Numerical Investigation Of Laminar Flow Research Articles

Multi-Block DQM/RBF-DQ as a meshless model for numerical investigation of laminar flow and forced convection in a channel with two circular fins

This work presents a numerical algorithm based on the combination of the conventional differential quadrature, radial basis function-based differential quadrature and domain decomposition technique as a truly method. The computation domain is decomposed into several subdomains and compatibility of subdomains is satisfied by applying additional interface equations. After performing validation process for the proposed algorithm, it was used to investigate the laminar flow and heat transfer within a horizontal channel with two circular fins at its bottom wall. The results show the excellent performance of the proposed method in simulating flow and heat transfer. The studies also indicate that increasing the radius of the fins and distance between the two fins increase their convective heat transfer rate. However, the effect of the first parameter on the thermal performance is far greater.

Three-dimensional numerical investigation of laminar flow in blind-tee pipes

Blind-tee pipes are often employed in process piping systems used in offshore and subsea oil and gas industry. The objective of the present study is to investigate the effects of blind-tee length, end-structure shape and flow velocity on the mixing condition inside blind-tee pipes. Three-dimensional numerical simulations are performed for the laminar flows in the pipes with blind-tee length varying from 1D to 5D at Re= 500, 1000, 1500 and 2000. Spherical and flat end-structure shapes are also investigated for the blind-tee section. Firstly, flow simulations in a straight pipe are performed, and the numerical results are compared with the analytical solutions. Then, the computed velocity profiles are used as the inlet velocity for the simulations of blind-tee pipes. Flow characteristics both inside and downstream the blind-tee section are numerically studied by analyzing the streamlines, pressure contours and velocity profiles. The results reveal that a higher inlet velocity and a blind-tee length no more than 3D can achieve a better mixing condition for the fluid flow in blind-tee pipes; while stagnant flows are more prone to occur towards the end of the blind-tee section at low velocities with the length longer than 3D, leading to potential fluid deposition in blind-tee pipes.

Numerical investigation of laminar flow of biological nanofluid in a rifled tube using two-phase mixture model: first-law and second-law analyses and geometry optimization

The impetus of this numerical investigation is to explore the performance aspects of laminar forced convection flow of biologically synthesized water–silver nanofluid inside an internally spiral-ribbed heat exchanger tube from both the first and second laws of thermodynamics perspectives. The two-phase mixture model is used to perform the required simulations. The impacts of the volume concentration of nanoadditives (φ), Reynolds number (Re) as well as the width (W), height (H) and pitch (P) of the ribs on the hydrothermal aspects and irreversibility behavior of the nanofluid are assessed, and the results are compared with the findings of smooth tube. It was found that the use of nanofluid and the use of rifled tube instead of water and smooth tube, respectively, are suitable ways to improve system performance from both the first and second laws of thermodynamics perspectives. Moreover, it was reported that the best hydrothermal performance of the nanofluid through the rifled tube occurs at φ = 1%, Re = 2000, W = 3 mm, H = 1 mm, P = 4 mm, while the minimum total irreversibility in the flow of water–silver nanofluid inside a rifled tube occurs at φ = 1%, Re = 2000, W = 3 mm, H = 0.5 mm, P = 4 mm.

Numerical investigation of laminar flow and heat transfer in a channel using combined nanofluids and novel longitudinal vortex generators

Enhancement of heat transfer in plate-fin heat exchangers can be obtained using vortex generators (VG). The three-dimensional laminar flow of water/Al2O3 nanofluid with different nanoparticle volume fractions in a channel with longitudinal vortex generators is numerically simulated. Two novel forms of modified delta winglet VG pairs (MDWP1, MDWP2) are introduced by adding and subtracting a part of the quadrant profile to the delta winglet VG profile. Simulation is carried out for the classic delta winglet pair (DWP) and MDWPs. Performance of heat transfer and pressure drop is compared as well as the overall performance analysis of channel is conducted for all three forms of VGs and two flow arrangement types, common flow up (CFU) and common flow down (CFD). Analytical expressions from the literature are used to check the validity of the model. Governing equations of laminar fluid flow and heat transfer are solved based on the finite-element method. The range of Reynolds number is from 100 to 500. Results show that in the range of the present study, using nanofluid increases about 20% of the heat transfer coefficient and 18% of pressure drop compared to pure water. As results confirm in all of the cases, the heat transfer coefficient increases using VG. The MDWP2 leads to the highest pressure drop and heat transfer between the three VGs types. It can produce up to 9% higher heat transfer coefficient in Re = 100 and 20% of higher pressure drop for CFD flow arrangement. The overall performance of the CFD arrangement is higher than CFU for the studied cases relatively. And the values of performance in a channel with DWP are greater than MDWP1 and MDWP2, which is due to the lower pressure drop of DWP.

