Characteristics of Fluidelastic Instability of Tube Rows in Crossflow

1988 ◽  
Vol 110 (1) ◽  
pp. 1-5
Author(s):  
S. S. Chen ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Diameter Ratio ◽  
Critical Flow ◽  
Jump Phenomenon ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Flow Velocities

An experimental study is reported that investigated the jump phenomenon in critical flow velocities for tube rows with different pitch-to-diameter ratios, and the excited and intrinsic instabilities for a tube row with a pitch-to-diameter ratio of 1.75. The experimental data provide additional insights into the instability phenomena of tube arrays in crossflow.

An Analysis of In-Flow Fluidelastic Instability Based on a Physical Insight

2014 ◽  
Author(s):  
Tomomichi Nakamura
Keyword(s):  
Flow Velocity ◽  
Flow Instability ◽  
Pressure Sensors ◽  
Measured Data ◽  
Critical Flow ◽  
Nonlinear Phenomenon ◽  
Critical Flow Velocity ◽  
Fluid Force ◽  
Tube Arrays ◽  
Fluidelastic Instability

Fluidelastic vibration of tube arrays caused by cross-flow has recently been highlighted by a practical event. There have been many studies on fluidelastic instability, but almost all works have been devoted to the tube-vibration in the transverse direction to the flow. For this reason, there are few data on the fluidelastic forces for the in-flow movement of the tubes, although the measured data on the stability boundary has gradually increased. The most popular method to estimate the fluidelastic force is to measure the force acting on tubes due to the flow, combined with the movement of the tubes. However, this method does not give the physical explanation of the root-cause of fluidelastic instability. In the work reported here, the in-flow instability is assumed to be a nonlinear phenomenon with a retarded or delayed action between adjacent tubes. The fluid force acting on tubes are estimated, based on the measured data in another paper for the fixed cylinders with distributed pressure sensors on the surface of the cylinders. The fluid force acting on the downstream-cylinder is assumed in this paper to have a delayed time basically based on the distance between the separation point of the upstream-cylinder to the re-attachment point, where the fluid flows with a certain flow velocity. Two models are considered: a two-cylinder and three–cylinder models, based on the same dimensions as our experimental data to check the critical flow velocity. Both models show the same order of the critical flow velocity and a similar trend for the effect of the pitch-to-diameter ratio of the tube arrays, which indicates this analysis has a potential to explain the in-flow instability if an adequate fluid force is used.

Investigation of In-Flow Fluidelastic Instability of Square Tube Arrays Subjected to Air Cross Flow

2015 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Shinichiro Hagiwara ◽  
Joji Yamada ◽  
Kenji Usuki
Keyword(s):  
Nuclear Power ◽  
Flow Instability ◽  
Flow Direction ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Nuclear Industry ◽  
Flexible Cylinder ◽  
Triangular Arrays ◽  
Tube Arrays ◽  
Fluidelastic Instability

In-flow instability of tube arrays is a recent major issue in heat exchanger design since the event at a nuclear power plant in California [1]. In our previous tests [2], the effect of the pitch-to-diameter ratio on fluidelastic instability in triangular arrays is reported. This is one of the present major issues in the nuclear industry. However, tube arrays in some heat exchangers are arranged as a square array configuration. Then, it is important to study the in-flow instability on the case of square arrays. The in-flow fluidelastic instability of square arrays is investigated in this report. It was easy to observe the in-flow instability of triangular arrays, but not for square arrays. The pitch-to-diameter ratio, P/D, is changed from 1.2 to 1.5. In-flow fluidelastic instability was not observed in the in-flow direction. Contrarily, the transverse instability is observed in all cases including the case of a single flexible cylinder. The test results are finally reported including the comparison with the triangular arrays.

