Design, Analysis, and Development of a Wave-Current Laboratory

2020 ◽  
Author(s):  
Nhu Nguyen ◽  
Jacob Davis ◽  
Ahmed Alshuwaykh ◽  
Krish Thiagarajan Sharman
Keyword(s):  
Guide Vane ◽  
Offshore Structures ◽  
Maximum Height ◽  
Flow Uniformity ◽  
Marine Energy ◽  
Final Design ◽  
S Period ◽  
University Of Massachusetts ◽  
Current Loading ◽  
Flow Nonuniformity

Abstract In real ocean environments, offshore structures are exposed to a combination of wave and current loading conditions. This scenario presents the need to study fluid-structure interactions in the presence of both conditions, achievable through experimentation in a recirculating flume coupled with a wavemaker. The Ocean Resources and Renewable Energy (ORRE) group set out to design a recirculating wave-current flume at the University of Massachusetts Amherst to enable the study of technologies such as scale floating platforms and marine energy converters. In this paper, we present the methods used to arrive at an optimal flume design under strict spatial constraints posed by the available lab space. Limitations on the length, width, and height of flume are overcome via innovative flow designs and compact structures. The final design is approximately 11.5 m (37.7 ft) in length and 1.2 m (3.9 ft) wide with a nominal water depth of 1 m (3.3 ft). The 2 m long test section begins 6 m beyond the inlet of the flume to maximize flow uniformity. A 24” thruster driven by 75 hp electric motor maintains a current velocity of 0.5 m/s throughout the section while a wedge-shape plunger is implemented at the inlet to generate 0.6–2.8 s period waves with a maximum height of 0.2 m. During the design process, 2D computational fluid dynamics (CFD) simulations are employed to maximize flow uniformity over a range of inlet angles and guide vane configurations. In the optimal scenario, a flow nonuniformity of 8.7 % was obtained across a 0.7 m water column measured from the free surface. Results from the 3D simulation around the tight corner section showed significant increase in flow nonuniformity. The implementation of the screens along the flow path might be necessary in the future.

Henderson Hoops: A New System for Marine Growth Inhibition on Offshore Tubulars

1987 ◽  
Vol 109 (4) ◽  
pp. 357-360
Author(s):  
P. K. Stansby ◽  
T. Henderson
Keyword(s):  
Growth Inhibition ◽  
Marine Environment ◽  
Tidal Flow ◽  
Offshore Structures ◽  
Axial Motion ◽  
Final Design ◽  
New System

Polypropylene hoops encircling the tubulars of offshore structures are used to inhibit marine growth through their rotation which is induced by the action of current on flaps with a hinged connection to the hoop. Axial motion occurs naturally for inclined and horizontal tubulars in tidal flow and requires an extra vane attachment for vertical tubulars. Controlled tests in the marine environment suggest that the concept is nearly completely effective. The final design for the device which is being mass-produced is described.

Structural Analysis of Rigid High-Pressure Risers for Seismic Loads

2021 ◽  
Author(s):  
Mahesh Sonawane ◽  
Rohit Vaidya ◽  
Hunter Haeberle
Keyword(s):  
High Pressure ◽  
Offshore Structures ◽  
Mitigation Strategies ◽  
Seismic Loads ◽  
Wave Loading ◽  
Design Data ◽  
Final Design ◽  
Design Loads ◽  
Offshore Risers ◽  
Low Probability

Abstract Typically, the design of all offshore risers focuses on environmental loads i.e. wave loading, wind loads and currents. While these loads are ubiquitous in an offshore environment, accidental loading in the form earthquake induced seismic loads is an important criterion in the design of offshore structures. API RP 2A recommends site-specific studies as a basis for developing the ground motion specification of the design criteria, particularly for sites in areas of high seismicity (Zones 3–5). Seismic loads are low probability events in most cases and there isn't enough data in the initial pre-FEED / FEED phase of project to conduct seismic studies on the riser systems. Designers have to rely on past experience, code guidance, and assumptions for design data. In this paper through the means of two (2) case studies for a region prone with high seismic activities, we will demonstrate the challenges of designing rigid High-Pressure Riser Systems for seismic loads. A comparison will be provided for assumed loads based on code guidance and loads derived from preliminary seismic studies. In addition, comparisons will be provided for the final design loads achieved after the detailed platform design. The results will show the risks of relying solely on one source of data in the design process that can imperil the fabrication / procurement process with redesign due to unforeseen loads. Design optimization through proper centralization and other mitigation strategies will be presented for the benefits of future concrete based fixed platform projects.

