A.F. Molland

Measurements and predictions of forces, pressures and cavitation on 2-D sections suitable for marine current turbines:

An investigation has been carried out into the lift, drag and cavitation characteristics of two-dimensional foil sections, which may typically be used as a starting point in the design of blade sections for marine current turbines. Cavitation tunnel experiments and numerical predictions using a panel code were carried out on four representative sections derived from the NACA series 4415, 6615, 63—215 and 63—815. The experimental lift and drag results show reasonable correlation with published wind tunnel data. The sections were modelled numerically using the two-dimensional panel code XFoil. The numerical cavitation predictions in most cases showed satisfactory agreement with the experiments and it is considered that such predictions could be used with reasonable confidence for predicting cavitation at the preliminary design stage. Overall, the results of the investigation provide detailed information that should assist in the design and operation of marine current turbines.

Quantifying the Airflow Distortion over Merchant Ships. Part II: Application of the Model Results

Wind speed measurements obtained from ship-mounted anemometers are biased by the presence of the ship, which distorts the airflow to the anemometer. Previous studies have simulated the flow over detailed models of individual research ships in order to quantify the effect of flow distortion at well-exposed anemometers, usually sited on a mast in the ship’s bows. In contrast, little work has been undertaken to examine the effects of flow distortion at anemometers sited on other merchant ships participating in the voluntary observing ship (VOS) project. Anemometers are usually sited on a mast above the bridge of VOS where the effects of flow distortion may be severe. The several thousand VOS vary a great deal in shape and size and it would be impractical to study each individual ship. This study examines the airflow above the bridge of a typical, or generic, tanker/bulk carrier/general cargo ship using computational fluid dynamics models. The results show that the airflow separates at the upwind leading edge of the bridge and a region of severely decelerated flow exists close to the bridge top with a region of accelerated flow above. Large velocity gradients occur between the two regions. The wind speed bias is highly dependent upon the anemometer location and varies from accelerations of 10% or more to decelerations of 100%. The wind speed bias at particular locations also varies with the relative wind direction, that is, the angle of the ship to the wind. Wind speed biases for various anemometer positions are given for bow-on and beam-on flows.

Quantifying the Airflow Distortion over Merchant Ships. Part I: Validation of a CFD Model

The effects of flow distortion created by the ship’s hull and superstructure bias wind speed measurements made from anemometers located on ships. Flow distortion must be taken into account if accurate air–sea flux measurements are to be achieved. Little work has been undertaken to examine the wind speed bias due to flow distortion in wind speed reports from voluntary observing ships (VOS). In this first part of a two-part paper the accuracy of the computational fluid dynamics (CFD) code VECTIS in simulating the airflow over VOS is investigated. Simulations of the airflow over a representation of the bridge of a VOS are compared to in situ wind speed measurements made from six anemometers located above the bridge of the RRS Charles Darwin. The ship’s structure was ideal for reproducing the flow over VOS when the wind is blowing onto either beam. The comparisons showed VECTIS was accurate to within 4% in predicting the wind speed over ships, except in extreme cases such as wake regions or the region close to the bridge top where the flow may be stagnant or reverse direction. The study showed that there was little change in the numerically predicted flow pattern above the bridge with change in Reynolds number between 2 10 5 and 1 10 7 . The findings showed that the CFD code VECTIS can reliably be used to determine the mean flow above typical VOS.

Experimental and numerical investigations into the drag characteristics of a pair of ellipsoids in close proximity

Investigations into the drag of ellipsoids in proximity have been carried out experimentally using a low-speed wind tunnel and numerically using a commercial computational fluid dynamics (CFD) code (CFXTM). The purpose of the investigations was to improve the understanding of the viscous resistance and viscous interaction effects between twin bodies in proximity, such as the hulls of a catamaran, and consequently to improve the techniques for estimating the resistance and powering of commercial catamarans. The wind tunnel tests were carried out on a single ellipsoid with a length-diameter ratio (L/D) of 6.0 and a pair of similar ellipsoids in proximity at separation-length ratios (S/L) of 0.27, 0.37, 0.47 and 0.57 at Reynolds number values up to 3.2 ×106. The ellipsoids thus represented a reflex (or reflected) model of a catamaran hull. In the numerical work, investigations were carried out on ellipsoids with the same geometry as those tested in the wind tunnel and ellipsoids with a larger length-diameter ratio. Results of the wind tunnel tests and numerical investigations are presented and compared. It is found from the investigations that viscous form effects and viscous interactions are present for such bodies and that CFD techniques can make very useful contributions to the investigations of these effects.

