Papers by Keyword: Sensitivity Analysis

Abstract: Shear strength probabilistic assessment of concrete members with glass fibre reinforced polymers (GFRP) is performed in the paper. The aim of the analysis performed is to verify the existing code analytical formulas for shear strength calculation using stochastic models, to perform uncertainty propagation, sensitivity analysis and model uncertainty assessment. The study introduces a probabilistic framework that incorporates both model uncertainty and stochastic variability of input parameters into the assessment of shear resistance. The code models of Eurocode 2, ACI 440 and the fib Model Code 2010 are examined with respect to uncertainties involved and the reliability of the design value determination.

Abstract: This study investigates the combined stability and sensitivity study of MHD radiative squeezed hybrid nanofluid flow between two parallel circular porous disks. Although numerous studies have examined magnetohydrodynamic (MHD) flows, thermal radiation effects, squeezed-flow configurations, and nanofluids in porous media, existing literature typically addresses these effects in isolation or in simplified combinations. Most prior works have focused on single-nanoparticle nanofluids, neglecting the enhanced thermo-physical behavior of hybrid nanofluids containing two different nanoparticles. The hybrid nanofluid comprises a base fluid embedded with two distinct nanoparticles, enhancing its thermal and flow properties. Several complex interactions including magnetic fields, thermal radiation, resistance in porous media, and squeezing effects influence the flow and thermal characteristics. A system of nonlinear partial differential equations is constructed and then converted into a dimensionless form through the application of similarity transformations. Subsequently, the dimensionless equations are solved using a power series method, and the resulting solutions are analyzed through the Hermite–Padé approximation scheme. A comparison between the current data and a published result has been made with a good agreement. The effect of flow parameters such as porosity parameter, squeeze number, Prandtl number, Eckert number, and radiation parameter on velocity and temperature fields is illustrated graphically. The skin friction coefficient and local heat transfer rate are also evaluated for the relevant physical parameters. The stability of the local heat transfer rate is examined through a bifurcation curve, which indicates that the lower branch represents a stable and physically realizable solution, while the upper branch corresponds to an unstable state. Sensitivity analysis is performed to measure the influence of key dimensionless parameters such as the squeeze number, porosity parameter, and radiation parameter on the local Nusselt number and the result of our model is significant. This work has potential applications in thermal management systems, energy devices, and advanced cooling technologies.

Abstract: Understanding the relationships between microstructure and (mechanical) properties is inevitable for the design of modern structural metallic materials. A crucial property for most high-strength steels is ductile damage tolerance, since ductile damage can accumulate during cold forming, which either leads to failure in the forming process or subsequently affects the performance. Structure-property relations are often investigated using numerical methods, e.g. crystal plasticity (CP) modeling with representative volume elements (RVE). In a previous study, CP-simulations on 3D-RVE were coupled with surrogate modeling techniques performing a variance-based sensitivity analysis. This analysis enables quantitative descriptions of the relationships between microstructure features with the damage tolerance, quantified by individual indicators for individual damage mechanisms. To investigate the effect of the material model and the corresponding phase properties, 500 sRVE simulations were carried out with different CPparameter sets and the damage tolerance is investigated. All sets stem from the same DP800 but were calibrated with different approaches. Surrogate models were trained on the simulative database to calculate Sobol Indices (SI), which are a measure of how strong damage tolerance is affected by a particular microstructure feature. The SI are compared for the individual material models and damage indicators. The structure-property quantification is heavily influenced by the different material models, resulting in different values for the SI and a different order for the individual microstructure features. The main factor for the pronounced differences is the differently evolving mechanical phase contrast between ferrite and martensite.

Abstract: Varying boundary conditions, such as convection, radiation, and contact thermal exchange parameters in Directed Energy Deposition (DED) process modeling, can significantly impact the predicted thermal fields [1] and final properties of a product. The current numerical study analyzes the effect of different boundary conditions on the temperature distribution during DED thanks to a 3D model of AISI M4 tool steel validated by an experimental campaign. It also confirms that a 2D FE model can already provide valuable trends about sensitivity of numerical results to boundary conditions. The accuracy and robustness of the 2D and 3D model predictions are analyzed. The temperature histories of a set of points at different heights in the clad and the melt pool dimensions provide experimental validation.

Abstract: This paper presents an initial investigation into the numerical modeling of additive manufacturing processes for AlNiCo magnets. The research concentrated on calibrating the heat source parameters by utilizing previously published experimental results. The influence of laser power and scanning speed on the laser fusion of AlNiCo5 on SS 304 substrates was investigated through single track experiments. The geometries of the melt pools were measured and utilized as the foundation for model calibration. A two-step calibration methodology was adopted: (1) a simplified 2D model implemented in Octave was used for sensitivity analysis and parameter fitting; and (2) validation was performed using a 3D model within the commercial software Simufact Welding software. Parameters calibrated through 2D simulations could be directly transferred to the 3D context. However, while the calibration procedure enabled accurate fitting for individual tracks, it resulted in globally non-optimal parameters, suggesting that process parameters influence laser penetration depth.

