Diaphragm Opening Research Articles

AEROACOUSTIC RESPONSE OF A SLIT-SHAPED DIAPHRAGM IN A PIPE AT LOW HELMHOLTZ NUMBER, 1: QUASI-STEADY RESULTS

The aeroacoustic response of a diaphragm in a pipe is studied by means of an analytical model and experimental measurements. The study is restricted to quasi-two-dimensional diaphragms with a sharp-edged rectangular aperture at conditions for which the acoustic source region can be considered compact. The compactness of the source can be realized under two conditions: either a low Strouhal number and a jet Mach number of the order unity; or a low jet Mach number and a Strouhal number of order unity. In this paper, the focus is on the first case. The second case of low Mach number and Strouhal number of order unity is discussed in a companion paper. The results of a quasi-steady theory are compared with measurements of the reflection and transmission coefficients of a diaphragm. The theoretical model is based on Ronneberger's model for a step-wise expansion (D. Ronneberger 1967, Acustica19, 222–235) and Bechert's description of an orifice used as an anechoic pipe termination (Bechert 1980 Journal of Sound and Vibration70, 389–405). An important phenomenon associated with the flow through a diaphragm is the so-called vena contracta effect. This effect is analyzed theoretically as a function of diaphragm opening and jet Mach number by using analytical results for a Borda tube. This allows the use of the theory up to Mach numbers of unity in the free jet downstream of the diaphragm. It is shown that at low frequencies the model and the experimental results are in good agreement. Significant deviations appear only when the Strouhal number reaches unity.

The thermodynamic properties of erosion plasma produced by diaphragm discharge in jets in vacuum

An experimental study is made of the thermodynamic properties of plasma flowing from the orifice of a plasma-forming diaphragm as a function of the size of the orifice of the diaphragm made of textolite (C37H47O16) under conditions of a diaphragm discharge in jets in vacuum (P init = 13.3-1.3 Pa). The data are obtained for a fixed energy supply in a wide range of variation of the diaphragm opening size, namely, the diaphragm thicknessl 0 = 2.0–20.0 mm and the diameter of the orifice 2r 0 = 2.0–12.0 mm. The increase of pressure and temperature in the jet is shown to slow down with an increase of the thicknessl 0 with the constant diameter of the diaphragm orifice 2r 0.

A computational study of shock speeds in high-performance shock tubes

This paper describes U2DE, a finite-volume code that numerically solves the Euler equations. The code was used to perform multi-dimensional simulations of the gradual opening of a primary diaphragm in a shock tube. From the simulations, the speed of the developing shock wave was recorded and compared with other estimates. The ability of U2DE to compute shock speed was confirmed by comparing numerical results with the analytic solution for an ideal shock tube. For high initial pressure ratios across the diaphragm, previous experiments have shown that the measured shock speed can exceed the shock speed predicted by one-dimensional models. The shock speeds computed with the present multi-dimensional simulation were higher than those estimated by previous one-dimensional models and, thus, were closer to the experimental measurements. This indicates that multi-dimensional flow effects were partly responsible for the relatively high shock speeds measured in the experiments.

Exceptional increases in electron cone output as the backup diaphragms are opened.

Some linac manufacturers provide cones for defining circular electron fields. During commissioning of one of our new radiotherapy units, we noted that the output of these cones has a strong dependence on the diaphragm opening that precedes the cone. In particular, for the 8 MeV beam, the output of a 3 cm diameter cone increased by more than a factor of 2 as the diaphragm was opened from 5 x 5 to 20 x 20 cm. One concludes that the particular mechanical design results in an output factor dependency that is exceptional when compared to the data presented in standard texts such as Khan's "The Physics of Radiation Therapy." The importance of quality assurance and communications with the manufacturer is underscored by this example.

Analysis of the second stage of the STAR 28 mm two-stage light gas gun

An engineering model of the second stage operation of the 28 mm two-stage light gas gun at the Shock Technology and Applied Research (STAR) facility of Sandia National Laboratories has been developed. It describes the piston motion and loading of the accelerated reservoir (AR) and the coupled projectile motion. The model was developed to better assess the safety of the AR and to determine the significance of various parameters to the gun performance. Validity of the model is supported by calculated results that compare closely with projectile velocity data over a range of piston masses, piston velocities, and projectile masses and correlate satisfactorily with AR diameter growth data in a typical high-performance test. For this test, bounds on the factor of safety (FS) for the piston velocity are determined to be 1.3 < FS < 1.5. Results indicate that the projectile velocity can be increased and the AR loading reduced by changes in the piston density and break diaphragm opening pressure.

