Flow Phenomena Research Articles

Phase diagram in multi-phase heterogeneous traffic flow model integrating the perceptual range difference under human-driven and connected vehicles environment

With the gradual development of autonomous driving and connected communication technology, urban road networks will be shared by a combination of Human-driven vehicles (HDVs) and Connected vehicles (CVs) for a long era. Besides, as the actual vehicle operator, the driver regulates the vehicle state with an accelerator, gear lever, or brake, whereas the stepwise acceleration process is overlooked in the literature. Motivated by this, comprehensive kinetic difference between the two types of vehicles, we propose a novel heterogeneous multi-phase traffic flow accounting for the HDVs and CVs to close this hole. In the section on linear stability analysis, the reductive perturbation approach was applied to figure out the stability norm of the new model. The findings show that, on the one hand, inhibiting traffic bottlenecks is positively impacted by the penetration rate of CVs and the number of preceding vehicles taken into account; on the other hand, by varying the headway between following vehicles, the multiple-phase transition occurs; consequently, the number of turning points in the optimal velocity function is the sole factor that affects the number of stages in multi-phase transitions. Subsequently, the modified Korteweg-de Vries (mKdV) equation corresponding to the new model is deduced to investigate the nonlinear phenomenon of traffic flow at the vicinity of the critical point, and the kink-antikink soliton wave solution by solving the above characteristic equation can describe the “stop-and-go” phenomenon in real traffic flow. Finally, the conclusion of the numerical experiments is consistent with the above theoretical analysis. This research can provide insight into the dynamic evolution of road traffic flow during the transition from HDVs to semi-CVs and eventually to CVs.

Laser-induced indirect ignition of non-premixed turbulent shear layers

This study uses direct numerical simulations to investigate the forced ignition of temporally-evolving turbulent subsonic shear layers separating a gaseous stream of methane (CH4) and a stagnant gas environment of molecular oxygen (O2). Ignition is forced by a thermal-energy source that heats up a small volume of gas during periods of time much shorter than the characteristic acoustic time scale. The kernel, including its initial rounded conical shape, resembles experimental observations after optical breakdown is achieved in a gas irradiated by a focused laser. Particular emphasis is placed on ignition phenomena observed when the laser is focused on the O2 environment outside the turbulent shear layer, where the local composition is far beyond the lean flammability limit. This represents an indirect mode of non-premixed ignition that develops after a relatively long period of time has passed since laser-energy deposition, when the eddies near the oxidizer edge of the turbulent shear layer are intercepted by a baroclinically-generated subsonic vortex of hot dissociated O2 ejected from the laser-energy deposition zone. The success of indirect ignition depends on the orientation of the laser beam, the thickness of the shear layer, and the kernel standoff distance from the oxidizer edge of the shear layer. An ignition Damköhler number is defined that accounts for these averaged effects in six different simulation cases. For near-unity ignition Damköhler numbers, the solution is also sensitive to the local instantaneous flow field prevailing near the oxidizer edge of the shear layer, in that a modification of the instantaneous pre-deposition flow field, while preserving its turbulence statistics, can produce different ignition outcomes.Novelty and significance statement This work investigates forced ignition in a canonical flow configuration – a non-premixed turbulent CH4/O2 shear layer – and analyzes mechanisms by which ignition can be unexpectedly achieved in adverse conditions. In particular, an ensuing laser-generated advection of hot dissociated gas is observed to ignite the shear layer even when the mixture at the laser focal point is not flammable, an observation first made in early experiments. This flow phenomenon, whose consequences on ignition of non-premixed turbulent flows have not previously been analyzed by direct numerical simulation, can significantly separate the laser-energy deposition zone from the ignition location and is linked to baroclinically generated vorticity due to the rounded conical shape of the energy kernel. The phenomenology analyzed here may impact the design of laser-based ignition systems for chemical propulsion.

