Reynolds Number Effects Research Articles

Wind Tunnel Tests of a Thick Wind Turbine Airfoil

ABSTRACTThis article reports about a wind‐tunnel experiment carried out in the ONERA F2 low‐speed wind tunnel on a model of the DU 97‐W‐300Mod airfoil designed for wind turbine application. The wind tunnel, the airfoil model, and experimental techniques used are presented, with special emphasis on the data processing and corrections required to derive airfoil forces and pressure distribution. To better document the flow physics at play, the results are illustrated by infrared thermography and surface oil flow visualization. The test allowed investigating Reynolds number effects between 1 and 3.8 millions. To ameliorate the understanding of the benefits and limitations of such airfoil testing, one section is devoted to the comparison of present results with previous experiments in other wind tunnels. Some of the difficulties arising in airfoil testing are evidenced and discussed to contribute to the improvement of test methods.

Reynolds number effects in shock-wave/turbulent boundary-layer interactions

We investigate Reynolds number effects in strong shock-wave/turbulent boundary-layer interactions (STBLI) by leveraging a new database of wall-resolved and long-integrated large-eddy simulations. The database encompasses STBLI with massive boundary-layer separation at Mach $2.0$ , impinging-shock angle $40^{\circ }$ and friction Reynolds numbers ${\textit {Re}}_\tau$ $355$ , $1226$ and $5118$ . Our analysis shows that the shape of the reverse-flow bubble is notably different at low and high Reynolds number, while the mean-flow separation length, separation-shock angle and incipient plateau pressure are rather insensitive to Reynolds number variations. Velocity statistics reveal a shift in the peak location of the streamwise Reynolds stress from the separation-shock foot to the core of the detached shear layer at high Reynolds number, which we attribute to increased pressure transport in the separation-shock excursion domain. Additionally, in the high Reynolds case, the separation shock originates deep within the turbulent boundary, resulting in intensified wall-pressure fluctuations and spanwise variations associated with the passage of coherent velocity structures. Temporal spectra of various signals show energetic low-frequency content in all cases, along with a distinct peak in the bubble-volume spectra at a separation-length-based Strouhal number $St_{L_{sep}}\approx 0.1$ . The separation shock is also found to lag behind bubble-volume variations, consistent with the acoustic propagation time from reattachment to separation and a downstream mechanism driving the shock motion. Finally, dynamic mode decomposition of three-dimensional fields suggests a Reynolds-independent statistical link among separation-shock excursions, velocity streaks and large-scale vortices at low frequencies.

Reynolds number effect on the Lagrangian evolution of hairpin vortices in turbulent channel flow

The evolution and generation of hairpins are studied in a Lagrangian perspective in turbulent channel flows. Direct numerical simulation database of turbulent channel flow at friction Reynolds numbers R e τ = 590, 390, and 180 is employed to perform tracking and interpolation algorithms of fluid particles on hairpins. These particles are carefully selected using a vortex line identification technique developed to extract the hairpin's core line. Interesting results are observed regarding the Reynolds number impact on the evolution and regeneration of hairpins. As the Reynolds number increases, the head and the vortical tongues are compressed and aligned in the main flow direction and the hairpin structures tend to orient more horizontally. The deformation shape of hairpins using the strain state parameter, which is correlated with the dissipation rate, is analysed using the probability density function. Most phenomena related to the generation of secondary hairpins, including the existence of vortical tongues, occur in the range 35 ≲ y + ≲ 50 . The results reveal that the Lagrangian perspective is a proper technique to address the extension of vortical tongues, generation of the secondary hairpin, and stretch of hairpin legs.

Reynolds number sensitivity of the vortex dynamics around a long-span rail-cum-road bridge girder with three separated boxes

The novel separated three-box girder is gradually adopted for very long-span cable-stayed bridges due to its excellent flutter stability. Due to its special design of cross section, it exhibits notable Reynolds number effects in the flow patterns and vortex dynamics when subject to incoming flow. To explore its Reynolds number sensitivity, this paper performs a three-dimensional large eddy simulation (LES) on the flow around a static long-span rail-cum-road bridge girder with three separated boxes at different Reynolds numbers. The overall centre height H of the bridge model is chosen as the characteristic length, and the investigated Reynolds number regime falls into the regime of 1e2≤Re≤2.8e4. Through the analysis of the flow characteristics of three distinct regions in the flow field(the windward leading edge region, the gap region and the wake region), a successive transition of the wake flow, gap flow, and leading edge shear flow is observed with increasing Reynolds number. The surrounding flow patterns are divided by different Reynolds number regimes as: laminar separation at the trailing edge (Re<5e2); simultaneous instability of the gap shear layer and the wake (5e2≤Re<1e3); restabilisation of the upstream gap shear layer (1e3≤Re<3e3); secondary instability of the upstream gap shear layer and transition of the wake (3e3≤Re<8e3); transition of the separated shear layer at the leading edge (8e3≤Re≤2.8e4). This paper reveals in detail the complex vortex dynamics in the surrounding flow field of the special cross section with three separated boxes.

