Self-Propulsion

The good seakeeping characteristics of SWATH hull form are very interesting for small working craft and pleasure boats. Intrinsic limitations as the low values of weight per inch of immersion and transversal and longitudinal instability, can be acceptable and successfully managed when the mission profile does not ask for significant load variation and shift. The exploitation of SWATH concept is limited by the craft size, but if main dimensions allow enough static stability, this configuration appears very promising. SWATH behaviour in rough sea at zero and low speed have led to consider this hull form within the small craft design research program in progress at University of Naples Federico II.
The design of small size SWATH working/pleasure craft has to begin from the consideration of strut waterplane areas that are the key factor to get acceptable static and dynamic stability. Displacement has to be reduced as most as possible to increase static stability, as shown by last design trends. The results of CFD analysis concerning SWATH resistance and propulsion, aspects are presented. A numerical evaluation of the hull-propeller interactions is performed, through simulations of self-propulsion tests with a simplified method (Actuator Disk model) to discretize the propeller effect. The effective wake coefficient, the thrust deduction fraction and hull efficiency are provided. To validate CFD resistance results a comparison with experimental tests performed by Authors is reported.
The presented work highlights different hydrodynamic aspects, comments advantages and critical issues of SWATH concept and reports detailed CFD modelling procedure with the aim to provide a reference for SWATH small craft design.

A series of self-propulsion tests of a catamaran design at medium-speeds is proposed to study the influence of the hydrodynamics at medium-speeds on the waterjet propulsors. These model tests will be carried out using a load-varied self-propulsion testing technique in calm water. Due to size requirements of the model, a single demihull is to be utilised in close proximity to the side wall of the towing tank which acts as the plane of symmetry, reflecting waves generated by the demihull and therefore providing the acceptable blockage effects and wave interference for the second demihull. NOMENCLATURE C r Residual resistant coefficient F rl Froude length number F rh Froude depth number Mass flow rate p s Total pressure at station s T G Gross thrust u s Jet velocity at station s

A series of self-propulsion tests of a catamaran design at medium-speeds is proposed to study the influence of the hydrodynamics at medium-speeds on the waterjet propulsors. These model tests will be carried out using a load-varied self-propulsion testing technique in calm water. Due to size requirements of the model, a single demihull is to be utilised in close proximity to the side wall of the towing tank which acts as the plane of symmetry, reflecting waves generated by the demihull and therefore providing the acceptable blockage effects and wave interference for the second demihull. NOMENCLATURE C r Residual resistant coefficient F rl Froude length number F rh Froude depth number Mass flow rate p s Total pressure at station s T G Gross thrust u s Jet velocity at station s

Any Physics theory is stated via the basic communication system which, by the aid of a theorem can be proved as contradictory. Therefore at best, a “least contradictory” Physics can be stated based on a claim for minimum contradic-tions which together with the theorem mentioned, constitute the core of this work. This Physics can be regarded as consequence of principles of thought; it is compatible, under certain simplifications, with Newtonian mechanics, rela-tivity theory and QM.  Finally this Physics is a Space-Time Quantum Mechanics which describes Minimum Contradictions Everything. On this basis, new explanations for various questions of physics can be given as the gravitation, the second thermodynamic law, the fractal behavior of matter systems and the interaction of the electromagnetic with the gravitational field.  According to the spirit of this work, stochastic-quantum space-time is matter itself and any matter system behaves as if it had an ability to decide for its evolution.  Thus, the basic property of “Everything” is volition whose however basic dimension is logic; this is the reason why things even though acting under their volition they appear to have a considerable logical behavior. According to this point of view, biological organizations have the ability to decide for their evolution which is another approach to species evolution in general.
This work originates from various articles, which have been presented at various conferences or published in various journals from 1994 until now. It is derived from purely mental principles in contrast to theories which condense the experience which has been revealed. Thus, in a logically linked way, under certain simplifications, Newton’s gravitation law derives from mental princi-ples and not from empirical observations as the falling apple is.

A series of self-propulsion tests of a catamaran design at medium-speeds is proposed to study the influence of the hydrodynamics at medium-speeds on the waterjet propulsors. These model tests will be carried out using a load-varied self-propulsion testing technique in calm water. Due to size requirements of the model, a single demihull is to be utilised in close proximity to the side wall of the towing tank which acts as the plane of symmetry, reflecting waves generated by the demihull and therefore providing the acceptable blockage effects and wave interference for the second demihull. NOMENCLATURE C r Residual resistant coefficient F rl Froude length number F rh Froude depth number Mass flow rate p s Total pressure at station s T G Gross thrust u s Jet velocity at station s