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In this study we consider the flow over airfoils with leading-edge roughness, designed to mimic the ice depositions that may occur on an aircraft in flight. The focus of this investigation is the effect of the angle of attack on the mean-flow three-dimensionality. In our previous work (Kumar et al., Journal of Turbulence, Vol. 22, No. 11, 2021, pp. 735–760), we found stationary spanwise inhomogeneities in the form of alternating regions of fast- and slow-moving fluid, which were termed “flow channels.” In the present study we investigate further this phenomenon. We observe the formation of hairpin vortices downstream of the roughness elements, which eventually merge; this causes the formation of wider channels that remain coherent and affect the trailingedge separation. With increasing angle of attack, the intensity of flow channeling can increase or decrease depending on the topology of the leading-edge roughness. Its effect on the trailing-edge separation remains, however, significant. The mean-separation line is highly distorted, and the separation length can vary by up to 30% of the chord length along the span. Vishal Kumar acknowledges the financial support by Mitacs, Bombardier Aerospace, and CARIC/CRIAQ. Ugo Piomelli acknowledges the support from the Natural Science and Engineering Research Council of Canada under the Discovery Grant program. This research was enabled in part by computational support provided by Compute Ontario (https://www.computeontario.ca) and Southern Ontario Smart Computing Innovation Platform (https://www.soscip.org).

A novel approach for the prediction of soot formation in combustion simulations within the framework of discrete sectional method (DSM) based univariate soot model and Flamelet Generated Manifold (FGM) chemistry, referred to as FGM-CDSM, is proposed in this study. The FGM-CDSM considers the clustering of soot sections derived from the original soot particle size distribution function (PSDF) to minimize the computational cost. Unlike conventional DSM, in FGM-CDSM, governing equations for soot mass fractions are solved for the clusters, by using a pre-computed lookup table with tabulated soot source terms from the flamelet manifold, while the original soot PSDF is re-constructed in a post-processing stage. The flamelets employed for the manifold are computed with detailed chemistry and the complete sectional soot model. A comparative assessment of FGM-CDSM is conducted in laminar diffusion flames for its accuracy and computational performance against the detailed kinetics-based classical sectional model. Numerical results reveal that the FGM-CDSM can favorably reproduce the global soot quantities and capture their dynamic response predicted by detailed kinetics with a good qualitative agreement. Furthermore, compared to detailed kinetics, FGM-CDSM is shown to substantially reduce the computational cost of the complete reacting flow simulation with soot particle transport. Primarily, the use of FGM reduces the overall calculation by about two orders of magnitude compared to detailed kinetics, which is advanced further with the clustering of sections at a low memory footprint. Therefore, the present work demonstrates the promising capabilities of FGM-CDSM in the context of computationally efficient soot calculations and provides an excellent framework for extending its application to the simulations of turbulent sooting flames. The research leading to these results has received funding from the European Union’s Horizon 2020 Programme under the ESTiMatE project, grant agreement no. 821418. The authors gratefully acknowledge the Red Española de Supercomputación (RES) for computational resources.

Friction drag constitutes approximately half of the total drag of subsonic civil transport aircraft at cruise conditions. Several means were examined to control the flow over an aircraft and achieve laminar flow. Here, a new concept for friction drag reduction in the form of an integration of the aerodynamics and propulsion of the aircraft is put forward. Engines buried in the wing and at the rear of the fuselage suck the boundary layer of the entire wing and fuselage surface, and then, they used it as intake air and exhaust through ducts. At the wings, the engines exhaust in the form of a jet flap at the trailing edge providing distributed propulsion. By this laminar flow, propulsive concept laminar flow is established over the entire aircraft, resulting in substantial drag reduction. The analysis showed that out of the four electrically powered aircraft versions considered only the combined lift distribution with tailless fuselage is about to be feasible. It was also found that the example aircraft design is inappropriate. It is expected that a design purposely based on the proposed concept would bring electrically powered transport aircraft within the specific energy levels of present batteries.

Microchannels are important devices to improve the heat exchange in several engineering applications as heat, ventilation and air conditioning, microelectronic cooling, power generation systems and others. The present work performs a numerical study of a microchannel with two trapezoidal blocks subjected to laminar flows, aiming to analyze the influence of the boiling process on the geometric configuration of the microchannel. Constructal Design and Exhaustive Search are used for the geometrical evaluation of the blocks. The Mixture multi-phase model and the Lee phase change model were both employed for the numerical simulation of the boiling process. In this study, the influence of the height and higher width of the first block (H11/L11) over the heat transfer rate and pressure drop for different magnitudes of the ratio between the lower width and higher width (L12/L11) was investigated. It is considered water in monophase cases and water/vapor mixture for multiphase flow. Two different Reynolds numbers (ReH = 0.1 and 10.0) were investigated. Results indicated that, for the present thermal conditions, the consideration of boiling flows were not significant for prediction of optimal configurations. Results also showed that in the cases where the boiling process was enabled, the multi-objective performance was higher than in the cases without boiling, especially for ReH = 0.1.

We intend to investigate numerically non-isothermal fluid flowing through a rectangular channel containing a perforated plate called screen with fixed refraction as well as the resistance coefficient. Air is permitted to flow with an initial temperature of 20 °C and with an initial rate of 1 (m/sec) from the entrance of the channel. A heater with a temperature of 50 °C and flux condition of 10 (W/m2) is applied at the lower boundary of the channel. The two-dimensional incompressible and the steady-state Navier Stokes equation along with the heat equation are worked out with the Galerkin’s Least Square method using COMSOL Multi-Physics. The difference in temperature and the velocity magnitude from the entrance to the exit of the channel is contrasted in terms of angles π/18to π/4. The heat transfer coefficient, the temperature, and the local Nusselt number are calculated downstream of the plate. Moreover, we have focused the behavior or orientation of velocity field, pressure, temperature, and friction factor through the screen with the help of five straight paths arranged with equal distance. Satisfactory results are achieved when compared with the available literature. The parameters of the heat transfer are affected by the angle of the perforated plate and the Nusselt number is increasing linearly with the angles and showing the exceptional pattern for all the angles. Finally, we suggested the angle of attack to achieve the optimum results for velocity field, temperature at the downstream, friction factor and the pressure.

