Field Of Fluid Dynamics Research Articles

Multiphysics Numerical Simulation and Geometric Optimization of a Micronozzle for the MEMS Thruster

This paper reports a numerical research on MEMS (microelectromechanical system) micronozzles through multiphysics coupling simulation along with design optimization based on simulation results. The micronozzle, which is a core component of the electrothermal microthruster, features a micron-scale geometry, a 2-dimensional (2D) Laval configuration, a rectangular cross section, and a highly thermal conductive silicon wall due to MEMS fabrication. As a result, viscous loss in the flow field and heat transfer to the nozzle wall can strongly influence nozzle performance, namely, thrust force and specific impulse. To accurately understand the flow field inside the micronozzle and how the highly thermal conductive silicon wall interacts with gas flow, a numerical simulation that couples fluid dynamics field and solid heat transfer field is employed in the research. The influence of different structural parameters on micronozzle performance is then investigated to set a basis for design optimization. The optimum design of the linear expander micronozzle is obtained through constrained optimization by linear approximation. To further improve micronozzle performance, the bell-shaped expander is adapted. The optimization result shows that the bell-shaped expander is not suitable for micronozzle featuring 2D Laval configuration, and the reason behind the phenomenon is thoroughly discussed.

Machine Learning based algorithms for modeling natural convection fluid flow and heat and mass transfer in rectangular cavities filled with non-Newtonian fluids

The importance of studying double-diffusive fluid flows along with the significance of non-Newtonian fluids have been well recognized in the fluid dynamics field for scientific and practical purposes. However, and given the ever-rising complexity of such non-linear flows, the conventional simulation methods are confronted with problems related to accuracy and required computation time and resources. As a result, the Machine Learning approach qualifies as a promising solution to said limitations. The present study investigates the application of Machine Learning models to study double-diffusive natural convection in rectangular cavities filled with non-Newtonian fluids. The flow is governed by four dimensionless parameters, namely: thermal Rayleigh number RaT, Lewis number Le, buoyancy ratio N, and power-law behavior index n, employed as input features. To precisely model fluid flow, three characteristics are predicted: flow intensity |ψc|, average Nusselt number Nu¯, and average Sherwood number Sh¯ using four machine learning models: Artificial Neural Networks (ANN), Random Forests (RF), Gradient Boosted Decision Trees (GBDT), and Extreme Gradient Boosting (XGBoost). The analysis of investigated models’ fine-tuned architectures using various tools confirms the non-linear complexity of the problem and allows to explore and discuss in details the inner-workings of each model. The ANN predicts the test data with R2=0.9999,R2=0.9996, and R2=0.9999 followed by XGBoost with R2=0.9979,R2=0.9802, and R2=0.9979, and that for |ψc|, Nu¯, and Sh¯, respectively. The study shows the strong and correlated effects of RaT and n on the flow characteristics. The models’ generalization is further examined using fluids with power-law behavior indexes outside the learning range. The present paper validates the choice of Machine Learning approach as a promising solution to model non-Newtonian double-diffusive fluid flows and encourages future works in this direction.

Numerical simulation of atmospheric-pressure surface dielectric barrier discharge on a curved dielectric with a curvilinear mesh

A numerical simulation method for atmospheric-pressure surface dielectric barrier discharge (DBD) is presented using a structured curvilinear mesh that is fitted to a curved dielectric surface. The numerical method is based on the plasma fluid model with general coordinate transformation, which is widely used in the field of the computational fluid dynamics. The calculations of a potential distribution formed by a line electrode and a planar surface DBD are performed to confirm the validity of the proposed method. We conducted numerical simulations of the DBD on a wavy surface using the proposed method to investigate the characteristics of the DBD on a curved surface. The propagation velocity of the discharge front and the electric field strength of the discharge front changed depending on the surface shape. The proposed method enables the calculation of the DBD on a complex surface and widens the application range of the numerical simulation in the field of discharge physics.

