scholarly journals Numerical Analysis of the Take-Off Performance of a Seaplane in Calm Water

2021 ◽  
Vol 11 (14) ◽  
pp. 6442
Author(s):  
Yang Guo ◽  
Dongli Ma ◽  
Muqing Yang ◽  
Xing’an Liu
Keyword(s):  
Rigid Body Dynamics ◽  
Hydrodynamic Resistance ◽  
Static State ◽  
Stagnation Line ◽  
Dynamic Motion ◽  
Main Challenge ◽  
Calm Water ◽  
Marine Economy ◽  
The 1960S ◽  
Heave Motion

Nowadays, with the escalating tensions in maritime dispute and the development of marine economy, there has been renewed interest in seaplanes for their special capacity of taking off and landing on water. Prediction of take-off performance, involving aerodynamic analysis and hydrodynamic analysis, is a main challenge in seaplane design, while the prediction methods have been little improved since the 1960s. This paper aims to investigate the attitude and resistance characteristics of a seaplane at different speeds during the take-off by numerically modeling the air-water flow field using RANS equations with VOF method. The trim and heave motion of seaplane in response to aerodynamic forces, hydrodynamic forces, hydrostatic forces, and propeller thrust was realized by solving rigid body dynamics equations and adopting dynamic overset mesh technique. The variations in heave, trim angle, and resistance characteristics during the takeoff were investigated, and their inherent relationships with the aerodynamic, hydrodynamic, and hydrostatic performance were revealed. Particular investigation on the hydrodynamic resistance indicates that the stagnation line located at the convex bow would contribute a considerable increase of pressure resistance at the first hump, and the trim angel of a seaplane should be operated in an optimum trim range, typical between 4–6 deg, to minimize the hydrodynamic resistance at the second hump. Additionally, the dynamic motion convergence study proves that the utilization of damping terms was an effective way to accelerate the convergence of the dynamic motion ending with a quasi-static state.

Dynamic Analysis and Configuration Design of a Two-Component Wave-Energy Absorber

2012 ◽  
Author(s):  
Christophe Cochet ◽  
Ronald W. Yeung
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Outer Cylinder ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Energy Extraction ◽  
Energy Absorber ◽  
Compound Cylinder ◽  
Motion Study ◽  
Heave Motion

The wave-energy absorber being developed at UC Berkeley is modeled as a moored compound cylinder, with an outer cylinder sliding along a tension-tethered inner cylinder. With rigid-body dynamics, it is first shown that the surge and pitch degrees of freedom are decoupled from the heave motion. The heaving motion of the outer cylinder is analyzed and its geometric proportions (radii and drafts ratios) are optimized for wave-energy extraction. Earlier works of Yeung [1] and Chau and Yeung [2,3] are used in the present heave-motion study. The coupled surge-pitch motion can be solved and can provide the contact forces between the cylinders. The concept of capture width is used to characterize the energy extraction: its maximization leads to optimal energy extraction. The methodology presented provides the optimal geometry in terms of non-dimensional proportions of the device. It is found that a smaller radius and deeper draft for the outer cylinder will lead to a larger capture width and larger resulting motion.

Numerical Modelling of a Planing Craft with a V-Shaped Spray Interceptor Arrangement in Calm Water

2020 ◽  
Author(s):  
Mikloš Lakatoš ◽  
Kristjan Tabri ◽  
Abbas Dashtimanesh ◽  
Henrik Andreasson
Keyword(s):  
Reaction Force ◽  
The Other ◽  
Numerical Comparison ◽  
Total Resistance ◽  
Stagnation Line ◽  
Planing Craft ◽  
Water Conditions ◽  
Calm Water ◽  
Wetted Surface Area ◽  
Novel Concept

