Computational Fluid Dynamics Modeling Approach Research Articles

A Practical Approach for Biochemical Modeling in the CFD Evaluation of Novel Anaerobic Digester Concepts for Biogas Production

The detailed physics-based description of anaerobic digesters is characterized by their multiscale and multiphysics nature, with Computational Fluid Dynamics (CFD) simulations being the most comprehensive approach. In practice, difficulties in obtaining a detailed characterization of the involved biochemical reactions hinder its application in the design of novel reactor concepts, where all physics interplays in the reactor must be considered. To solve this limitation, a practical approach is introduced where a calibration step using actual process data was applied for the simplified biochemical reactions involved, allowing us to efficiently manage uncertainties arising when characterizing biochemical reactions with lab scale facilities. A complete CFD modeling approach is proposed for the anaerobic digestion of wastewater, including heat transfer and multiphasic flow. The proposed multiphase model was verified using reference data and, jointly with the biochemical modeling approach, applied to a lab-scale non-conventional anaerobic digester for winery wastewater treatment. The results showed qualitative improvement in predicting methane production when the diameter of the particles was reduced, since larger particles tend to move downwards. The biochemistry of the process could be simplified introducing a preexponential factor of 380 (kmol/m3)(1 – n)/s for each considered chemical reaction. In general, the proposed approach can be used to overcome limitations when using CFD to scale-up optimization of non-conventional reactors involving biochemical reactions.

A CFD Modelling Approach of Fuel Spray under Initial Non-Reactive Conditions in an Optical Engine

A better understanding of why and how pollutant emissions from compression ignition engines are produced is one of the strategies to reduce them, and to achieve this it is important to understand what happens in the fuel injection inside the combustion chamber and in the combustion process. Experimentally, it is difficult to analyse the fuel spray right at the initial moments when it enters the combustion chamber due to its high velocity. These initial moments of the fuel spray affect its complete development and, consequently, the combustion process inside the chamber. This fact has motivated the approach of this work, in which a parametric study of the spray penetration as a function of variables that can be measured has been proposed. The purpose of this model is to understand which variables of the injection system significantly affect the spray penetration in the initial instants and how they affect it. This study was carried out using diesel and serves as a reference framework for similar studies using pure or blended sustainable advanced fuels. A computational fluid dynamics (CFD) model that determines the spray penetration at initial instants under different injection pressures and nozzle hole diameters is presented in this work. To tune the model, experiments were carried out on an optical engine. The modelled and experimental results exceed 94.8% agreement in all cases studied.

A Critical Review of CFD Modeling Approaches for Darrieus Turbines: Assessing Discrepancies in Power Coefficient Estimation and Wake Vortex Development

This critical review delves into the impact of Computational Fluid Dynamics (CFD) modeling techniques, specifically 2D, 2.5D, and 3D simulations, on the performance and vortex dynamics of Darrieus turbines. The central aim is to dissect the disparities apparent in numerical outcomes derived from these simulation methodologies when assessing the power coefficient (Cp) within a defined velocity ratio (λ) range. The examination delves into the prevalent turbulence models shaping Cp values, and offers insightful visual aids to expound upon their influence. Furthermore, the review underscores the predominant rationale behind the adoption of 2D CFD modeling, attributed to its computationally efficient nature vis-à-vis the more intricate 2.5D or 3D approaches, particularly when gauging the turbine’s performance within the designated λ realm. Moreover, the study meticulously curates a compendium of findings from an expansive collection of over 250 published articles. These findings encapsulate the evolution of pivotal parameters, including Cp, moment coefficient (Cm), lift coefficient (Cl), and drag coefficient (Cd), as well as the intricate portrayal of velocity contours, pressure distributions, vorticity patterns, turbulent kinetic energy dynamics, streamlines, and Q-criterion analyses of vorticity. An additional focal point of the review revolves around the discernment of executing 2D parametric investigations to optimize Darrieus turbine efficacy. This practice persists despite the emergence of turbulent flow structures induced by geometric modifications. Notably, the limitations inherent to the 2D methodology are vividly exemplified through compelling CFD contour representations interspersed throughout the review. Vitally, the review underscores that gauging the accuracy and validation of CFD models based solely on the comparison of Cp values against experimental data falls short. Instead, the validation of CFD models rests on time-averaged Cp values, thereby underscoring the need to account for the intricate vortex patterns in the turbine’s wake—a facet that diverges significantly between 2D and 3D simulations. In a bid to showcase the extant disparities in CFD modeling of Darrieus turbine behavior and facilitate the selection of the most judicious CFD modeling approach, the review diligently presents and appraises outcomes from diverse research endeavors published across esteemed scientific journals.

