Hydrodynamic Tests Research Articles

Method for Real-Time Hybrid Model Testing of ocean structures: Case study on horizontal mooring systems

This paper presents a method for Real-Time Hybrid Model testing (ReaTHM testing) of ocean structures. ReaTHM testing is an extension to traditional hydrodynamic model-scale testing, where the system under study is partitioned into physical and numerical substructures. The physical and numerical subsystems are connected in real-time through a control system. Based on experience with various ReaTHM tests, a general method for ReaTHM testing of ocean structures has been proposed. An experimental case study was carried out to illustrate the proposed method. The study was conducted in a state-of-the-art hydrodynamic laboratory, where a physical cylindrical buoy was placed in a still-water basin. Horizontal mooring loads from a numerical mooring system, which were modelled using the nonlinear finite element software RIFLEX were actuated onto the physical substructure. System performance was verified through comparison with a physical horizontal mooring system consisting of physical springs.

Геотермический мониторинг как способ прогноза вулканических извержений и оценки геоэнергетических ресурсов

Geothermal monitoring is an effective tool for predicting volcanic eruptions, as well as for assessing the geothermal energy potential of geothermal areas. Increased magmatic activity, an indicator of which is the penetration of hot volcanic gases through faults, has been observed in recent years on the Elbrus volcano. Since Elbrus is a year-round resort of world importance, in order to control volcanic and seismic activity, forecast and reduce the risks of eruption and earthquakes, it is recommended to drill a observation well on the slope of Elbrus with the installation of an underground fiber-optic system for temperature and pressure monitoring. In combination with microseismic, gravimetric and inclinometric observations, satellite IR imaging and geochemical gas testing, the continuously obtained information on the thermodynamic conditions of the subsoil will provide a reliable complex for the operational forecast of natural geophysical disasters. Utilization of the geothermal energy of the magma chamber in the artificial circulation systems of small GeoPPs, water injection from the surface and obtaining superheated water and steam from producing wells will reduce the risks of eruption and at the same time provide the resort with environmentally friendly thermal and electric power. Technological justification for the construction of a GeoPP will also require exploratory drilling to the area of ​​hot rocks, therefore information on the distribution of temperature and pressure along the wellbore is doubly valuable. In geothermal fields that are under development, to assess the spatial heterogeneity of the filtration characteristics can be a useful method of “thermal interference testing” – as a complement or alternative to hydrodynamic interference testing. It is recommended to conduct such an experiment at the North Mutnovsky geothermal field.

Review and historical overview of experimental facilities used in hull coating hydrodynamic tests

The prediction of hydrodynamic performance of hull coatings with different surface conditions is a challenging task. Moreover, with the emergence of new prototype coatings that are relatively smooth in terms of roughness characteristics, the accurate estimation of their drag is particularly important, as this will enable a good grading of drag reducing benefits of coatings. In the context of coating studies, the experimental methods are considered as the backbone and results obtained from experimental facilities with the required performance will enable accurate scaling of test results to full-scale ship results. Although numerical simulations like computational fluid dynamics have acquired the level of accuracy good enough to replace some of the systematic model testing used for ship design optimization, it is still not evident whether the simulations will be able to replicate the physical reality such as coating type, its roughness and biofilms accurate enough to enable predictions of the power requirements for ships. Therefore, this article gives insight into various coating hydrodynamic testing facilities and methods that are capable of measuring drag characteristics of coatings. The work highlights the details of each method and identifies the concepts and parameters needed to describe, implement and analyze hydrodynamic coating drag measurements. This article also summarizes the merits and demerits of each type of facility based on reports and studies reported in open literature. Finally, the authors propose a recommendation that can be incorporated into the design of the new hydrodynamic facility.

