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The velocity fields, streamlines and pressure distribution with torpedo velocity U = 1 m/s and angle of attack θ = −10 • .
Source publication
In this study, numerical computation is used to investigate the hydrodynamic characteristics of a torpedo-shaped underwater glider. The physical model of a torpedo-shaped underwater glider is developed by Myring profile equations and analyzed by the computational fluid dynamics approach. The Navier–Stokes equations and the energy equation coupled w...
Citations
... Based on large eddy simulation and the Ffowcs-Williams and Hawkings equations, Qin et al. [32] performed hydrodynamic analysis for a Slocum glider and a blended-wing-body glider, and concluded that blended-wing-body gliders have lower energy cost and low noise performance. Le and Hong [33] used computational fluid dynamics (CFD) methods to acquire the hydrodynamic characteristics of a torpedo-shaped underwater glider, demonstrating the practicality of CFD methods in glider design. To reflect the underwater glider motion more realistically, Wang et al. [34] proposed a fluid-multibody coupled analysis method considering the interactions between multibody dynamics and fluid dynamics, enabling a complex dynamic analysis of the underwater glider. ...
Marine monitoring equipment such as Argo profiling buoys and underwater gliders are important devices for oceanographic research and marine resource exploration. In this study, a novel mobile buoy capable of vertical profiling motion like Argo profiling buoys and sawtooth gliding motion like underwater gliders is proposed. The proposed mobile buoy can switch between the two motion modes with controllable wings. To verify the feasibility of the proposed mobile buoy, a fluid–multibody coupling model considering multibody dynamics and hydrodynamics was developed to investigate the dynamic response. A scaled-down buoy prototype was fabricated and the feasibility of the two motion modes was experimentally investigated in a laboratory tank. The experimental results agree well with the results of numerical simulation. This work can be helpful for the design and analysis of this kind of mobile buoy.
... Computer fluid dynamic (CFD) simulation is one of the most common ways to obtain hydrodynamic parameters of underwater * Corresponding author. E-mail address: hchoi@kmou.ac.kr equipment easily and quickly in the research process of underwater equipment [8][9][10][11][12]. Nguyen et al. [13] have proposed a robust adaptive control algorithm for the hybrid underwater glider (HUG). ...
This study aims to design a new hybrid twin autonomous underwater vehicle (HTAUV) consisting of dual cylinder hulls and analyze its pitching motion. The kinematic model for the HTAUV is established, followed by the execution of hydrodynamic simulation CFD of the HTAUV using Ansys Fluent. These simulations are conducted to obtain the hydrodynamic force equation of the HTAUV, which relates to the deflection angle of the elevator. Through the motion simulation of the HTAUV, under the same net buoyancy condition, notable differences emerge when the elevator is deflected. Specifically, parameters such as gliding speed, gliding angle, and pitch angle of the HTAUV are larger when the elevator is deflected, as compared to cases where no deflection is applied.
... Computational fluid dynamics (CFD) is known as an important technology for the study of the hydro-aerodynamic characteristics of fluid motion, and has been applied to a microchannel, sterilization chamber, torpedo-shaped underwater glider, centrifugal blower, an infection isolation room, etc. [7][8][9][10][11][12][13][14]. Le et al. [7][8][9][10] investigated the thermocapillary migration of the fluid flows in a microchannel. ...
... Computation 2023, 11,167 12 of 13 Figure 11 shows the pressure in the two cases of the hand-washing chamber during a 20 s period. The pressure value in the chamber with a hand is larger than that in the chamber without a hand. ...
... Computation 2023,11, 167 ...