A Computational Fluid Dynamics Modelling Approach for the Numerical Verification of the Bioclimatic Design of a Public Urban Area in Greece

Recent recordings of urban overheating reveal a dramatic increase in cities’ population exposure to heatwaves. Heatwaves’ implications are escalated in urban environments due to the intensification of the Urban Heat Island (UHI) effect. To combat the overheating and UHI adverse effects, novel urban rehabilitation actions are needed based on reliable predictions of appropriate Key Performance Indicators (KPIs) (such as pedestrian-level air temperature and thermal comfort) for alternative design scenarios. The objective of the current study is to present the application of a previously developed Computational Fluid Dynamics (CFD) model for the calculation of urban microclimatic conditions for the assessment of the UHI and thermal-comfort conditions in a central urban area in the city of Heraklion in Crete, Greece. Empirical validation of the model is performed through comparisons with monitored microclimate data (i.e., air temperature, relative humidity, wind speed) and actual sensation vote recordings found in another research study. In compliance with the latter, the validation campaign is conducted for a typical hot summer day in July 2009 from 10:00 to 16:00. The model is then used to assess the UHI effects for both the existing urban configuration and a given suggested environmental upgrade of the space. Simulations of the existing situation reveal that the squares located in the studied area already stand for efficient resistances to urban overheating, and heat vulnerabilities are detected mainly in non-shaded traffic and pedestrian roads perimetric to the squares. Based on the CFD simulations, the suggested environmental upgrading plan exhibits a reduction in the peak mean air temperature of 0.46 °C, and thermal comfort is improved by at least 5% (based on SET) throughout the studied area in summer. At the same time, simulations of winter conditions suggest that there are limited potential pedestrian thermal-sensation and building heating penalties under the considered renovation scenario.

A CFD Modelling Approach for the Operation Analysis of an Exhaust Backpressure Valve Used in a Euro 6 Diesel Engine

Harvesting residual thermal energy from exhaust gases with thermoelectric generators is one of the paths that are currently being explored to achieve more sustainable and environmentally friendly means of transport. In some cases, thermoelectric generators are installed in a by-pass configuration to regulate the mass flow entering the thermoelectric generator. Some manufacturers are using throttle valves with electromechanical actuators and electronic control in the exhaust pipe to improve techniques for active control of pollutant emissions in reciprocating internal combustion engines, such as the exhaust gas recirculation. The above-mentioned circumstances have motivated the approach of this work: computational fluid dynamics (CFD) modelling of the operation of a throttle valve used for establishing adequate exhaust backpressure conditions to achieve the low pressure exhaust gas recirculation in Euro 6 engines. The aim of this model is to understand the flow control process with these types of valves in order to incorporate them in an exhaust system that will include two thermoelectric generators used to convert residual thermal energy into electrical energy. This work presents a computational model of the flow through the throttle valve under different temperatures and mass flow rates of the exhaust gas with different closing positions. For all cases, the values of the pressure drop were obtained. In all cases studied, the level of agreement between the modelled and experimental results exceeds 90%. The developed model has helped to propose a correlation to estimate the mass flow rate of exhaust gas from easily measurable quantities.

A Hybrid Particle-Flow CFD Modeling Approach in Truncated Hepatic Arterial Trees for Liver Radioembolization: A Patient-specific Case Study.

