Propeller design optimization for tunnel bow thrusters in the bollard pull condition

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 50-51).Tunnel bow thrusters are often used by large ships to provide low-speed lateral maneuverability when docking. Required to provide high thrust while essentially at a standstill, the design point for these thrusters is the bollard pull condition. Traditionally, the term bollard pull refers to the amount of force a tug can apply to a bollard when secured to a pier. Here, the bollard pull condition is used to describe a propeller with no flow over it except for that induced by its own rotation. Conventional propeller design is primarily performed for an optimal vessel speed or range of speeds. OpenProp, a propeller design code based on lifting line theory, is a numerical model capable of design and analysis of such propellers. It has been experimentally validated for standard design conditions in an external flow, but until now has been incapable of design with no external fluid velocity component applied. Recent updates to the model now allow for bollard pull design work. This project is the first application of the OpenProp model update. Propellers are designed for both open water and ducted (tunnel) applications in OpenProp. Propeller geometry design refinement by coupling MTFLOW, an Euler Equation viscous flow solver, with PBD-14, a lifting surface design program for marine propulsors is examined. An experimental apparatus is constructed to test the propeller designs and validate the OpenProp model. A range of off-design operating conditions are analyzed and results are presented.by James R. Wilkins, IV.Nav.E.and S.M

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion