scholarly journals Plunging Circular Jets: Experimental Characterization of Dynamic Pressures Near the Stagnation Zone

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 173
Author(s):  
Grégoire Jamet ◽  
António Muralha ◽  
José F. Melo ◽  
Pedro A. Manso ◽  
Giovanni De De Cesare
Keyword(s):  
Dynamic Pressure ◽  
Experimental Studies ◽  
Air Entrainment ◽  
Complete Characterization ◽  
Stagnation Zone ◽  
Dam Foundation ◽  
Flow Energy ◽  
Plunge Pool ◽  
Circular Jets ◽  
Dynamic Pressure Measurements

Spillways are a requirement for dams’ safety, mainly preventing overtopping during floods. A common spillway solution involves plunging jets, which dissipate a considerable flow energy in the plunge pool. Energy dissipation has to occur in a controlled manner to avoid endangering the dam foundation and river slopes. Indeed, a scouring process in the downstream riverbed will inevitably develop until equilibrium is reached, otherwise a suitable pre-excavated or concrete lined plunge pool has to be provided. This paper focuses on experimental studies in which particular attention was paid to the dynamic pressures in the plunge pool floor at the vicinity of the jet stagnation zone sampled at 2.4 kHz. A rectangular experimental facility, 4.00 m long and 2.65 m wide, was used as plunge pool. Tests involved a vertical circular plunging jet with velocity ranging from 5 to 18 m/s and plunge pool depth ranging from 4.2 to 12.5 jet diameters. Differences in dynamic pressure measurements are highlighted between transducers located in the inner and outer regions of the jet diameter footprint. Several parameters characterizing the dynamic pressures evidence trends tied with the jet velocity that, to the authors’ knowledge, were not dealt in previous research. These can derive from the coupling effects of consequent recirculating motions and air entrainment in the limited-size plunge pool. Both effects, increasing with velocity, cause an reduction in the efficiency of the diffusing jet shear layer. This aspect deserves further investigation to achieve a better understanding and more complete characterization.

scholarly journals Reproducibility of C. I. P.-compatible dynamic pressure measurements

2020 ◽  
Vol 87 (10) ◽  
pp. 630-636
Author(s):  
Oliver Slanina ◽  
Susanne Quabis ◽  
Robert Wynands
Keyword(s):  
Dynamic Pressure ◽  
Storage Conditions ◽  
Dynamic Measurement ◽  
Gas Pressure ◽  
Pressure Measurements ◽  
Small Arms ◽  
Minimum Pressure ◽  
Maximum Value ◽  
Preliminary Study ◽  
Dynamic Pressure Measurements

AbstractTo ensure the safety of users like hunters and sports shooters, the dynamic pressure inside an ammunition cartridge must not exceed a maximum value. We have investigated the reproducibility of the dynamic measurement of the gas pressure inside civilian ammunition cartridges during firing, when following the rules formulated by the Permanent International Commission for the Proof of Small Arms (C. I. P.). We find an in-house spread of 0.8 % between maximum and minimum pressure for runs with the same barrel and of 1.8 % among a set of three barrels. This sets a baseline for the expected agreement in measurement comparisons between different laboratories. Furthermore, a difference of more than 3 % is found in a preliminary study of the influence of ammunition storage conditions.

Application of side-hole fibers for dynamic pressure measurements

2000 ◽  
Author(s):  
Wojtek J. Bock ◽  
Magdalena S. Nawrocka ◽  
Waclaw Urbanczyk
Keyword(s):  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Side Hole ◽  
Dynamic Pressure Measurements

Distribution of Flow Across the Radius of an Axisymmetric Shock Tube With Variable Cross-Sectional Area

1991 ◽  
Author(s):  
Stephen J. Schraml ◽  
Richard J. Pearson
Keyword(s):  
Shock Tube ◽  
Dynamic Pressure ◽  
Computer Code ◽  
Turbulence Modelling ◽  
Variable Cross ◽  
Cross Sectional ◽  
Flow Simulations ◽  
First Order ◽  
Series Of Experiments ◽  
Dynamic Pressure Measurements

Abstract Experiments were conducted to study the characteristics of unsteady flow in a small, axisymmetric shock tube. These experiments have been supplemented by calculational results obtained from the SHARC hydrodynamic computer code. Early calculational results indicated that a substantial gradient in flow velocity and dynamic pressure may exist along the cross-section of the shock tube. To further investigate this phenomenon, a series of experiments was performed in which dynamic pressure measurements were made at various radii in the expansion section of the shock tube. Additional calculations with the SHARC code were also performed in which turbulence modelling, artificial viscosity and second order advection were employed. The second set of calculations agree very well with the experimental results. These results indicate that the dynamic pressure is nearly constant across the radius of the shock tube. This contradicts the early computational results which were performed with first order advection and without turbulence modelling. As a result of these findings, it was concluded that turbulence modelling was necessary to obtain accurate shock tube flow simulations.

