Numerical Performance Assessment Research Articles

Experimental and Numerical Performance Assessment of East-West Bifacial Photovoltaic Floating System in Freshwater Basins

Experimental and Numerical Performance Assessment of East-West Bifacial Photovoltaic Floating System in Freshwater Basins

Model averaged tail area confidence intervals in nested linear regression models

SummaryThe performance, in terms of coverage and expected length, of the model averaged tail area (MATA) confidence interval, proposed by Turek & Fletcher (2012, Computational Statistics & Data Analysis, 56, 2809–2815), depends greatly on the data‐based model weights used in its construction. We generalise the computationally convenient exact formulae due to Kabaila, Welsh & Abeysekera (2016, Scandinavian Journal of Statistics, 43, 35–48) for the coverage and expected length of this confidence interval for two nested linear regression models to the case of two or more nested linear regression models. This permits the numerical assessment of the performance, in terms of coverage probability and scaled expected length, of the MATA confidence interval for any given data‐based model weights in the context of three or more nested linear regression models. We illustrate this numerical assessment of performance of the MATA confidence interval, for model weights based on any given Generalised Information Criterion, in the context of three nested linear regression models using the real life ‘Cholesterol’ data. This provides a very informative further exploration of the influence of these model weights on the performance of this confidence interval.

CFD Based Numerical Performance Assessment of a Solar Air Heater Duct Roughened by Transverse - Trapezoidal Sectioned Ribs

CFD Based Numerical Performance Assessment of a Solar Air Heater Duct Roughened by Transverse - Trapezoidal Sectioned Ribs

Numerical performance assessment of a new wave energy conversion system

The greater wave energy content in deeper waters has initiated substantial research in offshore wave energy converters (WECs). However, the existing WECs are hindered by their high initial costs, primarily attributed to the demanding mechanical workloads they endure. This paper describes a novel wave energy conversion system developed at IST for deep waters (around 20-50 meters) based on a floater and a ballast, suspended by a set of cables. In the novel approach, the WEC is made up essentially by membranes, without a rigid structure, thus reducing the initial cost of investment comparing to other solutions.A simplified numerical model in the time-domain of the system based on linear theory is developed and a preliminary performance assessment under regular and irregular wave conditions (for conditions prevalent along the western coast of Portugal) is performed. Additionally, the effect of the ballast mass is considered. The results reveal the system's non-linear behavior during the floater's ascending phase and emphasize the significant influence of the ballast's mass on power production.

Assessment of Small Diameter Steel Pile as a Stabilizing Element for Transmission Tower Slope Stability

Background: Stabilization of unstable slopes with relatively large reinforced concrete piles has been widely adopted over the past several decades. Small diameter steel piles have several advantages as a slope reinforcement technique for an unstable transmission tower slope where space and access restrictions that typically occur render alternate approaches unfeasible. Methods: In this study, a numerical performance assessment of small diameter steel pile as a stabilizing element for transmission tower slope stability was carried out using an uncoupled analysis, in which the pile response and slope stability are considered separately. Numerical evaluations are presented and the influencing parameters that could affect the behavior of reinforcing piles to increase transmission tower slope stability are investigated. Results: The numerical analysis results indicate that the soil properties, slope geometry, pile location, pile diameter, pile length and number of pile rows have a combined effect on the performance of small diameter steel piles to stabilize transmission tower slopes. Conclusion: The numerical assessment can satisfactorily capture some fundamental response of transmission tower slope reinforced with multi-row small diameter steel piles.

Experimental and numerical performance assessment of a hybrid parabolic dish collector with photovoltaic for a distiller

ABSTRACT Environmental pollution has been rising recently, and so clean water needing has also increased. People could have easy access to pure water in all environments and conditions. This study is the solar tracking parabolic dish collector with produced pure water independent of electricity (off-grid). This system is fully renewable and autonomous. This system possesses a receiver, a boiler, a condenser, six 1000 mm diameter parabolic dish collectors, and 1 kW photovoltaic (PV) collectors. Thermal oil uses as the working fluid in the experiments. The experiment measured solar radiation, air temperature, air velocity, oil inlet and outlet temperatures, oil flow rate, receiver side surface temperatures, and instantaneous amount of pure water. Numerical and thermal analysis of the receiver in the experimental setup carry out. ANSYS Fluent 18.1 uses for numerical analysis. Energy and exergy analysis calculates the receiver for pure water production rate. The time interval when the system operates at high performance determines. In this study investigates the behavior of some exergetic indicators on the performance of the experimental setup, the cost of the experimental setup, and the enviro-economic impact of the parabolic dish-type collector. For this purpose, some exergetic factors such as the exergy effect, environmental impact factor, waste exergy rate, improvement potential, and exergetic sustainability index examine. The receiver’s improvement potential is between 1700 and 3000 W. In addition, the sustainability index, waste exergy rate, and environmental impact factor range from 0.32 to 0.36, 0.90 to 0.94, and 2.6 to 3.0, respectively.