With the increase of high-power electrical components in modern ships, especially fully electric ships with electric propulsion drive (EPD), the cooling of EPD electrical components has become particularly important. Providing optimal configurations for heat sinks with high thermal efficiency plays an essential role in this regard. A new technique for improving the efficiency of heat sinks is the utilization of perforated fins. This study examined the effects of perforation geometry (shape and size) on laminar airflow flow and heat transfer characteristics over a perforated plate-fin heat sink. Three-dimensional simulations were conducted using the finite-volume scheme based on the SIMPLE algorithm. In this research, the effects of perforation shape and size on various parameters, e.g., total drag force, average Nusselt number, perforated fin efficiency (PFE), heat transfer performance enhancement (HTPE), and fin optimization factor (η) were evaluated. The results confirmed that at a specific heat transfer surface area for perforated fins, the highest efficiency is achieved by circular perforations. In contrast, the square perforations due to geometric similarity to rectangular fins could reach the maximum size. Consequently, fins with square perforations could achieve the most optimal configuration. Also, results showed that for a constant perforations size, change in perforations shape improves HTPE, PFE, and η by more than 40%, 45%, and 110%, respectively. Also, by modifying perforations size for a specified shape, an increment of more than 35%, 40%, and 150% is observed in HTPE, PFE, and η, respectively.

"How long is the coast of Britain?" was the question stated by Mandelbrot. Using smaller and smaller rulers the coast length limits to infinity. If this logic is applied to the fractal heat sink geometry, infinite cooling capacity should be obtained using fractals with mathematically infinite surface area. The aim of this article is to check this idea using Richardson extrapolation of numerical simulation results varying the fractal element length from one to zero. As expected, the extrapolated heat flux has a noninfinite limit. The presented fractal heat sink geometry is non-competitive to the straight fins.

Gel fibers prepared based on microfluidic laminar flow technology have important research value in constructing biomimetic scaffolds and tissue engineering. The key point of microfluidic laminar flow technology is to find the appropriate fluid flow rate in the micropipe. In order to explore the influence of flow rate on the laminar flow phenomenon of a microfluidic chip, a microfluidic chip composed of an intermediate main pipe and three surrounding outer pipes are designed, and the chip is prepared by photolithography and the composite molding method. Then, a syringe pump is used to inject different fluids into the microtubing, and the data of fluid motion are obtained through fluid dynamics simulation and finite element analysis. Finally, a series of optimal adjustments are made for different fluid composition and flow rate combinations to achieve the fluid’s stable laminar flow state. It was determined that when the concentration of sodium alginate in the outer phase was 1 wt% and the concentration of CaCl2 in the inner phase was 0.1 wt%, the gel fiber prepared was in good shape, the flow rate was the most stable, and laminar flow was the most obvious when the flow rate of both was 1 mL/h. This study represents a preliminary achievement in exploring the laminar flow rate and fabricating gel fibers, thus offering significant reference value for investigating microfluidic laminar flow technology.

Within the framework of the Stokes model of an incompressible fluid with a constant viscosity, the problem of uniform acceleration of a plane from rest with its subsequent stationary motion is formulated and analytically solved. The analysis of the obtained solution indicates its agreement, within the limiting transition, with the Stokes self-similar solution, which corresponds to the instantaneous bringing of the plane to motion with a finite velocity. Both solutions, as well as the balance of viscous dissipation with the power of the friction force of the plane on the fluid, indicate that the solution of the problem will never take the form of a linear function. However, given the absence of a longitudinal pressure gradient, it is the linear solution that must be obtained from the corresponding Stokes equation of steady motion. This contradiction for the description of the boundary layer is overcome by assuming a spatial variability of the molecular diffusion coefficient, which is a consequence of the violation of isotropy and homogeneity of the medium., В рамках моделі Стокса нестисливої рідини, що має сталу в’язкість, сформульовано та аналітично розв’язано задачу про рівномірний розгін площини із стану спокою із подальшим стаціонарним її рухом. Аналіз отриманого розв’язку вказує на його узгодження, в рамках граничного переходу, із автомодельним розв’язком Стокса, що відповідає миттєвому приведенню площини до руху із скінченою швидкістю. Обидва розв’язки, а також баланс в’язкої дисипації із потужністю сили тертя площини об рідину, вказують на те, що розв’язок задачі ніколи не буде мати вигляд лінійної функції. Проте, зважаючи на відсутність повздовжнього градієнту тиску, саме лінійний розв’язок повинен отримуватись із відповідного рівняння Стокса стаціонарного руху. Вказане протиріччя для опису граничного шару долається шляхом припущення там змінності у просторі коефіцієнта молекулярної дифузії, що є наслідком порушення ізотропії та однорідності середовища.&nbsp

In the present study, to predict the transverse velocity field in the near-wake of laminar flow over a circular cylinder at the Reynolds numbers of 60 and 300, we construct neural networks with instantaneous wall pressures on the cylinder surface as the input variables. For the two-dimensional unsteady flow at Re=60, a fully connected neural network (FCNN) is considered. On the other hand, for a three-dimensional unsteady flow at Re=300 having spanwise variations, we employ two different convolutional neural networks based on an encoder–FCNN (CNN-F) or an encoder–decoder (CNN-D) structure. Numerical simulations are carried out for both Reynolds numbers to obtain instantaneous flow fields, from which the input and output datasets are generated for training these neural networks. At the Reynolds numbers considered, the neural networks constructed accurately predict the transverse velocity fields in the near-wake over the cylinder using the information of instantaneous wall pressures as the input variables. In addition, at Re=300, it is observed that CNN-D shows a better prediction ability than CNN-F.

Inspired by the shape of water flow in nature, a novel algorithm for global optimization, water flow optimizer (WFO), is proposed. The optimizer simulates the hydraulic phenomena of water particles flowing from highland to lowland through two operators: 1) laminar and 2) turbulent. The mathematical model of the proposed optimizer is first built, and then its implementation is described in detail. Its convergence is strictly proved based on the limit theory. The parametric effect is investigated. The performance of the proposed optimizer is compared with that of the related metaheuristics on an open test suite. The experimental results indicate that the proposed optimizer achieves competitive performance. The proposed optimizer was also successfully applied to solve the spacecraft trajectory optimization problem.