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. At its intermediate, unresectable stage, HCC is typically treated by local injection of embolizing microspheres in the hepatic arteries to selectively damage tumor tissue. Interestingly, computational fluid dynamics (CFD) has been applied increasingly to elucidate the impact of clinically variable parameters, such as injection location, on the downstream particle distribution. This study aims to reduce the computational cost of such CFD approaches by introducing a novel truncation algorithm to simplify hepatic arterial trees, and a hybrid particle-flow modeling approach which only models particles in the first few bifurcations. A patient-specific hepatic arterial geometry was pruned at three different levels, resulting in three trees: Geometry 1 (48 outlets), Geometry 2 (38 outlets), and Geometry 3 (17 outlets). In each geometry, 1 planar injection and 3 catheter injections (each with different tip locations) were performed. For the truncated geometries, it was assumed that, downstream of the truncated outlets, particles distributed themselves proportional to the blood flow. This allowed to compare the particle distribution in all 48 “outlets” for each geometry. For the planar injections, the median difference in outlet-specific particle distribution between Geometry 1 and 3 was 0.21%; while the median difference between outlet-specific flow and particle distribution in Geometry 1 was 0.40%. Comparing catheter injections, the maximum median difference in particle distribution between Geometry 1 and 3 was 0.24%, while the maximum median difference between particle and flow distribution was 0.62%. The results suggest that the hepatic arterial tree might be reliably truncated to estimate the particle distribution in the full-complexity tree. In the resulting hybrid particle-flow model, explicit particle modeling was only deemed necessary in the first few bifurcations of the arterial tree. Interestingly, using flow distribution as a surrogate for particle distribution in the entire tree was considerably less accurate than using the hybrid model, although the difference was much higher for catheter injections than for planar injections. Future work should focus on replicating and experimentally validating these results in more patient-specific geometries.

Achieving Near-Uniform Fluid and Proppant Placement in Multistage Fractured Horizontal Wells: A Computational Fluid Dynamics Modeling Approach

SummaryMultistage plug-and-perforate fracturing of horizontal wells has proved to be an effective method to develop unconventional reservoirs. Various studies have shown uneven fluid and proppant distributions across all perforation clusters. It is commonly believed that both fracturing fluid and proppant contribute to unconventional well performance. Achieving uniform fluid and proppant placement in all perforation clusters is an important step toward optimal stimulation. This paper discusses how to achieve such uniform placement in each fracturing stage by means of a computational fluid dynamics (CFD) modeling approach.A laboratory-scale CFD model was built and calibrated using experimental data of proppant transport through horizontal pipes available from several laboratory configurations. A field-scale model was then built and validated using perforation erosion data from downhole camera observations. With the field-scale model validated, CFD simulations were performed to evaluate the impact of key parameters on fluid and proppant placement in individual perforations and clusters. Some key parameters investigated in this study included perforation variables (orientation, size, and number), cluster variables (count and spacing), fluid properties, proppant properties, pumping rates, and stress shadow effects.Both laboratory and CFD results show that bottom-side perforations receive significantly more proppant than top-side perforations because of gravitational effects. Laboratory and CFD results also show that proppant distribution is increasingly toe-biased at higher rates. Proppant concentration along the wellbore from heel to toe varies significantly. Gravity, momentum, viscous drag, and turbulent dispersion are key factors affecting proppant transport in horizontal wellbores. This study demonstrates that near-uniform fluid and proppant placement across all clusters in each stage is achievable by optimizing perforation/cluster variables and other treatment design factors. CFD modeling plays an important role in this design-optimization process.

