Dynamics of marine vehicles with aerodynamic surfaces

An assessment of the relative speeds and payload capacities of airborne and waterborne vehicles highlights a gap which can be usefully filled by a new vehicle concept, utilizing both hydrodynamic and aerodynamic forces. A high speed marine vehicle equipped with aerodynamic surfaces (called an AAMV, 'Aerodynamically Alleviated Marine Vehicle') is one such concept. The development of this type of vehicle requires a mathematical framework to characterize its dynamics taking account of both aerodynamic and hydrodynamic forces. This thesis presents the development of unified and consistent equations of equilibrium and equations of motion to predict the dynamic performance of such AAMV configurations. An overview of the models of dynamics developed for Wing In Ground effect 'WIGe' vehicles and high speed marine vehicles (planing craft) is given first. Starting from these models, a generic AAMV configuration is proposed and a kinematics framework is developed. Then, taking into account the aerodynamic, hydrostatic and hydrodynamic forces acting on the AAMV, equations of equilibrium are derived and solved. This is followed by deriving and solving the full equations of motion, using a small perturbation assumption. A static stability criterion, specific for the AAMV configuration, has been developed. This mathematical framework and its results are implemented in MATLAB and validated against theoretical and experimental data. The resultant capability for analysing novel AAMV configurations is presented through two parametric analysis. The analysis demonstrate that these models offer a powerful AAMV design tool.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A Mathematical Model to Analyze the Static Stability of Hybrid (Aero- Hydrodynamically Supported) Vehicles.

Among the new concepts developed for high speed marine vehicles over the last two decades, the "aerodynamic alleviation" approach consists in using an aerodynamic surface to "alleviate" the weight sustained by the hydrodynamic lift. Such vehicle experiences aerodynamic and hydrodynamic forces of the same order of magnitude, therefore the dynamic models developed for airborne and waterborne vehicles are not suitable. Considering a vehicle having a high-speed prismatic planing hull and one or more aerodynamic surfaces, the authors propose two mathematical methods. The first one calculates the equilibrium attitude of the vehicle at a given speed and its numerical implementation has been used to undertake a parametric analysis of the influence of some configuration characteristics on performances. The second method analyzes the static stability of the HV. Starting from the dynamic analysis previously proposed by the authors, the characteristic polynomial of the HV dynamics is derived and a static stability criterion is proposed

High Speed Marine Vehicles With Aerodynamic Surfaces: Development of a Dynamic Model for a Novel Configuration.

A research programme on high speed marine vehicles fitted with aerodynamic surfaces started in Cranfield University in 2005. One of the configurations analyzed is a high speed prismatic planing hull with one or more aerodynamic surfaces; it is called a hybrid vehicle (HV). Two mathematical models have been developed for the dynamic behavior which is a combination of the very different behaviors of aircraft and ships. The first model estimates the equilibrium attitude of the HV at a certain speed. A parametric analysis for the influence of the configuration on the performance of the HV has been conducted (1). With the second model, the authors propose a set of ordinary differential equations of motion, derived in the frame of small-disturbance stability theory which has been used to investigate the longitudinal dynamic stability of the HV (2). Ref. (1) and (2) present a complete description of the mathematical models, while this article summarizes the methodology adopted to develop these dynamic models and gives a brief summary of the results. (1) COLLU, M., PATEL, M. H., TRARIEUX, F., A Mathematical Model to analyze the Static Stability of Hybrid (Aero- hydrodynamically supported) vehicles., 8th Symposium on High Speed Marine Vehicles 2008 (HSMV08), Naples, Italy, 2008. (2) COLLU, M., PATEL, M. H., TRARIEUX, F., A Unified Mathematical Model for High Speed Hybrid (Air and Water- borne) Vehicles., 2nd International Conference on Marine Research and Transportation, 2007

A Unified Mathematical Model for High Speed Hybrid (Air and Water-borne) Vehicles.

During the last two decades, the interest in civil and military high speed marine vehicles has lead to several new configurations. Some of them exploit a combination of aerodynamic and hydrodynamic forces to sustain part of the weight of the craft, leading to a hybrid vehicle (HV). This paper focuses on the study of the longitudinal high-speed dynamics of such hybrid vehicles. Since airborne and waterborne vehicles belong to two distinct areas of research, they have been investigated with a rather different approach. The authors propose a unified mathematical model to represent the kinematics suitable for hybrid vehicles, including a detailed analysis of the aerodynamic and hydrodynamic forces acting on the vehicle. Then a set of ordinary differential equations of motion is derived in the frame of small-disturbance stability theory, leading to the Cauchy standard form. An illustrative example of a hybrid vehicle (KUDU II) is analyzed with the proposed method

Investigations with a bandwidth measure for fatigue assessment of the Foinaven dynamic umbilical including VIV