Design of a Guide Vane for Improving Inside Flow Uniformity of Electrostatic Precipitator

2013 ◽  
Vol 62 (4) ◽  
pp. 523-528
Author(s):  
Kyung-Wook Noh ◽  
Seong-Jun Bae ◽  
Sookhee Park ◽  
Sunkyun Kang ◽  
Jangmyung Lee
Keyword(s):  
Electrostatic Precipitator ◽  
Guide Vane ◽  
Flow Uniformity

Automated Aerodynamic Optimization of an Aggressive S-Shaped Intermediate Compressor Duct

2018 ◽  
Author(s):  
T. Stürzebecher ◽  
G. Goinis ◽  
C. Voss ◽  
H. Sahota ◽  
P. Groth ◽  
...  
Keyword(s):  
Guide Vane ◽  
Aerodynamic Optimization ◽  
Baseline Design ◽  
Separating Flow ◽  
High Pressure Compressor ◽  
Important Research Topic ◽  
Final Design ◽  
Endwall Contouring ◽  
Aero Engines ◽  
Pressure Compressor

As bypass-ratio in modern aero engines is continuously increasing over the last decades, the radial offset between low pressure compressor (LPC) and high pressure compressor (HPC), which needs to be overcome by the connecting s-shaped intermediate compressor duct (ICD), is getting higher. Due to performance and weight saving aspects the design of shorter and therefore more aggressive ducts has become an important research topic. In this paper an already aggressive design (with respect to current aero engines) of an ICD with integrated outlet guide vane (OGV) is used as a baseline for an aerodynamic optimization. The aim is to shorten the duct even further while maintaining it separation free. The optimization is broken down into two steps. In the first optimization-step the baseline design is shortened to a feasible extent while keeping weak aerodynamic restrictions. The resulting highly aggressive duct (intermediate design), which is shortened by 19 % in axial length with respect to the baseline, shows separation tendencies of low momentum fluid in the strut/hub region. For the second step, the length of the optimized duct design is frozen. By implementing new design features in the process of the optimizer, this optimization-step aims to eliminate separation and to reduce separation tendencies caused by the aggressive shortening. In particular, these features are: a nonaxisymmetric endwall contouring and parametrization of the strut and the OGV to allow for changes in lift and turning in both blade designs. By comparison of the three designs: Baseline, intermediate (separating flow) and final design, it can be shown, that it is possible to decrease length of the already aggressive baseline design even further, when adding a nonaxisymmetric endwall contouring and changes in blade shape of the strut and OGV. Flow separation can be eliminated while losses are kept low. With a more aggressive and therefore shorter duct the engine length and weight can be reduced. This in turn leads to lighter aircrafts, less fuel consumption and lower CO2 and NOx emissions.

Unsteady Blade and Disk Resonant Stress Analysis Due to Supersonic Inlet Guide Vane Wakes

2008 ◽  
Author(s):  
G. Nordwall ◽  
M. Leduc ◽  
A. Demeulenaere
Keyword(s):  
Stress Analysis ◽  
Guide Vane ◽  
Pressure Ratio ◽  
Electrical Power ◽  
Specific Power ◽  
Inlet Guide Vane ◽  
Wake Structure ◽  
High Pressure Ratio ◽  
High Order Harmonic ◽  
Final Design

A high specific-power radial inflow turbine is currently being designed for installation in the fall of 2008. This turbine will generate 7,000–18,500 HP (5–14 MW) of electrical power. Operating with a relatively high pressure ratio and high molecular weight (58), which is common in geothermal power generation applications, the process has the ability to produce a very strong wake structure. Such wakes have caused catastrophic impeller fatigue failures in similar applications. To prevent a failure, the current design is based on a study of the interaction between the wake structure and the impeller. The SAFE and Campbell diagram are used for screening purposes, but the final design is analyzed using an unsteady CFD analysis coupled with time-dependent Finite Element Stress analysis. This pairing of CFD and FEA analysis allows the alternating torque to be determined both under resonant and non-resonant conditions. With this analysis, it is possible to approximate the stress resulting from higher order resonant frequencies which cannot be avoided in blade tuning. The analysis has shown that a high order harmonic of the vane passing frequency will not lead to unacceptable alternating stress levels. To facilitate future analysis, the 360° unsteady solution was compared to a harmonic analysis with two harmonic frequencies. The harmonic solution has shown good agreement with the full 360° solution.