Design and Hydrodynamic Model Test of Mini Submarine Propeller with High Efficiency and Low Cavitation

Design and development of propellers for submarines are in some ways different from propellers for surface vessels. The most important demand is low acoustic signature and propeller efficiency. The design for the propulsor for submarine is a specialist task of a later stage of design. The propulsive efficiency has essensially three parts in the traditional method of approach. The first and major part is the efficiency of the propeller it self as a divice which may develop to overcome the resistance to motion the vessel. The aim of this research is to design a mini submarine propeller and obtain high efficiency and low cavitation. To reach this aim, model tests were performed both in Towing Tank and Cavitation Tunnel. From the propeller model tests, the result shows a good efficiency and low cavitation. 
 Keywords: Submarine , Propeller , Efficiency, Cavitation

A Fully Coupled Computational Fluid Dynamics Method for Analysis of Semi-Submersible Floating Offshore Wind Turbines Under Wind-Wave Excitation Conditions Based on OC5 Data

Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the DeepCwind semi-submersible floating platform with the National Renewable Engineering Lab (NREL) 5-MW baseline wind turbine model under combined wind–wave excitation environment conditions. Free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests for a regular wave are performed to validate the numerical model by inputting gross system parameters supported in the Offshore Code Comparison, Collaboration, Continued, with Correlations (OC5) project. A full-configuration FOWT simulation, with the simultaneous motion of the rotating blade due to 6-DOF platform dynamics, was performed. A relatively heavy load on the hub and blade was observed for the FOWT compared with the onshore wind turbine, leading to a 7.8% increase in the thrust curve; a 10% decrease in the power curve was also observed for the floating-type turbines, which could be attributed to the smaller project area and relative wind speed required for the rotor to receive wind power when the platform pitches. Finally, the tower-blade interference effects, blade-tip vortices, turbulent wakes, and shedding vortices in the fluid domain with relatively complex unsteady flow conditions were observed and investigated in detail.

Vertical flow constructed wetland planted with Heliconia psittacorum used as decentralized post-treatment of anaerobic effluent in Southern Brazil

In order to investigate the potential of vertical flow constructed wetlands (VFCWs), a 24.5 m2 surface area filled with gravel and planted with Heliconia psittacorum, was implemented as an experimental system for domestic wastewater treatment in southern Brazil. The aims of the study were to (i) evaluate the performance of a full scale system septic tank (ST) and VFCW for decentralized domestic wastewater treatment, and (ii) identify the influence of Heliconia for hydraulic characteristics and consequent performance of the VFCW. The applied load rates in the VFCW were, on average, 10 g biochemical oxygen demand (BOD) m−2 day−1, 4 g NH4+-N m−2 day−1 and a hydraulic loading rate (HLR) of 60 mm day−1. Physicochemical analyses of wastewater treatment were carried out through grab sample methodology, for 5 months. Additionally, hydrodynamic tests were performed during plant development using rhodamine. The study demonstrated the viability of the system for decentralized wastewater treatment in Brazil, with average removal efficiencies of 78% for chemical oxygen demand (COD) and 84% for total suspended solids (TSS), according to national effluent discharge regulations. In spite of media’s large size, the VFCW achieved good average removal efficiencies. The tracer test results showed that the VFCW average hydraulic detention time increased as plants grew. This may have occurred due to interception of wastewater applied on the macrophyte’s leaves as well as a reduction in filter media permeability caused by the spread of roots and rhizomes. These results indicate that the plants played an important role in increasing wastewater contact time in wetlands with high hydraulic conductivity such as a gravel VFCW.

Performing captive model tests with a hexapod

In this study, a hexapod, six-degree of freedom (DOF) platform has been implemented to perform the captive model tests. With this novel device, a physical ship model can be forced to produce independent or coordinated motions in six-DOF that cannot be accomplished by a traditional one. This paper starts with the demonstration of the principle of the novel captive model test device. The motion relations between the driving legs of the testing platform and the physical ship model have been derived, based on which the mathematical model of hydrodynamic force has been established. Next, the testing procedures have been given by performing hydrodynamic coefficients tests of a rectangular frame and two ship models using the novel test device. Finally, the test results are compared with the theoretical values to verify the reliability of the device. The test device proposed in this paper provides a novel alternative to the traditional captive model test devices. It can identify the complex hydrodynamic coefficients of the mathematical model simultaneously in a single device, which is of great significance for the efficient prediction of hydrodynamics performance of given ships and offshore structures.

