Inlet Boundary Conditions Research Articles

A numerical approach for inlet-outlet boundary conditions with least-square moving particle explicit (LSMPE) method on GPU

ABSTRACT In severe accidents of nuclear reactors, studying the pressure drop of debris beds is of great significance for delaying the progression of the accident. However, traditional MPS often exhibits significant pressure oscillation issues when dealing with the inlet-outlet boundary. The study introduces a method for managing inlet and outlet boundary conditions using the Least-Square moving particle explicit method (LSMPE). A high-precision least squares discrete method was applied to the moving particle explicit method (MPE) based on predictive-corrected pressure. The code was accelerated using OpenACC for parallelization. Special boundary treatments were applied to minimize errors induced by boundaries, including particle number density correction for inlet particles, addressing slip or nonslip boundaries, and introducing concept particles at the outlet. The stability and accuracy of this method were validated through three cases. Simulation results for Poiseuille flow and circular flow demonstrated the method’s good precision, exhibiting stable pressure fields. Results from single-phase flow simulations through a porous medium bed agreed well with predictions from the Ergun equation, highlighting the method’s potential for practical engineering applications.

Effects of inlet boundary conditions on blood flow and thrombosis modelling in patients with chronic thromboembolic pulmonary hypertension

To investigate the impact of patient-specific boundary conditions (BC) on blood flow and thrombosis modelling for patients with chronic thromboembolic pulmonary hypertension (CTEPH), three types of BCs were utilized to construct CTEPH models based on computed tomography pulmonary angiography images. First BC type is the patient-specific velocity profiles at the main pulmonary artery using phase contrast MRI (PC-MRI). The other two simplified types are the pulsatile BC and steady BC, which are obtained by spatially and temporally averaging the PC-MRI BC. Hemodynamic features including helical density, time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI), and thrombosis were compared for the three types BCs. The results indicated that, compared to the MRI BC, steady BC overestimated helical density and TAWSS in the pulmonary arteries by approximately 63.1% and 60%, respectively. The impact of simplified pulsatile BC on TAWSS and OSI in most regions of the pulmonary arteries was negligible with differences within 5%. Regarding thrombosis, the area predicted under pulsatile BC was approximately 80% smaller than that under PC-MRI BC. In conclusion, compared to PC-MRI BC, steady inlet BC tend to overestimate hemodynamic parameters, while pulsatile inlet BC yield similar wall shear stress based on parameters in most regions of the pulmonary artery. Patient-specific PC-MRI inlet BC should be used for accurate predictions of helical flow pattern and thrombus formation.

Modeling for formation of microdroplets prepared by pulsated orifice ejection method

Abstract This study investigated the preparation of metallic microdroplets by pulsed orifice ejection method. Computational fluid dynamics simulations, combined with volume-of-fluid model, were employed to analyze the jet break-up and droplet formation behaviors of various metallic materials within a certain Weber number (We) range. An energy-based physical model under inlet boundary conditions was established to precisely control the generation of droplets. The results indicate that the break-up state of metal jets is significantly influenced by material properties within the range that We = 12 ∼ 24, which makes the materials exhibiting higher surface tension and density relatively favorable to the production of mono-sized microdroplets. Moreover, the break-up behavior of the jet is closely related to the ratio of volume force to surface tension (Bond number). And the proposed model effectively predicts the properties of droplets. This research provides theoretical guidance and technical support for the precise preparation of metallic microdroplets.

