In this paper the LAMINAR FLOW in the rectangular channel bends is simulated using numerical techniques. The turning angle of the channel bend and the area ratio of the channel cross-section are two important parameters to be examined. For FLOW simulation, the body fitted 3-D continuity and momentum equations are used and a body fitted general purpose code is developed. The existing results of a tied-diriven cavity and the experimental results from a 90 degree square bend were used for code validation. After the code validation, the effect of the area change in the 90 degree bend is examined.The numerical results indicated that increasing the area causes changes in the FLOW pattern, in turn, which has a direct impact on pressure drop. Similar results were obtained for other bend angles including 30,60,120,150 and 180 degree bends. The results showed that increased bend turning angle increases the pressure drop which is in good agreement with existing experimental data.

The superhydrophobic surfaces have many applications, including skin friction reduction, antiicing, anti-fouling, and self-cleaning surfaces. Also, with the precise design of these surfaces, it is possible to increase the heat transfer coefficient in the condensation heat transfer. In recent years, a variety of methods have been proposed for the fabrication of the superhydrophobic surfaces, some of which are very complex and not applicable for industrial uses. In this paper, a nanocomposite superhydrophobic coating is produced in a simple and applicable way for large surfaces. Using this method, a superhydrophobic surface with surface structures in multi-scale and with a sliding angle of less than 5 degrees is obtained. After evaluating the specification of superhydrophobic surfaces, slip length measurement of the coating is performed using a fabricated measurement system. It should be noted that the slip length of the superhydrophobic surface is a characteristic feature of these surfaces and always its measurement is associated with challenges. In this research, the slip length of the created coating was measured by use of the proposed measurement system. The results show that the slip lengths of about 40-500 microns can be achieved by use of the proposed measurement system.

In this paper the results of numerical simulations for heat transfer of a nanofluid FLOW inside a counter FLOW heat exchanger is presented. Effects of addition of the Al2O3 nanoparticles on the entropy generation of the system are investigated. Single fluid model is used for simulation of the nanofluid FLOW. Analytical and experimental formulations are used for density, specific heat, viscosity and conductivity of nanofluid. Finite volume method (FVM) has been used for numrerical simulation and SIMPLE algorithm is applied for pressure velocity coupling. It is found that adding nano particles in annulus, causes a little incerement in entropy generation which can be overlooked. On the other hand, the increasing of volume fraction of nanoparticles leads to ascend heat transfer coefficient (U ) and total heat transfer (Q) significantly, and it results in decreased entropy number (Ns).

A numerical investigation is carried out for LAMINAR sinusoidal pulsating FLOW through a modeled arterial stenosis with a trapezoidal profile up to peak Reynolds number of 1000. Finite element based numerical technique is used to solve the fluid FLOW governing equations where the fluid is assumed to be viscous, incompressible and Newtonian. The effects of pulsation, stenosis severity, Reynolds number and Womersley number on the FLOW behavior are studied. The dynamic nature of pulsating FLOW disturbs the radial velocity distribution and thus generates recirculation zone in the poststenotic region. The peak wall shear stress develops for 65% stenosis (by area) is 3, 2.2, and 1.3 times higher than that for 30%, 45%, and 55% stenosis, respectively. Peak wall shear stress and wall vorticity appear to intense at the throat of the stenosis. It is also observed that the peak wall vorticity seems to increase with the increase of stenosis size and Reynolds number. However, the peak values of instantaneous wall vorticity are not greatly affected by the variation of Womersley number.

In this paper, the LAMINAR incompressible FLOW equations are solved by an upwind least-squares meshless method. Due to the difficulties in generating quality meshes, particularly in complex geometries, a meshless method is increasingly used as a new numerical tool. The meshless methods only use clouds of nodes to influence the domain of every node. Thus, they do not require the nodes to be connected to form a mesh and decrease the difficulty of meshing, particularly around complex geometries. In the literature, it has been shown that the generation of points in a domain by the advancing front technique is an order of magnitude faster than the unstructured mesh for a 3D configuration. The Navier–Stokes solver is based on the artificial compressibility approach and the numerical methodology is based on the higher-order characteristic-based (CB) discretization. The main objective of this research is to use the CB scheme in order to prevent instabilities. Using this inherent upwind technique for estimating convection variables at the mid-point, no artificial viscosity is required at high Reynolds number. The Taylor least-squares method was used for the calculation of spatial derivatives with normalized Gaussian weight functions. An explicit four stage Runge-Kutta scheme with modified coefficients was used for the discretized equations. To accelerate convergence, local time stepping was used in any explicit iteration for steady state test cases and the residual smoothing techniques were used to converge acceleration. The capabilities of the developed 2D incompressible Navier-Stokes code with the proposed meshless method were demonstrated by FLOW computations in a lid-driven cavity at four Reynolds numbers. The obtained results using the new proposed scheme indicated a good agreement with the standard benchmark solutions in the literature. It was found that using the third order accuracy for the proposed method could be more efficient than its second order accuracy discretization in terms of computational time.

