Explanation of Turbulence Mixing Mechanism at Downstream Region of T-junction Piping Systems (II) : Understanding of Arched Vortex Structures by Numerical Simulations

2002 ◽  
Vol 2002.15 (0) ◽  
pp. 559-560
Author(s):  
Satoshi MURAKAMI ◽  
Toshiharu MURAMATSU
Keyword(s):  
Numerical Simulations ◽  
Vortex Structures ◽  
Downstream Region ◽  
Piping Systems ◽  
Turbulence Mixing

Numerical Investigations of a Turbulence Mixing Process Related to Thermal Striping Phenomena at a T-Junction of Liquid Metal Fast Reactor Piping Systems

2002 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Liquid Metal ◽  
Fast Reactor ◽  
Evaluation System ◽  
Velocity Ratio ◽  
Piping System ◽  
Mixing Process ◽  
Downstream Region ◽  
Piping Systems ◽  
Turbulence Mixing ◽  
Thermal Striping

Fluid-structure thermal interaction phenomena characterized by stationary random temperature fluctuations, namely thermal striping are observed in the downstream region of a T-junction piping system of liquid metal fast reactor (LMFR). Therefore the piping walls located in the downstream region must be protected against the stationary random thermal process which might induced high-cycle fatigue. This paper describes the evaluation system based on numerical simulation methods for the thermal striping, and numerical results of the thermal striping at a T-junction piping system under the various parameters, i.e., velocity ratio and diameter ratio between both the pipes and Reynolds number. Then detailed turbulence mixing process at the T-junction piping region due to arched vortexes generating lower frequency fluctuations are evaluated through a separate numerical analysis of a fundamental water experiment.

Numerical Investigations of Arched Vortex Characteristics Generated at T-Junction Piping Systems

2004 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Stokes Equations ◽  
Velocity Ratio ◽  
Navier Stokes ◽  
Fluid Temperature ◽  
Simulation Code ◽  
Navier Stokes Equations ◽  
Downstream Region ◽  
Piping Systems ◽  
Frequency Components ◽  
Thermal Striping

Thermohydraulic analyses for a fundamental water experiment simulating thermal striping phenomena at T-junction piping systems were carried out using a quasi-direct numerical simulation code DINUS-3, which is represented by instantaneous Navier-Stokes equations and deals with a modified third-order upwind scheme for convection terms. Calculated results were compared with experimental results on the flow patterns in the downstream region of the systems, the arched vortex structures under a deflecting jet condition, the generation frequency of the arched vortex, etc. in the various conditions; i.e., diameter ratio α, flow velocity ratio β and Reynolds number Re. From the comparisons, it was confirmed that (1) the DINUS-3 code is applicable to the flow pattern classifications in the downstream region of the T-junction piping systems, (2) the arched vortex characteristics with lower frequency components and their generation possibilities can be estimated numerically by the DINUS-3 code, and (3) special attentions should be paid to the arched vortex generations with lower frequency components of fluid temperature fluctuations in the design of T-junction systems from the viewpoints of the avoidances for the thermal striping.

Numerical Simualtion of Turbulence Mixing Characteristic in Various Secondary Flow Conditions at T-Junction Piping Systems

2004 ◽  
Author(s):  
Masa-aki Tanaka ◽  
Toshiharu Muramatsu
Keyword(s):  
Numerical Simulation ◽  
Secondary Flow ◽  
Temperature Fluctuation ◽  
Safety Issue ◽  
Flow Direction ◽  
Branch Pipe ◽  
Flow Conditions ◽  
Simulation Code ◽  
Piping Systems ◽  
Turbulence Mixing

Temperature fluctuation caused by mixing the fluids with different temperature in a T-junction pipe gives eventually thermal fatigue to structure, and this phenomenon is significant as safety issue in liquid metal cooled fast reactor (LMFBR). In Japan Nuclear Cycle Development Institute (JNC), experimental and numerical investigations have been performed to clarify the mixing phenomena in the T-junction pipe and to establish an evaluation rule for design. If the T-junction pipe is set near an elbow pipe, turbulence mixing is surly affected by the secondary flow generated in the elbow pipe and it is necessary to study the influence of the secondary flow on the temperature fluctuation in the T-junction pipe. We carried out investigation into the secondary flow effect by numerical simulation using a quasi-direct numerical simulation code. Numerical simulation is conducted on the existing experiment, in which the test section simulated the T-junction pipe with the elbow pipe in LMFBR. Major parameter in the numerical simulation is the flow direction of the branch pipe to the flow direction of the elbow pipe. We discuss the influences of the secondary flow on turbulent mixing behavior, and also clarify the mixing mechanism in T-junction pipe.