Experiments on hydraulic jumps over uneven bed for turbulent flow modelling validation in river flow and hydraulic structures

This study presents a comprehensive dataset comprising multiple data packages derived from laboratory experiments on steady and unsteady hydraulic jumps interacting with a large-scale Gaussian-shaped bed obstacle in an open-channel flume. The primary objective was to accurately measure the impact of hydraulic jump on the free surface and the bed pressure along the obstacle, ensuring the transferability of the results. A multi-process method was followed: designed experiments were recorded, images were postprocessed, and water level data were digitalized. For steady conditions, the bed pressure along the obstacle were measured by piezometers. The repository data are organized and provided in a single package, supplemented by a second package containing panoramas for each experimental time instant and graphical representations of the data, facilitating rapid evaluation of the outcomes. This study provides versatile data that can be utilized in various ways, particularly for fluvial model validation and studying turbulence-driven phenomena in open-channel flows. The detailed methodology presented herein can contribute to the advancement of enhanced laboratory techniques to study similar flow problems.

Effect of network architecture on physics-informed deep learning of the Reynolds-averaged turbulent flow field around cylinders without training data

Unsupervised physics-informed deep learning can be used to solve computational physics problems by training neural networks to satisfy the underlying equations and boundary conditions without labeled data. Parameters such as network architecture and training method determine the training success. However, the best choice is unknown a priori as it is case specific. Here, we investigated network shapes, sizes, and types for unsupervised physics-informed deep learning of the two-dimensional Reynolds-averaged flow around cylinders. We trained mixed-variable networks and compared them to traditional models. Several network architectures with different shape factors and sizes were evaluated. The models were trained to solve the Reynolds-averaged Navier-Stokes equations incorporating Prandtl’s mixing length turbulence model. No training data were deployed to train the models. The superiority of the mixed-variable approach was confirmed for the investigated high Reynolds number flow. The mixed-variable models were sensitive to the network shape. For the two cylinders, differently deep networks showed superior performance. The best fitting models were able to capture important flow phenomena such as stagnation regions, boundary layers, flow separation, and recirculation. We also encountered difficulties when predicting high Reynolds number flows without training data.

Artificial neural network approach to simulate the impact of concentration in optimizing heat transfer rate on water-based hybrid nanofluid under slip conditions: A regression analysis

The recent era of science depends upon the efficient performance of the heat transfer rate in several engineering applications for which the role of nanofluids have a greater impact. Therefore, the impact of particle concentration in optimizing heat transfer analysis of water-based hybrid nanofluid is conducted via an artificial neural network. The combined effect of oxide nanoparticles such as MgO and TiO2 in water performs their effective role with various factors involved in the flow phenomena. The magnetized hybrid nanofluid flow over an expanding surface filled with porous material shows its noble behavior on the flow properties. Further, it is not usual to omit the effectiveness of the dissipative heat impact. Therefore, the role of viscous, Joule, and Darcy dissipation is incorporated in the energy profile for which the profiles became coupled. The designed nonlinear model invokes suitable similarity rules that give rise to a system of nonlinear ordinary equations in non-dimensional form. Afterwards, the traditional numerical approach is beneficial to conduct the simulation of the flow profiles. The optimization of the heat transfer rate analysis is obtained by the implementation of an artificial neural network (ANN) for the response of Nusselt number using various factors. The regression analysis for the embedding data shows the effectiveness of the proposed approach in this discussion. The proposed study describes the important outcomes as; an increasing slip produces a thinning in the bounding surface thickness for the case of pure fluid comparing to the nanofluid and hybrid nanofluid. Further, the data set used for the hybrid nanofluid shows an efficient fitting than the case of nanofluid.