Acoustic Response of a Vibrating Elongated Cylinder in a Hydrodynamic Turbulent Flow

The present paper contains the results of the numerical analysis of the interaction between a Newtonian incompressible turbulent flow and a linear elastic slender body, together with the influence of the fluid–structure interaction (FSI) on the noise generation and propagation. The purpose is to evaluate the differences in term of acoustic pressure between the case where the solid body is rigid (infinite stiffness) and the case where it is elastic (finite stiffness). A partitioned and implicit algorithm with the arbitrary Lagrangian–Eulerian method (ALE) is used for the interaction between the fluid and solid. For the evaluation of the turbulent fluid motion, we use a large eddy simulation (LES) with the Smagorinsky subgrid scale model. The equation for the solid is solved through the Lagrangian description of the momentum equation and the second Piola–Kirchoff stress tensor. In addition, the acoustic analogy of Lighthill is used to characterize the acoustic source (the slender body) by directly using the fluid dynamic fields. In particular, we use the Ffowcs Williams and Hawkings (FW-H) equation for the evaluation of the acoustic pressure in the fluid medium. As a first numerical experiment, we analyze a square cylinder immersed in a turbulent flow characterized by two different values of stiffness: one infinite (rigid case) and one finite (elastic case). In the latter case, the body stiffness and mean flow velocity are such that they induce the lock-in phenomenon. Finally, we evaluate the differences in terms of acoustic pressure between the two different cases.

An efficient communication strategy for massively parallel computation in CFD

With the development of high-performance computers, it is necessary to develop efficient parallel algorithms in the field of computational fluid dynamics (CFD). In this study, a novel parallel communication strategy based on asynchronous and packaged communication is proposed. The strategy implements an aggregated communication process, which requires only one communication in each iteration step, significantly reducing the number of communications. The correctness and convergence of the novel strategy are demonstrated from both theoretical and experimental perspectives. And based on the real vehicle CHN-T model with 140 million meshes, a detailed performance comparison and analysis is performed for the novel strategy and the traditional strategy, showing that the novel strategy has significant advantages in terms of scalability. Finally, the strong scalability and weak scalability tests are carried out separately for the CHN-T model. The strong scaling efficiency can reach 74% with 10.5 billion meshes and 256,000 cores. The weak scaling parallel efficiency can reach 90% with 10 billion meshes and 179,000 cores. This research work has laid an important foundation for the development of the fast design of aircraft and cutting-edge numerical methods.

The Nirenberg Problem on Half Spheres: A Bubbling-off Analysis

Abstract In this paper, we perform a refined blow-up analysis of finite energy approximated solutions to a Nirenberg-type problem on half spheres. The latter consists of prescribing, under minimal boundary conditions, the scalar curvature to be a given function. In particular, we give a precise location of blow-up points and blow-up rates. Such an analysis shows that the blow-up picture of the Nirenberg problem on half spheres is far more complicated that in the case of closed spheres. Indeed, besides the combination of interior and boundary blow ups, there are nonsimple blow-up points for subcritical solutions having zero or nonzero weak limit. The formation of such nonsimple blowups is governed by a vortex problem, unveiling an unexpected connection with Euler equations in fluid dynamic and mean fields type equations in mathematical physics.

Monitoring the evaporation of a sessile water droplet with a chromatic confocal measurement system.

In this Letter, a chromatic confocal measurement system with high stability and accuracy is presented to monitor the evaporation of a sessile water droplet. The stability and accuracy of the system are tested by measuring the thickness of a cover glass. To compensate for the measurement error caused by the lensing effect of the sessile water droplet, a spherical cap model is proposed. Together with the parallel plate model, the contact angle of the water droplet can also be obtained. The evaporation process of sessile water droplet under different environment is monitored experimentally in this work, which demonstrates the potential application of chromatic confocal measurement system in the field of experimental fluid dynamics.

Isogeometric variational multiscale modeling of stably stratified flow over complex terrains

Numerical modeling of stratified boundary layer over complex terrain has been an ongoing challenge in the field of environmental fluid dynamics. In this work, we present a computational framework aiming to tackle that challenge. The key components of the framework are residual-based variational multiscale method, isogeometric analysis, and weak imposition of Dirichlet boundary condition. The framework is validated against a laboratory experiment on strongly stratified flow past a three-dimensional bell-shaped hill. Good agreement is observed for qualitative flow physics, with the predicted occurrences of flow separation, recirculation, and hydraulic jump closely matching those in the experiment. In addition, the dividing-streamline height and wavelength of lee wave computed from the present framework compare well to the theoretical predictions. We show that the present framework is able to tackle various degrees of stratifications. The effect of weak imposition of Dirichlet boundary condition on the performance of the framework is also examined. This paper is concluded with an outlook toward applying the present framework to modeling microscale stratified flow past real-world terrains by simulating stratified flow past a two-dimensional environmental terrain.

