Combined Experimental/Numerical Development of Propulsor Evaluation Capability

2010 ◽  
Author(s):  
Amanda M. Dropkin ◽  
Stephen A. Huyer ◽  
Charles Henoch
Keyword(s):  
Experimental Data ◽  
Open Water ◽  
Velocity Profiles ◽  
Full Scale ◽  
Cfd Modeling ◽  
Water Tunnel ◽  
Local Flow ◽  
Cfd Models ◽  
Advance Ratio ◽  
Full Scale Tests

Propulsor design methods utilize Computational Fluid Dynamics (CFD) to develop initial propulsor configurations and predict the full-scale in-water performance of these optimal designs. However, like all numerical models, these CFD models need experimental validation to provide a sufficient level of confidence in the design. The actual data needed to validate CFD models include propulsor inflow velocities and thrust and are impractical to collect for full-scale vehicles. As a result, the in-water propulsor performance can be significantly different than CFD predictions. Another approach in the propulsor design process is to experimentally test a subscale version of the vehicle and appropriately scale results. This scaling is often unreliable due to differences between open water conditions and the flow in the laboratory facility. This paper presents a method to combine CFD modeling with subscale experiments to improve full-scale propulsor performance prediction. Laboratory experiments were conducted on subscale generic torpedo models in the 12″ × 12″ water tunnel located at the Naval Undersea Warfare Center in Newport, Rhode Island. This model included an operational ducted post-swirl propulsor. Laser Doppler Velocimetry was used to measure several velocity profiles along the torpedo hull. The experimental data were used in this project to validate the CFD models constructed using the commercial CFD software, Fluent®. Initially, axisymmetric two-dimensional simulations investigated the bare body, hull only case, and a shrouded body without the propulsor. These models were selected to understand the axisymmetric flow development and investigate methods to best match the propulsor inflow. A variety of turbulence models including the realizable k-epsilon model and the Spallart-Almaras model were investigated and ultimately the numerical and experimental velocity profiles were found to match within 3%. Based on these water tunnel simulations, differences between the flow in the facility and open water could then be characterized. These differences quantified both the effect of Reynolds number as well as local flow acceleration due to tunnel blockage effects. Full 3-D flow simulations were then conducted with an operating propulsor and compared with the corresponding subscale experimental data. Finally, simulations were conducted for full-scale tests and compared with actual in-water data. While the in-water data was limited to propulsor rpm and vehicle velocity, the operating advance ratio could be determined as well as the estimated vehicle thrust. This provided a method to utilize CFD/experiments to bridge the gap between subscale and full-scale tests. The predicted in-water advance ratio of 1.87 was very close to the measured value of 1.75.

Combined Experimental/Numerical Development of Propulsor Evaluation Capability

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Amanda M. Dropkin ◽  
Stephen A. Huyer ◽  
Charles Henoch
Keyword(s):  
Experimental Data ◽  
Rhode Island ◽  
Axisymmetric Flow ◽  
Turbulence Models ◽  
Open Water ◽  
Velocity Profiles ◽  
Full Scale ◽  
Cfd Modeling ◽  
Advance Ratio ◽  
Full Scale Tests

This paper presents a method to combine computational fluid dynamics (CFD) modeling with subscale experiments to improve full-scale propulsor performance prediction. Laboratory experiments were conducted on subscale models of the NUWC Light underwater vehicle in the 0.3048 m × 0.3048 m water tunnel located at the Naval Undersea Warfare Center in Newport, Rhode Island. This model included an operational rim-driven ducted post-swirl propulsor. Laser Doppler Velocimetry was used to measure several velocity profiles along the hull. The experimental data were used in this project to validate the CFD models constructed using the commercial CFD software package, Fluent®. Initially, axisymmetric two-dimensional simulations investigated the bare hull, hull only case, and a shrouded body without the propulsor. These models were selected to understand the axisymmetric flow development and investigate methods to best match the propulsor inflow. A variety of turbulence models were investigated and ultimately the numerical and experimental velocity profiles were found to match within 3%. Full 3D flow simulations were then conducted with an operating propulsor and compared with the corresponding subscale experimental data. Finally, simulations were conducted for full-scale tests and compared with actual open-water data. While the open-water data was limited to propulsor rpm and vehicle velocity, the operating advance ratio could be determined as well as the estimated vehicle thrust. This provided a method to utilize CFD/experiments to bridge the gap between subscale and full-scale tests. The predicted open-water advance ratio was 10.3% higher than the experimental value, as compared with the 28% difference previously found from a linear extrapolation of Reynolds number from model scale to full scale. This method was then applied to two different research propulsor geometries and led to agreement between computational and experimental advance ratios on the order of 2%.

