VNUHCM Journal of Engineering and Technology

Application of CFD to optimize the design of twin-pod autonomous underwater vehicle

2025-06-25T17:44:56+07:00

This study explores the hydrodynamic characteristics of a distinctive unmanned underwater vehicle, the Twin-Pod Autonomous Underwater Vehicle (TPAUV). The TPAUV is composed of two torpedo-shaped buoyant bodies connected by a fixed wing and equipped with a propulsion system that includes two buoyancy engines and two thrusters. This innovative configuration allows the vehicle to move with exceptional versatility, maneuvering effectively in both vertical and horizontal directions. As such, the TPAUV is particularly suited for low-speed seabed survey missions, which require stability, precision, and efficient energy use in challenging underwater environments. To evaluate the TPAUV’s performance, the study employed advanced three-dimensional Computational Fluid Dynamics (CFD) simulations to perform a detailed analysis of its hydrodynamic properties. The analysis focused particularly on the turbulent flow generated by the propellers, which significantly influences vehicle behavior and energy efficiency. By assessing how fluid flow interacts with the vehicle’s structural components, the study aimed to optimize the TPAUV’s hydrodynamic performance while minimizing potential drag and turbulence-related inefficiencies. A standout feature of the TPAUV design is its ability to achieve a substantial separation between the center of gravity (CG) and the center of buoyancy (CB), ensuring exceptional stability during submerged operations. This feature is crucial for maintaining precise control and orientation, especially during complex seabed exploration tasks. Additionally, the study examined the hydrodynamic interactions between the two hulls, identifying both beneficial and adverse effects on the vehicle’s overall performance. Variables such as hull dimensions, shape effects, and the vehicle’s operating depth were investigated to better understand their influence on hydrodynamic interactions. Additionally, the relationship between drag force, lift force, and velocity, as well as the variation of hydrodynamic drag force over time, is also discussed in the study. The study highlighted specific areas where these interactions had the greatest and least impact, offering valuable insights into improving the TPAUV’s design. These findings not only validate the feasibility of the TPAUV’s unique configuration but also provide practical recommendations for enhancing the stability, efficiency, and reliability of underwater survey vehicles. This research serves as a foundational step toward advancing the design and control strategies of next-generation autonomous underwater vehicles.

Study on simulation and calculation of aerodynamic characteristics on airfoils

2025-06-30T22:15:57+07:00

Computational Fluid Dynamics (CFD) has emerged as an indispensable tool for simulating and analyzing the aerodynamic characteristics of aircraft components. This paper uses the open-source software OpenFOAM to determine the aerodynamic performance of a NACA 64008a airfoil. The simulations employ the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Spalart-Allmaras turbulence model to capture the turbulent effects. The computational methodology, mesh generation, boundary conditions, and initial conditions are validated with experimental data for the NACA 0012 airfoil. The simulations are then applied to predict the aerodynamic performance of the NACA 64008a airfoil. The results depict the lift, drag, and pressure distribution at various angles of attack. Detailed analysis of the pressure field around the airfoil provides insights into the formation and development of leading-edge and trailing-edge vortices, which play a crucial role in determining the overall performance. The pressure coefficient (Cp) distribution along the chord length (x/c) of the NACA 64008a airfoil at different angles of attack (AOA) is presented. The relationship between the lift coefficient (Cl) and the angle of attack (α) for the NACA 64008a airfoil is also investigated. Furthermore, the variation of the drag coefficient (Cd) with the angle of attack (α) for the NACA 64008a airfoil is examined. These insights can be used to guide future design optimization efforts

Investigation of factors affecting the channel sealing processing mode of microfluidic chips using spin coating technology

2025-07-01T00:05:58+07:00

Nowadays, the research and production of microfluidic chips for various applications in bio/chemical fields are attracting significant attention from scientists around the world. The fabrication of microfluidic chips typically involves two steps: creating open microchannels and subsequently sealing them. The sealing of these open microchannels is a critical step that determines the ultimate quality of the product. Adhesive bonding and solvent bonding are two commonly used approaches for sealing open channels. Both approaches require the creation of an adhesive layer or a solvent layer sandwiched between the two substrate surfaces to facilitate bonding under the influence of chemical and physical reactions. Therefore, controlling the process of creating this layer plays a vital role. To achieve this, spin coating is a technique often used to quickly and simply create thin coating layers owing to the centrifugal force. However, this method also has many limitations such as limited thickness control, uniformity issues, limited material compatibility, and limited control over film structure. In this study, the authors conducted an investigation of the factors affecting the formation of coating layers using the spin coating technique. The investigation results showed difficulties in choosing the substrate placement position and selecting the appropriate spinning speed for the coating material. Additionally, the authors propose the incorporation of a new force, in conjunction with centrifugal force, during the coating process, which demonstrates potential in mitigating the formation of distinctive thickness profiles by reducing the thickness in the central region of the coating