This paper presents a numerical investigation for LAMINAR forced convection FLOW of a radiating gas in a rectangular duct with a solid element that makes a backward facing step. The fluid is treated as a gray, absorbing, emitting and scattering medium. The governing differential equations consisting the continuity, momentum and energy are solved numerically by the computational fluid dynamics techniques. Since the present problem is a conjugate one and both gas and solid elements are considered in the computational domain, simultaneously, the numerical solution of Laplace equation is obtained in the solid element for temperature calculation in this area. Discretized forms of these equations are obtained using the finite volume method and solved by the SIMPLE algorithm. The radiative transfer equation (RTE) is also solved numerically by the discrete ordinate method (DOM) for computation of the radiative term in the gas energy equation. The streamline and isotherm plots in the gas FLOW and the distributions of convective, radiative and total Nusselt numbers along the solid-gas interface are presented. Besides, the effects of radiation conduction parameter and also solid to gas conduction ratio as two important parameters on thermo hydrodynamic characteristics of such thermal system are explored. It is revealed that the radiative Nusselt number on the interface surface is much affected by RC parameter but the radiation conduction parameter has not considerable effect on the convective Nusselt number. Comparison between the present numerical results with those obtained by other investigators for the case of non-conjugate problems shows good consistency.

The use of the classical Boussinesq approximation is a straightforward strategy for taking into account the buoyancy effect in incompressible solvers. This strategy is highly effective if density variation is low. Whenever the density variation is high, this can cause considerable deviation from the correct prediction of fluid FLOW behavior and the accurate estimation of heat transfer rate. In this study, an incompressible algorithm is suitably extended to solve high-density-variation fields caused by strong natural-convection with mixing of oxygen and nitrogen in unsteady LAMINAR compressible FLOW in a cavity. The continuity, momentum, energy and species equations are discretized based on finite volume methods and then numerically solved with extended algorithm with SIMPEL method. This new algorithm is capable of solving both Boussinesq and non-Boussinesq regimes.The fluid is assumed to be calorically an ideal gas and its thermodynamic properties depend on temperature and pressure. The extended algorithm is then verified by solving the benchmark convecting cavity problem at Rayleigh 106 and a temperature range of e=0.01-0.6. The results show that the method can vigorously solve unsteady mixing FLOW fields with extreme density variation

An accurate and efficient computational procedure is developed to predict the LAMINAR hypersonic FLOW field for both the perfect gas and equilibrium air around the axisymmetric blunt body configurations. To produce this procedure, the boundary layer equations utilize the integral matrix solution algorithm for the blunt nose and after body region by using a space marching technique. The integral matrix procedure enables us to create accurate and smooth results using the minimum grid in the boundary layer and to minimize the computational costs. This algorithm is highly appropriate for the design of hypersonic reentry vehicles. The effects of real gas on the FLOWfield characteristics are also studied in boundary layer solutions. Comparisons of the results with experimental data demonstrate that accurate solutions are obtained.

This paper explores the use of shark-skin inspired two-dimensional forward facing steps to attain LAMINAR FLOW control, delay boundary layer transition and to reduce drag. Computation Fluid Dynamics (CFD) simulations are carried out on strategically placed forward facing steps within the LAMINAR boundary layer using the Transition SST model in FLUENT after comprehensive benchmarking and validation of the simulation setup. Results presented in this paper indicate that the boundary layer thickness to step height ratio ( /h), as well as the location of the step within the LAMINAR boundary layer (x/L), greatly influence transition onset. The presence of a strategically placed forward facing step within the LAMINAR boundary layer might damp disturbances within the LAMINAR boundary layer, reduce wall shear stress and energize the boundary layer leading to transition onset delay and drag reduction as compared to a conventional flat plate. Results presented in this paper indicate that a transition delay of 20% and a drag reduction of 6% is achievable, thereby demonstrating the veracity of biomimicry as a potential avenue to attain improved aerodynamic performance.

In this study a two dimensional, steady state and incompressible LAMINAR FLOW for staggered tube arrays in crossFLOW is investigated numerically. A finite-volume method is used to discretize and solve the governing Navier-Stokes and energy equations for the geometries expressed by a boundary-fitted coordinate system. Solutions for Reynolds numbers of 100, 300, and 500 are obtained for a tube bundle with 10 longitudinal rows. FLOW and heat transfer results are presented for a tube at pitch-to-diameter ratios of 1.33, 1.60, and 2.00 for ES, ET, and RS arrangements. Differences in streamlines and isotherm contours compared for three different arrangements. The predicted results for skin-friction coefficient and average Nusselt number showed a good agreement with available experimental measurements.