A study on the hydrodynamic performance of manta ray biomimetic glider under unconstrained six-DOF motion

A manta ray biomimetic glider is designed and studied with both laboratory experiments and numerical simulations with a new dynamic update method called the motion-based zonal mesh update method (MBZMU method) to reveal its hydrodynamic performance. Regarding the experimental study, an ejection gliding experiment is conducted for qualitative verification, and a hydrostatic free-fall experiment is conducted to quantitatively verify the reliability of the corresponding numerical simulation. Regarding the numerical simulation, to reduce the trend of nose-up movement and to obtain a long lasting and stable gliding motion, a series of cases with the center of mass offset forward by different distances and different initial angles of attack have been calculated. The results show that the glider will show the optimal gliding performance when the center of mass is 20mm in front of the center of geometry and the initial attack angle range lies between A0 = -5° to A0 = -2.5° at the same time. The optimal gliding distance can reach six times its body length under these circumstances. Furthermore, the stability of the glider is explained from the perspective of Blended-Wing-Body (BWB) configuration.

Time-Domain Flooding Simulation of a Damaged Warship

Understanding of the complex dynamic behavior of damaged ships and floodwater remains limited for ship designers and safety authorities. In this work, a Navier-Stokes (NS) solver that combines the volume of fluid (VOF) method with overset mesh techniques is developed to simulate the flooding process of a damaged ship. The VOF method captures the fluid interface, and the turbulence effect on flows is considered with the k-ω model. The overset mesh techniques are employed to handle the mesh update following transient ship motions. Then, the results of a damaged barge with dynamic and overset mesh are compared with the experimental data. On the basis of this validation, the solver is applied to the flooding problems of a damaged warship. This research is intended to be a useful step toward the establishment of a stability criterion for damaged ships in the future.

Fit Evaluation during Repetition Interaction in Garment Pattern Design

We present a novel virtual try-on solution for fitting evaluation and pattern modification to design various types of garment and speed up the garment design process. In the phase of fit evaluation, we propose a method for producing two-dimensional (2D) color maps by comparing a 2D triangle mesh panel garment and a 3D triangle mesh garment, which can display the fit evaluation outcome in real time. In the phase of pattern modification, a novel prior condition based on maximum entropy coordinates and a more comprehensive mean value coordinates interpolation algorithm are proposed. By a combination of the two deformation methods, the positions of the internal vertices are updated smoothly. Applying the proposed method to the repetition of the garment design procedure, the experimental results show that it can easily pinpoint the location where it needs to be modified and can achieve arbitrary pattern modification with a smooth mesh update.

Analysis of Concentric Canister Wall Roughness Effect on Jet Flow Based on Fluid Dynamics

Adopting concentric canister launchers (CCL), high temperature and high pressure environment of CCL is unfavorable for the missile launch. In addition to the gap between internal canister and external canister, injecting water for cooling are the main factor of impact the canister flow field, CCL’s rough wall is also a very important influence factor. In this paper, under the two working conditions of rough wall and smooth wall, use dynamic layering manner of moving mesh update method to simulate concentric canister missile launch process. The results reveal that rough wall has a great influence for pressure of concentric canister internal flow field, but the least influence for temperature. In practical engineering applications, need smooth surface material for smooth flow field exhaust when manufacturing concentric cylinder, but the non-concentric canister manufacturing of missile cold-launch canister, retain the rough wall can increase the pressure of the missile launch, this is conducive to missile launch, and also saves manufacturing costs, reduces processing procedures.