Polyvinyl Alcohol/Chitosan/Gelatin Hydrogel incorporated with betel leaves for enhanced wound care management

2025-07-23T15:58:07+07:00

In the rapidly advancing medical field, there is a significant demand for efficient, safe, and cost-effective wound healing solutions that address both infection control and tissue regeneration. Traditional wound dressings often fall short in managing complex wounds, particularly those susceptible to microbial contamination or inflammation. For these critical healthcare needs, the development of innovative material systems that facilitate rapid wound recovery is essential. This research explores the potential of a composite biomaterial based on Polyvinyl Alcohol (PVA), Chitosan, and Gelatin—three biocompatible and biodegradable polymers known for their unique physicochemical and biological properties. The blend is further enhanced by incorporating betel leaf extract, a natural antibacterial agent widely used in traditional medicine in Southeast Asia, including Vietnam. The synergistic combination of these components aims to create an optimized wound dressing that promotes faster healing, moisture retention, reduced inflammation, and antimicrobial protection. Chitosan contributes to hemostatic activity and antimicrobial resistance, Gelatin supports cellular adhesion and proliferation, while PVA improves structural integrity and flexibility. Betel leaf extract, rich in bioactive compounds like chavicol and eugenol, imparts potent antibacterial and anti-inflammatory properties. A series of formulations were prepared by varying the ratios of PVA, Chitosan, and Gelatin, and introducing different concentrations of betel leaf extract to evaluate mechanical properties, swelling behavior, degradation rate, and antibacterial activity. Surface morphology was examined using digital microscopy to assess homogeneity and distribution of betel particles. Among all combinations, a 2:1:1 ratio of PVA/Chitosan/Gelatin with 15% betel leaf content exhibited the most favorable characteristics. This study highlights the potential of using sustainable, natural resources to develop advanced wound dressings that are accessible, effective, and environmentally friendly, offering promising applications in biomedical and clinical settings.

Isolation and investigation of biological potential of endophytic fungi in Eleochararis dulcis

2025-07-24T10:03:52+07:00

The grass is a common wild plant in the river delta region of the Southwest region of Vietnam. They grow abundantly and flourish in saline-acidic areas. Native grasses interact with their endogenous microorganisms. However, there have not been many studies on this subject, especially the grass in Vietnam.

From the grass, the study isolated 3 endophytic fungi from the root. The results showed that the fungal strain with the highest P-decomposing ability was NR3 with a PO₄^3- content of 696.74 mg/L. All 3 strains were able to grow and develop, but the decomposing ability was not observed. In addition, all 3 fungal strains were able to synthesize N but the results were quite low. The ability to synthesize the plant hormone IAA in PDB medium with/without L-Tryptophan was investigated and quantified by spectrophotometry with Salkowski reagent. The results showed that in the environment without L-Tryptophan supplementation, strain NR3 had the highest IAA synthesis capacity with a total IAA content of 12.06 mg/L. In the environment with L-Tryptophan supplementation, the amount of IAA produced was higher, in which strain NR1 had an extracellular IAA content of 24.62 mg/L. The research results provided initial data on the biological capacity of endophytic fungi in the roots of reed grass, creating the premise for further studies.

A study on the determination of fuel injection timing based on the control of pressure synchronization in real-time for a Constant Volume Combustion Chamber

2025-06-25T10:22:57+07:00

The understanding of the diesel combustion mechanism is crucial in the optimization of fuel combustion efficiency and emission formation, a control method of the fuel injection timing and an experimental combustion measurement on a constant volume combustion chamber (CVCC) were carried out. A pre-combustion technique has been used to burn combustible gas mixtures, including acetylene, oxygen, and nitrogen, to generate diesel engine conditions. The created combustion pressure in CVCC was quantified by a piezoelectric transducer pressure sensor, and a microcontroller processed the consecutively recorded pressure data to determine the desired fuel injection timing, like diesel engine conditions, by real-time synchronization. Then the diesel combustion pressure, rate of heat release, and ignition delay were analyzed under conditions of fuel injection pressure, ambient temperature, and oxygen concentration corresponding to 1200 bar, 1000 K, and 21%, respectively. The obtained results revealed that the fuel injection control algorithm met the desired operating pressure conditions precisely within 2.7% in error. Moreover, the observations from the combustion pressure and rate of heat release analysis showed a similar development trend as compared to diesel combustion.