Full-size Experiments Research Articles

A low-resistance local component design method based on biomimicry and a random forest model: A pipe elbow case study

The energy consumption of building transmission and distribution systems accounts for more than 30% of building energy consumption, and the prevalence of localized components in building transmission and distribution systems leads to severe energy losses and resistance effects during system operation. To solve this problem, our research team has developed a series of resistance reduction components. This paper proposes a low-resistance local component shape optimization method based on biomimicry and machine learning, taking pipe elbows as an example, and the normalized shape optimization parameters of elbows with different pipe diameters are given. Through numerical simulation, full-size experiments, energy dissipation analysis and other methods, the optimized elbow resistance reduction effect and resistance reduction mechanism are verified and analyzed. The results showed that the resistance reduction rate of the elbow was 19%–26% for different pipe diameters and Reynolds numbers, and the optimized elbow significantly reduced energy dissipation during the flow process. Previously, the shape optimization problem of local components focused mainly on rectangular ducts that can be simplified in two dimensions; this study extends the optimization objective to circular pipes, which provides an effective method for guiding the optimal design of low-resistance local components in building transmission and distribution systems.

Analysis of the results adequacy of the fuselage finite-element modeling in the vicinity of a large cutout

The issues of ensuring the reliability of the finite element models (FEM) of the fuselage in the hatch cutout zone are considered at the early aircraft design stages. The purpose and tasks of research are formulated. To assess the reliability of mathematical models, the objects with standards were selected. The methods of experimental research and measuring instruments are discussed. The results of a comparative analysis of the numerical experiment with analytical solutions and full-size experiments data are presented. For the validation of FEM structures, the checkable characteristics and types of their verification are determined. The results of this research contain a discussion of the impact of finite element mesh details on a stress concentration factor, an adequacy of modeling the stress and strain field in the vicinity of the cutout and taking into account a nonlinearity in strength calculations of structures with stress concentration. This paper focuses on the analysis of modeling a framed cylindrical shell with a large rectangular cutout, for which full-size tests were conducted by TSAGI researchers. Strains of strong frames, limiting the cutout in a cylindrical shell, shearing and equivalent stress in the skin, normal stresses in stringers at the intersection with the strong frame, displacements of strong frames cross-sections at test points are analyzed. Based on the results of this research, the recommendations for modeling thin-walled fuselage structures in the vicinity of a large cutout, ensuring the performance of calculations with engineering accuracy were formulated.

Adaptive leak signal extraction based on EMD-CC for water pipeline leak location

When using acoustic methods for water pipeline leak localization, noise will significantly affect the accuracy of localization, especially for the case that the noise intensity far exceeds the signal intensity, the traditional noise reduction methods will be ineffective. Therefore, an empirical mode decomposition and cross-correlation (EMD-CC) method for leak localization is proposed, which can adaptively extract effective leak signals from low signal-to-noise ratio (SNR) detection signals, and then can significantly improve the accuracy of localization. In this paper, the principle and steps of the algorithm are elaborated, and the effectiveness is verified in simulations and experiments. In the simulations, the SNR of the reconstructed signal −15 dB is dramatically increased to −6 dB. Compared with conventional noise reduction methods, the time-delay value estimation of EMD-CC is more accurate, more reliable, and more noise resistant. In full-size experiments, the accuracy of localization after processing is significantly improved.

Fully transient coupled prediction model of wellbore temperature and pressure for multi-phase flow during underbalanced drilling

Considering gas-liquid-solid three-phase flow and heat transfer, the accurate simulation of wellbore temperature and pressure profile while underbalanced drilling (UBD) has been predicted significantly in deep well drilling. Firstly, the research presents a fully transient coupled prediction model of wellbore temperature and pressure field and the thermophysical properties of circulating fluid are taken into consideration, and a double-cycle iterative algorithm for the axial and radial coupled solution of wellbore temperature and pressure is proposed. The model is discretized by using the finite volume method and is verified by the two-phase flow temperature and pressure data from the Louisiana full-size experiments. Then, qualitatively and quantitatively comparisons with water-based mud (WBM) and oil-based mud (OBM) to analyze the coupled variation of transient wellbore temperature and pressure. The sensitivity analysis between WBM and OBM is carried out and WBM is more sensitive to the thermophysical properties compared with OBM. Finally, the feasibility study of calculating bottom-hole pressure according to simple linear temperature is launched. It is found that the average of formation temperature and linear cyclic temperature (AFLT) model that a simplification of the temperature model due to the approximate method is more accurate and convenient between WBM and OBM. This research on wellbore temperature and pressure profile intuitively understands the complex problems of wellbore multi-phase flow, and further provides a theoretical reference for controlling well kick and extending to horizontal, highly deviated well and geothermal wells.