The present study numerically, investigates the aerodynamic characteristics of low speed flow past symmetric NACA airfoils, for various t/c values of 0.10, 0.15, 0.18, 0.21 and 0.24 at chordwise Reynolds numbers of 2 × 105 and 4 × 105, where t is the airfoil thickness and c is the airfoil chord. The presence of laminar separation bubble is indicated by oscillatory behaviour of pressure coefficient on the suction surface beyond peak pressure. The fluctuations in lift/drag are seen at smaller t/c values of 0.10 and 0.15, whereas no fluctuations are seen at a higher t/c value of 0.21. An empirical expression is developed to predict the mean lift, viscous as well as total drag coefficients for symmetric airfoils as a function of t/c only, which varies linearly for both the Reynolds numbers studied. The velocity vectors show the flow separations phenomenon only at smaller t/c values of 0.10 and 0.15, while at a higher t/c value of 0.21, well behaved and steady flow field is seen, which might be the reason for the absence of lift/drag fluctuations. The far-field acoustic measurements of symmetric NACA airfoils for various thickness ratios reveal that thicker airfoil (NACA0021, t/c = 0.21) radiates lower acoustic emissions (i.e., about 2 dB) as compared to the thinner (NACA0010, t/c = 0.10) ones.

In the current study, we focused on the shape effects of copper (Cu) nano-particles on heat transmission of three-dimensional magnetohydrodynamic (MHD) nano-fluid. A particular type of flow is considered, i.e., rotating flow over an exponentially stretching sheet. Significant actions of thermal radiation and Grashof number are also formulated to study. The modified Chebyshev wavelets method is introduced to examine the numerical solutions of the accomplished model. Error analysis and further comparison with existing results reflect the appropriateness of the proposed modification. Graphical behavior of dimensionless velocities, temperature, Nusselt number, and skin friction under the inspiration of several parameters is also presented. The attained solutions propose that the modification is beneficial and can be protracted to other highly nonlinear problems. The modified Chebyshev wavelets technique lowers computing time, according to the study. The research takes into account the form impacts of nano-particles. There are three kinds of nano-particles to examine (spherical, laminar, and cylinder). The behavior of various particles varies depending on the flow and temperature profile. For microparticles with a laminar structure, velocity and temperature have higher values.

Concentration gradient and fluid shear stress (FSS) for cell microenvironment were investigated through microfluidic technology. The Darcy–Weisbach equation combined with computational fluid dynamics modeling was exploited to design the microfluidic chip, and the FSS distribution on the cell model with varying micro-channels (triangular, conical, and elliptical). The diffusion with the incompressible laminar flow model by solving the time-dependent diffusion–convection equation was applied to simulate the gradient profiles of concentration in the micro-channels. For the study of single cell in-depth, the FSS was investigated by the usage of polystyrene particles and the concentration diffusion distribution was studied by the usage of different colors of dyes. A successful agreement between model simulations and experimental data was obtained. Finally, based on the established method, the communication between individual cells was envisaged and modeled. The developed method provides valuable insights and allows to continuously improve the design of microfluidic devices for the study of single cell, the occurrence and development of tumors, and therapeutic applications.

The fluid flow in a two-dimensional channel with a sudden expansion (x/h = 2) is studied. The calculations were performed for the laminar flow regime based on the numerical integration of the nonstationary Navier-Stokes equations. Various flow characteristics are determined at Re = 100–800. Results are obtained for longitudinal velocity profiles for various sections of the channel. The present work is devoted to modeling the separation flow around a plate in a cylinder. Mathematical modeling of the fluid flow and the results of a computational study of the put forward hypothesis are carried out using the example of the fluid flow supply to the cylinders. The unsteady Reynolds-averaged Navier-Stokes equations are used as a mathematical model of flows. For the numerical solution of the presented systems of equations, the control volume method and the SIMPLE algorithm were used., {"references":["Blasius H. Laminare Stromung in Kanalen Wecselnder Briete , Zeitschrift filer Mathematik und Physik. 10 . p. 225. (1910)","The starting flow down a step , J. Fluid Mech, 69( 2).pp. 229-240. (1975)","Sinha SP, Gupta AK, Oberai M. M . Laminar tear-off flow around ledges and caverns , Rocket technology and cosmonautics, 19 (12), pp. 33-37.(1981)","4.\tArmaly B. F., Durst F., Pereira J. C. F., Schonung B.\t Experimental and theoretical investigation of backward-facing stap flow , J. Fluid Mech, 127. pp. 473-496.(1983","5.\tZheng P. Detached currents. - M.: Mir. 2.P,354. (1973)","Honji H. The starting flow down a step. J. Fluid Mech., 1975, vol. 69, no. 2, pp. 229– 240. DOI: https://doi.org/10.1017/S0022112075001413","7.\tСинха С.П., Гупта А.К., Оберай М.М. Ламинарное отрывное обтекание уступов и каверн. Ч. 1. Течение за уступом. Ракетная техника и космонавтика, 1981, т. 19, № 12, с. 33–37.","8.\tЧжен П. Отрывные течения, М., Мир, 1972.","Гогиш Л.В., Степанов Г.Ю. Турбулентные отрывные течения. М., Наука, 1979.","10.\tLe H., Moin P., Kim J. Direct numerical simulation of turbulent flow over a backward-facing step. J. Fluid Mech., 1997, vol. 330, pp. 349–374. DOI: https://doi.org/10.1017/S0022112096003941","11.\tDurst F., Melling A., Whitelow J.H. Low Reynolds number flow over a plane symmetric sudden expansion. J. Fluid Mech., 1974, vol. 64, iss. 1, pp. 111–118. DOI: https://doi.org/10.1017/S0022112074002035","Cherdron W., Durst F., Whitelow J.H. Asymmetric flows and instabilities in symmetric ducts with sudden expansions. J. Fluid Mech., 1978, vol. 84, iss. 1, pp. 13– 31. DOI: https://doi.org/10.1017/S0022112078000026","Macadno E.O., Hung Т.-K. Computational and experimental study of a captive annular eddy. J. Fluid Mech., 1967, vol. 28, iss. 1, pp. 43–64. DOI: https://doi.org/10.1017/S0022112067001892","14.\tKumar A., Yajnik K.S. Internal separated flows at large Reynolds number. J. Fluid Mech., 1980, vol. 97, iss. 1, pp. 27–51. DOI: https://doi.org/10.1017/S0022112080002418","Плоткин А. Расчеты спектральным методом некоторых отрывных ламинарных течений в каналах. Аэрокосмическая техника, 1983, № 7, c. 75–85.","16.\tAcrivos A., Schrader М.L. Steady flow in a sudden expansion at high Reynolds numbers. Phys. Fluids, 1982, vol. 25, iss. 6, pp. 923–930. DOI: https://doi.org/10.1063/1.863844","Куон О., Плетчер Р., Льюис Дж. Расчет течений с внезапным расширением при помощи уравнений пограничного слоя. Теор. основы инж. расч., 1984, т. 106, № 3, с. 116–123.","Плетчер Л. Пределы применимости уравнений пограничного слоя для расчета ламинарных течений с симметричным внезапным расширением. Теор. основы инж. расч., 1986, № 2, с. 284–294.","19.\tLoitsyansky L.G. Mechanics of liquid and gas. - M.: Nauka, 1987. - 678 p.","20.\tPatankar SV Numerical Heat Transfer and Fluid Flow. Taylor and Francis. ISBN 978-0-89116-522-4, 1980.","21.\tSamarsky A.A. Theory of difference schemes.-M.: Nauka, 1983.-656p.","22.\tAnderson D., Tannehill J., Pletcher R. Computational fluid mechanics and heat transfer : In 2 vols. T. 1: Per. from English. - M.: Mir, 1990. - 384 p.","23.\tMadaliev E, Madaliev M, Adilov K, and Pulatov T. Comparison of turbulence models for two-phase flow in a centrifugal separator in E3S Web of Conferences. 264 . 1009. (2021). https://doi.org/10.1051/e3sconf/20212640 1009"]}

