Kamarul Arifin Ahmad

Navigating hazardous environments, such as areas with fire risks, wild animal activity, or inaccessible terrains, poses significant challenges, necessitating the development of bio-inspired robotic systems. This study focuses on the biomechanical design and kinematic analysis of a spider-mimicking robot, specifically examining quad and hexa-legged configurations to optimize movement efficiency and stability. The research employed 3D Computer-Aided Design (CAD) in Fusion 360 to model and simulate the robot's leg framework, analyzing deformation, tension, and strain. Fused Deposition Modelling (FDM) with Poly Lactic Acid (PLA) material was used for component fabrication, chosen for its balance of lightweight properties and structural integrity, validated through stress analysis. A single limb’s forward and reverse kinematics were studied, enabling the development of optimized gait patterns. SIMSCAPE Multibody in MATLAB was utilized for dynamic simulations, and Proportional Derivative (PD) and Proportional Integral Derivative (PID) controllers were tested to evaluate trajectory tracking accuracy and stability. Results show that the six-legged configuration exhibits superior stability with a 15% improvement in gait cycle efficiency and a 20% reduction in energy consumption per stride compared to the four-legged counterpart. The use of PID controllers further enhanced performance, achieving a 12% improvement in settling time and reducing oscillations in trajectory tracking tasks. The choice of PLA material ensured durability under operational loads, with minimal deformation over repeated stress cycles. Servomotor selection and configuration were tailored to optimize torque and speed, enabling precise leg control. This study highlights the potential of bio-inspired robots to advance robotic mobility through optimized kinematics and material choices.

Ice accretion on aircraft wings poses a critical safety challenge during operational flights as it alters the aerodynamic performance the wing profile and increases structural loads acting on it. Therefore, it has become crucial to understand the thermodynamic and fluid dynamic behavior of ice formation over the airfoil surface to address this issue. This study investigates the heat and mass transfer characteristics of a two-dimensional NACA0012 airfoil during in-flight icing under various flow conditions. The research aims to model the ice accretion process, analyze its impact on aerodynamic performance, and assess the heating requirements for ice mitigation. Throughout the study, a numerical approach was employed using the FENSAP-ICE simulation suite in ANSYS Fluent, which integrates the Reynold’s-Averaged Navier-Stokes equations with the K-ω SST turbulence model to model airflow and ice formation. Additionally, the study investigated icing at airflow velocities of 80, 102, 150, and 200 m/s, analyzing the resulting ice formation as a result of varying flow speeds, its influence on lift and drag coefficients across different angles of attack, and the heating loads necessary for ice removal using thermal balance calculations. The results of the study showed strong consistency between the simulated ice accretion patterns and droplet collection efficiency and the experimental findings reported in literature. Therefore, validating the use if FENSAP-ICE for such analyses. Furthermore, it was also found that the ice build-up over the airfoil significantly degrades its aerodynamic performance with reductions in lift and increases in drag coefficients. The obtained findings provide valuable insights for expanding the numerical analysis performed in this study to design effective ice protection systems for aircrafts under diverse operational conditions.

An airway is likely to be contacted with virus. When the virus is adhered to the airway by breath, some humans maybe get infected. Therefore, the infection risk is important to predict by evaluating quantitatively the adhesion area and the amount of virus. The airway consists of the nasal cavity (such as the maxillary sinus, ethmoid sinus, frontal sinus, and sphenoidal sinus), pharynx, larynx, trachea, bronchi, and lungs. In this study, CFD analysis of transport process of virus concentration in the airway was conducted by considering adhesion and breathing waveform, and the infection risk at sinuses were predicted. The 3D geometry of the nasal cavity can be constructed from 2D-CT (Computed Tomography) image data utilizing ITK-SNAP. The flow within the nasal cavity is assumed to an incompressible, unsteady (pulsatile flow), and turbulent. The continuity equation and the Navier-Stokes equations are used in computational fluid dynamics (CFD) analysis. In CFD analysis, the boundary condition at the inlet is defined that the pressure is zero, and the concentration is dependent on inlet mass flow. The boundary condition at outlet is defined that the velocity is the simulated breathing waveform, and the gradient of concentration is free. The wall boundary condition of concentration is adhesion. It has been determined that the Ethmoid Sinus exhibits a heightened propensity for viral adhesion within the nasal cavity, based on the evaluation of the amount of adhesion. In addition, it was found that the flow is complexed by considering the breathing waveforms. It was found that the concentration diffusion in Maxillary Sinus (Region 1) and Ethmoid Sinus (Region 2) was increased by the generated vortexes. Besides, it was found that the amount of adhesion increases more than twice by considering the adhesion.

