Experimental Investigations of Incipient and Desinent Cavitation

1964 ◽  
Vol 86 (2) ◽  
pp. 275-281 ◽  
Author(s):  
A. F. Lehman ◽  
J. O. Young
Keyword(s):  
High Speed ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Minimum Area ◽  
Internal Contour ◽  
Throat Region ◽  
Smooth Contour ◽  
Contour Change ◽  
Cylindrical Throat ◽  
Onset Of Cavitation

Experiments with water in a high speed recirculating water tunnel were undertaken to measure the pressures at which incipient and desinent cavitation occurred. Incipient cavitation is defined as the onset of cavitation; desinent cavitation is defined as the cessation of cavitation. The two lucite test sections used formed the minimum area region of the nozzle in the water tunnel. One test section had a smoothly changing internal contour and the other had an abrupt contour change at the entrance to the cylindrical throat region. Cavitation in the abrupt contour occurred at the throat entrance at higher pressures than the cavitation pressures in the smooth contour. The cavitation in the smooth contour occurred at the entrance to the diffuser part of the nozzle. It was concluded that the cavitation pressures and cavitation numbers increased with velocity, the increase being greater for the abrupt contour with the exception of minimums indicated at incipient conditions in the abrupt contour at throat velocities near 88 ft/sec. A notable difference between the incipient and desinent cavitation numbers and pressures occurred for the abrupt contour, but not for the smooth contour using the techniques described for identifying the incipient and desinent cavitation regimes.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

scholarly journals Numerical and Experimental Investigations on Vocal Fold Approximation in Healthy and Simulated Unilateral Vocal Fold Paralysis

2021 ◽  
Vol 11 (4) ◽  
pp. 1817
Author(s):  
Zheng Li ◽  
Azure Wilson ◽  
Lea Sayce ◽  
Amit Avhad ◽  
Bernard Rousseau ◽  
...  
Keyword(s):  
Computational Model ◽  
Vocal Fold ◽  
High Speed ◽  
Computational Models ◽  
Ex Vivo ◽  
Vocal Fold Paralysis ◽  
Future Application ◽  
Experimental Investigations ◽  
Type I ◽  
Mri Scans

We have developed a novel surgical/computational model for the investigation of unilat-eral vocal fold paralysis (UVFP) which will be used to inform future in silico approaches to improve surgical outcomes in type I thyroplasty. Healthy phonation (HP) was achieved using cricothyroid suture approximation on both sides of the larynx to generate symmetrical vocal fold closure. Following high-speed videoendoscopy (HSV) capture, sutures on the right side of the larynx were removed, partially releasing tension unilaterally and generating asymmetric vocal fold closure characteristic of UVFP (sUVFP condition). HSV revealed symmetric vibration in HP, while in sUVFP the sutured side demonstrated a higher frequency (10–11%). For the computational model, ex vivo magnetic resonance imaging (MRI) scans were captured at three configurations: non-approximated (NA), HP, and sUVFP. A finite-element method (FEM) model was built, in which cartilage displacements from the MRI images were used to prescribe the adduction, and the vocal fold deformation was simulated before the eigenmode calculation. The results showed that the frequency comparison between the two sides was consistent with observations from HSV. This alignment between the surgical and computational models supports the future application of these methods for the investigation of treatment for UVFP.

Investigation of Ventilation Monitoring and Controlling System for Supercavitation Experiment in the Water-Tunnel Based on Configuration Software

2014 ◽  
Vol 556-562 ◽  
pp. 3219-3222
Author(s):  
Shan Shan Li ◽  
Peng Wang ◽  
Xu Han ◽  
Jin Feng Liu ◽  
Xiao Gang Zhou
Keyword(s):  
High Speed ◽  
Configuration Software ◽  
Water Tunnel ◽  
Controlling System ◽  
Ventilation Monitoring ◽  
The Future ◽  
Numerous Data ◽  
And Control ◽  
Monitor And Control

The supercavitation weapon is a new concept weapon moving at a high speed underwater, which is devised applying the characteristic of supercavitation reducing the resistance of water, and it may be widely used in the future. The present ventilating system has many shortcomings, such as less automation and numerous data cannot be measured and recorded timely. In this paper, the automatic monitor and control ventilating system of supercavitation water-tunnel was developed using configuration software and PLC. All parameters can be measured, recorded and displayed automatically via using of the system. It has many advantages such as higher automation, convenience, and easy maintenance.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

scholarly journals Improved operator agreement and efficiency using the minimum area contour change method for delineation of hyperintense multiple sclerosis lesions on FLAIR MRI