Numerical investigation of laminar flow and heat transfer in a liquid metal cooled mini-channel heat sink

With the recent trend of miniaturization and high-power output, effective heat dissipation has become the top priority in several industrial applications. This work contributes to the novel and efficient cooling technique that utilizes the liquid metal as working fluid. A numerical analysis of laminar flow and forced convective heat transfer of Galinstan through a mini-channel heat sink exposed to a constant heat flux has been presented. A detailed parametric analysis of the influence of heat sink's geometry, and the inlet velocity on the pressure drop, pumping power and the maximum heat flux has been carried out. Optimized heat sink's dimensions and inlet velocity are obtained. Furthermore, the numerical results are compared with the analytical correlations and discussion concerning the agreement and discrepancy is made. In addition, the flow and heat transfer performance of mini-channel heat sink cooling using liquid metal, nanofluid and water are compared, which intuitively shows the advantage of using liquid metal as coolant.

Numerical investigation of laminar flow and heat transfer of non-Newtonian nanofluid within a porous medium

In this study, comprehensive study of laminar flow and heat transfer of pseudo-plastic non-Newtonian nanofluid (Al2O3+CMC) within the porous circular concentric region is presented. The effect of volume fraction of nanoparticles, Reynolds number, Darcy number, thickness ratio is studied. Simulations for different Reynolds numbers and Darcy numbers in the range of 100≤Re≤300and 10−4≤Da≤10−2 are done. The results show that the effect of the porous layer on increasing the convective heat transfer coefficient is larger than the Reynolds number, since, at a given volume fraction, the porous medium plays a greater role in increasing the heat transfer compared to the increasing Reynolds number. Also, at a given volume fraction and for a fixed porosity, decreases in the permeability leads to increased Darcy velocity and, consequently, velocity profile. As the thickness of the porous layer increases at fixed values of permeability and porosity, the velocity of the nanofluid is also increased in a constant Reynolds number, by increasing the thickness of the porous media, heat transfer coefficient increases. In addition, at a specified thickness and constant Reynolds number, by increasing the Darcy number, the heat transfer coefficient and the Nusselt number increases. Moreover, as the thickness of the porous layer increases at fixed values of permeability and porosity, the velocity of the nanofluid is also increased; this consequently maximizes the pressure drop.

A numerical investigation of laminar flow over a backward facing inclined step

The aim of the present study is to analyze the two dimensional flow over a backward-facing-inclined step in laminar flow regime. The inspiration for the present work is derived from the fact that in automobile industry, analyzing the flow over an inclined step shall help in understanding the characteristics of the rear vehicle wake. A considerable percentage of the energy needed to propel the vehicle is dissipated by the vorticity generated in the rear of the vehicle, hence it is of utmost importance to understand the properties of the wake. In the present paper, the flow over a backward step is initially analyzed and the results are compared with the existing literature to validate the code developed. The inclined step simulations were carried out by varying different aspects of the geometry i.e. different tilts, several upstream lengths and a range of different Reynolds numbers. Critical Reynolds numbers for vortex shedding in the wake of different step inclinations have been analyzed for all cases studied. A discussion on the time-averaged drag and lift coefficients as a function of Reynolds number and for all cases undertaken, are among the results presented. Among the conclusions, it is particularly interesting to point out that the inclination angle of 15° was found to be the critical angle for vortex shedding, after which critical Reynolds number remains constant.

