Vorticity Model Research Articles

Transitioning Science to Practice

ABSTRACTNational security challenges require a new approach to collaborative problem solving to address emergent challenges or opportunities. To effectively address these challenges, development of artificial intelligence (AI) technologies including machine learning (ML) and deep learning (DL), is underway. Advancing AI/ML capabilities requires transdisciplinary research encompassing the fusion of technology and emergent scientific discovery. Achieving this requires a departure from traditional research and development (R&D) methods. New development processes need to support the understanding that research progresses iteratively technology insertion is incremental, and the final capability is evolutionary. We propose a novel systems engineering/research model called the vortical model. The vortical model introduces an iterative framework through which emerging advances in research outcomes are effectively demonstrated and validated for integration, as new capabilities, at varying technology insertion points. Our goal is to facilitate the transfer of knowledge from emerging research for swift, effective integration into the organization's mission capabilities.

A 3-D Viscous Vorticity Model for Predicting Turbulent Flows over Hydrofoils

This research addresses the demand for a computationally efficient numerical tool capable of predicting 3-D turbulent flows over 3-D hydrofoils, a critical step in ultimately addressing marine propeller or turbine performance. The related software development and its applications are conducted by employing the vorticity-based approach known as the viscous vorticity equation (VISVE). In particular, an existing 3-D laminar VISVE solver was modified in order to handle 3-D turbulent flow scenarios. The extension incorporates the k−ω SST model into the 3-D VISVE solver by using the finite volume method (FVM), thereby broadening its application to turbulent flows. The model was then tested in the case of turbulent flows over 3-D hydrofoils. The results were found to not be sensitive to either grid or time step size and to be in very good agreement with those obtained using a Reynolds-averaged Navier–Stokes (RANS) solver. This solver offers distinct advantages, including a significantly reduced computational domain size and reduced computational costs through its vorticity-based approach. Notably, turbulence concentration within boundary layers and free shear flows does not compromise the method’s computational efficiency. The simplified meshing process, which automatically generates the grids based on the number of panels on the hydrofoil, enhances accessibility for researchers and engineers.

A Moist Potential Vorticity Model for Midlatitude Long-Lived Mesoscale Convective Systems over Land

Abstract Mesoscale convective systems (MCSs) bring large amounts of rainfall and strong wind gusts to the midlatitude land regions, with significant impacts on local weather and hydrologic cycle. However, weather and climate models face a huge challenge in accurately modeling the MCS life cycle and the associated precipitation, highlighting an urgent need for a better understanding of the underlying mechanisms of MCS initiation and propagation. From a theoretical perspective, a suitable model to capture the realistic properties of MCSs and isolate the bare-bones mechanisms for their initiation, intensification, and eastward propagation is still lacking. To simulate midlatitude MCSs over land, we develop a simple moist potential vorticity (PV) model that readily describes the interactions among PV perturbations, air moisture, and soil moisture. Multiple experiments with or without various environmental factors and external forcing are used to investigate their impacts on MCS dynamics and mesoscale circulation vertical structures. The result shows that mechanical forcing can induce lower-level updraft and cooling, providing favorable conditions for MCS initiation. A positive feedback among surface winds, evaporation rate, and air moisture similar to the wind-induced surface heat exchange over tropical ocean is found to support MCS intensification. Both background surface westerlies and vertical westerly wind shear are shown to provide favorable conditions for the eastward propagation of MCSs. Last, our result highlights the crucial role of stratiform heating in shaping mesoscale circulation response. The model should serve as a useful tool for understanding the fundamental mechanisms of MCS dynamics.

Quarks species in a cold genesis theory; theoretic implications of a Vortical quark model

By the author’s cold genesis theory (CGT), based on the Galileian relativity, it was argued the possibility to explain the massic spectrum of the elementary particles by two species of preonic quasi-crystalline quarks: A) preonics –formed by basic preons z0(34 me) which form bosonic preons z2(4z0) and zpi(7z0) , and B) quarkonics – formed by 3n preonic quarks (4≥n≥1) (mainly –v- or/and s-quarks) or as crystalline cluster of 7x5 = 35 preonic or quarkonic quarks: (p+;n−) –nucleonic quarks or l±, s±,v± -preonic quarks, or c- or b- quarkonic quarks, (‚charm’, ‚botton’), in two flavors: f=1-of Standard model’s variant and f = 2 –of Souza/CGT’s variant. Because the basic z0-preons are explained as cluster of paired degenerate electrons, the strong forces between quarks and particles can be naturally explained by the existence of a permanent etherono-quantonic vortex around the super-dense kernel of electron generated by etherono-quantonic winds of the quantum vacuum and by an etheronic centripetal force of Magnus type. As consequence, in CGT can be argued a model of‚ gravistar’ having a shell of dark energy but also of photons vortexed around a rotational hard core (HC) of black hole type which –by matter→energy conversion can obtain periodically an antigravitic (pseudo)charge MA, by the releasing of heavy etherons of the destroyed degenerate electrons’ vortices. The antigravitic field of an enough high value of MA, produced by the friction between the surface of an internal hard core (HCi) of HC, of black hole type, and the interior surface of a crystalline shell of current strange cold quarks, HCe, could be –in this case, a natural equivalent of the‚ dilaton’ field considered in the EMD theories.

