scholarly journals Influence of Vapor-Gas Cavity on Pressure Field in Closed Discharge Chamber with Rigid Walls

2021 ◽  
Vol 57 (3) ◽  
pp. 102-116
Author(s):  
V. Kosenkov ◽  
Keyword(s):  
Mathematical Model ◽  
Electric Discharge ◽  
Moving Boundary ◽  
Discharge Chamber ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Great Influence ◽  
Alloy Plate ◽  
Gas Cavity ◽  
Rigid Walls

The pressure field in discharge chambers of a limited volume with deformable walls very often has a great influence on the efficiency of technological processes of deformation of sheet alloys; therefore, its determination is an urgent task. As a result of an electric discharge in the liquid filling the discharge chamber, in it, a cavity with a higher compressibility is formed than the liquid in the chamber. At the stage of the discharge, this cavity is filled with non-ideal plasma, and after the discharge, with liquid vapor and gases dissolved in it (vapor-gas cavity). Its pulsations form a pressure field in the discharge chamber. The moving boundary of the vapor-gas cavity creates great problems in calculating the pressure field in a liquid, especially after a large number of its pulsations. At present, the role of the vapor-gas cavity in the formation of the pressure field in the discharge chamber with a deformable wall, which is a sheet alloy plate, is insufficiently studied. Its definition is the purpose of this work. The study was carried out on the base of a previously developed mathematical model of an electric discharge in water, which in this work is supplemented with relations that significantly increase the accuracy of calculating the resistance of the discharge channel and the energy released in it. It was determined that the pulsations of the vapor-gas cavity provide pressure fluctuations in it in an antiphase with the average pressure in the liquid. In a discharge chamber with rigid walls, they decay slowly, but the presence of a deformable wall leads to a rapid decay of pressure fluctuations. In the previously developed mathematical model, the change in the optical transparency of the plasma was taken into account, and its significant effect on the pressure in the cavity and the pressure field in the liquid was determined.

A mathematical model for heterogeneous reactions with a moving boundary

AIChE Journal ◽  
1989 ◽  
Vol 35 (4) ◽  
pp. 625-634 ◽  
Author(s):  
Kareem I. Batarseh ◽  
Glenn P. Swaney ◽  
Alfred H. Stiller
Keyword(s):  
Mathematical Model ◽  
Moving Boundary ◽  
Heterogeneous Reactions

Computing Micro Synthetic Jet in Slip Regime With Moving Membrane

2002 ◽  
Author(s):  
A. Rustem Aslan ◽  
Oktay Baysal ◽  
Firat O. Edis
Keyword(s):  
Moving Boundary ◽  
Pressure Field ◽  
Wall Slip ◽  
Synthetic Jet ◽  
Navier Stokes ◽  
Rarefied Flows ◽  
Flow Simulations ◽  
Slip Regime ◽  
Velocity Magnitude ◽  
Primary Focus

A Navier-Stokes (NS) solver for moving and deforming meshes has been modified to investigate numerically the diaphragm-driven flow in and out of two synthetic jet cavity geometries. The piezoelectric-driven diaphragm of the cavity is modeled in a realistic manner as a moving boundary to accurately compute the flow inside the jet cavity. The primary focus of the present paper is to describe the effect of cavity geometry and the wall slip, resulting from the relatively larger Kn number flows associated with micro sized geometries, on the exit jet velocity magnitude. Compressible flow simulations are required for rarefied flows to accurately predict the pressure field. The present computations for the quiescent external flow condition reveal that cavity geometry and the wall slip has an increasing effect on the magnitude of the average jet exit velocity as well as vortex shedding from the orifice.

