scholarly journals Unsteady RANS CFD Simulations of Sailboat’s Hull and Comparison with Full-Scale Test

2020 ◽  
Vol 8 (6) ◽  
pp. 394 ◽  
Author(s):  
Pietro Casalone ◽  
Oronzo Dell’Edera ◽  
Beatrice Fenu ◽  
Giuseppe Giorgi ◽  
Sergej Antonello Sirigu ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Full Scale ◽  
Navier Stokes ◽  
Hydrodynamic Resistance ◽  
Cfd Simulations ◽  
Unsteady Rans ◽  
Scale Test ◽  
Full Scale Tests ◽  
Substitution Procedure ◽  
Experimental Fluid

The hydrodynamic investigation of a hull’s performance is a key aspect when designing a new prototype, especially when it comes to a competitive/racing environment. This paper purports to perform a fully nonlinear unsteady Reynolds Averaged Navier-Stokes (RANS) simulation to predict the motion and hydrodynamic resistance of a sailboat, thus creating a reliable tool for designing a new hull or refining the design of an existing one. A comprehensive range of speeds is explored, and results are validated with hydrodynamic full-scale tests, conducted in the towing tank facility at University of Naples Federico II, Italy. In particular, this work deals with numerical ventilation, which is a typical issue occurring when modeling a hull; a simple and effective solution is here proposed and investigated, based on the phase-interaction substitution procedure. Results of the computational fluid dynamic (CFD) campaign agree with the experimental fluid dynamic (EFD) within a 2% margin.

Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

2022 ◽  
pp. 147509022110707
Author(s):  
Ugur Can ◽  
Sakir Bal
Keyword(s):  
High Speed ◽  
Full Scale ◽  
Navier Stokes ◽  
Drag Forces ◽  
Fluid Body ◽  
Unsteady Rans ◽  
Lift Forces ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Model Family

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

scholarly journals Full-Scale Tests for Assessing Blasting-Induced Vibration and Noise

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Chung-Won Lee ◽  
Jiseong Kim ◽  
Gi-Chun Kang
Keyword(s):  
Noise Level ◽  
Full Scale ◽  
Noise Prediction ◽  
Square Root ◽  
Infrastructure Development ◽  
Full Scale Test ◽  
Noise Levels ◽  
Tunnel Excavation ◽  
Scale Test ◽  
Full Scale Tests

Vibration and noise problems caused by a number of construction processes, specifically blasting for infrastructure development, are becoming important because of their civil appeal. In this study, a square root equation (SRE) with a 95% confidence level was proposed for predicting blasting-induced vibration through full-scale test blasting, and the vibration value predicted from this equation was located between the values predicted from the USBM (US Department of Interior, Bureau of Mines), NOF (Nippon Oil & Fats Co., Ltd.), and MCT (Ministry of Construction and Transportation) equations. Additionally, by comparing the measured noise level at full-scale test blasting with the calculated noise levels from several noise prediction equations, it was determined that the noise level predicted by the ONECRC equation had the best agreement with the measured results. However, in cases where blasting includes tunnel excavation, simultaneous measurement of vibration and noise is required to prevent damage to the surrounding facilities.

STUDY ON RETROFIT EFFECTS FOR HORIZONTAL PLANE OF TRADITIONAL WOODEN HOUSES BASED ON FULL-SCALE TEST

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
Mitsuhiro Miyamoto ◽  
Haruka Okuhiro
Keyword(s):  
Horizontal Plane ◽  
Pushover Analysis ◽  
Full Scale ◽  
Horizontal Shear ◽  
Full Scale Test ◽  
Analysis Model ◽  
Scale Test ◽  
Full Scale Tests ◽  
Static Pushover Analysis ◽  
Good Agreement

In the present study, few studies have focused on the horizontal plane of traditional wooden houses in Japan. This study aims to examine the retrofit effects for the horizontal plane of traditional wooden houses based on full-scale tests. The first part of this paper is devoted to the experimental study performed to determine the structural behavior and characteristics of full-scale roof specimens. A horizontal shear test was conducted to obtain the fracture mode and relationship between the applied load and deformation angle. The second part deals with a static pushover analysis of the full-scale roof specimens. The results between the experimental test and the static pushover analysis are presented and discussed. The analysis model used for the static pushover analysis is proposed; the results were in good agreement with the tests.

