Flow-sensitive Analysis Research Articles

Quantitative Analysis of Material Flow of Used Mobile Phones in Japan

Since Japan is importing most of natural resources, reducing amount of material usage is an emerging problem. Plus, reducing environmental impact of product lifecycle is also important. This paper first, illustrated a material flow of used mobile phones with quantitative information. Then, a sensitivity analysis was applied to clarify important factors in reducing material consumption and environmental impact. Result showed that transportation length has a big influence on environmental impact. Thus, an efficient logistics can be a key in reducing environmental impact. The material flow showed that a big portion of used phones are stored in homes. To collect such stored mobile phones, official network called MRN (mobile phone network) is the best strategy in reducing material consumption and avoiding problems regarding outflow. Finally, the paper concluded that sensitivity analysis of material flow is a useful method in determining proper strategy of treatment of used products.

Selective X-Sensitive Analysis Guided by Impact Pre-Analysis

We present a method for selectively applying context-sensitivity during interprocedural program analysis. Our method applies context-sensitivity only when and where doing so is likely to improve the precision that matters for resolving given queries. The idea is to use a pre-analysis to estimate the impact of context-sensitivity on the main analysis’s precision, and to use this information to find out when and where the main analysis should turn on or off its context-sensitivity. We formalize this approach and prove that the analysis always benefits from the pre-analysis--guided context-sensitivity. We implemented this selective method for an existing industrial-strength interval analyzer for full C. The method reduced the number of (false) alarms by 24.4% while increasing the analysis cost by 27.8% on average. The use of the selective method is not limited to context-sensitivity. We demonstrate this generality by following the same principle and developing a selective relational analysis and a selective flow-sensitive analysis. Our experiments show that the method cost-effectively improves the precision in the these analyses as well.

Sensitivity Analysis of Flow and Temperature Distributions of Density Currents in a River-Reservoir System under Upstream Releases with Different Durations

A calibrated three-dimensional Environmental Fluid Dynamics Code model was applied to simulate unsteady flow patterns and temperature distributions in the Bankhead river-reservoir system in Alabama, USA. A series of sensitivity model runs were performed under daily repeated large releases (DRLRs) with different durations (2, 4 and 6 h) from Smith Dam Tailrace (SDT) when other model input variables were kept unchanged. The density currents in the river-reservoir system form at different reaches, are destroyed at upstream locations due to the flow momentum of the releases, and form again due to solar heating. DRLRs (140 m3/s) with longer durations push the bottom cold water further downstream and maintain a cooler bottom water temperature. For the 6-h DRLR, the momentum effect definitely reaches Cordova (~43.7 km from SDT). Positive bottom velocity (density currents moving downstream) is achieved 48.4%, 69.0% and 91.1% of the time with an average velocity of 0.017, 0.042 and 0.053 m/s at Cordova for the 2-h, 4-h and 6-h DRLR, respectively. Results show that DRLRs lasting for at least 4 h maintain lower water temperatures at Cordova. When the 4-h and 6-h DRLRs repeat for more than 6 and 10 days, respectively, bottom temperatures at Cordova become lower than those for the constant small release (2.83 m3/s). These large releases overwhelm the mixing effects due to inflow momentum and maintain temperature stratification at Cordova.

Effects of fluid thermophysical properties on cavitating flows

We studied the thermo-fluid cavitating flows and evaluated the effects of physical properties on cavitation behaviors. The thermo-fluid (including liquid nitrogen, liquid hydrogen and hot water) cavitating flows around a 2D hydrofoil were numerically investigated. The Favre-averaged Navier-Stokes equations with the enthalpy-based energy equation, transport equation-based cavitation model, and the k-ω SST turbulence model were applied. The thermodynamic parameter Σ, defined as \(\sum { = \left( {\rho _v ^2 L^2 } \right)/\left( {\rho _l ^2 C_v T_\infty \sqrt {\varepsilon _l } } \right)} \) was used to assess the thermodynamic effects on cavitating flows. The results manifest that the thermal energy solution case yields a substantially shorter and mushier cavity attached on the hydrofoil due to the thermodynamic effects, which shows better agreement with the experimental data. The temperature drop inside the cavity decreases the local saturated vapor pressure and hence increases the local cavitation number; it could delay or suppress the occurrence and development of the cavitation behavior. The thermodynamic effects can be evaluated by thermophysical properties under the same free-stream conditions; the thermodynamic parameter Σ is shown to be critical in accurately predicting the thermodynamic effects on cavitating flows. The surrogate-based global sensitivity analysis of liquid nitrogen cavitating flow suggests that ρv, Cl and L could significantly influence temperature drop and cavity structure in the existing numerical framework, while ρv plays the dominant role on temperature drop when properties vary with changing temperature. The liquid viscosity µl slightly affects the flow structure but hardly affects the temperature distribution.

