Plexiglas Model Research Articles

Experimental Study on the Horizontal Bearing Characteristic of a Strip-Walled Underground Diaphragm Wall

Researching and developing a new type of diaphragm wall foundation can solve the probl em that the traditional diaphragm wall structure may not meet the high standards of safety and stability of underground structures in some specific engineering environments. This paper focuses on the horizontal bearing characteristic of a new form of foundation, a strip-walled underground diaphragm wall, through a series of model tests. In the tests, nine plexiglass models with different section sizes, wall spacings and wall heights, as well as loading strategies (horizontal loads along and against the wall in the model), were conducted. The influence of the above factors on the horizontal bearing performance of the foundation and the soil resistance distribution around the wall was studied. The results show that when the horizontal load applied along the wall is greater than 50 N, the growth rate of total displacement at the top of the wall gradually decreases; when a horizontal load is applied against the wall, with a uniform change in wall height, the optimal wall spacing is 11 cm. When the same displacement occurs, the bearing performance of the model under the former loading strategy is generally 10% higher than that under the later loading strategy. In addition, the depth where the maximum bending moment along the wall occurred gradually moves downward with the increase in horizontal load, and the increase in wall spacing and wall height has a positive effect on the horizontal bearing characteristic. With the application of load, the maximum bending moment of the wall will gradually decrease along the depth. The increase in wall spacing and wall height can improve the overall flexural stiffness and horizontal bearing performance of the foundation. Lastly, the group wall effect coefficient, β, is put forward, and a simplified formula for calculating the horizontal bearing capacity of a strip wall foundation is proposed. In the formula, β is negatively correlated with the buried depth of the wall and positively correlated with the distance between the walls, and its coefficient is greater than 1.

Evaluation of the Stability of Open-Tray Impression Coping Using Two Different Impression Materials at Three Different Subgingival Implant Placement Depths.

Objective To evaluate and compare the stability of the open trayimpression coping within the set impression while attaching the lab analog when polyether (PE) heavy body and polyvinyl siloxane (PVS) putty impression materials were used and the implant platform was placed sub-gingivally at three different depths. Methods Two impression materials, PE and PVS, and custom-made plexiglass models with embedded single implants to simulate implant positioning depths of 0 mm, 2 mm, and 4 mm, sub-gingivally, were used in the study. Open tray impressions were made after attaching impression coping to theimplant embedded in themodel. Implant lab analog was attached to the impression coping in the set impression, and its stability was measured using a universal testing machine. Forty-two open tray impressions were madein six groups, with seven impressions in each group. Descriptive statistics such as mean and standard deviation were calculated. A comparison of the meanstability between the two impression materials at each depth was done using an independent t-test.Comparison of the mean stability between the three different subgingival implant depths in each material was done by one-way ANOVA with the Scheffe multiple comparison test (post-hoc analysis). The level of significance was set at p<0.05. Results The stability of the impression coping was measured as the force in Newtons required for the displacement of the analog attached to the impression coping embedded in the set impression. PEwith the embedded impression coping at a depth of 0 mm gave the highest mean stability value (4.37+/-0.41), and the least mean stability was offered by PVS with the embedded impression coping at 4 mm depth (1.88+/-0.37). When an independent t-test was done to compare the mean stability values of PE and PVS,there was a statistically significant difference at0 mm, 2 mm, and 4 mm. On doing one-way ANOVA to compare the mean stability between the different depth groups, there was a statistically significant difference between the three depth groups in PE and PVS. Scheffe multiple comparison tests (post-hoc analysis) revealed a statistically significant difference between 0 mm, 2 mm, and 4 mm subgingival depths of the impression coping placement in bothPE and PVS. Conclusion The accuracy of the master cast is an important determinant for the precise fit and long life of the final prosthesis. In the case of maxillary anterior implant placements where deep subgingival placement of the implant platform is needed for aesthetic and functional reasons, the impression material should be selected carefully to ensure the stability of the impression coping. Among the materials included in the present study, the PE impression material offered the maximum stability for impression coping compared to PVS.