The current paper aims at assessing the effect of the radial mesh on the description of the axial velocity in steady-state and transient conditions and at presenting the results of a new optimized equal-area mesh. For this purpose, a quasi-2D model is implemented and tested for different mesh configurations and sizes. A new two-region mesh geometry with 40 cylinders is proposed to optimize the description of the wall shear stress immediately after each pressure variation. This mesh is composed of two regions: one with a high-resolution near the pipe wall and the second with a coarser grid in the pipe core. Different configurations of this mesh are analysed for both steady and unsteady conditions. Results are compared with those obtained by a 1D model and with experimental data for laminar flows, discussed in terms of the computation effort and accuracy. The proposed two-region mesh has demonstrated: (i) a reduction in the simulation error by five times when compared with standard meshes for the same computational effort and for the instantaneous valve closure; (ii) an important improvement in accuracy for an experimental S-shape valve maneuver, particularly for meshes with few cylinders; and (iii) a correct description of the transient pressures collected in the experimental tests.

In high-power laser systems, the primary cause of contamination of optical components and degradation of spatial cleanliness is laser-induced sputtering of particles. To mitigate this problem, laminar flow is frequently utilized to control the direction and transport of these particles. This study characterizes the properties of laser-induced sputtering particles, including their flying trend, diameter range, and velocity distribution at varying time intervals. A time-resolved imaging method was employed to damage the rear surface of fused silica using a 355 nm Nd: YAG pump laser. The efficacy of laminar flow in controlling these particles was then assessed, with a particular focus on the influence of laminar flow direction, laminar flow velocity, particle flight height, and particle diameter. Our results indicate that the optimal laminar flow velocity for preventing particle invasion is highly dependent on the maximum particle attenuation distance (or safety distance), which can vary by up to two orders of magnitude. Furthermore, a laminar flow velocity of 0.5 m/s can effectively prevent particle sedimentation. Future research will aim to optimize laminar flow systems based on these findings to achieve high surface cleanliness in high-power laser systems with minimal energy consumption.

Despite the extensive research already done on laminar flows with porous boundaries, polar flows bounded by cylinders have not yet been studied. This paper investigates the polar laminar flow for an incompressible fluid located in a porous annular pipe and driven by suction-injection at the walls. The fluid being confined between the cylinders with zero axial velocity, it is proven that the flow takes place in the polar plane with conservation of mass if an incoming flow exists in the same plane to compensate the mass of fluid extorted by suction. So, one of the cylinders undergoes the suction, and the other the injection. Suitable boundary conditions for both cylinders are then found. The problem depends on the Reynolds number, the pipe gap ratio, and the pore density and surface ratios. The method of solution utilizes the shooting technique including the Runge-Kutta and Newton-Raphson algorithms. Radial flows are found as a possible solution. When the flow is not radial, the patterns of the acceptable streamlines highlight a particular zone in which the fluid is at rest, bounded by two singular streamlines and the downstream cylinder. The flow velocity is determined. Physical understandings of the flow are derived.

The transition process within a Laminar Separation Bubble (LSB) that formed on a compressor blade surface was investigated using Large Eddy Simulations (LESs) at a Reynolds number of 1.5 × 105 and incidence angles of 0°, +3°, and +5°. The vortex dynamics in the separated shear layers were compared at various incidence angles and its effects on the loss generation were clarified through entropy analysis. Results showed that transition onset, which was accurately identified by the Linear Stability Theory (LST), was significantly promoted at the increased incidence angle. As such, the development of LSB was suppressed and the relative role of viscous instability played in the transition process was weakened. At the incidence angle of 0°, two-dimensional spanwise vortices detached from the blade surface and rolled up periodically, which were further stretched and eventually evolved into large-scale hairpin vortices. As time passed, the fully developed hairpin vortices broke down into small-scale eddies. Meanwhile, the flow near the wall reversely ejected into the outer separated shear layers and a sweeping process happened subsequently, forcing the separated shear layers to reattach and accelerating the generation of turbulent fluctuations. By comparison, the strength of vortex rolling-up was weakened at higher incidence angles, and the vortex pairing and breakdown of large-scale vortices were less pronounced. Therefore, the level of turbulent fluctuations that generated in the separated shear layers was reduced. Detailed entropy analysis showed that the turbulent dissipation effect related to the Reynolds shear stresses determined the largest amount of positive entropy generation, which declined to a lower level as the incidence angle increased from 0° to +5°. Correspondingly, the profile loss was reduced by 50.4%.

We present the laminar boundary layer flow over the standard tori rotating in an otherwise quiescent incompressible fluid. The mean flow equations are derived by using a specific form of the toroidal-poloidal coordinate system. A pseudo-spectral collocation method mixed with the first-order Euler scheme is employed to solve the related steady mean flow equations. A fixed aspect ratio R is defined as the ratio of radii of the torus and its tube that distinguishes each fixed torus within the general family of standard tori. Tori of spindle type turn into a sphere when the aspect ratio R = 0 and thus the mean flow results for the rotating sphere are consistently reproduced. The influence of aspect ratio R on the steady mean velocity components and the wall shear stresses are presented in detail. In a precise manner, the mean flow results for each rotating torus are explainable in a consistent way to the already established case of steady laminar boundary layer flow over the rotating sphere. The significance of the current work is discussed in terms of the hydrodynamic instabilities of boundary layer flows over the family of rotating tori.