The aim of this study is to develop a physical model and investigate the bactericidal effect of an automated hand-washing system through numerical computation, which is essential in areas affected by COVID-19 to ensure safety and limit the spread of the pandemic. The computational fluid dynamics approach is used to study the movement of the solution inside the hand-washing chamber. The finite element method with the k- model is applied to solve the incompressible Navier–Stokes equations. The numerical results provide insights into the solution’s hydrodynamic values, streamlines, and density in the two cases of with a hand and without a hand. The pressure and mean velocity of the fluid in the hand-washing chamber increases when the inlet flow rates increase. When the hand-washing chamber operates, it creates whirlpools around the hands, which remove bacteria. In addition, the liquid inlet flow affects the pressure in the hand-washing chamber. The ability to predict the hydraulic and cleaning performance efficiencies of the hand-washing chamber is crucial for evaluating its operability and improving its design in the future.
... The research also showed that the changes in hydrodynamic force and moment is nonlinear. Thanh-Long and Duc-Thong [20] also used the CFD method to investigate the hydrodynamic properties of a torpedo-shaped underwater glider. Profiling equations were used to establish the physical model of the underwater glider. ...
Torpedoes play an irreplaceable role in naval warfare; therefore, it is significant to study the dynamic response of the direct navigation of torpedoes. In order to study the dynamic response of torpedoes under different Munk moment coefficients, the dynamic equation of torpedoes is established based on the momentum theorem and the momentum moment theorem. The linear motion mathematical model of torpedoes is obtained. The relationship between the torpedo and the Munk moment coefficient is derived. The straight-line motion model of the torpedo under different Munk moments is established, and the dynamic properties of the space motion of the torpedo are analyzed. It is found that the Munk moment coefficient increase will lead to an increase in the deflection of the torpedo’s direct motion on each degree of freedom, and the Munk moment coefficient is related to the additional mass matrix. During the design of the torpedo, the added mass should be reduced by changing the shape of the torpedo as much as possible so as to reduce the pitch moment, yaw, and roll moments of the torpedo.
... The fixed wing plays a vital role in the work of the UG and the HAUV; the lift generated by the wing drives the UG and HAUV forward during the dive and surfacing states and CFD numerical calculations are used to study the hydrodynamic characteristics of torpedo-type underwater gliders. [7]. The acquisition of hydrodynamic parameters is crucial to the simulation prediction of the UG and the HAUV. ...
The twin hybrid autonomous underwater vehicle (THAUV) is a novel type of unmanned underwater platform that consists of a twin torpedo-shaped hull and is actuated by two buoyancy engines and two thrusters proposed in this paper. The THAUV was designed to have faster speed generated by the two buoyancy engines and two thrusters. The two buoyancy engines on each hull and the airfoil are mainly responsible for the diving and surfacing motion, and the thrusters drive the THAUV along the horizontal plane. The THAUV is capable of carrying more instrumentation and energy than a conventional hybrid autonomous underwater vehicle (HAUV) with a single buoyancy engine such that the THAUV can perform more exploration tasks and operate for a longer period in a one-time operation. Different from other unmanned underwater vehicles (UUVs) with two airfoils or wings, the THAUV has a single airfoil connecting the twin hull such that it does not require connecting bars and additional airfoils. For this reason, the structure of THAUV is more compact and simpler. In this paper, a new compact THAUV is designed and CFD simulation is used to obtain the hydrodynamic parameters of THAUV operation in water. The motion model of the THAUV is also established and the operating parameters of the THAUV are obtained by simulation.
... Computational fluid dynamics (CFD) simulation is a valuable technology for the understanding of hydroaerodynamics in many areas such as evaluating fluid motion and hydrodynamic characteristics (pressure and velocity) in a microchannel, sterilization chamber, or laminar airflow unit in operating rooms [8][9][10][11][12][13]. Beaussire et al. [14] performed CFD simulations based on the lattice Boltzmann method (LBM) to analyze the airflow and particles spreading from a patient's cough, and summer and winter weather effects are also considered in the study. ...