Design of a rotor blade tip for the investigation of dynamic stall in the transonic wind-tunnel Göttingen

2016 ◽  
Vol 120 (1232) ◽  
pp. 1509-1533 ◽  
Author(s):  
B. Lütke ◽  
J. Nuhn ◽  
Y. Govers ◽  
M. Schmidt
Keyword(s):  
Experimental Data ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Fe Model ◽  
Stress Distributions ◽  
Cfd Simulations ◽  
Blade Tip

ABSTRACTThe aerodynamic and structural design of a pitching blade tip with a double-swept planform is presented. The authors demonstrate how high-fidelity finite element (FE) and computational fluid dynamic (CFD) simulations are successfully used in the design phase. Eigenfrequencies, deformation, and stress distributions are evaluated by means of a three-dimensional (3D) FE model. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are compared to experimental data for a light dynamic stall case atMa= 0.5,Re= 1.2 × 106. The results show a very good agreement as long as the flow stays attached. Tendencies for the span-wise location of separation are captured. As soon as separation sets in, discrepancies between experimental and numerical data are observed. The experimental data show that for light dynamic stall cases atMa= 0.5, a factor of safety ofFoS= 2.0 is sufficient if the presented simulation methods are used.

A new methodology for the assessment of the running resistance of trains without knowing the characteristics of the track: Application to full-scale experimental data

2018 ◽  
Vol 232 (6) ◽  
pp. 1814-1827 ◽  
Author(s):  
Claudio Somaschini ◽  
Tommaso Argentini ◽  
Daniele Rocchi ◽  
Paolo Schito ◽  
Gisella Tomasini
Keyword(s):  
High Speed ◽  
High Capacity ◽  
Full Scale ◽  
Design Stage ◽  
Resistance Force ◽  
Full Scale Test ◽  
High Speed Trains ◽  
Scale Test ◽  
Full Scale Tests ◽  
Resistance Coefficients

The resistance to motion of trains is an essential requisite especially while designing high-speed trains and high-capacity railway lines. The optimisation of friction effects and aerodynamic performance can be done during the design stage of a new train but the actual value of the running resistance can be inferred only by means of full-scale tests during the operation of a train. A CEN standard (EN 14067-4) describes the methodologies for the assessment of the running resistance of railway vehicles starting from full-scale test measurements. According to this standard, the speed-dependent terms of the resistance force have to be determined by means of coasting tests on railway lines, whose characteristics must be well known. Since this is not always possible and small errors on the gradient could lead to major uncertainties in the evaluation of the resistance force, a new method for the estimation of the running resistance coefficients, irrespective of the characteristics of the track is proposed in this paper. The reliability of the method is verified by comparing the results with those obtained from the procedure proposed in the CEN standard. The comparison shows that the new methodology is able to evaluate the resistance coefficients with an accuracy equivalent to that of the other methods but with fewer tests and with a more robust procedure relying on a lesser number of parameters.

scholarly journals Aerodynamic study of a suspension bridge deck by CFD simulations, wind tunnel tests and full-scale observations

2021 ◽  
Vol 1201 (1) ◽  
pp. 012007
Author(s):  
I. Kusano ◽  
E. Cheynet ◽  
J. B. Jakobsen ◽  
J. Snæbjörnsson
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Suspension Bridge ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Wide Range

Abstract Assessing the aerodynamic characteristics of long-span bridges is fundamental for their design. Depending on the terrain complexity and local wind conditions, episodes of large angles of attack (AoA) of 15° may be observed. However, such large AoAs ( above 10°) are often overlooked in the design process. This paper studies the aerodynamics properties of a flow around a single-box girder for a wide range of AoAs, from –20° to 20°, using numerical simulations. The simulations are based on a 2D unsteady Reynolds-averaged Navier–Stokes (URANS) approach using the k − ω SST turbulence model with a Reynolds number of 1.6 × 105. Numerically obtained aerodynamic static coefficients were compared to wind tunnel test data. The CFD results were generally in good agreement with the wind tunnel tests, especially for small AoAs and positive AoAs. More discrepancies were observed for large negative AoA, likely due to the limitation of modelling 3D railings with 2D simulations. The simulated velocity deficit downstream of the deck was consistent with the one measured in full-scale using short-range Doppler wind lidar instruments. Finally, the Strouhal number from the CFD simulations were in agreement with the value obtained from the full-scale data.