A cooperative molecular communication (CMC) system is considered inside a cylindrical-shaped channel where a few cooperative nodes (CNs) are intermediately placed between a transmitter (TX) and a fusion center (FC). The expressions for the maximum achievable rate and probability of error at the FC considering AND and OR rules are derived. Furthermore, the performance of the CMC system in a cylindrical channel is compared with the direct and CN-assisted systems. The CMC system with randomly-placed CNs is also analyzed and compared with the uniformly-placed CNs, and it is found that a lower probability of error is obtained in the case of uniform placement\ud of CNs. Furthermore, the system performance as a function of radial displacement of TX and FC under constant flow is compared with that under laminar flow and a higher probability of error is observed under laminar flow. The increased probability of error under laminar flow occurs due to the fact that the drift velocity decreases towards the walls of the cylindrical channel. The analytical expressions are verified using Monte-Carlo simulations.

The flow driven by electromagnetic forcing of an electrolytic fluid in a concentric sphere system with differential rotation is studied experimentally and theoretically in the laminar regime. The electromagnetic force is generated by the interaction of a direct current injected radially through electrodes located at the equatorial zone of the spheres and a dipolar magnetic field produced by a permanent magnet inside the inner sphere. Even though the flows are fully three-dimensional, under some assumptions, they can be mathematically modeled with a general one-dimensional solution from the incompressible Navier–Stokes equations. Additionally, in order to deepen the flow dynamics, a full three-dimensional numerical simulation is also obtained. Experimentally, velocity profiles in the equatorial plane between spheres were obtained with particle image velocimetry. The analytical solution reproduces qualitatively the experimental profiles, whereas the numerical solution reproduces quantitatively the experimental measurements.

This paper presents a numerical investigation of the laminar flow and pressure drop characteristics of planar Tee joints, a canonical flow of interest for the thermal-hydraulic design of oil-immersed power transformer windings. After formulating the problem in nondimensional form, the steady, constant property flow in planar 90 ∘ Tee joints is computed numerically by integrating the Navier–Stokes equations with fully developed upstream and downstream boundary conditions. The analysis assumes a straight-through configuration in which the straight duct holds flow in the same direction before and after the junction, whereas the flow in the side branch can either divide from the incoming flow or combine with it. The analysis starts with the description of the flow patterns that emerge in the dividing and combining cases for all mass split ratios, 0 ≤ m 1 ≤ 1 , and a wide range of straight duct to side branch width ratios, 1 ≤ α ≤ 3 , and Reynolds numbers of the common branch, 0 < Re3 ≤ 200, values that are representative of the cooling oil flow in oil-immersed transformer winding. Flow maps for planar Tee joints are then presented, showing the existence of different regions in the (Re3, m 1 )-plane that exhibit different number and location of recirculation zones. Pressure distributions and secondary loss coefficients are then computed and analyzed, providing a numerical database that is used to develop new local pressure loss correlations for planar Tee joints in an accompanying paper.

High-temperature high-velocity steam exposures of (0001) sapphire coupons were performed at temperatures of 1200 °C–1450 °C to determine the quantitative capability of the steamjet apparatus. Recession results were compared to calculated values of Al(OH)3 (g) mass transfer rates based on laminar flow models and available thermodynamic data for Al(OH)3 (g). Linear material volatilization rates and a strong gas velocity dependence on the reaction depth confirmed that the Al2O3 reaction was controlled by a gas-phase diffusion process. The temperature dependence for the steam reaction agreed with thermodynamic calculations and with the literature, confirming that Al(OH)3 (g) transport through a gas boundary layer represents the rate-limiting step for Al2O3 volatilization in steam. The steamjet experimental setup can thus be utilized for determination of steam-oxide reaction thermodynamics given known steam flow conditions. Steamjet test recession results for simple oxides are discussed for comparison with behavior of complex oxides that form porous product layers, which are not yet well understood.

Transversal and longitudinal combustion instabilities typically present in gas turbines and rocket engines. It is thus important to investigate the flame responses of the two directional disturbanc...

The application of grooved surface structure is an emerging and effective means in turbulence flow control. However, for a realistic configuration, the global flow field described directly by simple application of massive grids makes it unfeasible to simulate. In this paper, a boundary surrogate model reproducing the effect of microscopic near-wall region is proposed to improve computational efficiency. The surrogate model trained with Lattice Boltzmann Method (LBM) considering the rarefied effect based on real micro/nanoflow field is new among literature, which accurately shows flow characteristics of the micro/nano structure. With this approach, numerical simulations via Reynolds-averaged Navier Stokes equations with modified wall boundary condition are performed in subsonic and transonic flow. The results show that micro/nano grooved surface structure has the effect of delaying transition from laminar to turbulence, thus reducing the skin friction significantly. Analysis of turbulence intensity and turbulence kinetic energy shows that the near-wall flow field of grooved airfoil is more stable compared with that of the smooth airfoil. The reducing rate of maximum turbulent intensity reaches 13.39%. The paper shows a perspective for further application of micro/nano groove structure to turbulence flow control in aircraft design by providing an accurate and efficient simulation method.

In current numerical study, forced flow and heat transfer of water/NDG (Nitrogen-doped graphene) nanofluid in nanoparticles mass fractions (φ) of 0, 2 and 4% at Reynolds numbers (Re) of 10, 50, 100 and 150 are simulated in steady states. Studied geometry is a two-dimensional microchannel under the influence of nanofluid jet injection. Temperature of inlet fluid equals with Tc=293K and hot source of microchannel is under the influence of oscillating heat flux. Also, in this research, the effect of the variations of attack angle of triangular rib (15°, 30°, 45° and 60°) on laminar nanofluid flow behavior inside the studied rectangular geometry with the ratio of L/H=28 and nanofluid jet injection is investigated. Obtained results indicate that the increase of Reynolds number, nanoparticles mass fraction and attack angle of rib leads to the increase of pressure drop. By increasing fluid viscosity, momentum depreciation of fluid in collusion with microchannel surfaces enhances. Also, the increase of attack angle of rib at higher Reynolds numbers has a great effect on this coefficient. At low Reynolds numbers, due to slow motion of fluid, variations of attack angle of rib, especially in angles of 30°, 45° and 60° are almost similar. By increasing fluid velocity, the effect of the variations of attack angle on pressure drop becomes significant and pressure drop figures act differently. In general, by using heat transfer enhancement methods in studied geometry, heat transfer increases almost 25%.

The inclusion of transition to turbulence effects in computational fluid dynamics simulations makes it possible to design laminar flow airframes. It also increases the level of physical representat...