Physical Experiments and Numerical Simulations of the Influence of Turbulence Inhibitors and the Position of Ladle Shroud on the Steel Flow in an Asymmetric Five-Strand Tundish

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative.

Modelling of Technological Parameters of Aluminium Melt Refining in the Ladle by Blowing of Inert Gas through the Rotating Impeller

The presented paper deals with the use of physical modelling to study the degassing process of aluminium melts in the refining ladle by blowing inert gas through a rotating impeller. For the purposes of physical modelling, a plexiglass model in a scale of 1:1 is used for the operating ladle. Part of the physical model is a hollow shaft used for gas supply that is equipped with an impeller and two baffles. The degassing process of aluminium melt by blowing of inert gas is simulated at physical modelling by a decrease of dissolved oxygen in the model liquid (water). This paper is aimed at the evaluation of laboratory experiments that were obtained by the method of physical modelling. Attention is focused on the assessment of relevant parameters for the degassing process—rotary impeller speeds, volume flow rate of inert gas, the distance of the impeller from the bottom of the refining ladle, and impeller variant. The preliminary results of physical modelling show that the optimal results of the refining process are achieved by using the F2A 190 impeller.

О ПРОВЕРКЕ ГИПОТЕЗЫ КОСИНУСНОГО РАСПРЕДЕЛЕНИЯ НАПРЯЖЕНИЙ В КОНТАКТЕ «ВАЛ-ОТВЕРСТИЕ»

One of the most common connection types in mechanical engineering and construction is the shaft-hole connection. The mechanical stresses caused by its loading are distributed in the contact zone of the loaded parts of the joint. In some cases, they can lead to destruction. Therefore, while designing, it is important to analyze the mechanical stresses in the contact zone. Traditionally, calculations assume that the contact stresses are distributed according to the cosine law. However, this is not entirely true, especially with diff erent shaft and hole diameters. The authors examined theoretical studies of the contact zone of the shaft and the hole (including the cases of diff erent diameters) and the stress distribution in the contact zone. Based on the studies, they performed numerical calculations in the APMWinMachine environment to determine the stresses in the volume of the shaft and the plate with a hole when loading the shaft-hole connection. The analyses were performed for the two-dimensional case by the fi nite element method in the APMStructure program. The results show that when the diameters in the connection are equal, the stress distribution is close to the cosine law. In this case, only one stress raiser occurs in the contact zone, which is located on the line of action of the loading force. However, if there is a slight discrepancy in the shaft and hole diameters, there are three stress raisers in which the connection may break – the central zone and two side zones. The angular distance between them can be determined based on the known theoretical formulas. The authors made an experiment with a plexiglass model, which qualitatively confi rmed the correctness of the analysis performed.

Internal flow dynamics of spill-return pressure-swirl atomizers

The sprays produced by spill-return pressure-swirl atomizers are strongly dependent on the nature of the internal fluid dynamics. Several spill-return atomizers were compared in terms of the spatial and temporal behaviour of the internal air-core, liquid sheet thickness and its perturbations. The only difference amongst the test configurations was the geometrical arrangement of the spill-line (SL) orifice through which the liquid was spilled away. The flow field inside the swirl chamber was examined using high-speed imaging with image post processing using an in-house Matlab code and three orthogonal velocity components acquired using Laser Doppler Anemometry. The dimensions of the production atomizers did not allow direct visualization of their internal flow, so a scaled, modular, transparent plexiglass model was used. Its flow characteristics were equivalent to the original atomizer. The refractive index of the atomizer body was matched to the test liquid using a solution of 1-Bromonaphthalene and kerosene fuel type JET A-1. The test conditions were derived from the original atomizer and were limited to inlet port Reynolds numbers, from 700 to 2000 and spill-to-feed ratios, SFR, from 0 to 0.75. An inviscid analysis, originally derived for Simplex atomizers, was modified and applied to the spill-return version. This approach allows a theoretical prediction of the discharge coefficient and air-core diameter dependent solely on SFR. An axially located SL orifice inhibits any internal air-core forming in the swirl chamber. Off-axial SL orifices generate and stabilize the air-core, which leads to the regular formation of a liquid sheet and a high-quality spray. Nevertheless, some configurations changed the breakup nature of the liquid sheet and consequently the spray quality. Moreover, the turn-down ratio of the liquid supply rate and spray stability depend on the distance of the SL orifices from the swirl chamber centreline. The flow energy losses increase with SFR. The outcomes from this analysis allow the optimization of the SL configuration for specific application and extend the classical inviscid analysis.

