Search

The aim of this research is to create new dimensionless relations in rigid wedge impact problems, which provides the possibility of calculating wedge kinematic parameters with acceptable accuracy. To accomplish this, the rigid wedge impact problem is simulated and validated using the Dynamic Fluid Body Interaction (DFBI) model in STAR-CCM+. In this study, new non-dimensional relations for the kinematical parameters of the wedge are derived utilising the Buckingham π theorem and data-driven analysis. It is observed that the use of appropriate dimensionless relations in any type of symmetric water impact problems involving a wedge shaped object will result in a unique diagram of each wedge kinematical parameter. This ultimately leads to the creation of two separate formulas to determine the maximum wedge acceleration value and its corresponding time. These formulas play a vital role in the design of high-speed crafts, and planing vessels. [ABSTRACT FROM AUTHOR]

ObjectivesThis paper aims to study the kinetic and dynamic characteristics of an trans-media unmanned vehicle during vertical take-off from water.MethodsIts dynamic performance during the trans-media process from water to air is numerically simulated on the basis of the viscous computational fluid dynamics (CFD) approach combined with the overset grid technique, multiple degrees of freedom and dynamic fluid body interaction (DFBI) motion model.ResultsThe results show that in order to pull the vehicle up, the air propeller rotation speed should be higher than the speed at the same pull force provided by a single propeller. As the main movement of the vehicle is vertically upward, the coupling of the air propeller downwash flow velocity and the fuselage of the vehicle leads to the "quick bowing" phenomenon.ConclusionsTo ensure smooth take-off, a manual or automatic control program should be added to adjust the tilt angle of the thrusters in real time during the take-off process. This study provides a powerful evaluation method for the optimal design and control of trans-media unmanned vehicle in the future.

[Objectives] In order to study the unsteady hydrodynamic performance of turbines under changing current conditions,[Method] this paper uses the Dynamic Fluid Body Interaction(DFBI) method based on an overset grid to simulate the unsteady hydrodynamic performance of turbines under different flow conditions. [Results] The results show that the DFBI method based on an overset grid can realize the monitoring of such transient parameters as speed, torque and flow field in the three stages of starting, acceleration and stabilization of the turbine during start-up. The power coefficient of the turbine has a peak value near the design flow rate of 1.2 m/s. Under dynamic conditions, the average energy efficiency of the turbine is about 0.181, which is about 33% lower than the designed flow rate of 1.2 m/s. [Conclusions] The numerical simulation method used in this paper can monitor the hydrodynamic performance of passively rotating turbines under real current conditions, and changes in the characteristic parameters of the turbine flow field and power output under passive rotation conditions, which can play an important role in guiding actual engineering design.