Pars sternalis diaphragmatic hernia with omphalocele: A report of two cases

A rare type of congenital diaphragmatic hernia occurs in which there is a large opening in the anterior diaphragm between the pericardial and peritoneal cavities without a sac. This hernia is invariably associated with defects in the anterior abdominal wall and with sternal defects. More commonly, it is associated with cardiac anomalies as in the Pentalogy of Cantrell. The etiology of this hernia is undoubtedly different from the more common hernia of Morgangni, which has a sac and few associated anomalies. The etiology may be failure of fusion of the pars sternis area of the septum transversum. Only five other cases have been described.

The iris diaphragm model of centriole and basal body formation

This paper suggests that the formation and structure of the microtubular skeleton of centrioles and basal bodies can be derived from the following simple geometric principle. A closed ring of nine microtubular initiation sites defines (1) a template for the packing of 18 additional microtubular initiation sites, and (2) the shape of nine rigid arms. Upon swivelling of each arm around a point located four initiation sites away on the initial ring, the array unfolds in a manner similar to the opening of an iris diaphragm. As a consequence, the curved shape of the microtubular triplet blades arises together with the clockwise rotational sense of the slanted blades of the centriole or basal body. The final diameter of the centriole (basal body) self-adjusts. Furthermore, the pitch of the triplet blades, the taper of centrioles and basal bodies, and the change of slant of the blades towards the distal end can be derived. In addition, the model points to a method of replication of pro-centrioles (pro-basal bodies). The hypothesis was tested by the fitting of electron microscopical cross sections of centrioles of 3T3 cells to the geometric shapes predicted by the model.

Fundamental mode distribution in a diaphragmed cavity

It is well known that if a circular aperture is placed inside a laser cavity, the resonant field spatial distribution is different from the Gaussian distribution. In this paper, the authors study the radial distribution of the resonant field progressive components, and show that the latter are characterised by distinct widths. The values of these widths depend on the diaphragm opening. To compute the resonant field distribution, they use a numerical method based on a field expansion in terms of a set of Gauss-Laguerre functions.

Successful closure of bronchopleural fistula by omental pedicle flap in patients with tuberculosis and chronic empyema

Bronchopleural fistulae were successfully closed by omental pedicle flaps in six patients with tuberculosis and chronic empyema. Two had tuberculous empyema and four had chronic empyema as sequelae of pulmonary tuberculosis. A pedicle of omentum containing the right epigastric artery was passed through an opening in the anterior diaphragm into the empyema cavity. It was fixed by sutures to the bronchopleural fistulae and filled in the interstices of the empyema cavity. Two patients underwent postmortem evaluation after dying from respiratory failure 7 and 15 months postoperatively. There was no necrosis or infection in the pedicled omentum. Histologic examination revealed ciliated epithelium of the inner wall of the omentum in the bronchopleural fistula. We believe the omental pedicle flap is a promising method of treating long-standing bronchopleural fistula, i.e. tuberculosis-related chronic empyema.

Mechanically operable acoustic filter

A mechanically operable acoustic filter for varying the acoustic spectrum of transmitted sound signals. Sound signals, e.g. from a patient's skin when the filter is incorporated into the chest piece of a stethoscope, are received at an inlet orifice which may or may not be provided with an outer diaphragm. A thin, preferably Mylar filtering diaphragm partitions the interior of the chest piece into two chambers communicating with respective inlet and outlet orifices and each other through a central opening in the filtering diaphragm in line with a central passageway in a tensioning member for the filtering diaphragm. The position of the tensioning member is adjustable by a knob disposed outside the chest piece between a first position in which all frequencies pass by way of the central opening and successive positions in which the diaphragm is correspondingly tensioned at the same time the free vibrating area thereof is reduced.

Process of opening of an inelastic diaphragm in a shock tube

Process of opening of an inelastic diaphragm in a shock tube

Unsteady Two-Dimensional Flow in a Shock Tube Caused by Diaphragm Opening : 2nd Report, Quasi-One-Dimensional Flow Model and Averaged Flow Behavior

Unsteady Two-Dimensional Flow in a Shock Tube Caused by Diaphragm Opening : 2nd Report, Quasi-One-Dimensional Flow Model and Averaged Flow Behavior

Influence of the diaphragm opening process on the initial flow in shock-tubes

Influence of the diaphragm opening process on the initial flow in shock-tubes

Unsteady Two-Dimensional Flow in a Shock Tube Caused by Diaphragm Opening : 1st Report, Experimental Study and Finite Difference Analysis