Why Did the 2017 Kuroshio Large Meander Event Become the Longest in the Past 70 Years?

AbstractThe Kuroshio south of Japan is known to vacillate between a straight and a large meander (LM) path. Since 1950, eight LM events have been observed with different durations. The most recent/on‐going LM started in August 2017 and has become the longest event in record. By analyzing eddy‐resolving sea surface height data and by adopting a wind‐forced linear vorticity model, we demonstrate that the on‐going LM is maintained by an exceptionally stable dynamic state of the Kuroshio Extension (KE) forced by wind stresses across the Pacific basin. The highly‐stable KE system not only minimizes westward eddy perturbations from disrupting the upstream Kuroshio path, its strengthened southern recirculation gyre further helps to anchor the Kuroshio across the Izu Ridge. By contrasting the on‐going event to the 2004–2005 event, we argue that the LM duration is more sensitive to the wind‐forced KE dynamic state than the eastward Kuroshio transport south of Japan.

Forced solitary wave and vorticity with topography effect in quasi-geostrophic modelling

A forced KdV equation including the special topography effect is derived to describe nonlinear long wave and solitary eddy based on the quasi-geostrophic potential vorticity model. We obtain the theoretical solution of the equation and the concrete form of stream function through perturbation theory and multi-scale analysis methods. It is found that the joint effect of weak shear basic flow and topography can change the cyclone and anticyclone structure of eddy, and in the meantime topographic structure affects the East-West propagation direction of solitary wave. Finally, according to the interaction between nonlinear long wave and topography by pseudo spectral numerical method, the topographic height is related to the amplitude, wavelength and wave velocity of the excited wave train, and the topography affects not only the spatial structure of wave, but also the amplitude of wave.

Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions

The global polarization of Λ hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at sNN=2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon's transverse momentum (pT) and rapidity (yCM) for the range of centrality 0–40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20 – 40%) collisions the polarization magnitudes are 〈PΛ〉(%)=6.8±1.3(stat.)±2.1(syst.) for Au+Au and 〈PΛ〉(%)=6.2±0.4(stat.)±0.6(syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D-fluid-dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.

Design and performance of very low head water turbines using a surface vorticity model algorithm

This study explores the numerical optimization of water turbine runner profile performance using a surface vorticity model algorithm. The turbine is designed on a laboratory scale and operates at a net head of 0.09 m, 400 rpm, and a water flow rate of 0.003 m3/s. The initial design of the turbine runner was optimized to minimize losses in the hydrofoil. The optimization algorithm is coded in MATLAB software to obtain the optimal stagger angle that will be used in the water turbine design. Furthermore, design validation was performed using computational fluid dynamics analysis ANSYS CFX to determine the water turbine performance. The settings used in ANSYS CFX include the reference pressure of 1 atm, turbulence model shear stress transport, and inlet boundary conditions using total pressure and static pressure outlet boundary conditions. The computational fluid dynamics analysis reveals that by optimizing the design, the efficiency of the water turbine increases by approximately 2.6%. The surface vorticity model algorithm can be applied to optimize the design of the water turbine runner.

Study of Spatial Orientation of Angular Momentum of z-Magnitude SDSS DR-13 Galaxies with Red Shift 0.50 to 0.53

The spatial orientations of 142,929 SDSS DR-13, z- magnitude galaxies having red shift 0.50 to 0.53 have been analyzed. The main goal of this work is to examine the orientation of the angular momentum of galaxies within the given redshift limit in the framework of three different scenarios 'Hierarchy model', 'Pancake model', and the 'Primordial vorticity model'. By using Godlowskian transformation the two-dimensional data were converted into three-dimensional data (polar and azimuthal angles). The expected isotropy distribution curves were obtained by removing the selection effects and performing a random simulation to generate 107 virtual galaxies by using Matlab 2015a. Three statistical tests of Chi-square, autocorrelation, and Fourier were used to compare the expected isotropic data with observed. The data classified into nine subsamples having each of one magnitude size. In general, the results supported the Hierarchy model. The model advocates random orientations of angular. However, a local anisotropy observed in few subsamples suggested a gravitational tidal interaction between neighboring galaxies, an early-merging process in which the angular momentum vector distorts the initial alignment of nearby galaxies.

