Hydrodynamics of wind-assisted ship propulsion verification and validation of RANS methodology

Wind energy as an auxiliary form of propulsion for commercial ships has again become of great interest as a possible response to volatile fuel prices and increasingly stringent environmental regulations. A well-founded performance prediction tool is a key prerequisite for the further development of this promising technology, and with the support of the European Commission and others, a group of researchers at Delft University of Technology is developing a performance prediction program for these hybrid ships. Reynolds-Averaged Navier Stokes (RANS) packages will be one of the primary tools used during the study. The advent of the numerical towing tank brings possibilities but also new challenges. The predominance of large, separated flow structures in the wake of the sailing ship, and the particular interest in the transverse force component points to a conscientious grid verification and validation study. Here, it is sufficient to achieve parity for absolute uncertainty within the larger context of the project. The ‘drift sweep’ procedure is presented with validation levels alongside computational time to demonstrate the utility of this approach in support of the derivation of empirical formulations using systemic hull form variations. Finally, a moving mesh for the rudder may be implemented in an extended drift/rudder sweep. However for this case there is no validation data presently available

Hydrodynamics of wind-assisted ship propulsion verification and validation of RANS methodology

Wind energy as an auxiliary form of propulsion for commercial ships has again become of great interest as a possible response to volatile fuel prices and increasingly stringent environmental regulations. A well-founded performance prediction tool is a key prerequisite for the further development of this promising technology, and with the support of the European Commission and others, a group of researchers at Delft University of Technology is developing a performance prediction program for these hybrid ships. Reynolds-Averaged Navier Stokes (RANS) packages will be one of the primary tools used during the study. The advent of the numerical towing tank brings possibilities but also new challenges. The predominance of large, separated flow structures in the wake of the sailing ship, and the particular interest in the transverse force component points to a conscientious grid verification and validation study. Here, it is sufficient to achieve parity for absolute uncertainty within the larger context of the project. The ‘drift sweep’ procedure is presented with validation levels alongside computational time to demonstrate the utility of this approach in support of the derivation of empirical formulations using systemic hull form variations. Finally, a moving mesh for the rudder may be implemented in an extended drift/rudder sweep. However for this case there is no validation data presently available.Ship Hydromechanics and Structure

Hydrodynamics of wind-assisted ship propulsion validation of RANS-CFD methodology

A Reynolds-Averaged Navier Stokes computational fluid dynamics (RANS-CFD) package will be one of the primary tools used during the development of a performance prediction program for Wind-Assisted commercial ships. The modelling challenge presented by large separated flow structures in the wake of the sailing ship points to a conscientious validation study. A validation data set, consisting of hydrodynamic forces acting on the ship sailing with a leeway angle, was collected at the Delft University of Technology towing tank facility, for bare-hull and appended cases. Four hull geometries were selected to represent of the Delft Wind-Assist Systematic Series. Appended cases were designed to represent a broad range of appendage topologies: Rudder, Bilge-keels, Skeg, and Barkeel. The direct validation exercise for the bare-hull case was successful, with the validation level for the sideforce equal to 9.5% (fine mesh: 9M cells). An extended validation statement is made for simulations for the entire series. This exercise was successful for leeway angles equal to 훽훽=[3표표,6표표]. The validation level (base mesh, 3M cells) for each force component is:푢푢푋푋′=12%, 푢푢푌푌′=17%, 푢푢푁푁′=10%. The validation for appended geometries was not regarded as successful, with the exception of the Rudder case. The numerical uncertainty is the dominant contribution for the validation level, motivating a proportionate refinement of the grid. Here, it is sufficient to achieve parity with other contributions to the uncertainty within the larger context of the project.Ship Hydromechanics and Structure

Wind-assist ship propulsion

Development of a Performance Prediction Program for Commercial Ship

Low-aspect ratio appendages for wind-assisted ships

Wind propulsion for commercial ships has been identified as a key component in the energy transition for the maritime industry. The sailing hybrid ship will operate with leeway (drift) angles to produce a lateral force known as sideforce, for steady operation under sail. In this paper, experimental results for the sailing performance of ships fitted with bilge keel appendages are presented. Systematic variations in appendage height, length, and position were tested, including several special cases (multiple bilge keels). The appendage typology is shown to mitigate the strong ‘destabilizing’ yaw moment that is characteristic of wind-assisted commercial vessels and to promote the non-linear sideforce component. The working principal for bilge keels—promotion of flow separation—can be employed to specify the separation location for components of the vessel vortex wake to improve the sailing performance of the ship.Ship Hydromechanics and Structure

Wind-assist ship propulsion

Development of a Performance Prediction Program for Commercial ShipsShip Hydromechanics and Structure

Protective Effects of Paricalcitol on Peritoneal Remodeling during Peritoneal Dialysis

Peritoneal dialysis (PD) is associated with structural and functional alterations of the peritoneal membrane, consisting of fibrosis, angiogenesis, and loss of ultrafiltration capacity. Vitamin D receptor activation (VDRA) plays an important role in mineral metabolism and inflammation, but also antiangiogenic and antifibrotic properties have been reported. Therefore, the effects of active vitamin D treatment on peritoneal function and remodeling were investigated. Rats were either kept naïve to PDF exposure or daily exposed to 10 mL PDF and were treated for five or seven weeks with oral paricalcitol or vehicle control. Non-PDF-exposed rats showed no peritoneal changes upon paricalcitol treatment. Paricalcitol reduced endogenous calcitriol but did not affect mineral homeostasis. However, upon PDF exposure, loss of ultrafiltration capacity ensued which was fully rescued by paricalcitol treatment. Furthermore, PD-induced ECM thickening was significantly reduced and omental PD-induced angiogenesis was less pronounced upon paricalcitol treatment. No effect of paricalcitol treatment on total amount of peritoneal cells, peritoneal leukocyte composition, and epithelial to mesenchymal transition (EMT) was observed. Our data indicates that oral VDRA reduces tissue remodeling during chronic experimental PD and prevents loss of ultrafiltration capacity. Therefore, VDRA is potentially relevant in the prevention of treatment technique failure in PD patients