Unsteady Two-Dimensional Flow in a Shock Tube Caused by Diaphragm Opening : 1st Report, Experimental Study and Finite Difference Analysis

Simple Technique for Predicting Type 11 and IV Shock Interference

3 Simpson, C. J. S. M, Chandler, T. R. D., and Bridgman, K. B., Measurements of the Opening Times of Diaphragms in a Shock Tube and the Effects of the Opening Process on Shock Trajectories, Aero Rept. 1194, 1966, National Physical Lab., Teddington, Middlesex, England. 4 Drewry, J. E. and Walenta, Z. A., Determination of Diaphragm Opening-Times and Use of Diaphragm Particle Traps in a Hypersonic Shock Tube, TN 90, 1965, University of Toronto, Institute for Aerospace Studies, Toronto, Canada. 5 Kirev, V. T., On Motion of a Shock Wave During Noninstantaneous Opening of Diaphragm in Shock Tube, News of Academy of Science USSR, Technology Section, Mechanics and Mechanical Engineering, No. 6, 1962, pp. 144-146. 6 Sandeman, R. J. and Alien, G. H., A Double Diaphragm Shock Tube for the 10-20 km/sec Range, Proceedings of the Eighth International Shock Tube Symposium, edited by J. L. Stollery, A. G. Gaydon, and P. R. Owen, Chapman and Hall, London, England, 1971. 7 Glass, I. I, Chan, S. K, and Erode, H. L., Strong Planar Shock Waves Generated by Explosively-Driven Spherical Implosions, A1AA Journal, Vol. 12, No. 3, March 1974, pp. 367-374. 8 Chan, S. K., An Analytical and Experimental Study of an Implosion-Driven Shock Tube, Rept. 191,1973, University of Toronto, Institute for Aerospace Studies, Toronto, Canada. 9 Weiss, V., ed., Aerospace Structural Metals Handbook, Vol. 1: Ferrous Alloys, Syracuse University Press, Syracuse, N.Y., 1963.

Diaphragm opening process in shock tubes

An experimental study of the diaphragm opening process for various types of diaphragms and shock tube configurations is presented. A qualitative description of the opening process is given. A normalized curve is presented which permits prediction of the functional dependence of the diaphragm opening aperture with time for different experimental conditions.

Propagation accelerée d'une onde de choc en tube à choc

The acceleration of a shock wave in the first part of a shock tube is measured and calculated as a function of the diaphragm opening time.

Low Attenuation Shock Tube: Driving Mechanism and Diaphragm Characteristics

The properties of an electric shock tube fitted with a diaphragm are examined. The diaphragm opening process and its effect on the motion of the shock wave are studied. A simple model to account for the diaphragm opening time is given and critical comparisons of theory and results with other work are made.The model works well both for shock tubes employing room temperature driver gas and also for those using heated driver gas. Furthermore, there is strong evidence that the diaphragm opening process is responsible for the accelerating phase of the shock wave motion in both types of shock tube.

Shock Tunnel Operation with an Expansive Area Change at the Main Diaphragm

The use of an expansive area change immediately following the diaphragm has afforded considerable convenience in shock tube applications and has been studied by a number of authors. It allows the use of a smaller diaphragm, thereby reducing the disturbance to the shock tube flow caused by the diaphragm opening, and it also permits greater flexibility in the choice of driver section configurations for a given shock tube size.It is natural to consider the extension of this idea to shock tunnel operation. This has been encouraged by the possibility of applying area change to operation of an arc-driven shock-tunnel. Some early success in employing arc-heated drivers for shock tunnels has been reported by Warren et al. However, the configuration they studied employed a long driver section to achieve correspondingly long test times. In addition, to achieve a constant shock velocity it was necesssary that electrical energy was added so that the gas was heated uniformly before the diaphragm ruptured. This necessitated a fast discharge condenser bank, with a high discharge voltage, the latter to enable an arc to be sustained over the length of the driver section. In the present application, a constriction between the driver section and the shock tube is employed, allowing the driver section to be treated as a constant pressure reservoir of gas. It is anticipated that this will allow the use of shorter drivers, thereby permitting the adoption of lower discharge voltages, and will also allow energy to be added relatively slowly while the shock tunnel is operating. This will produce substantial economies in provision of the large energy storage facilities required for shock-tunnel operation.

A novel use of a telescope to photograph metal diaphragm openings.

Image converter camera and astronomical telescope arrangement for photographing metal diaphragm openings in shock tube