The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Akio Arakawa - One of the best experts on this subject based on the ideXlab platform.
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Inclusion of Surface Topography into the Vector Vorticity Equation Model (VVM)
Journal of Advances in Modeling Earth Systems, 2011Co-Authors: Akio ArakawaAbstract:[1] Surface topography is implemented into the vector Vorticity Equation model with a block representation of mountains in the height coordinate. The kinematic boundary conditions at the surface are satisfied with a proper computational boundary condition for Vorticity. This approach has been tested in various ways, including idealized 2D mountain waves, the much-studied “Boulder Downslope Windstorm” case, and 3D orographic precipitation over a ridge with and without small-scale irregularities. The model performs reasonably well in all of these cases, with no obvious computational difficulties due to the use of coordinate surfaces intersecting the surface and is ready to be used for arbitrarily prescribed surface topography without any artificial smoothing.
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A Three-Dimensional Anelastic Model Based on the Vorticity Equation
Monthly Weather Review, 2008Co-Authors: Joon-hee Jung, Akio ArakawaAbstract:Abstract A three-dimensional anelastic model has been developed using the Vorticity Equation, in which the pressure gradient force is eliminated. The prognostic variables of the model dynamics are the horizontal components of Vorticity at all heights and the vertical component of Vorticity and the horizontally uniform part of the horizontal velocity at a selected height. To implement the anelastic approximation, vertical velocity is diagnostically determined from the predicted horizontal components of Vorticity by solving an elliptic Equation. This procedure replaces solving the elliptic Equation for pressure in anelastic models based on the momentum Equation. Discretization of the advection terms uses an upstream-weighted partially third-order scheme. When time is continuous, the solution of this scheme is quadratically bounded. As an application of the model, interactions between convection and its environment with vertical shear are studied without and with model physics from the viewpoint of Vorticity...
Muhua Chien - One of the best experts on this subject based on the ideXlab platform.
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implementation of the land surface processes into a vector Vorticity Equation model vvm to study its impact on afternoon thunderstorms over complex topography in taiwan
Asia-pacific Journal of Atmospheric Sciences, 2019Co-Authors: Muhua Chien, Hsiaochun Lin, Fangyi ChengAbstract:In this study, we aim to evaluate the impact of fast land-atmosphere interactions on the afternoon thunderstorm in Taiwan through high-resolution meteorological simulations. For this purpose, the Noah land surface model (LSM) is implemented into the vector Vorticity Equation cloud-resolving model (VVM) with corresponding realistic land surface data of Taiwan into the coupling system, called TaiwanVVM. Two idealized experiments are conducted by giving the same surface forcing but one with direct land-atmosphere coupling from Noah LSM (called Coupled experiment) and the other with prescribed surface fluxes (called Prescribed experiment). Our results show that the fast land-atmosphere interaction over complex topography has a significant influence on rainfall intensity, especially in the heavy precipitating region where the interaction is strong. Without direct coupling between the land surface and the atmosphere in the Prescribed experiment, the diurnal intensity is suppressed by 50% over whole Taiwan and 70% for East Taiwan. Our findings demonstrate that the intensity of the afternoon thunderstorm is sensitive to fast land-atmosphere interactions by modifying local circulation in the mountainous region of Taiwan.
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representation of topography by partial steps using the immersed boundary method in a vector Vorticity Equation model vvm
Journal of Advances in Modeling Earth Systems, 2016Co-Authors: Muhua ChienAbstract:In this study, representation of surface topography in the vector Vorticity Equation model (VVM) is updated with a partial step approach using the immersed boundary method. Compared with the full step approach, the partial step approach provides additional topography forcing to represent micro mountains while preserving the same grid structure through interpolating from adjacent grid points. It maintains the characteristics of dynamics and physics of VVM and improves the representation of gentle slope topography without increasing vertical resolution. This approach produces reasonable results on the simulation of classical mountain waves with coarse vertical resolution. Additional experiments are performed to verify our approach including density driven flow using a cold bubble and 3-D orographic precipitation over a ridge. The results show that Vorticity fields in the partial step approach have a smoother response to the gentle slopes due to the improvement in the topography representation.
Spyros A. Kinnas - One of the best experts on this subject based on the ideXlab platform.
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Parallel implementation of a VIScous Vorticity Equation (VISVE) method in 3-D laminar flow
Journal of Computational Physics, 2021Co-Authors: Spyros A. KinnasAbstract:Abstract This paper presents a newly developed parallel implementation of solving the 3–D Vorticity Equation to fully simulate the incompressible laminar flow in the Eulerian frame. This method is designed to solve 3–D problems with irregular wall boundaries in small and compact computational domains in general shapes efficiently. The curl form of Vorticity Equation is discretized using the Finite Volume Method (FVM) by applying Stokes' theorem, which automatically guarantees the divergence–free condition of Vorticity field at all times. The Vorticity preserving velocity field is recovered by an explicit scheme without solving any linear system, and this velocity field is reprojected onto a divergence–free space by solving only one scalar velocity–potential Poisson's Equation. The Vorticity boundary condition is satisfied by employing a Vorticity creation scheme, that can handle arbitrary wall boundary shapes. Numerical results of the flow past a 3–D NACA0012 hydrofoil with one periodic direction, the flow past a sphere, and the flow past a 3–D rectangular wing are presented to validate the scheme.