V-shaped spray interceptors are a novel concept of spray deflection on planing craft. Conventional spray rails are positioned longitudinally on the bottom of the hull and detach the spray from hull deflecting it towards the sides or slightly down and aftward. The V-shaped spray interceptors, on the other hand, are located in the spray area forward of the stagnation line such that they would deflect the oncoming spray down and aftward, thereby producing a reaction force that reduces the total resistance. An experimental study reported that the V-shaped spray interceptors to reduce the total resistance at low planing speed by up to 4%. This paper features a numerical comparison of two planing craft, one equipped with a conventional setup of longitudinal spray rails and the other with a V-shaped spray interceptor. Both configurations were simulated in calm water conditions and were free to pitch and heave in a speed range of Fr∇ = 1.776 to 3.108. The numerical model was analyzed for grid sensitivity and numerical results were compared with experimental results. The two concepts were compared in terms of total resistance, lift, running position and wetted surface area. Conventional spray rails were shown to account for up to 5.6% of total lift and up to 6.5% of total resistance. The V-shaped spray interceptor was shown to reduce the total resistance by up to 8%. Since the V-shaped spray interceptor was located in the spray area forward of the stagnation line, it deflected the oncoming spray thereby producing a horizontal reaction force (-1.5% of RTM) in the direction of the craft’s motion. The rest of differences in the total resistance of the hulls equipped with the conventional spray rails and the V-shaped spray rails was due to absence of the resistance of the absent spray rails.

Interactive Two-Stage Rendering Technique of Deformable Part Through Haptic Interface

2011 ◽  
Author(s):  
Zhaoguang Wang ◽  
Georges Dumont
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Rigid Body Dynamics ◽  
Haptic Interaction ◽  
Two Stage ◽  
Deformation Spaces ◽  
The Real ◽  
Time Deformation ◽  
Main Challenge ◽  
On Line

Virtual Reality technology has been widely applied in the background of industrial evaluation applications. However, a large majority of these applications are focusing on haptics-based assemblies which mainly deal with rigid-body dynamics. Here we concern the real-time haptic interaction with deformable mock-ups aiming at the industrial design evaluation of mechanical parts. The main challenge of this application is that a tradeoff between the deformation accuracy and the interaction performance has to be achieved. In this paper, we propose a two-stage method for a real-time deformation modelling by combining an off-line pre-computation phase and an on-line deformation interaction phase. The key contributions of this paper lie on two aspects. First, during off-line phase, we propose a mesh analysis method which allows us to pre-compute different deformation spaces by anticipating the evaluation scenarios. Moreover, a real-time switch among different deformation spaces is developed so that the on-line deformation computation can focus on degrees of freedom where necessary with respect to users’ interactions. Second, during on-line phase, we apply a division scheme to divide the deformation process into two separate modules which are implemented on different threads to ensure the haptic interaction performance. Experiments are carried out based on a prototype implementation concerning different models of growing complexity. The deformation accuracy and the real-time performance are discussed.

Added Mass and Damping of Rectangular Bodies Close to the Free Surface

1984 ◽  
Vol 28 (04) ◽  
pp. 219-225
Author(s):  
John Nicholas Newman ◽  
Bjørn Sortland ◽  
Tor Vinje
Keyword(s):  
Hydrodynamic Force ◽  
Standing Waves ◽  
Present Theory ◽  
Added Mass ◽  
The Body ◽  
Simple Explanation ◽  
Two Dimensional ◽  
Infinite Depth ◽  
Calm Water ◽  
Heave Motion

A submerged two-dimensional rectangle in calm water with infinite depth is studied. The rectangle is oscillating in a heave motion. Negative added mass and sharp peaks in the damping and added-mass coefficients have been found when the submergence is small and the width of the shallow region on top of the rectangle is large. Resonant standing waves will occur in this area. A linear theory is developed to provide a relatively simple explanation of the occurrence of negative added mass for submerged bodies. The vertical hydrodynamic force is associated only with the flow in the shallow region, and the resulting pressure which acts on the top face of the rectangle. The results from this theory are compared with numerical results from the Frank method. The importance of the interaction effect between the top and the bottom of the body, which is neglected in the present theory, is discussed.

scholarly journals Wave loadings on a vertical cylinder due to heave motion

1995 ◽  
Vol 18 (1) ◽  
pp. 151-170 ◽  
Author(s):  
D. D. Bhatta ◽  
M. Rahman
Keyword(s):  
Velocity Potential ◽  
Diffraction Problem ◽  
Vertical Cylinder ◽  
Finite Depth ◽  
Wave Forces ◽  
Wave Loads ◽  
Exterior Region ◽  
Calm Water ◽  
Heave Motion ◽  
Fixed Structure

Wave forces and moments due to scattering and radiation for a vertical circular cylinder heaving in water of finite depth are derived analytically. These are derived from the total velocity potential which can be decomposed as two velocity potentials; one due to scattering in the presence of an incident wave on fixed structure (diffraction problem), and the other due to radiation by the heave motion on calm water (radiation problem). For each part, the velocity potential is derived by considering two regions, namely, interior region and exterior region. The complex matrix equations are solved numerically to determine the unknown coefficients to compute the wave loads. Some numerical results are presented for different depth to radius and draft to radius ratios.