Effect of topographical pattern on vortex shedding and heat transfer phenomena in power-law fluid flow around a rotating cylinder

The present numerical investigation studies the momentum and heat transfer phenomena from a heated rotating patterned cylinder in the vortex shedding regime. In particular, the effect of surface patterns ( ω , δ ), fluid behavior ( 0.4 ≤ n ≤ 1.6 ), cylinder rotation speed ( 0.5 ≤ α ≤ 2 ), and Prandtl number ( 1 ≤ Pr ≤ 100 ) at Reynolds number 100 on the force coefficients and Nusselt number are studied. Vorticity and isotherm profiles demonstrate the flow dynamics and heat transfer characteristics. According to the findings of this study, the formation of the vortex (including its size, shape, and number of vortices) and the time period during which the vortex shedding pattern repeats itself demonstrates a dependency on the shape of the cylinder, fluid behavior, and rotating speed. It has been noted that a significant decrease in the frequency of vortex shedding occurs on adding topographical patterns. Additionally, it has been noticed that on increasing rotational speed, vortex shedding can be suppressed for all fluid behaviors. Numerical simulation results reveal that the average drag coefficient ( C ¯ D ) for a rotating patterned cylinder decreases with increasing rotational speed ( α ), and it further reduces on increase in pattern frequency ( ω ) and amplitude ( δ ) compared to a smooth circular cylinder. The shear-thinning fluid behavior helps to dissipate the heat from the cylinder to the surrounding fluid. Conversely, shear-thickening fluid behavior exhibits the opposite trend.

Numerical Analysis of Effects of Vane Deflection Angle on Flow-Thermal Characteristics in a Fuel Rod Assembly

The utilization of a grid spacer with vane is a significant component within reactor fuel channels. The presence of the vane has a notable impact on the mixing of flow and the enhancement of heat transfer within subchannels. The purpose of this work was to perform a numerical analysis of the effects of the vane deflection angle on the flow-thermal characteristics in a fuel rod assembly. In the current analysis, a square array consisting of a 5 × 5 rod bundle was utilized. The pitch-to-rod diameter ratio was set to 1.33, while the blockage ratio of the grid spacer was determined to be 0.16. A relative study was made for flow-thermal characteristics with four different vane deflection angles, such as 21 deg, 25 deg, 29 deg, and 33 deg. Analyses were made for a fluid pressure of 15.5 MPa, an inlet temperature of 583 K, and a velocity of 4.74 m/s. The present study investigated the Shear Stress Transport (SST) k-ω and Renormalization Group (RNG) k-ε turbulence models to analyze flow phenomena and thermal performance. The numerical results were validated through experimental data and also compared with correlations proposed by researchers. The analysis of the results was carried out using various methods, including the examination of data curves and streamlines, as well as vector and contour plots. The results indicate that a higher deflection angle leads to a greater reduction in temperature at the grid spacer. The swirl ratio was observed to be maximum close downstream to the grid spacer, and the persistence of the swirl ratio in the downstream can enhance the performance of departure of nucleate boiling. The vane on the grid spacer with a higher deflection angle enhances the coefficient of heat transfer remarkably close to the downstream grid spacer.

Convective heat mechanism in Williamson nanoliquid over an escalating surface through an interface with viscous heating

This analysis explains the magneto-hydrodynamic flow on Williamson nanofluids previous stretching surface surrounded by the permeable media. The apt magnetic field was suggested for the angle of the axial direction of the flow. Anyhow, this flow phenomenon was characterized into the added heat source/sink and conjunction of radiating heat. The impacts of convective heating and viscous heating by expanding surface were again the significant feature of the analysis. This originality arises by the combination of the cross-diffusion effects of reverse behavior on the thermophoresis and Brownian motion. This form sketched into the aforesaid phenomenon was modified into the nonlinear ordinary form by the appropriate assumptions on comparison transformations. Therefore, the sets of equations were controlled for the numerical access using Lobatto-IIIa collocation method applicable to this Matlab bvp4c shooting process. This parametric performance of many components about their statistical values was given numerical imitations graphically by the rate coefficients in tabular forms. The validation and the compliance of the current result were acquired by the past study on the specific case. Further, the significant results of this analysis were: This non-Newtonian Williamson parameter combination of that magnetizing property diminishes the fluid velocities. In addition, the important influence of both viscosity parameter and radiation parameter of heating process was noted.