Airborne infection isolation (AII) rooms are used to accommodate patients with highly infectious diseases and keep the released pathogens to limit the risk of cross-infection. This paper proposes a concept for an AII room made from two shipping containers to handle the scarcity of hospital beds when the COVID-19 disease spreads over the world. The proposed system consists of the main isolation room, anteroom, and toilet as well as other functional areas. In addition, the main isolation room was modeled with important components such as a supply air vent, exhaust air, a patient, and a bed. The computational fluid dynamics (CFD) approach based on the finite volume method (FVM) is used to solve the three-dimensional governing equations. The CO2 concentration was used to determine the infectious contaminant concentration of the air in the room. Therefore, the infectious control could be evaluated by the air change per hour (ACH). The numerical results show that the room temperature is maintained at 24°C, which is appropriate for people in the room. The laminar airflow extends downward to the floor after leaving the supply air vent on the ceiling, creating circulating patterns throughout the room. When evaluating the effectiveness of ventilation systems to remove airborne contaminants based on different ACH numbers, the CO2 concentration in the room was reduced to 581 ppm, 477 ppm, and 438 ppm in the cases of 12 ACH, 24 ACH, and 48 ACH, respectively. As a result, the greater the number of air change per hour, the greater the performance for contaminant removal. It served as the foundation for assessing and optimizing the ventilation system of the portable negative pressure room.
This paper presents a compact design of compliant mechanism that produces single degree-of-freedom (DOF) for accurate linear motion and large stroke with low input force of below 10N from the linear actuators. Based on the stiffness matrices and relationships between beam-type flexure elements, the analytical model of the entire compliant mechanism is proposed and its mechanical property is clarified. Subsequently, the finiteelement-analysis (FEA) is conducted via ANSYS software to verify the actual performance of the compliant mechanism. The good agreement between analytical and simulation results demonstrates the correctness of the proposed design, and it can be employed as a compliant bearing for a precise linear actuator. The obtained results also suggest some ideas to enhance the performance of the designed linear-motion compliant mechanism in terms of working range, stiffness characteristic and positioning accuracy.
An accurately predicted dynamic model is essentially required to design a robust control system for an autonomous underwater vehicle (AUV) maneuvering in six degrees of freedom. The dynamic model consists of hydrodynamic derivatives which include inertial and damping coefficients. Traditionally, these coefficients can
be estimated through Analytical and Semi-Empirical (ASE) methods, Computational Fluid Dynamics (CFD), and through experiments such as captive or free model testing. Additionally, System Identification (SI) estimators, e.g. extended Kalman filter, are also employed to predict the complete set of parameters. Recently, with the advent of Artificial Intelligence (AI) in almost every field of science, supervised machine learning algorithms such as Support Vector Machine (SVM) and neural network algorithms are also being applied to predict the coefficients with lesser computational cost and higher accuracy. Additionally, AI-based parametric and nonparametric modelling of autonomous marine vehicles have also been discussed. Accordingly, the contributions of researchers and scientists, with respect to the evolution and application of these important techniques for marine vehicles, particularly torpedo-shaped AUVs, done over the past more than 75 years, have been thoroughly surveyed and sequentially consolidated in this article. At the end, based on the survey, merits and demerits of each technique over the others have been highlighted and published results have also been discussed to evaluate the effectiveness of these estimation techniques for autonomous underwater vehicles.
Purpose
This paper aims to focus on the effect of the operating condition such as the impeller speed on the centrifugal fan performance and flow characteristics. The ability to predict the behavior of the airflow motion in a centrifugal blower is essential for obtaining the topology optimization design.
Design/methodology/approach
A physical model of the air blower consisting of these main parts in a blower system: collector, impeller, outlet flange and volute casing, and the appropriate boundary conditions are set up by ANSYS software. Computation fluid dynamics are performed for the numerical analysis. The calculation of blower performance parameters such as total pressure, efficiency and flow rate is based on the Reynolds averaged Navier–Stokes equations and k - ε turbulence flow model.
Findings
The numerical results show that the change in operating conditions has a significant effect on the blower performance, and the pressure maintained inside the blower is higher for a larger impeller rotational speed.
Originality/value
This work is original and has not yet been submitted to elsewhere or published previously.
