway involves a steady increase of the surface winds to tropical cyclone strength as the radius of maximum winds gradually decreases. A notable feature of this evolution is the creation of small-scale lower tropospheric cyclonic vorticity anomalies by deep convective towers and subsequent merger and convergence by the low-level secondary circulation. The second pathway also begins with a strengthening low-level circulation, but eventually a significantly stronger mid-level circulation develops. Cyclogenesis occurs subsequently when a small-scale surface concentrated vortex forms abruptly near the center of the larger-scale circulation. The small-scale vortex is warm core throughout the troposphere and results in a fall in local surface pressure of a few millibars. It usually develops rapidly, undergoing a modest growth to form a small tropical cyclone. Many of the simulated systems approach or reach tropical cyclone strength prior to development of a prominent mid-level vortex so that the subsequent formation of a strong small-scale surface concentrated vortex in these cases could be considered intensification rather than genesis. Experiments are performed to investigate the dependence on the inclusion of the ice phase, radiation, the size and strength of the incipient mid-level vortex, the amount of moisture present in the initial vortex, and the sea surface temperature. Notably, as the sea surface temperature is raised, the likelihood of development along the second pathway is increased. This appears to be related to an increased production of ice. The sensitivity of the pathway taken to model physics and initial conditions revealed by these experiments raise the possibility that the solution to this initial value problem is near a bifurcation point. Future improvements to model parameterizations and more accurate observations of the transformation of disturbances to tropical cyclones should clarify the conditions that favor a particular pathway when starting from a mid-level vortex.

Joint Impact of Forecast Tendency and State Error Biases in Ensemble Kalman Filter Data Assimilation of Inner-Core Tropical Cyclone Observations

Abstract: In this study the properties and causes of systematic errors in high-resolution data assimilation of inner-core tropical cyclone (TC) observations were investigated using the Hurricane Weather Research and Forecasting (HWRF) Ensemble Data Assimilation System (HEDAS). Although a recent study by Aksoy et al. demonstrated overall good performance of HEDAS for 83 cases from 2008 to 2011 using airborne observations from research and operational aircraft, some systematic errors were identified in the analyses with respect to independent observation-based estimates. The axisymmetric primary circulation intensity was underestimated for hurricane cases and the secondary circulation was systematically weaker for all cases. The diagnostic analysis in this study shows that the underestimate of primary circulation was caused by the systematic spindown of the vortex core in the short-term forecasts during the cycling with observations. This tendency bias was associated with the systematic errors in the secondary circulation, temperature, and humidity. The biases were reoccurring in each cycle during the assimilation because of the inconsistency between the strength of primary and secondary circulation during the short-term forecasts, the impact of model error in planetary boundary layer dynamics, and the effect of forecast tendency bias on the background error correlations. Although limited to the current analysis the findings in this study point to a generic problem of mutual dependence of short-term forecast tendency and state estimate errors in the data assimilation of TC core observations. The results indicate that such coupling of errors in the assimilation would also lead to short-term intensity forecast bias after the assimilation for the same reasons.

Impact of sea surface temperature front on stratus-sea fog over the Yellow and East China Seas — a case study with implications for climatology

Abstract: A stratus-sea fog event that occurred over the Yellow and East China Seas on 3 June 2011 is investigated using observations and a numerical model, with a focus on the effects of background circulation and Sea Surface Temperature Front (SSTF) on the transition of stratus into sea fog. Southerly winds of a synoptic high-pressure circulation transport water vapor to the Yellow Sea, creating conditions favorable for sea fog/stratus formation. The subsidence from the high-pressure contributes to the temperature inversion at the top of the stratus. The SSTF forces a secondary circulation within the ABL (Atmospheric Boundary Layer), the sinking branch of which on the cold flank of SSTF helps lower the stratus layer further to reach the sea surface. The cooling effect over the cold sea surface counteracts the adiabatic warming induced by subsidence. The secondary circulation becomes weak and the fog patches are shrunk heavily with the smoothed SSTF. A conceptual model is proposed for the transition of stratus into sea fog over the Yellow and East China Seas. Finally, the analyses suggest that sea fog frequency will probably decrease due to the weakened SSTF and the reduced subsidence of secondary circulation under global warming.