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VIScous Vorticity Equation (VISVE) for Turbulent 2-D Flows with Variable Density and Viscosity
Journal of Marine Science and Engineering, 2020Co-Authors: Spyros A. KinnasAbstract:The general Vorticity Equation for turbulent compressible 2-D flows with variable viscosity is derived, based on the Reynolds-Averaged Navier-Stokes (RANS) Equations, and simplified versions of it are presented in the case of turbulent or cavitating flows around 2-D hydrofoils.
Robert Davies-jones - One of the best experts on this subject based on the ideXlab platform.
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Integrals of the Vorticity Equation. Part I: General three- and two-dimensional flows
Journal of the Atmospheric Sciences, 2006Co-Authors: Robert Davies-jonesAbstract:Abstract The integral of the vector Vorticity Equation for the Vorticity of a moving parcel in 3D baroclinic flow with friction is cast in a new form. This integral of the Vorticity Equation applies to synoptic-scale or mesoscale flows and to deep compressible or shallow Boussinesq motions of perfectly clear or universally saturated air. The present integral is equivalent to that of Epifanio and Durran in the Boussinesq limit, but its simpler form reduces easily to Dutton’s integral when the flow is assumed to be isentropic and frictionless. The integral for Vorticity has the following physical interpretation. The Vorticity of a parcel is composed of barotropic Vorticity; baroclinic Vorticity, which originates from solenoidal generation; and Vorticity stemming from frictional generation. Its barotropic Vorticity is the result of freezing into the fluid the w field (specific volume times Vorticity) that is present at the initial time. Its baroclinic Vorticity is the vector sum of contributions from small s...
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Integrals of the Vorticity Equation. Part II: Special Two-Dimensional Flows
Journal of the Atmospheric Sciences, 2006Co-Authors: Robert Davies-jonesAbstract:Abstract In Part I, a general integral of the 2D Vorticity Equation was obtained. This is a formal solution for the Vorticity of a moving tube of air in a 2D unsteady stratified shear flow with friction. This formula is specialized here to various types of 2D flow. For steady inviscid flow, the integral reduces to an integral found by Moncrieff and Green if the flow is Boussinesq and to one obtained by Lilly if the flow is isentropic. For steady isentropic frictionless motion of clear air, several quantities that are invariant along streamlines are found. These invariants provide another way to obtain Lilly’s integral from the general integral.
Zhimin Chen - One of the best experts on this subject based on the ideXlab platform.
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steady state bifurcation analysis of a strong nonlinear atmospheric Vorticity Equation
Journal of Mathematical Analysis and Applications, 2015Co-Authors: Zhimin ChenAbstract:The quasi-geostrophic Vorticity Equation studied in the present paper is a simplified form of the atmospheric circulation model introduced by Charney and DeVore [J. Atmos. Sci. 36(1979), 1205–1216] on the existence of multiple steady states to the understanding of the persistence of atmospheric blocking. The fluid motion defined by the Equation is driven by a zonal thermal forcing and an Ekman friction forcing measured by ?. It is proved that the steady-state solution is globally unique for large ? values while multiple steady-state solutions branch off the basic steady-state solution for ?viscosity, the Equation has fully non-linear property as its non-linear part contains the highest order derivative term. Steady-state bifurcation analysis is essentially based on the compactness, which can be simply obtained for semilinear Equations such as the Navier–Stokes Equations but is not available for the fully nonlinear quasi-geostrophic Vorticity Equation in the Euler formulation. Therefore the Lagrangian formulation of the Equation is employed to gain the required compactness.
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Steady-state bifurcation analysis of a strong nonlinear atmospheric Vorticity Equation
Journal of Mathematical Analysis and Applications, 2015Co-Authors: Zhimin ChenAbstract:The quasi-geostrophic Vorticity Equation studied in the present paper is a simplified form of the atmospheric circulation model introduced by Charney and DeVore [J. Atmos. Sci. 36(1979), 1205–1216] on the existence of multiple steady states to the understanding of the persistence of atmospheric blocking. The fluid motion defined by the Equation is driven by a zonal thermal forcing and an Ekman friction forcing measured by ?. It is proved that the steady-state solution is globally unique for large ? values while multiple steady-state solutions branch off the basic steady-state solution for ?