Aircraft structures are frequently exposed to damage from environmental factors and operational wear, leading to the development of surface imperfections such as cracks. These imperfections can increase aerodynamic drag, a phenomenon known as excrescence drag. To mitigate these effects and quickly restore structural integrity, repair patches, often made from aluminium alloys and tailored to the damage, are applied following guidelines set out in the Aircraft Battle Damage Repair (ABDR) manuals. This paper investigates the aerodynamic performance impacts of applying such patches to two prominent airfoil models: the symmetric NACA 0012 and the cambered NACA 2412. Utilizing advanced computational tools including CATIA V5 for 3D modelling and CFD++ for fluid dynamics simulation, this study examines changes in aerodynamic characteristics such as lift, drag, and pressure distribution under various flow conditions. The research particularly focuses on quantifying the aerodynamic changes introduced by the patches through detailed analyses of lift curves, drag polars, and pressure coefficient (Cp) plots. Our findings aim to provide insights into the trade-offs involved in patch repairs, exploring how different patch configurations influence airfoil performance. This contributes to the development of optimized repair strategies that ensure minimal aerodynamic disruption while extending the operational lifespan of aircraft components.

The increase in pollution levels in recent years has increased the prevalence of pulmonary diseases. The accumulation of pollutant particles in the pulmonary tract is speculated to be one of the major reasons for the increase in chronic cases. This necessitates the study of the mechanism of particle deposition in human airways to develop better drug delivery systems. Aerosolized forms of drugs are commonly used to treat pulmonary diseases. The current study employed computational fluid dynamics (CFD) and discrete element method (DEM) techniques to study airflow patterns and particle deposition phenomena. An idealized 3D CAD model was developed based on available literature. A discretized finite-volume model was tested to ensure an independent solution. A user-defined function (UDF) was used to simulate realistic breathing dynamics for the respiration cycle. The aerosol particles of the calculated volume were mixed into the airflow domain. The analysis was conducted using ANSYS FLUENT CFD solver. This study found several regions of high turbulence in the upper human airways, with secondary flow structures exhibiting bifurcations and the glottal region. The study also found that the oral cavity and oropharynx regions with higher turbulence intensity had a concentrated deposition of particles. Most of the aerosol particles (5μm) were transported into the alveolar sacs, where they were absorbed into the bloodstream. The oral cavity and oropharynx have the highest pressure and particle deposition efficiency, while the trachea plays a crucial role in particle deposition during inhalation due to weak oscillatory flows and turbulence, especially in the tracheal region and lower respiratory tract. The oral cavity has the highest efficiency at 7.32%, while the trachea has the lowest at 0.4%. The overall deposition efficiency across all regions is 9.078%.This study did not account for the breakup of aerosol particles. Aerosol particles can break apart due to airflow and collisions, affecting their size and deposition efficiency. Ignoring this breakup could lead to inaccurate results, making accurate dosimetry essential for inhalation studies

Aircraft cabins have high occupant densities and may introduce the risk of COVID-19 contamination. In this study, a segment of a Boeing 767 aircraft cabin with a mixing type of air distribution system was investigated for COVID-19 deposition. A section of a Boeing 737-300 cabin, featuring four rows with 28 box-shaped mannequins, was used for simulation. Conditioned air entered through ceiling inlets and exited near the floor, simulating a mixed air distribution system. Cough droplets were modeled using the Discrete Phase Model from two locations: the centre seat in the second row and the window seat in the fourth row. These droplets had a mean diameter of 90 µm, an exhalation velocity of 11.5 m/s and a flow rate of 8.5 L/s. A high-quality polyhedral mesh of about 7.5 million elements was created, with a skewness of 0.65 and an orthogonality of 0.3. The SIMPLE algorithm and a second-order upwind finite volume method were used to model airflow and droplet dynamics. It was found that the ceiling accounted for the maximum concentration followed by the seats. The concentration of deposits was almost 50% more when the source was at window as compared to the centre seat. The Covid particles resided for longer duration when the source was at the centre of the cabin than when it was located near the widow.