Numerical performance assessment of double-shell targets for Z-pinch dynamic hohlraum

A Z-pinch dynamic hohlraum can create the high-temperature radiation field required by indirect-drive inertial confinement fusion. A dynamic hohlraum with peak radiation temperature over 300 eV can be obtained with a >50 MA Z-pinch driver according to the scaling law of dynamic hohlraum radiation temperature vs drive current. Based on a uniform 300 eV radiation temperature profile with a width of 10 ns, three double-shell capsules with radii of 2, 2.5, and 3 mm are proposed, and the corresponding fusion yields from a one-dimensional calculation are 28.8, 56.1, and 101.6 MJ. The implosion dynamics of the 2.5 mm-radius capsule is investigated in detail. At ignition, the areal density of the fuel is about 0.53 g/cm2, the fuel pressure is about 80 Gbar, and the central ion temperature is about 4.5 keV, according to the one-dimensional simulation. A two-dimensional simulation indicates that the double-shell capsule can implode nearly spherically when driven by the radiation field of a Z-pinch dynamic hohlraum. The sensitivities of the fusion performance to the radiation temperature profiles and to deviations in the capsule parameter are investigated through one-dimensional simulation, and it is found that the capsule fusion yields are rather stable in a quite large parameter space. A one-dimensional simulation of a capsule embedded in 50 mg/cm3 CH foam indicates that the capsule performance does not change greatly in the mimicked environment of a Z-pinch dynamic hohlraum. The double-shell capsules designed here are also applicable to laser indirect-drive inertial fusion, if a laser facility can produce a uniform 300 eV radiation field and sustain it for about 10 ns.

Numerical performance assessment of a solar greenhouse dryer for the drying of Olive Mill Wastewater

Numerical performance assessment of a solar greenhouse dryer for the drying of Olive Mill Wastewater

Experimental and numerical performance assessment of square aluminum and steel energy absorbers with circular hole discontinuities

This work reports the performance of energy absorbers made in mild-steel and aluminum thin-walled square tubes under quasi-static compression tests. They have circular holes discontinuities laterally drilled on two or four opposing faces of the tube, according to three different distances based on the effective crushing distance, resulting in 23, 36, and 46 mm, as well as two diameters 8 and 12 mm. The tubes are 300 mm in effective length, 50 mm wide, and thickness varies. A substantial variation at performance parameters occurs with wall thickness and material changes. Failure initiators with 12 mm in diameter distant from each other 23 and 36 mm lead to better performance for aluminum and steel absorbers, respectively. Von Mises equivalent stress reaffirms that failure initiator influences stress distribution; consequently, the deformation process and; eigenvalue buckling analysis highlights the relation of buckling effect with the peak force and the stiffness of the tube face.

Numerical performance assessment of Tuned Mass Dampers tomitigate traffic-induced vibrations of a steel box-girder bridge

In this paper, the effects of Tuned Mass dampers (TMDs) on the reduction of the vertical vibrations of a real horizontally curved steel box-girder bridge due to different traffic loads are numerically investigated. The performance of TMDs to reduce the bridge vibrations can be affected by the parameters such as dynamic characteristics of TMDs, the location of TMDs, the speed and weight of vehicles. In the first part of this study, the effects of mass ratio, damping percentage, frequency ratio, and location of TMDs on the performance of TMDs to decrease vertical vibrations of different sections of bridge deck are evaluated. In the second part, the performance of TMD is investigated for different speeds and weights of traffic loads. Results show that the mass ratio of TMDs is the more effective parameter in reducing imposed vertical vibration in comparison with the damping ratio. Furthermore, it is found that TMD is very sensitive to its tuned frequency, i.e., with a little deviation from a suitable frequency, the expected performance of TMD significantly decreased. TMDs have a positive and considerable performance at certain vehicle speeds and this performance declines when the weight of traffic loads is increased. Besides, the results reveal that the highest impact of TMD on the reduction of the vertical vibrations is when free vibrations occur for the bridge deck. In that case, maximum reductions of 24% and 59% are reported in the vertical acceleration of the bridge deck for the forced and free vibration amplitudes, respectively. The maximum reduction of 13% is also obtained for the maximum displacement of the bridge deck. The results are mainly related to the resonance condition.

