Full-scale Ones Research Articles

Testing of a Polymer Drill String Protector under Conditions close to Borehole

With today's proliferation of various polymers, it is necessary to assess the feasibility and feasibility of replacing rubber with more modern materials. The purpose of the tests was to study the effect of abrasive wear, the effect of temperature on material properties, resistance to chipping and other types of wear. This will allow assessing the possibility of application in well conditions, as well as determining the magnitude of the effect of each type of wear on the product. We were faced with the task of testing new protectors in conditions close to full-scale ones. For this, a stand was designed, which allows you to reproduce the lateral load, add abrasive and corrosive agents that affect the wear of the product, ensure circulation of the model fluid, with the characteristics of the drilling fluid, as well as study the effect of elevated temperature on the change in material properties. Due to the fact that in a real well the protector is not under constant load, especially in the vertical sections of the wellbore, but can rotate on the pipe, a day on the test bench can be equivalent to months when the protector is in the well. Therefore, the tests carried out can predict the wear of tread parts, as well as assess the reliability of the use of treads made of polymer materials.

Scale-up of open zeolite bed reactors for sorption energy storage: Theory and experiment

Sorption energy storage (SES) technology has been considered one of the promising solutions to cope with the ever-increasing carbon emissions from buildings. Nevertheless, it is still elusive the extrapolation of conclusions from pilot-scale experiments to full-scale ones. In the present work, a relaxation technique was introduced to develop a scale-up model for SES reactors. A full set of scaling ratios of parameters for an analog reactor to those for a prototype reactor was explored, which theoretically ensured the similarity of the two reactors in geometry, dynamics, sorption-kinetics, and thermal performance. Subsequently, charging and discharging experiments were conducted in two geometrically similar reactors. Four performance ratios of the analog values to prototype values were calculated based on the measured data and were compared with theoretical values derived from the scale-up model. The results showed that these ratios were in good agreement with corresponding theoretical values, where the maximum deviation was less than 10%. Based on the developed scale-up model, a small-scale reactor can duplicate the thermal performance of a large-scale reactor on a miniature dimensional scale and in a reduced time scale.

Оценка методов расчета значений суммарной солнечной радиации для различных интервалов времени

The article presents the results of evaluation of a number of methods for calculating total, scattered and direct radiation. The methods were tested on actinometric data of eight stations of the former USSR, located in different climatic and latitudinal zones, in order to clarify the spatial boundaries of their application and the time interval for which it is possible to carry out calculations with an error of not more than 10 %. It is established that the accuracy of calculations is influenced by the location of the station in relation to the seas and lakes. In addition, a number of methods do not take into account the tier and shape of the cloud, so at the same amount of cloud observed different amounts of total radiation, which in turn leads to errors in the calculation of the amounts of radiation. For stations with high atmospheric transparency and low air humidity, the calculation methods provide understated data compared to full-scale ones. For stations with high dust content of the surface layer of the atmosphere, the calculated data are overstated. For marine and lake stations, overestimation of the calculated data is caused by increased humidity throughout the year and as a result, even with a small cloud cover, incoming solar radiation is significantly weakened by water vapor. The considered calculation methods can be used to calculate monthly amounts of total radiation with an accuracy of 10-12 %. Calculation for shorter time intervals leads to an increase in calculation errors. Using the method of calculating the total radiation components gives an error in the calculation of monthly amounts from 10 to 30 %, depending on the latitude. Performing calculations using this method for time intervals less than a month leads to a sharp increase in the size of errors.

High-Reynolds-number effects simulations for wind effects on a cooling tower model in a wind tunnel based on a statistical approach

The traditional high-Reynolds-number (Re) effects simulation method for wind effects on circular cylindrical models in wind tunnels is fundamentally a trial-and-error practice, which is strongly subjective and laborious. To this end, a mathematically well-founded high-Re effects simulation method is proposed based on the response surface (RS) optimization algorithm in this article. Having the advantages of good considerations of random errors and simplified calculations using the polynomial models, RS method has been widely employed in chemical industry. However, it is seldom employed in physical experiments. Using a case study of Weisweiler cooling tower, it has been proved that model tests using the new high-Re effects simulation method based on RS optimization algorithm can objectively and easily reproduce the mean and the fluctuating wind pressure distributions measured on the spot, and the model-scale spectral characteristics of the wind pressures obtained by using the new high-Re effects simulation method agree well with the full-scale ones. Besides, numerical analyses undertaken on a computational fluid dynamics platform also indicate the validity of the new method.

