arXiv subjects

Aigbe Awenlimobor

Publications and source records attributed to Aigbe Awenlimobor.

3 recordsLinked to original sources

arXiv2025

Method for backtracking the layer thermal conductivities of multilayer thin film structure using coupled Newton Raphson approach and 3-omega approach

The thermal conductivity of thin films is commonly estimated using the 3-omega experimental method. When calibrating the test setup, it is customary to use a specimen with a known thermal conductivity for validation. However, when determining the thermal conductivity of samples with unknown values, numerical approximations can provide a means to validate experimental results and ensure the integrity of the setup. A simple analytical or finite element analysis (FEA) method can be used to achieve this. For multilayer systems of unknown layer thermal conductivities, the 3-omega experimental setup only provides information about the overall bulk thermal conductivity of the system. To obtain the individual layer thermal conductivities, a combined experimental and numerical approach can be used. This article presents a novel method for backtracking the layer thermal conductivities of a multilayer thin film structure using a coupled 3-omega experimental and Newton-Raphson numerical approach. The method is validated using high-fidelity data obtained from literature.

physics.comp-ph↗

arXiv2025

Determination of Preferred Fiber Orientation State based on Newton-Raphson Method using Exact Jacobian

Fiber orientation is an important descriptor of the microstructure for short fiber polymer composite materials where accurate and efficient prediction of the orientation state is crucial when evaluating the bulk thermo-mechanical response of the material. Recent macroscopic fiber orientation models have employed the moment-tensor form in representing the fiber orientation state which all require a closure approximation for the higher order orientation tensors. In addition, various models have been developed to account for rotary diffusion due to fiber-fiber and fiber-matrix interactions which can now more accurately simulate the experimentally observed slow fiber kinematics in polymer composite processing. Traditionally explicit numerical IVP-ODE transient solvers like the 4th order Runge-Kutta method have been used to predict the steady-state fiber orientation state. Here we propose a computationally efficient method based on the Newton-Raphson iterative technique for determining steady state orientation tensor values by evaluating the exact derivatives of the moment-tensor evolution equation with respect to the independent components of the orientation tensor. We consider various existing macroscopic fiber orientation models and several closure ap-proximations to ensure the robustness and reliability of the method. The performance and stability of the approach for obtaining physical solutions in various homogeneous flow fields is demonstrated through several examples. Validation of the obtained exact derivatives of the orientation tensor is performed by benchmarking with results of finite difference techniques

math.NA↗

arXiv2025

The Effect of Shear-Thinning Rheology on the Dynamics and Pressure Distribution of a Single Rigid Ellipsoidal Particle in Viscous Fluid Flow

This paper evaluates the behavior of a single rigid ellipsoidal particle suspended in homogenous viscous flow with a power-law Generalized Newtonian Fluid (GNF) rheology using a custom-built finite element analysis (FEA) simulation. The combined effects of the shear-thinning fluid rheology, the particle aspect ratio, the initial particle orientation and the shear-extensional rate factor in various homogenous flow regimes on the particle's dynamics and surface pressure evolution are investigated. The shear-thinning fluid behavior was found to modify the particle's trajectory and alter the particle's kinematic response. Moreover, the pressure distribution over the particle's surface is significantly reduced by the shear-thinning fluid rheology. The FEA model is validated by comparing results of the Newtonian case with results obtained from the well-known Jefferys analytical model. Furthermore, Jefferys model is extended to define the particle's trajectory in a special class of homogenous Newtonian flows with combined extension and shear rate components typically found in axisymmetric nozzle flow contractions. The findings provide an improved understanding of key transport phenomenon related to physical processes involving fluid-structure interaction (FSI) such as that which occurs within the flow-field developed during material extrusion-deposition additive manufacturing of fiber reinforced polymeric composites. These results provide insight into important microstructural formations within the print beads.

physics.flu-dyn↗