Applicability of the Wavy-Wall Model of Fluidelastic Instability to a Normal Triangular Tube Array

2008 ◽  
Author(s):  
Julie Harel ◽  
Craig Meskell
Keyword(s):  
Experimental Data ◽  
Triangular Array ◽  
Phase Lag ◽  
Pressure Perturbation ◽  
Wavy Wall ◽  
Decay Function ◽  
Wall Model ◽  
Line Array ◽  
Tube Arrays ◽  
Fluidelastic Instability

The Yetisir and Weaver formulation of the Lever and Weaver “wavy-wall” model for fluidelastic instability in tube arrays has been implemented for both normal triangular and in-line square arrays. The sensitivity of this model to the input parameters (i.e. attachment and separation points, decay function and phase lag function) has been examined. It was found that variations in the decay function were most significant and that the model behaved similarly for both array types. The predicted surface pressure perturbation due to tube displacement has then been compared with experimental data. For the in-line array the model behaviour compared well, while for the normal triangular array, the predictions were not representative of the experimental data. It is concluded that while the Yetisir and Weaver model can be applied successfully to in-line square arrays, it is not appropriate for densely packed normal triangular arrays.

Instability Mechanisms and Stability Criteria of a Group of Circular Cylinders Subjected to Cross-Flow—Part 2: Numerical Results and Discussions

1983 ◽  
Vol 105 (2) ◽  
pp. 253-260 ◽  
Author(s):  
S. S. Chen
Keyword(s):  
Experimental Data ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Critical Flow ◽  
Stability Criteria ◽  
Flow Part ◽  
Parameter Ranges ◽  
Square Array ◽  
Good Agreement ◽  
Flow Velocities

The fluid-force coefficients for a row of cylinders and a square array are determined from available experimental data and critical flow velocities are calculated as a function of system parameters. Experimental data for critical flow velocities are found to be in good agreement with the analytical results. It is concluded that different stability criteria have to be utilized in different parameter ranges because of different instability mechanisms.

Measurement of Pressure Drop in a Full-Scale Fuel Assembly of a Liquid Metal Reactor

2003 ◽  
Vol 125 (2) ◽  
pp. 233-238 ◽  
Author(s):  
Seok Ki Choi ◽  
Il Kon Choi ◽  
Ho Yun Nam ◽  
Jong Hyeun Choi ◽  
Hoon Ki Choi
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Pressure Drop ◽  
Liquid Metal ◽  
Fuel Assembly ◽  
Diameter Ratio ◽  
Pressure Drops ◽  
Liquid Metal Reactor ◽  
The Wire ◽  
Measured Pressure

An experimental study has been carried out to measure the pressure drop in a 271-pin fuel assembly of a liquid metal reactor. The rod pitch to rod diameter ratio P/D of the fuel assembly is 1.2 and the wire lead length to rod diameter ratio H/D is 24.84. Measurements are made for five different sections in a fuel assembly; inlet orifice, fuel assembly inlet, wire-wrapped fuel assembly, fuel assembly outlet and fuel assembly upper region. A series of water experiments have been conducted changing flow rate and water temperature. It is shown that the pressure drops in the inlet orifice and in the wire-wrapped fuel assembly are much larger than those in other regions. The measured pressure drop data in a wire-wrapped fuel assembly region is compared with the existing four correlations. It is shown that the correlation proposed by Cheng and Todreas fits best with the present experimental data among the four correlations considered.

Pitch and Mass Ratio Effects on Transverse and Streamwise Fluidelastic Instability in Parallel Triangular Tube Arrays

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Marwan Hassan ◽  
David Weaver
Keyword(s):  
Experimental Data ◽  
Relative Importance ◽  
Mass Ratio ◽  
Damping Parameter ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
Fluid Coupling ◽  
Lift And Drag ◽  
Tube Pitch

The simple tube and channel theoretical model for fluidelastic instability (FEI) in tube arrays, as developed by Hassan and Weaver, has been used to study the effects of pitch ratio and mass ratio on the critical velocity of parallel triangular tube arrays. Simulations were carried out considering fluidelastic forces in the lift and drag directions independently and acting together for cases of a single flexible tube in a rigid array and a fully flexible kernel of seven tubes. No new empirical data were required using this model. The direction of FEI as well as the relative importance of fluid coupling of tubes was studied, including how these are affected by tube pitch ratio and mass ratio. The simulation predictions agree reasonably well with available experimental data. It was found that parallel triangular tube arrays are more vulnerable to streamwise FEI when the pitch ratio is small and the mass-damping parameter (MDP) is large.