Research on temperature distribution characteristics of oil‐immersed power transformers based on fluid network decoupling

AbstractDue to the complex structure and large size of large‐capacity oil‐immersed power transformers, it is difficult to predict the winding temperature distribution directly by numerical analysis. A 180 MVA, 220 kV oil‐immersed self‐cooling power transformer is used as the research object. The authors decouple the internal fluid domain of the power transformer into four regions: high voltage windings, medium voltage windings, low voltage windings, and radiators through fluid networks and establish the 3D fluid‐temperature field numerical analysis model of the four regions, respectively. The results of the fluid network model are used as the inlet boundary conditions for the 3D fluid‐temperature numerical analysis model. In turn, the fluid resistance of the fluid network model is corrected according to the results of the 3D fluid‐temperature field numerical analysis model. The prediction of the temperature distribution of windings is realised by the coupling calculation between the fluid network model and the 3D fluid‐temperature field numerical analysis model. Based on this, the effect of the loading method of the heat source is also investigated using the proposed method. The hotspot temperatures of the high‐voltage, medium‐voltage, and low‐voltage windings are 89.43, 86.33, and 80.96°C, respectively. Finally, an experimental platform is built to verify the results. The maximum relative error between calculated and measured values is 4.42%, which meets the engineering accuracy requirement.

Effective lateral dispersion of momentum, heat and mass in bubbling fluidized beds

The lateral dispersion of bed material in a bubbling fluidized bed is a key parameter in the prediction of the effective in-bed heat transfer and transport of heterogenous reactants, properties important for the successful design and scale-up of thermal and/or chemical processes. Computational fluid dynamics simulations offer means to investigate such beds in silico and derive effective parameters for reduced-order models. In this work, we use the Eulerian-Eulerian two-fluid model with the kinetic theory of granular flow to perform numerical simulations of solids mixing and heat transfer in bubbling fluidized beds. We extract the lateral solids dispersion coefficient using four different methods: by fitting the transient response of the bed to (1) an ideal heat or (2) mass transfer problem, (3) by extracting the time-averaged heat transfer behavior and (4) through a momentum transfer approach in an analogy with single-phase turbulence. The method (2) fitting against a mass transfer problem is found to produce robust results at a reasonable computational cost when assessed against experiments. Furthermore, the gas inlet boundary condition is shown to have a significant effect on the prediction, indicating a need to account for nozzle characteristics when simulating industrial cases.

Failure analysis of erosion wear of the pipeline after 30° elbow by adsorbent particles

An adsorbent transport pipeline after a 30° elbow experienced premature perforation and leakage during service. The failure analysis was performed by means of morphology observation, damaged surface analysis and computational fluid dynamics (CFD) simulation. The results revealed that thickness thinning occurred only on the upper wall, and the severely thinned region exhibited a special striated groove morphology. The main cause of pipeline failure was attributed to erosive wear caused by adsorbent impacts on the wall. Due to the particle redistribution process under the action of multiple force fields in the small bending angle elbow, the straight pipeline after the elbow had a very complex inlet boundary condition, so that the particle concentration at the upper wall was substantially increased. Besides, the sliding motion of the particles on the wall surface was greatly intensified. Cutting deformation became the main form of erosion damage, which induced an alteration in the erosional morphology of the failed pipeline and the backwardness of the leakage site.

Uncertainty quantification of the inlet boundary conditions in a supercritical CO2 centrifugal compressor based on the non-intrusive polynomial chaos

Given the sensitivity of supercritical carbon dioxide centrifugal compressors performance to inlet boundary parameter fluctuations, this study focuses on the uncertainty quantification of the inlet boundary conditions. Non-intrusive polynomial chaos surrogate models were developed for both performance parameters and flow field of a supercritical carbon dioxide centrifugal compressor. Sensitivity and correlation analyses revealed that inlet total temperature is the primary influencing parameter. Fluctuations of 1.37 % in total temperature and 6.75 % in total pressure result in changes of 40.94 %, 18.57 %, and 1.77 % in mass flow rate, total pressure ratio, and total to total isentropic efficiency, respectively. Flow field statistical analysis shows that inlet uncertainties nonlinearly impact the dryness fraction and relative Mach number distributions near the blade leading edge, while the density in the condensation zone on the suction side of the leading edge is less affected. Error bands in static pressure on blade surfaces highlight significant variations, particularly at 90 % spanwise on the blade suction side, where shocks and supersonic flow induce prominent disturbances. This study offers a preliminary methodology and theoretical guidance for robust aerodynamic optimization and operational strategies of supercritical carbon dioxide centrifugal compressors.