KAJIAN SEAKEEPING KAPAL FERRY RO-RO 750 GT BERBASIS PENGUJIAN HIDRODINAMIKA

The Ferry Ro-Ro is a ship that functions to crossing inter island and to transport vehicles, passengers and goods. Building a ship requires a very large investment value so that the design of the ship is a very important consideration by conduct the intens study to determine the performance of a ship, one of them is the performance of the ship motion, endurance, and reliability while sailing which can be seen by conducting a hydrodynamic test in the form of a seakeeping test on the Ferry Ro-Ro Ship Model. This study conduct the seakeeping testing due to Ferry Ro-Ro 750 GT Ship Model which aims to predict the pattern of ship behavior by using the seakeeping test methods at Manoeuvering and Ocean Basin at Laboratorium Hidrodinamika Indonesia at Balai Teknologi Hirdoinamika - BPPT with th parameter Wave Height Hs = 2.50 m, Wave Period Tp = 9.00 s by heading 180 deg and 135 deg, and model scale is 1 : 21.19. The seakeeping test procedure for the Ferry Ro-Ro 750 GT Ship Model is based on ITTC No 7.5-02-07-02 standards. Testing of the ship model is conducted by using the method of free running where ship moving at a speed of 12 knots (actual scale). Analysis of measurement results is displayed in the form of Response Amplitude Operator (RAO) and statical analysis. The hydrodynamic test results in the form of a seakeeping test of Ferry Ro-Ro 750 GT Ship Model shows the value of Root Mean Square (RMS) of each direction of the ship relative to the direction of arrival of the wave (heading) 180 deg with roll value = 0.825 deg and pitch value = 2.231 deg. And heading 135 deg with roll value = 2.410 deg and pitch value = 1.797 deg, where NORDFORSK 1987 criteria standard for RMS roll value is 6 deg, and RMS pitch value is 1.5 deg.
 Keywords: Seakeeping, Ferry Ro-Ro, Hydrodynamics

Motion Characteristic Analysis of a Floating Structure in the South China Sea Based on Prototype Monitoring

Due to the complexity of ocean environmental loading models and the nonlinearity and empirical parameters involved in hydrodynamic numerical modeling and model testing, many uncertainties still exist in the design and operation of floating platforms. On-site prototype measurements provide a valid strategy for obtaining accurate environmental loading parameters and floater motion responses. A prototype monitoring system was built as part of a joint industrial project in the South China Sea. Long-term ocean environmental loading parameter data and structural dynamic motion responses were collected from 2012 to the present. In this study, the dynamic motions of the platform structure were analyzed using an artificial neural network (ANN) and data obtained during a typhoon. Numerical modeling was performed to analyze the platform parameters using a radial basis function (RBF), and hydrodynamic modeling was conducted using ansys-aqwa. Five geometric parameters related to the platform design were selected for optimization and included the mass, moments of inertia of the three rotation degrees, and the position of the center of gravity (COG). The mean values of the surge and pitch and the standard deviations of the roll and pitch were used as the input parameters. The model validations showed that the proposed ANN-based method performed well for obtaining the optimal platform parameters. The maximum errors of the roll, pitch, surge, and sway motions were within 5%. The updated response amplitude operators (RAOs) and new design indices for a 100-year return period of a typhoon were determined to guide operations and evaluate platform designs.

Troubleshooting in a full-scale wastewater treatment plant: what can be learnt from tracer tests

The experimental assessment of the actual reactor hydrodynamic behavior is aimed at detecting possible deviations from the design configuration, as well as suggesting corrective/improving modifications, efficacy of which can be also assessed in the aftermath. The hydrodynamic scheme can be defined by means of tracer tests (stimulus–response method) used for detecting the residence time distribution curve. This study shows the results of three hydrodynamic tests performed on a wastewater treatment plant half-line, in which a biological process (denitrification and oxidation–nitrification) is carried out. Hydrodynamic faults (in terms of dead space and/or flow bypass) were identified, and consequent actions suggested (i.e., change in submerged mixers orientation in the reactors; sinking of the final section of the sludge recirculation pipe below the free surface to avoid foaming phenomena; introduction of new mixed liquor recirculation lines). These actions, together with a careful selection of wastes to be treated, led to an improvement of the overall process performance.