EXPERIMENTAL STUDY OF THE KINEMATIC PARAMETERS OF MOVEMENT OF CARS FORCED IDLE MOTION

2018 ◽  
pp. 52-57
Author(s):  
Ivelin Kostov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Experimental Research ◽  
Kinematic Parameters ◽  
Research Results ◽  
Software Product

In the work brought some experimental data of kinematic parameters of movement of cars forced idle, as the software product was used to diagnose 900 ATS, which recorded kinematic parameters of vehicle. On the basis of the conducted experimental research results are shown tabulated and analysed.

EXPERIMENTAL STUDY ON FLAME PROPAGATION IN A STRAIGHT PIPE

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Siti Zubaidah Sulaiman ◽  
Rafiziana Md Kasmani ◽  
A. Mustafa
Keyword(s):  
Experimental Study ◽  
Flame Propagation ◽  
Experimental Work ◽  
Diameter Ratio ◽  
Straight Pipe ◽  
Pipe Length ◽  
Operating Condition ◽  
Consistent Trend ◽  
Length To Diameter Ratio

Flame propagation in a closed pipe with diameter 0.1 m and 5.1 m long, as well as length to diameter ratio (L/D) of 51, was studied experimentally. Hydrogen/air, acetylene/air and methane/air with stoichiometric concentration were used to observe the trend of flame propagation throughout the pipe. Experimental work was carried out at operating condition: pressure 1 atm and temperature 273 K. Results showed that all fuels are having a consistent trend of flame propagation in one-half of the total pipe length in which the acceleration is due to the piston-like effect. Beyond the point, fuel reactivity and tulip phenomenon were considered to lead the flame being quenched and decrease the overpressures drastically. The maximum overpressure for all fuels are approximately 1.5, 7, 8.5 barg for methane, hydrogen, and acetylene indicating that acetylene explosion is more severe. 

scholarly journals Impact of Orifice-to-Pipe Diameter Ratio on Leakage Flow: An Experimental Study

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2189
Author(s):  
Tingchao Yu ◽  
Xiangqiu Zhang ◽  
Iran E. Lima Neto ◽  
Tuqiao Zhang ◽  
Yu Shao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Pipe Wall ◽  
Pressure Head ◽  
Diameter Ratio ◽  
Pipe Diameter ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Different Shapes ◽  
Real Scale

The traditional orifice discharge formula used to estimate the flow rate through a leak opening at a pipe wall often produces inaccurate results. This paper reports an original experimental study in which the influence of orifice-to-pipe diameter ratio on leakage flow rate was investigated for several internal/external flow conditions and orifice holes with different shapes. The results revealed that orifice-to-pipe diameter ratio (or pipe wall curvature) indeed influenced the leakage flow, with the discharge coefficient ( C d ) presenting a wide variation (0.60–0.85). As the orifice-to-pipe diameter ratio decreased, the values of C d systematically decreased from about 12% to 3%. Overall, the values of C d also decreased with β (ratio of pressure head differential at the orifice to wall thickness), as observed in previous studies. On the other hand, orifice shape, main pipe flow velocity, and external medium (water or air) all had a secondary effect on C d . The results obtained in the present study not only demonstrated that orifice-to-pipe diameter ratio affects the outflow, but also that real scale pipes may exhibit a relevant deviation of C d from the classical range (0.61–0.67) reported in the literature.

Experimental study of hypochloremia

1935 ◽  
Vol 31 (8-9) ◽  
pp. 1112-1112
Keyword(s):  
Experimental Data ◽  
Experimental Study

Analyzing clinical and experimental data on hypochloremia, the authors show that both during vomiting and when giving diuretica, it is not only about the loss of chlorine, but at the same time a large amount of water is lost.

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