Numerical performance assessment of a novel Darrieus-style VAWT with auxiliary straight blades

Domestic Vertical Axis Wind Turbines (VAWT) are able to operate also when the wind speed is low and can be installed in the open spaces of housing areas. The Darrieus turbine is the most promising since it is characterized by higher efficiency, even if for applications at higher wind speeds with respect to Savonius VAWTs. Several researchers try to optimize the aerodynamics of the Darrieus rotors, allowing wind turbines to start rotation even in the presence of low wind speeds. In this paper the authors propose a numerical investigation of the flow field around a 1:4 scaled model of a pair of blades installed on an innovative Darrieus-type VAWT. A Reynolds Averaged Navier-Stokes-based CFD model was validated on the basis of the wind tunnel data, and the scaled turbine performance was analysed by numerically evaluating the effect of different geometric configurations and rotation angles on the turbine torque coefficients. The results of the simulations confirmed the capabilities of the proposed configuration to give valuable performance even for low wind speeds.

Numerical performance assessment of buried corrugated metal culvert subject to service load conditions

Two- and three-dimensional continuum finite element methods were used to assess the mechanical response of buried metal culverts subjected to service load conditions. The analysis explored the influence of the culvert profile, cover depth, section aspect ratio, and service load magnitude on culvert deformation, thrust, and section moment response. The numerical predictions were calibrated using third-party experimental data. For shallow burial conditions, the culvert section profile was found to be an influential parameter on the predicted culvert response where the soil–culvert interaction mechanisms and load transfer processes are governed by nonlinear behaviour. Models that incorporate the corrugated culvert profile provided better estimates of the culvert thrust than the simplified computational models that are typically used in analysis. Results from this study demonstrate that existing simplified methods cannot capture the local variation (i.e., amplitude, waveform) of the membrane strain and section thrust particularly between the crest and trough of corrugation.

Numerical performance assessment of slope reinforcement using a pile-anchor structure under seismic loading

The pile-anchor structure is one of the most commonly used and effective methods in slope treatment. However, the dynamic behavior of slope reinforcement using a pile-anchor structure remains poorly understood. Performance assessment of the reinforcement system under seismic loading is therefore critical for reinforcement design. In this study, a numerical model of slope reinforced by pile-anchor structure, together with the analysis procedure, is briefly discussed. We consider four different reinforcement schemes to examine the effectiveness of pile-anchor reinforcement under seismic loading. Finite element analysis is used to derive the dynamic response, and Newmark sliding block analysis is employed to examine the stability of the reinforced slope. The performance assessment results indicate that the pile-anchor structure presents significant advantages of slope deformation reduction with a more reasonable internal force distribution and increased slope stability.

Up-scaling transport in porous polymer membranes using asymptotic homogenization

PurposeEfficient numerical assessment of performance is particularly important in digital material design of porous materials. This study aims to present an up-scaled approach to virtually investigate permeation of fluids through a real porous filter membrane with a heterogeneous micro-structure.Design/methodology/approachThe method of asymptotic homogenization is applied. The structural parameters of the micro-structure are directly obtained from structural equation modeling image analysis of a commercial filter membrane without fitting procedures. The simulation results are compared to permeation experiments of gaseous nitrogen and liquid water.FindingsThe authors found that variations in the pressure gradients across the membrane, resulting from the heterogeneity of pore structure, need to be considered. Remarkable agreement between simulations and experiments is observed.Originality/valueDespite some research in the field of filtration, no studies on filter membranes have been published yet, although they represent a large segment of filtration technology.

Numerical performance assessment of an innovative Darrieus-style vertical axis wind turbine with auxiliary straight blades