Externally applied magnetic force effect on the Couette flow of a viscous incompressible fluid with heat source/sink

PurposeThis study aims to investigate the effect of externally applied magnetic force and heat transfer with a heat source/sink on the Couette flow with viscous dissipation in a horizontal rotating channel. The magnetic force is added to the governing equations. The effects of fluid flow parameters are observed under the applied magnetic force. In this system, the magnetic force is applied perpendicular to the plane of the fluid flow. In recent years, the magnetic field has renewed interest in aerospace technology. The physical and theoretical approach in the multidisciplinary field of magneto fluid dynamics (MFD) is applied in the field of aerospace vehicle design.Design/methodology/approachAuthors use the perturbation method to solve and find the approximate solutions of differential equations. First, convert the partial differential equation to ordinary differential equation and calculate the approximate solutions in two cases. The first solution got by assuming heat generating in the fluid and the second one got when heat absorbing. After applying the external magnetic force, the effects of various fluid parameters velocity, temperature, skin friction coefficient and Nusselt number are found and discussed using tables and graphs.FindingsIt is found that the velocity of the fluid has decreased tendency when the rotation of the fluid and magnetic force on the fluid increases. The temperature of the fluid, Prandtl value and Eckert number increased when the heat source generated heat. When heat absorbs the heat, sink parameter increases and the temperature of the fluid decreases. Also, while heat absorbs, the temperature increases when the Prandtl value and Eckert number increase.Originality/valueThe skin friction coefficient on the surface increases, when the rotation parameter and the magnetic force parameter of the fluid increase. In the case of heat generating, the Nusselt number increased, while the Eckert number and Prandtl numbers increased. Also, the Nusselt number has larger values when the heat source parameter has near the constant temperature, and it has smaller values when the temperature varies. In the case of heat-absorbing, the Nusselt number decreased when the Eckert and Prandtl numbers increased. Also, the Nusselt number varies up and down while the heat absorbing parameter increases.

Improved convergence of the spectral proper orthogonal decomposition through time shifting

Spectral proper orthogonal decomposition (SPOD) is an increasingly popular modal analysis method in the field of fluid dynamics due to its specific properties: a linear system forced with white noise should have SPOD modes identical to response modes from resolvent analysis. The SPOD, coupled with the Welch method for spectral estimation, may require long time-resolved datasets. In this work, a linearised Ginzburg–Landau model is considered in order to study the method's convergence. Spectral proper orthogonal decomposition modes of the white-noise forced equation are computed and compared with corresponding response resolvent modes. The quantified error is shown to be related to the time length of Welch blocks (spectral window size) normalised by a convective time. Subsequently, an algorithm based on a temporal data shift is devised to further improve SPOD convergence and is applied to the Ginzburg–Landau system. Next, its efficacy is demonstrated in a numerical database of a boundary layer subject to bypass transition. The proposed approach achieves substantial improvement in mode convergence with smaller spectral window sizes with respect to the standard method. Furthermore, SPOD modes display growing wall-normal and spanwise velocity components along the streamwise direction, a feature which had not yet been observed and is also predicted by a global resolvent calculation. The shifting algorithm for the SPOD opens the possibility for using the method on datasets with time series of moderate duration, often produced by large simulations.

URANS numerical simulations of pulsating flows considering streamwise pressure gradient on asymmetric diffuser

The paper focuses on implementing the wall model developed by Manhart, in Reynolds Averaged Navier - Stokes (RANS) turbulence models used in the field of Computational Fluid Dynamics (CFD). This wall model considers the influence of the streamwise pressure gradient in addition to the existing wall models used in the usual CFD codes. In the present work, two RANS numerical simulations are carried out using the k-ω Shear Stress Transport (SST) turbulence model on an asymmetric diffuser geometry. One numerical simulation is carried out using the implementation of the Manhart wall model in the k-ω SST turbulence model, and the other numerical simulation is performed using the standard formulation of the k-ω SST turbulence model. The numerical simulations carried out using the Manhart wall model and the standard formulation of the k-ω SST are compared with experimental measurements made on the asymmetric diffuser experimental installation. The numerical simulations are carried out using a free, open-source CFD tool, Code_Saturne. The comparisons between numerical simulations and the experimental data are in good agreement in the boundary layer of the flow inside the diffuser. The Manhart wall model had a faster convergence resulting in a shorter simulation time.