Wind-induced response of saddle membrane structure under typhoon wind field by weather research and forecasting model and computational fluid dynamics

Currently, the research on wind-induced response of membrane structures focuses on the normal wind field, and there is little research on typhoon with greater disaster. In this paper, the wind-induced response of saddle membrane structures under typhoon is studied by numerical simulation. Firstly, the wind field information of typhoon is simulated according to the Weather Research and Forecasting model, and the information is used as the inlet boundary condition of Computational Fluid Dynamics. The vibration modal analysis is carried out, considering the influence of wind field intensity, wind direction angle, rise-span ratio, and pretension on the displacement of the membrane. The results show that the probability density curve of wind-induced response has a certain skewness. The saddle membrane structure has the largest vibration amplitude of the membrane at 0° wind direction angle, and the most unfavorable wind pressure value of the membrane is negative. In reducing the displacement of the membrane, the effect of reducing the wind-induced vibration response by increasing the rise-span ratio of the structure is better than that of the pretension. This paper reveals that the law of wind-induced response can provide a theoretical basis for the design of membrane structures against typhoons.

Investigation into the Computational Analysis of High–Speed Microjet Hydrogen–Air Diffusion Flames

High-speed microjet hydrogen–air diffusion flames are investigated computationally. The focus is on the prediction of the so-called bottleneck phenomenon. The latter has been previously observed as a specific feature of the present flame class and has not yet been investigated computationally. In the configuration under consideration, the nozzle diameter is 0.5 mm and six cases with mean nozzle injection velocities (U) between 306 m/s and 561 m/s are considered. The flow in the nozzle lance is analyzed separately to obtain detailed inlet boundary conditions for the flame calculations. It is confirmed by calculation that the phenomenon is mainly determined by the transition to turbulence in the initial parts of the free jet. The transitional turbulence proves to be the biggest challenge in predicting this class of flames, as the generally available turbulence and turbulent combustion models reach the limits of their validity in transitional flows. In a Reynolds-Averaged Numerical Simulation framework, the Shear Stress Transport model is found to perform better than alternative two-equation models and is used as the turbulence model. By neglecting the interactions between the turbulence and chemistry (no-model approach), it is possible to predict the morphology of the bottleneck flame and its dependence on U qualitatively. However, the position of the bottleneck is overpredicted for U < 561 m/s. The experimental flames in the considered U range are all attached to the nozzle. This is also predicted by the no-model approach. The Eddy Dissipation Concept (EDC) used as the turbulence combustion model predicts, however, lifted flames (with increasing lift-off height as U decreases). With the EDC, no bottleneck morphology is observed for U = 561 m/s. For lower U, the EDC results for the bottleneck position are generally closer to the measurements. It is demonstrated that accuracy in predicting the bottleneck position can be improved by ad hoc modifications of the turbulent viscosity.

The Effect of Unsteady Inlet Boundary Conditions on the Aero-Thermal Behavior of High-Pressure Turbine Vanes – A Numerical Study Using Scale-Resolving Simulations

Abstract This paper presents the application of a novel method to prescribe unsteady boundary conditions to transient, scale-resolving computational fluid dynamics simulations of the high-pressure turbine in modern jet engines. The methodology is based on the compression of the interface data at the combustor–turbine interface, using proper orthogonal decomposition and Fourier series (PODFS). Doing so can reduce the stored data at the interface drastically. The capability of the PODFS method to produce realistic inlet boundary conditions was demonstrated in previous work. Here, the method is applied to a turbine case. The outlet data of a combustor simulation is used to create the PODFS boundary conditions for a scale-resolving simulation of a simplified first nozzle guide vane of the high-pressure turbine. This simulation is compared with simulations with steady-state boundary conditions to show the effect of unsteadiness in the inlet boundary condition on the aerodynamic and thermal behaviors of the turbine. While the aerodynamics show minor sensitivity against the way of applying the inlet boundary conditions, the thermal behavior of the vanes is strongly affected by the modeling of combustor unsteadiness.

