Research Projects

Since 2009, I have been actively involved in several research projects for my M.Sc. and PhD studies, as well as independent research. My main area of interest and expertise is in the analysis of thermo-fluid systems, with application in industrial aerodynamics, cooling technologies, porous media , and biomedical systems. I have used analytical techniques, along with computational fluid dynamic (CFD) and experimental methods to conduct my research.

Below, you can find a brief description of my projects:

Optimization of Slotted Airfoils to Improve Aerodynamic Performance

Feasibility of increasing lift and decreasing drag by drilling narrow span-wide channels near the leading edge of NACA 4412 airfoils is investigated. It is proposed to drill two-segment slots that allow some of the incoming air to flow through them and then exit from the bottom surface of the airfoil. Such slots can result in an increased local pressure and thereby higher lift. Length, width, inlet angle and exit angle of slots are varied to determine optimum configurations. Aerodynamic performance at different angles of attack (AoAs) and the chord-based Reynolds number of 1.6E+6 is investigated. It is concluded that longer and narrower slots with exit streams more aligned with the air flowing below the airfoil can result in a higher lift. Also, in order to keep the slotted airfoils beneficial for AoAs greater than zero, it is proposed to (a) slightly lower the slot position with respect to the original design, and (b) tilt up the first-leg by a few degrees. For the best design case considered, an average improvement of 8% is observed for lift coefficient over the entire range of AoA (with the maximum increase of 15% for AoA=0), without any significant drag penalty.

A Novel Hybrid Turbulence Model: DES-ASM

Turbulent air flow over an NACA 4412 airfoil is investigated computationally. To overcome the near-wall inaccuracies of higher order turbulence models such as Large Eddy Simulation (LES) and Detached Eddy Simulation (DES), it is proposed to couple DES with algebraic stress model (ASM). Angles of attack of 0 and 14 degrees are studied for an airfoil subjected to flow with Re=1.6E+6. Distribution of the pressure coefficient at airfoil surface and the chordwise velocity component at four locations near the trailing edge are determined. Results of the baseline DES and hybrid DES-ASM models are compared against published data. It is demonstrated that the proposed hybrid model can slightly improve the flow predictions made by the DES model. Findings of this research can be used for the improvement of near-wall flow predictions for wind turbine applications.

Gas Turbine Blade Internal Cooling

In this project, the turbulent flow and heat transfer in a fast spinning two-pass channel is studied. The channel represents the small cooling channels drilled inside gas turbine blades to assist with the heat removal from the hot surfaces of the blade. This channel has a square cross-section with the size of 50.8 mm (2"), and the first and second leg lengths of 514 mm and 460 mm, respectively. The air flow rate and the rotation speed of the shaft are such that the Reynolds number of up to 34,000 and Rotation numbers of up to 0.75 are examined. Several computational fluid dynamics (CFD) simulations are conducted for this study, and the results indicate that higher rotation numbers can result in better mixing of the air in the channel, which yields more uniform temperature distribution and higher heat removal rates.

An experimental test setup is also designed, fabricated, and assembled at UWM. In this setup, the bottom surface of the channel is provided with adjustable electrical heaters, while the other sides of the channel are well insulated. A total of 12 wireless thermocouples is deployed to measure the temperature of air along the channel. Air flow rate and the rotation speed of the shaft are both adjustable through using variable frequency drive (VFD). The current experimental results show good agreement with CFD predictions.

(left) The entire experimental setup

(right) a closer look at the test section, the heater, the thermocouples and the slip ring.

Sample CFD results of normalized temperature on the horizontal mid-plane, for a rotating channel with Ro=0.65, ω=1530 rpm, U_in=12.5 m/s

Drying of Porous Media Exposed to Turbulent Flow

The isothermal drying of a porous medium in the form of a square bluff body resting on a flat surface while being exposed to turbulent air flow is investigated. The porous medium is represented by a pore-network model consisting of a network of volume-less nodes connected to each other via narrow throats. As the air flows past the water-saturated network, the water evaporates in the network and the evaporated water-vapors diffuse through the air inside the network to advect away in the outside domain. This work presents a powerful new method to predict drying of a porous medium by coupling the outside-the-network flow and transport with the inside-the-network drying and liquid redistribution.

The water redistribution inside the network is predicted by the invasion-percolation algorithm after assuming the dominance of capillary forces over viscous and gravity forces. The outside velocity field is first obtained using the k-Omega model in ANSYS Fluent package. Then, the velocity field is used in a finite-volume based code in order to solve for mass transfer outside the network using the regular convective-diffusive species transport equation. The drying mechanism and vapor transport inside the pore network is coupled with the outside mass-transfer simulation. The effects of the outside-flow Reynolds number and different turbulent-flow models on several global drying parameters such as evaporation or drying rate, cumulative drying time, and top-surface saturation were studied. The concentration boundary layer thickness (CBLT), which is employed to set the mass-transfer boundary condition in pore network simulations and has been hitherto taken as constant in the literature, was found to change not only with position on the network top, but was also found to decline with time due to the drying of the network top. (Figure shows the saturation of 5 different realizations of a square-shape pore-network at 5 distinct time steps)

Research Projects

Optimization of Slotted Airfoils to Improve Aerodynamic Performance

A Novel Hybrid Turbulence Model: DES-ASM

Gas Turbine Blade Internal Cooling

Drying of Porous Media Exposed to Turbulent Flow

Other Projects:

- Multiscale Modeling of a Chemofilter Device for Filtering Chemotherapy Toxins from Blood

- Two Phase Blood Flow within Bifurcated Vessels

- Compressible Transonic Flow over an Airfoil

- Evaporation of Multi-component Liquid Mixtures from Porous Polymer Wicks

- Permeability Estimation using Image Processing

- Polymer Wick Design Optimization