Slurry improvement by vacuum pre-loading in combination with electro-osmosis and with dynamic compaction method

Aiming at the problem of serious soil cracking during electro-osmosis stage in the treatment of dredged slurry by vacuum pre-loading in combination with electro-osmosis method, this study proposes a new vacuum pre-loading method in combination with electro-osmosis and with dynamic compaction to overcome these drawbacks. Meanwhile, different current ratios are used to characterise the different activation times of the dynamic compaction to achieve the optimal activation time. Five laboratory tests were performed on dredged slurry in self-made plexiglass model bucket, and the electric current, drainage of soil, soil surface settlement and vane shear strength, etc. in the reinforcement of dredged were monitored. The test results show that the combined action of the vacuum pre-loading, electro-osmosis, and dynamic compaction process enhances the circuit current, improves the efficiency of the electro-osmotic drainage, and thus promotes the drainage of the soil and ultimately yields a better reinforcement effect. Meanwhile, the dynamic compaction process effectively reduces the energy consumption in the process of vacuum pre-loading combined with electro-osmosis. In addition, the optimal effect owing to the dredged slurry can be evoked when the dynamic compaction is activated in the middle stage of the electro-osmosis process.

Experimental and Numerical Characterization of the Flow Field at the Core Entrance of a Water Model of a Heavy Liquid Metal–Cooled Reactor

The thermal-hydraulic challenges of a nuclear reactor are numerous and mastering them is crucial for the design and safety of new reactors. Numerical simulation through computational fluid dynamics (CFD) codes or system thermal-hydraulic codes can address a lot of the different questions, nevertheless the use of water modeling for the study of the thermal-hydraulic behavior of a new primary system and the validation of codes remains an extremely valuable tool. A water model of the pool-type PbBi-cooled MYRRHA reactor has been developed at the von Karman Institute in collaboration with SCK•CEN. It is a full plexiglass model at a geometrical scale 1/5 of MYRRHA. This transparent water model allows the application of optical measurement techniques like particle image velocimetry (PIV) for flow characterization. Local results of PIV measurements performed in the lower plenum at the entrance of the core are presented and compared with CFD results for nominal operating condition and a natural convection case simulating decay heat removal. Very good agreement has been found in the velocity field. The results also show the importance of the radial flow entering the core of the water model in natural convection.

Experimental investigation of accidental scenarios using a scale water model of a HLM reactor

The thermal-hydraulics challenges of a nuclear reactor are numerous and their investigation is crucial for the design and safety of new reactors. Numerical simulation through CFD codes or System thermal hydraulics codes can address a lot of the different challenges; nevertheless the use of water modeling for the study and validation of the thermal hydraulic behavior of a new primary system remains a valuable tool. A water model of the pool-type liquid metal-cooled MYRRHA reactor has been developed at the von Karman Institute in collaboration with SCK•CEN. It is a full Plexiglas model at a geometrical scale 1/5 of the design version 1.2 of MYRRHA. The scaling was performed by respecting as much as possible the Richardson, Euler, Reynolds and Péclet numbers’ similarity with MYRRHA. This transparent water model allows the application of optical measurement techniques for the flow characterization. Different transient tests relevant for MYRRHA have been defined by SCK•CEN. These test cases have been studied using the water model facility. They include the study of the transient thermal hydraulic behavior when switching from forced to Loss-of-Flow (LOF), the failure of a single pump, the failure of one of the four heat exchangers and the loss of coolant inventory (LOC). Results of phenomenological behavior are presented as well as the time–dependent variation of temperatures recorded with different arrays of thermocouples immersed inside the upper plenum.

