Paper 22: Transient Flows in Short Curved Diffusers

1969 ◽  
Vol 184 (7) ◽  
pp. 45-56
Author(s):  
B. E. L. Deckker ◽  
T. K. Ramakrishnan ◽  
D. H. Male
Keyword(s):  
Pressure Wave ◽  
Transient Flow ◽  
Pressure Waves ◽  
Steady Regime ◽  
Circular Arc ◽  
Transient Flows ◽  
Area Distribution ◽  
Flow Through ◽  
Total Divergence ◽  
Curved Walls

The work reported is the first stage of an investigation into the effect of pressure waves of varying amplitude on the flow through the blade passages of turbomachines. Attention is confined to the interaction between the pressure wave and the geometry of four curved diffusers with the same area distribution about a circular- arc centre-line. The geometry of these diffusers is based on a straight diffuser with a total divergence angle equal to 12° and a length of 5 in. The nominal turning angles are 30°, 45°, 60°, and 90°. The transient flow through the five diffusers has been compared on the basis of sequences of Schlieren photographs taken at 50 μs intervals. The attenuation of the wave at the curved walls has also been measured. Systematic measurements have been made of the net and transmitted pressures, and also the pressures on the curved walls, during the quasi-steady régime. An attempt has been made to predict the net and transmitted pressures by means of two simple analyses, one of which is moderately successful. Diffuser effectiveness has been compared under conditions of steady and quasi-steady flow.

scholarly journals Analysis of Water Hammer with Different Closing Valve Laws on Transient Flow of Hydrogen-Natural Gas Mixture

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Norazlina Subani ◽  
Norsarahaida Amin
Keyword(s):  
Natural Gas ◽  
Pressure Wave ◽  
Transient Flow ◽  
Water Hammer ◽  
Wave Profile ◽  
Maximum Pressure ◽  
Gas Mixture ◽  
Pressure Waves ◽  
Closing Time ◽  
Closure Laws

Water hammer on transient flow of hydrogen-natural gas mixture in a horizontal pipeline is analysed to determine the relationship between pressure waves and different modes of closing and opening of valves. Four types of laws applicable to closing valve, namely, instantaneous, linear, concave, and convex laws, are considered. These closure laws describe the speed variation of the hydrogen-natural gas mixture as the valve is closing. The numerical solution is obtained using the reduced order modelling technique. The results show that changes in the pressure wave profile and amplitude depend on the type of closing laws, valve closure times, and the number of polygonal segments in the closing function. The pressure wave profile varies from square to triangular and trapezoidal shape depending on the type of closing laws, while the amplitude of pressure waves reduces as the closing time is reduced and the numbers of polygonal segments are increased. The instantaneous and convex closing laws give rise to minimum and maximum pressure, respectively.

scholarly journals Transient flows in a wellbore during killing of an empty well

2019 ◽  
Vol 23 (4) ◽  
pp. 2297-2306
Author(s):  
Lin Jiang ◽  
Na Wei ◽  
An-Qi Liu ◽  
Ying-Feng Meng ◽  
Hai-Tao Li ◽  
...  
Keyword(s):  
Gas Flow ◽  
Transient Flow ◽  
High Yield ◽  
Two Phase ◽  
Transient Flows ◽  
Gas Drilling ◽  
Well Completion ◽  
Flow Through ◽  
Transient Seepage ◽  
Gas Layer

Failure to adequately equipping the wellhead with appropriate well control equipment may result in a high pressure in the gas drilling when it reaches a high-yield gas layer. This would require the execution of a well killing operation to facilitate follow-up drilling and well completion. An empty well of gas-phase brings implementation of a gas-liquid two-phase transient flow, filling with killing mud. The operation may also entail coupling of the transient seepage from the formation with the gas-liquid two-phase transient flow through the wellbore. In this study, a mathematical model and a numerical method for coupling the transient gas flow through the formation with the gas-liquid two-phase transient flow in the wellbore were developed. The numerical simulation results showed that successful killing of an empty gas-drilled well required proper co-ordination of several key parameters among which the wellhead backpressure is particularly crucial to the operation. The findings of this study promise to facilitate the pro-cess design and parameter optimization for the killing of empty gas-drilled wells.

scholarly journals Investigations of hydraulic transient flows in pressurized pipeline based on 1D traditional and 3D weakly compressible models

2021 ◽  
Vol 23 (2) ◽  
pp. 231-248
Author(s):  
Guohong Wu ◽  
Xiangyu Duan ◽  
Jianghui Zhu ◽  
Xiaoqin Li ◽  
Xuelin Tang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Pressure Wave ◽  
Transient Flow ◽  
Turbulence Models ◽  
Turbulent Shear ◽  
Wall Region ◽  
Turbulent Dissipation ◽  
Transient Flows ◽  
Axial Pressure Gradient ◽  
Viscous Shear

Abstract Transient flow characteristics and dissipation mechanism in pressurized pipeline were investigated based on 1D friction models and 3D turbulence models, where the pressure–density model was combined into the 3D continuity equation allowing for the elasticity of the fluid and the pipes. The applicability of 3D realizable k–ε and 3D SST (shear stress transport) k–ω turbulence models was verified with comparison to 1D traditional water hammer models and the experimental data for fast closing of the valve in the reservoir–pipe–valve system. The valve closure rule was instantaneously carried out using the grid slip CFD (computational fluid dynamics) technique. The SST k–ω turbulence model has the highest accuracy in predicting the pressure attenuation of transient flows. The 3D detailed flow field confirms that the asymmetric flows induced by the change of valve opening within approximately three-fourths of the pipe inner diameter before the valve are captured. In the pressure wave cycles, the unsteady inertia, axial pressure gradient, viscous shear stress and turbulent shear stress mainly influence the velocity variations. During the pressure wave propagation, the viscous and turbulent dissipation are critical in the pressure attenuation in the wall region; the viscous dissipation is mainly concentrated in the viscous sublayer, while the turbulent dissipation increases to the maximum values at y+ = 13–23.