Spatial Orientations of Angular Momentum Vectors of Galaxies in Supercluster S [247+040+0029] and Substructures

We present an analysis of spatial orientations of 1331 galaxies in the supercluster S [247+040+0029]. The main goal of this work is to search for a new substructure candidate and examine the orientation of angular momentum in the framework of three different scenarios (hierarchy, pancake, and primordial vorticity models) using “position angle-inclination method”, and to test the dependence on magnitude with the angular momentum orientations and their projections. We identified five substructures studying number density contour map with considerably high concentration of galaxies. Using random simulation method to remove the selection effect on database, we carried out expected isotropic distribution using cosmological principle. We then used three statistical tests: Chi-square, Auto-correlation, and Fourier to identify isotropy between observed and expected isotropic distributions. We varied radius in the range 0.3° to 1.0° to find substructures in supercluster. From this we found five sub-structures when taking radius 0.3° and two substructures for 1.0° radius in the number density counter maps of galaxies. By analyzing the result obtained through statistical tests, we are able to conform that evolution of galaxy in the supercluster and substructures supports “Hierarchy model" giving the angular momentum of galaxies in the large scale structure tends to be oriented random with respect to the reference coordinate system.

Viscous Flow Evolution and Boundary Layer Characteristics during the Head-On Collision of Solitary Waves

Lee, T.-C.; Chang, C.-H., and Tang, C.-J., 2021. Viscous flow evolution and boundary layer characteristics during the head-on collision of solitary waves. Journal of Coastal Research, 37(3), 544–556. Coconut Creek (Florida), ISSN 0749-0208.Viscous shear flow near the bottom during the head-on collision of two solitary waves is investigated using a stream function–vorticity model. Fully nonlinear free-surface conditions are satisfied numerically at every time step. The bottom boundary-layer flow region is locally refined to explore its physical characteristics through detailed vorticity transport in the shear layer beneath the two solitary waves during their collision. Both symmetric and asymmetric head-on collisions are examined and discussed. The wave deformations are compared with the results of other studies for validation, and the fluid mechanisms in the flow field are illustrated with streamline, equivorticity line, path line, and timeline plots to reveal the interaction processes. It is revealed that the wave interaction behaves nonlinearly not only at the free surface but also in the vorticity exchanges near the bottom.

Deep Eastern Boundary Currents: Idealized Models and Dynamics

AbstractConcentrated poleward flows along eastern boundaries between 2- and 4-km depth in the southeast Pacific, Atlantic, and Indian Oceans have been observed, and appear in data assimilation products and regional model simulations at sufficiently high horizontal resolution, but their dynamics are still not well understood. We study the local dynamics of these deep eastern boundary currents (DEBCs) using idealized GCM simulations, and we use a conceptual vorticity model for the DEBCs to gain additional insights into the dynamics. Over most of the zonal width of the DEBCs, the vorticity balance is between meridional advection of planetary vorticity and vortex stretching, which is an interior-like vorticity balance. Over a thinner layer very close to the eastern boundary, a balance between vorticity tendencies due to friction and stretching that rapidly decay away from the boundary is found. Over the part of the DEBC that is governed by an interior-like vorticity balance, vertical stretching is driven by both the topography and temperature diffusion, while in the thinner boundary layer, it is driven instead by parameterized horizontal temperature mixing. The topographic driving acts via a cross-isobath flow that leads to stretching and thus to vorticity forcing for the concentrated DEBCs.

A mechanism for formation of the western North Pacific monsoon trough: nonlinear upscale cascade

Linear and nonlinear barotropic vorticity model frameworks are constructed to understand the formation of the monsoon trough in boreal summer over the western North Pacific. The governing equation is written with respect to specified zonal background flows, and a wave perturbation is prescribed in the eastern boundary. Whereas a uniform background mean flow leads no scale contraction, a confluent background zonal flow causes the contraction of zonal wavelength. Under linear dynamics, the wave contraction leads to the development of smaller scale vorticity perturbations. As a result, there is no upscale cascade. Under nonlinear dynamics, cyclonic (anticyclonic) wave disturbances shift northward (southward) away from the central latitude due to the vorticity segregation process. The merging of small-scale cyclonic and anticyclonic perturbations finally leads to the generation of a pair of large-scale cyclonic and anti-cyclonic vorticity gyres, straddling across the central latitude. The large-scale cyclonic circulation due to nonlinear upscale cascade can be further strengthened through a positive convection-circulation feedback.