Sensitivity analysis of transient flow of two parallel pump-turbines operating at runaway

Transient flow analysis in hydroelectric power plants is one of the most important issues for the prevention of undesirable pressure fluctuations in waterways. In this paper sensitivity analysis of hydraulic transient for two parallel pump-turbine units operating at runaway (unstable S-shaped zone of pump-turbine hill-chart) have been numerically investigated. The characteristics of Siah Bishe power plant located at the north of Iran, has been considered. Firstly, simultaneous operation of two units at runaway is simulated. For this purpose, the governing equations of transient flow are solved along the waterways using the method of characteristics and modified Suter transformations. Then, the sensitivity of pressure rise at the spiral case, water level oscillating at surge tank, rotational speed and flow rate and torque oscillation at unstable zone of hill-chart to moment of inertia, head loss coefficient of connection tunnel of surge tank, connection tunnel diameter and acoustic wave velocity has been performed. The results show that the moment of inertia has considerable effect on the maximum torque at unstable condition of runaway. Also, more moment of inertia can well postpone the peak of pressure and rotational speed. The maximum water level of surge tank and the maximum torque at unstable condition of runaway are strongly affected by head loss coefficient of connection tunnel of surge tank and connection tunnel diameter. By using different values for acoustic wave velocity, output conditions don't show any clear trend.

A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal

Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository.In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository.

Global stability and sensitivity analysis of boundary-layer flows past a hemispherical roughness element

We study the full three-dimensional instability mechanism past a hemispherical roughness element immersed in a laminar Blasius boundary layer. The inherent three-dimensional flow pattern beyond the Hopf bifurcation is characterized by coherent vortical structures usually called hairpin vortices. Direct numerical simulation results are used to analyze the formation and the shedding of hairpin vortices inside the shear layer. The first bifurcation is investigated by global-stability tools. We show the spatial structure of the linear direct and adjoint global eigenmodes of the linearized Navier-Stokes equations and use the structural-sensitivity field to locate the region where the instability mechanism acts. The core of this instability is found to be symmetric and spatially localized in the region immediately downstream of the roughness element. The effect of the variation of the ratio between the obstacle height k and the boundary layer thickness δk∗ is also considered. The resulting bifurcation scenario is found to agree well with previous experimental investigations. A limit regime for k/δk∗<1.5 is attained where the critical Reynolds number is almost constant, Rek ≈ 580. This result indicates that, in these conditions, the only important parameter identifying the bifurcation is the unperturbed (i.e., without the roughness element) velocity slope at the wall.

Social Network based sensitivity analysis for patient flow using computer simulation

Prediction of patient flow, an essential element of any healthcare system, is challenging due to uncertainties in patient volume. One such source of uncertainty is a propagated outbreak of epidemic diseases as they spread through networks of human populations. Till date, no study exists that studied the effect of social network structure on patient flow. In this study, we aim to examine the relationship between patient flow in a social network and the corresponding network characteristics. For this purpose, we developed a simulation model in which an epidemic spreads through a social network and then the generated patients are directed to a healthcare system. To quantify the patient flow, we considered the conditional expected value of the length of stay (LoS) as our performance measure. The network characteristics considered were average distance, closeness centralization, betweenness centralization, and eigenvector centralization. Results from this study indicate that the patient flow has a direct relationship with closeness centralization and an inverse relationship with average distance. Betweenness and eigenvector centralization did not provide any meaningful information in patient flow prediction. Overall, patient flow is more sensitive to average distance. This work helps healthcare planners and decision makers in better prediction of the patient flow during a propagated outbreak of an epidemic.