2013 ◽  
Vol 13 (1) ◽  
Author(s):  
David S Wack ◽  
Michael G Dwyer ◽  
Niels Bergsland ◽  
Deepa Ramasamy ◽  
Carol Di Perri ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Minimum Area ◽  
Contour Change

scholarly journals Prechamber optimal selection for a two stage turbulent jet ignition type combustion system in CNG-fuelled engine

2019 ◽  
Vol 176 (1) ◽  
pp. 16-26 ◽  
Author(s):  
Ireneusz PIELECHA ◽  
Wojciech BUESCHKE ◽  
Maciej SKOWRON ◽  
Łukasz FIEDKIEWICZ ◽  
Filip SZWAJCA ◽  
...  
Keyword(s):  
High Speed ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Optimization Methods ◽  
Turbulent Jet ◽  
Experimental Investigations ◽  
Combustion System ◽  
Two Stage ◽  
Lean Burn ◽  
High Speed Engine

Searching for further reduction of fuel consumption simultaneously with the reduction of toxic compounds emission new systems for lean-mixture combustion for SI engines are being discussed by many manufacturers. Within the European GasOn-Project (Gas Only Internal Combustion Engines) the two-stage combustion and Turbulent Jet Ignition concept for CNG-fuelled high speed engine has been proposed and thoroughly investigated where the reduction of gas consumption and increasing of engine efficiency together with the reduction of emission, especially CO2 was expected. In the investigated cases the lean-burn combustion process was conducted with selection of the most effective pre-combustion chamber. The experimental investigations have been performed on single-cylinder AVL5804 research engine, which has been modified to SI and CNG fuelling. For the analysis of the thermodynamic, operational and emission indexes very advanced equipment has been applied. Based on the measuring results achieved for different pre-chamber config-urations the extended methodology of polioptimization by pre-chamber selection and the shape of main chamber in the piston crown for proposed combustion system has been described and discussed. The results of the three versions of the optimization methods have been comparatively summarized in conclusions.

scholarly journals MEASURING DISPLACEMENT AND VELOCITY OF A STRIKER USING A RADIO-INTERFEROMETER

2019 ◽  
Vol 81 (1) ◽  
pp. 118-128
Author(s):  
V. V. Balandin ◽  
V. V. Balandin ◽  
V. V. Parkhachev
Keyword(s):  
High Speed ◽  
Radio Interferometer ◽  
Experimental Investigations ◽  
X Ray ◽  
Gas Gun ◽  
Impact Interaction ◽  
Ballistic Experiment ◽  
Wide Range ◽  
Series Of Experiments ◽  
Error Of Measurement

Investigating impact interaction of solid and deformed bodies with obstacles of various physical natures requires developing experimental methodologies of registering the parameters of the interaction process. In experimental investigations of impact interaction of solids, it is common practice to measure displacement of strikers as a function of time, as well as their velocity and deceleration. To determine the displacement and velocity of a striker, a radio-interferometric methodology of registering the displacement of its rear end is proposed. In contrast with the registration methods based on high-speed filming and pulsed X-ray photography, the method using a millimeter-range radio-interferometer provides continuous high-accuracy registering of the displacement of the rear end of a striker in a wide range of displacement values. To test the effectiveness of the methodology, a series of experiments have been conducted on registering the motion of a cylindrical striker of an aluminum alloy, fired from a 20mm-dia gas gun. The displacement of the striker was also monitored using high-speed filming. The results of measuring using the two methodologies differ within the limits of the error of measurement. Based on the results of the above experiments, it has been concluded that the methodology of determining the displacement and velocity of strikers in a ballistic experiment using a mm-range radio-interferometer makes it possible to measure practically continuously large displacements (100 mm and larger) to a safe accuracy. The present methodology can be used for measuring the displacement and velocity of the rear end of a striker interacting with obstacles of various physical natures (metals, ceramics, soils, concretes, etc.).

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2020 ◽  
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 2·105) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1D-CTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probe measurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

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