CFD Simulations of Lifeboat During Sailing Phase in Harsh Weather

2015 ◽  
Author(s):  
Vidar Tregde ◽  
Sverre Steen
Keyword(s):  
Degrees Of Freedom ◽  
Free Fall ◽  
Model Tests ◽  
Full Scale ◽  
Cfd Simulations ◽  
Thrust Coefficient ◽  
Cfd Models ◽  
Calm Water ◽  
Set Up ◽  
Full Scale Tests

A free fall lifeboat is going through several phases during a drop; sliding on the skid, rotation on skid, free fall, water entry, ventilation, maximum submergence, resurfacing and the sailing phase. In the sailing phase, the engine is running, providing propeller thrust, and the vessel is exposed to wind and waves while trying to run away from the host. CFD simulations of the lifeboat in the sailing phase have been run in regular Stokes 5th order waves, as well as simulations in irregular seas. The regular waves have been set up with different wave heights and wave periods. The set-up of waves have been done to fulfil the requirements in DNV-OS-E406, which is the DNV-GL offshore standard for design of free fall lifeboats. Validation of the CFD models are done with comparison to model tests from calm water tests as well as self-propelled model tests in waves. Results from full scale tests in calm water and in waves are also used in validation of CFD results. The hydrodynamic problem solved for 3 degrees-of-freedom (DOF) free running model in waves with thrust force from propeller is solved using the CFD software Star CCM+. A method for estimating thrust coefficient with a combination of full scale calm water results and results from CFD simulations is presented. The CFD simulations have shown to give acceptable accuracy for lifeboat in a seaway. Further, the CFD simulations have shown to be very useful for demonstrating fulfilment of requirements in the offshore standard for lifeboats in the sailing phase.

scholarly journals Modeling fires in structures with an atrium in the FDS field model

2018 ◽  
Vol 193 ◽  
pp. 03023 ◽  
Author(s):  
Oleg Nedryshkin ◽  
Marina Gravit ◽  
Kirill Grabovyy
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Fire Safety ◽  
Safety Assessment ◽  
Field Model ◽  
Calculated Data ◽  
Full Scale ◽  
Software System ◽  
Fire Model ◽  
Full Scale Tests

Modeling of dangerous fire factors is an important element in the system of modern fire safety assessment of buildings and structures. The paper presents a comparative analysis of the characteristics of the software system PyroSim. The verification of the fire model in the FDS program, which was performed on the basis of full-scale tests conducted by Professor Chau W.L., was analysed. The analysis of empirical and calculated data on modeling of fire in the atrium is made. The conclusion is made about the accuracy of simulation in the FDS program and the coincidence of the experimental data with the calculated ones.

CFD Modeling of Pulverized Coal Combustion in an Industrial Burner

2012 ◽  
Author(s):  
Marco Torresi ◽  
Bernardo Fortunato ◽  
Sergio Mario Camporeale ◽  
Alessandro Saponaro
Keyword(s):  
Experimental Data ◽  
Coal Combustion ◽  
Three Dimensional ◽  
Full Scale ◽  
Pulverized Coal ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Second Phase ◽  
Pulverized Coal Combustion ◽  
Char Burnout

The accurate prediction of pulverized coal combustion in industrial application still remains a great challenge. This is mainly due to the lack of high quality experimental data acquired during the operation of industrial plants. This work describes the CFD model used in order to numerically simulate the pulverized coal combustion of a full scale, swirl stabilized, aerodynamically staged, industrial burner. In particular, two different combinations of devolatilization and char burnout models were investigated comparing the numerical results with available experimental data obtained during a burner test carried out, in full-scale configuration, in a 50 MWth, fully instrumented, test rig. In order to avoid any unrealistic assumption on pulverized coal distribution at the burner inlet, the entire primary air duct for pulverized coal transportation has been considered. The main flow is computed solving the steady, incompressible, three-dimensional, Reynolds Averaged Navier-Stokes (RANS) equations, whereas the pulverized coal is simulated as a reacting discrete second phase in a Lagrangian frame of reference, computing the trajectories of the discrete phase entities, as well as heat and mass transfer. The numerical analysis confirms the very good burner performance obtained during the tests with a very low percentage of fixed carbon left in the ashes.

