Varangrat Juntasaro

Kasetsart University | KU · Department of Mechanical Engineering

Dynamic gut-on-a-chip platform allows better recreation of the intestinal environment in vitro compared to the traditional static cell culture. However, the underlying mechanism is still not fully discovered. In this study, the shear stress behavior in a gut-on-a-chip device with porous membrane subjected to peristalsis motion is numerically invest...

A numerical study is performed to investigate the effect of buoyancy on the cooling performance of leading edge cooling of a rotating turbine blade under the real operating condition at baseload. The Double Swirl Cooling (DSC) configuration is simulated using the SST k-ω turbulence model that proves to be the most accurate for impinging flow under...

The present work is aimed to investigate whether the modification to the bend geometry of a multipass internal cooling passage in a gas turbine blade can enhance heat transfer and reduce pressure drop. The two-pass channel and the four-pass channel are modified at the bend from the U shape to the bulb and bow shape. The first objective of the work...

A semi-active flapping foil, which is a heaving foil attached to a torsional spring, efficiently generates thrust. In this report, the propulsive characteristics of such foils are studied using a boundary element method. The numerical investigation is performed to clarify the effects of foil inertia and resonance. It is found that the flapping prop...

The present study deals with numerical investigation of a semi-active flapping foil of which the kinematics is characterized by an imposed heave motion and a free pitch motion. A torsion spring is attached to the foil and acts to restore the foil parallel to the advance velocity. The prescribed flapping foil has been simulated using a boundary elem...

The accuracy of predicting turbulence induced secondary flows is crucially important in many industrial applications such as turbine blade internal cooling passages in a gas turbine and fuel rod bundles in a nuclear reactor. A straight square duct is popularly used to reveal the characteristic of turbulence induced secondary flows which consists of...

During the last decade, there have been two RANS-based transition models used in commercial CFD software: θ γ Re − model and L k model. The present work is aimed to combine the merit parts of both transition models. Apart from the base turbu-lence model, the transition model proposed here is composed of the original L k -equation and the new γ alge...

The realistic simulation of cavitation on a marine propeller is important for the efficient design of the propeller. However, the flow characteristic that occurred on the marine propeller is complicated and difficult to predict due to the combined effects of turbulence, cavitation, and multiphase phenomena. There is still currently no turbulence mo...

The interfacial layer of nanoparticles has been recently shown to have an effect on the thermal conductivity of nanofluids. There is, however, still no thermal conductivity model that includes the effects of temperature and nanoparticle size variations on the thickness and consequently on the thermal conductivity of the interfacial layer. In the pr...

The flow over a stepped spillway is free surface, multiphase and turbulent. Moreover, a recirculation region occurs at each step of the spillway. The flow characteristic is hence complicated and difficult to predict. In previous work on stepped spillways (Chen et al. Journal of Hydraulic Engineering, ASCE, 128 (7), 683–688 and Xiangju et al. Scienc...

The adaptive mesh refinement (AMR) method is developed for three-dimensional turbulent complex flows in clean rooms using the finite volume method with a collocated grid arrangement. Clean rooms have many interesting and complex flow characteristics especially the secondary flows and the recirculation regions. The accurate numerical solution of the...

The performance of different turbulence models and source-term models for the turbulent separated particle-laden flow is investigated. The accuracy of various turbulence models is firstly evaluated without any modification by the source-term model. The considered models are the k–ω SST model; the standard, the RNG and the realizable k–ε models with...

The new concept of turbulence modeling is proposed as an attempt to simulate the effect of turbulence on the flows as realistically as possible. The turbulence effect is fundamentally not the diffusion phenomena that the concept of eddy viscosity models is based on. It is rather the convection phenomena that are responsible for the turbulence effec...

The development of CFD code with the use of parallel computing in conjunction with the multigrid and multiblock methods is presented for calculating an incompressible flow through a two-dimensional T-junction. The finite volume method (FVM) is used to discretize the governing equations of the steady laminar flow. The QUICK scheme is applied for the...

The present work concerns the evaluation of the damping functions in the low-Reynolds-number non-linear q−ζ turbulence model to improve the accuracy of the predicted results. Different expressions for the damping function ( f μ) are studied to find the most suitable use in low-Reynolds-number turbulence models, followed by the re-optimisation of th...

A Reynolds-stress expression used in a non-linear eddyviscosity turbulence model is developed based on the Direct Numerical Simulation (DNS) data of fully developed turbulent channel flow of Kim et al. (1987) for both Re T = 180 and 395. The data are initially used to analyze the accuracy of various Reynolds-stress expressions used in the non-linea...

A comparative study of a number of flux-limiters based on MUST methodology is presented in this paper to find the most suitable flux-limiter to be used in unsteady and steady convective flow calculations. The accuracy and convergence behaviour of these flux-limiters are assessed in five pure convection problems: (1) rotation of a cone-shaped scalar...

The multigrid method adopted in conjunction with the parallel computing is presented. The standard multigrid doubling the mesh size in all directions, called full-coarsening technique, suffers from the partitioning of data for parallel computing. To remedy this problem, the semicoarsening technique should be used instead. This work is aimed to pres...

This paper is aimed to present the combination of the parallel computing and the multigrid method on the Navier-Stokes solver. The combination is based on the concept of the object-oriented programming (OOP), which consists of 4 independent modules: Grid Generation, Navier-Stokes Solver, Multigrid Method and Parallel Computing modules. The multigri...

The characteristics of flow field in the internal passage of turbine blade cooling are affected by the combined effects of the secondary flows and the rotation of the blade. These secondary flows occur in the near wall regions and have the great effect on the characteristics of the primary flow and the cooling rate. Accurate modeling of the flow in...

Two-phase turbulent flows of dilute concentration of discrete particles occur in many industrial and natural processes such as the combustion of liquid and fuels, cyclone separators, pneumatic transport of particulate material, and environmental particulate transport. In these applications, turbulence modulation will occur. Turbulence modulation re...

An Adaptive Mesh Refinement method (AMR) is presented for predicting turbulent flow in a three-dimensional domain. The low-Reynolds-number linear k turbulence model of Launder and Sharma [4] is employed to predict turbulent flow. In this paper, AMR is the local refinement method of the active type that relies on high numerical errors or gradient. T...

A numerical technique to investigate the transitional boundary layer flow over a flat plate subjected to freestream turbulence and non-zero pressure gradient is presented. The technique solves the full equations of fluid motion rather than the boundary-layer equations which are neglect the y-momentum equation and preserve the pressure variation onl...