Emerging Trends in Machine Learning for Computational Fluid Dynamics

The renewed interest from the scientific community in machine learning (ML) is opening many new areas of research. Here we focus on trends in ML that are providing opportunities to advance the field of computational fluid dynamics (CFD). We discuss synergies between ML and CFD that have already shown benefits, and we also assess areas that are under development and may produce important benefits in the coming years. We believe that it is also important to emphasize a balanced perspective of cautious optimism for these emerging approaches.

A cell-based smoothed finite element model for non-Newtonian blood flow

Smoothed Finite Element Method (S-FEM) has drawn increasing attention in the field of computational fluid dynamics (CFD) and the present work seeks to make further contribution to this growing field of S-FEM by simulating for the non-Newtonian blood flow. This investigation took the form of Streamline Upwind Petrov-Galerkin in conjunction with Stabilized Pressure Gradient Projection (SUPG/SPGP) to alleviate the spatial oscillation and instability problems. The validation of the cell-based S-FEM (CS-FEM) combined with SUPG/SPGP was carried out by the blood flow over a backward-facing step. The performances of the presented method were explored by the blood flow in the carotid bifurcation and blood flow in the intracranial segment of internal carotid artery. Impressively, the results exhibit good features of the CS-FEM on solving severely distorted mesh vis-a-vis the standard finite element method (FEM). The presented method could realize the accurate prediction in the mentioned complex blood flows as the same as Finite Volume Method software STAR-CCM+.

Neural network-based eddy-viscosity correction for RANS simulations of flows over bi-dimensional bumps

The improvement of Reynolds-Averaged Navier–Stokes (RANS) models has become one major issue in the field of computational fluid dynamics (CFD). Despite being largely used in industry, eddy-viscosity models still lack accuracy even for simple flow configurations. In this scenario, we investigate new data-driven approaches for the development of machine-learning augmented turbulence models. The main contribution of this work is providing a machine-learning oriented turbulence model that estimates directly the eddy-viscosity correction, and that does not require the use of additional transport equations. The configuration studied is a turbulent flow over a parametric set of bumps characterized by different levels of curvature, pressure gradient and flow separation. An artificial neural network (ANN) model is trained, cross-validated and tested to construct a mapping between the input features and the two quantities of interest : the eddy viscosity discrepancy and the true eddy viscosity estimated from the numerical database. We showed that the ANN predicts the eddy viscosity discrepancy with good accuracy but when coupled to a RANS solver, the improved solution is very noisy. On the other hand, when predicting the eddy viscosity directly, the ANN-based model successfully reproduce the general flow-field behavior, in terms of pressure and skin-friction distributions. The present methodology was proved to be robust even in predicting extrapolated flows. The methods and results of this work provide useful guidance for turbulence model developers.

Conserved relativistic Ertel’s current generating the vortical and thermodynamic aspects of space–time

Motivated by Aoki et al.’s recent research on conserved charges and entropy current, we reinvestigated the conservation of relativistic Ertel’s current, which has received little attention outside the field of geophysical fluid dynamics. Ertel’s charge is an important indicator of the correlation between vortex vectors and entropy gradient fields in Earth’s meridional heat transport. We first show that in the generalized Hamiltonian structure of baroclinic fluids, the duality between the total energy and the Casimir as a function of Ertel’s charge plays an important role in the nonrelativistic case. Then, by extending the result to relativistic cases, we show that this finding has far-reaching implications not only for space–time issues in cosmology but also for the foundation of quantum field theory. An especially important finding is that, as an unreported dual form of the Einstein field equation, we identify a special equation satisfied not only by the vortex tensor field generated by the conserved charge but also by the Weyl tensor in interpreting the physical nature of the metric tensor [Formula: see text], which appears in the cosmological term [Formula: see text].

Biomechanical Sensing Using Gas Bubbles Oscillations in Liquids and Adjacent Technologies: Theory and Practical Applications.