Study of surface roughness on flow past a wind turbine tower section

The flow around wind turbine towers usually reaches very high Reynolds numbers greater than a million. Understanding the flow around the towers under these conditions is crucial, as it may lead to vibrations due to the vortices formed. Investigating aerodynamic characteristics at such high Reynolds numbers, both numerically and experimentally, is challenging. The current study validates such an experimental study, where a rough surface is employed to increase the effective Reynolds numbers and accelerate the laminar-turbulent transition in the boundary layer. Unsteady Reynolds-Averaged Navier-Stokes (RANS) simulations are carried out using OpenFOAM for a Reynolds number range of 1.36·105 to 6.8·105. The constant (a 1) used to calculate the eddy viscosity is varied to simulate the flow separation during adverse pressure gradients. A force partitioning method is implemented in OpenFOAM and various force contributions are analysed for this Reynolds number range. It is seen that the RANS simulations overpredict the aerodynamic characteristics and the extent of flow separation unless the value of a 1 is varied as a function of the Reynolds number. Furthermore, it is observed that the only force contributor is the vorticity-induced force, as the simulations are performed for a fixed cylinder.

Effects of roughness on non-equilibrium turbulent boundary layers

The effects of roughness were considered as part of a NATO Advanced Vehicle Technology effort titled ‘Non-Equilibrium Turbulent Boundary Layers at High Reynolds Numbers’ (NATO AVT-349). This paper comments on the current state of understanding of the flow physics and modelling efforts to predict rough-wall boundary layer behaviour. Outer layer similarity to smooth wall flows and Reynolds number effects are discussed for zero, favourable, and adverse pressure gradients based on the results of experiments and numerical simulations. Various types of modelling are considered including Reynolds averaged Navier-Stokes (RANS) models with different roughness and turbulence models, wall-modelled large eddy simulations (WMLES), and resolvent models. Current needs and gaps in present understanding are discussed along with recommendations for future experiments and computations.

Enhancing heat transfer in various grooved annular for Taylor-Couette-Poiseuille flow

The present study investigated the impact of various parameters on pressure drop, Nusselt number, and friction factor in grooved annular channels, which have practical applications in cooling electric motors and generators. The parameters studied include the effective Reynolds number, Taylor number, groove aspect ratio, number of grooves, and groove angle. The k-ω SST turbulence model was employed in CFD simulations for various parameter ranges. These ranges include an effective Reynolds number spanning from 4.42 × 103to 1.6 × 104, Taylor number of 0–2.24 ×106, the groove aspect ratio of 0 to 2, the number of grooves ranging from 5 to 20, and the groove angle ranging from 70° to 130°. As the effective Reynolds and Taylor numbers increase within the ranges noted above, the Nusselt number exhibits a corresponding increase of 9.16 % and 1.77 %, respectively. However, the effective Reynolds number plays a more significant role. Various design factors, including the number of grooves, the aspect ratio, and the groove angle, also influenced the heat transfer enhancement. As any of these factors increase within the specified ranges, the corresponding Nusselt number values increase by 2.35 %, 3.62 %, and 6.09 %, respectively.