A Numerical Study on the Performance of a Pumping Station with Bell-Mouth-Based Vertical Pumps during an Accidental Shutdown

This study presents a numerical simulation of a pump’s performance during a power-cut event and connected hazards resulting from the failure of non-return flap valves. The vertical mixed-flow pumps with suction bells were mounted inside the suction basins of a pumping station. Different regimes of the pump operation during the time were analyzed based on the pump’s 4-quadrant characteristics and the dynamics of rotating parts in the pump, gearbox and electric engine. The resulting development of flow rates, rotor speed and forces in the course of time were used to analyze the hazards of failure of any pumping system component and the flooding of the suction object and its surroundings. The presented results show a deep insight into the flow phenomena in vertical mixed-flow pumps with suction bells during the runaway process and confirm that the developed methodology can be successfully applied to monitor the critical regimes in a pumping station in real time. The simulations were verified with some experimentally obtained data.

Numerical investigations on the impact of metallic foam configurations on heat transfer in double tube heat exchanger: A parametric approach

In this research, a parametric analysis of partially filled high-porosity metallic foams within a double-tube heat exchanger integrated into a solar flat plate collector is conducted. The primary objective is to comprehensively analyze the thermal and fluid flow behavior in this complex system through numerical simulations employing ANSYS Fluent v2021, with water as the working fluid. The study encompasses three distinct metal foam materials—Nickel, Copper, and Aluminum—each investigated across six cases with varying porosities (ranging from 0.80 to 0.90) and pore densities (ranging from 10 to 30). The investigation also explores changes in the internal diameter of the foams adjacent to the conduit wall and the external diameter of the foam within the tube core, resulting in multiple test cases. Rigorous validation of simulation results against experimental data enhances the credibility of the findings. To simulate fluid flow and heat transfer phenomena within the metal foam heat exchanger’s intricate geometry, the research leverages the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the k-epsilon model, treating the metal foam as a porous medium. The outcomes reveal intriguing insights, such as the close thermal performance match between 10 PPI aluminum foam and the more costly 10 PPI copper foam. The highest performance factor is observed for 30 PPI aluminum foam, highlighting its efficiency. However, the performance factor exhibits variations, with values of 2.03, 3.15, and 3.73 for 100 PPI, 20 PPI, and 30 PPI foams, respectively, and their corresponding porosities of 0.90, 0.85, and 0.80 in case 1, case 2, and case 3, all at a lower Reynolds number of 3,000. This performance factor decreases progressively with increasing fluid flow rates. Additionally, the research evaluates key parameters, including average wall temperature, average Nusselt number, and Colburn j factor, to identify the optimal performance characteristics within the investigated configurations. This study provides valuable insights into the potential for enhancing the efficiency of heat exchangers in solar flat plate collectors through the strategic utilization of high-porosity metallic foams.

A numerical investigation of the thermal characteristics of supercritical carbon dioxide (sCO2) flowing through mini serpentine channels

In this study, we numerically investigate the heat transfer characteristics of CO2 during phase transitions in its supercritical state in serpentine channels. Four different inclination angles are applied to three different radii of curvature flow channels with the same diameter of 2 mm. The supercritical state is maintained by assuming that the mass flux is approximately 191 kg/m2s, the inlet temperature is 298.15 K, and the operating pressure is 7.65 MPa. To ensure a consistent total heat input, different heat flux values are applied to the three different cases, eliminating the potential impact of the increased surface area on the heat transfer performance and allowing a clearer investigation of the geometric effects within the same temperature range. In a channel with a constant radius of curvature, the centrifugal force has a dominant influence on the heat flow compared to gravitational buoyancy, showing a flow phenomenon independent of the angle. In contrast, in a flow channel with a varying radius of curvature, the gravitational buoyancy fluctuates depending on the local area. As a result, the ratio of the centrifugal force to the gravitational buoyancy decreases, causing more variations with changes in the inclination angle. As the centrifugal force contributes significantly to turbulent mixing, the average heat transfer coefficient is highest in the flow channel with the shortest wavelength. As the wavelength increases, the ratio of centrifugal force to buoyancy begins to affect density stratification, especially in gas-like regions, leading to buoyancy. The local heat transfer coefficient at points around the circumference of the cross-section affected by buoyancy and in the film is analyzed, which is closely related to the centrifugal buoyancy and gravitational buoyancy, and their ratio. To express this influence in a correlation equation, a new Nu correlation with an error of less than 25 % is proposed using De, which combines the centripetal force and Reynolds number, ratio of centrifugal buoyancy and gravitational buoyancy, Ф, and Pr as.Nu=0.849De0.541∅-0.154Pr-0.160

