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Lattice Boltzmann Method for Simulation of Nanoparticle Brownian Motion and Magnetic Field Effects on Free Convection in A Nanofluid-filled Open Cavity with Heat Generation/Absorption and Non Uniform Heating on the Left Solid Vertical Wall
Get PDFThis article reports a numerical study of nanoparticle Brownian motion and magnetic field effects by natural convection in a nanofluid-filled open cavity with non uniform boundary condition. Lattice Boltzmann Method (LBM) is used to simulate nanofluid flow and heat transfer. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo-Kleinstreuer-Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity and effective viscosity is considered and examined. Simulations have been carried out for the pertinent parameters in the following ranges: Rayleigh number (Ra=103−106), Hartmann number (Ha=0-60), nanoparticle volume concentration (Φ=0–0.04) and heat generation or absorption coefficient (q=−10, −5, 0, 5, 10). The numerical results show a decrease in heat transfer with an increase in particle volume fraction. In addition, it is observed that the Brownian motion greatly influences the heat transfer rate depending on the Hartmann number, Rayleigh number and nanoparticle solid volume fraction. Additionally, in the presence of the heat generation or absorption, the Brownian motion effect on heat transfer at Ra=103 is more pronounced than other Rayleigh numbers and the least effect is observed at Ra= 106
Influence of functionalization on the structural and mechanical properties of graphene
Get PDFMolecular dynamics simulations were applied in order to calculate the Young’s modulus of graphene functionalized with carboxyl, hydroxyl, carbonyl, hydrogen, methyl, and ethyl groups. The influence of the grafting density with percentages of 3, 5, 7, and 10% and the type of distribution as a single cluster or several small clusters were also studied. The results show that the elastic modulus is dependent on the type of functional groups. The increasing coverage density also evidenced a decrease of the Young’s modulus, and the organization of functional groups as single cluster showed a lesser impact than for several small clusters. Furthermore, the bond length and angle distribution probability analyses reveal that lengths and angles are affected with increasing functionalization suggesting more out-of-plane displacements of the carbon atoms within the graphene structure
Cycle Time Reduction in Injection Molding by Using Milled Groove Conformal Cooling
Get PDFThis paper presents simulation study on Milled Grooved conformal cooling channels (MGCCC) in injection molding. MGCCC has a more effective cooling surface area which helps to provide efficient cooling as compared to conventional cooling. A case study of Encloser part is investigated for cycle time reduction and quality improvement. The performance designs of straight drilled are compared with MGCCC by using Autodesk Moldflow Insight (AMI) 2016. The results show total 32.1% reduction of cooling time and 9.86% reduction of warpage in case of MGCCC as compared to conventional cooling
Generalized Rayleigh Wave Dispersion in a Covered Half-space Made of Viscoelastic Materials
Get PDFDispersion of the generalized Rayleigh waves propagating in a covered half-space made of viscoelastic materials is investigated by utilizing the exact equations of the theory of linear viscoelasticity. The dispersion equation is obtained for an arbitrary type of hereditary operator of the materials of the constituents and a solution algorithm is developed for obtaining numerical results on the dispersion of the waves under consideration. Dispersion curves are presented for certain attenuation cases and the influence of the viscosity of the materials is studied through three rheological parameters of the viscoelastic materials which characterize the characteristic creep time, long-term values and the mechanical behaviour of the viscoelastic material around the initial state of the deformation. Numerical results are presented and discussed for the case where the viscoelasticity of the materials is described through fractional-exponential operators by Rabotnov. As the result of this discussion, in particular, how the rheological parameters influence the dispersion of the generalized Rayleigh waves propagating in the covered half-space under consideration is established
Inverse Analysis of Origin-Destination matrix for Microscopic Traffic Simulator
Get PDFMicroscopic traffic simulations are useful for solving various traffic- related problems, e.g. traffic jams and accidents, local and global environmental and energy problems, maintaining mobility in aging societies, and evacuation plan- ning for natural as well as man-made disasters. The origin-destination (OD) matrix is often used as the input to represent traffic demands into traffic simulators. In this study, we propose an indirect method for estimating the OD matrix using a traffic simulator as an internal model. The proposed method is designed to output results that are consistent with the input of the simulator. The method consists of the following steps: (1) calculating link traffic volume from the OD matrix, and (2) updating the matrix. The estimated matrix is updated iteratively until it converges to a predefined tolerance level. Numerical experiments are then conducted using the proposed method on a grid network and on a representation of an actual road network. Finally, we discuss the characteristics of the proposed method and the non-negative constraint for the traffic volume