The design and construction of model ship propeller blades in hybrid composite materials

Abstract A description is given of the design and construction in hybrid composite materials of a model ship propeller for use in wind tunnel tests. The reasons for the choice of a glass/carbon reinforced composite material for the blade manufacture are discussed. Results are presented for tests carried out on hybrid composite samples prepared by wet-lay-up by hand under practical manufacturing conditions. The design stress levels used in the final design were based on the test results for the samples. A description is given of the blade design and the production method. Successful operation of the propeller has confirmed the suitable application of the chosen material for the blades.

Ship Resistance and Propulsion: Components of Hull Resistance

Physical Components of Main Hull Resistance An understanding of the components of ship resistance and their behaviour is important as they are used in scaling the resistance of one ship to that of another size or, more commonly, scaling resistance from tests at model size to full size. Such resistance estimates are subsequently used in estimating the required propulsive power. Observation of a ship moving through water indicates two features of the flow, Figure 3.1, namely that there is a wave pattern moving with the hull and there is a region of turbulent flow building up along the length of the hull and extending as a wake behind the hull. Both of these features of the flow absorb energy from the hull and, hence, constitute a resistance force on the hull. This resistance force is transmitted to the hull as a distribution of pressure and shear forces over the hull; the shear stress arises because of the viscous property of the water.

Ship Resistance and Propulsion: Numerical Estimation of Ship Resistance

Introduction The appeal of a numerical method for estimating ship hull resistance is in the ability to seek the ‘best’ solution from many variations in shape. Such a hull design optimisation process has the potential to find better solutions more rapidly than a conventional design cycle using scale models and associated towing tank tests. Historically, the capability of the numerical methods has expanded as computers have become more powerful and faster. At present, there still appears to be no diminution in the rate of increase in computational power and, as a result, numerical methods will play an ever increasing role. It is worth noting that the correct application of such techniques has many similarities to that of high-quality experimentation. Great care has to be taken to ensure that the correct values are determined and that there is a clear understanding of the level of uncertainty associated with the results.

Ship Resistance and Propulsion: Wake and Thrust Deduction

Introduction An interaction occurs between the hull and the propulsion device which affects the propulsive efficiency and influences the design of the propulsion device. The components of this interaction are wake, thrust deduction and relative rotative efficiency. Direct detailed measurements of wake velocity at the position of the propeller plane can be carried out in the absence of the propeller. These provide a detailed knowledge of the wake field for detailed aspects of propeller design such as radial pitch variation to suit a particular wake, termed wake adaption, or prediction of the variation in load for propeller strength and/or vibration purposes. Average wake values can be obtained indirectly by means of model open water and self-propulsion tests. In this case, an integrated average value over the propeller disc is obtained, known as the effective wake. It is normally this average effective wake, derived from self-propulsion tests or data from earlier tests, which is used for basic propeller design purposes.

Ship Resistance and Propulsion: Figure Acknowledgements

Dominic A Hudson Pdf Ship Resistance And Propulsion Miguel Santos. 9780521760522 Ship Resistance And Propulsion Practical. Chapter 7 Resistance And Powering Of Ships. Ship Resistance And Propulsion By Anthony F Molland. Prediction Of Resistance And Propulsion Power Of Ships. Resistance Amp Propulsion Archives Thenavalarch. Ship Resistance And Propulsion Evebook S Blog. Ship Resistance And Propulsion Practical Estimation Of. Talk Ship Resistance And Propulsion. Ship Resistance And Propulsion Amarine. Ship Resistance Propulsion And Hull Design Sintef. The Hamburg Ship Model Basin Hsva. Ship Resistance And Propulsion Anthony F Molland. Ship Resistance And Propulsion Practical Estimation Of. Naval Architecture Resistance And Propulsion Britannica. Ship Resistance And

Ship Resistance and Propulsion: Index

Dominic A Hudson Pdf Ship Resistance And Propulsion Miguel Santos. 9780521760522 Ship Resistance And Propulsion Practical. Chapter 7 Resistance And Powering Of Ships. Ship Resistance And Propulsion By Anthony F Molland. Prediction Of Resistance And Propulsion Power Of Ships. Resistance Amp Propulsion Archives Thenavalarch. Ship Resistance And Propulsion Evebook S Blog. Ship Resistance And Propulsion Practical Estimation Of. Talk Ship Resistance And Propulsion. Ship Resistance And Propulsion Amarine. Ship Resistance Propulsion And Hull Design Sintef. The Hamburg Ship Model Basin Hsva. Ship Resistance And Propulsion Anthony F Molland. Ship Resistance And Propulsion Practical Estimation Of. Naval Architecture Resistance And Propulsion Britannica. Ship Resistance And