Boundary-layer instability on a highly swept fin on a cone at Mach 6

The growth and characteristics of linear, oblique instabilities on a highly swept fin on a straight cone in Mach 6 flow are examined. Large streamwise pressure gradients cause doubly inflected cross-flow profiles and reversed flow near the wall, which necessitates using the harmonic linearized Navier–Stokes equations. The cross-flow instability is responsible for the most-amplified disturbances, however, not all disturbances show typical cross-flow characteristics. Distinct differences in perturbation structure are shown between small ( $\sim$ 3–5 mm) and large ( $\sim$ 10 mm) wavelength disturbances at the unit Reynolds number $Re' = 11 \times 10^6$ m $^{-1}$ . As a result, amplification measurements based solely on wall quantities bias a most-amplified disturbance assessment towards larger wavelengths and lower frequencies than would otherwise be determined by an off-wall total-energy approach. A spatial-amplification energy-budget analysis demonstrates (i) that wall-normal Reynolds-flux terms dictate the local growth rate, despite other terms having a locally larger magnitude and (ii) that the Reynolds-stress terms are responsible for large-wavelength disturbances propagating closer to the wall compared with small-wavelength disturbances. Additionally, the effect of free-stream unit Reynolds number and small yaw angles on the perturbation amplification and energy budget is considered. At a higher Reynolds number ( $Re' = 22 \times 10^6$ m $^{-1}$ ), the most-amplified wavelength shrinks. Perturbations do not behave self-similarly in the thinner boundary layer, and the shift in most-amplified wavelength is due to decreased dissipation relative to the lower-Reynolds-number case. Small yaw angles produce a streamwise shift in the boundary layer and disturbance amplification. The yaw results quantify a potential uncertainty source in experiments and flight.

Investigation of Sidewall and Reynolds Number Effects in a Ribbed Square Duct

This paper presents a comprehensive three-dimensional Direct Numerical Simulation (DNS) investigation of flow characteristics over a roughened wall in a duct, exploring bulk Reynolds number variations from 4400 to 13,200 and considering the influence of side walls. Notably, a significant increase in friction factor highlights heightened resistance to flow due to surface roughness, emphasizing the importance of considering surface conditions in engineering applications. The study reveals three recirculation zones in the streamwise direction, indicating intricate separation phenomena caused by the interaction between the ribbed wall and the flow. Furthermore, the presence of sidewalls creates two major vortices perpendicular to the flow direction, highlighting the complexity of the vortical structures in this configuration, crucial for predicting flow behavior and optimizing system performance. The study demonstrates that the influence of the Reynolds number on these vortices is not well-scalable with respect to outer units, in contrast with respect to smooth ducts. Investigating side-wall effects, increased turbulent production rate, and non-equilibrium turbulence along the side walls highlight the sensitivity of turbulent stresses to Reynolds number and side-wall proximity. In conclusion, the paper provides novel insights into the interplay between Reynolds numbers, roughened surfaces, and boundary conditions in turbulent flows, laying a foundation for a deeper understanding of the flow in duct with high roughness.

Estimating nonlinear wind-induced response of roof cable nets by aeroelastic experiments and ML modeling

The paper examines the structural engineering challenges related to the assessment of the wind-induced vertical displacements of lightweight, hyperbolic-paraboloid cable-supported membrane roofs. Analysis and comparisons are conducted using three distinct methods for calculating the roof vertical, out-of-plane displacements. Finite element method (FEM) analysis is employed using: (i) estimated static nodal forces obtained from wind pressure coefficients determined by aerodynamic wind tunnel tests on a rigid building model, and (ii) loads found from wind pressure coefficients, estimated through machine learning (ML) methods, and (iii) measured roof response found from aeroelastic wind tunnel tests on a flexible model. The study examines three different roof geometries (square, rectangular and circular) and two distinct membrane curvatures for each geometry. Furthermore, wind directionality (three mean-wind incidence angles) and Reynolds number effects (seven mean wind velocities) are studied. Comparisons show that the non-linear FEM analysis, based on estimated static wind loads, underestimates the roof displacements at the roof center, compared to the direct measurements on the aeroelastic model. The main contribution of the study consists of a novel application of ML models, and Artificial Neural Networks (ANNs) in particular, which are employed to correct roof displacement estimations, found by simplified aerodynamic test pressure measurements on rigid roof models. The goal is to better describe the complex fluid-structure interaction of the roof membranes, which can only be achieved by direct aeroelastic tests that are difficult to design and execute. Finally, the study demonstrates that ANNs can be used not only for the preliminary design of the full-scale structure but also for construction of wind tunnel scale models.

A multi-region analysis of unsteady Oseen's equation for accelerating flow past a circular cylinder