A new method for scaling inlet flow waveform in hemodynamic analysis of aortic dissection.

Computational fluid dynamics (CFD) simulations have shown great potentials in cardiovascular disease diagnosis and postoperative assessment. Patient-specific and well-tuned boundary conditions are key to obtaining accurate and reliable hemodynamic results. However, CFD simulations are usually performed under non-patient-specific flow conditions due to the absence of in vivo flow and pressure measurements. This study proposes a new method to overcome this challenge by tuning inlet boundary conditions using data extracted from electrocardiogram (ECG). Five patient-specific geometric models of type B aortic dissection were reconstructed from computed tomography (CT) images. Other available data included stoke volume (SV), ECG, and 4D-flow magnetic resonance imaging (MRI). ECG waveforms were processed to extract patient-specific systole to diastole ratio (SDR). Inlet boundary conditions were defined based on a generic aortic flow waveform tuned using (1) SV only, and (2) with ECG and SV (ECG + SV). 4D-flow MRI derived inlet boundary conditions were also used in patient-specific simulations to provide the gold standard for comparison and validation. Simulations using inlet flow waveform tuned with ECG + SV not only successfully reproduced flow distributions in the descending aorta but also provided accurate prediction of time-averaged wall shear stress (TAWSS) in the primary entry tear (PET) and abdominal regions, as well as maximum pressure difference, ∆Pmax, from the aortic root to the distal false lumen. Compared with simulations with inlet waveform tuned with SV alone, using ECG + SV in the tuning method significantly reduced the error in false lumen ejection fraction at the PET (from 149.1% to 6.2%), reduced errors in TAWSS at the PET (from 54.1% to 5.7%) and in the abdominal region (from 61.3% to 11.1%), and improved ∆Pmax prediction (from 283.1% to 18.8%) However, neither of these inlet waveforms could be used for accurate prediction of TAWSS in the ascending aorta. This study demonstrates the importance of SDR in tailoring inlet flow waveforms for patient-specific hemodynamic simulations. A well-tuned flow waveform is essential for ensuring that the simulation results are patient-specific, thereby enhancing the confidence and fidelity of computational tools in future clinical applications.

Influence of fuel inhomogeneity on detonation wave propagation in a rotating detonation combustor

Rotating detonation combustor (RDC) is a form of pressure gain combustion, which is thermodynamically more efficient than the traditional constant-pressure combustors. In most RDCs, the fuel–air mixture is not perfectly premixed and results in inhomogeneous mixing within the domain. Due to discrete fuel injection locations, local pockets of rich and lean mixtures are formed in the refill region. The objective of the present work is to gain an understanding of the effects of reactant mixture inhomogeneity on detonation wave structure, wave velocity, and pressure profile. To study the effect of mixture inhomogeneity, probability density functions of fuel mass fractions are generated with varying standard deviations. These distributions of fuel mass fractions are incorporated in 2D reacting simulations as a spatially/temporally varying inlet boundary condition. Using this methodology, the effect of mixture inhomogeneity is independently investigated to determine the effects on detonation wave propagation and RDC performance. As mixture inhomogeneity is increased, detonation wave speed, detonation efficiency, and potential for pressure gain all decrease, ultimately leading to the separation of the reaction zone from the shock wave.

Determination of Local Heat Transfer Coefficients and Friction Factors at Variable Temperature and Velocity Boundary Conditions for Complex Flows

Transient conjugate heat transfer measurements under varying temperature and velocity inlet boundary conditions at incompressible flow conditions were performed for flat plate and ribbed channel geometries. Therefrom, local adiabatic wall temperatures and heat transfer coefficients were determined. The data were analyzed using typical heat transfer correlations, e.g., Nu=CRemPrn, determining the local distributions of C and m. It is shown that they are closely linked. A relationship lnC=A−mB is observed, with A and B as modeling parameters. They could be related to parameters in log-law or power-law representations for turbulent boundary layer flows. The parameter m is shown to have a close link to local pressure gradients and, therewith, near wall streamlines as well as friction factor distributions. A normalization of the C parameter allows one to derive a Reynolds analogy factor and, therefrom, local wall shear stresses.