Vertical axis wind turbines (VAWTs) are receiving growing interest for small scale power generation at low wind speed condition, in particular for off-grid, home applications. VAWTs are mainly composed of two typologies: drag-based Savonius, and lift-based Darrieus turbines. Between the two, the Darrieus turbine is the most promising since it is characterized by higher efficiency, even if for applications at higher wind speeds with respect to Savonius VAWTs. A lot of research is made in order to enhance the aerodynamics of the Darrieus rotors, making them applicable for lower wind speeds without significantly affecting efficiency. One of the developments of standard Darrieus configuration is proposed in our previous paper, adopting three couples of blades for the rotor, each composed by a main and an auxiliary aerofoil. A scaled model of such rotor configuration is tested in the wind tunnel available at the Department of Civil and Mechanical Engineering (DICEM) of the University of Cassino, showing good performances in terms of power and torque coefficients, especially at the lower wind speeds. In the present paper, a Reynolds Averaged Navier-Stokes-based CFD model is used in order to investigate the performance of an innovative, real scale double-bladed wind turbine. The CFD model is validated on the basis of the wind tunnel data, and the real scale wind turbine performance is analysed by numerically evaluating the power and torque coefficients. The results of the simulations confirm the capabilities of the proposed configuration to give valuable performance even for wind speeds below 4 m·s-1.

A numerical performance assessment of a commercial cardiopulmonary by-pass blood heat exchanger

We developed a numerical model, based on multi-physics computational fluid dynamics (CFD) simulations, to assist the design process of a plastic hollow-fiber bundle blood heat exchanger (BHE) integrated within the INSPIRETM, a blood oxygenator (OXY) for cardiopulmonary by-pass procedures, recently released by Sorin Group Italia. In a comparative study, we analyzed five different geometrical design solutions of the BHE module. Quantitative geometrical-dependent parameters providing a comprehensive evaluation of both the hemo- and thermo-dynamics performance of the device were extracted to identify the best-performing prototypical solution. A convenient design configuration was identified, characterized by (i) a uniform blood flow pattern within the fiber bundle, preventing blood flow shunting and the onset of stagnation/recirculation areas and/or high velocity pathways, (ii) an enhanced blood heating efficiency, and (iii) a reduced blood pressure drop. The selected design configuration was then prototyped and tested to experimentally characterize the device performance. Experimental results confirmed numerical predictions, proving the effectiveness of CFD modeling as a reliable tool for in silico identification of suitable working conditions of blood handling medical devices. Notably, the numerical approach limited the need for extensive prototyping, thus reducing the corresponding machinery costs and time-to-market.

A newly developed rotor profile for lobe pumps: Generation and numerical performance assessment

This study develops a new lobe pump rotor profile that significantly improves pump performance. Rotor profiles including two traditional designs and two new designs consist of three segments that are generated by circular or/and epicycloidal curves. This study evaluates the performance of four profiles via volume calculation and flow field analysis, considering to the number of lobes. Results demonstrate that the shapes of rotor surfaces affect pump performance remarkably. An epicycloidal profile provides a much advantage than a circular profile. The new rotor profile with three segments was generated by the curves in order of epicycloidal-circular-epicycloidal (ECE profile) obtained performance of 55% higher than the traditional profiles and the order of circular-epicycloid-circular (CEC profile). The analysis in this study also proves that a multi-lobe design of three or four lobes does not increase pump performance, but provides a more stable output and higher capacity than a two-lobe pump.

Performance of structure–equipment systems with a novel roll-n-cage isolation bearing

In this the paper, the problem of mitigating the seismic response of sensitive equipments housed in building structures is addressed by isolating the structure with an innovative device referred to as roll-n-cage isolator. The device is described, characterized and represented by a hysteretic semi-physical mathematical model. A numerical performance assessment is performed by implementing the isolator in a building structure housing equipment in upper floors where accelerations are amplified and motions contain strong components at long periods. The numerical results show that the proposed isolator is efficient in substantially attenuating the structure-equipment response under a wide variety of actual earthquakes while exhibiting robust performance for a wide range of structures.

Noncoherent space-frequency coded MIMO-OFDM

Recently, the use of coherent space-frequency coding in orthogonal frequency-division multiplexing (OFDM)-based frequency-selective multiple-input multiple-output (MIMO) fading channels has been proposed. Acquiring knowledge of the fading coefficients in a MIMO channel is already very challenging in the frequency-flat (fast) fading case. In the frequency-selective case, this task becomes significantly more difficult due to the presence of multiple paths, which results in an increased number of parameters to be estimated. In this paper, we address code design for noncoherent frequency-selective MIMO-OFDM fading links, where neither the transmitter nor the receiver knows the channel. We derive the code design criteria, quantify the maximum achievable diversity gain, and provide explicit constructions of full-diversity (space and frequency) achieving codes along with an analytical and numerical performance assessment. We also demonstrate that unlike in the coherent case, noncoherent space-frequency codes designed to achieve full spatial diversity in the frequency-flat fading case can fail completely to exploit not only frequency diversity but also spatial diversity when used in frequency-selective fading environments. We term such codes catastrophic..