Calculation of Pressure Wave Propagation Through a Tube Junction

1996 ◽  
Vol 210 (3) ◽  
pp. 239-244 ◽  
Author(s):  
M J P William-Louis ◽  
C Tournier
Keyword(s):  
Wave Propagation ◽  
Pressure Wave ◽  
Method Of Characteristics ◽  
Subsonic Flow ◽  
New Method ◽  
Superposition Method ◽  
Pressure Waves ◽  
Incoming Flow ◽  
Governing Equations ◽  
Pressure Losses

This paper describes a new method for the calculation of pressure wave propagation through a junction. The unsteady model, valid for subsonic flow, takes into account the fluid compressibility and pressure losses according to the type of junction. A new method called the ‘branch superposition method’ is used for the numerical calculation, and consists of uncoupling the system of governing equations. During the propagation of pressure waves through a three-tube junction, two branches are inlet or outlet. Therefore, to uncouple the system, one of the two branches with incoming flow is modelled as a source or one of the two branches with outgoing flow as a sink. This method, combined with the method of characteristics, gives the possibility of predicting the propagation of pressure waves through a junction, where the fluid may be initially at rest or not. The model is validated by a comparison with experimental results.

An Investigation Into Quantifying Pressure Wave Oscillation in the Lung

2010 ◽  
Author(s):  
J. Mussa ◽  
A. M. Al-Jumaily ◽  
G. Ijpma
Keyword(s):  
Wave Propagation ◽  
Medical Devices ◽  
Pressure Wave ◽  
Pressure Oscillation ◽  
Variable Pressure ◽  
Pressure Waves ◽  
Pressure Oscillations ◽  
Wave Oscillation ◽  
Airway Tree

Understanding pressure wave propagation in the lung is of importance for a number of medical devices including those for diagnostics and treatments. The main objective of this research is to quantify the transmitability of the airway tree with respect to pressure oscillations. Ovine lungs are casted to produce a hollow airway tree. Variable pressure oscillations and airflow are supplied at the trachea of the casted model and pressure oscillations are measured at the bronchioles. The study indicates that pressure waves with different frequencies can be delivered to different locations of the lung by controlling the pressure oscillation source to the lung.

Validation of ATHLET Code by LOCA-Induced Pressure Wave Propagation Tests

2014 ◽  
Author(s):  
István Trosztel ◽  
Iván Tóth ◽  
György Ézsöl
Keyword(s):  
Wave Propagation ◽  
Flow Rate ◽  
Pressure Wave ◽  
High Speed ◽  
Low Frequency ◽  
Test Facility ◽  
Primary System ◽  
Pressure Waves ◽  
Test Results ◽  
System Pressure

Propagation of pressure waves inside the reactor vessel after a large break LOCA is an issue since it affects pressure drop across core internals and, as a result, induces stresses in different components, like core barrel, core structures and even fuel. For reactor safety analysis pressure wave propagation is traditionally performed by systems codes. However, strong dispersion among the calculated results calls for test results to validate the calculations. The pressure wave propagation following a larger LOCA is being systematically addressed by experiments in the PMK-2 integral-type test facility. In order to capture the high speed propagation of pressure waves special pressure transducers (capable to resolve the pressure variation with a frequency of 4 kHz) have been installed. The first four tests were conducted with rupture disks for opening the break, but a special quick opening valve will be installed for future tests, allowing the adjustment of the opening time between 12 and 50 ms. The paper presents results of validation of the ATHLET code by the test results. The low-frequency oscillation of the measured system pressure was shown to be caused by flow rate coming from the pressuriser that compensates mass lost via the break: the frequency of the oscillation was slightly under-predicted. The propagation of the first rarefaction wave from the top of the downcomer to the upper plenum is very well calculated by ATHLET: in spite of the first order discretisation no numerical diffusion can be observed. The calculated pressure differences between two different locations in the system are of primary interest, since they define the loads on primary system internals. ATHLET somewhat overestimates the amplitude of the pressure difference pulses, while it fairly well describes the frequency of oscillations. First analyses indicate an effect of the calculated break flow rate. ATHLET calculates a slower attenuation of the pressure oscillations as compared to test results. This can be the consequence of rigid walls assumed in the analysis. The tendency of increasing first pressure peak with increasing system pressure is well predicted by the code. In summary, it can be stated that ATHLET calculations produce slightly conservative results based on comparison with measured data.

Wave Propagation in Mixtures of Solids and Liquids

1980 ◽  
Vol 22 (1) ◽  
pp. 17-20
Author(s):  
A. R. D. Thorley
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Differential Equations ◽  
Numerical Method ◽  
Method Of Characteristics ◽  
Unsteady Flows ◽  
Pressure Waves ◽  
Transient Pressure ◽  
Solid Matter ◽  
Speed Of Propagation

The differential equations for conservation of mass and linear momentum in unsteady flows of slurries are developed to the point where they can be solved using the numerical method of characteristics. An approximation is introduced which permits the flow velocities of the two components to vary at different rates. Comparisons are made with new experimental data for the amplitude and speed of propagation of transient pressure waves in slurries containing up to 40 per cent by volume of solid matter.