Effective wake estimation of KCS hull at full-scale by GEOSIM method based on CFD

In this study, the effective wake factors of a self-propelled container ship were investigated by Telfer's GEOSIM method based on CFD (Computational Fluid Dynamics). For this purpose, the self-propulsion characteristics of KCS (KRISO Container Ship) at three different model scales and full-scale were determined at Fr = 0.26 by unsteady RANS (Reynolds Averaged Navier-Stokes) solver. All scales corresponded to a wide range of Reynolds numbers. Turbulent flow around the KCS hull has been investigated by the k-ε turbulence model. Heave and pitch motions of KCS hulls have been modeled with the DFBI (Dynamic Fluid Body Interaction) method and overset mesh technique. The rotational motion of KP505 propeller has been simulated using the RBM (Rigid Body Motion) approach. The result obtained by the extrapolation of the effective wake fraction with the GEOSIM method was compared with the full-scale ones of CFD and ITTC methods. The results by the GEOSIM method are more compatible with those of full-scale CFD than the results of 1978 ITTC method. In the wake region, where viscous effects are predominant, the change of effective wake fraction with Reynolds number has been successfully represented by the GEOSIM method, thus more robust and reliable results have been found.

Assessment of statistical features of the diffused acoustic field in a test section of a cavitation tunnel

Noise measurements in a cavitation tunnel is the preferred approach for predicting the underwater noise radiated by a propeller at sea. The accuracy of the prediction is linked to the similitude laws used to transform the model scale measurements to the full-scale ones. Besides, this accuracy is obviously linked to the accuracy of the model scale measurements. The knowledge of the acoustical features of the facility used to perform such measurements is then one of the key points of such measurements. The proposed communication presents the recent results obtained in the test section of the Large Cavitation Tunnel (GTH at Val-de-Reuil) to describe the statistics of the diffuse acoustic field. The results show that the diffuse field complies spatially very well with the Gumbel distribution for narrow band levels (expressed in dB for the power spectral density). The limit of the statistical domain (defined as the “Schroeder frequency”) is also estimated thanks to the experimental measurements performed inside the test section.

Scaling effect on the moment and shear responses of three types of beam-to-column connectors used in mass timber buildings

To fully understand the structural behaviour of large structural systems under given loading scenarios, experimental testing of the entire system or of a representative part of it is often required. However, due to limited laboratory space and budget restrictions, tests are frequently performed on scaled down systems. The scaled tests allow investigating the influence of a large number of parameters, therefore providing in-depth understanding of the structural system response, an opportunity rarely achievable in full-scale testing due to cost related issues. As timber is known to be sensitive to size effects, it is unclear (i) how accurately tests performed on a scaled down timber structure would reproduce the full-scale system response and (ii) how scaled tests results must be interpreted to consider the scaling effect. This paper experimentally investigates the full-scale and quarter-scale moment and shear non-linear responses of three types of beam-to-column connectors currently used in post-and-beam mass timber buildings. Moreover, the paper discusses (i) how tests performed on scaled down timber buildings can be extrapolated to full-scale structures, and (ii) presents recommendations for the scaled down specimens to best replicate the response of the full-scale ones. A total of 12 full-scale and 18 quarter-scale tests were performed. Considering the scaling factor, results show that the overall non-linear responses of the quarter-scale connections closely match the full-scale responses. However, still taking into account the scale factor: (i) the average ratio of the quarter-scale to full-scale elastic stiffness is 0.74 and (ii) the tests performed on the scaled down connections typically result in a capacity 1.2 times higher than the capacity of the full-scale systems. Results also demonstrate the importance of using steel or aluminium connectors with similar material ductility in both the scaled down and full-scale connectors.

Numerical investigation of fluid dynamics phenomena in external gear pump

A three-dimensional numerical model able to describe the performance of a gear pump taking into account turbulence and cavitation is presented. The computational model is implemented in the ANSYS CFX software package. As a method for modeling moving boundaries (taking into account the rotation of gears), the method of "immersed solid" is chosen. A homogeneous two-phase model is used to describe the flow of a viscous incompressible fluid with the formation of cavitation. The adequacy of the developed model is checked; the analysis of the numerical stability and convergence of the solution is carried out. With this model, a number of computational experiments were carried out at the experimental design stage to create a fuel system for a promising gas turbine engine. The technical characteristics of the pump, such as the flow rate, presence and degree of cavitation, were checked. Simulation results for different pump operating modes are analyzed. Comparison of the numerical results for single-phase and two-phase flow is performed. The places of cavitation formation and its level are shown and justified. The localization and volume of cavitation areas, cavitation concentration, and the level of its possible influence on the consumable-technical and strength characteristics of the product are examined in relation to the rotational speed of gears. It has been found that cavitation areas are formed, especially, at high gear speeds. The simulation results are presented in the form of graphical functional dependencies and contour plots. The developed numerical model of the gear pump makes it possible to carry out computational experiments instead of expensive full-scale ones, and to give recommendations for preventive improvement of the design, even before the manufacture of prototypes of the product.