CFD studies of the propagation and extinction of flame in an under-ventilated and over-ventilated enclosure

This piece of work is a contribution to the model-building and numerical simulation of fire phenomenon concerning fire outbreak, in confined enclosures. The numerical tool that has been used is the industrial Computational Fluid Dynamics (CFD) code called Fire Dynamics Simulator (FDS), in its 5.5.3 version. The chosen configuration of Foote and Chen et al. has allowed us to evidence the ventilation phenomena. The results of calculations that we carried out under over-ventilation conditions were satisfactory. A gap is nevertheless observed between calculations and measurements when the measurement point is located close to the air inlet duct. In under-ventilated conditions, the results are equally satisfactory, but appear to require heat flow sensitivity analysis to be excellent.

Analytical sensitivity analysis of transient groundwater flow in a bounded model domain using the adjoint method

AbstractSensitivity analyses are an important component of any modeling exercise. We have developed an analytical methodology based on the adjoint method to compute sensitivities of a state variable (hydraulic head) to model parameters (hydraulic conductivity and storage coefficient) for transient groundwater flow in a confined and randomly heterogeneous aquifer under ambient and pumping conditions. For a special case of two‐dimensional rectangular domains, these sensitivities are represented in terms of the problem configuration (the domain size, boundary configuration, medium properties, pumping schedules and rates, and observation locations and times), and there is no need to actually solve the adjoint equations. As an example, we present analyses of the obtained solution for typical groundwater flow conditions. Analytical solutions allow us to calculate sensitivities efficiently, which can be useful for model‐based analyses such as parameter estimation, data‐worth evaluation, and optimal experimental design related to sampling frequency and locations of observation wells. The analytical approach is not limited to groundwater applications but can be extended to any other mathematical problem with similar governing equations and under similar conceptual conditions.

An Investigation on the Role of NO2 in the Oxidation of Methane to Formaldehyde

Experimental results and a kinetic modeling were previously reported for the gas phase oxidation of methane in the presence of NO2 at short residence time (20–80 ms) in a microreactor. A detailed kinetic analysis is carried out in the present study in means of flow rate and sensitivity analysis, in order to investigate the role of NO2. A comparison is made of the reaction systems with and without NO2. The concentration profiles of several key species are presented and analyzed in the present study. The CH3O· radicals are present in far larger quantities in the CH4/O2/NO2 system than in the CH4/O2 system. With NO2, the dominant route to HCHO is through CH3O·, primarily involving the reaction: CH3· + NO2 ⇔ CH3O· + NO, followed by: CH3O· (+M) ⇔ CH2O + H· (+M) and CH3O· + O2 ⇔ HO2· + CH2O. The promoting effects of NO2 can be explained by the interconversion NO2/NO, which is mainly related to: HO2· + NO ⇔ NO2 + OH·, NO2 + H· ⇔ NO + OH·, NO + CH3O2· ⇔ CH3O· + NO2 and NO2 + CH3· ⇔ CH3O· + NO.

A multi-methodological approach for assessing sustainability of urban projects

Purpose – The purpose of this paper is to propose a multi-methodological approach for assessing the sustainability of urban projects. The proposed framework has the objective of addressing the different dimensions involved in the analysis (economic, environmental, social, technological, cultural, etc.), following the subsequent phases for the definition of the projects (from a very general masterplan to more detailed preliminary projects). Design/methodology/approach – The multi-methodological approach is organized according to subsequent steps, involving the application of different evaluation methods, namely SWOT analysis, multicriteria analysis, discounted cash flow analysis and sensitivity analysis. With the aim of better illustrating the proposed approach, the method is applied on a real case concerning the project of a new boulevard in the city of Skopje. Findings – The proposed approach resulted to be successful in structuring the complex planning context and in increasing and improving the information for the project, thus acting as a learning process. Originality/value – The paper is based on the experimentation of an hybrid approach for addressing planning process. The multi-methodological framework can be useful in supporting decision making process in the domain of urban projects. In this sense, the proposed framework is able to communicate the planners’, designers’ and decision maker’s perspectives, to enhance transparency in the decision process and thus to increase acceptance.