Study on the Protection Effect of Sprinklers on Glass by Fire Scale in Building Fires

Window sprinklers are commonly used to protect glass, but there is a lack of research on the effect of fire scale on protection. In this study, full-scale experiments on sprinkler-protected glass in building fires were carried out. The experimental process was simulated using CFD numerical simulation software (FDS), and the effect of the heat release rate on the protection effect was revealed based on the glass surface temperature and heat insulation efficiency. It was found that in a full-size compartment fire, the window sprinkler was able to protect the glass from being damaged by high-temperature smoke. The numerical simulation could effectively simulate the spray distribution pattern of a window sprinkler as well as the gas temperature evolution, and the simulation results matched well with the full-size experiments. The window surface temperatures all decreased rapidly and increased linearly with the HRR after the window sprinkler was activated. The steady-state window center temperatures were 40 °C, 60 °C and 76 °C when the HRR was 2 MW, 4 MW and 6 MW, respectively. The window center temperature was less than the critical temperature of glass breakage, indicating that the window sprinkler could protect the glass from fire damage well, within the fire scale of 6 MW. The thermal insulation efficiency in the edge region was slightly lower than that in the center of the window. In the range of 2 to 6 MW, there was no significant correlation between the thermal insulation efficiency and the HRR, and the thermal insulation efficiency was in the range of 54% to 59%.

Predicting extrusion process parameters in Nigeria cable manufacturing industry using artificial neural network

The extrusion process is a very complex process due to the number of process parameters that are associated with it which are prone to high fluctuations. The main purpose of this work is to determine the realistic extrusion process parameters in the thermoplastic extrusion process in Nigeria cable manufacturing industries with the use of an artificial neural network. Conventionally, the use of trial and error technique which involves full-size experiments is generally used to determine the process parameters in the thermoplastic extrusion process. This conventional technique is expensive and it is also time-consuming. The use of an artificial neural network to predict extrusion process parameters before plant execution will make extrusion process operations more efficient. This technique also bridges the gap that exists between theoretical analysis and real manufacturing system because real manufacturers' data was used. The neural network was developed in a MATLAB environment and was trained with a supervised learning method based on Levenberg Marquardt Algorithm and the developed ANN model is capable of predicting manufacturing process parameters for different grades of PVC thermoplastic material.

Air Curtains Combined with Smoke Exhaust for Smoke Control in Case of Fire: Full-Size Experiments

This paper analyses the possibility of using air curtains to prevent smoke flow from fire compartments. Full size experiments have been carried out and several relevant conditions to assess smoke-tightness have been tested. The smoke temperature during the tests was ranging from 182°C to 351°C, the angle measured between the curtain axis and the vertical plane was ranging from 18° and 26°, the nozzle thickness was ranging from 0.017 m to 0.045 m and the velocity at the nozzle was ranging from 8.3 m/s to 19.9 m/s. During the tests, the air curtain’s nozzle was positioned horizontally at the top of a permanent opening (door). With this configuration, we obtained an approximately vertical downward jet through the used opening. This paper includes the final results of the tests and develops an analytical tool for predicting the performance of air curtains. It was concluded that it is possible to achieve smoke-tightness, provided that the adequate plane jet parameters and the compartment’s smoke exhaust are correctly adjusted. According to this analysis, the smoke-tightness limit corresponds to equation $$ B = \Delta {\text{P}}_{\text{a}} /\Delta {\text{P}}_{\text{s}} = - 0.30 \,u_{a} /u_{a\_min} + 1.25 $$ (with $$ 1.30 \le u_{a} /u_{a\_min} \le 1.67 $$ ).

Selection of Optimal Hot Extrusion Process Parameters for AA6061-Fly Ash Composites

The simulation of hot extrusion process is a challenging problem in process modeling because of very large deformations, strain rates and temperature changes during the process. The process development in industrial extrusion is to a maximum extent based on trial and error and often involves full size experiments. Numerical simulations can replace most of these experiments, which are often both time consuming and expensive. Hence in the present work, attempt has been made to simulate hot extrusion process. AA6061-flyash Metal Matrix Composite(MMC) as billet, H13 tool steel as the die, 400oC as billet temperature and extrusion ratio of 25:4 are used as simulation parameters. Simulation is performed using software DEFORM 3D by varying ram speed, Cone Half Angle (CHA) and friction coefficient with extrusion load. The effects of change of process parameters were observed and optimal process parameters were selected.

