The Vibration Study of A Sandwich Conical Shell With A Saturated FGP Core

This paper is provided to analyze the free vibration of a sandwich truncated conical shell with a saturated functionally graded porous (FGP) core and two same homogenous isotropic face sheets. The mechanical behavior of the saturated FGP is assumed based on Biot’s theory, the shell is modeled via the first-order shear deformation theory (FSDT), and the governing equations and boundary conditions are derived utilizing Hamilton’s principle. Three different porosity distribution patterns are studied including one homogenous uniform distribution pattern and two non-homogenous symmetric ones. The porosity parameters in mentioned distribution patterns are regulated to make them the same in the shell’s mass. The equations of motion are solved exactly in the circumferential direction via proper sinusoidal and cosinusoidal functions, and a numerical solution is provided in the meridional direction utilizing the differential quadrature method (DQM). The precision of the model is approved and the influences of several parameters such as circumferential wave number, the thickness of the FGP core, porosity parameter, porosity distribution pattern, the compressibility of the pore fluid, and boundary conditions on the shell’s natural frequencies are investigated. It is shown that the highest natural frequencies usually can be achieved when the larger pores are located close to the shell’s middle surface and in each vibrational mode, there is a special value of the porosity parameter which leads to the lowest natural frequencies. It is deduced that in most cases, natural frequencies decrease by increasing the thickness of the FGP core. In addition, reducing the compressibility of the porefluid a small growth in the natural frequencies can be seen.

Porosity Distribution Simulation and Impure Inclusion Analysis of Porous Crystal Layer Formed via Polythermal Process

In this work, we investigated the porosity distribution and separation property of the porous crystal layer formed via the polythermal process. The proposed porosity distribution model, considering both the cooling profile and the crystal settling effect, provided simulative results that met the MRI analysis experimental results with suitable agreement. Significant porosity variation from the top to the bottom of the crystal layer (ϕ from 0.75 to 0.55 under rapid cooling profile) was detected. Meanwhile, the vertical supersaturation degree gradient induced by the fluid fluctuation could impact nucleation and crystal growth kinetic along with crystal particle settling. The resulting crystal layer possessed various impurity inclusion conditions. Under a moderate cooling profile (0.4 K·min−1), the volume fraction of closed pores against overall pores decreased from 0.75 to 0.36. The proposed model and experimental analysis approach were demonstrated to be helpful for porosity distribution simulation and impure inclusion analysis of layer crystallization.

The Effect of Ultrasonic Agitation on the Porosity Distribution in Apically Perforated Root Canals Filled with Different Bioceramic Materials and Techniques: A Micro-CT Assessment

The present study evaluated the effect of ultrasonic agitation on the porosity distribution of BioRoot RCS/single gutta-percha cone (BR/SC) and MTA Flow (MF) root canals fillings used as apical plugs in moderately curved and apically perforated roots. Eighty mesial root canals of mandibular first molars were enlarged up to ProTaper NEXT X5 rotary instrument 2 mm beyond the apical foramen, simulating apical perforations. Specimens were randomly divided into four experimental groups (20 canals per group) according to the material and technique used for root canal obturation: BR/SC, BR/SC with ultrasonic agitation (BR/SC-UA), MF and MF with ultrasonic agitation (MF-UA). The ultrasonic tip was passively inserted into the root canal after the injection of flowable cement and activated for 10 s. The specimens were scanned before and after obturation with a high-resolution micro-computed tomography scanner, and the porosity of the apical plugs was assessed. The differences between groups were analyzed using the Kruskal-Wallis and Mann-Whitney tests, with the significance level set at 5%. None of the obturation materials and techniques used in this study was able to provide a pore-free root canal filling in the apical 5 mm. Considerably higher percentages of open and closed pores were observed in the MF and MF-UA groups, with the highest porosity being in the MF-UA group (p < 0.05). No significant differences were observed between the BR/SC and BR/SC-UA groups, where the quantity of open and closed pores remained similar (p > 0.05).

DEM study of the angle of repose and porosity distribution of cylindrical particles with different lengths

Effect of the length of cylindrical particle on repose angle and porosity of a pile was numerically studied using discrete element method. The variation of repose angle and porosity with coefficient of sliding and rolling friction were also discussed. The results shown that compared with sphere particle, the bottom size of cylindrical pile is smaller, while the height of cylinder pile is larger and the heap is steeper. With the increase of the length of cylinder, the contour line of the pile becomes steep, and the angle of repose increases. The repose angle shows a positive correlation with coefficient of sliding and rolling friction. The porosity increases with the increase of the length of cylinders. The trends of porosity are basically consist with that of repose angle, and with increase of friction coefficient, the average porosity increases.

Optimizing Borehole Images to Predict Porosity in New Discovery Limestone Minahaki Formation Pia-001 Exploration Well Matindok Block Central Sulawesi

PIA-001 exploration well is located 4 km away from Donggi Gas Field, Central Sulawesi. The objective of the well is to unlock the hydrocarbon potential in Minahaki Formation. However, this is not an easy task to do. Minahaki Formation is mainly comprised of heterogeneous limestone facies, in which the primary and secondary porosity varies from facies to facies at different scales. Moreover, the diagenesis processes, such as dissolution and cementation alter each facies differently. These are the factors that introduce high uncertainty in the porosity distribution and estimation in Minahaki Formation. The conventional method to predict porosity utilizes conventional logs such as density, neutron and sonic log. However, this method is not suitable to be used in heterogeneous limestone. Its low vertical sampling rates relative to the porosity distribution, fails to predict accurately the porosity and productivity potential of these complex reservoirs. Hence, porosity needs to be generated using other type of data. The ideal data to tackle this complexity is by using electrical borehole image log which was logged within water based mud. This data is in high resolution and cover 360-degree view of borehole wall. On top of that, by using the newly developed carbonate textural and porosity estimation method, the porosity as well as the productivity potential can be accurately generated. This carbonate textural and porosity computation method has been performed in PIA-001 Well. It is observed that the secondary porosity in PIA-001 well comprises of vugs connected to fractures, vugs connected to bed boundary and connected vugs with some isolated vugs, with the total porosity ranges from 10-20%. Generally, this porosity trend shows good correlation with the porosity result from routine core analysis. Besides that, the porosity as well as the connectivity from this method is used to assist the DST interval selection. Based on this study, it can be concluded that electrical borehole image contributes to significant improvement in heterogeneous limestone porosity estimation. The porosity result also shows a good correlation with the porosity from routine core analysis and flow potential from DST Test. It is suggested to perform the same analysis to improve the success ratio in exploration well with the same reservoir challenges.