Overexpansion of the SAPIEN 3 Transcatheter Heart Valve: An Ex Vivo Bench Study

ObjectivesThis study assessed the effect of overexpansion beyond labeled size (diameter) of transcatheter heart valves through an ex vivo bench study. BackgroundTranscatheter heart valves function optimally when expanded to specific dimensions. However, clinicians may sometimes wish to overexpand balloon-expandable valves to address specific clinical challenges. The implications of overexpansion have assumed considerable importance, and objective information to guide practice is limited. MethodsWe evaluated SAPIEN 3 transcatheter heart valves (Edwards Lifesciences, Irvine, California). Valves (diameters of 23, 26, and 29 mm) were expanded to nominal dimensions, and then incrementally overexpanded with balloons sized 1-, 2-, and 3-mm larger than the recommended diameter. Valves underwent visual, microcomputed tomography, and hydrodynamic evaluation at various degrees of overexpansion. ResultsSAPIEN 3 valves with labeled diameters of 23, 26, and 29 mm could be incrementally overexpanded to midvalve diameters of 26.4, 28.4, and 31.2 mm, respectively. With overexpansion, there was visible restriction of the valve leaflets, which was particularly evident with the smaller valves. After maximal overexpansion of a 26-mm valve a leaflet tear was observed. High-speed video demonstrated impaired leaflet motion of both the 23- and 26-mm valves and hydrodynamic testing documented a regurgitant fraction for the 23- and 26-mm valves above accepted international standards. The maximally overexpanded 29-mm SAPIEN 3 still had relatively normal leaflet motion and excellent hydrodynamic function. Durability was not specifically evaluated. ConclusionsOverexpansion of balloon-expandable valves is possible. However, excessive overexpansion may be associated with impaired hydrodynamic function, acute leaflet failure, and reduced durability. Smaller valves may be at greater risk with overexpansion than larger valves. Overexpansion is best avoided unless clinical circumstances are compelling.

A fourth-order accurate finite volume method for ideal MHD via upwind constrained transport

We present a fourth-order accurate finite volume method for the solution of ideal magnetohydrodynamics (MHD). The numerical method combines high-order quadrature rules in the solution of semi-discrete formulations of hyperbolic conservation laws with the upwind constrained transport (UCT) framework to ensure that the divergence-free constraint of the magnetic field is satisfied. A novel implementation of UCT that uses the piecewise parabolic method (PPM) for the reconstruction of magnetic fields at cell corners in 2D is introduced. The resulting scheme can be expressed as the extension of the second-order accurate constrained transport (CT) Godunov-type scheme that is currently used in the Athena astrophysics code. After validating the base algorithm on a series of hydrodynamics test problems, we present the results of multidimensional MHD test problems which demonstrate formal fourth-order convergence for smooth problems, robustness for discontinuous problems, and improved accuracy relative to the second-order scheme.

Bubbles and microbubbles for hydrodynamic test facilities

Bubbles are known to have important effects in hydrodynamic facilities such as cavitation tunnels, hydraulic flow loops, pumps, valves and turbines test facilities, towing tanks etc. They are also used to simulate real two-phase flows with various void fractions or bubble size distributions under different pressure and velocity conditions. In order to manage safely these problems or to simulate at best the prototype conditions, an arsenal of theoretical and experimental techniques is necessary, including: – The control of dissolved air, which is under the form of independent molecules moving in the water. – The control of nuclei which are generally microbubbles of some tens of micrometers. – The injection of emulsions. Emulsions are a mixture of water and bubbles of millimetric size. – The separation of free air. Free air concerns bubbles of any size. – The resorption and the control of bubbles growing or shrinking by diffusion of air in water. The production and control of bubbles also implies the use of dedicated measuring techniques. Among these are devices to measure the void fraction and size of bubbles in emulsions as well as dissolved gas: – Local optical and electrical probes [14], – Optical techniques, – Venturi measurements (susceptibility meters). Susceptibility is the pressure at which a nucleus must be submitted to explode and create a vapor bubble. – Optical and polarographic gages for dissolved O2 analysis. Finally, microbubbles can be utilized as non-polluting tracers for optical velocity measurements in water and transparent fluids, such as LDV or PIV. Many of these techniques have been developed by YLEC Consultants. Some of these can be utilized in fluids other than water, such as liquid metals.