Abstract: Ammonia can be produced from a wide range of raw materials such as coal, natural gas, coke and oil. Coal gasification is a process that converts biomass or fossil fuel-based carbonaceous materials into CO, H₂ and CO₂. A cryogenic air separation process was used to obtain oxygen from air because of high purity and high amount of oxygen, which will be used for coal gasification. For an ammonia synthesis process using pure oxygen gasification, the energy consumption of cryogenic air separation occupies a large proportion. The aim is to reduce energy consumed in the ammonia plant. The models of the process were developed with the aid of Aspen Plus. The energy consumption of the different processes was obtained through energy analysis, economic analysis and sensitivity analysis. From the three simulations, it can be seen that Simulation 3 produced oxygen with the highest purity of 0.979. From the energy analysis, the energy consumed on the total utilities in Simulation 1 was 5.626×10¹⁰ BTU/h with an energy savings of 1.55%, the energy consumed in Simulation 2 was 5.286×10¹⁰ BTU/h with an energy savings of 1.53% while the energy consumed on the total utilities in Simulation 3 was 1.425×10⁹ BTU/h with an energy savings of 74.90%. Simulation 3 consumed the least energy. The economic analysis showed the total cost of each plant for a 10-year duration. Simulation 1 had a total operating cost of 42.083 billion USD/year, Simulation 2 had a total operating cost of 41.9615 billion USD/year and Simulation 3 had a total operating cost of 918.841 million USD/year. Therefore, Simulation 3 consumed the least cost of total operation. It can also be seen that the higher the energy consumption in a plant, the higher the total cost of the plant as Simulation 3 consumed the least energy, which justified that. Simulation 3 is the air separation plant that optimises the energy consumption, thereby reducing the energy consumed in the whole ammonia plant.

Abstract: The paper concerns the problems related to applying the complex variable step method for the sensitivity analysis of the steady temperature field in the solid body domain due to the perturbations of the geometrical and physical parameters. The optimization problem using the approach proposed is also discussed. At the stage of numerical modelling, the boundary element method is used. The first part of the paper is devoted to the shape sensitivity. The results obtained are compared with the solution resulting from the implicit approach of sensitivity analysis. In the second part, the practical problem concerning optimizing the geometry of continuous casting mould cross-section is considered. The project variable vector contains the cooling pipes' radius and the volume flow rate of the cooling water. The numerical results and the conclusions are presented in the final part of the paper.

Abstract: Fly ash is widely used for replacing partial cement and producing high-performance concrete. The concrete production company is interested in the optimal substitute ratio of fly ash. This study presents a general procedure for evaluating the optimal substitute ratio of fly ash. First, the compressive strength of fly ash blended concrete is evaluated based on adaptive neuro-fuzzy inference system (ANFIS). The water-to-binder ratio, fly ash replacement ratio, and ages are used as input parameters of ANFIS. Strength is the output parameter of ANFIS. Second, sensitivity analysis is performed using ANFIS. The development of relative strength of fly ash blended concrete is calculated considering water-to-binder ratio, fly ash replacement ratio, and ages. The analysis results show that the optimal replacement fly ash is dependent on water-to-binder ratio of concrete. As thewater-to-binder ratio decreases from 0.5 to 0.3, the optimal substitute ratio of fly ash increases from 15% to 30%.

Abstract: Pressure drop in a vertical or deviated borehole has been found to be due to hydrostatic changes and friction as a result of the produced fluids flowing to the surface. When oil flows upwards, the flowing pressure along the tubing string drops, and this makes gas to start liberating. Thus, multiphase flow forms in the tubing string. Hence, adequate modelling of vertical lift performance is required to predict the pressure drop and subsequently the wellbore pressure because many factors are involved [1]. In this work, sensitivity analysis of multiphase flow in a well has been carried out with the aid of PROSPER in which the most accurate correlation was chosen from twelve selected built-in correlations present in the program to predict the pressure drop via gradient matching. A sensitivity analysis of the well was further performed to investigate the parameters such as tubing diameter, gas-oil ratio and wellhead pressure that were affecting the vertical lift performance of a high water cut well. The results obtained from the correlation matching showed that Dun and Ros [2] original correlation was the best fit correlation for the well. The results of the sensitivity analysis revealed that reduction of wellhead pressure from 600 psi to 400 psi could increase liquid rate by 41%. An adjustment of wellhead pressure was found to give the most significant impact on the production rate of the well as compared to other two parameters studied.

Abstract: The application of distributed temperature sensors(DTS) to monitor producing zones ofhorizontal well through a real-time measurement of a temperature profile is becoming increasinglypopular. The information from DTS can potentially be transformed to obtain the permeability alongto the wellbore and well completion method and so on. The relationship between these parametersand the real-time temperature distribution along the wellbore is very important. Based onmass-,momentum-,and energy-balance equations, this paper established a model to predict thetemperature along the horizontal wellbore. The models presented in this paper account for heatconvective, fluid expansion, heat conduction, and viscous dissipative heating. Wellbore temperaturecurves are plotted by computer iterative calculation. In addition, this paper revealed the relationshipbetween wellbore temperature distribution and different characteristics, such as permeability alongto the wellbore and well completion method. The analysis results show that permeability differenceand different well completion methods may lead to different downhole temperature distribution atthe same time step, different production rate, different wellbore temperature as well as the change offriction factor in the wellbore. From the temperature distribution and temperature derivative curvesin different cases, we could easily derive the permeability distribution along wellbore and thelocation of the perforated intervals and the fractures.