An innovative use of a method to detect Vortex Induced Vibration (VIV) bandwidth in the curvature data of subsea flexible risers and umbilicals is presented. The parameter epsilon gives a valuable estimate of the bandwidth of signals such as VIV as a single value which may be used to track the behaviour with time and against other measures such as current speed. The method is conveniently based on a peak counting approach originally used in a marine context by Cartwright and Longuet-Higgins. Low epsilon values close to zero indicate a narrow-band process whereas values near unity indicate a broad-band process. Curvature and environmental data were gathered by the Foinaven Umbilical Monitoring System (FUMS) installed on the Foinaven Petrojarl IV floating production unit located in the Atlantic margin, west of Shetland. The VIV frequency range owing to current excitation considered is that in the range 0.2–2 Hz. This paper presents analyses showing the correlation of the epsilon bandwidth parameter with standard deviation of curvature, current speed and spectral analysis results for extended periods measured on the Foinaven dynamic umbilical. Examination of the number of frequencies and their values using spectrograms over long periods enable interesting interpretation of the build-up and decay of the VIV behaviour. These data are also reduced to the predominant peak frequencies, and standard deviation along with epsilon to provide a compact description of the VIV behaviour over 10 min intervals. Clear frequency and amplitude shifts can be observed as VIV varies with current ebb and flow. The behaviour is usefully described using only epsilon, standard deviation, and peak frequencies. The importance of epsilon for fatigue damage assessment is demonstrated through a formulation derived by Wirsching and Light. Strong VIV regimes are often characterized by an intense activity around a particular frequency and the impact of such relatively narrow-band events on the fatigue life of the structure is clearly demonstrated. This paper also presents the relative contributions of mooring, and waves/vessel motions, and VIV to fatigue damage. Although wave excitation remains the main source of fatigue, VIV appears to potentially contribute to a significant part of the overall fatigue dama

Investigations with a bandwidth measure for fatigue assessment of the Foinaven dynamic umbilical including VIV

An innovative use of a method to detect Vortex Induced Vibration (VIV) bandwidth in the curvature data of subsea flexible risers and umbilicals is presented. The parameter epsilon gives a valuable estimate of the bandwidth of signals such as VIV as a single value which may be used to track the behaviour with time and against other measures such as current speed. The method is conveniently based on a peak counting approach originally used in a marine context by Cartwright and Longuet-Higgins. Low epsilon values close to zero indicate a narrow-band process whereas values near unity indicate a broad-band process. Curvature and environmental data were gathered by the Foinaven Umbilical Monitoring System (FUMS) installed on the Foinaven Petrojarl IV floating production unit located in the Atlantic margin, west of Shetland. The VIV frequency range owing to current excitation considered is that in the range 0.2–2 Hz. This paper presents analyses showing the correlation of the epsilon bandwidth parameter with standard deviation of curvature, current speed and spectral analysis results for extended periods measured on the Foinaven dynamic umbilical. Examination of the number of frequencies and their values using spectrograms over long periods enable interesting interpretation of the build-up and decay of the VIV behaviour. These data are also reduced to the predominant peak frequencies, and standard deviation along with epsilon to provide a compact description of the VIV behaviour over 10 min intervals. Clear frequency and amplitude shifts can be observed as VIV varies with current ebb and flow. The behaviour is usefully described using only epsilon, standard deviation, and peak frequencies. The importance of epsilon for fatigue damage assessment is demonstrated through a formulation derived by Wirsching and Light. Strong VIV regimes are often characterized by an intense activity around a particular frequency and the impact of such relatively narrow-band events on the fatigue life of the structure is clearly demonstrated. This paper also presents the relative contributions of mooring, and waves/vessel motions, and VIV to fatigue damage. Although wave excitation remains the main source of fatigue, VIV appears to potentially contribute to a significant part of the overall fatigue dama

Advance directives from haematology departments: the patient’s freedom of choice and communication with families. A qualitative analysis of 35 written documents

Abstract Background In France, advance directives are favourably perceived by most of the population, although the drafting rate is low. This ambivalence is challenging because advance directives are meant to promote the autonomy and freedom of choice of patients. The purpose of this study was to analyse the content of advance directives written by patients suffering from malignant haemopathies to better understand how patients put them into practice. These could be relevant as early as the initial diagnosis of haematological malignancies because of the uncertain course of the disease. Methods This was a multicentre, qualitative, descriptive study. The advance directives written by patients with malignant haemopathies treated in one of the six French hospital departments were included in the study from 01/06/2008 to 15/04/2016. A thematic analysis of the advance directives was performed by two researchers: a senior haematologist and a research assistant. Results The median age of the patients was 69. Most were women (sex ratio: 0.59), living as a couple (57%), with lymphoid pathologies (66%), who were still alive two years after the instructions were written (63%) and had nominated a health care proxy (88.6%). Free texts (62.9%) were richer in content than pre-defined forms. The advance directives were used in three ways: for a purely legal purpose, to focus on medical treatments or actions, or to communicate a message to the family. Three main themes emerged: (1) refusal of medical treatment (100%), in which patients express refusal of life-sustaining care (97.1%). The actual treatments or the moment when they should be limited or stopped were not always mentioned in detail. (2) A desire for effective pain relief to avoid suffering (57.1%) and (3) messages for their family (34.3%), such as funeral arrangements (17.1%) and messages of love or trust (14.3%). Conclusions Patients who write advance directives are not necessarily at the end of their lives. Their content mainly conveys treatment wishes, although patients also use them to pass on personal messages to their close family. This emerging role of advance directives to communicate messages within the family should be valued, even if it is not their original purpose