Measurement of exhaust gas emissions from miniature turbojet engine

This paper presents a methodology developed to measure exhaust gas emissions during operation of a miniature turbojet engine, using a laboratory test rig. The rig has been built for research and development works aimed at modelling and investigating processes and phenomena occurring in jet engines. The miniature jet engines, similarly to full–scale ones used commonly in air transport, are characterized by variable exhaust gas emissions, depending on engine operating parameters. For this reason, an attempt has been made to determine the characteristic features of miniature engine operation modes and to define the variability of operation parameters and exhaust gas emissions as a function of time. According to the authors, the preliminary tests allowed for defining specific profile of engine test, which enables proper measurement regarding exhaust gas emissions using the miniature jet engine. The paper also presents test results for Jet A-1 fuel, according to the used methodology.

Size effect on fire resistance of structural concrete

Research on the size effect of reinforced concrete members at ambient temperatures includes only limited studies on the size effect of their fire resistance, integrating thermal and structural similitudes. Preliminary testing on concrete cylinders and unreinforced beams showed a ¼ ASTM E-119 exposure time for the fire rating of small scale specimens compared to the full scale ones. Based on numerical and experimental analyses at Florida Atlantic University, the following quantitative relationships were developed for columns and beams: (i) equivalent fire duration and specimen size; (ii) fire endurance and cross-section size, and (iii) cross-section size, concrete cover thickness, and load capacity after fire exposure. The fire endurance at similar load ratios increases with an increase of member cross-section size and concrete cover thickness.

Full scale wake prediction of an energy saving device by using computational fluid dynamics

Recently interest on energy saving devices (ESD׳s) has increased with the enforcement of the energy efficiency design index (EEDI) verification proposed by the International Maritime Organization (IMO). Extension of propulsive performance results from model to full scale ships plays an important role in verification of ships with ESD׳s. The present study proposed a reliable and efficient propulsive performance prediction method for full scale ships with ESD׳s. The propulsive performance prediction in full scale KVLCC2 with pre-swirl stator (PSS) was conducted by the proposed method. Its results were then compared with those by the existing extension methods and by full scale CFD computations. From the results, it was confirmed that the proposed method could extend the model scale results to full scale ones with ESD׳s performance improvement effects. Unlike the existing methods, it takes into account of ESD׳s and consumes much less computational resources and time than full scale CFD computations.

Numerical Study on Similarity of Plume’s Infrared Radiation from Reduced Scaling Solid Rocket

Similarity of plume radiation between reduced scaling solid rocket models and full scale ones in ground conditions has been taken for investigation. Flow and radiation of plume from solid rockets with scaling ratio from 0.1 to 1 have been computed. The radiative transfer equation (RTE) is solved by the finite volume method (FVM) in infrared band 2~6 μm. The spectral characteristics of plume gases have been calculated with the weighted-sum-of-gray-gas (WSGG) model, and those of the Al2O3particles have been solved by the Mie scattering model. Our research shows that, with the decreasing scaling ratio of the rocket engine, the radiation intensity of the plume decreases with 1.5~2.5 power of the scaling ratio. The infrared radiation of the plume gases shows a strong spectral dependency, while that of the Al2O3particles shows grey property. Spectral radiation intensity of the high temperature core of the solid rocket plume increases greatly in the peak absorption spectrum of plume gases. Al2O3particle is the major radiation composition in the rocket plume, whose scattering coefficient is much larger than its absorption coefficient. There is good similarity between spectral variations of plumes from different scaling solid rockets. The directional plume radiation rises with the increasing azimuth angle.

