The simplest decomposition of a turbulent field

2012 ◽  
Vol 241 (3) ◽  
pp. 284-287 ◽  
Author(s):  
Massimo Germano
Keyword(s):  
Turbulent Field

The Numerical Simulation of Turbulent Flow in Semi-Closed Rotor-Stator Cavity

2016 ◽  
Author(s):  
Guohu Luo ◽  
Shengde Wang ◽  
Hong Shen ◽  
Zhenqiang Yao
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Pressure Difference ◽  
Tangential Velocity ◽  
Reynolds Stress Model ◽  
Mean Flow ◽  
Closed Cavity ◽  
Turbulent Field ◽  
Effects Of Rotation

The present work numerically considered the turbulent flow in a semi-closed rotor-stator cavity with a superimposed throughflow based on Reynolds Stress Model (RSM). The mean flow structure and turbulent field in the semi-closed cavity (SC) were identified by comparison with the flow in open cavity (OC) and closed cavity (CC). Then the effects of rotation Reynolds number, ranging from 1 × 106 to 4 × 106, on the flow in SC were investigated. The superimposed flow noticeably decreases the tangential velocity, resulting that the pressure difference between central hub and periphery in SC is greater than the OC but less than the CC. The flow in SC belongs to Stewartson type in the region between inlet and outlet, but to Bachelor type between outlet and periphery. Around the outlets, the flow is greatly affected, especially for turbulent field, where the turbulence intensities maintain at higher levels outside the two boundary layers. With the increase of Reynolds number, the tangential velocity goes up, resulted the attenuation of jet impinging effects, the shrinking of affected zones by outlets and the enlargement of pressure difference. Moreover, with the Bödewadt layer moving toward the central hub, the turbulence intensities increase inside two boundary layers but decrease outside them. Consequently, the flow is transited to Stewartson and then Batchelor type.

STOCHASTIC MODELING AND FILTERING OF DISCRETE MEASUREMENTS FOR A TURBULENT FIELD APPLICATION TO MEASUREMENTS OF ATMOSPHERIC WIND

2010 ◽  
Vol 24 (29) ◽  
pp. 5723-5732
Author(s):  
C. BAEHR
Keyword(s):  
Stochastic Models ◽  
Nonlinear Filtering ◽  
Mean Field ◽  
Field Application ◽  
Velocity Measurements ◽  
Random Path ◽  
Acquisition Process ◽  
Turbulent Fluid ◽  
Turbulent Field ◽  
3D Flows

Nonlinear filtering of local turbulent fluid measurements was an unexplored domain; in this paper, we present original stochastic models and efficient filters to explore it. First, we propose nonlinear filters for processes of a mean-field law and give the convergence of their particle approximations. We then define the acquisition process of a vector field along a random path, and significantly modify the Lagrangian models of fluids proposed by the physicists to make them compatible with the problem of filtering. The closure of these equations is obtained by conditioning the dynamics to the observations and to the acquisition process. Our algorithm allowed us to filter velocity measurements of a real turbulent fluid in 3D flows.

scholarly journals 12. Solar electrodynamics

1958 ◽  
Vol 6 ◽  
pp. 105-113 ◽  
Author(s):  
T. G. Cowling
Keyword(s):  
Magnetic Fields ◽  
Solar Magnetic Field ◽  
Charged Particles ◽  
Coronal Heating ◽  
Magnetic Control ◽  
Solar Magnetic Fields ◽  
Historical Account ◽  
Turbulent Field ◽  
Sunspot Equilibrium ◽  
General Field