Extraction of macroscopic and microscopic adjoint concepts using a lattice Boltzmann method and discrete adjoint approach.

In the present research, we tried to improve the performance of the lattice Boltzmann (LB) -based adjoint approach by utilizing the mesoscopic inherent of the LB method. In this regard, two macroscopic discrete adjoint (MADA) and microscopic discrete adjoint (MIDA) approaches are used to answer the following two challenging questions. Is it possible to extend the concept of the macroscopic and microscopic variables of the flow field to the corresponding adjoint ones? Further, similar to the conservative laws in the LB method, is it possible to find the comparable conservation equations in the adjoint approach? If so, then a definite framework, similar to that used in the flow solution by the LB method, can be employed in the flow sensitivity analysis by the MIDA approach. This achievement can decrease the implementation cost and coding efforts of the MIDA method in complicated sensitivity analysis problems. First, the MADA and MIDA equations are extracted based on the LB method using the duality viewpoint. Meanwhile, using an elementary case, inverse design of a two-dimensional unsteady Poiseuille flow in a periodic channel with constant body forces, the procedure of analytical evaluation of the adjoint variables is described. The numerical results show that similar correlations between the distribution functions can be seen between the corresponding adjoint ones. Besides, the results are promising, emphasizing the flow field adjoint variables can be evaluated via the adjoint distribution functions. Finally, the adjoint conservative laws are introduced.

Sensitivity analysis of a GIS-based model: A case study of a large semi-arid catchment

Water resource and hydrologic modeling studies are intrinsically related to spatial processes of hydrologic cycle. Due to generally sparse data, and high rainfall variability, the accurate prediction of water availability in complex semi-arid catchment depends to a great extent on how well spatial input data describe realistically the relevant characteristics. The Geographic Information System (GIS) provides the framework within which spatially distributed data are collected and used to prepare model input files. Despite significant recent developments in distributed hydrologic modeling, the over-parameterization is usually a critical issue that can complicate calibration process. Sensitivity analysis methods reducing the number of parameters to be adjusted during calibration are important for simplifying the use of these models. The objective of this paper is to perform a sensitivity analysis for flow in a semi-arid catchment (1,491 km2), located in northwestern of Tunisia, using the Soil and Water Assessment Tool (SWAT) model. The simulation results revealed that among eight selected parameters, curve number (CN2), soil evaporation compensation factor (ESCO), soil available water capacity (SOL_AWC) and threshold depth of water in the shallow aquifer required for return flow (GWQMN) were found to be the most sensitive parameters. Calibration of hydrology, facilitated by the sensitivity analysis, was performed for the period 2001 through 2003. Results of calibration showed that the model accurately predict runoff and performed well with a monthly Nash Sutcliffe efficiency (NSE) of 0,78, a coefficient of determination (R2) of 0,85 and a percent of bias (PBIAS) equal to −13,22 %.

Sensitivity analysis of transonic flow past a NASA airfoil/wing with spoiler deployments

Transonic flow past a NASA SC(2)-0710 airfoil with deployments of a spoiler up to 6° was studied numerically. We consider angles of attack from -0.6° to 0.6° and free-stream Mach numbers from 0.81 to 0.86. Solutions of the unsteady Reynoldsaveraged Navier-Stokes equations were obtained with a finite-volume solver using several turbulence models. Both stationary and time-dependent deployments of the spoiler were examined. The study revealed the existence of narrow bands of the Mach number, angle of attack, and spoiler deflection angle, in which the flow was extremely sensitive to small perturbations. Simulations of 3D flow past a swept wing confirmed the flow sensitivity to small perturbations of boundary conditions.

