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.

Hydraulic Circuit Design Keys to Remove the Dependence of the Injected Fuel Amount on Dwell Time in Multi-Jet C.R. Systems

2006 ◽  
Author(s):  
Mirko Baratta ◽  
Andrea Emilio Catania ◽  
Alessandro Ferrari
Keyword(s):  
Circuit Design ◽  
Pressure Wave ◽  
High Performance ◽  
Dwell Time ◽  
Performance Test ◽  
Pressure Oscillation ◽  
Operating Conditions ◽  
Injection System ◽  
Hydraulic Circuit ◽  
Pressure Oscillations

In Multijet Common Rail (C.R.) systems, the capability to manage multiple injections with full flexibility in the choice of the dwell time (DT) between consecutive solenoid current pulses is one of the most relevant design targets. Pressure oscillations triggered by the nozzle closure after each injection event induce disturbances in the amount of fuel injected during subsequent injections. This causes a remarkable dispersion in the mass of fuel delivered by each injection shot when DT is varied. The present works aims at investigating hydraulic circuit design keys to improve multiple injection performance of C.R. systems, by virtually removing the dependence of the injected fuel amount on DT. A Multi-Jet C.R. of the latest solenoid-type generation was experimentally tested at engine-like operating conditions on a high performance test bench. The considerable influence that the injector supplying pipe can exert on induced pressure oscillation frequency and amplitude was widely investigated and a physical explanation of cause-effect relationships was found by energetics considerations, starting from experimental tests. An optimization study was carried out to identify the best geometrical configurations of the injector supplying pipes so as to minimize pressure oscillations. The analysis was carried out with the aid of a previously developed simple zero-dimensional model, allowing the evaluation of pressure wave frequencies as functions of main system geometric data. Purposely designed orifices were introduced into the rail-pipe connectors or at the injector inlet, so as to damp pressure oscillations. Their effects on injection system performance were experimentally analyzed. Hydraulic circuit solutions that apply both optimized injector inlet-pipe sizes and oscillation damping orifices at the rail outlet were thoroughly investigated. Finally, the influence of the rail volume on pressure wave dynamics was studied to evaluate the possibility of severely reducing the rail capacitance. This would lead to a system, not only with reduced overall dimensions, but also with a prompter dynamic response during engine transients.

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.

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.

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.

scholarly journals Pressure wave propagation in a granular bed

2005 ◽  
Vol 72 (3) ◽  
Author(s):  
Stephen R. Hostler ◽  
Christopher E. Brennen
Keyword(s):  
Wave Propagation ◽  
Pressure Wave ◽  
Granular Bed

scholarly journals Pressure wave propagation in bubbly liquid.

1990 ◽  
Vol 56 (525) ◽  
pp. 1237-1243
Author(s):  
Yoichro MATSUMOTO ◽  
Hideji NISHIKAWA ◽  
Hideo OHASHI
Keyword(s):  
Wave Propagation ◽  
Pressure Wave ◽  
Bubbly Liquid
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