The laminar boundary-layer separation phenomenon is an interesting and important aspect of boundary-layer flows. It occurs in various physical situations because of a decrease in wall shear stress caused by retarded flow velocity, among other things. Flow separation can be prevented or delayed by utilizing bodies of revolution because the surface transverse curvature produces a favorable pressure gradient, which in turn increases the wall shear stress that keeps the flow attached to the surface. Bodies of revolution, whose body contours follow a power-law form, also play a vital role in delaying flow separation. Bodies of revolution of varying cross sections and involving surface transverse curvature are utilized to examine their effects on flow separation. In particular, a convex transverse curvature has been considered owing to its effects on the nature of the favorable pressure gradient, which delays the flow separation. A Görtler-type retarded flow velocity was considered in this study to investigate the flow separation process. A detailed analysis is provided to understand the flow separation by calculating the separation points under various assumptions. It has been observed that the body contour exponent n and the convex transverse curvature parameter k play an assistive role in the delay of boundary-layer separation even under the influence of strong retardation. The results are presented through various tables and graphs to highlight the role of the power-law exponent of external velocity m, convex transverse curvature parameter k, and body contour exponent n on the separation points.

Active and passive techniques have been utilized together to enhance heat transfer in this study. The ferronanofluid, magnetic field, and dimpled tube have not been utilized together in the literature so far. Regarding this issue, this investigation is the first experimental study to specify the effect of use of these three effects simultaneously. The concept of this study is to determine the thermo-hydraulic performance of Fe3O4/H2O flow inside a dimpled tube under magnetic field effect. Constant and uniform heat flux of 4500 W/m2 has been applied on the surface of the tube. The work aims to gain data in the range of laminar flow (1131≤ Re≤2102) in the dimpled tube. Dimple geometry with pitch ratio of P/d = 3.75, magnetic field (B = 0.03 ≤ T ≤ 0.16), and nanoparticle volume fraction of 1.0% are the base variables. The results showed that Nusselt number increases with increasing Reynolds number and magnetic field intensity. The highest increase in Nusselt number is obtained as 115.31% compared with the distilled water flow in the smooth tube for the case of magnetic field intensity of 0.3 T. The highest Performance Evaluation Criteria value is also determined as 1.44 for the case of ferronanofluid flow in dimpled tube at Re = 1131 in absence of magnetic field. WOS:000743375000001

The heat transfer is a very interesting field for efficient, useful, eco-friendly reasons. The economic & environmental factors demand that we get the maximum possible efficiencies from thermal power plants possible only by making more efficient heat exchangers. Increasing the effectiveness of new and existing heat exchangers is a typical criterion of engineers involved with the design of heat exchangers. Augmenting process plant efficiency and finding new ways to reduce energy requirements is always an important design priority. Therefore, the heat transfer augmentation plays a substantial role in improving energy efficiency and development of high-performance thermal systems. The heat transfer augmentation techniques are classified as passive, active and compound techniques. The current article presents an extensive review of experimental and numerical studies on passive compound heat transfer augmentation techniques (PCHTAT), combining two or more of the current techniques can be employed all together to produce an enhancement larger than that produced by using only one augmentation. The compound technique arrangement are (i.e. helical-ribbed tube with double twisted tape inserts, Dimpled tube fitted with a twisted tape swirl generator, non-uniform wire coil, and twisted tape inserts. etc.) which covers the laminar and turbulent flow regions. Interactions between different enhancement methods will increase the overall heat transfer coefficient of the thermal systems than that produced by using only one augmentation technique.

Batch-type solar collector is a tilt-able water-heating solar-thermal system comprising an isosceles-trapezoidal enclosure housing a circular-cylinder absorber at the bottom wall, insulated side-walls, and flat-top glazing. Free convection of air inside such trapezoidal enclosure is studied numerically by varying the tilt angle of the whole enclosure from 0o-70o. The influence of tilt on the flow field has been demonstrated by plotting the streamlines and isotherms. The present study successfully identifies the importance of enclosure-tilt in quantifying heat-loss between absorber and glazing by developing a computational correlation between Nusselt and Rayleigh as a function of tilt. The correlation trend is non-monotonic over the range of angular Rayleigh numbers numerically experimented with having a peak around angular Rayleigh number 3×105 corresponding to the tilt-angle 30 degrees. The irregular-shaped cavity implies that the heat-transfer correlations already existing for regular-shaped cavities may not be used otherwise they will draw implausible conclusions and this argument identifies the novelty of the present study.

Solar air heaters (SAHs) convert incident solar radiation to thermal energy on an absorber plate. Smooth absorber plates have a low convective heat transfer rate in traditional ducts. Artificial rib roughness is applied to the bottom sides of the absorber plate in order to improve heat transfer in SAHs. However, when the rib roughness is employed over the absorber plate of the airflow side, it also increases the pressure loss due to friction. The purpose of this work is to provide researchers with a scientific perspective on the geometry, structure of ribs, flow directions, and laminar zone in order to maximize heat transfer and reduce friction. This review article discusses different roughness parameters, various artificial roughness geometries, and thermohydraulic performance. Nusselt number and friction factor correlations have also been incorporated in this review article which is developed by various scientists based on their respective experimental results for various roughness parameters. The paper also provides a thorough analysis of current research, summarises prior developments, and speculates on potential future routes for developing new heat transfer systems. Furthermore, this review paper will assist researchers and academics in developing a sound understanding of the effects of roughness on the absorber plate.

Computational Fluid Dynamics (CFD) and heat transfer simulations are conducted for a cross flow heat exchanger. The heat exchanger consists of a linear pipe carrying a heated fluid. The thermal interactions between the heated fluid having a laminar flow and the walls of the pipe have been studied under the influence of an external environment of water having a turbulent flow, in a direction normal to the pipe. A RANS model with a k- e variant was used to model the behavior of different material pipes which were observed under the varying conditions of turbulence, velocity, pressure and vorticity. When subjected to the same conditions, plots of the temperature gradient, isothermal contours, heat transfer coefficient against Reynolds number and thermal conductivity modelled against the various graphene coating thicknesses studied have shown that out of Copper and Stainless Steel the former has shown the most significant increase in thermal conductivity on the addition of a Graphene coating. Furthermore, to check for optimum efficiency, the same study was conducted with an internal coating of a Graphene layer for the aforementioned materials. It has been observed that an outer coating was not only more economically feasible, but also showed better thermal performance compared to an inner coating of graphene for copper, however it did improve the thermal performance of Stainless Steel significantly.

