An Experimental Study on the Influence of Structural Damping on Internal Fluid Pressure During a Transient Flow

1990 ◽  
Vol 112 (3) ◽  
pp. 284-290 ◽  
Author(s):  
D. D. Budny ◽  
F. J. Hatfield ◽  
D. C. Wiggert
Keyword(s):  
Experimental Study ◽  
Transient Flow ◽  
Traditional Approach ◽  
Dynamic Pressure ◽  
Fluid Pressure ◽  
Piping System ◽  
Internal Dynamic ◽  
Structural Damping ◽  
Pipe System ◽  
Internal Fluid

The traditional approach to designing a piping system subject to internal dynamic pressure is to restrain the piping as much as possible, and the approximation made in the analysis is to assume no contribution of structural energy dissipation. To determine the validity of this concept and approximation, an experimental study of a piping system was performed to measure the influence of structural damping. A pipe system was designed with a loop that could be turned so that its natural frequency would match that of the contained liquid. It was discovered that a properly sized damper on the piping loop greatly accelerates the decay of the fluid pressure transient. The damper absorbs some energy from the piping, reducing the resulting rebound fluid pressure. When the loop is subjected to forced steady-state vibration, there is a fluid pressure response. The amplitude of that pressure can be reduced by installing an external damper: the stiffer the damper the more effective it is in reducing dynamic pressure.

Transient Pressure Analysis in Piping Networks due to Valve Closing and Outlet Pressure Pulsation

1996 ◽  
Vol 118 (3) ◽  
pp. 315-325 ◽  
Author(s):  
F. K. Choy ◽  
M. J. Braun ◽  
H. S. Wang
Keyword(s):  
Pressure Pulsation ◽  
Transient Flow ◽  
Fluid Pressure ◽  
Piping System ◽  
Transient Pressure ◽  
Closing Time ◽  
Frequency Domains ◽  
Transient Pressure Analysis ◽  
Parametric Studies ◽  
Piping Networks

This paper investigates the transient flow and pressure developments in a piping network due to design parametric and operational variations. Numerical simulations using both the method of characteristics and the finite difference formulation are performed and compared. The transient fluid pressure pulsations in the pipes are examined in both the time and frequency domains using a Fast Fourier Transform (FFT) algorithm. The parametric studies consider changes in i) the main pipe size, ii) the valve closing time at the branch outlet, iii) the piping system configuration (both single and multiple branched systems), and iv) the frequency of pressure pulsation at the branch outlet (manifold effect). The paper discusses the sensitivity of the transient fluid pressure and the excitability of the piping natural frequencies at various locations of the pipes, due to valve closing and manifold effects at the branch outlet. The effects of resonance due to pressurefrequency variation at the branch outlet are also studied and general conclusions are drawn from these results.

Vascular Fluid Damping of Flexible Multifunctional Composite Cantilevers: Experiment, Modeling and Analysis

2014 ◽  
Author(s):  
Matthias Gaucher-Petitdemange ◽  
Ya Wang ◽  
Masoud Masoumi ◽  
Daniel J. Inman
Keyword(s):  
Experimental Study ◽  
Fluid Flows ◽  
Structural Damping ◽  
Multifunctional Composites ◽  
Modeling And Analysis ◽  
Internal Fluid ◽  
Fluid Damping ◽  
Flow Through ◽  
Vascular Channels ◽  
Damping Treatments

Passive structural damping treatments based on viscoelastic polymers of elastomers are widely used in practice and have been the focus of numerous research studies and papers. Here we examine a multifunctional structure with vascular channels and investigate how the fluid in the channels provides damping to the system. While the vibration and stability of flow through a pipe has been extensively examined, internal fluid induced passive damping has not been well investigated in literature. Motivated by research in using vascular channels to provide self-cooling and autonomous healing of multifunctional composites, here we investigate the material and mechanical parameter dependence effects of internal fluid damping using an experimental study, modeling and numerical analysis of the dynamics of flexible cantilever beam conveying three types of internal vascular fluid flows.