scholarly journals A CFD-Based Shape Design Optimization Process of Fixed Flow Passages in a Francis Hydro Turbine

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1392
Author(s):  
Ujjwal Shrestha ◽  
Young-Do Choi
Keyword(s):  
Design Optimization ◽  
Draft Tube ◽  
Guide Vane ◽  
Optimization Techniques ◽  
Optimization Process ◽  
Shape Design ◽  
Flow Uniformity ◽  
Hydro Turbine ◽  
Shape Design Optimization ◽  
Hydro Turbines

In recent times, optimization began to be popular in the turbomachinery field. The development of computational fluid dynamics (CFD) analysis and optimization technology provides the opportunity to maximize the performance of hydro turbines. The optimization techniques are focused mainly on the rotating components (runner and guide vane) of the hydro turbines. Meanwhile, fixed flow passages (stay vane, casing, and draft tube) are essential parts for the proper flow uniformity in the hydro turbines. The suppression of flow instabilities in the fixed flow passages is an inevitable process to ensure the power plant safety by the reduction of vortex-induced vibration and pressure pulsation in the hydro turbines. In this study, a CFD-based shape design optimization process is proposed with response surface methodology (RSM) to improve the flow uniformity in the fixed flow passages of a Francis hydro turbine model. The internal flow behaviors were compared between the initial and optimal shapes of the stay vane, casing, and the draft tube with J-Groove. The optimal shape design process for the fixed flow passages proved its remarkable effects on the improvement of flow uniformity in the Francis hydro turbine.

Optimal Design of Reaction Hydro Turbine Model Stay Vane by Vane Angle and Thickness Distribution

2019 ◽  
Author(s):  
Ujjwal Shrestha ◽  
Jungwan Park ◽  
Young-Do Choi
Keyword(s):  
Flow Field ◽  
Guide Vane ◽  
Thickness Distribution ◽  
Leading Edge ◽  
Optimization Techniques ◽  
Design Parameters ◽  
Angle Distribution ◽  
Flow Uniformity ◽  
Pump Turbine ◽  
Vane Angle

Abstract Optimization is uprising technology in the engineering field, which enhance the performance of mechanical components. Likewise, upcoming turbomachinery designs need to be more efficient, cost-effective and easy manufacturing. Many optimization techniques have implemented for the development of efficient turbomachines. In this study, the optimization has mostly confined to the stay vane of reaction turbine like Francis, Pump Turbine etc. Stay vanes are mainly used to direct the flow towards guide vane and runner in the reaction type turbine (Francis, Pump Turbine). The three-dimensional flow field from the spiral casing is highly distorted, which causes secondary flow. However, the uniform flow field has maintained by stay vane. Due to steady flow field from stay vane, the performance of the runner has improved. Therefore, the better design of stay vane has been required for the improvement of the flow field around the runner passage. The design parameters of the stay vane are vane angle distribution and thickness distribution from leading edge to trailing edge. The vane angle distribution controls the stability of flow field direction and momentum towards the runner. Similarly, the thickness distribution will maintain the profile of the stay vane. The optimization of stay vane has improved turbine efficiency, flow uniformity, and pressure loss. The multi-objective genetic algorithm (MOGA) was selected for the optimization of stay vane because it satisfies all the objective functions without being dominated by any specific solution. MOGA is a more realistic approach to optimization. The validation test of performance is conducted to compare the result of experimental and numerical methods. The optimized stay vane has improved the flow uniformity around the stay vane.

scholarly journals Recent work and prospective analysis on offshore structures and marine energy harvesting at the Faculty of Engineering of the University of Porto

2021 ◽  
Vol 1201 (1) ◽  
pp. 012043
Author(s):  
F Taveira-Pinto ◽  
P Rosa-Santos ◽  
T. Fazeres-Ferradosa
Keyword(s):  
Renewable Energy ◽  
Energy Harvesting ◽  
Offshore Structures ◽  
Future Research ◽  
Marine Renewable Energy ◽  
The Past ◽  
Energy Group ◽  
Marine Energy ◽  
The University ◽  
Offshore Oil

