Hydrodynamic Tests Research Articles

A SR-UKF-based method to identify submarine hydrodynamic coefficients

Objectives The square root unscented Kalman filter (SR-UKF) algorithm was developed for the identification of hydrodynamic coefficients, which are difficult to obtain accurately in submarine motion models. Methods Firstly, the hydrodynamic coefficients identification model was established based on the nonlinear mathematical model of submarine motion in the vertical plane, combined with the SR-UKF algorithm. Then, a sinusoidal maneuvering in the vertical plane was carried out by the automatic steering method and the generated data in addition to the measurement errors were chosen as the input for SR-UKF parameter identification. Finally, six viscous hydrodynamic coefficients in the vertical motion plane were identified through a numerical simulation. Results The simulation results show that, all identified hydrodynamic coefficients converge to fixed values within 3 000 seconds, and through the selection of appropriate initial values, the maximum error between the identification results and the standard values measured by a hydrodynamic test is only 1.5%. Conlusions SR-UKF can be effectively applied to identify submarine hydrodynamic coefficients, and can be further extended to real ship coefficients identification.

REFOS: A Renewable Energy Multi-Purpose Floating Offshore System

The present paper deals with the development of a multi-purpose floating tension leg platform (TLP) concept suitable for the combined offshore wind and wave energy resources exploitation, taking into account the prevailing environmental conditions at selected locations along the European coastline. The examined Renewable Energy Multi-Purpose Floating Offshore System (REFOS) platform encompasses an array of hydrodynamically interacting oscillating water column (OWC) devices, moored through tensioned tethers as a TLP platform supporting a 10 MW wind turbine (WT). The system consists of a triangular platform supported by cylindrical floaters, with the WT mounted at the deck’s center and the cylindrical OWC devices at its corners. Details of the modelling of the system are discussed and hydro-aero-elastic coupling between the floater; the mooring system; and the WT is presented. The analysis incorporates the solutions of the diffraction; the motion- and the pressure-dependent radiation problems around the moored structure, along with the aerodynamics of the WT into an integrated design approach validated through extensive experimental hydrodynamic scaled-down model tests. The verified theoretical results attest to the importance of the WT loading and the OWC characteristics on the dynamics of the system.

Inconsistencies arising from the coupling of galaxy formation sub-grid models to pressure-smoothed particle hydrodynamics

ABSTRACT Smoothed particle hydrodynamics (SPH) is a Lagrangian method for solving the fluid equations that is commonplace in astrophysics, prized for its natural adaptivity and stability. The choice of variable to smooth in SPH has been the topic of contention, with smoothed pressure (P-SPH) being introduced to reduce errors at contact discontinuities relative to smoothed density schemes. Smoothed pressure schemes produce excellent results in isolated hydrodynamics tests; in more complex situations however, especially when coupling to the ‘sub-grid’ physics and multiple time-stepping used in many state-of-the-art astrophysics simulations, these schemes produce large force errors that can easily evade detection as they do not manifest as energy non-conservation. Here, two scenarios are evaluated: the injection of energy into the fluid (common for stellar feedback) and radiative cooling. In the former scenario, force and energy conservation errors manifest (of the same order as the injected energy), and in the latter large force errors that change rapidly over a few time-steps lead to instability in the fluid (of the same order as the energy lost to cooling). Potential ways to remedy these issues are explored with solutions generally leading to large increases in computational cost. Schemes using a density-based formulation do not create these instabilities and as such it is recommended that they are preferred over pressure-based solutions when combined with an energy diffusion term to reduce errors at contact discontinuities.

Development of A High-Load Capacity Test Rig to Evaluate the Static Performance of Process Fluid-Lubricated Thrust Bearings

Electrical submersible pumps (ESPs) are artificial lift devices widely used in the oil and gas industry to increase production. For unconventional wells, which includes subsea applications, installation cost is an order of magnitude higher than the cost of the typical ESP, thus pump reliability is paramount. Contamination of the thrust bearing lubricant oil by process fluid due to seal failures is one of the leading causes of thrust bearing failure. While improving seal reliability can prevent thrust bearing failures, an alternative approach is to develop process-fluid lubricated thrust bearings. This research aims to characterize and study the performance of thrust bearings operating with process fluid lubrication. A component level-level test rig for testing the performance of thrust bearings in any mixture of water, sand, and air is designed, built, and commissioned. Initial tests of the PEEK and Tungsten Carbide (WC) bearings include a load capacity test to determine the hydrodynamic limit of the bearing, a hydrodynamic test to corroborate test rig stability, and a wear test to determine if the bearings can operate feasibly past hydrodynamic limits in a mixed lubrication regime. Initial results show that lubrication starvation can occur in an unpressurized chamber for low viscosity fluids that are not supplied directly to the bearing. Furthermore, the film thickness, temperature rise in the pads, and load capacity all are lower for water lubricated bearings when compared to oil lubricated bearings. Results suggest that liner material affects wear rate but not load capacity; however, operating even the WC bearings past hydrodynamic limits causes substantial wear and is not recommended as an operating mode. Polycrystalline Diamond (PCD) coated mixed lubrication bearings were also tested. These bearings, although requiring higher drive torque, sustained higher loads than the tilting pad bearings without significant wear