Setting Conditions of Long and Short Routing Mode of Rail Transit

This paper analyzes the setting conditions on long and short routing mode of urban rail transit both qualitatively and quantitatively. The extended routing and the nested routing are selected to establish the evaluation system of train routing operation effect. Based on the sensitivity analysis of passenger flow and comparison of the operation effects of the train routing above, a conclusion when it is necessary to set long and short routing mode is drew. The instance of Metro Line 3 of City B verificates the method above and it is found the advantage of setting long and short routing mode is smaller as the passenger flow becomes balanced.

Decision Making Using Engineering Economic Tools: A Real Case Study

Appropriate financial decisions are important for success of any company. Sometimes, erroneous selection of project or investment ruins the overall company’s financial condition. There are number of financial or engineering economic tools available but the appropriateness of a given project, estimate its value, and justify it from an engineering economics standpoint is the key. It’s known that engineering economics provides the tools and techniques in evaluating alternatives economically and source of many engineering decisions are based on engineering economics. In this paper, we will make economics decision for the location of copper mining plant using traditional engineering economics tools like cash flow, depreciation, and spider diagram and sensitivity analysis by using a real case study.

Pyrolysis of propane for CVI of pyrocarbon. Part IV: Main pathways involved in pyrocarbon deposit

A detailed kinetic mechanism modeling both gas and surface reactions involved in chemical vapor deposition (CVD) of pyrocarbon has been developed. Simulated results have been validated by comparison with experimental data. Pyrolytic carbon deposit was realized on carbon fibers by the pyrolysis of propane at low pressure (<3kPa) and high temperature (≈1200K). The kinetic mechanism consists in 608 gaseous and 275 surface elementary steps, and is efficient to predict both pyrocarbon deposit rate and gas phase composition vs. temperatures, residence time ranging and fibers surface to reactant volume ratio. In this paper, the main pyrocarbon deposition pathways are proposed by using flow rate and sensitivity analyses. In our experimental conditions, pyrocarbon seems to be mainly formed by the deposition of small unsaturated species (such as acetylene and ethylene) and methyl radicals. Pyrocarbon deposition rate is controlled by the gas phase composition (H2, CH3, C2H2 and C2H4) and a few surface key reactions.

Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution

Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs (m1), and tracer cumulative mass discharge (Md) through control planes combined with hydraulic head observations (h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling.

Comparison of Performance Losses Between Ultrasonic and Thermal Bonding of Membrane Electrode Assemblies in Proton Exchange Membrane Fuel Cells

Ultrasonic bonding of low-temperature PEM membrane electrode assembly (MEA) components together has been shown previously to cut both cycle time and energy input of that manufacturing step by over an order of magnitude as compared to the industry standard of thermal pressing. This paper compares performance between ultrasonically and thermally bonded low-temperature MEAs and characterizes the performance losses from the new bonding process. A randomized, full factorial experiment was designed and conducted to examine performance of MEAs with 10 cm2 active area while varying three factors: bonding method (ultrasonically and thermally pressed using previously optimized bonding parameters), membrane condition (dry and conditioned Nafion® 115), and electrode catalyst loading (0.16 and 0.33 mg Pt/cm2). Ultrasonic MEAs performed as well as their thermal MEAs across all tested current densities with pure oxygen supplied to the cathode. However, thermal MEAs outperformed ultrasonic MEAs at current densities above 0.4 A/cm2 with air supplied to the cathode. Impedance spectroscopy, cyclic voltammetry, and flow sensitivity analyses were used to characterize the performance losses of the ultrasonic MEAs. The data suggest the presence of oxygen diffusion losses above 0.4 A/cm2 when air was supplied to the cathode. Ultrasonic MEAs were three times more sensitive to changes in air flow rate on the cathode than the thermally MEAs. Increasing the platinum catalyst loading from 0.16 to 0.33 mg Pt/cm2 resulted in a performance enhancement of approximately 20 mV and 65% greater electrochemical surface area. Understanding the effect of ultrasonic bonding on various performance losses will help optimize the MEA bonding process. Analysis of specific losses present for ultrasonic MEAs may also provide insight into the design of MEA components for ultrasonic bonding.