The function of the modified novel 0.1 mm polytetrafluoroethylene hand-made valved conduit through the hydrodynamic test in vitro

Objective 0.1 mm polytetrafluoroethylene (PTFE) has been comfirmed to be better biocompatibable comparing to the bovine pericardium. The study aims to explore the appropriate hand sewed way for the 0.1 mm PTFE conduit and to assess the function through the hydrodynamic test in vitro. Methods The modified novel 0.1 mm PTFE hand-made valved conduit was tested with different size of 0.1 mm PTFE patch under TH-2200 machine in vitro. The 19 mm valved conduits were divided group A and B according to different width and lenth of 0.1 mm PTFE patch, comparing to the traditional bioprosthetic valve as group A0 and B0 relatively. In group A, the circumference of the conduit (π×d) mm was defined as the lenth of PTFE patch while (0.65×d+ 0.74) (mm) or (0.84×d) (mm) as width differently (group A1, group A2). In group B, the appropriate width was defined as the width of PTFE patch while π×d (mm) or (1.2π×d) (mm) as length differently (group B1, group B2). Then 14mm, 16mm and 22 mm valved conduits were made with the appropriate width and length from perious study to get tested as well as 19 mm conduits. Results Under the flow of 2, 3, 4, 5L/min, Gradiant pressure (ΔP) in group A1 and A2 was a little bit higher than A0. But there is no significant difference on effective orifice area (EOA) among A1, A2 and A0. The regurgitation fraction (RF) of group A2 is less than A1, but still more than A0 which showed (0.84×d) (mm) width was better than (0.65×d+ 0.74) (mm). There was no significant difference on ΔP and EOA between B1 and B2. But RF of B2 was much lower than B1, even better than B0, which showed (1.2π×d) (mm) length was better than (π×d) (mm) length. The 14, 16, 19 and 22 mm valved conduits made with (0.84×d) (mm) width and (1.2π×d) (mm) also showed low ΔP and few regurgitation. Conclusion Modified novel 0.1 mm PTFE hand-made valved conduits play a satisfying role on anti-regurgitation with the (0.84×d) (mm) width and (1.2π×d) (mm) length PTFE patch. Key words: Expanded polytetrafluoroethylene; In vitro; Handmade; Valve function

Motion Control and Motion Coordination of Bionic Robotic Fish: A Review

Fish’s outstanding motion and coordination performance make it an excellent source of inspiration for scientists and engineers aiming to design and control next-generation autonomous underwater vehicles within the framework of bionics. This paper offers a general review of the current status of bionic robotic fish, with particular emphasis on the hydrodynamic modeling and testing, kinematic modeling and control, learning and optimization, as well as motion coordination control. Among these aspects, representative studies based on ideas and concepts inspired from fish motion and coordination are discussed. At last, the major challenges and the future research directions are addressed in the context of integration of various research streams from ichthyologic, hydrodynamic, mechanical, electronic, control, and artificial intelligence. Further development of bionic robotic fish can be utilized to execute some specific missions in complex underwater environments, where operations are unsafe or impractical for divers or conventional underwater vehicles.

Calibration of two compact permanent magnet spectrometers for high current electron linear induction accelerators.

