Wide Reynolds Number Range Research Articles

Acoustic viscous boundary layer beyond laminar regime: Particle Image Velocimetry measurements

The current study reports an experimental investigation of flow regimes for acoustically oscillating flows in the near-wall region of a resonator. Particle Image Velocimetry (PIV) is used to measure axial and transverse velocity components inside an empty square resonator over the acoustic cycle for a wide range of Reynolds numbers and at a high Womersley number. The measurements are compared with LDV measurements in a circular duct. A good agreement between the PIV and LDV measurements is observed. The measured transverse distribution of the axial velocity agrees well with the Stokes boundary layer expectations up to the Reynolds number (based on acoustic velocity and viscous boundary layer depth) of 240. At higher Reynolds numbers, the measured velocity distribution deviates from the theoretical expectations, suggesting a change of regime at a Reynolds number between 240 and 272. To assert the critical Reynolds number, the velocity fluctuations and Reynolds stress are estimated. At Reynolds number of 272, an increase in the value of the Reynolds stress is observed at the edge of the viscous penetration depth which is regarded as an indication of changing the flow regime. To better qualify the high amplitude acoustic flow, the spectrum of the turbulent kinetic energy and evolution of the integral length scale over the acoustic cycle are investigated. The decay of turbulent kinetic energy with the wavenumber complies with the universal slope (−5/3). The integral length scale increases during the deceleration stage and decreases at the beginning of the acceleration stage.

Performance enhancement of a C-shaped printed circuit heat exchanger in supercritical CO2 Brayton cycle: A machine learning-based optimization study

The present work is focused on enhancing the overall thermo-hydraulic performance of a previously proposed C-shaped printed circuit heat exchanger (PCHEs) using Machine Learning (ML) Algorithms. In this context, CFD analysis is carried out on 81 different channel configurations of the C-shaped channel geometry, and computed data is used to train three ML algorithms. Later, C-shaped channel geometry is optimized by coupling the trained ML model with the multi-objective genetic algorithm (MOGA). Finally, the optimized channel geometry (called optimized ML ) is investigated numerically for a wide range of Reynolds numbers. Its performance is compared with the zigzag geometry, C-shaped base geometry, and previously optimized C-shape channel geometry using response surface methodology (RSM). The findings showed that the multilayered approach combining MOGA, CFD, and machine learning techniques is beneficial to accomplish a robust and realistic optimized solution. Comparing the thermo-hydraulic characteristics of the optimized ML channel geometry with zigzag channel geometry shows that the former is up to 1.24 times better than the latter based on the performance evaluation criteria (PEC). Furthermore, the overall performance of the optimize ML channel geometry was found up to 21% and 16% higher than the optimized RSM geometry on the cold and hot sides, respectively.

Investigation of the cavitation processes behind a cylinder located in a microchannel in a wide range of Reynolds numbers

Numerical modeling and experimental investigation of hydrodynamic cavitation on a microcylinder located in a microchannel were carried out. The Zwart–Gerber–Belamri cavitation model was employed to simulate cavitation processes, and turbulence was simulated using the LES model. Experimental studies were performed by visualization with a shooting frequency of 960 Hz. Fluid pressure at the channel inlet ranged from 2 to 30 bar. Time dependences of pressure, velocity and vapor volume fraction, as well as their average values, were obtained at five points. Stable developed cavitation was found to exist for inlet pressures above 18 bar; no cavitation at all was observed for inlet pressures below 8 bar as confirmed by experimental studies. A fairly good agreement was revealed between the calculated and experimental data. The cavitation pulsation frequency (480–2200 Hz) and hydrodynamic pulsation frequency values (26–96 kHz) were obtained. The presence of cavitation was shown to shift the frequency of hydrodynamic pulsations towards larger values. Dependence of the relative drag coefficient on the inlet pressure, well approximated by a correlation ζ r = (2Δp) 0.5 , was obtained.