Study on the performance of catalytic reactor for aircraft fuel tank inerting system

The catalytic reactor, which plays a pivotal role in the novel aircraft fuel tank green inerting system, encounters complex and alternating inlet boundary conditions. In this study, a transient theoretical model of the catalytic reactor was established and solved through programming, and its accuracy was verified through self-built experimental setups. The dynamic performance of the catalytic reactor and the impact of operational parameters were investigated. Additionally, a method for determining the operational range of the catalytic reactor was proposed. The results indicate that the bed temperature gradually increases to 370°C along the axial direction as the reaction progresses over time. In addition, the concentrations of fuel vapor and oxygen gradually decrease along the axial direction or with time, while achieving a fuel vapor conversion rate of 70.13% under design conditions. The promotion of catalytic reactions can be achieved by lowering the inlet gas velocity, elevating temperature, or increasing the concentrations of fuel vapor and oxygen. However, the bed's maximum temperature may surpass the self-ignition temperature of fuel vapor by 425°C. A novel indicator for oxygen consumption rate is proposed, which should be comprehensively evaluated in conjunction with the conversion rate to determine the performance of catalytic reactors. Moreover, increasing the reactor diameter can enhance both conversion rate and oxygen consumption rate. Pressure drop is detrimental to the catalytic reaction, therefore, high altitude and low-pressure conditions should be considered as the standard for reactor design. Meanwhile, this paper proposes a theoretical model to determine the operational range of the catalytic reactor based on criteria such as suitable catalytic efficiency and flight temperature. The research findings presented in this study provide a solid theoretical foundation for optimizing catalytic reactor design, thereby significantly promoting the application of green inerting systems.

Numerical modeling and experimental validation of fluid flow in micro- and meso-fluidic siphons

Siphons have been used for thousands of years to transfer fluids without the use of pumps or power and are present in our daily lives. Paradoxically, it is only in recent decades that the operation of siphons has been fully clarified, which is now understood to be exclusively linked to gravity and molecular cohesion. Siphons are uniquely able to offer automatic, intermittent flow, yet present the main drawback of requiring a source of energy to induce initial flow. Our research team has recently disclosed a microfluidic siphon able to self-prime and deliver a sequence of bioanalytical reagents, previously demonstrated for high-performance, multi-reagents diagnostic testing. Here we show for the first time 2D and 3D computational fluid dynamics (CFD) modeling and the experimental characterization of fluid flow in a range of miniaturized hydrophilic siphons of varying hydraulic liquid height-to-length ratios, ΔH/LT = 0–0.9, using fluids of varying viscosities. CFD simulations using velocity- and pressure-driven inlet boundary conditions were generally in good agreement with experimental fluid flow rates and pressure-balance predictions for plastic ∼0.2 mm and glass ∼0.6 mm internal diameter microfluidic siphons. CFD predictions of fluid flow in “meso-scale” siphons with 1 and 2 mm internal diameters also fully matched normalized experimental data, suggesting that miniaturized siphons are scalable. Their discharge rate and pressure drop are readily predicted and fine-tunable through the physical properties of the fluid and some design parameters of the siphon. The wide range of experimental and numerical parameters studied here provide an important framework for the design and application of gravity-driven micro- and meso-fluidic siphons in many applications, including but not limited to life sciences, clinical diagnostics, and process intensification.

Role of aneurysmal hemodynamic changes in pathogenesis of headaches associated with unruptured cerebral aneurysms.