Full-scale and reduced-scale tests on smoke movement in case of car park fire

Full-scale and reduced-scale measurements along with numerical simulations have been carried out in order to increase fire safety in car parks, with particular focus on the smoke back-layering (SBL). SBL is the distance covered by the smoke upstream of the ventilation flow with respect to the fire source. It has been measured in both full- and reduced-scales and the results are compared to the literature. The investigated car park (full- and reduced-scale) has been simplified: ceiling and walls are plain and the final layout is similar to a very wide road tunnel. Horizontal and vertical beams supporting the ceiling are not considered. Therefore the results obtained are only valid for large closed parks with a flat ceiling and uni-directional smoke and ventilation patterns within the investigated heat release rate range. The study serves double purposes:Empirical formulae can be obtained and the best model for SBL can be chosen from the existing correlations for road tunnel fires to be applied to car parks with the above described simplified geometries.If the results of the reduced-scale car park model are in accordance with the full-scale ones, the reduced-scale model can be used for more complex car park layouts, which is a very favorable solution in terms of both time and costs.In addition to the SBL investigation, unexpected flow phenomena at the entrance and extractors, respectively, are also explained by reduced-scale trials.

A numerical model of a HIL scaled roller rig for simulation of wheel–rail degraded adhesion condition

Scaled roller rigs used for railway applications play a fundamental role in the development of new technologies and new devices, combining the hardware in the loop (HIL) benefits with the reduction of the economic investments. The main problem of the scaled roller rig with respect to the full scale ones is the improved complexity due to the scaling factors. For this reason, before building the test rig, the development of a software model of the HIL system can be useful to analyse the system behaviour in different operative conditions. One has to consider the multi-body behaviour of the scaled roller rig, the controller and the model of the virtual vehicle, whose dynamics has to be reproduced on the rig. The main purpose of this work is the development of a complete model that satisfies the previous requirements and in particular the performance analysis of the controller and of the dynamical behaviour of the scaled roller rig when some disturbances are simulated with low adhesion conditions. Since the scaled roller rig will be used to simulate degraded adhesion conditions, accurate and realistic wheel–roller contact model also has to be included in the model. The contact model consists of two parts: the contact point detection and the adhesion model. The first part is based on a numerical method described in some previous studies for the wheel–rail case and modified to simulate the three-dimensional contact between revolute surfaces (wheel–roller). The second part consists in the evaluation of the contact forces by means of the Hertz theory for the normal problem and the Kalker theory for the tangential problem. Some numerical tests were performed, in particular low adhesion conditions were simulated, and bogie hunting and dynamical imbalance of the wheelsets were introduced. The tests were devoted to verify the robustness of control system with respect to some of the more frequent disturbances that may influence the roller rig dynamics. In particular we verified that the wheelset imbalance could significantly influence system performance, and to reduce the effect of this disturbance a multistate filter was designed.

Simulating the full-scale sea trials in the towing tanks using polymer drag reduction

We discuss the approach to simulate the experiments with surface and underwater vehicles in towing tanks for Reynolds numbers corresponding to the full-scale ones using discrete injection of polymer additives. Experimental data on velocity profiles and local skin-friction coefficient in turbulent boundary layer of vehicles and their models are given. Results of the simulating tests demonstrate a good agreement with sea trials.

Effect of the format of antibodies on their specificity

The influence of alterations in the format of antibodies on their specificity has been examined. To analyze the role of Ig constant regions in recognizing antigens, a comparison was made of the specificities of full-scale murine monoclonal antibodies and scFv single-chain miniantibodies obtained from the latter with regard to a group of closely related protein antigens – Staphylococcus enterotoxins. It was found that in the scFv format the specificity and affinity of miniantibodies diminished as compared to the full-scale ones. Specificity of antibodies may be enhanced by transforming them into full-scale antibodies. Moreover it was shown that miniantibodies within a phage particle generated from combinatorial phage libraries possess greater specificity to the antigen, however during the subsequent transformation to soluble scFv antibodies their specificity diminishes.

내침식페인트 성능 판별에 적합한 새로운 캐비테이션 침식시험기법 개발

The very erosive cavitation is simulated by an inclined propeller dynamometer in the medium-size cavitation tunnel of MOERI. The inclined shaft for propeller makes strong cavitaion, which occurs around the root of a propeller blade. The cavitation begins at the leading edge of the propeller and contracted toward the trailing edge through the reentrant jet action. The cavity focused on the region near the trailing edge collapsed over the blade surface. As the impact pressure by the cavitation collapsing is too strong, it can damage the blade surface in the form of pit. This cavitation impacts created by the collapsing process are similar to the full-scale ones and are different from those by other erosion test methods. The newly developed cavitation erosion test method can be applied to evaluate the materials such as metals, ceramics and coatings in terms of cavitation resistance.