A. N. Mullick

Numerical Analysis of Convective Transport of Fly Ash-water Slurry Through a Horizontal Pipe

The thermal transport of solid-liquid suspension under turbulent flow condition is not well understood because of the complex interaction between the solid particles and the turbulent carrier fluid. The solid particles may enhance or suppress the rate of heat transfer and turbulence depending on their size and concentration. In the present paper, a three-dimensional numerical simulation is carried out in order to study the pressure drop and heat transfer characteristics of a liquid-solid slurry flow in a horizontal pipe. The simulation is performed by using the algebraic slip mixture (ASM) model which is a part of the finite-volume based CFD software Ansys Fluent. The turbulence is handled by the RNG k - e model. A hexagonal shape and cooper type non-uniform three-dimensional grid is created to discretize the computational domain. Spherical fly ash particles, with mass median diameter of 13μm for an average flow velocity ranging from 1-5 m/s and particle concentrations within 0-40% by volume for each velo...

Flow Development through a Duct and a Diffuser Using CFD

In the present paper an extensive study of rectangular cross-sectioned C-duct and C-diffuser is made by the help of 2-D mean velocity contours. Study of flow characteristics through constant area duct is a fundamental research area of basic flu id mechanics since the concepts of potential flow and frictional losses in conduit flow were established. C-ducts are used in aircraft intakes, combustors, internal cooling systems of gas turbines, ventilation ducts, wind tunnels etc., while d iffuser is mechanical device usually made in the form of a gradual conical expander intended to raise the static pressure of the fluid flowing through it. Flow through curved ducts is more complex compared to straight duct due to the curvature of the duct axis and centrifugal forces are induced on the flowing flu id resulting in the development of secondary motion (normal to the primary flow d irect ion) which is manifested in the form of a pair of contra-rotating vortices. For a diffuser in addition to the secondary flow, the diverging flow passage, which causes an adverse stream wise pressure gradient, can lead to flow separation. The combined effect may result n non uniformity of total pressure and total pressure loss at the exit . A comparat ive study of different turbulent models available in the Fluent using y  as guidance in selecting the appropriate grid configuration and turbulence models are done. Standard k-ε model and RSM models are used to solve the closure problem for both the constant area duct and the diffuser. It has been observed that the Standard k-e model predicts the flow through the constant area duct and the diffuser within a reasonable domain of the y  range.

Characteristics of Fluid Flow through Microchannels

The microfluidics devices have recently attracted tremendous interest due to its potential of bringing novel applications into reality in various fields. However, the challenges in the design of microfluidics devices still remain since all aspects of fluid flow in microchannels have not been yet fully understood. Microfluidics is a vast and rapidly evolving research field. This report presents major findings in the literature on fundamentals of flow physics in microchannels. The review is intended to provide an extensive overview on the available knowledge base as well as the areas that require intensive investigation. It includes an extensive parametric study on effect of the wall roughness, entrance conditions, friction factor and pressure drop on flows in microchannels.

Flow Investigation through Annular Curved Diffusing Duct

In the present investigation the distribution of mean velocity, static pressure and total pressure are experimentally studied on an annular curved diffuser of 30° angle of turn with an area ratio of 1.25 and centerline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent and then a series of parametric investigations are conducted with same centre line length and inlet diameter but with different area ratios varying from 1.25 to 2 with change in angle of turn 30° to 75°.The measurements were taken at Reynolds number 2×105 based on inlet diameter and mass average inlet velocity. Predicted results of coefficient of mass averaged static pressure recovery (30%) and coefficient of mass averaged total pressure loss (21%) are in good agreement with the experimental results of coefficient of mass averaged static pressure recovery (26%) and coefficient of mass averaged total pressure loss (17%) respectively. Standard k‐e model in Fluen...

Flow Investigation Through a 30° Turn Diffusing Duct in Subsonic Flow Regime

Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate effective operation of the combustor by reducing the total pressure loss. The performance characteristics of these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of axial velocity, transverse velocity, mean velocity, static and total pressures are experimentally studied on a curved diffuser of 30° angle of turn with an area ratio of 1.27. The centreline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent, the commercial CFD software. The measurements of axial velocity, transverse velocity, mean velocity, static pressure and total pressure distribution were taken at Reynolds number 1.9 × 105 based on inlet diameter and mass average inlet velocity. The mean velocity and all the three components of mean velocity were measured with the help of a pre-calibrated five-hole pressure probe. The velocity distribution shows that the flow is symmetrical and uniform at the inlet and exit sections and high velocity cores are accumulated at the top concave surface due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The mass average static pressure recovery and total pressure loss within the curved diffuser increases continuously from inlet to exit and they attained maximum values of 35% and 14% respectively. A comparison between the experimental and predicated results shows a good qualitative agreement between the two. Standard k-e model in Fluent solver was chosen for validation. It has been observed that coefficient of pressure recovery Cpr for the computational investigation was obtained as 38% compared to the experimental investigation which was 35% and the coefficient of pressure loss is obtained as 13% in computation investigation compared to the 14% in experimental study, which indicates a very good qualitative matching.Copyright