Retrograde flow phenomenon of poly‐D,L‐lactic acid filler injection over lower eyelids

Retrograde flow phenomenon of poly‐D,L‐lactic acid filler injection over lower eyelids

Productivity, selectivity, and energy consumption of pilot-scale vacuum assisted air-gap membrane distillation for the desalination of high-salinity streams

The implementation of air gap membrane distillation systems is limited by a lack of overall performance predictions which rely on few available pilot-scale studies. This study evaluates the productivity, energy consumption, and selectivity of a pilot-scale air gap membrane distillation system by combining experiments and modeling activities. The effect of operating conditions, i.e., applied vacuum, feed flow rate, and feed stream salinity, was investigated to identify regulating factors and quantify dependencies. Response surface methodology was applied to model the phenomena and provide statistical analysis. Increasing flow rates produced a near linear increase of productivity within the investigated range. Operating at higher applied vacuum also translated into enhanced productivity, though the distillate flux increased by a maximum of 10 % when vacuum increased from −100 mbar to −500 mbar. Flow rate and vacuum also governed the observed salt flux by a similar magnitude because salt flux resulted mainly from liquid pore flow phenomena. The trans-membrane pressure regulated the membrane rejection: increasing the pressure difference led to a lower rejection. Moreover, high feed stream salinity lowered both the productivity and the distillate quality. The productivity gains were typically achieved at the expense of an increase in specific thermal energy consumption; however, an interesting relation was observed with feed stream salinity, with a minimum of specific thermal energy consumption of roughly 300kWhth⋅m−3 identified in the treatment of a stream with a salinity of 150g/L.

Turbulent transports in the flow around a rectangular cylinder with different aspect ratios

The flow around a rectangular cylinder exhibits intricate features, encompassing phenomena such as separation, reattachment, boundary layer transition, and relaminarization. This study explores the intense transport of turbulent fluctuations in these complex flow phenomena, including momentum and turbulent kinetic energy (TKE) transport, for three aspect ratios (L/D=5,10 and 15) at a medium Reynolds number (Re=1000). The connection between these transports and crucial vortical structures is elucidated for the first time. On the lateral side of the cylinder, strong momentum transport occurs, dominated by ejection and sweep events associated with the hairpin vortex. The generation of the LE vortex also leads to active TKE production. The existence of the LE separation bubble, as well as the relaminarization of the downstream boundary layer at L/D=10 and 15, affects the distribution of production terms. This perspective offers an effective yet novel approach that has not been previously addressed in prior researches. The redistribution of TKE results in a disturbance growth, linked to boundary layer transition. The source term reveals that streamwise TKE carried into the recirculating region is closely related to the frequency prior amplified by the LE shear layer. In the wake behind TE, turbulent transports are influenced by vortex shedding patterns.