Optimal cross-sectional area distribution of a high-speed train nose to minimize the tunnel micro-pressure wave

2010 ◽  
Vol 42 (6) ◽  
pp. 965-976 ◽  
Author(s):  
Yo-Cheon Ku ◽  
Joo-Hyun Rho ◽  
Su-Hwan Yun ◽  
Min-Ho Kwak ◽  
Kyu-Hong Kim ◽  
...  
Keyword(s):  
Pressure Wave ◽  
High Speed ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
High Speed Train ◽  
Cross Sectional ◽  
Area Distribution

Transient Analysis on Helium Coolant Tube Break Accident of Dual-Functional Lithium Lead Test Blanket Module

2016 ◽  
Author(s):  
Qian Sun ◽  
Tianji Peng ◽  
Zhiwei Zhou ◽  
Zhibin Chen ◽  
Jieqiong Jiang
Keyword(s):  
Pressure Wave ◽  
Transient Analysis ◽  
Structural Integrity ◽  
Maximum Pressure ◽  
Pressure Waves ◽  
Operating Pressure ◽  
Pressure Shock ◽  
Dual Functional ◽  
Short Time ◽  
Helium Coolant

Dual-functional Lithium Lead Test Blanket Module (DFLL-TBM) was proposed by China for testing in the International Thermonuclear Experimental Reactor (ITER).When an in-TBM helium coolant tube breaks, high pressure helium will discharge into the Pb-Li breeding zones. The pressure shock in the TBM will threaten the structural integrity and safety of ITER. Simulation and analysis on helium coolant tube break accident of DFLL-TBM was performed, and two cases with different break sizes were considered. Computational results indicate that intense pressure waves spread quickly from the break to the surrounding structures and the variation of pressure in the TBM breeding box is drastic especially when the pressure wave propagation encounters large resistance such as at the bending corner of the flow channel, the inlet and outlet of Pb-Li, etc. The maximum pressure in the TBM breeding box which is even higher than the operating pressure of helium also occurs in these zones. Although the pressure shock lasts for a very short time, its effect on the structural integrity of DFLL-TBM needs to be paid attention to.

Laminar flow in symmetrical channels with slightly curved walls II. An asymptotic series for the stream function

1963 ◽  
Vol 272 (1350) ◽  
pp. 406-428 ◽  
Keyword(s):  
Laminar Flow ◽  
Asymptotic Series ◽  
Radius Of Curvature ◽  
Two Dimensional ◽  
The Third ◽  
Higher Order Terms ◽  
Curvature Parameter ◽  
Leading Term ◽  
Flow Through ◽  
Curved Walls

A class of two-dimensional channels, with walls whose radius of curvature is uniformly large relative to local channel width, is described, and the velocity field of laminar flow through these channels is obtained as a power series in the small curvature parameter. The leading term is the Jeffery-Hamel solution considered in part I, and it is shown here how the higher-order terms are found. Terms of the third approximation have been computed. The theory is applied to two examples, for one of which experimental results are available and confirm the theoretical values with fair accuracy.

Cinematographic Analysis of Counter Jet Formation in a Single Cavitation Bubble Collapse Flow

2011 ◽  
Vol 27 (2) ◽  
pp. 253-266 ◽  
Author(s):  
S.-H. Yang ◽  
S.-Y. Jaw ◽  
K.-C. Yeh
Keyword(s):  
Flow Field ◽  
Cavitation Bubble ◽  
Pressure Wave ◽  
Bubble Surface ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Liquid Jet ◽  
Pressure Waves ◽  
Field Variation ◽  
Critical Position

ABSTRACTThis study utilized a U-shape platform device to generate a single cavitation bubble for the detail analysis of the flow field characteristics and the cause of the counter jet during the process of bubble collapse induced by pressure wave. A series of bubble collapse flows induced by pressure waves of different strengths are investigated by positioning the cavitation bubble at different stand-off distances to the solid boundary. It is found that the Kelvin-Helmholtz vortices are formed when the liquid jet induced by the pressure wave penetrates the bubble surface. If the bubble center to the solid boundary is within one to three times the bubble's radius, a stagnation ring will form on the boundary when impacted by the penetrated jet. The liquid inside the stagnation ring is squeezed toward the center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from the solid boundary is about three times the bubble's radius, the bubble collapse flows will vary. Depending on the strengths of the pressure waves applied, either just the Kelvin-Helmholtz vortices form around the penetrated jet or the penetrated jet impacts the boundary directly to generate the stagnation ring and the counter jet flow. This phenomenon used the particle image velocimetry method can be clearly revealed the flow field variation of the counter jet. If the bubble surface is in contact with the solid boundary, the liquid jet can only splash radially without producing the stagnation ring and the counter jet. The complex phenomenon of cavitation bubble collapse flows are clearly manifested in this study.

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