Deterioration in Strength of Brittle-State Porous Bodies

1965 ◽  
Vol 32 (1) ◽  
pp. 43-46 ◽  
Author(s):  
P. C. Huang
Keyword(s):  
Porous Medium ◽  
Porous Material ◽  
Residual Strength ◽  
Modulus Of Elasticity ◽  
Room Temperature ◽  
Density Ratio ◽  
Material Function ◽  
Porous Bodies ◽  
Degradation Factor ◽  
Brittle State

A theory is presented to predict the deterioration in strength for a structure composed of a brittle-state porous material which has been subjected to a damaging tension field. Based on the theory, a degradation factor can be formulated as a means of evaluating the residual strength numerically. A proposed material function for a brittle-state porous medium was evaluated experimentally and was found to be satisfactory for an alumina material. The modulus of elasticity at room temperature of the same material has been found to increase with the density ratio in semi-logarithmic form.

Catalytic activity of CuGHK peptide-based porous material

2021 ◽  
Author(s):  
Francisco G. Cirujano ◽  
Nuria Martin ◽  
Neyvis Almora-Barrios ◽  
Carlos Martí-Gastaldo
Keyword(s):  
Catalytic Activity ◽  
Porous Material ◽  
Active Sites ◽  
Room Temperature ◽  
Side Chain ◽  
Periodic Distribution ◽  
Lysine Side Chain ◽  
One Step

Room temperature one-step synthesis of the peptide-based porous material with a periodic distribution of pockets decorated with lysine side chain active sites behaves as a heterogeneous organocatalyst. The pockets are...

Equation of State’s Crossover Enhancement of Pseudopotential Lattice Boltzmann Modeling of CO2 Flow in Homogeneous Porous Media

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 434
Author(s):  
Assetbek Ashirbekov ◽  
Bagdagul Kabdenova ◽  
Ernesto Monaco ◽  
Luis R. Rojas-Solórzano
Keyword(s):  
Porous Medium ◽  
Lattice Boltzmann ◽  
Multiphase Flows ◽  
Equations Of State ◽  
Density Ratio ◽  
Narrow Channel ◽  
Lattice Boltzmann Model ◽  
High Density Ratio ◽  
Homogeneous Porous Medium ◽  
Density Ratios

The original Shan-Chen’s pseudopotential Lattice Boltzmann Model (LBM) has continuously evolved during the past two decades. However, despite its capability to simulate multiphase flows, the model still faces challenges when applied to multicomponent-multiphase flows in complex geometries with a moderately high-density ratio. Furthermore, classical cubic equations of state usually incorporated into the model cannot accurately predict fluid thermodynamics in the near-critical region. This paper addresses these issues by incorporating a crossover Peng–Robinson equation of state into LBM and further improving the model to consider the density and the critical temperature differences between the CO2 and water during the injection of the CO2 in a water-saturated 2D homogeneous porous medium. The numerical model is first validated by analyzing the supercritical CO2 penetration into a single narrow channel initially filled with H2O, depicting the fundamental role of the driving pressure gradient to overcome the capillary resistance in near one and higher density ratios. Significant differences are observed by extending the model to the injection of CO2 into a 2D homogeneous porous medium when using a flat versus a curved inlet velocity profile.

Investigation of the Effect of Porous Material on the Flow and Temperature Patterns of a Passive Solar Air Heater

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Digpal Kumar ◽  
B. Premachandran
Keyword(s):  
Heat Flux ◽  
Porous Medium ◽  
Porous Material ◽  
Constant Heat Flux ◽  
Surface Radiation ◽  
Electrical Heating ◽  
Solar Air Heater ◽  
Air Heater ◽  
The Difference ◽  
Drying Chamber

Abstract In this work, the effect of flow resistance due to the presence of porous medium representing agricultural products at the exit of free convection-based solar air heater is studied experimentally and numerically. An air heater, along with the drying chamber, is designed as an inclined channel to conduct the experiments. Constant heat flux condition is provided by electrical heating on the top absorber plate of the channel. Experiments are conducted for heat flux ranging from 250 to 750 W/m2 for the channel inclination angle of 30 deg. Porous material bed height is also varied in the drying chamber, while porosity is set at 0.36. The surface-to-surface radiation model is considered for modeling of heat transfer within the flow. For all the heat flux values considered in the experiments, numerical simulations are performed at three different angles of inclinations of 15 deg, 30 deg, and 45 deg. In this analysis, the temperature distribution in the channel wall, the flow pattern, the difference in the mass flowrate, and temperature of the outlet air are investigated with different heights of the porous medium.