Temperature-dependent droplet impact dynamics of a water droplet on hydrophobic and superhydrophobic surfaces: An experimental and predictive machine learning–based study

• Droplet impact on microstructured surfaces (hydrophobic/superhydrophobic) at different temperatures has been studied. • Effect of velocity, droplet diameter, temperature, surface wettability and roughness on impact dynamic are evaluated. • Using three machine-learning algorithms, an innovative method for predicting droplet impact dynamic is presented. Heightening the water repellency of surfaces can serve anti-icing purposes by removing water drops before they freeze and adhere to a surface. Here we study the impact dynamics of water droplets on silicone rubber surfaces—ranging from hydrophobic to superhydrophobic—at −20, −10, and 25 °C. We evaluate the influence of static contact angle, contact angle hysteresis, surface roughness, temperature, impacting velocity, and droplet diameter on droplet behavior (e.g., deposition, bouncing, splash). Minor effect of temperature on droplet dynamics on microstructured surfaces for a wide range of Weber and Reynolds numbers is observed. Experimental observations show that full bouncing only occurs on superhydrophobic surfaces with a CA > 160° and a CAH < 2° at temperatures above 0 °C for We < 110 and Re < 5000. Increasing the impact velocity of the droplet on rough surfaces heightens the probability of splashing. This experimental data is then coupled with machine-learning techniques (logistic regression, decision tree, and random forest) to comprehensively investigate droplet impact behavior on hydrophobic and superhydrophobic surfaces at various temperatures. We predict the behavior probability of impacting droplets on surfaces as a function of Weber number, Reynolds number and surface features (static contact angle, contact angle hysteresis, temperature, and surface roughness). Our experimental results and machine learning–based predictions are highly consistent, demonstrating that machine learning can effectively predict droplet motion on hydrophobic and superhydrophobic silicone rubber surfaces at different temperatures.

Interaction between a complex fluid flow and a rotating cylinder

The flow of a thixotropic Bingham material past a rotating cylinder is studied under a wide range of Reynolds and Bingham numbers, thixotropic parameters, and rotational speeds. A microstructure transition of the material involving breakdown and recovery processes is modeled using a kinetic equation, and the Bingham- Papanastasiou model is employed to represent shear stress-strain rate relations. Results show that the material’s structural state at equilibrium depends greatly on the rotational speed and the thixotropic parameters. A layer around the cylinder resembling a Newtonian fluid is observed, in which the microstructure is almost completely broken, the yield stress is negligibly small, and the apparent viscosity approximates that of the Newtonian fluid. The thickness of this Newtonian-like layer varies with the rotational speed and the Reynolds number, but more significantly with the former than with the latter. In addition, the lift and moment coefficients increase with the rotational speed. These values are found to be close to those of the Newtonian fluid as well as of an equivalent non-thixotropic Bingham fluid. Many other aspects of the flow such as the flow pattern, the unyielded zones, and strain rate distribution are presented and discussed.

Investigation of micromixing in the ART plate reactor PR37 using the acetal cleavage method and different mixing models

The mixing time can strongly affect the yield of a desired product if side reactions occur. Mixing is therefore of great practical importance. Millireactors enable comparatively high flow rates at moderate pressure drops and are thus well suited for production purposes. In this work, the mixing performance of the millistructured reactor ART PR37 is investigated using the Bourne method. Four plate types with similar meandering, converging/diverging process channels, but different hydraulic diameters have been studied over a wide range of Reynolds numbers. Mixing times have been calculated using two different mixing models, the IEM model and a recently introduced modified incorporation model. Mixing times were found to be less than 0.1 second for Reynolds numbers exceeding 150. For higher Reynolds numbers, mixing times in the range of 0.02 to 0.03 s are achievable without prohibitively high pressure drops. The ART PR37 is therefore a promising option for mixing-sensitive reactions.

Flow Estimation by Flow Induced Vibration of Bluff Bodies

The study confirms the feasibility of using information from flow-induced vibration generated by bluff bodies for measurement of flow. The proposed methodology is based on experiments conducted for recording acceleration signals from vibration sensors embedded along with bluff bodies in cross flow. The studies were undertaken in a wide Reynolds number range of 4700 to 5.655x105, with five different geometries of bluff bodies for shape optimization. Resonance and vortex shedding frequencies of samples are determined experimentally. The recorded acceleration signals are analysed using three different techniques such as frequency shift method, resonance amplitude method and overall acceleration estimation method. In this, the frequency shift method shows correlation at low flow velocities. In the resonance amplitude method and overall acceleration method, acceleration levels show a cubic relation with the flow rate. In the resonance amplitude method, obtained R2 values are from 0.93 to 0.99. Overall acceleration estimation method has shown better correlation with flow rate and its R2 values were above 0.99. The study confirms that application of all three methods together yields reasonably good estimation for a wide range of flow.

Mixing Performance of a Planar Asymmetric Contraction-and-Expansion Micromixer.