Unsteady Flow Structure on a Centrifugal Pump: Experimental and Numerical Approaches

2002 ◽  
Author(s):  
Jose´ Gonza´lez ◽  
Carlos Santolaria ◽  
Eduardo Blanco ◽  
Joaqui´n Ferna´ndez
Keyword(s):  
Numerical Model ◽  
Centrifugal Pump ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Side Wall ◽  
Relative Effect ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Blade Passing Frequency ◽  
Wide Range

Both experimental and numerical studies of the unsteady pressure field inside a centrifugal pump have been carried out. The unsteady patterns found for the pressure fluctuations are compared and a further and more detailed flow study from the numerical model developed will be presented in this paper. Measurements were carried out with pressure transducers installed on the volute shroud. At the same time, the unsteady pressure field inside the volute of a centrifugal pump has been numerically modelled using a finite volume commercial code and the dynamic variables obtained have been compared with the experimental data available. In particular, the amplitude of the fluctuating pressure field in the shroud side wall of the volute at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Once the developed numerical model has shown its capability in describing the unsteady patterns experimentally measured, an explanation for such patterns is searched. Moreover, the possibilities of the numerical model can be extended to other sections (besides the shroud wall of the volute), which can provide plausible explanations for the dynamic interaction effects between the flow at the impeller exit and the volute tongue at different axial positions. The results of the numerical simulation are focused in the blade passing frequency in order to study the relative effect of the two main phenomena occurring at that frequency for a given position: the blade passing in front of the tongue and the wakes of the blades.

Proper Orthogonal Decomposition and Extended- Proper Orthogonal Decomposition Analysis of Pressure Fluctuations and Vortex Structures Inside a Steam Turbine Control Valve

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Peng Wang ◽  
Hongyu Ma ◽  
Yingzheng Liu
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Steam Turbine ◽  
Pressure Fluctuation ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Control Valve ◽  
Vortex Structures ◽  
Orthogonal Decomposition ◽  
Pod Analysis ◽  
Proper Orthogonal

In steam turbine control valves, pressure fluctuations coupled with vortex structures in highly unsteady three-dimensional flows are essential contributors to the aerodynamic forces on the valve components, and are major sources of flow-induced vibrations and acoustic emissions. Advanced turbulence models can capture the detailed flow information of the control valve; however, it is challenging to identify the primary flow structures, due to the massive flow database. In this study, state-of-the-art data-driven analyses, namely, proper orthogonal decomposition (POD) and extended-POD, were used to extract the energetic pressure fluctuations and dominant vortex structures of the control valve. To this end, the typical annular attachment flow inside a steam turbine control valve was investigated by carrying out a detached eddy simulation (DES). Thereafter, the energetic pressure fluctuation modes were determined by conducting POD analysis on the pressure field of the valve. The vortex structures contributing to the energetic pressure fluctuation modes were determined by conducting extended-POD analysis on the pressure–velocity coupling field. Finally, the dominant vortex structures were revealed conducting a direct POD analysis of the velocity field. The results revealed that the flow instabilities inside the control valve were mainly induced by oscillations of the annular wall-attached jet and the derivative flow separations and reattachments. Moreover, the POD analysis of the pressure field revealed that most of the pressure fluctuation intensity comprised the axial, antisymmetric, and asymmetric pressure modes. By conducting extended-POD analysis, the incorporation of the vortex structures with the energetic pressure modes was observed to coincide with the synchronous, alternating, and single-sided oscillation behaviors of the annular attachment flow. However, based on the POD analysis of the unsteady velocity fields, the vortex structures, buried in the dominant modes at St = 0.017, were found to result from the alternating oscillation behaviors of the annular attachment flow.

Buffer Groove Design of Continuous Rotary Electro-Hydraulic Servo Motor Used in Simulator

2010 ◽  
Vol 37-38 ◽  
pp. 234-237
Author(s):  
Xiao Jing Wang ◽  
Jun Peng Shao ◽  
Guang Bin Yu
Keyword(s):  
Mathematical Model ◽  
Pressure Gradient ◽  
Experimental Research ◽  
Pressure Field ◽  
Structure Design ◽  
Cavity Pressure ◽  
Servo Motor ◽  
Pressure Impact ◽  
Hydraulic Servo ◽  
The Mathematical Model

In order to improve the low speed stationary of continuous rotary electro-hydraulic servo motor and avoid the pressure impact in the sealed cavity during the oil distributing, this paper designed the shape of buffer groove, established the mathematical model of pressure gradient, and analyzed change law of sealed cavity pressure gradient under different dimension of buffer groove. The pressure field distribution of sealed cavity was studied in certain radial and axial gap, and it is validated the dimension of buffer groove is rational, which lays foundation for structure design and experimental research of large displacement servo motor.