On the Darcy–Forchheimer flow of carbon nanotubes nanofluid across a stretching surface for the impact of heat source/sink and Ohmic heating

This research leads to carrying out the productivity and the efficiency of the carbon nanotubes (CNTs) that have extensive applications in solar collectors. Due to the superior thermal as well as electrical properties, the use of CNTs has an important contribution to the nanotechnology revolution. Therefore, owing to the aforementioned vital points, this investigation intended to put forth the thermophysical properties of both single and multi-walled CNT nanofluids past a stretching surface. Additionally, an electrically conducting nanofluid flow phenomenon enriches due to the inclusion of dissipation (Ohmic heating) and external heat source/sink. The dimensional form of the three-dimensional fluid flow phenomena is transformed to a non-dimensional form with the use of similarity transformation and further numerical procedure is implemented to solve the nonlinear governing equations. The substantial significance of the characterizing parameters is presented briefly via figures and the comparative analysis with the earlier investigation is deployed through the table. However, the main findings of this study are as follows: A significant attenuation in the shear rate is marked for the enhanced inertial drag but it augments for the augmented values of the magnetization; further, particle concentrations of both the CNTs favor accelerating the fluid momentum as well as temperature distribution.

Scale-dependent wetting behavior of bioinspired lubricants on electrical discharge machined Ti6Al4V surfaces

The relationships between the geometric features of material surfaces and topographically related phenomena, such as wetting, change with the scale of observation. In these studies, multiscale analyzes allow characterizing the relationships between electrical discharge machining parameters, complex surface topographic structures and contact angles. Importantly, it was possible to indicate the best scales for observing the phenomena of lubricant flow on electro-discharged surfaces and to identify key geometric parameters of the surface affecting the contact angle. This paper proposes scale-dependent contact angle analyzes of electro-discharge machined Ti6Al4V alloy for biomedical implant applications. Liquids imitating synovial fluid in joints were used as lubricants. The research focuses on comparing the impact of discharge energy on surface microtexture, chemical composition, contact angle and surface free energy. The analysis of the lubrication behavior on micro-textured surfaces in contact mechanics co-determines the tribological properties. The research results confirm the effectiveness of modeling the specific wettability of implant surfaces with bioinspired lubricants.

Backward flow and jet formation of liquid and granular medium in a gravity drainage system following a sudden valve closure

The sudden closure of a valve during the gravity-driven drainage of the liquid or granular medium causes the backward flow of material and generates a strong backward pressure wave. The phenomenon, which has a strong similarity with classical water hammer, is reported for the first time. Under specific conditions, the formation of the jet is observed at the free surface. The current article presents a detailed computational investigation of the unique phenomenon of backward propagation of materials and jet formation. A detailed comparison of the flow phenomenon for liquid and granular medium of constant bulk density is reported providing a particular emphasis on jet formation in these two cases. Distinct stages of flow dynamics are observed particularly for granular medium. For liquid, the runout time for the jet formation has been quantified analytically to appreciate the energy dissipation. The analytical model also produces good agreement (+10.75%, −8.9%) with the trained model based on numerical results. A detailed parametric study is incorporated for aspect ratio and valve height ratio to characterize and compare the phenomenon for both the flowing medium, − liquid, and granular matter.

A Banach spaces-based fully mixed virtual element method for the stationary two-dimensional Boussinesq equations

In this paper we extend recent results obtained for the Navier–Stokes equations to propose and analyze a new fully mixed virtual element method (mixed-VEM) for the stationary two-dimensional Boussinesq equations appearing in non-isothermal flow phenomena. The model consists of a Navier–Stokes type system, modeling the velocity and the pressure of the fluid, coupled to an advection-diffusion equation for the temperature. The variational formulation is based on the introduction of the additional unknowns given by a modified pseudostress tensor, which depends on the pressure, and the diffusive and convective terms of the fluid, and the pseudoheat vector, which involves the temperature, its gradient, and the velocity. As a consequence of the former, the pressure is eliminated from the system, but computed afterwards via a post-processing formula. In turn, for the Galerkin approximation we follow the approach employed in a previous work introducing for the first time an Lp spaces-based mixed-VEM for the Navier–Stokes equations, and couple it with a similar mixed-VEM for the convection–diffusion equation modeling the temperature. The solvability analysis of the resulting coupled discrete scheme is carried out by using appropriate fixed-point arguments, along with the discrete versions of the Babuška–Brezzi theory and the Banach-Nečas-Babuška theorem, both in subspaces of Banach spaces. The first Strang lemma is applied to derive the a priori error estimates for the virtual element solution as well as for the fully computable approximation of the pseudostress tensor, the pseudoheat vector, and the post-processed pressure. Finally, several numerical results, illustrating the performance of the mixed-VEM scheme and confirming the rates of convergence predicted by the theory, are reported.