Flow and suspended-sediment transport in the Colorado River near National Canyon

Abstract: Point measurements of flow speed and suspended-sand concentration were made from a cableway 293-km downstream from Glen Canyon Dam during the 1996 controlled flood. The data demonstrate a systematic fining of the suspended load in the Colorado River, a reduction in near-bed sand concentration with time, and a strong secondary circulation that very effectively transported suspended sand toward the channel margins. In the center of the river, the primary flow was well represented by steady, horizontally uniform flow theory, with a shear velocity of 0.081 m/s and a sand grain related roughness parameter of 4.5.10 -6 m; at the channel margins the primary flow exhibited a distinct internal boundary layer with a shear velocity of approximately 0.081 m/s and an outer boundary layer with a shear velocity of approximately twice that value. The secondary circulation was caused by long wavelength irregularities in the rockfall-produced sloping banks of the approximately trapezoidal channel. The primary flow was forced upward and toward the river center by these topographic features causing a fully 3-dimensional circulation. The upward forced vertical velocities apparently interacted with turbulence in the primary flow to produce boils. Consequently, the upwelling zone degraded to an irregular, bank-parallel boil line. Downwelling occurred over a broad region in the center of the river, but also was concentrated along well-defined convergence zones over which woody debris concentrated. This secondary circulation was very effective in transporting suspended sand toward the channel margins at the bottom, then lifting it in the boils and depositing it inshore of the boil line on the riverbanks.

Nonlinear stratified spindown over a slope

Abstract: Nonlinear stratified spindown of an along-isobath current over an insulated slope is shown to develop asymmetries in the vertical circulation and vertical relative vorticity field. During spindown, cyclonic vorticity is weakened to a greater extent than anticyclonic vorticity near the boundary because of buoyancy advection. As a consequence, Ekman pumping is weakened over Ekman suction. Momentum advection can weaken Ekman pumping and strengthen Ekman suction. Time-dependent feedback between the geostrophic flow and the frictional secondary circulation induces asymmetry in cyclonic and anticyclonic vorticity away from the boundary. Buoyancy advection over a slope can modify the secondary circulation such that anticyclonic vorticity decays faster than cyclonic vorticity outside the boundary layer. In contrast, momentum advection can cause cyclonic vorticity to spin down faster than anticyclonic vorticity. A scaling and analytical solutions are derived for when buoyancy advection over a slope can have a more significant impact than momentum advection on these asymmetries. In order to test this scaling and analytical solutions, numerical experiments are run in which both buoyancy and momentum advection are active. These solutions are contrasted with homogeneous or stratified spindown over a flat bottom, in which momentum advection controls the asymmetries. These results are applied to ocean currents over continental shelves and slopes.

Study on the Angular Momentum of Axisymmetric Tropical Cyclone in the Developing Stage

Abstract: The angular momentum transport of an idealized axisymmetric vortex in the developing stage was investigated using the Weather Research and Forecast (WRF) model. The balanced axisymmetric vortex was constructed based on an empirical function for tangential wind, and the temperature, geopotential, and surface pressure were obtained from the balanced equation. The numerical simulation was carried out for 6 days on the f-plane with the Sea Surface Temperature (SST) set as constant. The weak vortex at initial time was intensified with time, and reached the strength of tropical cyclone in a couple of days. The Absolute Angular Momentum (AAM) was transported along with the secondary circulation of the vortex. Total AAM integrated over a cylinder of radius of 2000 km decreased with simulation time, but total kinetic energy increased rapidly. From the budget analysis, it was found that the surface friction is mainly responsible for the decrease of total AAM. Also, contribution of the surface friction to the AAM loss was about 90% while that of horizontal advection was as small as 8%. The trajectory of neutral numerical tracers following the secondary circulation was presented for the Lagrangian viewpoint of the transports of absolute angular momentum. From the analysis using the trajectory of tracers it was found that the air parcel was under the influence of the surface friction continuously until it leaves the boundary layer near the core. Then the air parcel with reduced amount of angular momentum compared to its original amount was transported from boundary layer to upper level of the vortex and contributed to form the anti-cyclone. These results suggest that the tropical cyclone loses angular momentum as it develops, which is due to the dissipation of angular momentum by the surface friction.

Numerical modeling of quasi-two-dimensional vortices in the atmosphere over the Black Sea

Abstract: We consider quasi-two-dimensional rapidly dissipating mesoscale atmospheric vortices generated over the Black Sea near the Crimean and Caucasian coasts. Based on the results of numerical modeling for a characteristic example of the Crimean eddy, we determine its structure and parameters and estimate the rate of decay of kinetic energy and enstrophy. In addition to the large-scale secondary circulation in the vortex, we also consider a small-scale secondary circulation induced by Raleigh-Benard convection.