Failure modes and loading bearing capacity of corrugated steel roofs connected by standing seam clips

This paper presents the research on failure modes and loading bearing capacity of two types of purlin-sheet roofs under uniform loadings. The full-size experiments are carried out on the purlin-sheet roofs and the allowable design stress and design proposals are proposed. Besides, the finite element analysis is conducted to compare with the experiments. Results show that the failure modes and loading bearing capacity of two types of purlin-sheet roofs are different. The first is that the adjustments are pulled out from the base, while the mechanical occlusions between the adjacent sheet and adjustments are well. The latter is that the mechanical occlusions between the adjustment and sheets are tensioned fracture, while the adjustment are tensioned straight and pulled out from the sheets. The numerical calculations and experiment data are in good agreement, and the deviations are mainly because of initial defects of specimens, construction errors of specimens and loading protocols. The numerical calculation method is reliable and can be used to analyze the sheet-purlin roof connected by standing seam clips.

Mathematical modeling of air coolers of indirect evaporative type

The method of integrated modeling of interconnected heat and mass transfer processes in air coolers of evaporative type has been developed. Air cooler of indirect evaporative type was taken as the object of research. Water was used as the evaporating agent. Basic schemes of airflows were considered: cross-flow and counter-flow. Partitioning of the problem into a number of subtasks (air flow distribution among channels, heat and mass transfer in the channel system) was proposed. Decomposition of the device structure into a number of elements was done. Mathematical models of interconnected processes of heat and mass transfer are given as a system of nonlinear ordinary differential equations in a one-dimensional statement. The developed efficient methods of joint solution of the mathematical model equations were used in simulation. A modified robust method for simulation of media flows in the channels of a complex profile (two-dimensional fields of velocity and temperature) was proposed. Joint solution of continuity equations, Navier-Stokes equation (in projections to the coordinate axes), Fourier equation and pressure equation was carried out. The method is invariant as to the channel shape and the properties of the working media. The method of calculation of heat exchange coefficients with the use of the obtained velocity and temperature fields is set forth. This enables to refine results of modeling of the processes proceeding in coolers. Computational and full-size experiments for a number of designs and operation conditions of air coolers were conducted. Comparative analysis of the obtained results has shown reliability of the proposed methods of mathematical modeling. Discrepancy between the calculated and experimental values of the cooled air temperature did not exceed 0.5 °C. The described method of mathematical modeling enables obtaining reliable information necessary to optimize the design and working conditions of coolers. The developed method of mathematical modeling of the heat and mass transfer processes can be used for a detailed study of various types of heat exchangers.

Gas-shielded welding with electrode oscillations. Thermal problem

A method is proposed for calculating the temperature field in welding with trapezoidal oscillations of the welding arc, including the equation of the temperature field for the scheme of the moving surface heat source with normal distribution, the equation of trapezoidal oscillation in the form of the sum of Fourier series and the experimentally determined dependence of the effective radius of the heating spot of the arc r0 on the welding conditions. The dependence of the effective radius of the heating spot of the arc r0 on the welding conditions is determined by the similarity methods for welding of low-carbon and low-alloy steels in CO2 and a mixture of the gases Ar + 20% CO2. The comparison of the calculated temperatures and the results obtained in full-size experiments in welding of the pipes shows that the proposed calculation method results in sufficiently accurate determination of the temperature fields for practical applications.

The use of scale models in ground tests reproducing heat transfer in space

It is suggested to use the method of experimental investigation of temperature conditions at the spacecraft with application of their reduced thermal models based on the similarity criteria formulated under the assumption of the mathematical nodal model of the studied object. Usually thermal-vacuum experiments with full-size object have tight time constraints due to a significant cost. However, on the basis of result of this limited experiment we can specify the parameters of the scale model developed using the nodal mathematical model. This correction ensures the compliance between the results of full-size and scale experiments. After that the scale thermal experiment can supplement the full-scale experiment due to investigation of thermal conditions, which cannot be reproduced experimentally in the full-scale experiment because of the limited resources. The suggested method will significantly expand the possibility to get reliable experimental data about the temperature modes of space objects without a considerable increase in costs.