The barotropic Rossby waves with topography on the earth’sδ-surface

AbstractThe Rossby solitary waves in the barotropic vorticity model which contains the topography on the earth’sδ-surface is investigated. First, applying scale analysis method, obtained the generalized quasi-geostrophic potential vorticity equation (QGPVE). Using The Wentzel–Kramers–Brillouin (WKB) theory, the evolution equation of Rossby waves is the variable-coefficient Korteweg–de Vries (KdV) equation for the barotropic atmospheric model. In order to study the Rossby waves structural change to exist in some basic flow and topography on theδ-surface approximation, the variable coefficient of KdV equation must be explicitly, Chebyshev polynomials is used to solve a Sturm-Liouville-type eigenvalue problem and the eigenvalue Rossby waves, these solutions show that the parameterδusually plays the stable part in Rossby waves and slow down the growing or decaying of Rossby waves with the parameterβ.

Multidecadal variations in ENSO-Indian summer monsoon relationship at sub-seasonal timescales

Customarily, the strength of the impact of El Nino-Southern Oscillation (ENSO) on Indian summer monsoon is evaluated with respect to the seasonal mean rainfall. As the rainfall occurring over the Indian subcontinent experiences strong variations intraseasonally, the impact of ENSO on these intraseasonal fluctuations is often more important for the agribusiness and economy when contrasted with the seasonal mean. The annual cycle of ISM rainfall peaks during July and August months. In this study, we investigate the impact of ENSO on ISM precipitation during July and August. We show that the relationship between ENSO and ISM rainfall during July and August has experienced significant changes at multidecadal timescales. While the impact of ENSO was significantly strong in August and significantly weak in July during 1948–1980, post-1980s August shows a weak ENSO-Monsoon relationship than that in July. We investigate these multidecadal changes in the ENSO-monsoon relationship using 68 years of observational records. ENSO produces strong (weak) upper tropospheric divergence over equatorial eastern Pacific Ocean in August (July) before 1980. A stronger divergence helps Rossby wave within the Pacific-Asian jet cools the upper tropospheric mid-latitude region by modulating the vorticity there. A colder mid-latitude temperature weakens the Indian summer monsoon. Thus, the impact of ENSO on the Indian summer monsoon was weaker (stronger) in July (August) before 1980 and vice versa after the 1980s. Further, we deploy a linear barotropic vorticity model to assess the association between upper tropospheric divergence over the Pacific Ocean region and vorticity (temperature) over the mid-latitude Asian region. A stronger forcing of divergence in the upper tropospheric Pacific region reinforces stronger positive vorticity in mid-latitude Asia resembling the findings above. Our study suggests that these multidecadal fluctuations in the sub-seasonal ENSO-monsoon relationship is linked to the physical changes in the state of the climate and could not be attributed to the stochastic processes. Such insight into the variability in ENSO-monsoon relationship at sub-seasonal timescales would help predictability and decision-making.

Dynamics of Deep Ocean Eastern Boundary Currents

AbstractThe long‐standing paradigm for the large‐scale time‐averaged ocean circulation in the world oceans includes intensified currents at the western boundary, and a much slower interior flow elsewhere. However, poleward deep boundary currents in the eastern limits of the deep South Pacific, Atlantic, and Indian Oceans have been observed repeatedly at 2‐ to 4‐km depth. They carry up to a third of the total deep ocean transports, implying a significant role in climate, yet their dynamics are still not well understood. Here we develop a theoretical understanding for these currents, using a hierarchy of realistic and idealized models, focusing on the South Pacific Ocean. The deep eastern boundary current there is shown to be driven by a traditional interior balance together with a narrow boundary layer scale near the eastern boundary, which exists only when stratification and topography are both included. A simplified semianalytical vorticity model is developed for the deep eastern boundary current.

The curled wake model: equivalence of shed vorticity models

In this work, we explore the spanwise velocities in the wake of a yawed wind turbine. In the curled wake model, these motions are induced by a collection of vortices shed from the rotor plane. The direction of the vorticity generated by yaw is aligned with the main flow (streamwise) direction. The streamwise vorticity induces velocities in the spanwise directions. These are the motions responsible for creating the curled wake mechanism. In this work, we explore a more accurate formulation for this mechanism, using a vortex cylinder. Under certain assumptions, the new and original curled wake models yield the same mathematical formulation. Also, both models predict an elliptic distribution of vortex strength, where the main difference is the location of the vortices.