Pressure Distributions on Sails Investigated Using Three Methods: On-Water Measurements, Wind-Tunnel Measurements, and Computational Fluid Dynamics

2011 ◽  
Author(s):  
Ignazio Maria Viola ◽  
Richard G. J. Flay
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Full Scale ◽  
Navier Stokes ◽  
Pressure Measurements ◽  
Wind Tunnel Tests ◽  
Pressure Distributions ◽  
Unstable Environment ◽  
Full Scale Tests ◽  
Good Agreement

The main results of a two-year project aimed at comparing full-scale tests, wind tunnel tests, and numerical analysis predictions are presented. Pressure measurements were obtained from both full-scale tests and wind-tunnel tests, in upwind and downwind conditions. The upwind wind tunnel test condition was modelled using a Vortex Lattice code, while the downwind wind-tunnel test was modelled using a Navier-Stokes code. The pressures obtained from the three different methods are compared on three horizontal sections of the headsail, mainsail, and asymmetric spinnaker. In general the pressures from the three experiments showed good agreement. In particular, very good agreement was obtained between the numerical computations and the wind tunnel test results. Conversely, the results from the downwind full-scale pressure measurements showed less similarity due to a slightly tightened trim being used for the spinnaker in the on-water tests. Full-scale tests allow the action of unsteadiness due to the wind, wave and yacht movements to affect the results. This unstable environment caused the asymmetric spinnaker to move around, and a tightened trim was required to prevent the spinnaker from collapsing.

Performance Analysis of Multi-Sectional Cycloidal Hydrokinetic Turbines

2021 ◽  
Author(s):  
Ang Li ◽  
Yijie Wang ◽  
Jun Chen ◽  
Greg Jensen ◽  
Haiyan Zhang
Keyword(s):  
Fluid Dynamic ◽  
Power Coefficient ◽  
Cfd Simulations ◽  
Hydrokinetic Turbines ◽  
Turbine Efficiency ◽  
Reliable Source ◽  
Sliding Interfaces ◽  
Water Turbine ◽  
Unsteady Rans ◽  
The One

Abstract Hydrokinetic power is the most efficient and reliable source of renewable energy and it has been utilized to produce power for centuries. The cycloidal water turbine is a subset of the H-bar type Darrieus turbines that are designed to actively controls the pitch angle of blades to improve turbine efficiency. However, the traditional cycloidal turbine has some shortcomings. For example, the torque and power coefficient vary significantly as the turbine rotates, which means the produced power is not uniform in one revolution. The associated hydrodynamic load will lead to fatigue of the turbine structure that will shorten the turbine lifespan. To solve this problem, a concept of the multi-sectional cycloidal water turbine is proposed. In the present study, computational fluid dynamic (CFD) simulations are applied to investigate the performance of the multi-sectional cycloidal turbine. A cycloidal turbine with three identical sections is designed. Each section consists of three blades and NACA0021 is chosen as the hydrofoil. Structured mesh with sliding interfaces is generated and arbitrary Mesh Interface (AMI) technique is employed. Unsteady RANS simulations with SST k–ω model are conducted to compute the flow field and torque generated by the turbine, and then power coefficient is computed. The results demonstrates that the three-section turbine has uniform performance in one revolution. At the design condition, the power coefficients of the one-section turbine and the three-section turbine are similar; when the TSR is much larger or less than the desired value, the three-section turbine has better performance.

The Design and Application of Shear Fracture Propagation Studies

1974 ◽  
Vol 96 (4) ◽  
pp. 323-329 ◽  
Author(s):  
W. A. Poynton ◽  
R. W. E. Shannon ◽  
G. D. Fearnehough
Keyword(s):  
Thermodynamic Equilibrium ◽  
Constant Velocity ◽  
Shear Fracture ◽  
Fracture Propagation ◽  
Full Scale ◽  
Full Scale Test ◽  
Test Behavior ◽  
Scale Test ◽  
Full Scale Tests ◽  
Fracture Arrest

Shear fracture propagation is studied using an analysis based upon the thermodynamic equilibrium of a constant velocity fracture. This equation is shown to describe the behavior of all full scale tests which exhibit constant velocity propagation. This equation is developed to identify the conditions for fracture arrest; the resulting formulation is again consistent with full scale test behavior. The paper also discusses the application of the theory to existing and new pipelines.

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.

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