One symptom commonly associated with the presence of unruptured intracranial aneurysms is headache. In this study, the authors aimed to analyze factors associated with headaches among patients with intracranial aneurysms, with special consideration of hemodynamic parameters. The authors prospectively included 96 patients with 122 unruptured intracranial aneurysms. The authors obtained detailed medical history including current diseases and medications, as well as blood pressure values taken during hospitalization from the patients' medical records. The short-form McGill Pain Questionnaire was administered to each patient at admission and 3-6 months after the procedure to assess type and severity of headache. Based on imaging data, the authors obtained 3D reconstruction of each patients' aneurysm dome with feeding artery. The authors performed computational fluid dynamics analysis of blood flow through prepared models using OpenFOAM. Blood was modeled as Newtonian fluid, using the incompressible transient solver. Patient-specific internal carotid artery (ICA) blood velocity waves obtained with Doppler ultrasound were set as inlet boundary conditions. After performing simulation, the authors calculated the hemodynamic parameters of the aneurysm dome. A total of 30 patients (31.25%) reported having headaches. In multivariate logistic regression analysis, female sex (OR 2.81, 95% CI 2.51-4.86; p < 0.01), ICA aneurysm location (OR 7.93, 95% CI 5.51-8.52; p < 0.01), multiple aneurysms (OR 6.05, 95% CI 1.83-11.83; p = 0.02), mean dome blood velocity (OR 3.10, 95% CI 2.01-3.30; p < 0.01) and time-averaged wall shear stress (OR 1.18, 95% CI 1.47-2.72; p = 0.04) were independently associated with the presence of headache. Additionally, 17 patients (56.67%) reported complete relief of symptoms after the procedure. In multivariate logistic regression analysis, the mean blood flow in the ICA was independently associated with complete resolution of headaches after aneurysm treatment (OR 2.32, 95% CI 1.57-3.28; p < 0.01). Hemodynamic parameters of intracranial aneurysms might be associated with headaches and their relief after aneurysm treatment.

Numerical Investigation of Effects of Ripple Type Needle Erosion on Pressure Inside a Pelton Nozzle

Abstract Pelton turbines, a commonly used impulse turbine for hydroelectric generation which converts the potential energy of the water into kinetic energy through a needle structure within the nozzle system. However, the exposure of the Pelton turbine components such as needle, seat ring, buckets to the sediment laden water can erode these components. The erosion on the needle can also lead to the efficiency degradation. This study aims to investigate the effect of needle erosion on the pressure dynamics within the Pelton nozzle system. For the study purpose, the nozzle system from Pelton rig at the Waterpower Laboratory, NTNU is used and a general erosion pattern is developed through literature and field information. The research focuses on analysing the difference in pressure distribution between the normal and eroded needles under different opening conditions, with the objective of understanding how erosion affects the nozzle performance. Single-phase 3-D simulations are performed with an unstructured ANSYS mesh and the CFX solver. This study examines the static pressure at the inner surface of the nozzle casing wall. The results show that for a constant head at the inlet boundary condition, the static pressure with eroded needles was significantly lower than that with normal needles. The pressure difference was around 1.88 kPa for a 60% nozzle opening and around 3.57 kPa for a 40% nozzle opening. The reduction in pressure is due to the increased area in the needle orifice and nozzle outlet caused by erosion, which is more pronounced at lower openings. The findings reveal a direct correlation between needle erosion and alterations in pressure distribution, highlighting the necessity for vigilant monitoring and timely maintenance. The study provides valuable insights into optimizing turbine performance in sediment-laden water conditions and underscores the importance of addressing needle erosion to maintain efficiency.

Can β-blockers prevent intracranial aneurysm rupture? - insights from Computational Fluid Dynamics analysis.