Micromixers are one of the critical components in microfluidic devices. They significantly affect the efficiency and sensitivity of microfluidics-based lab-on-a-chip systems. This study introduces an efficient micromixer with a simple geometrical feature that enables easy incorporation in a microchannel network without compromising the original design of microfluidic devices. The study proposes a newly designed planar passive micromixer, termed a planar asymmetric contraction-and-expansion (P-ACE) micromixer, with asymmetric vertical obstacle structures. Numerical simulation and experimental investigation revealed that the optimally designed P-ACE micromixer exhibited a high mixing efficiency of 80% or more within a microchannel length of 10 mm over a wide range of Reynolds numbers (0.13 ≤ Re ≤ 13), eventually attaining approximately 90% mixing efficiency within a 20 mm microchannel length. The highly asymmetric geometric features of the P-ACE micromixers enhance mixing because of their synergistic effects. The flow velocities and directions of the two fluids change differently while alternately crossing the longitudinal centerline of the microchannel, with the obstacle structures asymmetrically arranged on both sidewalls of the rectangular microchannel. This flow behavior increases the interfacial contact area between the two fluids, thus promoting effective mixing in the P-ACE micromixer. Further, the pressure drops in the P-ACE micromixers were experimentally investigated and compared with those in a serpentine micromixer with a perfectly symmetric mixing unit.

Experiments on the Drag and Lift Coefficients of a Spinning Sphere

The drag and lift coefficients are important parameters that affect the particle motion in a viscous fluid. In the present study, the drag and lift coefficients of a spinning sphere in a water tank were studied experimentally using a high-speed camera. To this end, 22 cases were studied to cover a wide range of dimensionless angular speeds (0.149 &lt; Rr &lt; 3.471) and Reynolds numbers (610 &lt; Re &lt; 3472). Based on the present experimental data and the results obtained from the literature, expressions were developed to calculate the lift and drag coefficients. The performed analyses on lift coefficient show that there is a critical Reynolds number (Rec) at each dimensionless angular speed. When 0 &lt; Re &lt; Rec, the lift coefficient decreases with increasing the Reynolds number, while it is constant when Rec &lt; Re&lt; 3500. The constant lift coefficient corresponding to different spin speeds was defined as the limit value of the lift coefficient. It is found that when 1 &lt; Rr &lt; 12, the limit value of the lift coefficient is 0.37, while the limit value of the lift coefficient increases with increasing dimensionless angular speed at 0 &lt; Rr &lt; 1. It is found that the spin increases the drag coefficient of a spinning sphere only when 0 &lt; Rr &lt; 10. Moreover, the performed analyses show that the drag coefficient of a spinning sphere is less than that of a non-spinning sphere when 10 &lt; Rr &lt; 25. Furthermore, the lift-to-drag ratio of a spinning sphere is discussed in this article.

Anisothermal flow dynamics in ventilated open space involved with indoor comfort

Energy cooling systems or thermal buildings are increasingly fertile subject for reducing the energy demand or for the indoor air quality coupled with energy demand. This work is devoted to studying cooling ability within an open domain. The space model is considered as a cavity heated on one external sidewall and cooled by three vertical boards which separate the room into four sub-domains. A complex flow structure is obtained in the present “cooperating” case, in which dynamic and buoyancy forces are added together on the active wall. It shows that the natural convection and the forced flow (injection) act directly on the resulting patterns, heat exchange, mixing ability, which control the thermal field homogeneity and the cooling necessity. The computation results show the influence of the parameters and the vertical boards on heat transfer in the enclosure. Under the wide range of Rayleigh (Ra) and Reynolds (Re) numbers, the features of dynamic and thermal fields permit to categorize the different convection phenomena. The intensity of mixing was quantified versus Ra and Re and we find the conditions and threshold of the different domains (diffusive, natural, forced and mixed convection).

Numerical analysis of the three-dimensional flow phenomena in a 19-pin wire-wrapped tight lattice bundle

The wire-wrapped tight lattice assembly has the advantages of compact arrangement, small volume, and high power density, and it has been widely used in the design of advanced nuclear reactors. A wire-wrapped tight lattice assembly has been proposed at Shanghai Jiao Tong University, and the mixing characteristics of this assembly have been experimentally investigated in a 19-pin wire-wrapped bundle in the previous work. In the present study, the numerical simulation for this bundle based on the Reynolds-Averaged-Navier-Stokes SST k-ω model has been carried out, and the numerical method was verified by the mixing experiment data. Then the three-dimensional flow phenomena have been discussed for a wide range of Reynolds numbers from 5843 to 100,000. The axial flow split parameters, vortex behaviors in cross-section, and the flow sweeping behaviors in subchannel gaps were analyzed in a typical condition, and the effect of the Reynolds number also has been discussed, which shows little effect on these parameters. This study is a continuation of our previous work, and they both aim to provide a reference for the design of wire-wrapped tight lattice assembly.

