Transient Internal Pressure Research Articles

Highly-Efficient Graphene Pressure Sensor with Hierarchical Alarm for Detecting the Transient Internal Pressure of Transformer Bushing

Highly-Efficient Graphene Pressure Sensor with Hierarchical Alarm for Detecting the Transient Internal Pressure of Transformer Bushing

Highly-Efficient Graphene Pressure Sensor with Hierarchical Alarm for Detecting the Transient Internal Pressure of Transformer Bushing

Highly-Efficient Graphene Pressure Sensor with Hierarchical Alarm for Detecting the Transient Internal Pressure of Transformer Bushing

Experimental and theoretical study on the internal pressure induced by the transient local failure of low-rise building roofs

A case study on the internal pressure induced by a local failure on the vulnerable gable roof of a low-rise building was extensively conducted experimentally and numerically. Five roof opening configurations were tested in the wind tunnel under three different boundary layer conditions, based on 1:40 scaled models. The effects of opening shape, opening position, opening ratio, building internal volume, and wind speed on peak transient and steady-state internal pressures were studied. The study results indicate that the peak transient and steady-state internal pressures and the corresponding transient overshoot ratio all increase with an increasing opening ratio. The peak steady-state internal pressure is little affected by the approaching wind speed; while the peak transient internal pressure coefficient shows a significant linear relationship with the wind speed. The coupling effect of vortex shedding and Helmholtz resonance in double building volume compensation situation may cause larger fluctuating internal pressure. Both the vortex shedding and Helmholtz resonance reduce the internal pressure coherence to some extent. The agreement between the numerical and experimental results is much better for the mean internal pressure than that for fluctuating internal pressure or peak internal pressure.

Steady-state and transient wind characteristics of low-rise building roofs with openings in vulnerable areas

A strong wind would cause roof openings on a low-rise building and bring further structural damage. Previous related studies focused on different shapes of openings on flat roofs. Little study has been done on the sloped roofs with openings in vulnerable roof areas. In this study, wind tunnel tests were carried out to investigate the steady-state and transient internal pressure characteristics due to opening at the vulnerable roof areas of a low-rise building. The tests considered both steady-state and transient openings of roof. The experimental results indicated that the steady-state internal pressure distribution tends to be uniform and that the internal pressure induced by leeward roof ridge opening is obviously lower than that induced by the windward one. The fluctuation effect around the orifice area is apparent with the skewed wind direction and the combined effect of internal and external pressures on the unopened roof side is significantly smaller than that on the opened side. Current design provision of China for internal pressure evaluation is found to be unconservative. The transient overshoot is closely related to the opening location in the vulnerable roof area and is more pronounced when the opening is on the leeward side. Among the internal pressure coefficients commonly adopted in design, the extreme net wind pressure coefficient is most important, which is affected most at the orifice near eaves, roof corners and tails, and leeward roof ridge.

Terrain uplift due to natural hydrologic overpressure in karstic conduits

Water supply from karst sources is a worldwide natural resource and the exploitation is tied to the knowledge of the positions of the hydrologic channels. We show that surface deformation induced by flood events in karst conduits is observable, and consists in uplift and outward movement from the hydraulic channel. Precipitation events produce the natural occurrence of subsurface hydraulic overpressure up to 1 MPa. Numerical modeling shows that the stresses are so strong to uplift and dislocate the surface by several mm and induce tilts in the order of microradians. The naturally induced deformation is compatible with a transient internal pressure loading of a channel. The results can be used to find new channels with dense GNSS networks. Sea water incursion and channels accessed for tourism could be monitored. Seismicity has been shown to have a seasonal variation in some areas, which could be explained by the subsurface stresses induced by the natural subsurface overpressure. The pressure induced deformation is expected to be observed in all karstic systems worldwide.

