Showing 6 results for Numerical Solution
M. S. Saidi and M. Saghafian, ,
Volume 20, Issue 1 (7-2001)
Abstract
In this paper, the oscillating two-dimensional laminar flow about a cylinder and the oscillation of a cylinder in still water are studied. A finite volume method is applied to solve the Navier Stokes equations using SIMPLEC algorithm on a body fitted co-located O-type grid. In this study, the non-dimensional flow numbers, Keulegan-Carpenter and Stokes’ numbers are chosen over a range where different laminar flow regimes are normally three-dimensional. The results of this simulation and comparison with numerical and experimental works indicate the good capability of this two-dimensional model in showing the various regimes of flow patterns and vortex shedding. Considering the forces exerted on the cylinder, this study shows that in cases where the flow is of a
regular type, there is a good match between longitudinal force presented by this work and the one calculated through Morrison’s equation. But for irregular flows where the flow pattern changes in each cycle, there is less overlap and the accuracy of Morrison’s equation is reduced. Studying the time variation of the transversal force gives accurate information about the vortex shedding and its frequency in each cycle and mode changing. Since the flow mode changes continuously with time, the average of transversal and longitudinal forces on consecutive cycles is not a good representation of the force exerted on the cylinder. On the other hand, the model has satisfactorily reproduced the time variation of the tranversal and longitudinal forces of a pure mode, matching the experimental results.
Keywords: Oscillating flow, Laminar flow about a cylinder, Numerical solution
M. H. Rahimian and M. Farshchi,
Volume 21, Issue 1 (7-2002)
Abstract
The internal flow circulation dynamics of a liquid drop moving in a co- or counter-flowing gas stream has been numerically studied. The present work is concerned with the time accurate numerical solution of the two phase flow field at the low Mach number limit with an appropriate volume tracking method to capture motion and deformation of a liquid drop. It is shown that relative velocity between gas and liquid and the parameters controlling the deformation of the drop have the strongest influence on its internal circulation, too. The effects of the liquid Weber number, ranging from 8 to 32, and of gas stream Reynolds number, ranging from 1 to 20 are studied. It was revealed that the largest and the most lasting internal circulation are observed in drops with small deformation in high Reynolds number gas streams. In the case of counter-flowing gas stream, there is a strong internal circulation inside the liquid drop. The locations of the gas separation points on the drop are strongly influenced by the internal circulation of the drop, resulting in a complex wake dynamics.
Keywords: Numerical solution, Two phase flow, Moving droplet, Droplet internal circulation
A. Keshavarzi and M. J. Kazemzadeh Parsee,
Volume 24, Issue 1 (7-2005)
Abstract
Flow separation at water intake is the main cause of head loss and flow discharge reduction.
As a result, study of shape and size of separation is very essential when designing an optimum water intake. Water intake is normally built with a 90 degree angle to the main channel flow direction. However, the flow structure in this type of water intake consists of large separation size along with vortex generation. In this study, the effect of the ratio of discharge at water intake to the main channel discharge (Qr) on the location and size of separation is investigated numerically and experimentally. The velocity of the flow at each point is measured in two dimensions using electromagnetic velocity meter. The results from the experimental data indicate that the location and shape of separations are a function of flow discharge ratio (Qr). These results also indicate that at higher ratios of flow discharge, the separation occurs downstream the water intake, whereas at lower flow discharges, the flow separation occurs upstream the water intake. Additionally, the capabilites of numerical turbulence computation models including standard k-e and RNG k-e models are investigated in this study. The computed flow velocity from the turbulence models showed that the result of standard k-e model is approximately close to the experimental data when compared with RNG k-e model
M. Hosseinalipour, M. M. Doustdar and K. Mazaheri, ,
Volume 24, Issue 2 (1-2006)
Abstract
A numerical simulation has been carried out to study the detonability characteristics of two- phase unconfined clouds. The parameters equivalence ratio, turbulence, shape, volume and uniformity of the cloud and the delay time distribution are recognized and introduced as the most important factors determining the reactivity of the cloud and influencing the initiation of a successful detonation. With regard to the dynamic behavior of the cloud and the changes in the magnitude of these significant characteristic parameters, the best ranges of time and position for secondary detonator action are determined.
Comparisons are also performed with experimental results along with theoretical analyses to validate the numerical results obtained in this study.
H. Edalati , B. Soltani,
Volume 34, Issue 2 (1-2016)
Abstract
Utilizing one of the mesh free methods, the present paper concerns static analysis of thin plates with various geometric shapes based on the mindlin classical plate theories. In this numerical method, the domain of issue is solely expressed through a set of nods and no gridding or element is required. To express the domain of issues with various geometric shapes, first a set of nodes are defined in a standard rectangular domain , then via a three-order map with, these nodes are transferred to the main domain of the original issue; therefore plates of various geometric shapes can be analyzed. Among meshfree numerical methods, Element Free Galerkin method (EFG) is utilized here. The method is one of the weak form integral methods that uses MLS shape functions for approximation. Regarding the absence of Delta feature in MLS functions, boundary conditions cannot be imposed directly; hence the Lagrangian method is utilized to impose boundary conditions. At the end, our outputs are compared with those of analytic and finite element methods for plates, in order to validate the exactness of our solution method, and then after reliability is established, a few new examples will be solved.
E. Ebrahimnia-Bajestan, H. Niazmand,
Volume 36, Issue 1 (9-2017)
Abstract
In this paper, numerical simulation of flow and heat transfer of Al2O3/water nanofluid has been carried out through three different geometries involving a straight pipe, a 90o curved pipe and a 180o curved pipe under constant heat flux condition. Employing singe-phase model for the nanofluid, the Navier-Stokes and energy equations for an incompressible and laminar flow have been solved in a body fitted coordinate system using a homemade code based on control-volume approach, while all thermophysical properties of the nanofluid are dependent on considered temperature. The effects of different nanoparticle concentration and centrifugal forces on the temperature and pressure field have been examined in detail. The accordance of numerical results with experimental data expresses the accuracy of the employed numerical method for simulating flow and heat transfer in the curved pipes, as well as the accuracy of the single-phase model of the nanofluid. The Presented results indicated that both the nanoparticle and curvature effects improve the heat transfer characteristics dramatically, but at the expense of considerable increase in pressure drop. Furthermore, the results showed that in order to obtain the optimum operating conditions of nanofluids, different parameters such as heat transfer enhancement and pressure drop must be considered simultaneously. Finally, a method has been proposed to indicate the proper nanofluid and flow geometry for special practical applications.