Abstract Marine energy harvesting and offshore structures for marine renewable energy exploitation rise as a trending topic of both research and industrial activities. However, many challenges are yet to be tackled and solved when it comes to place such equipment and structures at sea. Over the past years the Marine Energy Group at FEUP has been tackling some of those challenges aiming at a better competitiveness of marine renewable energy in comparison to traditional oil & gas sector, which is more mature and developed at this point in time. Additionally, recent findings of this research team have also been applicable to several offshore oil & gas infrastructures. In this work, the latest contributions, projects and research outcomes developed by the team are reviewed and presented towards the enhancement of future research lines and industrial opportunities.

CFD-Based Hydraulic Design and Manufacturing of a Multistage Low Specific-Speed Diffuser Pump

2019 ◽  
Author(s):  
Martijn van der Schoot ◽  
Kevin Bruurs ◽  
Eric van der Zijden
Keyword(s):  
Manufacturing Process ◽  
Performance Test ◽  
Guide Vane ◽  
Response Surfaces ◽  
Pump Design ◽  
Simulation Based Design ◽  
Final Design ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Mechanical Pump

Abstract A multistage low specific-speed diffuser pump was designed to achieve very good hydraulic performance with a newly designed integrated diffuser, crossover and return guide vane. The diffuser was designed using a continuous crossover design. The design space of this diffuser was limited because of the usage of a mechanical pump design from a similar existing pump. This paper presents the simulation-based design of this new pump and the role that simulation can play in the manufacturing process. A new diffuser has been designed to obtain optimum efficiency and to ensure that the pump will operate most of its time very close its best efficiency point. The new diffuser was designed using an approach where the diffuser vane was stretched to completely cover the area starting just behind the impeller trailing edge towards the eye of the next stage impeller. This means that the diffuser vanes should now convert velocity into pressure, guide the fluid to the next stage impeller eye while reducing the swirl and uniformizing the flow. The shape of the diffuser has been optimized using response surfaces that were created using Computation Fluid Dynamics (CFD). This way, a diffuser with a minimum amount of losses was obtained, due to smooth and gradual area changes of the waterway. The final design incorporating this diffuser was analyzed using steady-state CFD to create the full performance curve. The design was transferred into a real physical product by manufacturing it. The resulting casting of the diffuser component was scanned using a 3D scanner. The 3D model of the scan was used to make a comparison using CFD between the performance of the designed and the manufactured diffuser. This provided understanding in how deviations due to the manufacturing process influence the performance. Finally, the complete pump underwent a performance test and its results closely matched the performance as calculated using CFD.

Impact of Micro-Droplets on Superhydrophobic and Hydrophilic Surfaces

2014 ◽  
Author(s):  
Hany Gomaa ◽  
Moussa Tembely ◽  
Nabil Esmail ◽  
Ali Dolatabadi
Keyword(s):  
Superhydrophobic Surface ◽  
Offshore Structures ◽  
Maximum Height ◽  
Power Cables ◽  
Ice Accretion ◽  
Major Threat ◽  
Hydrophilic Surfaces ◽  
Wide Range ◽  
The Difference ◽  
The Impact

Ice accretion is a major threat to all exposed structures such as wind turbines, overhead power cables, offshore structures and aircrafts. Such deposition starts by an impact of water droplets of different sizes on the surface of the exposed structure. This work aims to shed more light on the difference in the dynamics occurring upon the impact of microdroplets on substrates with various wettabilities, hydrophilic (aluminum) and Superhydrophobic (Aluminum + WX2100) surfaces. Experiments are conducted on a wide range of diameters, between cloud sized droplets with diameters ranging down to 20μm, and 10 times larger droplets with a diameter of 250 μm. A comparison in the impact (through deformation) results is made all through the wide range and explained using the two extremes. This is done experimentally by analyzing the maximum spread diameter on the hydrophillic surface and superhydrophobic surface and maximum height as a function of time on the hydrophillic surface. Both parameters are visualized experimentally, simulated numerically for the same impact velocities and then results are compared for verification.

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