A numerical investigation of laminar flow of a water/alumina nanofluid

The present paper reports the results of a numerical investigation of a tubular developing laminar flow of a water/alumina nanofluid under constant heat flux conditions. The nanofluid is modelled as a water/alumina nanoparticles mixture. Brownian and thermophoretic diffusion effects have been considered through the energy and nanoparticle concentration field equations. Though these modes of diffusion have been suggested extensively in the literature, their effect on momentum and energy transport has not yet been numerically analyzed. In addition, the model includes temperature and concentration effects over the transport properties of the nanofluid. A new CFD solver has been developed for the solution of the present set of governing equations. Model solutions have been sought for conditions corresponding to two experimental investigations carried out elsewhere. Base fluid (water) solutions have been used to asses the accuracy of the numerical model, the results being reasonably comparable to the experimental ones and adequately correlated by the Churchill and Ozoe correlation. Nanofluid solutions have been obtained for nanoparticles volumetric concentrations of up to 6%. A concentration boundary layer has been observed to develop along the wall of the pipe, a region which is progressively depleted of nanoparticles by the action of thermophoretic diffusion. A slight heat transfer enhancement has been found especially at the higher nanoparticle concentrations, with the maximum enhancement being of the order of 5%. The dimensionless numerical results, based on cross section (local) properties, fall within 25% with respect to the experimental ones. The Churchill and Ozoe correlation seems to adequately correlate numerical results for the range of Graetz numbers of the present investigation and for the lower range of nanoparticles concentration. Heat flux effects seem to play a potential role in nanofluid heat transfer at the tube wall though their significance has not been consistently investigated under the present investigation.

Numerical modeling of fluid dynamics and heat transfer of glass flow in a short channel

A numerical investigation of laminar flow in a two-dimensional, Cartesian flow that exits from a short channel with a backward-facing step is carried out in this work for the Reynolds number range of 0.00054 < Re < 54. We studied the steady state fluid dynamics, phase change and heat transfer of the flow. We analyzed the flow behavior occurring for different outflow velocities and three different configuration of the step. The incompressible working fluid was glass. The temperature, streamline, phase change and pressure fields are obtained and analyzed as a function of position. In order to obtain a better understanding of the step angle influence on the fluid dynamics, we obtained the heat transfer flux rates and the axial velocity profiles.

Numerical investigation of laminar flow and heat transfer in a radial flow cooling system with the use of nanofluids

Nanofluids, because of their enhanced heat transfer capability as compared to normal water/glycol/oil based fluids, offer the engineer opportunities for development in areas where high heat transfer, low temperature tolerance and small component size are required. In this present paper, the hydrodynamic and thermal fields of a water–γAl2O3 nanofluid in a radial laminar flow cooling system are considered. Results indicate that considerable heat transfer enhancement is possible, even achieving a twofold increase in the case of a 10% nanoparticle volume fraction nanofluid. On the other hand, an increase in wall shear stress is also noticed with an increase in particle volume concentration.

Numerical investigation of laminar flow and heat transfer in a radial flow cooling system with the use of nanofluids

Nanofluids, because of their enhanced heat transfer capability as compared to normal water/glycol/oil based fluids, offer the engineer opportunities for development in areas where high heat transfer, low temperature tolerance and small component size are required. In this present paper, the hydrodynamic and thermal fields of a water–γAl 2O 3 nanofluid in a radial laminar flow cooling system are considered. Results indicate that considerable heat transfer enhancement is possible, even achieving a twofold increase in the case of a 10% nanoparticle volume fraction nanofluid. On the other hand, an increase in wall shear stress is also noticed with an increase in particle volume concentration.

Numerical Investigation of Laminar Flow and Heat Transfer in Multiple Pipe Bends

The heat transfer is enhanced in curved pipes by the secondary flow. Its stirring effect is expected to be more augmented in multiple pipe bends which form a coiled pipe with periodically canging the plane of curvature. Numerical investigations of flow and temperature field including the developing region in such a pipe are carried out in laminar flow regime using parabolized governing equations. The calculation method has been validated for coiled pipes. In multiple pipe bends, Coriolis force due to the change of curvature plane causes complicated secondary flow pattern, realizing more homogeneous mixing. In the case of high Prandtl number fluids, the heat transfer is more enhanced in multiple pipe bends compared with in ordinary coiled pipes. Meanwhile, this is not the case for low Prandtl number fluids. The mechanism which causes this opposite effect is also discussed.