A Vlasov equation for pressure wave propagation in bubbly fluids

2002 ◽  
Vol 454 ◽  
pp. 287-325 ◽  
Author(s):  
PETER SMEREKA
Keyword(s):  
Wave Propagation ◽  
Vlasov Equation ◽  
Pressure Wave ◽  
Bubble Dynamics ◽  
Type Equation ◽  
Nonlinear Effects ◽  
Single Bubble ◽  
Pressure Waves ◽  
General Description ◽  
Bubbly Fluids

The derivation of effective equations for pressure wave propagation in a bubbly fluid at very low void fractions is examined. A Vlasov-type equation is derived for the probability distribution of the bubbles in phase space instead of computing effective equations in terms of averaged quantities. This provides a more general description of the bubble mixture and contains previously derived effective equations as a special case. This Vlasov equation allows for the possibility that locally bubbles may oscillate with different phases or amplitudes or may have different sizes. The linearization of this equation recovers the dispersion relation derived by Carstensen & Foldy. The initial value problem is examined for both ideal bubbly flows and situations where the bubble dynamics have damping mechanisms. In the ideal case, it is found that the pressure waves will damp to zero whereas the bubbles continue to oscillate but with the oscillations becoming incoherent. This damping mechanism is similar to Landau damping in plasmas. Nonlinear effects are considered by using the Hamiltonian structure. It is proven that there is a damping mechanism due to the nonlinearity of single-bubble motion. The Vlasov equation is modified to include effects of liquid viscosity and heat transfer. It is shown that the pressure waves have two damping mechanisms, one from the effects of size distribution and the other from single-bubble damping effects. Consequently, the pressure waves can damp faster than bubble oscillations.

The Effect from Hole Area on Pressure Waves Produced by a High-Speed Train through Tunnel with Perforated Wall

2011 ◽  
Vol 94-96 ◽  
pp. 1733-1736
Author(s):  
Yuan Gui Mei ◽  
Yong Xing Jia
Keyword(s):  
Numerical Method ◽  
Pressure Wave ◽  
High Speed ◽  
Method Of Characteristics ◽  
Pressure Waves ◽  
High Speed Train ◽  
One Dimensional ◽  
Isentropic Flow ◽  
Perforated Wall ◽  
Hole Area

The perforated wall has great effect on pressure waves produced by high-speed train through a tunnel. In this paper the effect is investigated numerically by the method of characteristics based on one-dimensional unsteady compressible non-isentropic flow theory. The numerical method is validated by experimental results of Netherlands NLR. The effect from hole area in perforated wall is investigated principally and the results shows that the pressure wave is alleviated remarkably in tunnel with perforated wall.

scholarly journals Small Bubbles Generation With Swirl Bubblers for SNS Target

2018 ◽  
Author(s):  
C. Barbier ◽  
E. Dominguez-Ontiveros ◽  
R. Sangrey
Keyword(s):  
Pressure Wave ◽  
Proton Accelerator ◽  
Pressure Waves ◽  
Negative Effects ◽  
Cavitation Damage ◽  
Pressure Losses ◽  
Oak Ridge ◽  
Micron Diameter ◽  
Rapid Temperature ◽  
Small Bubbles

Oak Ridge National Laboratory’s (ORNL) Spallation Neutron Source (SNS) uses a mercury target to generate neutrons. When the powerful 1.4 MW, 60Hz proton beam hits the target, a strong pressure wave propagates in the mercury and into the vessel wall due to the rapid temperature rise in mercury. These pressure waves induce cavitation damage on the target container and high stresses, which both limit the lifetime of the target. Since October 2017, helium gas has been injected into the mercury flow in order to mitigate the negative effects of pulse-induced pressure waves. The preliminary strain measurements suggest that gas injection is indeed efficient at mitigating the pressure wave. Tiny nozzles (8-micron diameter) at choked condition are used to generate small bubbles. The bubblers can theoretically inject a total mass flow rate of 0.75 SLPM. However, during operation the bubblers were capable of injecting only approximately 0.45 SLPM, which suggests that some of the nozzles may have become clogged. Since there is a strong desire to inject a larger quantity of gas in the target to, hopefully, mitigate even more the pressure wave, SNS has been looking at implementing swirl bubblers in the target, similar to the ones used in the Japan Proton Accelerator Research Complex (J-PARC) mercury target. In this paper, results with prototypical bubblers tested in water and mercury are presented. Bubblers were installed in prototypical targets and bubble size distributions were measured in both water and mercury. It was found that swirl bubblers can generate a large number of small bubbles, but some compromises were made to keep the pressure losses across them reasonable.

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