The stability of a viscous liquid in a vertical tube containing porous material

1959 ◽  
Vol 252 (1268) ◽  
pp. 120-134 ◽  
Keyword(s):  
Porous Medium ◽  
Porous Material ◽  
Density Gradient ◽  
Capillary Tube ◽  
Saturated Porous Medium ◽  
Vertical Tube ◽  
Neutral Stability ◽  
Molecular Diffusivity ◽  
Dimensionless Ratio ◽  
The Stability

If a long vertical tube filled with porous material contains a viscous solution, the density of which increases with height as a result of the presence of the dissolved substance, the equilibrium of the liquid is stable provided that the density gradient does not anywhere exceed the value d ρ /d Z = 3·390 μκ / gkb 2 Here κ , the diffusivity of the solute through the saturated porous medium, is defined to be the quantity of solute diffusing across unit area within the porous medium per unit time under unit density gradient. The above expression for the density gradient at neutral stability has been compared experimentally with Taylor’s value for the corresponding density gradient in a vertical capillary tube. For a porous medium consisting of randomly packed glass spheres of mean diameter about 0·2 mm and porosity ϵ = 0·365, it has been found that the two results are consistent provided that the ratio κ / Dϵ = 0·633, where D is the molecular diffusivity of the solute when the porous medium is absent. As this dimensionless ratio is a property of the porous material alone, it can be determined directly by diffusion measurements. An alternative method of measuring κ / Dϵ , based upon an electrical analogue, has led to a value of 0·641 for the same porous material, which is in good numerical agreement.

Computational Fluid Dynamics Evaluations of Film Cooling Flow Scaling Between Engine and Experimental Conditions

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
James L. Rutledge ◽  
Marc D. Polanka ◽  
Nathan J. Greiner
Keyword(s):  
Low Temperature ◽  
Film Cooling ◽  
Momentum Flux ◽  
Room Temperature ◽  
Density Ratio ◽  
Flux Ratio ◽  
Experimental Conditions ◽  
Cold Air ◽  
Momentum Flux Ratio ◽  
Adiabatic Effectiveness

The hostile turbine environment requires testing film cooling designs in wind tunnels that allow for appropriate instrumentation and optical access, but at temperatures much lower than in the hot section of an engine. Low-temperature experimental techniques may involve methods to elevate the coolant to freestream density ratio to match or approximately match engine conditions. These methods include the use of CO2 or cold air for the coolant while room temperature air is used for the freestream. However, the density is not the only fluid property to differ between typical wind tunnel experiments so uncertainty remains regarding which of these methods best provide scaled film cooling performance. Furthermore, matching of both the freestream and coolant Reynolds numbers is generally impossible when either mass flux ratio or momentum flux ratio is matched. A computational simulation of a film cooled leading edge geometry at high-temperature engine conditions was conducted to establish a baseline condition to be matched at simulated low-temperature experimental conditions with a 10× scale model. Matching was performed with three common coolants used in low-temperature film cooling experiments—room temperature air, CO2, and cold air. Results indicate that matched momentum flux ratio is the most appropriate for approximating adiabatic effectiveness for the case of room temperature air coolant, but matching the density ratio through either CO2 or cold coolant also has utility. Cold air was particularly beneficial, surpassing the ability of CO2 to match adiabatic effectiveness at the engine condition, even when CO2 perfectly matches the density ratio.

Thermal Shock Behavior of Nd-Doped α-Sialon Ceramics

2010 ◽  
Vol 434-435 ◽  
pp. 130-133 ◽  
Author(s):  
Chun Feng Liu ◽  
Feng Ye ◽  
Yu Zhou ◽  
Yu Dong Huang ◽  
Jian Min Zhou
Keyword(s):  
Thermal Shock ◽  
Residual Strength ◽  
Room Temperature ◽  
Stoichiometric Composition ◽  
Surface Oxidation ◽  
Cycle Times ◽  
Time Cycle ◽  
Thermal Shock Behavior ◽  
Hot Press Sintering ◽  
Room Temperature Strength