Numerical investigation of vortical evolution in a backward-facing step expansion flow

A numerical investigation of laminar flow over a backward-facing step is presented for the Reynolds number in the range of 50⩽Re⩽2500. The objective of this numerical investigation is to add to the existing knowledge of the backward-facing step flow to deepen our understanding of the expansion flow structure. We proceed with the analysis by verifying the computer code through the Pearson vortex problem. We then perform a parametric study by varying the Reynolds number, with the aim of determining whether or not there exists a critical Reynolds number, above which reattachment length on the channel floor decreases. We also concentrate on subjects that have been little explored in the flow, examples of which are the onset of a single vortex in the primary eddy and how the recirculating bubble containing flow reversals is torn into smaller eddies. Eddy distortion, leading to mobile saddle points, and the merging of eddies are also discussed in this study.

Time evolution of laminar flow over a three-dimensional backward-facing step

A numerical investigation of laminar flow over a backward-facing step is presented within the transient context. The analysis is concerned with the step geometry and flow conditions reported by Armaly et al. Results show that there is generally good agreement between the three-dimensional results and the experimental data for Re<400, and excellent agreement with the two-dimensional results. Insight is also provided into the rich character of the end-wall-induced three-dimensional vortices in the channel downstream of the step. To this end, the topological theory is adopted to draw the particle oil streaklines on the roof, floor, step plane and the end-wall, from which lines of separation and reattachment are theoretically determined. Together with the Lagrangian particle track plot in the flow interior, light is shed on the formation of a secondary flow pattern, and thus the development of longitudinal vortices. The present transient analysis increases the understanding of the complex interaction of the end-wall-induced vortices and the mainstream flow. This helps to reveal the mechanism responsible for the increasing penetration of the three-dimensional flow structure into a region near the mid-plane of the channel, at which the flow is essentially two-dimensional. Copyright © 1999 John Wiley & Sons, Ltd.

Numerical simulations of laminar flow over a 3D backward-facing step

A numerical investigation of laminar flow over a three-dimensional backward-facing step is presented with comparisons with detailed experimental data, available in the literature, serving to validate the numerical results. The continuity constraint method, implemented via a finite element weak statement, was employed to solve the unsteady three-dimensional Navier–Stokes equations for incompressible laminar isothermal flow. Two-dimensional numerical simulations of this step geometry underestimate the experimentally determined extent of the primary separation region for Reynolds numbers Re greater than 400. It has been postulated that this disagreement between physical and computational experiments is due to the onset of three-dimensional flow near Re ≈ 400. This paper presents a full three-dimensional simulation of the step geometry for 100⩽ Re⩽ 800 and correctly predicts the primary reattachment lengths, thus confirming the influence of three-dimensionality. Previous numerical studies have discussed possible instability modes which could induce a sudden onset of three-dimensional flow at certain critical Reynolds numbers. The current study explores the influence of the sidewall on the development of three-dimensional flow for Re greater than 400. Of particular interest is the characterization of three-dimensional vortices in the primary separation region immediately downstream of the step. The complex interaction of a wall jet, located at the step plane near the sidewall, with the mainstream flow reveals a mechanism for the increasing penetration (with increasing Reynolds number) of three-dimensional flow structures into a region of essentially two-dimensional flow near the midplane of the channel. The character and extent of the sidewall-induced flow are investigated for 100⩽Re⩽ 800. © 1997 John Wiley & Sons, Ltd.

Numerical investigation of laminar flows through 90-degree diversions of rectangular cross-section

Numerical solutions of the incompressible Navier-Stokes equations are obtained for steady, laminar flows through 90-degree diversions of rectangular cross-section. Calculations are carried out for various Reynolds numbers, discharge ratios and duct aspect ratios. The computed solutions are compared with available experimental measurements and analysed to elucidate the complex three-dimensional separation and flow topology patterns. It is shown that, even for large aspect ratio ducts, the flow at the symmetry plane is significantly affected by the distant top and bottom solid boundaries. These boundaries induce a complex three-dimensional flow which includes: a depth-varying dividing stream-surface in the main channel; depth-varying recirculation zones in both main and branch channels within which low velocity flow spirals upward; and secondary circulation currents which sweep near-bottom boundary flow into the two recirculation zones. These same flow patterns have been observed experimentally in diversions of circular as well as rectangular cross-sections for both turbulent and laminar flow regimes, but their details were not accessible to previous calculations.

95/05453 Experimental and numerical investigation of laminar flow over a forward facing step inside a pipe

95/05453 Experimental and numerical investigation of laminar flow over a forward facing step inside a pipe