Observations of Secondary Circulation Around Curved Open Channels and Coastal Headlands

Abstract: In three dimensions when water flows around a bend, instead of flowing straight, it spirals around the bend in a loose helical pattern. This pattern is commonly known as secondary circulation or secondary flow. The driving forces behind curvature induced secondary circulation are a stream-wise velocity shear due to bottom friction and centripetal acceleration. The velocity shear decreases the velocity towards the bottom resulting in an imbalance in the centripetal acceleration. This drives the flow radially outwards near the surface, and radially inwards near the bottom, creating a loose helical flow pattern around the curve. Secondary circulation plays an important role in nature, this includes mixing, erosion and formation of banks in rivers and estuaries, and localized up-welling at coastal headlands. Observations from the curved tidal channel of the Otago Harbour show secondary flows up to 20 % of the primary flow and vertical velocity inferred from secondary flow that is up to 1% of the primary flow. Linear regression shows the cross-channel distribution of the observed secondary flow can be resolved from the horizontal ADCP measurements well enough to be able to infer the vertical velocity using mass continuity, rp = 0.95. The pattern of this vertical velocity is upwards on the inside and downwards on the outside of the curve. Observed around the curved tidal channel is the radially outwards movement of the depth averaged velocity maxima due to advective momentum transport and this movement is contrasted between the flood and ebb tide. Observations from a sharper curvature bend in the Clutha river delta show flattening and deformation of the vertical profile of the primary flow due to the advection of momentum by secondary circulation and associate a counter rotating outer-bank cell of secondary circulation with this deformation. A visual explanation for this outer bank cell is proposed, based around the forces of plane equilibrium and the deformation of the vertical profile of the primary flow. At Cape Saunders, a coastal headland, the vertical velocity inferred from horizontal ADCP measurements show a significant localized up-welling synchronized with the tidal cycle of up to 0.007 ms−1. Concurrent CTD measurements show up-welling of up to 0.002 ms−1 are correlated with the vertical velocity inferred from secondary flow, rp = 0.65, supporting the concept of inferring vertical velocity from the horizontal measurements. This up-welling equates to ≈ 7 m per hour meaning the entire water column is replacing itself with nutrient rich deep waters at least once during a tidal cycle.

A Discussion on the East Asian Winter Monsoon Index—Differences between the East Asian Winter Monsoon at Mid-high and Low Latitudes

Abstract: The National Centers for Environmental Prediction (NCEP) reanalysis data and the National Oceanic and Atmospheric Administration (NOAA) Extended Reconstructed Sea Surface Temperatures (SSTs) are used in this study to investigate characteristics of the East Asian winter monsoon (EAWM) at various latitude zones. On the basis of two indices describing the strengths of the low-latitudinal EAWM (EAWM-L) and mid latitudinal EAWM (EAWM-M), theirvariation characteristics, associated atmospheric circulation, and related SST patterns are examined. The results indicate that although both the EAWM-M and EWAM-L indices can reflect the intensity of the EAWM, the atmospheric circulation associated with the two indices is clearly distinct. In the lower troposphere, the EAWM-L is closely related to anomalous circulation around the South China Sea and the Philippines, while the EAWM-M presents a closer relationship with the circulation adjacent to Lake Baikal, known as the Baikal blocking high. In the middle troposphere, the close relationship of EAWM-M and the Baikal blocking high remains persistent, while the EAWM-L has a relatively closer linkage with a major Asian trough. In the upper troposphere, variation in the intensity of a subtropical westerly jet may modulate secondary circulation and is eventually linked with the EAWM-L index, while the variation of EAWM-M is mainly related to a shift of the north boundary of the westerly jet. In addition, the EAWM-L is significantly correlated with SSTs in the central and eastern equatorial Pacific and that in the tropical Indian Ocean, while the EAWM-M has a closer relationship with the latter than with the former. The close relationships of the EAWM-L with the central and eastern equatorial Pacific and with the tropical Indian Ocean are clearly revealed on interannual and interdecadal scales; however, the significant linkage of the EAWM-M with the tropical Indian Ocean exists mainly on the interdecadal scale.