It is difficult to find a valid high-order (of Reynolds number) analytical approximation to the uniform viscous flow past an infinite circular cylinder by applying perturbation techniques. In this study, we show that by accelerating flow past a circular cylinder with taking unsteady Stokes' solution as an initial approximation, higher-order approximation solutions to unsteady Oseen's equation can be obtained by an iteration scheme of perturbation, which exactly satisfy the boundary conditions. As a matter of fact, the nonlinear (convective) term linearized by Oseen's approximation is overweighted especially near the body surface. To eliminate the overweight, a multi-region analysis is proposed in this study to improve analytical unsteady Oseen's solution so as to extend the valid range of Reynolds numbers. In other words, the flow region is hypothetically divided into several annular regions, and the linearized convective term in each region is modified by multiplying with a Carrier's coefficient c (0 &amp;lt; c ≤ 1). The results show that, when the accelerating parameter in the range of 0.5 ≤ a ≤ 4, the maximum effective Reynolds number Reeff of the fourth-order five-region solution is both much larger than that of Stokes' and Oseen's ones. For example, when a = 0.5, Reeff = 22.26 is roughly eight times that of Stokes' solution (Reeff = 2.67), and nine times that of Oseen's solution (Reeff = 2.41). Moreover, when the instantaneous Reynolds number Re(t) is smaller than the Reeff, the flow separation angle and the wake length are both consistent with the numerical results obtained by accurately solving the full Navier-Stokes equations. In addition, the flow properties, including the drag coefficients, streamline patterns, and the pressure coefficients, as well as the vorticity distributions also agree well with the numerical results. This study represents a significant extension of our previous study for unsteady Stokes' equation [Xu et al., Phys. Fluids 35, 033608 (2023)] to unsteady Oseen's equation and its generalization.

Finite Reynolds Number Effect on Small-Scale Statistics in Decaying Grid Turbulence

Since about 1997, the realisation that the finite Reynolds number (FRN) effect needs to be carefully taken into account when assessing the behaviour of small-scale statistics came to the fore. The FRN effect can be analysed either in the real domain or in the spectral domain via the scale-by-scale energy budget equation or the transport equation for the energy spectrum. This analysis indicates that the inertial range (IR) is established only when the Taylor microscale Reynolds number Reλ is infinitely large, thus raising doubts about published power-law exponents at finite values of Reλ, for either the second-order velocity structure function (δu)2¯ or the energy spectrum. Here, we focus on the transport equation of (δu)2¯ in decaying grid turbulence, which represents a close approximation to homogeneous isotropic turbulence. The effect on the small-scales of the large-scale forcing term associated with the streamwise advection decreases as Reλ increases and finally disappears when Reλ is sufficiently large. An approach based on the dual scaling of (δu)2¯, i.e., a scaling based on the Kolmogorov scales (when the separation r is small) and another based on the integral scales (when r is large), yields (δu)2¯∼r2/3 when Reλ is infinitely large. This approach also yields (δu)n¯∼rn/3 when Reλ is infinitely large. These results seem to be supported by the trend, as Reλ increases, of available experimental data. Overall, the results for decaying grid turbulence strongly suggest that a tendency towards the predictions of K41 cannot be dismissed at least at Reynolds numbers which are currently beyond the reach of experiments and direct numerical simulations.

Improving the rheological behavior of magnetiz couple stress Buongiorno's nanofluid through resilient wavy channel with curvature effect: Nonlinear analysis

In biological systems, fluids with complex rheological behavior often encounter complex microenvironments. Couple stress fluids can be applied to model the flow of biological fluids in micro-vessels, capillaries, and other intricate structures. Couple stress fluids can be employed to model drug transport in microfluidic devices and capillaries, providing insights into the behavior of pharmaceuticals at small scales. Studying the couple stress fluids is crucial, particularly when considering the impact of particle viscosity in the existence of induced magnetic fields and nanoparticles that might enhance the characteristic motion. So, we studied the moderate and magnetic Reynold numbers and curvature effects of magnetized couple stress Buongiorno's nanofluid model through resilient wavy channel. The governing equations of this model are formed in non-dimensional form without any approximation, i.e., in the companionship of moderate Reynolds number and curvature effect, which aren't studied in this form. Using the Adomian decomposition approach, it is possible to obtain a solution of nonlinear system of partial differential equations analytically. The semi-analytical results are obtained and represented graphically for characteristic motion and bio-thermal properties for temperature and concentration, as well as magnetic features. Physically, by rising the magnetic Reynolds number, the magnetic permeability raises, so the ability of the couple stress fluid to form an internal magnetic field within itself with the impact of an applied magnetic field increases, which increases the magnetic force.