Flow transportation inside shale rocks at low-temperature combustion condition: A simple scaling law

The gas flow inside the shale undergoes a complicated process from continuum-flow to Knudsen diffusion during combustion. In this study, a shale sample obtained from Shanxi province with burial depth of 643 m was combusted at a constant temperature to study the transient internal pressure variation. In the beginning, a cylinder-shaped shale was combusted above an electric heater at a constant temperature 450 °C. The transient internal pressures and surface temperatures of the shale sample were recorded every 15 s. With the thermal wave propagating from the electric heater to the top of shale, the shale surface temperature gradually increased. The pressure inside the sample was quickly built up because of the thermal cracking of kerogen. It reached a peak value of 12,000 Pa. Afterwards, the pressure gradually declined with the improvement of the permeability of the shale. By the observations during the experiment, a combustion model based on the scaling power law was used to simulate the transient internal pressure changes of a cylinder shaped shale sample during the combustion process. The simulated results showed a good agreement with experimental data. Based on the pressure variation data, it was found that not only the original trapped/storage gas (free state gas, adsorbed state gas, and dissolved state gas) but also the thermal cracking hydrocarbon gases produced from kerogen could be extracted from tight shale formation for gas recovery. Thus, combustion can further improve the production rate of gas from shale reservoirs.

Spatial aperiodic vibrations of the pipelines under transient internal pressure

The influence of the average value and amplitude of the transient internal pressure in the pipelines on the spatial vibrations of the latter has been assessed. The graphic dependences of the spatial vibrations, their phase patterns, Fourier spectra, and Poincare maps have been presented. The latter have been analyzed depending on the input parameters and time. Brief conclusions have been formulated.

Application of Inverse Method to Estimation of Gas Adsorption Isotherms

As a first step to analyze the inverse kinetic of adsorption, an inverse algorithm is developed to estimate equilibrium adsorption isotherm in a gas storage vessel by using the dynamic transient internal pressure. In the present study, no prior information is need for the functional form of the unknown isotherm equation to solve continuity equation. The conjugate gradient method is employed for optimization procedure. The incremental differential quadrature method as a computationally efficient and accurate numerical tool is applied to solve the corresponding direct, sensitivity and adjoint problems. The accuracy of the presented approach is examined by simulating the exact data of known model. Good accuracy of the obtained results validates the presented approach.

Numerical Analysis on Transient Internal Pressure Character of Sudden Opening Building Suffer Simple Harmonic Excitation

The theoretical solution of the transient response of the wind-induced internal pressure based on assuming the external pressure is simple harmonic excitation by the linear equation governing the dynamics of internal pressure was presented. The effect of orifice loss coefficient, opening angle, the opening ratio and background porosity factor (Pf) on the transient internal pressure character was analyzed. The result shows: the peak value of the transient internal pressure and the overshooting ratio decreases with the increase of the orifice loss coefficient; the opening angle decides the overshooting effect. The overshooting ratio increases with the opening ratio and presents a decreasing trend while Pf increases; the effect of these factors on steady internal pressure is relatively small.

Transient response of a metallic capsule to an internal pressure pulse

Response of a metallic capsule to a transient internal pressure is analyzed adopting two models. The first is a two-dimensional (2-D) model with finite extent in the plane of the capsule's cross-section and infinite length normal to that plane. The second is a three-dimensional (3-D) axisymmetric model consisting of a short thin cylinder capped by thin disks. In both models, transfer matrices relate state vectors of tractions and displacements at two segment boundaries. The time interval from pressure initiation to failure of its material measures the capsule's effectiveness as a confining boundary.

The Response of Pipes and Supports to Internal Pressure Loads Generated by Gaseous Detonations

Pipes with nominal diameters 300 mm constructed from GRP or medium density polyethylene (MDPE) have been subject to transient internal pressure loads, generated by ethylene-air detonations. Several GRP sections survived repeated tests, while an MDPE pipe failed in a catastrophic manner. Time resolved strain measurements of the wall responses were obtained and both pre-cursor axial and transverse hoop strains have been resolved. The responses of idealized pipe supports are also reported.

WTRLGD—A computer program for the transient analysis of waterlogged fuel rods under the RIA condition

A computer code WTRLGD has been developed to describe the transient internal pressure of a waterlogged fuel rod during power burst and also to predict the possibility of the rod failure in the mode of cladding rupture. The code predicts transient thermal behavior of the fuel rod on the basis of an assumption of axisymmetry, and thermal-hydraulic transients of the internal water on the basis of a homogeneous volume-junction model modified so as to involve the cladding deformation. Calculated transients of the rod pressure are in fairly good agreement with those measured in the NSRR experiments, simulating the fuel rod behavior under an RIA condition. The comparison between calculation and experiment verifies that the code is an effective tool for the prediction of the failure of a waterlogged fuel rod.