Performance assessment of solar PV and thermal-driven humidification dehumidification systems: A CFD modelling approach

Demand for clean water rises continuously with the increase in population. One of the promising techniques for sustainable water production is achieved through humidification and dehumidification (HDH) technique. The present study focuses on the fluid dynamic design processes and the system performance using solar energy as primary source in HDH process. Computational fluid dynamics (CFD) simulations are validated against the standard experimental results of solar photovoltaic panel (PVP) HDH system, published in the literature. The performance of the PVP HDH system is analyzed for improvement with the partitions and fin surfaces in the humidifier and dehumidifier chambers respectively. From this study, it is found that performance in yield of a basic PVP system increases by 16 % after the improvement in PVP system with partitions and fins in humidifier and dehumidifier respectively. For the efficient performance and cheaper production cost, the parabolic trough collector (PTC) HDH system is also investigated at horizontal and sloping conditions. Theoretical heat transfer calculations and experimental measurements from literature are included for the validation of PTC humidifier and dehumidifier investigations by CFD approach. Analytical calculations are performed in the combined PTC-solar still configuration also. The improved PTC system with slope shows 18 % higher yield as compared to the improved PVP system. GOR and SDWP are investigated between the PTC and PVP HDH systems and the cost analysis is included to find the payback time period in the basic and improved HDH systems.

Biomass gasification using mixtures of air, saturated steam, and oxygen in a two-stage downdraft gasifier. Assessment using a CFD modeling approach

This work proposes and employs a mixed-complexity modeling approach to creating a 3D computational fluid dynamics (CFD) model to predict the syngas production from Miscanthus briquettes in a two-stage downdraft gasifier operating with different gasification fluids. The study was performed at steady state regime in the Ansys Fluent environment considering the non-premixed combustion model. A probability density function is also included as a tool for the description of the chemical kinetics to predict the syngas composition following the main chemical reactions involved in the gasification process. The goal of this approach is to reduce the computational cost while still providing accurate predictions. In comparison to experimental gasification with air, the model correctly predicts the temperature profile inside the reactor, the composition of the syngas (CO, H2 and CH4), and therefore the lower heating value (LHV). For cases involving the use of saturated steam and oxygen as gasification fluids, the model predicted key species concentrations in the gasification zone and the reactor core and accurately described the significant increase in the LHV of the syngas. This approach opens the possibility of studying the gasification process in moving-bed reactors using different gasification fluids and feedstocks based on their elemental and proximate analysis.

Ultrasonic oscillatory two-phase flow in microchannels

Experimental and numerical investigations are performed to provide an assessment of the transport behavior of an ultrasonic oscillatory air–water two-phase flow in a microchannel. The flow exhibits highly unsteady behavior as the water and air interact with each other during the vibration cycles, making it significantly different from the well-studied steady flow in microchannels. The computational fluid dynamics (CFD) modeling is realized by combing the turbulence Reynolds-averaged Navier–Stokes k−ω model with the phase-field method in the Eulerian framework to resolve the dynamics of the two-phase flow. The numerical results are qualitatively validated by the experiment. Through parametric studies achieved by CFD simulation, we specifically examined the effects of vibration conditions (i.e., frequency and amplitude), microchannel taper angle, and wall surface contact angle (i.e., wettability) on the flow rate through the microchannel. The configuration for the highest flow rate is identified, which will help optimize the efficiency of a novel ultrasonic drying device. The described CFD modeling approach may also advance the potential applications where oscillatory or general unsteady microchannel two-phase flows may be present.

Novel CFD modeling approaches to assessing urine flow in prostatic urethra after transurethral surgery