K-1340 Study on Turbulence Mixing Characteristics at T-Junction Piping Systems : Numerical Evaluations of Arched Vortexes

2001 ◽  
Vol II.01.1 (0) ◽  
pp. 193-194
Author(s):  
Satoshi MURAKAMI ◽  
Toshiharu MURAMATSU ◽  
Kozo SUDO ◽  
Hideki HIBARA
Keyword(s):  
Mixing Characteristics ◽  
Piping Systems ◽  
Turbulence Mixing

Vortex states in rotating two-component dipolar Bose–Einstein condensates

2019 ◽  
Vol 33 (10) ◽  
pp. 1950080 ◽  
Author(s):  
Qiang Zhao
Keyword(s):  
Numerical Simulations ◽  
Stationary State ◽  
Significant Role ◽  
Formation Process ◽  
Vortex Structures ◽  
Pitaevskii Equation ◽  
Vortex States ◽  
Dipole Interactions ◽  
Two Component ◽  
Bose Einstein

We consider the stationary state properties of pseudo-spin-1/2 rotating dipolar Bose–Einstein condensates (BECs) by numerical simulations of the Gross–Pitaevskii equation. Different vortex structures in each component are studied, depending on the competition between the dipole–dipole interactions (DDIs) and rotational. We also investigate the differences of vortex number in the two components, showing that anisotropic nature of DDIs plays a significant role in vortices formation process.

Near-Ground Pressure and Wind Measurements in Tornadoes*

2010 ◽  
Vol 138 (7) ◽  
pp. 2570-2588 ◽  
Author(s):  
Christopher D. Karstens ◽  
Timothy M. Samaras ◽  
Bruce D. Lee ◽  
William A. Gallus ◽  
Catherine A. Finley
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Vortex Structures ◽  
Swirl Ratio ◽  
Velocity Data ◽  
Low Level ◽  
Ground Pressure ◽  
Wind Measurements ◽  
Gust Front

Abstract Since the spring of 2002, tornadoes were sampled on nine occasions using Hardened In-Situ Tornado Pressure Recorder probes, video probes, and mobile mesonet instrumentation. This study describes pressure and, in some cases, velocity data obtained from these intercepts. In seven of these events, the intercepted tornadoes were within the radar-indicated or visually identified location of the supercell low-level mesocyclone. In the remaining two cases, the intercepted tornadoes occurred outside of this region and were located along either the rear-flank downdraft gust front or an internal rear-flank downdraft surge boundary. The pressure traces, sometimes augmented with videography, suggest that vortex structures ranged from single-cell to two-cell, quite similar to the swirl-ratio-dependent continuum of vortex structures shown in laboratory and numerical simulations. Although near-ground tornado observations are quite rare, the number of contemporary tornado measurements now available permits a comparative range of observed pressure deficits for a wide variety of tornado sizes and intensities to be presented.

Numerical Study of Orifice Cavitation-Induced Instability and Pipe Vibration

2018 ◽  
Author(s):  
Wenjie Bai ◽  
Quan Duan ◽  
Arris S. Tijsseling
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Eddy Simulation ◽  
Operation Conditions ◽  
Large Eddy ◽  
Strong Shear ◽  
Piping Systems ◽  
Variation Trends ◽  
Pipe Vibration

Different kinds of orifice are widely used as a resistance element to reduce pressure in various piping systems. However, due to strong shear and turbulence mechanisms around the orifice, it is susceptible to instabilities that generate pressure fluctuations and pipe vibrations. Especially when cavitation occurs, this effect can be very strong. The present work tries to characterize orifice-induced instability by means of numerical simulations and assess pipe vibration levels. Firstly, by taking an elongated orifice as an example, the fluctuating pressure around the orifice is obtained by a Large Eddy Simulation with a 2D unsteady model of cavitation. Secondly, the pipe vibration response is studied with experiment. The variation trends of pressure fluctuation and pipe vibration are analysed under different operation conditions. The results of the simulations can provide a good explanation for pipe vibration. A relationship between orifice cavitation-induced instability and vibration is established based on numerical simulations and experimental results.

scholarly journals Numerical simulations of swirling pipe flows- decay of swirl and occurrence of vortex structures

2011 ◽  
Vol 318 (6) ◽  
pp. 062022 ◽  
Author(s):  
H A Vaidya ◽  
Ö Ertunç ◽  
B Genç ◽  
F Beyer ◽  
Ç Köksoy ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Vortex Structures ◽  
Pipe Flows

Numerical Simulations on the Leading Edge Film Cooling With Counter-Inclined Film-Hole Row

2016 ◽  
Author(s):  
Dan Zhao ◽  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Ying-ni Zhai
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Numerical Simulations ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Downstream Region ◽  
The Heat Transfer Coefficient

Numerical simulations have been performed on the film cooling characteristics of counter-inclined film-hole rows, which have advantage in manufacturing relative to the usually used parallel-inclined film-hole row structure, on a turbine vane leading edge model. Two types of counter-inclined film-hole row were studied, including collinear counter-inclined film-hole row and non-collinear counter-inclined film-hole row. The distributions of film cooling effectiveness and heat transfer coefficient were obtained for the blowing ratios of 0.5, 1.0, 1.5 and 2.0. The effect of hole pitch on the film cooling effectiveness and heat transfer coefficient was also studied. The results show that the film cooling performances of counter-inclined film-hole rows are not weakened compared to the traditional parallel-inclined film-hole row structure. Film cooling effectiveness of the non-collinear counter-inclined film-hole row is even a little better than the film cooling effectiveness of the traditional film-hole row and collinear counter-inclined film-hole row in the downstream region near the film-hole row. The film cooling effectiveness of the two counter-inclined film-hole row structures decreases with the increase of blowing ratio, while the heat transfer coefficient increases. The change of inclination structure of film-hole row has very little effect on the heat transfer coefficient in the downstream region, while the increase of hole pitch could influence the values of heat transfer coefficient as well as film cooling effectiveness in a relatively notable way.

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