Amplification of Transverse Reynolds Stresses in Shock–Turbulence Interactions

The amplification of transverse Reynolds stresses in shock–turbulence interactions is studied at a wide range of Mach and Reynolds numbers using well-resolved direct numerical simulations. Data show that the Reynolds stresses change significantly across the shock with a clear dependence on characteristics of the turbulence upstream of the shock, an effect not captured by classical theories. Budget analysis shows that pressure–dilatation and dissipation dominate the transport of the transverse stresses, which are further analyzed in the context of linear analysis. Data suggest that amplification factors for transverse stresses follow -scaling in both wrinkled and broken regimes. Unlike the amplification of streamwise stresses, no transition is observed to a regime where transverse stresses depend solely on the mean Mach number, at least for the conditions studied here. Possible explanations are discussed.

THE INFLUENCE OF DIFFERENT FACTORS ON THE MAISOTSENKO CYCLE EFFECTIVENESS

An important problem in the heat industry is the significant cost of energy resources for air conditioning. Therefore, energy-efficient refrigeration systems based on renewable energy sources and evaporative air cooling, as well as air-conditioning systems according to the Maisotsenko cycle using psychrometric energy of the environment are of great importance. This paper presents the results of experimental and numerical research of the influence of various factors on the efficiency of indirect evaporative heat and mass transfer apparatus on the M-cycle on the basis of a new unit cell.&#x0D; An experimental stand of a heat and mass transfer apparatus with vertically arranged plate channels was developed for experimental research. Experimental studies of heat and mass transfer in the new unit cell were conducted in a wide range of Reynolds numbers 200…1200, temperature 16… 30 °С, relative humidity 30… 50 %. The calculated study was performed using a modified ε-NTU method. Studies have shown that the thermodynamic efficiency of a wet bulb thermometer at a Reynolds number below 500 exceeded one. According to the results of computational studies, the influence of cell length and surface intensification of dry channels on thermodynamic efficiency was determined. Shown the effect of changes in thermodynamic efficiency in the range of 86…94 % increase in efficiency by 1 % leads to an increase in cell length by 7 %. The value of the enhancement factor increases with increasing air flow regime, so when the heat and mass transfer surface area increases by 50 % and the Reynolds number 200, the thermodynamic efficiency increases by 14 %, and with the Reynolds number 800 – by 28 %. The dependence of the thermodynamic efficiency of the cells at the dew point on the relative humidity of the inlet air have a maximum, which with increasing Reynolds number shifts toward larger values of relative humidity.&#x0D; Unlike traditional air conditioning devices, the M-cycle heat and mass exchanger does not use a steam compression cycle, so energy costs are spent only on the operation of the fan to pump air, which is a more environmentally friendly and energy efficient way of air conditioning.

Numerical validation of simple non-stationary models for self-propelled pitching foils

High-resolution numerical simulations of the self propelled locomotion of two-dimensional pitching foils are used to assess simplified models based on linear potential theory for the fluid-foil interaction. These models are very useful because they provide simple analytical estimations of the swimming velocity, among other relevant features of the aquatic locomotion of fishes and underwater robotic devices propelled by flapping foils. In particular, we consider a pitching foil self-propelled from two different models of the unsteady thrust force based on linear potential theory, both complemented with a new simple model for the unsteady viscous friction obtained from the present full-numerical simulations, valid in a wide range of Reynolds numbers (103≲Re≲104) of interest for many natural and robotic swimmers. The resulting ordinary differential equation for the swimming velocity is easily integrated numerically, comparing favorably with the full-numerical simulations for small pitch amplitudes (Strouhal numbers St≲0.25) and the above range of Reynolds numbers. Further, when the swimming velocity is small, simple approximate solutions of the dynamic model equation are obtained, whose pitch amplitude validity range is more limited than the numerical solution of the model as the Reynolds number and the foil mass ratio increase, becoming negligibly small when the frequency-based Reynolds number is well over 104. Although both thrust models yield similar quantitative results, they predict qualitatively different dependencies of the swimming velocity on the different non-dimensional parameters.

