Lid Cavity Research Articles

Impact of nanoparticle shape on thermo-solutal buoyancy induced lid-driven-cavity with inclined magnetic-field

The aim of this paper is to numerically investigate the influence of nanoparticles shape on heat and mass transport phenomena in a moving lid cavity under the combined effect of thermo-solutal buoyancy force and magnetic force. The governing equations are transformed into velocity-vorticity form of equations and solved using Galerkin's weighted residual finite-element-technique. The analysis has been carried out with parameters like buoyancy ratio (−5 ≤ N ≤ 5), magnetic field inclination angle (0° ≤ ϕ ≤ 90°) with four shapes of Al2O3 nanoparticle like bricks, blades, platelets and cylinders. The results revealed that the shape factor on Nusselt number is significant depending upon the inclined magnetic field and buoyancy ratio whereas on mass transfer the shape effect is negligible. The diffusion mode of transport process is stronger than the convection mode at higher inclination angle of magnetic field. Based on a given value of N and ϕ, blade and cylinder shows the best performance in Nusselt and Sherwood number respectively except the platelet shape that shows maximum frictional loss in terms of wall shear stress.

Numerical simulation of lid driven flow in a curved corrugated porous cavity filled with CuO-water in the presence of heat generation/absorption

In this article, numerical simulation is performed for mixed convection lid-driven flow of CuO-water nanofluid enclosed in a curved corrugated. Cylindrical obstacles having three different constraints: (adiabatic, cold, and heated) at its surface are considered. Internal heat generation/absorption and uniform heat is provided at the vertical wall of the cavity. The bottom wall is insulated, and the curve surfaces are maintained with cold temperature. Mathematically equations are developed from physical problems and solved through Galerkin weighted residual method of FEM formulation. The effect of various Reynold number (Re), Darcy number (Da), solid volume fraction of nanoparticles (ϕ), heat generation/absorption coefficient (Q) and various cylindrical obstacle on velocity, Nusselt number, molecular movements and the flow structure has been studied. Nusselt number increases for high Darcy number due to the convection in lid cavity. For high Reynold number generally Nusselt numbers decrease or remain the same at the wall with an increase of nanoparticles in porous medium. There significant effect of heat sink coefficient on temperature profile and Nusselt number decreases with increasing of Q.

Cavity Tightness Preferences of Overwintering Halyomorpha halys (Hemiptera: Pentatomidae).

Brown marmorated stink bug (Halyomorpha halys) (Stål) is a household nuisance pest that seeks shelter in buildings during the winter months. It has been found in a variety of cavities and spaces between building elements, as well as in the objects stored within buildings. This experiment examined the cavity tightness preferences for these insects as they settled in winter refugia. Adult overwintering H. halys were placed in two types of simulated refugia made from rigid material. Each type had a cavity of constant width, while one had a flat lid and constant tightness, and the other had a sloped lid that became tighter as insects moved inside. Adults were allowed to enter and settle, then their locations were recorded. In sloped lid cavities, H. halys tended to settle where the cavity tightness was between 4.5 and 5.5 mm. In the flat lid cavity boxes, H. halys tended to move all the way back. In both configurations, H. halys had a significant tendency to orient their heads towards the cavity entrance. A field comparison of cavity tightness in refugia with less rigid cardboard substrates was also performed, with spacers consisting of one or two layers of 3-mm cardboard. This comparison found differences in cavity selection by sex, with males more likely to pick single-spaced layers, and females more likely to select double-spaced layers. Understanding these preferences could be useful for collection, pest management, trap design, and study of impacts on structures.

Heat and mass transfer enhancement in a double diffusive mixed convection lid cavity under pulsating flow

This work assess the effectiveness of the pulsating flow regime for the enhancement of heat and mass transfer in double diffusive problems by studying a two-dimensional, heated, lid cavity. The research characterizes the influence of pulsating parameters such as temporal frequency, wave number and amplitude in the process. Results show that the pulsating regime enhances heat/mass transfer within a square cavity up to a 14%/38% respectively with respect to the non-pulsating case, due to the promotion of additional shear stress fields. As Richardson number, Brownian diffusion or the solute/thermal buoyancy ratio increase or the cavity becomes narrower, heat/mass transfer increases.

Performance of an elasto-viscoplastic model in some benchmark problems

A recent elasto-viscoplastic thixotropic model proposed by (de Souza Mendes in J. Non-Newton. Fluid Mech. 164:66–75, 2009; de Souza Mendes in Soft Matter 7:2471–2483, 2011) is applied to five benchmark problems: the flow in a lid cavity, the flow through an expansion followed by a contraction, the flow over a flat plate, the channel entry flow, and the flow around a cylinder confined between parallel plates. One of the main advantages of this approach is its ability to recover a model for elasto-viscoplastic materials in a smooth fashion, i.e., in the limit where the characteristic thixotropic time tends to zero. These problems are numerically solved using the finite element method, with a four-field GLS-type formulation. While the simplified version is applied to the first three problems, the full model including thixotropy is applied to the channel entry flow and the flow around the cylinder. The elasto-viscoplastic problems analyzed show that, in general, elasticity tends to inhibit yielding and is more concentrated in unyielded regions. The thixotropic effects analyzed show that the delay in the microstructure response of the material significantly alters the problem when compared to the pure elasto-viscoplastic counterpart.