Assessment of the pressure and velocity of urine flow for different diameter ratios of prostatic urethra (RPU) after transurethral surgery using computational fluid dynamics (CFD). A standardized and idealized two-dimensional CFD model after transurethral surgery (CATS-1st) was developed for post-surgery mid-voiding. Using CATS-1st, 210 examples were amplified according to an array of size [3][5][14], which contained three groups of longitudinal diameters of prostatic urethra (LD-PU). Each of these groups contained five subgroups of transverse diameters of the bladder neck (TD-BN), each with 14 examples of transverse diameters of PU (TD-PU). The pressure and velocity of urine flow were monitored through flow dynamics simulation, and the relationship among RPU-1 (TD-PU/TD-BN), RPU-2 (RPU-1/LD-PU), the transverse diameter of the vortex, and the midpoint velocity of the external urethral orifice (MV-EUO) was determined. A total of 210 CATS examples, including CATS-1st examples, were analyzed. High (bladder and PU) and medium/low (the rest of the urethra) pressure zones, and low (bladder), medium (PU), and high (the rest of the urethra) velocity zones were determined. The rapid changes in the velocity were concentrated in and around the PU. Laminar flow was present in all the examples. The vortices appeared and then gradually shrank with reducing RPU on both the sides of PU in 182 examples. In the vortex examples, minimum RPU-1 and RPU-2 reached close to the values of 0.79 and 0.02, respectively. MV-EUO increased gradually with decreasing RPU. In comparison to the vortex examples, the non-vortex examples exhibited a significantly higher (p < 0.01) MV-EUO. The developed CFD models (CATS) presented an effective simulation of urine flow behavior within the PU after transurethral surgery for benign prostatic hyperplasia (BPH). These models could prove to be useful for morphological repair in PU after transurethral surgery.

Characterization of Structural Properties in High Reynolds Hydraulic Jump Based on CFD and Physical Modeling Approaches

AbstractA classical hydraulic jump with Froude number (Fr1=6) and Reynolds number (Re1=210,000) was characterized using the computational fluid dynamics (CFD) codes OpenFOAM and FLOW-3D, whose perf...

Experimental and numerical investigation of the Advanced Fuel Ignition Delay Analyzer (AFIDA) constant-volume combustion chamber as a research platform for fuel chemical kinetic mechanism validation

Advanced combustion engine strategies that can offer increased efficiency and reduced emissions are enabled by numerical engine combustion simulations, requiring accurate chemical kinetic mechanism input. The Advanced Fuel Ignition Delay Analyzer (AFIDA) device can perform high quality, repeatable measurements of ignition delay (ID) times using small fuel quantities with high throughput. The AFIDA experiments involve liquid fuel injection into the heated and pressurized constant-volume chamber, producing an autoignition delay resulting from a combination of physical mixing and chemical kinetic processes, a complexity which makes the development of complementary numerical models necessary for the development and validation of chemical kinetic mechanisms. Modeling the device based on a homogenous approximation with reduced primary reference fuel (PRF) mechanism shows up to 75% error in the modeled vs. observed autoignition delay data for n-heptane and iso-octane at 10 bar (ɸ = 1.2–0.8) and 20 bar (ɸ = 0.6–0.4) over 973–648 K, whereas the use of a computational fluid dynamics (CFD) model reduces the discrepancy to within 25%. The homogenous approximation error is greatest for conditions where the observed ignition delay is short and the system is not sufficiently mixed (<30 ms), providing guidance to select a homogenous reactor vs. CFD modeling approach based upon desired accuracy. Experimental 20 bar iso-octane ID results show a larger magnitude of negative temperature coefficient chemistry compared to numerical results, indicating possible deficiencies in the PRF chemical kinetic mechanism. This characterization demonstrates the AFIDA as a capable research platform for chemical kinetic model development and validation.

CFD code-to-code benchmarking on simulation of fire and smoke propagation for nuclear applications

Abstract The nuclear industry has seen an increased use of Computational Fluid Dynamics (CFD) technology as a high-fidelity tool for design-basis and beyond design-basis accident simulations. For fire hazards, detailed experimental investigation in a realistic environment is often impractical. Therefore, the use of an advanced 3D CFD modeling approach to predict smoke and fire propagation has risen, especially for nuclear power plant fire modeling applications. CFD simulations can include major contributing and mitigating mechanisms regarding the fire propagation and its consequences, in fine detail and under realistic geometry conditions. In addition, accurate simulations of unsteady 3D fire and smoke spread, in conjunction with evacuation analyses, can be used to establish effective emergency evacuation strategies. In the present study, the fire and smoke propagation in a main control room was modelled using Reynolds-Averaged Navier-Stokes Equation based twoequation turbulence models and a Large Eddy Simulation model implemented in a commercial CFD code, Siemens STAR-CCM+. The predictions from STAR-CCM+ were compared with those obtained in a previous study using the NIST Fire Dynamic Simulator (FDS) code. Although higher temperature was predicted at the fire source by STAR-CCM+, the current study predicted trends similar to the FDS results with some minor differences at the operator location. A follow-up study is currently underway to investigate the factors affecting the differences, including further assessment of codes against available benchmark experiments.