Hypertension is a risk factor for intracranial aneurysm rupture. We analyzed whether the intake of drugs from specific classes of anti-hypertensive medications affects hemodynamic parameters of intracranial aneurysm dome. We recorded medical history including medications and the in-hospital blood pressure values. We then obtained 3D reconstruction of each patients' aneurysm dome and the feeding artery. Using OpenFOAM software we performed Computational Fluid Dynamics analysis of blood flow through the modeled structures. Blood was modeled as Newtonian fluid, using the incompressible transient solver. As the inlet boundary condition we used the patient-specific Internal Carotid Artery blood velocity waves obtained with Doppler ultrasound. We calculated haemodynamic parameters of the aneurysm dome. All presented analyses are cross-sectional.We included 72 patients with a total of 91 unruptured intracranial aneurysms. The history of β-blocker intake significantly influenced hemodynamic parameters of aneurysm dome. The patients on β-blockers had significantly smaller aneurysm domes (5.09 ± 2.11 mm vs. 7.41 ± 5.89 mm; p = 0.03) and did not have aneurysms larger than 10 mm (0% vs 17.0%; p = 0.01). In the Computational Fluid Dynamics analysis, walls of aneurysms in patients who took β-blockers were characterized by lower Wall Shear Stress Gradient (1.67 ± 1.85 Pa vs. 4.3 ± 6.06 Pa; p = 0.03), Oscillatory Shear Index (0.03 ± 0.02 vs. 0.07 ± 0.10; p = 0.04) and Surface Vortex Fraction (16.2% ± 5.2% vs. 20.0% ± 6.8%; p<0.01). After controlling for covariates, we demonstrated difference of Surface Vortex Fraction (F[1, 48] = 4.36; p = 0.04) and Oscillatory Shear Index (F[1, 48] = 6.51; p = 0.01) between patients taking and not taking β-blockers, respectively. Intake of β-blockers might contribute to more favorable hemodynamics inside aneurysmal sac. Other antihypertensive medication classes were not associated with differences in intracranial aneurysm parameters.

Effect of flow modifiers on the fluid flow characteristics in a slab caster tundish

ABSTRACT In a slab caster tundish, controlling liquid steel flow is of paramount importance for clean steel production. A conventional tundish design consists of a pouring box, a weir and a dam. To improve the overall performance of a 40 ton slab caster tundish, three different arrangements by incorporating additional flow modifiers have been examined. A three-dimensional steady state fluid flow model has been developed using a RANS (Reynolds-Averaged Navier-Stokes) approach. Subsequently, transient scalar-transport equations were solved to obtain the C-curve of the tundish. A different approach has been followed to evaluate the inlet boundary condition to mimic the process conditions more accurately. The CFD predictions were validated with the results of the water model. Mean residence time, dead volume fraction and flow structures have been considered for evaluating tundish performance. All the proposed configurations have shown improvements in comparison to the base case. The mean residence time of the fluid was found to be the highest for the case having two pairs of weir and dam. However, the insights derived from the flow structures specifically plug flow in zone 2 and near the tundish outlet region suggest that that having a single weir and two dams is the optimal choice.

A fully coupled Pressure-Based method for compressible flows at all Mach numbers

When extending the fully coupled pressure-based method to resolve compressible flows, the effective treatment of the boundary conditions is crucial due to the inherent characteristics of compressible flows. Failure to properly account for this can result in numerical instability and divergence. In this article, a detailed treatment of boundary conditions for compressible flows has been formulated in terms of the boundary face’s contribution to the discretization equation of the boundary element. These boundary conditions involve subsonic inlet, supersonic inlet, subsonic outlet, and supersonic outlet boundary conditions. The analysis has been focused on test cases of flow through a bumped arc channel and a converging–diverging nozzle including quasi-incompressible, subsonic, transonic, supersonic and hypersonic speed regimes, where the Mach number ranges from 0.1 to 10. The results indicate the robust performance of the fully coupled method in resolving compressible flows. The computational results obtained from the fully coupled algorithm exhibit a high degree of consistency with available literature cases and analytical solutions, with a maximum error of less than 5%. Moreover, the findings also suggest that the coupled solver presents promising potential in handling hypersonic flows.