Papers by Keyword: Rotating Disk

Abstract: This research focuses on the crucial task of identifying the viscous sublayer in improving wet cleaning processes. Computational fluid dynamics (CFD) is employed to manipulate fluid properties and process parameters for optimizing cleaning efficiency. The research findings encompass the evolution of thickness across the wafer radius, characterization of the wavy air-liquid interface, velocity profile within the liquid, and measurement of the viscous sublayer's thickness. Key findings highlight the significance of small-scale turbulent structures, the competition between Coriolis and viscous forces, and the successful utilization of CFD LES (Large Eddy Simulation) for quantifying and visualizing the viscous sublayer and eddy flow.

Abstract: The prominence of present work is to investigate the axisymmetric mixed convective magnetohydrodynamic (MHD) flow of a Casson nanofluid over a stretching variable thickened rotating disk in the presence of heat source/sink and velocity slip surface boundary condition. Besides, thermal buoyancy and viscous dissipation effects are examined. Convective heat and zero nanoparticles mass flux conditions at the boundaries of the disk are implemented. Von Karman similarity transformation is employed to formulate highly nonlinear coupled ordinary differential equations and solved via Optimal Homotopy Analysis Method (OHAM). The computed numerical values are presented graphically to predict the features of the embedded parameters. A new method (slope of the linear regression) is used to analyze the computed data of Skin friction coefficient, Nusselt number and Sherwood number. It is found that the power law exponent parameter plays a dominant role within the velocity, thermal and concentration boundary layer regions. Further, the fluid flow is opposed due to the magnetic field and velocity slip results in a reduced velocity boundary layer.

Abstract: The effects of thermal and exponential space dependent heat sources (THS and ESHS) on magneto-nanoliquid flow across a rotating disk with uniform stretching rate along radial direction are scrutinized in this communication. H₂O based nanoliquids containing aluminium (AA 7075) and titanium (Ti₆Al₄V) alloy nanoparticles are considered. The AA7075 is made up of 90% Al, 5-6% Zn, 2-3% Mg, 1-2% Cu with additives such as Fe, Mn and Si etc. The flow is driven due to rotating disk with uniform stretching of the disk. Impacts of Joule and viscous heating are also deployed. The multidegree ordinary differential equations are formed via Von Karman transformations. The obtained non-linear BVP is solved by Runge-Kutta-Fehlberg based shooting approach (RKFS). Graphical illustrations depict the impacts of influential parameters on flow fields. The skin friction and Nusselt number are also calculated. Results pointed out that the thermal boundary layer growth stabilizes due to the influence of ESHS aspect. Velocities of nanofluid are superior than that of nanoliquid. Furthermore, the thermal performance of base liquid is outstanding when we added titanium alloy nanoparticles in comparison with aluminium alloy nanoparticles.

Abstract: In fertilizers industries the granulation is an essential operation to form pellets with good quality. The granular product has improved handling, hardness, solubility, resistance to segregation and meets requirements such as the size, shape and particle size distribution through appropriate manipulation of the process variables. There are several types of granulators, however, this work is intended to study a granulator known as rotating disk, which promotes agitation of the particles by rotating around its axis. Although these devices are used industrially, cannot be found in the literature many details about the fluid dynamics in these operations. To study the fluid dynamics behavior of these particles on a rotation disk was analyzed the variables: rotation axis and filling degree. It was verified the existence of flow regimes which depends on these variables: rolling, cascading and centrifugation. Also, it was evaluated the dynamic angle of repose, that characterizes the rolling regime. This work aimed to obtain results of fluid dynamics that describe the behavior of solids flowing in a rotating disk. Thus, to meet the objectives of this work, simulations was carried out through the techniques of Computational Fluid Dynamics (CFD) and Discrete Element (DEM) to evaluate different parameter values: restitution coefficient (η), friction coefficient (μ) and the coefficient of elasticity (k) of the linear model "spring-dashpot" to find a good set of parameters that characterizes this system.