The Influence of Structural Damping on Internal Pressure During a Transient Pipe Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 424-429 ◽  
Author(s):  
Dan D. Budny ◽  
D. C. Wiggert ◽  
F. J. Hatfield
Keyword(s):  
Fluid Pressure ◽  
Equation Model ◽  
Piping System ◽  
Viscous Damping ◽  
Structural Damping ◽  
Equivalent Viscous Damping ◽  
Transient Event ◽  
Frequency Components ◽  
Transient Pipe Flow ◽  
Poisson Coupling

A four equation model of axial wave propagation with Poisson coupling which includes viscous damping to account for structural energy dissipation is evaluated. Comparison of the predictions with experimental data indicates that the model can satisfactorily predict fluid pressure and structural velocity. The results show that structural damping reduces the pressure peaks during a transient event by eliminating the high frequency components. For the conditions studied, this reduction was 20 to 25 percent for a piping system with no axial constraints. A saddle-type support increases the equivalent viscous damping, and this increased damping can be modeled as either distributed damping or as an external damper.

Performance Analysis of Thin Shell Bends under High Pressure and Temperature

2015 ◽  
Vol 787 ◽  
pp. 296-300
Author(s):  
P. Govindaraj ◽  
Mouleeswaran Senthilkumar
Keyword(s):  
High Stress ◽  
Fluid Pressure ◽  
Bending Moment ◽  
Piping System ◽  
High Stress Concentration ◽  
Geometrical Imperfection ◽  
Internal Fluid ◽  
Piping Systems ◽  
The Cost ◽  
Work Effect

Around 70% of the cost in piping industry is spent in the pipe manufacturing with optimum design of pipes without defects. Research on design of pipes has gained importance from the last decade. There are numerous methods being developed to improve the efficiency of piping units considering various parameters. The pipe tends to flatten when they are forced to bend, this geometrical changes has a significant role in the acceptability criteria of pipes. It is necessary to bend pipes in order to transmit liquid or gas from one place to other place. In this work special attention is given to pipe bends because of high stress concentration due to various loading conditions. From several kinds of piping systems, process piping systems are chosen for analysis since pipes used here transport important and hazardous materials. Damage to such piping system can cause serious loss to economy and human lives. The geometrical imperfection associated with bending of pipes is ovality. This degree of ovality determines the acceptance of pipes. Thickening and thinning effects cause additional problems like large plastic deformation and loss of flexibility respectively. Hence estimation of the best degree of ovality is required. In this work effect of ovality is estimated by taking the internal fluid pressure and In plane bending moment into account.

scholarly journals Simulation Model of Bottom Hole Dynamic Pressure and Reservoir Dynamic Stress in Hydraulic Fracturing with Pulse Injection

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Ge Zhu ◽  
Shimin Dong
Keyword(s):  
Hydraulic Fracturing ◽  
Pressure Wave ◽  
Dynamic Stress ◽  
Transient Flow ◽  
Dynamic Pressure ◽  
Fluid Pressure ◽  
Injection Pressure ◽  
Pulse Injection ◽  
Bottom Hole ◽  
Injection Scheme

To study the mechanism of hydraulic fracturing with pulse injection theoretically, in this paper, the transient flow model of fracturing fluid in the pipe string was established, and it was solved by method of characteristics and finite difference method, respectively. Furthermore, the elastodynamic model of reservoir was also established. Based on the finite element method, the dynamic stress distribution in the reservoir was simulated and calculated. In addition, the influence of parameters in the pulse injection scheme on dynamic stress was analyzed. The results indicate that the unsteady injection produces a pulse pressure wave at the wellhead. The pressure wave propagates along the pipe string to the bottom of the well, and its amplitude attenuates due to the resistance loss. When the pressure wave propagates to the bottom of the well, it will be reflected and there is a superposition area of the downward pressure wave and upward reflection wave near the bottom hole. The bottom hole pressure of pulse injection is the sum of stable injection pressure and the above pressure wave. Simultaneously, this fluid pressure with pulse variation will stimulate reservoir to produce dynamic stress in its interior. The pulse adjustment time and adjustment amplitude in the injection scheme have a significant impact on the dynamic stress. The results of this paper are helpful to understand the mechanism of hydraulic fracturing with pulse fluid injection and provide guidance for its parameter design.