In this work, two compact, permanent magnet, electron spectrometers have been built to measure the electron beam energy at the Dual Axis Radiographic Hydrodynamic Test facility. Using H- and OH- anions, the spectrometers were calibrated at the Special Technologies Laboratory in Santa Barbara, California (USA). The spectrometers were mounted on a custom drift tube that allows the magnet assemblies to be translated, which increases the path length of the electrons traveling through the magnetic field and therefore increases the upper bound of the measurable electron kinetic energy. The measurable range of electron kinetic energies is between 2.8 MeV-4.1 MeV for the first spectrometer and 14.1 MeV-21.1 MeV for the second spectrometer, with an overall measurement uncertainty of 0.32%.

Dynamic characteristics of composite tilting pad journal bearing for turbine/generator applications

Tilting pad journal bearings have been employed for turbine, compressor, pump, and generator applications owing to their high loading capacity, excellent stability, and service durability at high operation speed compared to conventional journal bearings. For high-speed and high-performance applications, tilting pad journal bearings should reduce the rotor vibration. Therefore, the bearings are designed to have excellent damping characteristics. In this study, composite tilting pad journal bearings consisting of carbon fiber/epoxy composites and a backup metal are fabricated to increase the dynamic performance and durability. A modal analysis is performed to investigate dynamic stability of the composite tilting pad. Moreover, the damping coefficient of fluid film, oil film pressure, and orbit of rotor are calculated with respect to the liner materials under a hydrodynamic lubrication state. To verify the analysis results, hydrodynamic lubrication tests of composite and white metal tilting pad journal bearings are conducted using an industrial test bench. As a result, the composite tilting pad journal bearing has effectively reduced the rotor vibration and increased the stability and durability of the bearing system compared to the white metal tilting pad journal bearing.

Direction-aware slope limiter for three-dimensional cubic grids with adaptive mesh refinement

In the context of finite volume methods for hyperbolic systems of conservation laws, slope limiters are an effective way to suppress creation of unphysical local extrema and/or oscillations near discontinuities. We investigate properties of these limiters as applied to piecewise linear reconstructions of conservative fluid quantities in three-dimensional simulations. In particular, we are interested in linear reconstructions on Cartesian adaptively refined meshes, where a reconstructed fluid quantity at a face center depends on more than a single gradient component of the quantity.We design a new slope limiter, which combines the robustness of a minmod limiter with the accuracy of a van Leer limiter. The limiter is called Direction-Aware Limiter (DAL), because the combination is based on a principal flow direction. In particular, DAL is useful in situations where the Barth–Jespersen limiter for general meshes fails to maintain global linear functions, such as on cubic computational meshes with stencils including only face-neighboring cells.We verify the new slope limiter on a suite of standard hydrodynamic test problems on Cartesian adaptively refined meshes. We demonstrate reduced mesh imprinting; for radially symmetric problems such as the Sedov blast wave or the Noh implosion test cases, the results with DAL show better preservation of radial symmetry compared to the other standard methods on Cartesian meshes.

Metody określania przepuszczalności in situ w warunkach kopalnianych na podstawie wyników testów hydrodynamicznych

Metody określania przepuszczalności in situ w warunkach kopalnianych na podstawie wyników testów hydrodynamicznych

CFD approach used for modelling hydrodynamic analysis and motion characteristics of a remotely operated vehicle

Towed underwater vehicles represents essential tools for providing safe access to the underwater world with many applications including ocean research, naval operations, inspection and repair different of undersea structures. Recently, there is a necessity to use smaller underwater vehicles, tethered or untethered by ship in rivers, lakes or oceans. This underwater vehicle represents an integral part of scientific equipment to explore the seas and oceans. Remotely operated vehicle (ROV) is one of these vehicles which consists of a surface body, connecting cable and underwater vehicle. The dynamic behavior of Remotely operated vehicle (translational and rotational motion or velocity, also sum of all forces acting on the system) is numerically investigated. This paper provided a model used for simulation and modeling approach to obtain the hydrodynamic characteristics of an underwater vehicle using computational fluid dynamic (performed by the Ansys CFX). This is the preliminary design stage where extensive hydrodynamic test facilities are not available.