An improved CFD modeling approach applied for the simulation of gas–liquid interaction in the ozone contactor along with structure optimization

An improved two-phase computational fluid dynamics (CFD) model has been developed by incorporation of Eulerian-Eulerian approach and user defined function (UDF) to address the liquid–gas flow and ozone reaction in an ozone contactor. Besides, a novel structure optimization design was proposed to improve the performance of contactor. Tracer residence time distribution (RTD) and distribution of CT value were applied as the indicators of contactor performance by conventional single phase model and improved two-phase model, respectively. The validation tests revealed that the improved two-phase CFD model is a reliable tool for the simulation of ozone contactor performance with good accuracy. The simulated results showed that this optimization design can greatly reduce the short-circuiting and dead zone in the contactor, along with the improvement of ozone mass transfer efficiency. Also much higher improvement of average CT value (310% increment) than the improvement of baffling factor (48.8% increment) denotes that the two-phase model is recommendable in the future study, and the use of baffling factor will underestimate the performance of ozone contactor.

Respirable dust pollution characteristics within an underground heading face driven with continuous miner – A CFD modelling approach

Respirable dust pollution at an underground heading face driven with continuous miner was detected during a ventilation survey. In order to obtain fundamental understandings of the airflow patterns and the respirable dust dispersion characteristics within the heading face, three dimensional Computational Fluid Dynamics (CFD) models were developed according to field condition. The continuous miner (JOY 12CM27), which significantly impacts the ventilation and respirable dust flow behaviour, was embedded into the model. The inappropriate ventilation arrangement, lack of effective dust control measures, as well as insufficient maintenance of equipment (e.g. blunt picks, missing nozzles etc.) were identified as the main reasons causing the high dust exposure levels (greater than 500 mg/m3). Based on the CFD model results, a new ventilation arrangement together with dust mitigation strategy were proposed. And an evaluation of the proposed system demonstrated a high respirable dust mitigation effect (90%) could be achieved. Therefore, it is highly recommended these control strategies to be implemented immediately to address the extremely high dust levels in the underground working environment. The proposed strategy will be also suitable for headings with similar conditions and could provide guidance for mining operators to refer.

Moisture adsorption in palletised corrugated fibreboard cartons under shipping conditions: A CFD modelling approach

Corrugated fibreboard packages (cartons) must support considerable mechanical loads during long term transport of fresh produce in refrigerated freight containers (RFCs). Fresh produce are transported under high relative humidity to reduce fruit moisture loss and preserve quality. However, these conditions can progressively reduce carton mechanical strength over time as a result of mechano-sorptive creep. Little is known regarding the actual moisture dynamics in stacked cartons in RFCs, which is important for mechanical strength assessments. To this end, a portion of a fully loaded RFC was investigated using a computational fluid dynamics (CFD) model, with respect to moisture transport in the air and the corrugated fibreboard. Simulations included the effects of loading, defrost cycles, fruit respiration and transpiration.Results showed relatively low moisture content gradients in fibreboards through the stacked cartons under optimal shipping conditions. However, the initial activation of the RFC considerably accelerated the development of moisture content gradients in the cartons. Additionally, the most significant factor influencing spatial moisture gradients through the cartons was heat conduction from outside through the container wall.