Correction to: Hydrodynamic Tests of Small-Sized Circulating Water Cooling Devices

To the article “Hydrodynamic Tests of Small-Sized Circulating Water Cooling Devices,” by K. E. Bondar’, N. S. Shulaev, and S. P. Ivanov, Vol. 56, Nos. 9-10, pp. 794–798, January, 2021

Tricuspid Versus Mitral Performance of Cylindrical Porcine Small Intestinal Submucosa Valves

Objective: Treatment options are extremely limited for children and older patients who are contra-indicated for receiving mechanical or bioprosthetic valves. The purpose of this study is to determine whether cylindrical porcine small intestinal submucosa (PSIS) bio-scaffold valves can facilitate robust valvular function in the tricuspid location. Methods: A 26-mm PSIS cylindrical valve (CorMatrix Cardiovascular) was sutured to a custom, 3D printed valve holder along two (150°) or three (120°) posts on the distal end. The annulus ring was sealed with a 3D printed cap. Hydrodynamic testing of the valves mounted in mitral and tricuspid positions were performed using a pulse duplicator system (Vivitro Labs) using 0.9% saline solution. A flow probe was affixed between atrium and ventricular chambers, and pressure transducers were inserted in the atrial, ventricular, and aortic locations. Tests utilized heart rate of 70 BPM, input S35 waveform comprising of a 35% systolic-65% diastolic configuration (Vivitest, Vivitro Labs), with a stroke volume of 50 mL for tricuspid (Noordegraaf 2019) and 71.4 mL for mitral conditions respectively. Results: Valve performance results in the tricuspid position showed a root mean square volumetric flow rate (QRMS) of 135 mL/s, a transvalvular pressure gradient (ΔP) of 3.97 mmHg, an effective orifice area (EOA) of 1.30 cm2, and a regurgitation factor (RF) of 7.70%. In the mitral position, the results showed a QRMS of 180 mL/s, a ΔP of 8.27 mmHg, an EOA of 1.08 cm2, and an RF of 8.34%. Conclusions: Preliminary data of cylindrical PSIS valves in both tricuspid and mitral positions show clinically acceptable hydrodynamics metrics of valve performance. Additional testing will help to establish statistical significances or lack thereof between the two valve groups.

Ex-vivo and In-vivo Validation of Novel Quantitative Videodensitometric Assessment of Mitral Regurgitation Following Surgical Mitral Valve Replacement

Objective: To investigate the accuracy and interobserver variability of Quantitative videodensitometric assessment of Mitral Regurgitation (QMR) after mitral valve replacement in a preclinical ovine model. Background: Quantitative videodensitometric aortography using the time-density principle is a well-documented technique for assessment of aortic regurgitation following transcatheter aortic valve replacement, but angiographic assessment of mitral regurgitation remains at best semi-quantitative (Sellers classification) and operator dependent. Methods: Fourteen sheep underwent surgical mitral valve replacement and were followed-up up to 1 year. A tricuspid valve with endogenous tissue restoration technology - the Xeltis valve (Xeltis BV, Eindhoven, the Netherlands) was implanted in 9 animals and the Trifecta valve (St. Jude Medical, St. Paul, MN, USA) was implanted in 5 animals. At the end of the follow-up period, the animals underwent a cardiac catheterization to measure their cardiac output and transmitral gradients immediately followed by ventriculography for QMR, then the animals were euthanatized, and the valve and peri-valvular tissue were excised. A mock-circulation (HDT-500 Hydrodynamic Test System [BDC Laboratory, US]) was used to assess the ex-vivo regurgitation fraction at a cardiac output comparable to the measurement obtained in-vivo. The CAAS A-valve 2.0.2 (Pie Medical Imaging BV, Maastricht, the Netherlands) was used for assessment of QMR. The QMR values (ex-vivo or in-vivo) as well as interobserver agreements were quantified after one, two, three, and four heart cycles. Results: The in-vivo QMR had significant correlations with the ex-vivo regurgitation fraction in all the cardiac cycles (best correlation: after 3 beats R2=0.784; p=0.002). The interobserver validation analysis showed significant agreements for all individual cardiac cycle (best agreement: after 4 beats R2=0.907; p<0.001). Conclusions: Angiographic quantification of mitral regurgitation using the CAAS-A valve prototype software is feasible, accurate, and highly reproducible in a preclinical setting. Further studies are necessary to establish the clinical value of this software.

Sustainable Improvement of Water Quality in Urban River Network by Rotating Overflow Weir—Case Study of Changzhou City in China

Water diversion is a practical and commonly used approach to improve the water quality of rivers in urban plains in China. This paper researches using rotating overflow weirs as the primary engineering solution to facilitate water diversion and improve the water quality of the river network in urban plain area of Changzhou, including hydrodynamic modeling, field tests, and application. The water diversion scheme, including clean water source, water transfer paths, quantity, and rate, was designed based on its current terrain and river systems. The Yangtze River was selected as a high-quality water source, and its two tributaries were utilized as clean water paths. Four rotating overflow weirs were proposed to create three stages of hydraulic gradient. Clean water can flow naturally and orderly in the researched urban river network without pumps. The required clean headwater level and clean water distributions were modeled hydrodynamically. Four temporary weirs were constructed at design locations to conduct field tests. And the water diversion scheme and its water quality improvement had been verified by field tests. Afterward, four permanent rotating overflow weirs were built. Currently, the monitoring results show the design water transfer scheme reaches expectations. The flow velocity in most rivers has been increased to 7cm/s from standstill in Changzhou's main urban plain area. The composite water quality of 93% river cross-sections monitored has been improved from Class V to Class Ⅲ and all have been improved to Class IV and above.

A Pin-on-Disk Tribometer for Friction and Lubricating Performance in mm-Scale

A pin-on-disk tribometer for micro-scale applications is presented in this paper. The tribometer consists of a stationary mm-scale pin and a rotating disk. Friction and lubrication film thickness are measured by a laser position detector and a laser displacement sensor. Using this tribometer, hydrodynamic tests have been carried out with the specimens fully submerged in a lubricant. Results suggest that the sliding motion in the mm-scale operates with a direct contact at low speed, and in the hydrodynamic regime at a higher speed. When the sliding reaches the critical speed, the lubricant film is established, and the thickness of the film stabilizes and the friction increases with the sliding speed. The tribometer shows good repeatability in these tests.

Optimal Actuator Placement for Real-Time Hybrid Model Testing Using Cable-Driven Parallel Robots

In real-time hybrid model testing, complex ocean structures are emulated by fusing numerical modelling with traditional hydrodynamic model testing. This is done by partitioning the ocean structure under consideration into a numerical and a physical substructure, coupled in real time via a measurement and control interface. The numerically computed load vector is applied to the physical substructure by means of multiple actuated winches so that the resulting experimental platform becomes a type of cable-driven parallel robot. In this context, the placement of the actuated winches is important to ensure that the loads can be accurately and robustly transferred to the physical substructure. This paper addresses this problem by proposing a performance measure and an associated actuator placement procedure that enables accurate force tracking and ensures that the numerically calculated loads can be actuated throughout the testing campaign. To clarify the application of the proposed procedure, it is applied to the design of a test setup for a moored barge. Overall, the paper represents a guideline for robust and beneficial actuator placement for real-time hybrid model testing using cable-driven parallel robots for load-actuation.

Design of a marine propeller for scale racing boats in a speed and energy efficiency contest

The process of optimized design, evaluation and manufacturing of high energy efficiency propellers for competition boats at scale is addressed in this research. This project uses the stages of hydrodynamic design, numerical testing and manufacturing of four prototypes as example. During the hydrodynamic design, three design methodologies were compared, namely: Blade Element Theory, lifting line theory and design based on DTMB propeller series. The objective function of the optimized design is based on obtaining the chord and pitch distribution that generates the greatest thrust, speed and efficiency. Similarly, the performance of each prototype was evaluated by CFD in a virtual channel registering thrust, torque and speed. Finally, the additive manufacturing process applied is presented. Prototyped propellers present efficiencies and maximum speeds approximately 15% higher than recommended commercial propellers for this type of boats. This study was developed by the Hydrometra group in the framework of the international competition Hydrocontest 2017.

Structural stability of novel composite heart valve prostheses - Fatigue and wear performance

Heart valve replacement is a very effective method to treat severe valvular stenosis or valvular insufficiency. The valve can be divided into the mechanical valve and biological valve according to the main materials of the valve leaflets. The former has good durability, but the patients need to take anticoagulants all their lives, otherwise, thrombosis will occur; the latter has good blood compatibility, and only 3–6 months of postoperative anticoagulation is required, but its durability is lower than the former. Compared with a traditional valve used materials, the fabric composite valve leaflets have both mechanical valve and biological valve advantages, i.e. it can have both good blood compatibility and excellent fatigue resistance. This material is comprised of the internal fabric layer and bilateral external polyurethane layers jointed with adhesive, and it can adjust the flexibility, wear-resistance and fatigue resistance of the valve leaflet through adjusting the thickness of the outer polyurethane protective layer, the weaving method, the fiber diameter and the surface density of the inner ultra-high molecular weight polyethylene (UHMWPE) fabric. In this article, we tested the long-term durability of a fabric composite with its property close to the valve leaflet made of bovine pericardium, to evaluate the material performance loss under long-term fatigue and the wear degree of this material with different polyurethane layer thicknesses. As many as two hundred million cycles of fatigue test and the hydrodynamic performance test before and after the fatigue test proved that the material could withstand a service life of at least five years without structural failure or functional degradation. According to the SEM images after the experiment, it can be predicted that this material can achieve a longer fatigue life.

Hydro-elastic response of composite hydrofoil with FSI

The present study investigates experimentally and numerically the impact of composite materials on hydro-elastic performances of a hydrofoil experiencing Fluid–Structure Interactions, and focus on the bend–twist coupling phenomenon. Four flexible hydrofoils piercing the free surface, with identical geometry of extruded plan-form, a constant NACA0015 section, are tested in a cantilevered configuration in a hydrodynamic flume. The hydrofoils are built from the same mold with different materials (carbon or glass fiber) and different layups. The layups are designed to allow or not bend–twist coupling by the use of ± 45°plies in the structure. Two different coupled FSI numerical approaches are developed to model the hydrofoils behavior: a low fidelity code based on the coupling of a Vortex Lattice Method and a beam theory and a high fidelity code made of the coupling of the structural model code–ASTER and an OpenFOAM VoF hydrodynamic model with free surface. Mechanical characterization of the hydrofoils highlights the differences on the structures which are exacerbated in the hydrodynamic tests. The bend–twist coupling induces a modification of the angle of attack at the tip, leading to a significant difference of the generated lift and thus the deformation. The bend–twist coupling and the hydrodynamic performances are simulated by the numerical approaches.

Mitral Valve-In-Valve: Defining the Indication Limits by in vitro Hydrodynamic Tests in a Brazilian Transcatheter Prosthesis.

IntroductionReoperations in cardiac surgery represent a clinical challenge, particularly because of the higher rate of perioperative morbidity and mortality. Mitral valve reoperation owing to bioprosthesis dysfunction, transcatheter treatment with a prosthesis implantation over the prosthesis has emerged as an alternative, especially for patients with a previous approach. In this study, we analyzed the hydrodynamic behavior of transcatheter prosthesis implantation in conventional mitral bioprostheses through hydrodynamic tests and produced a recommendation for the size of transcatheter valve most adequate for valve-in-valve procedure.MethodsMitral bioprostheses were attached to a flow duplicator and different combinations of transcatheter prostheses were implanted inside. The equipment simulates the hydrodynamic behavior of the valves submitted in vitro and determines transvalvular pressures and flow parameters.ResultsAll tests could be performed. Better hydrodynamic performance occurred for transcatheter prostheses 1 mm smaller than bioprostheses, except for the 27-mm bioprostheses. Effective valve areas (cm²) and transvalvular gradients (mmHg) were, respectively: Bioprosthesis × Inovare: 27 × 28 mm: 1.65 and 5.95/29 × 28 mm and 31 × 30 mm: 2.15 and 3.6.ConclusionThe mitral valve-in-valve implantation proved to be feasible in vitro. The use of 27-mm bioprostheses should be judicious, with preference for a 26-mm transcatheter valve. In the 29 and 31-mm bioprostheses, the implantation was very satisfactory, with good effective valve areas and transvalvular gradients, with preference for smaller transcatheter valves.

