Adaptive obstacle climbing and hydrodynamic performance analyses of the amphibious robot with wheels and flexible undulating fins

In this paper, an amphibious robot with flexible undulating fins and self-adaptive climbing wheels are proposed for satisfying the needs of industrial applications. The structure of the climbing mechanism and undulating fin are firstly designed. Then, the adaptive obstacle climbing and the hydrodynamic characteristics are investigated through numerical simulations by using the Adams and Fluent, respectively. Finally, the experimental measurements of the land walking and underwater propulsion are studied. The numerical results illustrate that the amphibious robot could climb the vertical obstacle adaptively. In the underwater marching pattern, the underwater velocity could reach 1 m/s. In the rotating and yawing patterns, the angular velocity increases to the certain value while the rotating angle keeps increasing. The robot moves forward and turns around with the difference frequency of the undulating fins. The underwater propulsion and land-walking experiments show good swimming performance and the obstacle crossing ability of the amphibious robot, respectively, which verify the numerical simulation.

Experimental device design justification for radiation resistance tests of single-mode optical fibers and FBG-based sensors at the IVG.1M reactor

One of the most important stages in the development of an experimental device is to carry out a series of computational studies to substantiate the compliance of device design with the objectives of the experiment, such as the choice of test modes and the study of standard and hypothetical emergency modes of its operation. Result of these studies is the neutron-physical, thermal, strength and hydrodynamic characteristics of the structural elements of the device and working bodies. During this work, a series of neutron calculations was conducted using the MCNP6 code and thermal-physical calculations using the ANSYS software package of two configurations of the experimental device. A feature of the calculated studies is the presence of specific requirements for the thermal state of the experimental device sleeve. Namely, ensuring a predetermined temperature gradient between its ribs, which should not exceed 4°K during the reactor tests.

Numerical Investigation on Air Film Fusion of Pressure-Equalizing Exhaust around Shoulder Ventilation of Submarine-Launched Vehicle

In order to study the influence of pressure-equalizing exhaust at the shoulder of a submarine-launched vehicle on the surface hydrodynamic characteristics, this paper establishes a numerical calculation method based on the VOF multiphase flow model, the standard RNG turbulence model and the overset mesh technology; the method compares the fusion characteristics of the air film at the shoulder of the underwater vehicle, as well as the distribution of surface pressure along the vehicle’s axial direction. The results show that the approximate isobaric zone derived from air film fusion can greatly improve the hydrodynamic characteristics of the vehicle, and the number of venting holes determines the circumferential fusion time of the air film. The greater the number of venting holes, the sooner circumferential fusion starts.

Investigation of Floating Transportation Equipment for the Offshore Wind Power

This paper presents a floating transportation equipment (FTE) for the negative pressure suction bucket foundation (NPSBF) of offshore wind turbines, and the basic design and main transportation means are introduced. The hydrodynamic characteristics of integrated FTE-NPSBF structure are comprehensively studied. The ability of FTE as a transportation aid to provide stability for the NPSBF is verified, and the vibration reduction measures under the condition of wave resonance during the floating transportation process are given.

Evaluation of hydrodynamic behavior of biosand filters using computational fluid dynamics combined with the design of experiments

Biosand filters (BSFs) are widely used in rural and urban areas where access to drinking water is limited or non-existent. This study applies computational fluid dynamics in the assessment of hydrodynamic characteristics considering changes in the design of two BSF models to make construction options available to communities, without losing hydrodynamic efficiency. The commercial code ANSYS-CFX 20.1 together with a central composite design of experiments methodology to simulate the flow was used under different combinations of porosities, permeabilities, pipe diameters, and filter diameters and heights. These parameters were combined statistically from Statistica 13.3. Our results have shown that combining greater filter depths with smaller pipe diameters has played a key role in the BSF best performance, and the CAWST V10 model has performed better than HydrAid, with lower velocities and longer hydraulic retention times.

Influence of non-uniform inflow on unsteady internal flow characteristics of waterjet pump

Waterjet propulsion has many advantages when operating at high-speed conditions. As a special way of navigation, it is mostly used in high-speed ships and shallow draft ships. In this paper, a mixed-flow waterjet pump was taken as the research object. For the two cases of non-uniform inflow and uniform inflow, a modified RANS/LES method was adopted for unsteady calculation of the whole channel, aiming at investigating the influence mechanism of the non-uniform inflow on the energy performance and pressure pulsation characteristics of the waterjet pump. The hydrodynamic characteristics of the waterjet pump were comprehensively analyzed such as head, efficiency, axial-force, internal flow and pressure pulsation. It is found that the non-uniform inflow will reduce the external characteristics of the waterjet pump and lead to the huge fluctuation of energy performance with time. Low-speed swirls occur locally in the intake duct for non-uniform inflow, in which condition the vorticity is much higher than that for uniform inflow. In terms of the low-speed area, [Formula: see text] and [Formula: see text], the values under non-uniform inflow condition are generally larger than those under uniform flow condition when in the impeller and guide vane zone. The dominant frequencies of pressure pulsation are, respectively, [Formula: see text], 7[Formula: see text] and 4[Formula: see text] in the intake duct, impeller and diffuser, which are almost consitent for the two cases. However, the frequency features are more diverse, and the amplitudes corresponding to the same frequencies are more intense for non-uniform inflow.