A Lagrangian roughness model integrated with the vortex method for drag coefficient estimation and flow control investigations around circular cylinder for a wide range of Reynolds numbers

A Lagrangian roughness model integrated with the vortex method for drag coefficient estimation and flow control investigations around circular cylinder for a wide range of Reynolds numbers

Thermal-hydraulic performance of additively manufactured lattices for gas turbine blade trailing edge cooling

• Thermal-hydraulic performance of four lattice frame materials, namely, Octet, Tetrakaidecahedron, Face diagonal-cube, and Cube is studied for turbine edge cooling application. • Face diagonal-cube provided the highest heat transfer coefficient and pressure drop values amongst the investigated samples at similar porosity values and unit cell size. • Cube topology yielded the lowest flow losses and consequently highest thermal–hydraulic performance of ∼ 2.78 at the lowest investigated Reynolds number. Gas turbine blade trailing edge cooling is challenging because of the stringent geometrical constraints driven by aerodynamics and thermal stresses. The blade topology becomes significantly thin towards the trailing edge which leaves a narrow room for the construction of internal cooling channels and also makes this section susceptible to failure due to thermal stresses. Conventionally, pin-fins are employed in the internal cooling channels of the trailing edge because they provide high levels of heat transfer coefficient values and also structural integrity. Much of the past studies on pin fins have focused on their relative arrangements, heights, crossflow scheme, etc., with an aim to enhance the endwall heat transfer coefficient as well as leverage the conjugate heat dissipation capabilities of these “extended surfaces”. Lattices on the other hand, have been investigated to a lesser degree, and some studies can be found for blade mid-chord region, however, with their manufacturability challenges at that time, the concepts did not gain traction. Lattices are far more complex topologies with superior local heat transfer characteristics as well as high conjugate heat dissipation capabilities due to large wetted surface area. With the recent advancements in metal additive manufacturing, complex topologies such as lattices can be revisited due to high chances of their realization now. To this end, we are presenting our study on lattices additively manufactured in 420 Stainless Steel (thermal conductivity nearly twice of Inconel 718), where four different unit cell topologies, (a) Octet, (b) Tetrakaidecahedron, (c) Face diagonal-cube, and (d) Cube, were printed using Binder Jetting technology. The aim of this study is to characterize the conjugate heat transfer capabilities of these lattices manufactured in 420 Stainless Steel prior to conduct similar study with Inconel 718, due to relatively simpler additive manufacturing route of Binder jetting (420 stainless steel) compared to Direct Metal Laser Sintering (Inconel 718). The intended design porosity of the samples was 0.886 and the coupons had single unit cell (edge size of 10 mm) in the thickness. The steady-state experiments were conducted to evaluate the effective thermal conductivity and forced convective heat transfer performance. For forced convection, the experiments were conducted for a wide range of Reynolds numbers with air as the working fluid. Overall heat transfer coefficient, pressure drop, Nusselt number and friction factor enhancement level and pumping power requirements of these structures are presented. The implications of the porosity variation due to manufacturing process on the interpretation of relative performance trends is discussed. The effective thermal conductivity was independent of the topology for considered porosity value. Face diagonal-cube yielded the highest heat transfer and pressure drop for the investigated Reynolds number range. However, Cube provided the best overall thermal hydraulic performance value of 1.94 to 2.78 for the investigated range of Reynolds number. At fixed pumping power conditions, Cube was capable of providing the highest heat transfer coefficient.

Mesoscopic simulations of inertial drag enhancement and polymer migration in viscoelastic solutions flowing around a confined array of cylinders

We study the flow around a periodic array of cylinders using a mesoscopic viscoelastic fluid that mimics polymeric solutions. We model our fluid employing a novel mesoscopic method based on Smoothed Dissipative Particle Dynamics and FENE springs. We characterize the static and dynamic properties of our model solutions and compare the results with theoretical predictions based on the Zimm model. After rheological characterization of the modeled solutions, we simulate the flow around a confined array of cylinders. The balance between inertia and elasticity in our simulations is studied using a wide range of Reynolds (Re) and Weissenberg (Wi) numbers. We find that increasing the flow rate reduces the drag coefficient on the cylinder up to a critical Re corresponding to a minimum. Thereafter, inertia becomes dominant and we encounter drag enhancement for all the solutions studied, including the Newtonian solvent. With the use of simple model for the viscous and inertial contributions to drag, we conclude that inertial effects are driving the increase in the drag experienced by the cylinder. In our simulations, we also observe migration of polymer chains away from the channel walls and in the wake of the cylinder. We conclude that stress gradients induced by the curvature of streamlines and convection of the depleted layers at the walls as the principal mechanisms driving the migration of chains. We find the extent of the migration correlates well with the viscoelastic Mach number (Ma = Re Wi ) suggesting that both elastic and inertial effects play a role in this phenomenon. • A mesoscopic model fluid with viscoelastic behavior is presented. • The drag on a confined array of periodically spaced cylinders is investigated. • Drag enhancement is explained with a simple model combining inertial and viscous drag. • Polymeric migration at the walls and the wake of the cylinders is investigated.