Application of network simulation method to viscous flows: The nanofluid heated lid cavity under pulsating flow

In this paper, the Network Simulation Method (NSM) is used to model an unsteady, viscous, flow problem: the heated lid-driven filled with nanofluid and in the presence of a pulsating flow. Through this method is analyzed the influence of the amplitude, wave number and oscillation frequency of sinusoidal velocity waves at the lid on the convection performance of the cavity. It is stated that this method is simple and efficient for solving unsteady, viscous, Navier–Stokes equations, through the design and resolution of an electrical circuit network whose equations are formally equivalent to the ones of the fluid flow problem. Results show that, for the case of Pr=3.93, Re=50, Ri=11.82, sinusoidal velocity waves at the lid increase the time-averaged Nusselt number in the cavity with respect to the non-pulsating case up to a 16%. This is due to enhancement of the transport phenomena induced by the pulsating flow.

Implementation of arbitrary inner product in the global Galerkin method for incompressible Navier–Stokes equations

The global Galerkin or weighted residuals method applied to the incompressible Navier–Stokes equations is considered. The basis functions are assumed to be divergence-free and satisfy all the boundary conditions. The method is formulated for an arbitrary inner product, so that the pressure cannot be eliminated by Galerkin projections on a divergence-free basis. A proposed straightforward procedure for the elimination of the pressure reduces the problem to an ODE system without algebraic constraints. To illustrate the applicability and the robustness of the numerical approach and to show that numerical solutions with unit and non-unit weight functions yield similar results the driving lid cavity and natural convection benchmark problems are solved using the unit and Chebyshev weight functions. Further implications of the proposed Galerkin formulation are discussed.

A natural extension of the conventional finite volume method into polygonal unstructured meshes for CFD application

A new general cell-centered solution procedure based upon the conventional control or finite volume (CV or FV) approach has been developed for numerical heat transfer and fluid flow which encompasses both structured and unstructured meshes for any kind of mixed polygon cell. Unlike conventional FV methods for structured and block structured meshes and both FV and FE methods for unstructured meshes, the irregular control volume (ICV) method does not require the shape of the element or cell to be predefined because it simply exploits the concept of fluxes across cell faces. That is, the ICV method enables meshes employing mixtures of triangular, quadrilateral, and any other higher order polygonal cells to be exploited using a single solution procedure. The ICV approach otherwise preserves all the desirable features of conventional FV procedures for a structured mesh; in the current implementation, collocation of variables at cell centers is used with a Rhie and Chow interpolation (to suppress pressure oscillation in the flow field) in the context of the SIMPLE pressure correction solution procedure. In fact all other FV structured mesh-based methods may be perceived as a subset of the ICV formulation. The new ICV formulation is benchmarked using two standard computational fluid dynamics (CFD) problems i.e., the moving lid cavity and the natural convection driven cavity. Both cases were solved with a variety of structured and unstructured meshes, the latter exploiting mixed polygonal cell meshes. The polygonal mesh experiments show a higher degree of accuracy for equivalent meshes (in nodal density terms) using triangular or quadrilateral cells; these results may be interpreted in a manner similar to the CUPID scheme used in structured meshes for reducing numerical diffusion for flows with changing direction.

Chaotic flow in rotating lid cavities

Numerical computations are performed to investigate the structure and evolution of flow in a two-dimensional axisymmetric rotating lid cavity. Frequency decompositions, phase diagrams, and flow visualization are used to monitor the changing kinematics of the flow as the speed of the rotating side wall is increased. For the flow regimes investigated, the approach to steady state is characterized by oscillatory instabilities, quasiperiodic flow, and chaotic flow leading to turbulence. A detailed study of the physical mechanisms involved in the computed flow field indicates the existence of at least two independent frequencies at a rotational Reynolds number Re in the range of 8×105 to 9×105. At Re≳106, a multiple of independent frequencies appear in the spectrum that indicate a transition to turbulence. This seems to be consistent with the experiments of Daily and Nece [ASME J. Basic Eng. 82, 217 (1960)] for the Reynolds number at which transition to weak turbulence is observed and with the theoretical scenario of Ruelle and Takens [Commun. Math. Phys. 20, 167 (1967)] for the transition to turbulence.

CFDMARK: A CFD-based benchmark for high-performance computer systems

CFDMARK is a benchmark specifically devised to gauge the performance of computer systems used in the execution of CFD codes. It differs from the industry standard benchmarks such as LINPACK by measuring system performance on real CFD test cases. These consist of six models built into the general-purpose, two-dimensional, multiphase, pressure-correction-based CFD code, CASCADE. They range in complexity from a simple moving lid cavity problem to a two-phase blast furnace simulation. The CFDMARK is calculated on the basis of the performance of these tests. A total of 17 computers—ranging from a 386 PC to a CRAY Y-MP supercomputer—were evaluated, and their performance was ranked according to CFDMARK. The results for 14 machines are presented here. The performance ranking according to the more representative CFDMARK is significantly different from that produced by LINPACK.

Precise calculation of effective emissivity of a diffuse cylindro-inner-cone with a specular lid

A mathematical model for calculating precisely the effective emissivity distribution ∊a of a diffuse cylindro-inner-cone with a plane specular lid is presented. The exchange factors that comprise the kernels of the integral equations for evaluating ∊a have been derived using the image method and contour integration. For the usual case of a highly reflective specular lid, values of ∊a throughout the cavity are slightly lower than when all surfaces are diffuse. On the other hand, if the intrinsic emissivity of the specular lid is numerically the same as the diffuse emissivity of the rest of the cavity walls (an uncommon practical case), ∊a is marginally higher in the specular lid cavity.