Viscous dissipation effects on the axisymmetric flow of Casson rheological fluid in the core region of curved artery surrounded by [formula omitted]/[formula omitted] nanofluid

Inspired by the blood flow in a curved artery, the heat transfer within the immiscible flow of Casson fluid (CF) as blood and plasma as nanofluid (NF) flow through a uniformly curved pipe is considered. The core region is filled with CF (non-Newtonian fluid), whereas the peripheral region is occupied with NF (Al2O3 water/γ-Al2O3 water). Viscous dissipation is also considered. The governing equations of the flow are solved analytically through perturbation series. The continuity of shear stresses and velocities at the interface with symmetric, regularity and no-slip conditions are considered. The effect of curvature ratio, blood thickness, Reynolds number, and concentration of nanomaterials in the peripheral region on heat transfer and axial velocity of both regions is investigated via contour and 2-dimensional plots. The streamlines are also presented for the variation of the above-mentioned parameters. The effect of nanomaterials concentration and curvature ratio are also studied on shear stresses. The results show that the axial velocity of immiscible fluids flow decreases with an increase in the concentration of nanomaterials. The number of velocity vortices decreases with an increase in the concentration of γ-Al2O3 nanomaterials in the peripheral region which leads to more controlled (laminar) flow. In real life, thinking about blood flow as a Casson fluid in the center and nanomaterials spread out around the edges can help researchers investigate flow patterns, shear stresses, and pressure distribution in curved arteries. It can help to analyze the development of diseases, i.e., aneurysms and atherosclerosis. Furthermore, the spread of nanomaterials in the surrounding area can be used as drug-delivery carriers in curved arteries.

Experimental investigation on heat transfer and friction factor characteristics for novel hybrid roughness used in solar air heater

ABSTRACT The influence of heat transfer and frictional characteristics of air that is turbulent and transitting rectangular channel textured by novel hybrid roughness (multi-V shaped ribs combined with hemispherical protrusion in V-fashion) has been studied experimentally. A uniform solar intensity of 1000 W/m2 is incident over the opposite side of the roughened plate. The relative roughness pitch, angle of attack, Reynolds number, hydraulic diameter, relative protrusion pitch, and relative gap width majorly influence the thermal and frictional characteristics of solar air heater. In this research paper, the effect of Reynolds number from 4281 to 18,250, relative protrusion pitch from 0.375 to 0.625 and relative gap width from 2 to 4 on heat transfer and friction factor on hybrid roughness geometry have been studied. The highest value of Nusselt number is 4.15 obtained at a relative protrusion pitch of 0.5, relative gap width of 2 compared to smooth duct and Reynolds number value of 18,250. By increasing the Reynolds number, the value of friction factor keeps on decreasing and highest value of friction factor of about 3.8 is obtained at a relative protrusion pitch of 0.375, Reynolds number value of 4,281 and relative gap width of 4 as compared to smooth duct. The results of the experiment shows that hybrid roughness performs thermally better than their solitary roughness geometries. Further, Nusselt number and friction factor correlations were also developed and show a very good match with the experimental results.

Effects of the Reynolds number on train aerodynamics considering air compressibility: a wind tunnel study

Abstract The study of Reynolds number (Re) effects is crucial for optimizing train aerodynamics, enhancing safety and reducing energy consumption of high-speed trains. In this paper, a wind tunnel test was carried out to investigate the influence of Re on the train aerodynamic performance considering the shift of the air compressibility, which has not yet been explored to date. The test was conducted in a low-speed and large-scale tunnel with a stationary floor and the vehicle model was based on a 1/8th scaled train with three units. The Re ranges from 0.75 × 106∼3.12 × 106 by accelerating the uniform wind speed from U = 27.8 m/s to U = 115 m/s with zero-yaw. The Mach number (Ma) of the maximum speed scenario has exceeded 0.3, indicating that the airflow can be considered as being in the compressible range. The results show that the aerodynamic characteristics of high-speed trains exhibit a self-similarity region of Re, which is dependent on the flow velocity. The aerodynamic loads change little when Re ≥ 1.51 × 106, which corresponds to U ≥ 55.6 m/s. Therefore, the compressibility of the airflow within the range up to U = 115 m/s has a negligible effect on aerodynamic loads, and can thus be disregarded. However, the surface pressure significantly decreases when the incoming flow surpasses 0.3 Ma and transitions into a compressible state. While the compressibility has a relatively minor impact on macroscopic aerodynamics, it cannot be overlooked when considering detailed flow field, such as surface pressure.

Turbulent Channel Flow: Direct Numerical Simulation-Data-Driven Modeling

Turbulent Channel Flow: Direct Numerical Simulation-Data-Driven Modeling

Staircase resiliency in a fluctuating cellular array.