Integrating High Purity Oxygen, Process Modeling, and CFD Models for Doubling Treatment Capacity in a Full Scale Leachate Wastewater Treatment

2015 ◽  
Vol 2015 (6) ◽  
pp. 1647-1657
Author(s):  
Malcolm Fabiyi ◽  
Asun Larrea ◽  
Wladimir Sarmiento-Darkin ◽  
Tony Wang ◽  
Simon Ho ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Process Modeling ◽  
High Purity ◽  
Full Scale ◽  
Cfd Models ◽  
Oxygen Process

scholarly journals Performance Prediction of a Hard-Chine Planing Hull by Employing Different CFD Models

2021 ◽  
Vol 9 (5) ◽  
pp. 481
Author(s):  
Azim Hosseini ◽  
Sasan Tavakoli ◽  
Abbas Dashtimanesh ◽  
Prasanta K. Sahoo ◽  
Mihkel Kõrgesaar
Keyword(s):  
Water Flow ◽  
Performance Prediction ◽  
Cfd Modeling ◽  
Computational Time ◽  
Resistance Force ◽  
Stagnation Line ◽  
Mesh Structure ◽  
Cfd Models ◽  
High Speeds ◽  
Des Model

This paper presents CFD (Computational Fluid Dynamics) simulations of the performance of a planing hull in a calm-water condition, aiming to evaluate similarities and differences between results of different CFD models. The key differences between these models are the ways they use to compute the turbulent flow and simulate the motion of the vessel. The planing motion of a vessel on water leads to a strong turbulent fluid flow motion, and the movement of the vessel from its initial position can be relatively significant, which makes the simulation of the problem challenging. Two different frameworks including k-ε and DES (Detached Eddy Simulation) methods are employed to model the turbulence behavior of the fluid motion of the air–water flow around the boat. Vertical motions of the rigid solid body in the fluid domain, which eventually converge to steady linear and angular displacements, are numerically modeled by using two approaches, including morphing and overset techniques. All simulations are performed with a similar mesh structure which allows us to evaluate the differences between results of the applied mesh motions in terms of computation of turbulent air–water flow around the vessel. Through quantitative comparisons, the morphing technique has been seen to result in smaller errors in the prediction of the running trim angle at high speeds. Numerical observations suggest that a DES model can modify the accuracy of the morphing mesh simulations in the prediction of the trim angle, especially at high-speeds. The DES model has been seen to increase the accuracy of the model in the computation of the resistance of the vessel in a high-speed operation, as well. This better level of accuracy in the prediction of resistance is a result of the calculation of the turbulent eddies emerging in the water flow in the downstream zone, which are not captured when a k-ε framework is employed. The morphing approach itself can also increase the accuracy of the resistance prediction. The overset method, however, overpredicts the resistance force. This overprediction is caused by the larger vorticity, computed in the direction of the waves, generated under the bow of the vessel. Furthermore, the overset technique is observed to result in larger hydrodynamic pressure on the stagnation line, which is linked to the greater trim angle, predicted by this approach. The DES model is seen to result in extra-damping of the second and third crests of transom waves as it calculates the stronger eddies in the wake of the boat. Overall, a combination of the morphing and DES models is recommended to be used for CFD modeling of a planing hull at high-speeds. This combined CFD model might be relatively slower in terms of computational time, but it provides a greater level of accuracy in the performance prediction, and can predict the energy damping, developed in the surrounding water. Finally, the results of the present paper demonstrate that a better level of accuracy in the performance prediction of the vessel might also be achieved when an overset mesh motion is used. This can be attained in future by modifying the mesh structure in such a way that vorticity is not overpredicted and the generated eddies, emerging when a DES model is employed, are captured properly.

Investigation of planing craft maneuverability using full-scale tests

2021 ◽  
pp. 147509022110303
Author(s):  
Kazem Sadati ◽  
Hamid Zeraatgar ◽  
Aliasghar Moghaddas
Keyword(s):  
Full Scale ◽  
Performance Characteristics ◽  
Forward Speed ◽  
Speed Reduction ◽  
Planing Craft ◽  
Full Scale Tests ◽  
Turning Maneuver

Maneuverability of planing craft is a complicated hydrodynamic subject that needs more studies to comprehend its characteristics. Planing craft drivers follow a common practice for maneuver of the craft that is fundamentally different from ship’s standards. In situ full-scale tests are normally necessary to understand the maneuverability characteristics of planing craft. In this paper, a study has been conducted to illustrate maneuverability characteristics of planing craft by full-scale tests. Accelerating and turning maneuver tests are conducted on two cases at different forward speeds and rudder angles. In each test, dynamic trim, trajectory, speed, roll of the craft are recorded. The tests are performed in planing mode, semi-planing mode, and transition between planing mode to semi-planing mode to study the effects of the craft forward speed and consequently running attitude on the maneuverability. Analysis of the data reveals that the Steady Turning Diameter (STD) of the planing craft may be as large as 40 L, while it rarely goes beyond 5 L for ships. Results also show that a turning maneuver starting at planing mode might end in semi-planing mode. This transition can remarkably improve the performance characteristics of the planing craft’s maneuverability. Therefore, an alternative practice is proposed instead of the classic turning maneuver. In this practice, the craft traveling in the planing mode is transitioned to the semi-planing mode by forward speed reduction first, and then the turning maneuver is executed.

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