OSCILLATION DAMPER CALCULATION BASED ON THE ELECTRO HYDRAULIC ANALOGY

2020 ◽  
pp. 17-24
Author(s):  
S. V. Britsyn ◽  
M. V. Ryabinin ◽  
S. E. Semenov
Keyword(s):  
Mathematical Model ◽  
Pressure Fluctuations ◽  
Pressure Pulsations ◽  
Plunger Pump ◽  
Outlet Pressure ◽  
Unsteady Fluid Flow ◽  
Flow Through ◽  
Unsteady Fluid ◽  
Hydraulic Analogy ◽  
The Mathematical Model

The method of the synthesis and the pressure fluctuations damping calculation based on the electro-hydraulic analogy is proposed. The mathematical model describing the processes of unsteady fluid flow through the device is developed. Using the composed transfer function and its approximation, the oscillation damper parameters identification to reduce the outlet pressure pulsations in the triplex plunger pump is carried out.

An Experimental Study of the Flow and Wall Pressure Field Around a Wing-Body Junction

1986 ◽  
Vol 108 (3) ◽  
pp. 308-314 ◽  
Author(s):  
M. A. Z. Hasan ◽  
M. J. Casarella ◽  
E. P. Rood
Keyword(s):  
Pressure Gradient ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Low Frequency ◽  
Adverse Pressure Gradient ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Frequency Content ◽  
Wall Pressure Fluctuations

The flow and wall-pressure field around a wing-body junction has been experimentally investigated in a quiet, low-turbulence wind tunnel. Measurements were made along the centerline in front of the wing and along several spanwise locations. The flow field data indicated that the strong adverse pressure gradient on the upstream centerline causes three-dimensional flow separation at approximately one wing thickness upstream and this induced the formation of the horseshoe root vortex which wrapped around the wing and became deeply embedded within the boundary layer. The wall-pressure fluctuations were measured for their spectral content and the data indicate that the effect of the adverse pressure gradient is to increase the low-frequency content of the wall pressure and to decrease the high-frequency content. The wall pressure data in the separated region, which is dominated by the horseshoe vortex, shows a significant increase in the low-frequency content and this characteristic feature prevails around the corner of the wing. The outer edge of the horseshoe vortex is clearly identified by the locus of maximum values of RMS wall pressure.

Turbulent Pressure-Velocity Measurements in a Fully Developed Concentric Annular Air Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 345-354 ◽  
Author(s):  
R. J. Wilson ◽  
B. G. Jones
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Core Region ◽  
Flow Channel ◽  
Wall Pressure ◽  
Analysis Method ◽  
Local Pressure ◽  
Wall Pressure Fluctuations

An experimental study of the fluctuating velocity field and the fluctuating static wall pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field and fluctuating static wall pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained. The effect of the turbulent core region of the flow on the wall pressure fluctuations was studied by cross-correlating the axial and radial velocity components with the wall pressure fluctuations. A three-sensor, signal subtraction data analysis method using coherence techniques was developed to separate the superimposed local pressure fluctuations and acoustically transmitted noise. This analysis method is shown to adequately isolate the local pressure fluctuation information at each wall of the flow channel. The results of the experimental measurements are compared with existing experimental and numerical information on turbulent annular flow fields and wall pressure statistics. The pressure-velocity correlation indicates that a substantial contribution to the pressure field on the wall of the flow channel is from the turbulent core region outside of the boundary layer. The wall pressure field is shown to be significantly different on the two dissimilar walls. The pressure-velocity correlations show that this difference is due to the geometric difference between the dissimilar volumetric sources which contribute to the wall pressure field. The results of this study show that vibration modeling must incorporate the effects of the flow geometry on the wall pressure statistics, which are used as the driving force for flow-induced vibrations.

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