Using the Vorticity Flux Equations to Model Hypersonic Transition

AbstractThe radius of maximum wind (RMW) has been found to contract rapidly well preceding rapid intensification in tropical cyclones (TCs) in recent literature but the understanding of the involved dynamics is incomplete. In this study, this phenomenon is revisited based on ensemble axisymmetric numerical simulations. Consistent with previous studies, because the absolute angular momentum (AAM) is not conserved following the RMW, the phenomenon can not be understood based on the AAM-based dynamics. Both budgets of tangential wind and the rate of change in the RMW are shown to provide dynamical insights into the simulated relationship between the rapid intensification and rapid RMW contraction. During the rapid RMW contraction stage, due to the weak TC intensity and large RMW, the moderate negative radial gradient of radial vorticity flux and small curvature of the radial distribution of tangential wind near the RMW favor rapid RMW contraction but weak diabatic heating far inside the RMW leads to weak low-level inflow and small radial absolute vorticity flux near the RMW and thus a relatively small intensification rate. As RMW contraction continues and TC intensity increases, diabatic heating inside the RMW and radial inflow near the RMW increase, leading to a substantial increase in radial absolute vorticity flux near the RMW and thus the rapid TC intensification. However, the RMW contraction rate decreases rapidly due to the rapid increase in the curvature of the radial distribution of tangential wind near the RMW as the TC intensifies rapidly and RMW decreases.

Download Full-text

New Physics II: Spin Picture, Particle Structure, and Fundamental Interactions

10.21203/rs.3.rs-1116117/v7 ◽

2021 ◽

Author(s):

China Kang

Keyword(s):

High Speed ◽

New Physics ◽

Particle Structure ◽

Classical Counterpart ◽

Fundamental Interactions ◽

Wave Particle Duality ◽

Theory Of Everything ◽

Vorticity Flux ◽

Quantum Phenomena ◽

Almost All

Abstract Experimental data sometimes fails to render the expected truth, such as high-speed bullets smashing into pieces on a water surface cannot verify the water’s hardness. By re-examining the essence underneath quantum phenomena and analyzing their relevance to universal classical theory, this study has thoroughly revealed the classical counterpart of spin. Subsequently, the equivalence between spin angular momentum (of energy or charge) and vorticity flux (of energy or charge) has also been unveiled, thus intuitively clarifying many abstruse physical concepts, like spin magnetic moment, virtual electron, relativistic time dilation, neutrino chirality, quark origin, and fundamental interactions (including gravitons). From now on, almost all quantum puzzles (e.g., wave-particle duality, quantum entanglement, Schrödinger’s cat) can be understood classically, just as prominent physicists such as Planck, Einstein, and Schrödinger longed for back then. This paper can be considered a blueprint of the Theory of Everything (TOE).

Download Full-text

On the lyman problem

Open Physics ◽

10.2478/bf02476296 ◽

2003 ◽

Vol 1 (2) ◽

Author(s):

Václav Kolár

Keyword(s):

Classical Field Theory ◽

Integral Boundary ◽

Effective Measure ◽

Local Determination ◽

Vorticity Flux ◽

Effective Part ◽

Definition Of ◽

Vorticity Transport ◽

Creation Rate

AbstractThis paper attempts to answer Lyman's question (1990) on the non-uniqueness in defining the 3D measure of the boundary vorticity-creation rate. Firstly, a straightforward analysis of the vorticity equation introduces a definition of a general vorticity flux-density tensor and its ‘effective’ part. The approach is strictly based on classical field theory and is independent of the constitutive structure of continuous medium. Secondly, the fundamental question posed by Lyman dealing with the ambiguity of the 3D measure of the boundary vorticity-creation rate for incompressible flow is discussed. It is shown that the original 3D measure (for an incompressible Newtonian fluid defined by Panton 1984), which is reminiscent of an analogy to Fourier's law, is in its character ‘effective’ and plays a crucial role in the prognostic vorticity transport equation. The alternative 3D measure proposed by Lyman includes, on the other hand, a ‘non-effective’ part, which plays a role in the local determination of the ‘effective’ measure as well as in a certain diagnostic integral boundary condition.

Download Full-text

Investigation of flow separation in a centrifugal pump impeller based on improved delayed detached eddy simulation method

Advances in Mechanical Engineering ◽

10.1177/1687814019897832 ◽

2019 ◽

Vol 11 (12) ◽

pp. 168781401989783

Author(s):

Yun Ren ◽

Zuchao Zhu ◽

Denghao Wu ◽

Xiaojun Li ◽

Lanfang Jiang

Keyword(s):

Large Eddy Simulation ◽

Centrifugal Pump ◽

Flow Separation ◽

Hybrid Algorithm ◽

Internal Flow ◽

Navier Stokes ◽

Eddy Simulation ◽

Large Eddy ◽

Reynolds Averaged Navier Stokes ◽

Vorticity Flux

The mechanism of flow separation in the impeller of a centrifugal pump with a low specific speed was explored by experimental, numerical, and theoretical methods. A novel delayed Reynolds-averaged Navier–Stokes/large eddy simulation hybrid algorithm combined with a rotation and curvature correction method was developed to calculate the inner flow field of the original pump for the large friction loss in the centrifugal impeller, high adverse pressure gradient, and large blade curvature. Boundary vorticity flux theory was introduced for internal flow diagnosis, and the relative velocity vector near the surface of the blade and the distribution of the dimensionless pressure coefficient was analyzed. The validity of the numerical method was verified, and the location of the backflow area and its flow features were determined. Finally, based on flow diagnosis, the geometric parameters influencing the flow state of the impeller were specifically adjusted to obtain a new design impeller. The results showed that the distribution of the boundary vorticity flux peak values, the skin friction streamline, and near-wall relative velocities improved significantly after the design change. In addition, the flow separation was delayed, the force applied on the blade was improved, the head under the part-load condition was improved, and the hydraulic efficiency was improved over the global flow ranges. It was demonstrated that the delayed Reynolds-averaged Navier–Stokes/large eddy simulation hybrid algorithm was capable to capture the separation flow in a centrifugal pump, and the boundary vorticity flux theory was suitable for the internal flow diagnosis of centrifugal pump.