Analyses of a pile-supported embankment over soft clay: Full-scale experiment, analytical and numerical approaches

The reinforcement of soils using rigid inclusions is a technique used to reduce settlements and to ensure the stability of an embankment built over soft soils. This technique reduces construction delays and is an economical and reliable solution, which has led to its widespread use. Thus, many design methods have been developed to assess the performance of these reinforced structures. These methods are mainly based on results from small scale models and numerical analyses. The reliability of these methods must be validated under in-situ conditions.This paper presents an analytical and numerical study of full-size experiments at the Chelles test site (France). The work presented in this paper is part of the ASIRI French National Research Project. The experiment consisted of a 5-m-high embankment built over soft alluvial ground improved by rigid vertical piles. The embankment is divided into four zones that illustrate the influence of the piles and the geosynthetic reinforcements on the soil's behavior. The performance of the embankment support system is assessed by monitoring data (total stresses, horizontal and vertical displacements). Several in-situ and laboratory soil investigations were performed using two axially loaded test piles. These tests verified the geotechnical hypothesis used for the numerical model and defined the soil–pile interaction parameters.Several analytical methods and numerical models were tested to assess the arching effect. Comparisons between the experimental data and these design methods are presented in terms of stress and the settlement efficacy of the improved system. The results show that these methods overestimate the stress efficacy but that the settlement efficacy is a reliable parameter to assess the overall performance of the rigid inclusion technique.

3D Finite element analysis of end - plate steel joints

This paper presents a numerical investigation of the mechanical behaviour of extended end - plate steel connections including comparison with full size experiments. Contact and friction laws have been taken into account with nonlinear, three dimensional finite element analysis. Material and geometric nonlinearities have been implemented to the model, as well. Results are then compared with experimental tests conducted at the Jordan University of Science and Technology. According to the most significant observation of the analysis, a separation of the column flange from the extended end - plate occurs. Other important structural parameters of the connection, like the impact of some column stiffeners on the overall response, local buckling of the column and friction of the beam to column interface, have been examined as well.

Numerical Study of the Effect of Ventilation Pattern on Coarse, Fine, and Very Fine Particulate Matter Removal in Partitioned Indoor Environment

An indoor size-dependent particulate matter (PM) transport approach is developed to investigate coarse PM (PM10), fine PM (PM2.5), and very fine PM (PM1) removal behaviors in a ventilated partitioned indoor environment. The approach adopts the Eulerian large eddy simulation of turbulent flow and the Lagrangian particle trajectory tracking to solve the continuous airflow phase and the discrete particle phase, respectively. Model verification, including sensitivity tests of grid resolution and particle numbers, is conducted by comparison with the full-size experiments conducted previously. Good agreement with the measured mass concentrations is found. Numerical scenario simulations of the effect of ventilation patterns on PM removal are performed by using three common ventilation patterns (piston displacement, mixing, and cross-flow displacement ventilation) with a measured indoor PM10 profile in the Taipei metropolis as the initial condition. The temporal variations of suspended PM10, PM2.5, and PM1 mass concentrations and particle removal mechanisms are discussed. The simulated results show that for all the of the three ventilation patterns, PM2.5 and PM1 are much more difficult to remove than PM10. From the purpose of health protection for indoor occupants, it is not enough to only use the PM10 level as the indoor PM index. Indoor PM2.5 and PM1 levels should be also considered. Cross-flow displacement ventilation is more effective to remove all PM10, PM2.5, and PM1 than the other ventilation patterns. Displacement ventilation would result in more escaped particles and less deposited particles than mixing ventilation.

Development of highly efficient building steel frame construction techniques that improve earthquake resistance. Full size experiments and results of demonstration obtained from the fabrication of model building steel frames

Development of highly efficient building steel frame construction techniques that improve earthquake resistance. Full size experiments and results of demonstration obtained from the fabrication of model building steel frames

Investigation of temperature and oil flow in EHV sealing ends

The highest conductor temperature in a cable system often occurs within a cable accessory rather than in a straight cable run. It is therefore important to study temperatures in cable accessories, both with full-size experiments and using computer models. The paper reports a combined experimental and theoretical study of one such cable accessory, namely a typical 400 kV outdoor sealing end. Measurements on such a sealing end have been made by KEMA in the Netherlands. Corresponding computer modelling has been done at the Central Electricity Research Laboratories of the CEGB in the UK. Both the measurements and the predictions are described here. Two related computer models have been used: one is a finite-element model of the complete sealing end and adjacent cable and conductor; the second is a detailed model of the natural convection oil flows within the main oil region of the sealing end.Good agreement has been obtained between measurements and predictions for three current loadings. Natural convection has been shown to be very important in the outer oil annulus, and it is essential to model this to obtain realistic temperature predictions. The application of the present method to other sealing ends is considered.

Characteristics of Fire inside a Room of Fire-Proof Construction ( 3 ) (In Full-Size Experiments)

Characteristics of Fire inside a Room of Fire-Proof Construction ( 3 ) (In Full-Size Experiments)