Hydrodynamic testing of wind-assisted cargo ships using a cyber-physical empirical method

A novel empirical method to study wind-assisted cargo ships is presented. The physical ship model, including propulsion units, interacts in real-time with a numerical sail model during free-running tests. Loads from the (virtual) sails are applied on the physical model using a cable-driven robot. All loads components except heave are applied with high accuracy and repeatability. The method is described thoroughly, and applied to investigate the benefits of wind assistance on a 190m bulk-carrier, equipped with four rotor sails. Key performance indicators for wind assistance are established when sailing in steady wind profiles of various directions and velocities, and a propulsion analysis is performed. An important conclusion is that the increase of hydrodynamic resistance due to heel, leeway and rudder (that balance transverse sail loads) is rather limited for this ship, except when sailing close-hauled in strong winds. It is also demonstrated that experiments in a unsteady (virtual) wind environment can be successfully conducted. The effect of turbulence on the motions of this ship are found to be very limited. The conclusion discusses the other types of studies that can be enabled by this novel cyber-physical empirical method.

Impact of aortic annulus geometry according to ISO 5840:2019 (draft) on hydrodynamic performance of transcatheter aortic valve prostheses

To assess the hydrodynamic performance of transcatheter aortic valve prostheses (TAVP), in vitro test using pulse duplicators is required. Test conditions as well as minimum performance criteria are specified in ISO 5840- 3:2013 and ISO 5840-3:2019-draft. In the 2019 published draft, modifications regarding hydrodynamic testing are proposed. Among others, the geometrical configuration of the fixation has changed, with the intention to improve the anatomical representation as well as the comparability of results from different test laboratories. We analyzed the consequences of altered annulus fixations regarding native leaflets as well as a step in the proximal area of the protheses to prevent their migration. The analyses were conducted with regard to the degree of calcification of the annulus ring on hydrodynamic parameters. By using 3D stereolithography printing technology, molds for casting of silicone elastomer of annulus models with and without native leaflets were manufactured. A modular system enabled us to use the same annulus ring to model the degree of calcification as well as different step sizes. We performed in vitro hydrodynamic testing according to ISO 5840-3:2019-draft of a selfexpandable valve prototype with porcine pericardial leaflets by using a commercially available pulse duplicator system. As expected, regurgitation increases with increasing degree of calcification, whereby the use of a step has no influence on the backflow of fluid during diastole. The effective orifice area (EOA) of the valve showed a clear tendency with respect to radial protrusion of the step. The EOA decreased as the radial protrusion increased. We also present a suggestion to prevent migration without affecting the general test results, by using a novel step design. We also found that the novel annulus model with native leaflet drastically reduced the regurgitation.

Study of the possibilities of 3D printing in ship modeling using the example of manufacturing a model of a small vessel for hydrodynamic testing in an experimental pool

The relevance of the work is determined by a fundamentally new direction of 3D printing in the manufacture of ship models for hydrodynamic testing. In this paper, we study the towing drag of a model of a small boat manufactured using additive three-dimensional printing technologies. Based on the dimensions of the 3D printers used and the technological parameters of working with them, as well as the design features of the test pool, small-sized vessels of a series of kayaks, kayaks and canoes, which are of sufficient length, but not too wide and high, were investigated as a prototype of the future model, which is ideal under the methods of additive manufacturing. A base of prototypes of vessels of this class has been compiled and a rationale has been given for the choice of the prototype vessel itself for research, including an analysis of the design of the vessels presented, the availability of design and technological documentation, as well as technological schemes for manufacturing the model. A 3D model of the vessel was developed, its optimization for 3D printing and analysis of geometric shapes for deviations from ITTC requirements. The study of deviations of the geometric shapes of the ship model from shrinkage deformations was carried out using 3D scanning with the development of a technological scheme for describing this process. When developing a 3D model, in the process of 3D printing, as well as processing the results of 3D scanning, modern software tools — FreeShip, Autodesk Inventor, Cloud Compare, and others — were used in the work. In the manufacture of the model, the new DPA adhesive compound formula was used, able to provide durable joints for PLA plastic products. It was found that the measurements prove the possibility of using 3D printing for the production of ship models for hydrodynamic testing, subject to all the nuances of the technology.