A new boundary layer integral method based on the universal velocity profile

A recently developed mixing length model of the turbulent shearing stress in wall bounded flows has been used to formulate a universal velocity profile (UVP) that provides an effective replacement for the widely used Coles wall-wake formulation. Comparisons with both direct numerical simulation and experimental data demonstrate the ability of the profile to approximate a wide variety of wall-bounded flows. The UVP is uniformly valid from the wall to the boundary layer edge and for all Reynolds numbers from zero to infinity. There is no presumption of logarithmic dependence of the velocity profile outside the viscous wall layer so the profile can accurately approximate low Reynolds number turbulent boundary layers. The effect of a pressure gradient is included in the UVP through the introduction of a modified Clauser parameter that correlates well with the parameters that determine the wake portion of the velocity profile. The inherent dependence of the UVP on Reynolds number, extended to include the effect of pressure gradient, enables it to be used as the basis of a new method for integrating the von Kármán boundary layer integral equation for a wide variety of attached wall bounded flows. To illustrate its application, the UVP is used to determine the zero-lift drag coefficient of the Joukowsky 0012 and NACA (National Advisory Committee for Aeronautics) 0012 airfoils over a wide range of chord Reynolds numbers.

Numerical Analysis of a Planar O Micromixer with Obstacles

Passive mixers rely on the channel geometry to mix fluids and mixing depends primarily on diffusion. However, many previously reported designs either work efficiently only at moderate to high Reynolds numbers (Re) or require a complex 3D channel geometry that is often difficult to fabricate. In this paper, we report the design, simulation, and characterization of a planar O passive microfluidic mixer with two types of obstacles to enhance mixing performance. Numerical investigation on mixing and flow structures in microchannels is carried out using the computational fluid dynamics (CFD) software ANSYS 15 for a wide range of Reynolds numbers from 1 to 200. The results show that the O mixer with obstacles has far better mixing performance than the O mixer without obstacles. The reason is that fluid path length becomes longer due to the presence of obstacles which gives fluids more time to diffuse. For all cases, the O mixer with circular &amp; fin obstacles have 3 times more efficient compared to the O mixer without obstacles. It is also clear that efficiency increase with axial length as expected. Efficiency can be simply improved by adding extra mixing units to provide adequate mixing. The value of the pressure drop is the lowest for the O mixer because there is no obstacle inside the channel. However, the O mixer with circular &amp; fin obstacles has the lowest mixing cost, an important characteristic for integration into complex, cascading microfluidic systems, which makes it the most cost-effective mixer. Due to the simple planar structure and low mixing cost, it can be easily realized and integrated into devices for various macromixing applications.

Modeling of Lateral Flow in CFD for Subchannel Analysis

This paper is aimed at the application of computational fluid dynamics (CFD) calculations for lateral flow modeling in rod bundles of Russian-type pressurized water reactors with hexagonal fuel rod lattice by subchannel analysis under a constant temperature. The subchannel code SUBCAL and CFD code ANSYS Fluent with the Reynolds stress turbulence model, which is capable of solving the anisotropic flow present in rod bundles, are used. Both methods are compared in terms of calculations in rod bundles. The literature review of available experiments of rod bundles suitable for CFD calculation validation follows. This paper describes the created CFD models on a triangular lattice, which are subsequently validated on selected experimental data in a wide range of Reynolds numbers and geometry (pitch-to–rod diameter ratio) together with mesh sensitivity analysis. The main part of this work is to develop a new equation for the lateral flow resistance coefficient for the subchannel code based on CFD calculations. Within these calculations, the turbulent mixing coefficient β for hydraulically smooth rod bundles, which is related to the geometry, and the momentum-energy transfer analogy correction factor ε are also evaluated and for which the equation is subsequently proposed.