Gas bubbles present in liquids underpin many natural phenomena and human-developed technologies that improve the quality of life. Since all living organisms are predominantly made of water, they may also contain bubbles—introduced both naturally and artificially—that can serve as biomechanical sensors operating in hard-to-reach places inside a living body and emitting signals that can be detected by common equipment used in ultrasound and photoacoustic imaging procedures. This kind of biosensor is the focus of the present article, where we critically review the emergent sensing technologies based on acoustically driven oscillations of bubbles in liquids and bodily fluids. This review is intended for a broad biosensing community and transdisciplinary researchers translating novel ideas from theory to experiment and then to practice. To this end, all discussions in this review are written in a language that is accessible to non-experts in specific fields of acoustics, fluid dynamics and acousto-optics.

Mechanism of hysteresis and uncontrolled deflection in jet vectoring control based on Coanda effect

We investigated the mechanism of hysteresis and uncontrolled deflection in jet vectoring control based on the Coanda effect. Thrust vectoring control based on the Coanda effect is highly applicable in the field of fluid dynamics because they can achieve jet deflection control with a simple geometric structure and low energy consumption. However, the hysteresis and uncontrolled deflection phenomena considerably hinder the practical application of these technologies. We designed a new passive fluidic thrust vectoring control model to analyze the mechanism of these disadvantages. We developed a synchronous pressure, force, and flow field measurement system to investigate the evolutions of flow structures and their effects on wall pressure distribution and vectoring force. The characteristics of the key flow structures, including the separation bubble, the secondary flow, and the backflow, were investigated. The transient features of jet attachment and jet detachment were researched to identify the transition of near-wall flow structures and wall pressure distribution during jet uncontrolled deflection. The mechanism of uncontrolled deflection is that the formation/breakdown of the separation bubble changes the flow state of the backflow, and the near-wall mass flux balance is collapsed. This causes a dramatic change in the jet vectoring angle, which is out of the valve's control. During attachment, the shear layer first touches the wall and forms a separation bubble, and then, the bubble shrinks. During detachment, the bubble first enlarges and then breaks down. Therefore, the formation and breakdown of the separation bubble correspond to different valve positions, which is the mechanism of hysteresis.

Viscoelastic and Viscoplastic Glucose Theory (VGT #31): Applying VGT with Two Different CGM Sensor Measured 2-Hour Postprandial Plasma Glucose (PPG) values from 240 Liquid Egg Meals and 191 Solid Egg Meals as the Strain, along with the PPG Change Rate Multiplied by a Viscosity Factor of Average Carbs/ Sugar Amounts for Each Egg Meal Type as the Stress, and then

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake influences which have dealt with “time-dependency” issues. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. But, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. The postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via postmeal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept” of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #29): Applying viscoelastic Glucose Theory with CGM Sensor Measured Fasting Plasma Glucose (FPG) Values as the Strain along with the FPG Change Rate Multiplied by a Viscosity Factor as the Stress, and Finally Utilizing the Viscoelastic Perturbation Model to Calculate the Predicted FPG Values to Compare Against the Measured FPG Values Based on GH-Method:

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work to earn a master’s degree in Biomechanics under Professor James Andrews. At that time, he used the spring and dashpot models to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. He also took additional graduate courses in the field of fluid dynamics and thermodynamics. Since then, many advancements have been made in the biomechanics branch, especially with human body tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relaxation for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. The author’s research focuses on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. Fasting plasma glucose (FPG) has nothing to do with either diet or exercise during sleep hours and is mainly relying on the health condition of both liver and pancreatic beta cells, which produces glucose and releases insulin, to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #30): Applying VGT with Two Different CGM Sensor Measured 3-Hour Postprandial Plasma Glucose (PPG) Values from 240 Liquid Egg Meals and 191 Solid Egg Meals as the Strain, Along with the PPG Change Rate Multiplied by a Viscosity Factor of Average Carbs/Sugar Amounts for Each Egg Meal Type as the Stress, and then Applying

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work on UI campus to earn a master’s degree in Biomechanics under Professor James Andrews. At that time, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. He also took additional graduate courses in the field of fluid dynamics and thermodynamics along the way of his schooling years. Since then, many advancements have been made in the biomechanics branch, especially with human body tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. The author’s research focuses on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. The postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept” of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.