Download Full-text

Interpreting Vortex Interactions With a Free Surface

Journal of Fluids Engineering ◽

10.1115/1.2910248 ◽

1994 ◽

Vol 116 (1) ◽

pp. 91-94 ◽

Cited By ~ 23

Author(s):

E. P. Rood

Keyword(s):

Free Surface ◽

Surface Condition ◽

Viscous Forces ◽

Vortex Interactions ◽

Free Surface Condition ◽

Vortex Loops ◽

Physical Experiments ◽

Vorticity Flux ◽

Tangential Acceleration

An understanding of the process by which vorticity interacts with a free surface is sought by analytical examination of the free-surface condition for the vorticity flux. A novel mechanism is suggested that permits closed vortex loops to evolve into open loops terminating at the free surface. It is hypothesized that abrupt vortex “disconnection,” observed in physical experiments, arises from a smooth diffusion of vorticity through the interface, with a necessary coincident tangential acceleration of the interface attributed to viscous forces.

Download Full-text

Tidal rectification in lateral viscous boundary layers of a semi-enclosed basin

Journal of Fluid Mechanics ◽

10.1017/s0022112087002933 ◽

1987 ◽

Vol 184 ◽

pp. 381-397 ◽

Cited By ~ 5

Author(s):

H. E. De Swart ◽

J. T. F. Zimmerman

Keyword(s):

Reynolds Number ◽

Boundary Layers ◽

Outer Boundary ◽

Stokes Number ◽

Residual Current ◽

Residual Flow ◽

Oscillatory Boundary Layer ◽

Tidal Rectification ◽

Vorticity Flux ◽

Viscous Boundary

The rectified flow, induced by divergence of the vorticity flux in lateral oscillatory viscous boundary layers along the sidewalls of a semi-enclosed basin, is studied as a function of the Strouhal number, k, equivalent to the Reynolds number of the viscous inner oscillatory boundary layer, and of the Stokes number. The squared ratio of these numbers defines another Reynolds number, measuring the strength of the self-advection by the residual flow. For strong self-advection the residual current decays to zero in an outer boundary, its width being large compared to the width of the inner layer. The regimes of small, moderate and strong self-advection are analysed.

Download Full-text

Wall-vorticity flux dynamics in a two-dimensional turbulent boundary layer

Journal of Fluid Mechanics ◽

10.1017/s0022112096001553 ◽

1996 ◽

Vol 309 ◽

pp. 45-84 ◽

Cited By ~ 31

Author(s):

J. Andreopoulos ◽

J. H. Agui

Keyword(s):

Boundary Layer ◽

Viscous Force ◽

Flux Dynamics ◽

Pressure Transducers ◽

High Frequency Response ◽

Wall Structures ◽

Response Pressure ◽

Vorticity Flux ◽

Low Amplitude ◽

Physical Phenomena

Four high-frequency-response pressure transducers with 10 viscous units resolution each have been used to obtain simultaneously the fluctuating pressure gradients at the wall of a zero-pressure-gradient boundary layer and then to compute the vorticity flux away from the wall. Since the viscous force on an element of incompressible fluid is determined by the local vorticity gradients, understanding of their dynamical characteristics is essential in identifying the turbulent structure. Extremely high and low amplitudes of both vorticity gradients have been observed which contribute significantly to their statistics although they have low probability of appearance. The r.m.s. of the vorticity flux when scaled with inner wall variables depends very strongly on the Reynolds number, indicating a breakdown of this type of scaling. The application of a small threshold to the data indicated two preferential directions of the vorticity flux vector. An attempt has been made to identify these high- and low-amplitude signals with physical phenomena associated with bursting-sweep processes. Vortical structures carrying bipolar vorticity are the dominant wall structures which are associated with the violent events characterized by large fluctuations of vorticity flux.

Download Full-text

On the generation of vorticity at a free surface

Journal of Fluid Mechanics ◽

10.1017/s0022112098003978 ◽

1999 ◽

Vol 382 ◽

pp. 351-366 ◽

Cited By ~ 42

Author(s):

THOMAS LUNDGREN ◽

PETROS KOUMOUTSAKOS

Keyword(s):

Shear Stress ◽

Free Surface ◽

Viscous Flows ◽

Vortex Sheet ◽

Boundary Integral ◽

Free Surfaces ◽

Boundary Integral Formulation ◽

Pressure Boundary Condition ◽

Vorticity Flux ◽

Pressure Boundary Conditions

The mechanism for the generation of vorticity at a viscous free surface is described. This is a free-surface analogue of Lighthill's strategy for determining the vorticity flux at solid boundaries. In this method the zero-shear-stress and pressure boundary conditions are transformed into a boundary integral formulation suitable for the velocity–vorticity description of the flow. A vortex sheet along the free surface is determined by the pressure boundary condition, while the condition of zero shear stress determines the vorticity at the surface. In general, vorticity is generated at free surfaces whenever there is flow past regions of surface curvature. It is shown that vorticity is conserved in free-surface viscous flows. Vorticity which flows out of the fluid across the free surface is gained by the vortex sheet; the integral of vorticity over the entire fluid region plus the integral of ‘surface vorticity’ over the free surface remains constant. The implications of the present strategy as an algorithm for numerical calculations are discussed.

Download Full-text