Sounding Mechanism of a Flue Organ Pipe-A Multi-Sensor Measurement Approach.

This work presents an approach that integrates the results of measuring, analyzing, and modeling air flow phenomena driven by pressurized air in a flue organ pipe. The investigation concerns a Bourdon organ pipe. Measurements are performed in an anechoic chamber using the Cartesian robot equipped with a 3D acoustic vector sensor (AVS) that acquires both acoustic pressure and air particle velocity. Also, a high-speed camera is employed to observe the jet coming out from the windway. For that purpose, the steam resulting from dry ice and hot water is used. A numerical simulation of the sounding mechanism of a pipe of the same geometry is based on measuring the pressure signal and the intensity field around the mouth employing an intensity probe and visualizing and observing the motion of the air jet, which represents the excitation mechanism of the system. The ParaVIEW software serves for the simulation and visualization of the air jet. Then, the results obtained from measurements and simulations are compared and discussed. Also, some future directions discussing the application of a machine-learning approach to the area of pipe organ air flow investigation are contained in the Conclusions section.

Multiscale Modeling of Flow in Rod Bundles: From Direct Numerical Simulation and Subchannel to Coarse-Mesh CFD

Fast and accurate evaluation of flow and heat transfer phenomena in rod bundles is a problem of long-standing interest in nuclear engineering. Computational fluid dynamics (CFD) can provide accurate but relatively time-intensive estimates, such that simulations of very long transients with high spatial detail are infeasible. On the other hand, subchannel codes require relatively low computational time and can provide pin-level estimates, but have substantial empiricism in evaluating aspects such as crossflows and turbulent mixing coefficients. A multiscale method (SC+) for bridging this accuracy/speed gap, based on the Subchannel CFD (SubChCFD) method of Liu et al. [Nucl. Eng. Design, Vol. 355, paper 110318 (2019)], is demonstrated and developed here with a focus on a 5 × 5 square rod bundle geometry. The method has been newly implemented into the commercial code STAR-CCM+ and benchmarked against Liu et al.’s data. The 5 × 5 geometry was chosen in part due to the availability of direct numerical simulation (DNS) data at a relevant Reynolds number of a similar configuration for comparison. The SC+ results are variously compared against results from DNS, large eddy simulation, wall-resolved Reynolds-averaged Navier-Stokes, and coarse-mesh CFD methods. As an expansion to the original SubChCFD approach, a simple Hi2Lo approach is demonstrated using the DNS data as a correction to the original friction factor correlations employed. This is verified to improve the predictions. Additional test cases with geometric perturbations are pursued, illustrating the flexibility of SC+. The potential of this method for modeling the narrow gap vortex instability, which would represent an advancement over standard subchannel approaches, is also assessed. The method is expanded to include transverse flow losses, which was found to improve the results for modeling the gap instability. Initial extensions of SC+ for hexagonal rod bundles are also presented; some inaccuracies for the coarsest meshes prompted a detailed investigation of the mesh convergence behavior of the method. Geometric correction factors were devised that provided substantial improvement on these very coarse meshes, improving the prospects of SC+ for wider usage. Future work plans are to expand the methodology to wire-wrapped rod bundles and to implement the method into Pronghorn, with a unified pipeline via the Cardinal wrapper between the codes NekRS, Pronghorn, and BISON, to solve fuel performance problems of direct interest to industry.