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

In-Plane Parametric Vibrations of Curved Bellows Subjected to Oscillating Internal Fluid Pressure Excitation

2004 ◽  
Author(s):  
Masahiro Watanabe ◽  
Eiji Tachibana ◽  
Nobuyuki Kobayashi
Keyword(s):  
Stability Analysis ◽  
Natural Frequencies ◽  
Parametric Instability ◽  
Fluid Pressure ◽  
Parametric Vibrations ◽  
Internal Fluid ◽  
Mathieu’S Equation ◽  
Stability Maps ◽  
Plane Direction ◽  
Pressure Excitation

This paper deals with the theoretical stability analysis of in-plane parametric vibrations of a curved bellows subjected to periodic internal fluid pressure excitation. The curved bellows studied in this paper are fixed at both ends rigidly, and are excited by the periodic internal fluid pressure. In the theoretical stability analysis, the governing equation of the curved bellows subjected to periodic internal fluid pressure excitation is derived as a Mathieu’s equation by using finite element method (FEM). Natural frequencies of the curved bellows are examined and stability maps are presented for in-plane parametric instability. It is found that the natural frequencies of the curved bellows decrease with increasing the static internal fluid pressure and buckling occurs due to high internal fluid pressure. It is also found that two types of parametric vibrations, longitudinal and transverse vibrations, occur to the curved bellows in-plane direction due to the periodic internal fluid pressure excitation. Moreover, effects of axis curvature on the parametric instability regions are examined theoretically.

scholarly journals Tactile Perception for Teleoperated Robotic Exploration within Granular Media

2021 ◽  
Vol 10 (4) ◽  
pp. 1-27
Author(s):  
Shengxin Jia ◽  
Veronica J. Santos
Keyword(s):  
Granular Media ◽  
Fluid Pressure ◽  
Tactile Sensor ◽  
Tactile Perception ◽  
Test Accuracy ◽  
Contact State ◽  
Buried Objects ◽  
Media Type ◽  
Additional Information ◽  
Internal Fluid

The sense of touch is essential for locating buried objects when vision-based approaches are limited. We present an approach for tactile perception when sensorized robot fingertips are used to directly interact with granular media particles in teleoperated systems. We evaluate the effects of linear and nonlinear classifier model architectures and three tactile sensor modalities (vibration, internal fluid pressure, fingerpad deformation) on the accuracy of estimates of fingertip contact state. We propose an architecture called the Sparse-Fusion Recurrent Neural Network (SF-RNN) in which sparse features are autonomously extracted prior to fusing multimodal tactile data in a fully connected RNN input layer. The multimodal SF-RNN model achieved 98.7% test accuracy and was robust to modest variations in granular media type and particle size, fingertip orientation, fingertip speed, and object location. Fingerpad deformation was the most informative modality for haptic exploration within granular media while vibration and internal fluid pressure provided additional information with appropriate signal processing. We introduce a real-time visualization of tactile percepts for remote exploration by constructing a belief map that combines probabilistic contact state estimates and fingertip location. The belief map visualizes the probability of an object being buried in the search region and could be used for planning.

Buckling of Risers in Tension due to Internal Pressure: Nonmovable Boundaries

1983 ◽  
Vol 105 (3) ◽  
pp. 277-281 ◽  
Author(s):  
M. M. Bernitsas ◽  
T. Kokkinis
Keyword(s):  
Internal Pressure ◽  
Fluid Pressure ◽  
Critical Length ◽  
Entire Length ◽  
Tubular Columns ◽  
Internal Fluid ◽  
Static Instability

Open-ended tubular columns may buckle globally as Euler columns due to the action of internal fluid pressure even while they are in tension along their entire length. Hydraulic columns, marine drilling and production risers are, therefore, prone to such static instability. This paper explains this phenomenon, defines the critical riser length for which this instability may occur and provides graphs with values of the critical length which can readily be used for design purposes. Risers with nonmovable boundaries are considered; namely, hinged-hinged, clamped-hinged, hinged-clamped and clamped-clamped risers.

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