scholarly journals The evolution of the Strategic role of Designers for Sustainable Development

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Brian BALDASSARRE ◽  
Giulia CALABRETTA ◽  
Nancy BOCKEN ◽  
Jan Carel DIEHL ◽  
Duygu KESKIN
Keyword(s):  
Sustainable Development ◽  
Business Models ◽  
Large City ◽  
Active Role ◽  
Main Challenge ◽  
Business Perspective ◽  
Strategic Role ◽  
The 1960S ◽  
Strategic Goal

Design for Sustainable Development refers to the application of a design process to solve a problem related to sustainability, such as creating a pair of shoes that can be recycled or managing waste collection in a large city. Since the origins of this concept in the 1960s, Design for Sustainable Development has been evolving, gradually broadening its scope over time from the design of products to the design of services, business models and wider ecosystems. In this evolution, designers have come closer and closer to business problems, thus becoming more strategic. In this paper, we explore this evolution from a business perspective. We visualize it into a framework and interview eight academic experts about the Strategic role of Designers for Sustainable Development. We find that the evolution can be framed around five topics: the strategic goal of designers, and their related perspective, language, key activities and main challenge. After discussing how the evolution took place around each topic, we draw implications for designers and managers who are willing to play an active role in the transition towards sustainable development.

scholarly journals OFFSHORE FLOATING MARINE FISH CAGE AQUACULTURE DEVELOPMENT PLANNING EVALUATION BASED ON HYDRO-OCEANOGRAPHY CONDITIONS IN SABANG BAY, WEH ISLAND

2019 ◽  
Vol 11 (1) ◽  
pp. 151-162
Author(s):  
Ulung Jantama Wisha ◽  
Guntur Adhi Rahmawan ◽  
Koko Ondara ◽  
Wisnu Arya Gemilang ◽  
Ruzana Dhiauddin ◽  
...  
Keyword(s):  
Development Planning ◽  
Water Area ◽  
Conservation Area ◽  
Offshore Area ◽  
Marine Tourism ◽  
Calm Water ◽  
Marine Economy ◽  
Tidal Condition ◽  
Cage Aquaculture ◽  
Coastal Bay

Sabang coastal bay becomes the area of significance where the development centered in the semi-enclosed area. Sabang Bay is well-known as the center of marine economy (Aquaculture, Harbor, and marine tourism). Recently, there is a planning initiated by Ministry of Marine Affairs and Fisheries (MMAF) to install the floating fish cage aquaculture (KJA) in the offshore area of Sabang Bay which the planning becomes a controversy between local people, local government, and researchers as well. This study aims to evaluate and discuss the impacts that will be happened if KJA is applied. Field surveys on hydro-oceanography aspects were done measuring currents, tides, waves, winds, bathymetry, water quality, as well as tourism condition. Based on those hydro-oceanography conditions, Sabang Bay categorized into calm water area where the sea current is weak (ranging from 0-0.12 m/s), whilst the high values of pH, salinity, and temperature are identified within the bay during low tidal condition. If KJA is installed within the bay, automatically it will pollute the water due to the accumulation of remaining fish feeder wastes. Moreover, within the bay, there are several attractive marine tourisms such as diving sites, the conservation area of Sophie Rickmers shipwreck site, and hot bubble (fumaroles hydrothermal vent). The presence of KJA will possibly disrupt marine tourism activities so that the implementation of KJA needs to be considered the impacts before installation.

scholarly journals Lessons Learned from 55 (or More) Years of Professional Experience in Urban Planning and Development

2021 ◽  
Vol 6 (2) ◽  
pp. 218-224
Author(s):  
Han Verschure
Keyword(s):  
Urban Planning ◽  
Rapid Change ◽  
Lessons Learned ◽  
Urban Life ◽  
The Earth ◽  
Main Challenge ◽  
Quality Of Urban Life ◽  
The Rich ◽  
The 1960S ◽  
As If