Low-loss dielectric laminates that are routinely used in the manufacturing of printed circuit boards (PCBs) are known to be anisotropic. The in-plane and the out-of-plane components of the dielectric permittivity have been so far typically determined using one of several available methods. In this article, we performed measurements of both components of complex permittivity of selected isotropic and anisotropic laminar materials employing a combination of a few split-post dielectric resonators (SPDRs) and one cylindrical cavity supporting several TM0n0 modes in the microwave band. Based on obtained data a novel, more precise approach to measuring the out-of-plane component of complex permittivity of laminar samples has been proposed. Additionally, a detailed analysis of several sources of measurement uncertainty (e.g., due to finite tolerances of manufacturing of the sample) has been performed and some recommendations formulated.

This paper demonstrates a numerical study on heat transfer characteristics of laminar flow in a double-layered oblique finned heat sink using nanofluids with Al2O3 nanoparticles. Microchannel heat sink with primary channel width of 0.5 mm with aspect ratio of 3 is employed. Instead of having conventional straight fins, oblique fins with narrow secondary channels are used. In this numerical study, single-phase fluid model with conjugate heat transfer is considered. The numerical modelling was first validated with existing data for double-layered conventional microchannel heat sink having water (base fluid) as the working fluid. Numerical investigations on oblique finned microchannel heat sink were then conducted for flow rates ranging from 3×10-7 to 15×10-7 m3/s, equivalent to primary channel inlet velocity in between 0.2 and 1.0 m/s. It was found that double-layered oblique finned configuration yields better heat transfer performance, inferred by the lower overall thermal resistance obtained as compared with that of double-layered conventional heat sink. Employing double-layered oblique finned heat sink, the heat transfer performance could be further enhanced, by using nanoparticles that are added into water-based fluid. It is found that the reduction of overall thermal resistance is proportional to the volume fraction of nanoparticles. Using cross flow double-layered oblique finned configuration, the largest reduction in the overall thermal resistance can reach up to 25%, by using nanofluids with 4% volume fraction of Al2O3 nanoparticles.

Laminar cross-flow over a circular cylinder with smooth as well as longitudinally grooved surfaces was investigated numerically for low freestream Reynolds number ranging from 50 to 300. Most of the currently published works on similar flow configurations considered high Reynolds number in the turbulent regime. The computations were performed by the ANSYS Fluent code. The numerical results were validated against the experimental results. The triangular V-shaped, the U-shaped, and Rectangular shaped grooves, with unit aspect ratio; along with the smooth cylinder, are considered. The predicted flow-field for the grooved cylinder cases are analyzed and compared with that for the smooth cylinder. The aerodynamic loads, time-averaged velocities, rms velocity, vorticity, and pressure coefficient plots around the smooth and grooved cylinders were compared to explore the effect of the shape of the grooves on flow dynamics over the cylinder. The flow physics around the cylinder is significantly affected by the shape and size of the grooves, and their circumferential distribution. It is found that the U-grooves significantly decrease the mean drag coefficient (around 13% for Re = 200 and 10% for Re = 300 compared to the smooth cylinder case). The grooves decreased viscous drag significantly (up to 30%) compared to pressure drag. The grooves on the cylinder also delayed the separation and reduced the extent of the recirculation zone in the cylinder wake due to the presence of recirculating flow within the individual grooves. The conclusion is that the properly designed longitudinal grooves on the cylinder in a cross-flow can be used advantageously for reducing aerodynamic loads like drag and lift force in laminar flow as well.

Natural and mixed convection heat transfer from a horizontal cylinder placed in a vented square enclosure has been investigated using numerical method with ANSYS Fluent 16.1 software for laminar and turbulent flow. Navier-Stokes equations and energy equation with standard k-? transport equation turbulence model have been used to simulate both flow and thermal behaviors. The operating conditions covered a range of the Rayleigh number from 103 to 106 and the Richardson number range between 0.1 and 100 at variable sizes of the lower open vent with constant upper opening size. The Nusselt numbers, velocity lines and isotherms are presented to display the flow and thermal behaviors. The results displayed that the average Nusselt number is affected by Rayleigh number, Richardson number, enclosure width, and lower opening size. The Nusselt number is enhanced by controlling the lower opening size. The maximum enhancement range for Nusselt number is between 20-85% depending on the Rayleigh number, Richardson number, enclosure width to cylinder diameter, and lower opening size. The velocity lines and isotherms are directly affected by the Rayleigh number, Richardson number, enclosure width to cylinder diameter, and lower opening size.

This study focuses on the combined effect of particle shape and porosity on the momentum and heat transfer of granular matter under laminar flow. Particle-resolved direct numerical simulations (PR-DNS) are carried out at different working conditions. Numerical results show that both the particle shape (via the aspect ratio, Ar, of the spheroid) and porosity play important roles in affecting the drag coefficient (Cd) and average Nusselt number (Nu). The influence of particle shape on Cd and Nu is regardless of the particle porosity. It is found that the Cd decreases with the increase of Ar for a given Reynolds number (Re). The Nu decreases with the increase of Ar under high Reynolds number (100

Numerical modeling of turbulent fluid flow generally valid only for fully developed turbulent flow without consideration of laminar flow region. Generally in any flow past body consist of laminar flow region eventually it turn to turbulent over a finite length. The prediction of laminar to turbulent transition boundary flow is influence the boundary separation in the turbulent zone and its effects in delay of separation. In this paper transition flow is predicted by fully turbulent flow solved by turbulent Kinetic energy and Specific turbulent dissipation models, transition is modeled by coupling of turbulent scalars and kinetic energy of laminar fluctuations. Transition model is analyzed over flow past aerofoil.

As one of the major functions of drilling mud is to maintain pressure inside a wellbore to avoid any invasion of unwanted high-pressure, this makes the determination of this pressure loss a very complicated task in the petroleum drilling industry. The aim of this paper is to predict the behaviour of drilling fluid flowing inside rotating pipe then in a concentric annulus at various values of inlet velocity and rotation speed. The governing equations (continuity and momentum) are solved numerically using CFD simulation with FLUENT commercial code. The flow is laminar in three-dimensional steady-state with non-Newtonian fluid. The results are visualized as: contours, pressure drop and velocity. The results show that pressure drop is decreased when pipe rotational speed increase. At the conditions of rotation speed of 300 rpm and inlet velocity of 1.2 m/s, the pressure loss present a significant decrease compared to the other conditions, furthermore, an uniform distribution of velocity in the pipe and annulus, is indicated. Therefore we can considerate this conditions of rotation speed and inlet velocity as optimal conditions.