Exact conservative solutions of fluid models for the scrape-off layer as the ancestors of plasma blobs?

New exact, analytical solutions are presented for the conservative part of a standard two-fluid (density plus vorticity) model of the scrape-off layer (SOL) which are of the travelling-wave type and describe the transport of large, machine-scale structures across a plasma cross-section (radially and/or poloidally). It is conjectured that amongst these conservative solutions (some extended throughout space, others much more localised) might be the ancestors of propagating coherent structures, known as blobs, often seen in experiments and numerical simulations of SOL turbulence. Several types of solutions can be obtained, capable of mimicking not only high-density blobs propagating outwards, but also inwardly moving plasma holes (structures with densities lower than the backrgound’s). Besides their fundamental interest as conservative solutions of the equations describing SOL turbulence, these exact solutions have the added value of providing benchmarks for the verification of numerical algorithms, as is here illustrated. Having thus verified one’s numerical implementation, a more realistic SOL model (including diffusion, parallel losses and a source of core plasma) is solved (by gradually adding the extra terms to the conservative part) to check whether these conservative solutions survive the full dynamics or not. They actually do survive (albeit enduring some degree of distortion, ending up by being eventually lost) for parameters representative of SOL plasmas in present-day fusion devices, thus somewhat vindicating one’s original conjecture that they might be the ancestors of blobs. In addition, being actual solutions of the conservative part of the fluid SOL equations (and with the possibility of taking essentially Gaussian forms), there is no need to further justify their use as seeds with which to initialise (so-called seeded) simulations. A further characteristic that these Gaussian, blob-like conservative solutions possess is that they have intrinsic net vorticity (or spin), which is also believed to be the case for turbulence-created blobs.

Solving hyperbolic-elliptic problems on singular mapped disk-like domains with the method of characteristics and spline finite elements

A common strategy in the numerical solution of partial differential equations is to define a uniform discretization of a tensor-product multi-dimensional logical domain, which is mapped to a physical domain through a given coordinate transformation. By extending this concept to a multi-patch setting, simple and efficient numerical algorithms can be employed on relatively complex geometries. The main drawback of such an approach is the inherent difficulty in dealing with singularities of the coordinate transformation.This work suggests a comprehensive numerical strategy for the common situation of disk-like domains with a singularity at a unique pole, where one edge of the rectangular logical domain collapses to one point of the physical domain (for example, a circle). We present robust numerical methods for the solution of Vlasov-like hyperbolic equations coupled to Poisson-like elliptic equations in such geometries. We describe a semi-Lagrangian advection solver that employs a novel set of coordinates, named pseudo-Cartesian coordinates, to integrate the characteristic equations in the whole domain, including the pole, and a finite element elliptic solver based on globally C1 smooth splines (Toshniwal et al., 2017 [27]). The two solvers are tested both independently and on a coupled model, namely the 2D guiding-center model for magnetized plasmas, equivalent to a vorticity model for incompressible inviscid Euler fluids. The numerical methods presented show high-order convergence in the space discretization parameters, uniformly across the computational domain, without effects of order reduction due to the singularity. Dedicated tests show that the numerical techniques described can be applied straightforwardly also in the presence of point charges (equivalently, point-like vortices), within the context of particle-in-cell methods.

Can Machines Learn to Predict Weather? Using Deep Learning to Predict Gridded 500‐hPa Geopotential Height From Historical Weather Data

AbstractWe develop elementary weather prediction models using deep convolutional neural networks (CNNs) trained on past weather data to forecast one or two fundamental meteorological fields on a Northern Hemisphere grid with no explicit knowledge about physical processes. At forecast lead times up to 3 days, CNNs trained to predict only 500‐hPa geopotential height easily outperform persistence, climatology, and the dynamics‐based barotropic vorticity model, but do not beat an operational full‐physics weather prediction model. These CNNs are capable of forecasting significant changes in the intensity of weather systems, which is notable because this is beyond the capability of the fundamental dynamical equation that relies solely on 500‐hPa data, the barotropic vorticity equation. Modest improvements to the CNN forecasts can be made by adding 700‐ to 300‐hPa thickness to the input data. Our best performing CNN does a good job of capturing the climatology and annual variability of 500‐hPa heights and is capable of forecasting realistic atmospheric states at lead times of 14 days. Although our simple models do not perform better than an operational weather model, machine learning warrants further exploration as a weather forecasting tool; in particular, the potential efficiency of CNNs might make them attractive for ensemble forecasting.