Measurements of Multiple Pure Tone Propagation From a High Bypass Turbofan Rotor in an Internal Flow Facility

2020 ◽  
Author(s):  
Richard F. Bozak
Keyword(s):  
Pure Tone ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Principal Component ◽  
Pressure Transducers ◽  
Acoustic Liners ◽  
Pure Tones ◽  
Dynamic Pressure Measurements ◽  
Stagger Angle

Abstract An important noise source in modern high bypass ratio turbofans is from multiple pure tones produced by the fan during takeoff. An experiment conducted on a 1.5 pressure ratio fan in an internal flow facility provided dynamic pressure measurements to investigate multiple pure tone generation and propagation. Since multiple pure tones are generated by blade shock variation primarily due to the fan’s blade stagger angle differences, the blade stagger angles were measured with an array of over-the-rotor dynamic pressure transducers. Multiple pure tone measurements were made with 30 wall-mounted dynamic pressure transducers from 0.4 to 1.1 diameters upstream of the rotor. Measured blade stagger angle differences correspond to the the shock amplitude variation measured upstream. The acoustic field was extracted from the dynamic pressure signals using principal component analysis as well as duct mode beamforming. Shocks traveling out the inlet were found to couple to duct modes propagating at similar angles. Over-the-rotor acoustic liners appear to reduce rotor shock variation resulting in a reduction of sub-harmonic multiple pure tone sound pressure levels by 3–4 dB.

Highly sensitive fiber optic sensor for dynamic pressure measurements

1999 ◽  
Author(s):  
Magdalena S. Nawrocka ◽  
Wojtek J. Bock ◽  
Waclaw Urbanczyk ◽  
Jan Wojcik
Keyword(s):  
Fiber Optic ◽  
Dynamic Pressure ◽  
Fiber Optic Sensor ◽  
Pressure Measurements ◽  
Optic Sensor ◽  
Highly Sensitive ◽  
Dynamic Pressure Measurements

Experimental Study on Pressure Fluctuations in the Boundary Layer of an Axisymmetric Body

2011 ◽  
Vol 66-68 ◽  
pp. 1488-1493
Author(s):  
Hong Xiao ◽  
Chao Gao ◽  
Zhen Kun Ma
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Mach Number ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Axisymmetric Body ◽  
Pressure Measurements ◽  
Fluctuating Pressure ◽  
Frequency Domains ◽  
Dynamic Pressure Measurements

The characteristics of the fluctuating pressure in the boundary layer of an axisymmetric body have been investigated experimentally using dynamic pressure measurements and Schlieren photograghs. Data were acquired at subsonic and super-sonic Mach numbers. The angles of attack ranged from 0° to 5°. Pressure signals were measured simultaneously in several positions along the model and were analyzed both in the time and frequency domains. The Mach number shows the relevant influence on . Furthermore, the pressure fluctuations’ level decreases with the increasing of Mach number except M=1.15. And it is shown that, the location along the axis of the model and the angles of attack have small effect on pressure fluctuations.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hessam Vatandoust ◽  
Hamidreza Yarmohammadi ◽  
Mohammadreza Kavianpour
Keyword(s):  
Froude Number ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Flow Speed ◽  
Middle Part ◽  
Statistical Characteristics ◽  
Pressure Coefficients

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Frequency Response Characterization for Dynamic Measurement of Pressure

2019 ◽  
Author(s):  
George Papadopoulos ◽  
Daniel Bivolaru
Keyword(s):  
Frequency Response ◽  
Dynamic Pressure ◽  
Harsh Environments ◽  
Measured Signal ◽  
Sensing Element ◽  
Optimum Frequency ◽  
Size Constraints ◽  
Dynamic Pressure Measurements ◽  
Point Level ◽  
Transducer Frequency

Abstract Transducer requirements for making true dynamic pressure measurements point to a miniature point-level sensing element that is exposed to the flow. Meeting this requirement, however, is often challenged by transducer size constraints, integration at the location of measurement, and packaging, especially when one considers applications in harsh environments where protection of the sensing element may be needed. As part of an effort towards the development of a high frequency pressure measurement device for use in harsh environments (ultra-high temperature), an investigation was performed to evaluate the effect of sensing element packaging and geometry at the point of measurement on the dynamic response of a nominal transducer. Frequency and time domain calculations were performed to assess variations on the magnitude and phase between an input signal and a “measured” signal at the sensing element location for a range of probe tip parameters. The results offer insights and metrics that can govern transducer sensing element and probe tip implementation for optimum frequency response and strategies for compensation.

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