A historical account of the subject's development is attempted. Prior to 1940, the most significant papers were those by Larmor (1919) and Cowling (1934) on dynamo theories of solar fields: by Kiepenheuer (1935) on the corona; and by Ferraro (1937) on isorotation. These indicated the importance of electromagnetic forces and were groping towards the idea of frozen-in fields. The latter idea was, however, not clearly stated before Alfvén's 1941–2 papers.Theory since then is divided into sections concerned with mechanical effects of magnetic fields, theories of sunspots, and the nature and origin of solar magnetic fields. The first includes theories of magnetic control of support of coronal filaments and prominences (van de Hulst, Alfvén, Dungey) and theories of magnetic influence on sunspot equilibrium. The second includes Alfvén's and Walén's theories of the solar cycle, and Biermann's explanation of sunspot coolness in terms of magnetic inhibition of convection. Sunspot theories, being discussed more fully by Biermann, are considered only briefly.Electromagnetic heating covers theories of coronal heating and flares, discharge phenomena, particle acceleration and radio emission. Many of the older theories (Alfvén's on coronal heating, Giovanelli's on flares, that of Bagge and Biermann on cosmic rays) are set aside because of their neglect of self-induction effects and inadequacy of the mechanism of conversion. The relative motion of charged particles and neutral atoms (Piddington, Cowling) is described as supplying a powerful heating effect.As regards the magnitude of the general solar magnetic field, it is suggested that the observed value can be discarded only if decisive reasons are given. Other theories having so far proved inadequate, dynamo theories of the origin of solar fields are regarded as the most promising. These can be partial, as when a toroidal field capable of explaining spot fields is supposed to be generated from the general field (Walén and others), or when a turbulent field is supposed to be generated from a smaller regular field (Alfvén and others): or total, when a simultaneous explanation of all fields is attempted (e.g. Parker). A general appraisal is made of the different theories.

scholarly journals Experimental Investigation of the Flow Field in the Vicinity of an Oscillating Wave Surge Converter

2020 ◽  
Vol 8 (12) ◽  
pp. 976
Author(s):  
Moisés Brito ◽  
Rui M. L. Ferreira ◽  
Luis Teixeira ◽  
Maria G. Neves ◽  
Luís Gil
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Flow Field ◽  
Nonlinear Behavior ◽  
Front Face ◽  
Regular Wave ◽  
Turbulent Field ◽  
Analytical Results ◽  
Power Capture

The main objective of this paper is to characterize the flow field on the front face of an oscillating wave surge converter (OWSC) under a regular wave. For this purpose, the longitudinal and vertical velocity components were measured using an Ultrasonic Velocity Profiler (UVP). In order to explain the main trends of the OWSC’s dynamics, the experimental data were firstly compared with the analytical results of potential theory. A large discrepancy was observed between experimental and analytical results, caused by the nonlinear behavior of wave-OWSC interaction that determine the turbulent field and the boundary layer. The experimental velocity field shows a strong ascendant flow generated by the mass transfer over the flap (overtopping) and flow rotation generated by the beginning of the flap deceleration and acceleration. These features (overtopping and flow rotation) have an important role on the power capture of OWSC and, therefore, analytical results are not accurate to describe the complex hydrodynamics of OWSC.

The influence of entropy fluctuations on the interaction of turbulence with a shock wave

1997 ◽  
Vol 334 ◽  
pp. 353-379 ◽  
Author(s):  
KRISHNAN MAHESH ◽  
SANJIVA K. LELE ◽  
PARVIZ MOIN
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Kinetic Energy ◽  
Direct Numerical Simulation ◽  
Scaling Law ◽  
Linear Analysis ◽  
Turbulent Field ◽  
Bulk Compression ◽  
Baroclinic Torque

Direct numerical simulation and inviscid linear analysis are used to study the interaction of a normal shock wave with an isotropic turbulent field of vorticity and entropy fluctuations. The role of the upstream entropy fluctuations is emphasized. The upstream correlation between the vorticity and entropy fluctuations is shown to strongly influence the evolution of the turbulence across the shock. Negative upstream correlation between u′ and T′ is seen to enhance the amplification of the turbulence kinetic energy, vorticity and thermodynamic fluctuations across the shock wave. Positive upstream correlation has a suppressing effect. An explanation based on the relative effects of bulk compression and baroclinic torque is proposed, and a scaling law is derived for the evolution of vorticity fluctuations across the shock. The validity of Morkovin's hypothesis across a shock wave is examined. Linear analysis is used to suggest that shock-front oscillation would invalidate the relation between urms and Trms, as expressed by the hypothesis.

Computation of beam propagation in turbulent field

2016 ◽  
Author(s):  
Yao Yang ◽  
Zhaofeng Cen ◽  
Xiaotong Li
Keyword(s):  
Beam Propagation ◽  
Turbulent Field
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