An adaptive load stepping algorithm for path-dependent problems based on estimated convergence rates
Get PDFA new adaptive (automatic) time stepping algorithm, called RCA (Rate of Convergence Algorithm) is presented. The new algorithm was applied in nonlinear finite element analysis of path-dependent problems. The step size is adjusted by monitoring the estimated convergence rate of the nonlinear iterative process. The RCA algorithm is relatively simple to implement, robust and its performance is comparable to, and in some cases better than, the automatic load incrementaion algorithm existent in commercial codes. Discussions about the convergence rate of nonlinear iterative processes, an estimation of the rate and a study of the parameters of the RCA algorithm are presented. To show the capacity of the algorithm to adjust the increment size, detailed discussions based on results for different limit load analyses are presented. The results obtained by RCA algorithm are compared with those by ABAQUS®, one of the most powerful nonlinear FEA (Finite Element Analysis) commercial software, in order to verify the capability of RCA algorithm to adjust the increment size along nonlinear analyses
Performance of Compact Radial Basis Functions in the Direct Interpolation Boundary Element Method for Solving Potential Problems
Get PDFThis study evaluates the effectiveness of a new technique that transforms domain integrals into boundary integrals that is applicable to the boundary element method. Simulations were conducted in which two-dimensional surfaces were approximated by interpolation using radial basis functions with full and compact supports. Examples involving Poisson’s equation are presented using the boundary element method and the proposed technique with compact radial basis functions. The advantages and the disadvantages are examined through simulations. The effects of internal poles, the boundary mesh refinement and the value for the support of the radial basis functions on performance are assessed
3D Numerical Simulation of Effect of Antiangiogenic Factor Angiostatin on Blood Flow and Interstitial Fluid Pressure in the Metastatic Tumor
Get PDFMetastatic tumor blood perfusion and interstitial fluid transport based on 3D microvasculature response to inhibitory effect of angiostatin are investigated in this paper. 3D blood flow、interstitial fluid transport and transvascular flow are described by the extended Poiseuille’s, Darcy’s and Starling’s law, respectively. Numerical solutions reveal that angiostatin can promote improved blood perfusion and decrease elevated interstitial fluid pressure within the metastatic tumor microenvironment. Moreover, angiostatin can increase interstitial convection within the tumor and result in more efficient drug delivery and penetration within the metastatic tumor, which suits well with the experimental observations. Together, our results may provide therapeutic implications for further clinical anti-angiogenic cancer therapy
On the Crack Spreading in Traverse Section of Bovine Bone
Get PDFBone is an important natural hierarchical biomaterial which supports human body and protect organs. Its mechanical property has been researched extensively. In this experimental work, 3D microscope and scanning electron microscope (SEM) were used to research crack expansion on bovine femur cortical bone transverse section. Softwares such as image J and Photoshop were used in image and data analyses. Our results suggested that the interface energy of extending through osteons is smaller than the interface energy of extending along cement lines. Cracks are more likely to extend through osteons. Further investigations are needed to reduce errors and validate our findings
Structural Damage Detection in Framed Structures using Under Foundation Settlement/ Rotation of Bases
Get PDFThis paper describes the damage detection in framed structures due to the vertical support settlement and rotation of footing bases. The damage detection procedure proposed by Nobahari and Seyedpoor (2013) is used to detect the damage in the members of the frame. In the present study, instead of using the flexibility matrix (referred here as original flexibility matrix) method, the generalized flexibility matrix is used in the same algorithm and the results are compared. The algorithm uses flexibility matrix and strain energy concept to detect the damage in the members. The behaviour of the frame is discussed through changes observed in flexibility in the associated degree of freedom. Finally, the results indicate that, the damage index determined by generalized flexibility matrix method is more reliable than using the original flexibility matrix based method for the problem of settlement and rotation of footing base