Turbulence in the wake of a roughness patch

Abstract: Little research was done in the past concerning the propagation of three dimensional effect in shallow wake flow caused by a roughness patch. Today’s research on related subjects is dominated by emerging obstructions in shallow water where the flow can be assumed as (quasi) two dimensional. However the relevance of a submerged obstruction with increased roughness can be found in wake control, oyster reefs, river- and estuary bottoms and heterogeneous land occupancy. To get a better understanding of the consequences of the three dimensionality of the flow structures, experiments are performed in a wide shallow flume to examine these structures. The main objective is to examine whether the wake structure of a roughness patch can be treated as (quasi)-two-dimensional. The objective has been answered by a combination of a literature study and an experiment performed at the faculty’s laboratory. The results show four dominant mechanisms in the wake of a roughness patch: transverse mass flux, bottom friction, mixing layer and the secondary circulation. Based on a momentum balance the transverse mass flux and the bottom friction are the largest contributions to this balance. Although the contribution of the mixing layer and the secondary circulation to the recovery of the wake are of the order of 10%, their influence on the flow structure is more pronounced. The mixing layer is shifted towards the wake centerline due to the presence of a transverse mass flux forming a misalignment between the maximum spanwise Reynolds stress and the position of the wake half width. Since this shift is of limited influence on the position of the secondary circulation, a misalignment if formed between the maximum momentum transport by the secondary circulation and the mixing layer causing a lower streamwise velocity at the edge of wake with respect to the wake of an emerging obstruction. The secondary circulation is responsible for the transport of low momentum fluid towards the edge of the wake near the bottom, and high momentum fluid towards the wake centerline near the surface. This behavior is responsible for the cross gradient in the streamwise velocity profiles as shown by the data obtained. For modeling purposes of well mixed quantities, a (quasi)-two-dimensional approach only holds if the weaker streamwise velocity near the edge of the wake is taken into account. In the case a prediction of depth varying quantities is desired, the cross gradient caused by the secondary circulation needs to be implemented as well which results in the need of a three-dimensional modeling approach.

Numerical simulation of flow and aquaculture organic waste dispersion in a curved channel

Abstract: The dispersion and deposition of particulate organic matter from a fish cage located in an idealized curved channel with a 90° bend are studied for different horizontal grid resolutions. The model system consists of a three-dimensional, random-walk particle tracking model coupled to a terrain-following ocean model. The particle tracking model is a Lagrangian particle tracking simulator which uses the local flow field, simulated by the ocean model, for advection of the particles and random walk to simulate the turbulent diffusion. The sinking of particles is modeled by imposing an individual particle settling velocity. As the homogeneous water flows through the bend in the channel, the results show that a cross-channel secondary circulation is developed. The motion of this flow is similar to a helical motion where the water in the upper layers moves towards the outer bank and towards the inner bank in the lower layers. The intensity of the secondary circulation will depend on the viscosity scheme and increases as the horizontal grid resolution decreases which significantly affects the distribution of the particles on the seabed. The presence of the secondary circulation leads to that most of the particles that settle, settle close to the inner bank of the channel.

Axisymmetrically Tropical Cyclone-like Vortices with Secondary Circulations

Abstract: The secondary circulation of the tropical cyclone (TC) is related to its formation and intensification, thus becomes very important in the studies. The analytical solutions have both the primary and secondary circulation in a three-dimensionally nonhydrostatic and adiabatic model. We prove that there are three intrinsic radiuses for the axisymmetrically ideal incompressible flow. The first one is the radius of maximum primary circular velocity $r_m$. The second one is radius of the primary kernel $r_k>r_m$, across which the vorticity of the primary circulation changes sign and the vertical velocity changes direction. The last one is the radius of the maximum primary vorticity $r_d$, at which the vertical flow of the secondary circulation approaches its maximum, and across which the radius velocity changes sign. The first TC-like vortex solution has universal inflow or outflow. The relations between the intrinsic length scales are $r_k=\sqrt{2}r_m$ and $r_d=2r_m$. The second one is a multi-planar solution, periodically in $z$-coordinate. Within each layer, the solution is a convection vortex. The number of the secondary circulation might be one, two, three, and even more. There are also three intrinsic radiuses $r_m$, $r_k$ and $r_d$, but they have different values. It seems that the relative stronger radius velocity could be easily found near boundaries. The above solutions can be applied to study the radial structure of the tornados, TCs and mesoscale eddies.

Electrothermal film heater performing heating through secondary water circulation

Abstract: An electrothermal film heater performing heating through secondary water circulation is composed of an upper water distribution fastening clamp plate, a lower water distribution fastening clamp plate, an electrothermal film tube, an O-type seal pipe plug, an O-type seal gasket, an upper and lower water distribution tank cover plate, a water and electricity separating tube, a secondary heat water storage tank, an anti-dry-burning controller, a water pressure flow regulation controller, a temperature regulation controller, a secondary heat circulation water inflow solenoid valve, a pressure and temperature control switch, a one-way valve, a secondary circulation water inflow tee, a water inflow solenoid valve, a solenoid valve controller, an water inflow tee, detection controller for pressure, flow and temperature, a computer control circuit and the like The electrothermal film tube and the water and electricity separating tube are non-metallic tubes with transparent ends The electrothermal film tube, the upper water distribution fastening clamp plate and the lower water distribution fastening clamp plate form an water inflow heating passage which is connected with a secondary circulation water heating passage composed of the water and electricity separating tube and the secondary heat water storage tank to form a waste heat secondary circulation recycling system

