This paper describes the design process of a high speed mono hull RoPax ferry which operates at a Froude number of 0.4. The design task was quite challenging, as two possible transport concepts were in principle possible: Two ships were needed with a total speed of 50knots, which could result in a combination of a 30kn high speed Catamaran plus a conventional 20kn RoPax Ferry or alternatively in two identical sister vessels of 25kn each. The solution with the high speed catamaran plus the conventional RoPax-Ferry defined the total cost budget, which must not be exceeded by the design of the two sister vessels. This resulted in a tough boundary condition and made life cycle cost evaluations necessary. Due to harbor restrictions, the length of the ships was limited by abt. 110m, resulting in a Froude number of abt. 0.4. This resulted in high costs for the propulsion system. The ferries should initially have open RoRo-Cargo spaces for cost reasons, which made the stability requirements (weather criterion plus Stockholm Agreement) quite challenging. This also strongly influenced the design of the final hull form. As the ship is very sensitive to weight, detailed steel structure optimizations had to be carried out to optimize the main grillage systems of the vehicle decks. The hull form and the appendage design required careful optimization to guarantee the required service speed with the engine power which was available in the price budget. As no vessel of comparison was available, the speed power estimation as well as all design tasks had fully to rely on numerical predictions. As the ship had further demanding requirements for course keeping and comfort in waves, the optimization of the hull form must include also these issues. The paper shows that the design of complex ships is actually a holistic task which includes many engineering disciplines. The paper also shows that 1st principle based design methods can support the design process of specialized vessels significantly.
<p>Close to reality computation of the serviceability, durability and load-carrying capacity of old masonry and concrete arch bridges for rising live loads is a current problem. In Germany many of such road- and railway bridges exist. Some of the most important features for applicable numerical evaluation of arch bridges are a realistic structural model, the consideration of the nonlinear load history and in particular the inclusion of realistic nonlinear material models applicable for historical masonry.</p> <p>Often input parameters necessary for a realistic simulation are unknown. Then e.g. material and geometry data must be determined by measurements. In particular at historical masonry bridges these data can show relatively strong variance. By sensitivity studies can be determined correlation between the input data variance and output value variation of the computation model. As basis of measuring program so the most important input values can be determined. Sometimes some input values can be measured only indirectly. In these cases parameter identifications can be used for the determination of the input values and for validating the computation model.</p> <p>The paper presents powerful strategies for sensitivity analysis with stochastic sampling methods and for identification problems with optimization algorithms. Several examples from a masonry arch bridge demonstrate the application of these methods. The material behaviour described by the presented practical applications with powerful three-dimensional continuum models for regular and irregular masonry types. On this basis it is possible to simulate masonry specific failure and damage mechanisms.</p>
Abstract Unconventional reservoirs produce substantial quantities of oil and gas. These reservoirs are usually characterized by ultra-low matrix permeability. Most unconventional reservoirs are hydraulically fractured in order to establish more effective flow from the reservoir and fracture networks to the wellbores. The success of hydraulic fracture stimulation in horizontal wells has the potential to dramatically change the oil and gas production landscape across the globe and the impacts will endure for decades to come. For a given field development project, the economics are highly dependent completion establishing effective and retained contact with the hydrocarbon bearing rocks. Well and completion design parameters that influence the economic success of the field development include well orientation and landing zone, stage spacing and perforation cluster spacing, fluid volume, viscosity and pumping rate, and proppant volume, size and ramping schedule. Optimization of these design parameters to maximize asset economic value is key to the success of every unconventional asset. To achieve an optimal completion design for an asset, the current industry practice is to conduct a large number of field trials that require high capital investment and long cycle-time, and most importantly, significantly erode the project value. The workflow and toolkits shown in this paper offer a much cheaper and faster alternative approach in which to develop an optimal well completion design for EUR and unit development cost (UDC) improvements. It provides an integrated well placement and completion design optimization process that integrates geomechanics descriptions, formation characterizations, flow dynamics, microseismic event catalogues, hydraulic fracturing monitoring data, well completion and operational parameters in a modeling environment with optimization capability. The model is built upon a 3D geological model with multi-disciplinary inputs including formation properties, in-situ stresses, natural fracture descriptions, and well and completion parameters (i.e., well orientation, landing interval, fluid rate and volume, perforation spacing, and stage spacing). Upon calibrating with the hydraulic fracturing diagnosis data, the model provides optimized well completion design, and guidance on data acquisition and diagnostic needs to achieve EUR performance at optimized costs. Field trials based on recommendations from the approach have yielded encouraging production uplift and have led to a significant reduction in the number of trials and cost compared to the commonly used trial-and-error approach. We believe it is technically feasible to derive an optimal completion design using a subsurface based forward modeling approach which will deliver significant value to the industry.
Potential flow solvers have been and still are the work horses of computational wave resistance determination. Having matured over more then two decades they seem to have reached their limit of improvement. While the main focus of today’s software development lies on viscous flow solvers, the development of potential codes must not be disregarded, but they should instead be keep up to date with respect to the requirements of today’s and future ship building markets as well as hardware and software capabilities.
The reliable and correct determination of the wave resistance is the key to an efficient ship design, as the wave resistance is one on the major factors concerning building and operational costs. In this paper the authors present a new approach to transverse wave cut analysis to overcome the major shortcoming of the resistance prediction from potential flow: a numerically stable and physically sound estimate for the magnitude of the wave making resistance.
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