Contact force with magnetic-guided catheter ablation.

Achieving adequate catheter tip-tissue contact is essential for delivering robust radiofrequency (RF) ablation lesions. We measured the contact force generated by a remote magnetic-guided catheter navigation system. A plexiglass model with an integrated scale was fashioned to mimic transvenous and retrograde access to sites in the right atrium and right and left ventricles. An 8 Fr RF ablation catheter was steered by remote magnetic guidance at fields of 0.08 and 0.10 T, with and without a long sheath positioned at the entrance of the chamber. Ten contact force readings were taken at each setting, with the scale recalibrated prior to each measurement. Generalized estimating equations were used to compare contact force measurements while adjusting for the non-independent data structure. A total of 240 contact force measurements were taken. Without a long sheath, contact forces with magnetic fields of 0.10 T (n = 60) and 0.08 T (n = 60) were similar (6.1 ± 1.4 g vs. 6.0 ± 1.3 g, P = 0.089). Contact forces were not significantly different with simulated transvenous (n = 80) and retrograde aortic (n = 40) approaches (6.2 ± 1.4 g vs. 5.7 ± 1.2 g, P = 0.132). The contact force increased substantially with a long sheath (P < 0.001) and was significantly higher with 0.10 T (n = 60) vs. 0.08 T (n = 60) fields (20.4 ± 0.6 g vs. 18.0 ± 0.5 g, P < 0.001). Magnetic fields of 0.08 and 0.10 T provide stable catheter contact forces, as reflected by the small variability between measurements. The average contact force is approximately 6 g without a sheath and increases to 20 g with a long sheath positioned at the entrance of the chamber of interest.

Experimental and numerical thermal-hydraulics investigation of a molten salt reactor concept core

Abstract In the paper measurement results of experimental modelling of a molten salt fast reactor concept will be presented and compared with three-dimensional computational fluid dynamics (CFD) simulation results. Purpose of this article is twofold, on one hand to introduce a geometry modification in order to avoid the disadvantages of the original geometry and discuss new measurement results. On the other hand to present an analysis in order to suggest a method of proper numerical modelling of the problem based on the comparison of calculation results and measurement data for the new, modified geometry. The investigated concept has a homogeneous cylindrical core without any internal structures. Previous measurements on the scaled and segmented plexiglas model of the concept core and simulation results have shown that this core geometry could be optimized for better thermal-hydraulics characteristics. In case of the original geometry strong undesired flow separation could develop, that could negatively affect the characteristics of the core from neutronics point of view as well. An internal flow distributor plate was designed and installed with the purpose of optimizing the flow field in the core by enhancing its uniformity. Particle image velocimetry (PIV) measurement results of the modified experimental model will be presented and compared to numerical simulation results with the purpose of CFD model validation.

An improved lance design for hot metal de-sulphurisation

Hot metal de-sulphurisation is a dip-lance process involving the pneumatic injection of fine-grained de-sulphurisation reagents into the molten metal. For maximum efficiency the particles must be dispersed in the ladle as widely as possible to increase the total interfacial area which is primarily controlled by the lance design. Seven different lance configurations were modelled and simulated to determine the most efficient design using physical and mathematical modelling approach. A 0.25 scale plexi-glass model of the 100 T hot metal ladle was fabricated for the study. Residence time and mixing time studies were carried out using the electrical conductivity measurement technique through stimulus response of injected saturated salt solution. Mathematical modelling approach using momentum balance was used to simulate fluid flow profile of lance-ladle assembly under operating conditions using computational fluid dynamics package ANSYS-CFX. Based on the studies a new curved port lance has been designed which resulted in uniform and swirling flow profile inside the ladle without rotating the lance. Injection through the new lance increased the residence time of the particles and reduced the dead zones. The new design was fabricated and experimented at de-sulphurisation stations and has resulted in reduced flux consumption and treatment time.

Measurement and mathematical simulation of acoustic characteristics of an artificially lengthened vocal tract

Phonation into tubes is used for voice training and therapy. In the present study, the formant frequencies were estimated from measurements of the acoustic pressure and the acoustic input impedance for a plexiglass model of the vocal tract (VT) prolonged by a glass tube. Similar transfer function measurements were performed with a human VT in vivo. The experimental results matched the mathematical modelling and confirmed the legitimacy of assuming rigid walls in mathematical simulations of the acoustic characteristics of an artificial VT model prolonged by a tube. However, this study also proved a considerable influence from soft tissues in the yielding walls of human VT cavities on the first formant frequency, F1. The measured F1 for the VT model corresponded to the computed value of 78Hz. The experiments in a human instead resulted in a much higher value of F1: about 200Hz. The results confirm that a VT model with yielding walls must be considered for mathematical modelling of the occluded or semi-occluded human vocal tract, e.g. prolonged by tubes or straws. This is explained by an acoustic-structural interaction of the vocal tract cavities with a mechanical low-frequency resonance of the soft tissue in the larynx.

Visualization of surfactant solution transport in saturated soil: an experimental study to represent wastewater loss from sewers

Surfactants are the main active agents in detergents products. Our investigation dealt with the effects of surfactants as a wastewater constituent on the infiltration process of wastewater through saturated soil. In order to more closely observe the flow’s interaction, in a laboratory experiment, a 2D Plexiglas model was filled with fine-grained soil and saturated with degassed water. The particle-free artificial laboratory wastewater was created by adding a commercially available detergent to degassed tap water producing a surfactant concentration with the strength equivalent of up to about 15 times of its critical micelle concentration. The visualization of flow was improved by adding a brilliant blue dye tracer enhancing the color contrast. Photographs were taken from the 2D model using conventional imaging equipment and were processed by image analysis to distinguish the dynamic flow interface between dyed and non-dyed areas. Primarily, the images of vertical flows were analyzed after reducing the contrast range. Next, utilizing an image analysis method, 2D images were reconstructed into 3D visualization models. Three-dimensional and cross-sectional images of the fluid–fluid–soil boundary layer revealed a rapid solute transport prevailing at the dynamic interfaces. This was confirmed with image analysis showing geometric irregularities on the soil surface.

Open Volumetric Air Receiver Based Solar Convective Aluminum Heat Treatment Furnace System

Abstract The current heat treatment processes make use of electricity or fuel for generating heat. Solar energy is available in abundance in the states of Rajasthan and Gujarat in India. Annual global solar radiation of about ≥2400 kWh/m2 is received in these regions. Use of the abundant solar thermal energy in heat treatment of metals would saveenergy and fuels. In view of this a concept of solar convective furnace system is described in this paper. As a starting point, heat treatment of aluminium is considered. For this system, requirements of industrial furnace are taken as basis.A scale-down retrofitted furnace is designed and analysed.The importance of different process stages like, solar thermal energy absorption, storage and utilization in design of such a system is presented.A thermodynamic analysis is performed to derive requirements for the achievement of a uniform heating at a pre-determined rate. Control strategy to meet the requirements is worked out. Air flow profile in the furnace is analyzed using CFD as a tool. Laser Doppler Velocimetery technique is used for measurement of velocity in a Plexiglas model of the scale-down furnace. Flow analysis using theadopted CFD tool shows non uniformities in air flow profile. To counter this, further modifications and improvements in the furnace structure are suggested. Evaluation of Open Volumetric Air Receiver (OVAR) using installed solar air tower simulation facility is also presented in the paper.

Study on a New Seismic Isolation System Based on Dynamic Test

A new seismic isolation system entirely different from wildly used Laminated Rubber seismic isolator model was suggested. Vibration table test on the Plexiglas model of the suggested seismic-isolation (S-I) system was carried out. The results show that the seismic force transferred to the superstructure is only about one-tenth of the ground vibrating.

