أحمد علي شاكر السعدي

The study investigates different methods to minimize the drag coefficient (C D) without ignoring the safety factor related to the stability of a vehicle, i.e., the lift coefficient (C L). The study was carried out by employing an SUV car analyzed numerically using one of the CFD software, Ansys. Four different models such as realizable k–ε, standard k–ω, shear stress transport k–ω, and Reynolds stress model (RSM). The considered models have been validated with experimental data and found in good agreement. The considered inlet velocity varies from 28 to 40 m/s, the results showed that the drag coefficient and the stability are both improved by applying a modification on the roof of the considered car.

The streamlined exterior shapes of tall buildings are important to reduce the effect of the wind. Therefore, an examination of different techniques for the exterior design of tall buildings is required. This study aims to analyses some tall buildings to select the most streamlined design in order to reduce high wind risks. The benchmark used in the current study is a building with a height of 120 m and a triangular cross-section with a side length of 20 m. A square cross-section twisted building design is used as a modified model in tall buildings of about 120 m. The rotation angle of the building is 45° for each twisted path. Six configurations of this type of building are tested with different radiuses of fillet on their edges, which are 0, 1, 2, 3, 4, and 5 m respectively. All geometries of the buildings are created by SolidWorks, while mesh and simulations are achieved using ANSYS Fluent. Great agreement is obtained between the current results and the previous related study for the benchmark. Using twisted buildings with a fillet of 5 m can lead to a reduction of the drag coefficient of about 27.5% relative to the benchmark. Wind in a horizontal direction can be reduced by using twisted geometry. But in terms of separation, using a fillet with a large radius can lead to avoid early separation of air.

In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05).

An experimental and theoretical study for heat transfer through thermoelectric cooling system in this paper was presented. An experimental work was conducted to evaluate the performance of a thermoelectric module fitted to a sun flower heat sink with a similar sized heat source. The experimental investigation was done to evaluate the effect of TE input voltage, flow rates of cooling air and heat source (heating element) power input on the performance of a thermoelectric cooling system. Four low heating load (1.7, 2.4, 3.6 and 5 W) were used and hot side was fitted to a sunflower heat sink with forced convection. Experimental results show that the increasing of cooling air flow rates improves system performance, while increasing in applied TE voltage leads to deterioration it. The COPmax obtained is about 4.7 at 2V TE voltages and 5W heating load, and then decreased sharply as voltage further increased and reaches 0.13 at 12V. The results of the current study show that all Thermo-electric Cooling system recorded temperatures increase with increasing in heating load at a constant TE voltage and air flow rate. In addition to that the Tc decreases and Th increases with the increment of input voltage and that can lead to increase of the air temperature passing over heat sink. TE performance is highly affected by air flow rate. The theoretical result validated experimentally and shows an acceptable agreement between them.

This study concentrates on different aerodynamic drag reduction techniques to reduce the aerodynamic drag coefficient and increase the stability of a three-dimensional full-size road vehicle. There are many modern aerodynamic add-on devices and modifications which are used in this research. All of these aerodynamic devices and modifications are used individually or in combination. Optimization of mesh parameters is carried out by analysis of the mesh data. Unstructured tetrahedral cells are used throughout the global domain to cope with the geometrical complexity of the car model. Inflation layers with prismatic cells are used to provide an accurate estimation of the velocity profiles near the surfaces of the car. Computational Fluid Dynamics (CFD) analysis based on steady state Reynolds-Averaged Navier-Stokes (RANS) turbulence modelling is used. Realizable k–ε, Standard k-ω, Shear Stress Transport k-ω (SST) and a Reynolds Stress Model (RSM) turbulence models are considered in this study. Good agreement has been achieved between the calculated drag coefficient for the baseline models and the experimental data for all types of turbulence models. It is found that the use of some types of aerodynamic modifications and devices can reduce the aerodynamic drag coefficient and increases the car stability.