Reflecting on the many debates over the years on changing urbanization processes, on the towns and cities of yesterday, today, and tomorrow, the main challenge will be listening to lessons of wisdom from the past and adapting these to our future professional work. When Chief Seattle said that the Earth does not belong to us, we belong to the Earth, he called for more humility and respect so as to plan for the needs of today and tomorrow, and not for the greed of a few. The doomsday scenarios of overpopulation only make sense if we continue to exploit our planet the way we do today, as if we have an infinite reservoir of resources. Already back in the 1960s, Barbara Ward, John F. C. Turner, and particularly Kenneth Boulding taught me to rethink our whole perception of Spaceship Earth. I have seen many towns and cities grow as if resources were limitless; I myself have seen and worked on efforts to focus on spatial quality, respecting nature whenever possible for a growing number of people, recognizing resources as being precious and scarce, and yet guaranteeing equitable access to a good quality of urban life. Such objectives are not evident, when models in education, schools of thought, professional planners, and greedy developers are often geared towards the contrary: the higher the skyscrapers, the better; the more egotripping by architects, the more the rich like it; the more people are stimulated to consume, the better the world will be. Such narrow visions will no longer help. At several global urban planning and developments events (1976, 1992, 1996, 2016, etc.), new ideas and agendas have been put forward. Whether the present Covid-19 crisis may induce a more rapid change in vision and practice is still too early to confirm, but luckily, several towns and cities, and a few visionary planners and decision makers are showing some promising examples.

scholarly journals Feasibility Study of Selected Riser Concepts in Deep Water and Harsh Environment

2017 ◽  
Author(s):  
Gilang Muhammad Gemilang ◽  
Daniel Karunakaran
Keyword(s):  
Deep Water ◽  
Time History ◽  
Bending Moment ◽  
Harsh Environment ◽  
Steel Catenary Riser ◽  
Main Challenge ◽  
Large Motion ◽  
Touchdown Point ◽  
Heave Motion ◽  
Vessel Motion

One of the well-known riser systems, the Steel Catenary Riser (SCR), has been an attractive choice for the riser system in deep water. However, the main challenge of the SCR is large motions from the host platforms due to the harsh environment. The large motion of host platforms may induce excessive buckling and fatigue at the touchdown point. By screening the downward velocities at the hang-off point in the time history graph, the time at which the critical responses (i.e. buckling utilization, bending moment and compression) peak is identified. This study investigates the feasibility of the SCR configuration in terms of the capability to cope with the vessel motion. Several types of the SCR configurations are proposed in this study. The selected configurations of SCR in this study are conventional SCR, Weight Distributed SCR (WDSCR), and Steel Lazy Wave Riser (SLWR). The feasibility of the three riser configurations was analyzed in terms of strength and fatigue performance to understand the limitation of one over the other. The “lazy wave” configuration efficiently absorbs the vessel heave motions. Thereby the SLWR configuration is proven to be the most robust configuration to cope with large motion of the host platform. This study proves that although the SCR feasibility is limited due to vessel heave motion, innovative solutions can be established to extend its feasibility in order to cope with the vessel heave motion in harsh environment.

Hydrodynamic Resistance analysis of New Hull Design for Multipurpose Amphibious Vehicle Applying with Finite Volume Method

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
M. Nakisa ◽  
A. Maimun ◽  
Yasser M. Ahmed ◽  
F. Behrouzi ◽  
S. Steen ◽  
...  
Keyword(s):  
Hydrodynamic Resistance ◽  
Operating Life ◽  
High Speeds ◽  
Bow Wave ◽  
Flat Shape ◽  
Calm Water ◽  
Hull Design ◽  
Computational Fluid Dynamics Cfd ◽  
Comparative Results ◽  
Volume Method

This paper numerically investigated the hydrodynamic resistance of Multipurpose Amphibious Vehicles (MAV) in three bow shapes to approach the better hull bow shape design. This type of vehicle and other blunt-shaped floating vehicles encounter the problem of a large bow wave forming at high speeds. This wave formation is accompanied by higher resistance and at a critical speed results in bow submergence or swamping. Three new shapes of hull bow design for the multipurpose amphibious vehicle were conducted at several speeds to investigate the hydrodynamic phenomena using Computational Fluid Dynamics (CFD, RANS code) which is applied by Ansys-CFX14.0 and Maxsurf. The vehicle’s hydrodynamic bow shapes were able to break up induced waves and avoid swamping. Comparative results with the vehicle fitted with U-shape, V-shape and Flat-shape of hull bow, showed that the U-shape of the hull bow has reduced the total resistance to 20.3% and 13.6% compared with the V-shape and flat shape respectively. Though, the U-shape of hull bow is capable to increase the amphibious operating life and speed of vehicle in calm water. Also it has ability to reduce the vehicle’s required power, fossil fuel consumption and wetted hull surface.

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