Abstract: In this work, elastic stress and deformation distribution through the radial direction of FG rotating disks are accurately calculated by employing the complementary functions method. A parabolic variation of the thickness is used for the concave, linear and convex thickness profiles. The inner and outer surfaces of the FG disk are assumed to be ceramic-rich and metal-rich, respectively. Between these two surfaces material properties vary radially according to Mori-Tanaka grading rule. After confirming the present results with the analytical results for the uniform disk with power-law graded rule, the effect due to many parameters such as angular velocity, metal-ceramic pairs, and material grading index on the stresses and displacements is investigated.

Abstract: A modified large-size MOCVD reactor is developed to produce uniform and large-volume epitaxy thin film layer of gallium nitride (GaN). The full governing equations for continuity, momentum, energy and chemical species are solved numerically. It is investigated how thermal flow field, and the operating parameters affect molar concentration of each reactant, and the thin film uniformity. These parameters are involved such as the chamber pressure (100-700 torr), susceptor rotation rate (100-800). In this paper, the simulation results from these listed parameters shows that an optimum epitaxy layer can be achieved in the large-size reactor.

Abstract: This study concerns the analysis of thermoelastic characteristics of non-uniform rotating disks subjected to thermal load including the effect of inertia force due to rotation of the disk. The solutions up to the elastic limit yield stress of the material are obtained under plane stress assumption by taking variation on total potential energy. The solution algorithm is implemented with the help of MATLAB computational simulation software. The analysis is carried out for various disk geometries and temperature distribution profiles. The effect of temperature on elasticity modulus is also investigated and some numerical results are presented and discussed in the form of limit angular speed under thermo-mechanical loading and reported in dimensionless form.

Abstract: The flow of an incompressible viscous power-law fluid over an infinite rotating disk with uniform suction or injection is studied. The governing differential equations, which are partial and coupled, are simplified to a set of ordinary differential equations by generalized Karman similarity transformation. Numerical solutions of the non-linear two point boundary value problem are obtained by multi-shooting method. The effects of the power-law index and the porous parameter on the velocity fields are discussed for shear thinning fluids.

Abstract: Bioceramics used in biomedical applications must exhibit specific behaviors. In scaffolds, for instance, the degradability of bioceramics is important to allow the cell ingrowth. Therefore, the dissolution of calcium phosphates increases the ionic concentrations around the interface implant–bone, favoring a more rapid bone apposition to the graft surface. The dissolution takes place under static or dynamic conditions, but the latter is usually not performed under rigorous hydrodynamic control. In the present work, two bioceramics, β-tricalcium phosphate and β-tricalcium phosphate substituted by magnesium, were produced by pressing and sintering to form disks. They were characterized by XRD, Raman, ICP, SEM, AFM and photometric test. The influence of chemical composition in the dissolution test was conducted through strict control of the hydrodynamic conditions. The disks were rotating in a precise speed, in order to produce a dissolution under the well-controlled mass transfer. Subsequently, the calcium release was evaluated in a simulated infectious environment using pH equals to circa 4. Thus, it was possible to evaluate the fraction of dissolution related to mass transfer or surface reactions for a large rotation speed range. The magnesium added to the bioceramic inhibits the total dissolution when compared to pure tricalcium phosphate, probably related to more dense and less soluble ceramic. Moreover, the mass transfer affects relatively less the magnesium tricalcium phosphate than pure tricalcium phosphate.

Abstract: The study of boundary layer flow and heat transfer near a rotating disk with nanofluids is investigated numerically. Three types of nanoparticles, namely, silver Ag, copper Cu and alumina Al₂O₃ with water as the base fluid are considered. The results show that the momentum boundary layer thicknesses shortens as the nanoparticle volume fraction increases, whereas thermal boundary layer thickness elongates for increasing ϕ. It is found that the reduced skin-friction coefficients and heat transfer rateat the rotating surface increase linearly with nanoparticle volume fractionϕ. The surface heat transfer rate for Cu-water nanofluid is higher than those of the otherswhen ϕ>0.02, even though the nanoparticle Ag has higher thermal conductivity than that of copper Cu.