A numerical simulation study of laminar hypersonic cold airflow over the backward-facing step (BFS) is performed at a freestream Knudsen number of 0.00009589 for resolving the flow field. The effects on the wall properties caused by the expansion of the flow and the separation of the boundary layer at the step corner have been investigated. The contributions of pressure and viscosity to the coefficients of lift and drag have been elucidated. It is seen that an increase in step height “nh” from n = 1 to 5 for a freestream flow at Mach 7.6 produces an incremental effect on the CL/CD ratio, whose range is between −1 to 1 for the variations in the step height simulated. The current study concludes that BFS yet remains a geometry that contributes to more drag than lift, however that effect can be minimized by increasing the step height during the design process of hypersonic vehicles for the above-mentioned Mach number.

This paper focuses on the convective heat transfer characteristics of Fe3O4 /Water magnetic nanofluids under laminar and turbulent conditions. After verifying the accuracy of the experimental apparatus, the effects of magnetic field strength, concentration, Reynolds number and temperature on the convective heat transfer coefficient have been studied. The convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions were studied in depth, and the influence of each factor on the heat transfer coefficient was analyzed by orthogonal experimental design method. Under the laminar flow conditions, the convective heat transfer of magnetic nanofluids performed best when the Reynolds number was 2000, the magnetic field strength was 600, the temperature was 30℃ and the concentration was 2%. And the convective heat transfer coefficient (h) increased by 3.96% than the distilled water in the same conditions. In turbulent state, the convective heat transfer of magnetic nanofluids performed the best when the Re was 6000, the magnetic field strength was 600, the temperature was 40℃ and the concentration was 2%. The h increased by 11.31% than the distilled water in the same Reynolds number and the magnetic field strength conditions.

Laminar mixing in the stirred tank is widely encountered in chemical and biological industries. Isolated mixing regions (IMRs) usually exist when the fluid medium has high viscosity, which are not conducive to mixing. In this work, the researches on IMRs, enhancement of laminar mixing and the phenomenon of particle clustering within IMRs are reviewed. For most studies, the aim is to destroy IMRs and improve the chaotic mixing. To this end, the mechanism of chaotic mixing and the structure of IMRs were well investigated. The methods developed to destroy IMRs include off-centered agitation, dynamic mixing protocol, special designs of impellers, baffles, etc. In addition, the methods to characterize the shape and size of IMRs as well as mixing effect by experiments and simulations are summarized. However, IMRs are not always nuisance, and it may be necessary in some situations. Finally, the present engineering applications are summarized, and the prospect of the future application is predicted. For example, particle clustering will form in the co-existing system of chaotic mixing and IMRs, which can be used for solid-liquid separation and recovery of particles from high viscosity fluid.

In the present numerical study, the finite element method is adopted to investigate the thermo-hydraulic transport characteristics of two-dimensional, steady, Laminar flow of Newtonian fluid through partially porous wavy channel. The wavy channel consists a porous wavy slab at the center. Water is taken as working fluid with Prandtl number Pr = 6.93 and Reynolds number Re = 700 considered for all simulations. Results are investigated in the form of average Nusselt number (Nuavg), Enhancement ratio (ER), Pressure drop ( Δ p ), Pressure ratio (PR), and Performance factor (PF) for different wave amplitudes ( α =0.06, 0.12, and 0.18) and wave phase shifts (φ = 00, 45°, 90° and 180°) of porous slab at different Darcy numbers range (Da = 10-6 to 10-2). Results reveal a significant increment in average Nusselt number with decreasing in Darcy number on the pressure drop penalty. The maximum value of ER found for geometry configuration α = 0.18 and φ = 900 at Darcy number Da = 10-6, and on the other end, maximum PF is obtained at Darcy number Da = 10-2 irrespective of geometry configurations. The lower value of ER was obtained at φ = 1800 irrespective of wave amplitude and Darcy number. There is a significantly less effect of porous slab wave phase shift of φ = 450 and φ = 900 for given Da on PR at fixed wave amplitude.

The flow nozzle aerator, which is the part of the water tap made up of Acrylonitrile Butadiene Styrene (ABS), can be modified entirely with a new design. The curved and cone-shaped slopes are used to improve the smooth flow at uniform velocity. Simultaneously, discharge is optimum by modified interior design. The smooth laminar delivery of water with optimum pressure, the liquid element at the aerator end becomes smooth. The assembled nozzle aerator solid model has been generated before experimentation. This can promote through the prediction by the modern tool ANSIFLUENT and Computational Fluid Dynamics (CFD) for finding the flow behavior and its outlet characters. The solid model can be fabricated to prototype for accurate dimensions by using 3D printing technology. Comparing fluid motion with the time consumption of filling water has been done over these different kinds of aerator and nozzle models, which are fabricated by 3-dimensional printing.

The use of micro-electronic devices in many applications such as aerospace, telecommunications, micro-electronics, robotics is drastically increasing and they need efficient cooling system. Micro-channel heat sinks (MCHS) are getting significant importance due to their very high surface to volume ratio and high heat dissipation rate. The hybrid nanofluids playing a vital role as cooling fluids in various thermal transportation applications due to their extraordinary heat transport characteristics. A numerical study is taken up for laminar flow of hybrid nanofluid as a heat transport medium in a rectangular MCHS to realize thermal and hydrodynamic behaviour in forced convection. The influence of Reynolds number (Re) and volume concentration of nanoparticles in Cu-Al2O3/water hybrid nanofluid on MCHS performance is investigated in the present paper. The correlations presented in the literature are used to calculate the properties of hybrid nanofluids. For various mixture ratios of 25–75%, 50–50% and 75–25% hybrid nanofluids the heat transport rate and pressure drop are calculated at different Reynolds numbers and compared with mono nanofluids of Cu-water (H2O) and Al2O3-water. An enhancement in heat transfer rate is observed with raise in volume fraction and marginal increase in pressure drop is observed for hybrid nanofluids over mono nanofluids of Cu-water and Al2O3-water. The results indicate an increase of 13.2% and 23.07% in Nusselt number for Cu-Al2O3/water hybrid nanofluid compared with Cu/water and Al2O3/water mono nanofluids respectively at 2.5% volume fraction. It is found from the numerical results that the pumping power requirement is less for hybrid Cu-Al2O3/water nanofluid compared to Cu/water nanofluids and an increase of 430 Pa compared to pure water. The data existing for Al2O3-water nanofluid in the literature is used to validate the present model.