Nd--sialons with the stoichiometric composition of Nd0.333Si10Al¬2ON15 were obtained by hot-press sintering at 1800°C for 1h. The thermal shock behavior of the Nd--sialons was examined by a water-quenching technique. The influence of the thermal shock temperature difference (T) and cycle times on the residual strength was evaluated. Equiaxed -sialon grains formed together with a small amount of intergranular phase M (Nd2Si3-xAl¬xO3+xN4-x) and -sialon phase. The residual strength after a thermal shock tended to decrease gradually with increasing T above 500°C. However, the specimens exhibited an improved residual strength (~94% of the room temperature strength) after a thermal shock of T=1100°C. The residual strength presented a gradual decrease with increasing the thermal shock cycle times at T=1100°C, and was still remained ~55% of the room temperature strength after 11-time cycle. It is contributed to the surface oxidation which may results in the healing of surface cracks and the generation of surface compressive stresses.

scholarly journals Nonlinear sorptive effects during the pumping of a nanofluid through porous medium

2020 ◽  
pp. 9-16
Author(s):  
V. A. Demin ◽  
◽  
B. S. Maryshev ◽  
A. I. Menshikov ◽  
◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
Porous Material ◽  
Direct Numerical Simulation ◽  
Critical Velocity ◽  
Mathematical Description ◽  
Particle Separation ◽  
Reverse Reaction ◽  
Sorption Properties ◽  
Filtration Process

Filtration process of a nanofluid with particles size less than 100 nm through a porous medium is analyzed theoretically on the base of direct numerical simulation. Mathematical description of this process is fulfilled using the MIM model and Darcy's law, which are modified to take into account the nonlinear reverse reaction of sorption properties of the material on the intensity of pore velocity. A new parameter, which characterizes this nonlinearity, is introduced into the model. In fact, it represents the value of critical velocity for particle separation from the pore walls by the flow. The values of permeability and porosity decrease in dependence on time during the saturation of porous medium with nanoparticles. These parameters are related with each other by the Kozeny–Carman equation. The results of calculations show that the variation of the critical velocity for particle separation significantly affects on the dynamics of redistribution of the mobile and immobile impurity in porous material.

scholarly journals An Eigenvalues Approach for a Two-Dimensional Porous Medium Based Upon Weak, Normal and Strong Thermal Conductivities

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 848
Author(s):  
Faris Alzahrani ◽  
Aatef Hobiny ◽  
Ibrahim Abbas ◽  
Marin Marin
Keyword(s):  
Porous Medium ◽  
Porous Material ◽  
Volume Fraction ◽  
Numerical Results ◽  
Two Dimensional ◽  
Temperature Stresses ◽  
Symmetric Geometry ◽  
Thermal Conductivities

This work is devoted to the investigation of a two-dimensional porous material under weak, strong and normal conductivity, using the eigenvalues method. By using Laplace–Fourier transformations with the eigenvalues technique, the variables are analytically obtained. The derived technique is assessed with numerical results that are obtained from the porous mediums using simplified symmetric geometry. The results, including the displacements, temperature, stresses and the change in the volume fraction field, are offered graphically. Comparisons are made among the outcomes obtained under weak, normal and strong conductivity.

Structural Stiffness of X-750 Alloy Bump Foil Strips for Compliant Foil Bearings With Different Heat Treatments

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Wenbo Duan ◽  
Yanhua Sun ◽  
Chunhua Ding ◽  
Lie Yu
Keyword(s):  
Heat Treatment ◽  
Dynamic Load ◽  
Modulus Of Elasticity ◽  
Room Temperature ◽  
Load Capacity ◽  
Great Influence ◽  
Heat Treatments ◽  
Structural Stiffness ◽  
Foil Bearings ◽  
Load Tests

This paper focuses on the structural stiffness of bump foils which are used for compliant foil bearings with different heat treatments. After heat treatments in vacuum environments, the mechanical properties of the foil strips were tested, and the structural stiffness was estimated from the static load versus displacement curves obtained from the experiments. High cycle dynamic load tests were also applied to the bump foil under different cycle loads, and the shape of the foil was scanned after the tests to measure the height variation of the bumps. The results show that the modulus of elasticity and strength of Inconel X-750 strip with thickness of 0.1 mm after different treatments are lower than that with the thickness of 0.18 mm at room temperature. Moreover, the sample foil strips which have been treated with a lower solution anneal temperature at 980 °C (2 hrs) and precipitation heat treatment at 732 °C (16 hrs) have the largest modulus of elasticity and strength at room temperature. Therefore, heat treatments have a great influence on the structure stiffness of the bump foil. At last, the results of the high cycle dynamic load tests show that the bump foil with suitable heat treatment will have a good load capacity and stress-relaxation property.

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