Inhomogeneous mixing by stationary convective cells set in a fixed array is a particularly simple route to layering. Layered profile structures, or staircases, have been observed in many systems, including drift-wave turbulence in magnetic confinement devices. The simplest type of staircase occurs in passive-scalar advection, due to the existence and interplay of two disparate timescales, the cell turn-over (τ_{H}), and the cell diffusion (τ_{D}) time. In this simple system, we study the resiliency of the staircase structure in the presence of global transverse shear and weak vortex scattering. The fixed cellular array is then generalized to a fluctuating vortex array in a series of numerical experiments. The focus is on regimes of low-modest effective Reynolds numbers, as found in magnetic fusion devices. By systematically perturbing the elements of the vortex array, we learn that staircases form and are resilient (although steps become less regular, due to cell mergers) over a broad range of Reynolds numbers. The criteria for resiliency are (a) τ_{D}≫τ_{H} and (b) a sufficiently high profile curvature (κ≥1.5). We learn that scalar concentration travels along regions of shear, thus staircase barriers form first, and scalar concentration "homogenizes" in vortices later. The scattering of vortices induces a lower effective speed of scalar concentration front propagation. The paths are those of the least time. We observe that if background diffusion is kept fixed, the cell geometric properties can be used to derive an approximation for the effective diffusivity of the scalar. The effective diffusivity of the fluctuating vortex array does not deviate significantly from that of the fixed cellular array.

Study on Flow and Heat Transfer in Single Rock Fractures for Geothermal Heat Extraction

A full understanding of the fluid flow and heat transfer behaviors within a single fracture is important for geothermal heat extraction. In this study, models of single fractures with varying aperture and inner surface roughness (characterized by fractal dimension) are constructed, and a compound fracture aperture (CFA) is proposed to describe the coupled effect of fracture aperture and inner surface roughness. The effect of the fluid flow Reynolds number on heat transfer was investigated as it ranged from 4.84 to 145.63. The results show that the overall heat transfer coefficient (OHTC) in a single fracture significantly increases with the rise in fluid velocity and the compound fracture aperture. Particularly, the OHTC in a single fracture with an inner surface fractal dimension of 2.09 can be up to 1.215 times that of a parallel flat fracture when the flow velocity reaches 0.18 m/s. Moreover, for a fracture with a smaller CFA, enhancing the fracture aperture plays a decisive role in increasing the OHTC. Aperture emerges as a more sensitive optimization parameter for efficient heat extraction compared to the flow velocity. Meanwhile, based on simulation results, a convective heat transfer correlation equation is derived to provide more accurate estimates of the OHTC in rock fractures with different geometries and morphological features.

A Comprehensive Evaluation of Turbulence Models for Predicting Heat Transfer in Turbulent Channel Flow across Various Prandtl Number Regimes

Turbulent heat transfer in channel flows is an important area of research due to its simple geometry and diverse industrial applications. Reynolds-Averaged Navier–Stokes (RANS) models are the most-affordable simulation methodology and are often the only viable choice for investigating industrial flows. However, accurate modelling of wall-bounded flows is challenging in RANS, and the assessment of the performance of RANS models for heated turbulent channel flow has not been sufficiently investigated for a wide range of Reynolds and Prandtl numbers. In this study, five RANS models are assessed for their ability to predict heat transfer in channel flows across a wide range of Reynolds and Prandtl numbers (Pr) by comparing the RANS results with respect to the corresponding Direct Numerical Simulation data. The models include three Eddy Viscosity Models (EVMs): standard k−ϵ, low Reynolds number k−ϵLS, and k−ωSST, as well as two Reynolds Stress Models (RSMs): Launder–Reece–Rodi and Speziale–Sarkar–Gatski models. The study analyses the Reynolds number effects on turbulent heat transfer in a channel flow at a Pr of 0.71 for friction Reynolds number values of 180,395,640, and 1020. The results show that all models accurately predict velocity across all Reynolds numbers, but the accuracy of mean temperature prediction drops with increasing Reynolds number for all models, except for the k−ωSST model. The study also analyses the Pr effects on turbulent heat transfer in a channel flow with Pr values between 0.025 and 10.0. An error analysis is performed on the results obtained from different turbulence models, and it is shown that the k−ωSST model has the smallest error for the predictions of the mean temperature and Nusselt number for high-Prandtl-number flows, while the low Reynolds number k−ϵLS model shows the smallest errors for low-Prandtl-number flows at different Reynolds numbers. An analytical solution is utilised to identify Pr effects on forced convection in a channel flow into three different regimes: analytical region, transitional region, and turbulent diffusion-dominated region. These regimes are helpful to discuss the validity of the models in relation to the Pr. The findings of this paper provide insights into the performance of different RANS models for heat transfer predictions in a channel flow.