A practical CFD modeling approach to estimate outlet boundary conditions of industrial multistage spray dryers: Inert particle flow field investigation

Industrial multistage spray drying systems often have limited in situ process measurements to provide sufficient information for computational fluid dynamics (CFD) simulations of the primary drying chamber. In this case study on the spray dryer at Davis Dairy Plant (South Dakota State University), uncertainties were encountered in specifying the outlet boundary conditions of the spray drying chamber with two outlets: the side outlet and the bottom outlet leading to the second stage external vibrating bed. Using the available data on the vacuum pressure of the chamber, a numerical framework was introduced to approximate suitable outlet boundary conditions for the drying chamber. The procedure involved analyzing the ratio of the airflow rate between the two outlets and using a pseudo-tracer inert particle injection analysis. The goal of this approach was to determine a suitable range of outlet vacuum pressure that will lead to realistic particle movement behaviors during the actual plant operation. The protocol developed here will be a useful tool for CFD modeling of large scale multistage spray drying systems.Abbreviations: ARC: Australian Research Council; CFD: Computational Fluid Dynamics; FFT: Fast Fourier Transform; MCC: Micellar Casein Concentrate; PRESTO: Pressure Staggering Option; SDSU: South Dakota State University; SIMPLE: Semi − Impilicit Method for Pressure Linked Equations; WPC: Whey Protein Concentrate

Improved dust management at a longwall top coal caving (LTCC) face – A CFD modelling approach

Dust management at longwall faces has always been a concern for mine operators. Recent respirable dust monitoring at a longwall top coal caving (LTCC) face indicated that extremely high dust exposure levels have been experienced at the face. Dust contamination from intake ventilation and the incorrect use of ventilation arrangements (i.e. curtains) at maingate (MG) area were identified as the main cause of this issue. Computational Fluid Dynamics (CFD) modelling studies were therefore conducted to investigate the impact of different ventilation arrangements on the dispersion behaviour of respirable dust at the LTCC face, with a special focus on the airflow patterns and the aerodynamics of fugitive dust at the intersection of MG and face. Field investigation was first carried out to observe the dust issue and obtain essential data for the development and validation of base model. Then parametric studies were conducted to evaluate the effectiveness of two different curtain configurations at MG considering the worst scenario of intake dust contamination to face (dust from travel road and beam stage loader (BSL) discharge point flows towards face) with the shearer cutting into the MG. Model results demonstrate that the occurrence of flow separation and incorrect use of curtains account for the main reasons of high dust exposure level at the intersection of MG and face, especially when the shearer is cutting into the MG. Ventilation arrangements at the MG and face entry are critical to minimise the impact of flow separation on the dust flow patterns at the intersection. Based on model results, new ventilation arrangements at the MG and face entry have been proposed and evaluated through which significant dust mitigation effect can be achieved at face entry, contributing to the overall reduction of dust exposure levels along the face.

Effects of different CFD modeling approaches and simplification of shape on prediction of flow field around manikin

Providing a comfortable and pleasant indoor environment for the occupants is the primary objective of an efficient ventilation process. Therefore, it is important to gain a proper understanding between the interaction of airflow and the occupants which determines the ultimate ventilation strategy and as one of the final outcomes, the architecture layout itself. The CFD (Computational Fluid Dynamics) methods provide an accurate and robust tool to simulate the complex airflow structure in enclosed spaces. Among the CFD simulation approaches, the large eddy simulation (LES) and its hybrid variants such as detached eddy simulation (DES) provides the information on the flow behavior by modeling the small turbulent structures of the airflow encountered in an indoor environment. These methods are highly sensitive to the boundary conditions which are the pivotal factors in an indoor airflow modeling and its accuracy. The main objectives of this paper are: (a) to assess the performance of different LES and DES models in capturing velocity and thermal fields (b) to investigate the effect of manikin’s shape on the accuracy of predictions. Three LES SGS (sub-grid scale) and one DES models are applied in this study considering the cases with and without the radiation from the manikin. Moreover, the effect of simplifying the manikins’ geometry on velocity and thermal distribution is investigated. Results showed that a detailed manikin shape can provide more accurate predictions (4–10%) at some locations, especially those close to the manikin’s body. As for performance of the applied models, Comparisons showed that ZEM and WALE models provide a better predictions of velocity and temperature fields by 3–10% at different locations.