Deepwater aerating device

Abstract: In order to solve the problems of the existing deepwater aerating device, such as bad return sludge mixing, low oxygen utilization rate and low removal rate of pollution components which are caused by short contact time of sewage and air and short mixing path, the utility model provides a new deepwater aerating device. A circulation flow controller is arranged to set up secondary circulation of the sewage and adjust the circulation water flow, thus the sewage circulation path is lengthened in a zigzag way, the sewage and the air are completely mixed, the oxygen utilization rate and the power efficiency are greatly improved, and the removal rate of BOD and NH3-N in the sewage is furthermore improved. The deepwater aerating device can be smaller, so as to reduce the engineering investment and the operation cost. At the same time, the secondary circulation which is set up by the circulation flow controller forms a certain hypoxia environment, so as to facilitate the denitrification reaction and improve the removal rate of TN in the sewage.

Double-loop three-stage closed type circulation area energy station system

Abstract: Provided is a double-loop three-stage closed type circulation area energy station system. The whole system is in an enclosed type water circulation manner and supplies cold/hot energy to users by means of double loops of a hot source water and a cold source water, wherein the hot source water loop supplies heat to the users and the cold source water loop supplies cool energy to the users. The system completes the processes of energy collection, energy transfer, energy use and energy disposal through the water circulation in three stages, namely, a primary circulation, a secondary circulation, and a tertiary circulation. the primary circulation, also called heat source station circulation, has the effects of bringing extraneous energy, such as underground heat, solar energy, and industrial and civil waste heat to the system and releasing the excess heat in the system into stratigraphic soil; the secondary circulation, also called intermediate transmission circulation, has the effects of transmitting the energy of the heat source station to the users or transmitting the energy discarded by the users to other users or to a ground heat source station; and the tertiary circulation, also called user circulation, has the effects of transferring the energy of the system to an users?? energy consumption site and receiving the energy discarded by the users to the system.

Evolution of secondary cellular circulation flow above submarine bedforms imaged by remote sensing techniques

Abstract: Normalized radar cross section (NRCS) modulation and acoustic Doppler current profiler (ADCP) measurements above submarine sand ribbons and sand waves are presented. The two study areas are located in the Southern Bight of the North Sea at the Birkenfels wreck and in the sand wave field of the Lister Tief in the German Bight of the North Sea. These measurements reveal the developments of secondary cellular circulations in tidally induced coastal sea areas. Secondary circulation cells can develop perpendicular as well as parallel to the direction of the dominant tidal current flow. Circulation cells developed perpendicular to the direction of the dominant tidal current flow are associated with marine sand ribbons manifested near an underwater wreck. Secondary circulation cells within the water column observed parallel to the direction of the dominant tidal current flow have been initiated during flood and ebb tidal current phases associated with submarine sand waves. These two types of cellular circulations must obey the Hamiltonian principle of classical mechanics. The current–short surface wave interaction is described by the action balance or radiation balance-equation based on weak hydrodynamic interaction theory. The calculated current gradient or strain rate of the applied imaging theory has the same order of magnitude for both bedforms such as marine sand ribbons and sand waves, respectively.

Axisymmetrically Tropical Cyclone-like Vortices with Secondary Circulations

Abstract: The secondary circulation of the tropical cyclone (TC) is related to its formation and intensification, thus becomes very important in the studies. The analytical solutions have both the primary and secondary circulation in a three-dimensionally nonhydrostatic and adiabatic model. We prove that there are three intrinsic radiuses for the axisymmetrically ideal incompressible flow. The first one is the radius of maximum primary circular velocity rm. The second one is radius of the primary kernel rk > rm, across which the vorticity of the primary circulation changes sign and the vertical velocity changes direction. The last one is the radius of the maximum primary vorticity rd, at which the vertical flow of the secondary circulation approaches its maximum, and across which the radius velocity changes sign. The first TC-like vortex solution has universal inflow or outflow. The relations between the intrinsic length scales are rk = √ 2rm and rd = 2rm. The second one is a multi-planar solution, periodically in z-coordinate. Within each layer, the solution is a convection vortex. The number of the secondary circulation might be one, two, three, and even more. There are also three intrinsic radiuses rm, rk and rd, but they have different values. It seems that the relative stronger radius velocity could be easily found near boundaries. The above solutions can be applied to study the radial structure of the tornados, TCs and mesoscale eddies.