Hydrodynamic Tests of Small-Sized Circulating Water Cooling Devices

This article presents a method for determining the hydrodynamic drag coefficient of sprinklers of small-sized circulating water cooling devices (mini cooling towers). Two types of mini cooling towers were compared (a small-sized cooling tower with a helical air flow and counterflow). For hydrodynamic testing, an experimental setup was developed and fabricated. The experiments to determine the drag coefficient were carried out depending on the air flow rate ranging from 0.5 to 3.0 m/sec and irrigation density ranging from 0 to 12 m3/(m2·h). It was shown that ОВ-65 sprinkler (for a mini tower with a helical air flow and a mesh shell diameter of 65 mm) has a higher hydrodynamic drag coefficient than OGGT-65 sprinkler (for a counterflow tower with a mesh shell diameter of 65 mm) with equal experimental parameters. The obtained hydrodynamic drag coefficients are approximated as linear relationships in the logarithmic coordinates of the hydrodynamic drag and Reynolds number. It is established that the drag coefficient is determined by the generalized relation A/ReK.

Force Tracking Using Actuated Winches With Position-Controlled Motors for Use in Hydrodynamical Model Testing

In this paper, we consider the problem of accurate force control using actuated winches, intended for use in real-time hybrid hydrodynamic model testing. The paper is also relevant to other cable-driven parallel robot applications that use force control in an inner control loop. For this problem, conventional strategies typically use actuated winches with torque-controlled servomotors directly connected to the cabled drum. In contrast, we propose using actuated winches with position-controlled servomotors that connect to the cabled drum via a clockspring. The servomotors are position controlled at drive-level and are rapid, accurate, robust, and simple to install. We show how this, combined with an accurate estimate of the clockspring deflection and stiffness, can yield fast and precise force tracking on moving objects. This includes proposing associated feedforward force-controllers that compensates for damping, angle-dependent force variations, delays, and non-constant clockspring characteristics. Extensive experimental testing on a 1 degree of freedom actuated mass-spring system supports the work.

Experimental study on the tension of cables and motion of tunnel element for an immersed tunnel element under wind, current and wave

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.

Simulating electrohydrodynamics with smoothed particle hydrodynamics based on a charge-conservative approach

This paper presents an EHD model for SPH based on a charge-conservative approach. Compared with the leaky dielectric model, the EHD model used in this paper was charge conserved, since no term in the charge conservation equation was neglected. An implicit SPH formula for calculating the electric potential from the electrical properties of the previous time step was constructed, based on the electric potential Poisson equation and the charge conservation equation. The SPH formulas of the electric field and the charge density were also presented. To implement the EHD boundary condition accurately, a scheme, with two kinds of EHD boundary dummy particles, was developed. Both static and hydrodynamic numerical tests were conducted, and the accuracy of the proposed EHD model for SPH was verified by comparison with the results of analysis, the FVM method and the existing ISPH with the leaky dielectric model. This study provides an efficient method for simulating complex EHD problems with SPH.

Subsea manifold installation: Operational windows estimation based on hydrodynamic model testing

In this paper, added mass and drag coefficients for typical subsea manifolds installation conditions are determined through experimental model tests. The forced oscillation test results show that the equipment has large drag coefficients in the low Keulegan-Carpenter (KC) region, which leads to higher damping. The results also show that the added mass increases with higher KC number values and is appreciably larger than those found in the literature for flat plates, even when extrapolated to a prism. With the experimentally obtained hydrodynamic coefficients, a series of analytical and numerical simulations are conducted for a typical installation operation for various sea states. The results show that the operational windows for subsea equipment installation are expanded when compared to the current conventional approach.

Facile Nonenzymatic Glucose Electrode Composed of Commercial CuO Powder and Ionic Liquid Binder

Commercially available micro-sized CuO powder was dispersed in the mixture of ethanol and protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]), a hydrophobic amide-type protic ionic liquid (IL), to prepare a composite paste for the modification of screen-printed carbon electrode (SPCE) via spin-coating. The fabricated SPCE\CuO−IL composite-based electrode showed a comparable activity as that of the nanonized metal-oxide based electrodes towards the electrochemical oxidation of glucose in alkaline solutions. Hydrodynamic chronoamperometry tests performed at +0.55 V showed a linear dynamic response of the electrode over the concentration range of 1 μM–2.8 mM with a sensor-sensitivity of 0.16 μA μM−1 in 0.1 M NaOH. The data also showed a linear dynamic response over the concentration range of 1 μM–4.6 mM with a sensor-sensitivity of 0.10 μA μM−1 in 0.1 M NaOH with 0.1 M NaCl, indicating that the major interferant Cl− had negligible effects on glucose detection . Ascorbic acid (AA) (in the physiological level) and ethanol also did not interfere with the detection. Detection of glucose in real samples showed the recovery ratios higher than 95 %. This study has clearly demonstrated that commercial CuO powder without nanostructure can provide sufficient reactivity to the electrocatalytic oxidation of glucose by using IL as the organic binder. Facile preparation of the micro-sized metal oxide-modified electrodes can be accordingly pursued.