Magesh Thiruvengadam

Shear-Driven Liquid Film in a Duct

Abstract Two-dimensional flow simulations of shear-driven thin liquid film by turbulent air flow in a duct is performed using the Reynolds Averaged Navier Stokes and continuity equations along with the Volume of Fluid (VOF) model that is part of the FLUENT-CFD code. The purpose of this study is to determine the suitability of using this code/model for predicting reported measurements of shear driven liquid film in a duct. Both a laminar and a turbulent flow models were examined for the liquid film flow region to assess their impact on film thickness and velocity. The Low Reynolds number k-ε turbulence model is utilized for simulating the turbulent air and film flow. Simulated results for the distributions of the air velocity, liquid film velocities along with the liquid film thickness as a function of inlet air and liquid film flow rates are presented. Simulated results show that the film thickness decreases but surface film velocity increases with increasing air flow rate; film thickness and surface film velocity increase with increasing film flow rate; the imposed laminar film flow model produces linear velocity distribution inside the film but the turbulence film flow model produces a nonlinear velocity distribution; the developing thin film influences significantly the air velocity distribution; and these results compare favorably with measured behavior.

Three-Dimensional Mixed Convection in Plane Symmetric-Sudden Expansion: Bifurcated Flow Regime

Simulations of three-dimensional laminar mixed convection in a vertical duct with plane symmetric sudden expansion are presented to illustrate the effects of the buoyancy-assisting force and the duct’s aspect ratio on flow bifurcation and heat transfer. The stable laminar bifurcated flow regime that develops in this geometry at low buoyancy levels leads to nonsymmetric temperature and heat transfer distributions in the transverse direction, but symmetric distributions with respect to the center width of the duct in the spanwise direction. As the buoyancy force increases, due to increases in wall heat flux, flow bifurcation diminishes and both the flow and the thermal fields become symmetric at a critical wall heat flux. The size of the primary recirculation flow region adjacent to the sudden expansion increases on one of the stepped walls and decreases on the other stepped wall as the wall heat flux increases. The maximum Nusselt number that develops on one of the stepped walls in the bifurcated flow regime is significantly larger than the one that develops on the other stepped wall. The critical wall heat flux increases as the duct’s aspect ratio increases for fixed Reynolds number. The maximum Nusselt number that develops in the bifurcated flow regime increases as the duct’s aspect ratio increases for fixed wall heat flux and Reynolds number.

A diesel particulate matter dispersion study inside a single dead end entry using dynamic mesh model

Three-dimensional simulations of diesel particulate matter (DPM) distribution inside a single dead end entry with a push-pull system for the load-haul-dump (LHD)-truck loading and truck hauling operations were carried out using ANSYS FLUENT computational fluid dynamics (CFD) software. The loading operation was performed for a fixed period of time. Then dynamic mesh technique in FLUENT was used to study the impact of truck motion on DPM distribution. The resultant DPM distributions are presented for the cases when the vehicles were fitted with and without diesel particulate filters (DPF). The results from the simulation can be used to determine if the areas inside the single dead end entry exceed the current U.S. regulatory requirement for DPM concentration (160 µg/m3). This research can guide the selection of DPM reduction strategies and improve the working practices for the underground miners.

Rigid multi-body kinematics of shovel crawler-formation interactions

Large capacity shovels are deployed in surface mining operations for achieving economic bulk production targets. These shovels use crawler tracks for effective terrain engagement in these environments. Shovel reliability, maintainability, availability and efficiency depend on the service life of the crawler tracks. In rugged and challenging terrains, crawler wear, tear, cracks and failure are extensive resulting in prolonged downtimes with severe economic implications. In particular, crawler shoe wear, tear, cracks and fatigue failures can be expensive in terms of maintenance costs and production losses. No fundamental research has been undertaken to understand the crawler-formation interactions in challenging and rugged terrains in surface mining operations. This study forms the foundations for providing long-term solutions to crawler failure problems. The kinematic equations governing the crawler-formation interactions have been formulated to characterise the crawler motions during shovel production. These equations capture the motions governing the link pin joint, oil sand terrain joint and driving constraints based on the multi-body rigid theory. Crawler propel is achieved by using prescribed velocities along a translational degree of freedom (DOF) and a translational and rotational DOF. The crawler kinematic solutions show that the 3-D crawler–terrain model results in 132 DOFs and requires dynamic modelling to obtain the unknown degrees of freedom. A 3-D virtual prototype model is built to capture the crawler-formation interaction in MSC ADAMS based on the rigid body crawler kinematics. The virtual prototype simulator is supplied with mass properties of crawler shoe, mass, stiffness and damping characteristics of oil sand and external loads due to machine weight and contact forces to obtain the time variation of position, velocity and acceleration for the crawler–terrain engagement for given driving constraints. The results from the driving constraints yield a non-linear longitudinal motion of the crawler track assembly. The crawler track lateral and vertical displacements during translation-only motion fluctuates with maximum magnitudes of 0.7 and 3.6 cm. Similarly the fluctuating longitudinal, lateral and vertical velocities and accelerations have maximum magnitudes of 0.22, 0.046 and 0.56 m/s and 7.41, 1.73, and 34.9 m/s2, respectively. This research provides a strong foundation for further study on developing flexible crawler track model for predicting crawler shoes dynamic stress distributions, cracks development and propagation and fatigue analysis during shovel operations.