Mixing of cold and hot particles in a pre-lifting scheme with two strands of catalyst inlets for FCC riser

The paper presents a pre-lifting scheme for an FCC riser with two strands of catalyst inlets. The solid volume fraction, particle velocity and the mixing of cold and hot particles in the pre-lifting zone are investigated using optical-fiber and a thermal technique in a large cold Plexiglas model. The heat exchange uniformity is used to quantify the mixing of cold and hot particles under different operating conditions. The whole pre-lifting zone is divided into four regions. The flow characteristics are different in each region, indicating that the particles are redistributed in this proposed pre-lifting scheme. The distribution of heat exchange uniformity shows that the mixing extent of cold and hot particles decreases in the following sequence: the riser entrance region>the central tube region>the bottom region. This may be due to the fact that the cold and hot particles have mixed completely and intensely in the proposed pre-lifting scheme. The mixing of cold and hot particles is quite desirable when the mass flux ratio of cold particles to hot particles is 3:2.

Shear lag analysis of thin-walled box girders based on a new generalized displacement

In many papers about the shear lag analysis of thin-walled box girders, the maximum angular rotation attributable to the in-plane shear deformation of flanges is adopted as generalized displacement. However, the generalized displacement is not very simple and clear and the analytical procedure is relatively complicated. Moreover, various types of warping displacement function for shear lag were assumed which may cause some confusion. In this paper, a new method for analyzing shear lag effect in thin-walled box girders is proposed in which the additional deflection induced by shear lag effect is adopted as the generalized displacement. Based on the generalized moment defined in this paper, the shear lag deformation state is separated from the flexural deformation state of the corresponding elementary beam and analyzed as a fundamental deformation state. The quadratic parabola is demonstrated to be the reasonable curve of the warping displacement function in the shear lag effect analysis of a box girder and the accuracy of the degrees of the warping functions is evaluated. The so-called negative shear lag is illustrated through the generalized moment. The governing differential equation and the boundary condition for the additional deflection are established by applying the principle of minimum potential energy, and the initial parameter solution to the differential equation is provided. A very simple and convenient formula of the shear lag warping stress is proposed which has the same form as that of the bending stress of elementary beam. A finite beam segment element with 8 degrees of freedom is developed to analyze the shear lag effect in complex continuous box girders with varying depth. Two plexiglass models of continuous box girders are analyzed and the calculated results are in agreement with the test results, which validates the analytical method and the element presented.

An Analysis of the Effectiveness of Application of Rotation Rate Sensors in Non Destructive Damage Evaluation

This paper reports the analysis of the effectiveness of the application of rotation rate sensors in structural damage identification problem using harmonic vibrations for plexiglass models of cantilever beams. The two types of sensors are applied: angular rate sensors and conventional translational, piezoelectric accelerometers. The amplitudes of dynamic response under harmonic kinematic excitations were subsequently used in the stiffness reconstruction procedure. Particularly promising results are obtained by using only rotation rate sensors in the reconstruction procedure.

Analysis of the impact of impeller geometry on the turbulent statistics inside a fan-stirred, cylindrical flame speed vessel using PIV

Turbulence statistics of three impellers with different geometric features were measured using particle image velocimetry inside a Plexiglas model (~1:1 scale) of a cylindrical flame speed vessel (30.5 cm ID × 35.6 cm L). With four impellers arranged in a central-symmetric configuration, turbulence intensities between 1.2 and 1.7 m/s with negligible mean flow (0.1u′) were attained at the lowest fan speeds. Acceptable ranges for homogeneity and isotropy ratios of the velocity fields were set within a narrow bandwidth near unity (0.9–1.1). Homogeneity ratios were unaffected by changes to the impeller geometry, and the prototype with the higher number of blades caused the flow to become anisotropic. The integral length scale of the flow fields varied between 27 and 20 mm, which correlates well with those typically observed inside a gas turbine combustor. The mechanism to independently vary the intensity level and the integral length scale was established, where turbulence intensity level was dependent on the rotational speed of the fan, and the integral length scale decreased with increasing blade pitch angle.