Hydroelastic Responses of a Flexible Hydrofoil in Turbulent, Cavitating Flow

2010 ◽  
Author(s):  
Antoine Ducoin ◽  
Yin Lu Young ◽  
Jean-Franc¸ois Sigrist
Keyword(s):  
Degrees Of Freedom ◽  
Experimental Studies ◽  
Cavitating Flow ◽  
Experimental Measurements ◽  
Naval Academy ◽  
Loosely Coupled ◽  
Numerical Predictions ◽  
Computational Fluid Dynamics Cfd ◽  
Lift And Drag ◽  
Twisting Deformation

The objective of this work is to develop and validate a robust method to simulate the hydroelastic responses of flexible hydrofoil in turbulent, cavitating flow. A two degrees-of-freedom (2-DOF) model is used to simulate the plunging and pitching motion at the foil tip due to bending and twisting deformation of a 3-D cantilevered hydrofoil. The 2-DOF model is loosely coupled with the commercial computational fluid dynamics (CFD) solver STAR-CCM+ to efficiently simulate the fluid-structure interaction (FSI) responses of a cantilevered, rectangular hydrofoil. The numerical predictions are compared with experimental measurements for cases with and without cavitation. The experimental studies were conducted in the cavitation tunnel at the French Naval Academy (IRENav), France. Only quasi-steady cases with Reynolds number (Re) of 750,000 are shown in this paper. In general, the numerical results agree well with the experimental measurements and observations. The results show that elastic deformation of the POM polyacetate (flexible) hydrofoil lead to increases in the angle of attack, which resulted in higher lift and drag coefficients, lower lift to drag ratio, and longer cavities compared to the stainless steel (rigid) hydrofoil. Whereas only stable cavitation cases are considered in this paper, significant interaction effects were observed during experiments for cases with unstable cavitation due to interations between the foil natural frequencies and the cavity shedding frequencies. Transient analysis of the FSI responses of 3-D elastic hydrofoils in turbulent, cavitating flow is currently under work.

Scaling of the Hydroelastic Response of Flexible Lifting Bodies in Transitional and Turbulent Flows

2013 ◽  
Author(s):  
Antoine Ducoin ◽  
Yin Lu Young
Keyword(s):  
Turbulent Flows ◽  
Degrees Of Freedom ◽  
Experimental Studies ◽  
Full Scale ◽  
Stress Distributions ◽  
Viscous Effects ◽  
Scaling Methods ◽  
Fluid Properties ◽  
Computational Fluid Dynamics Cfd ◽  
Hydroelastic Response

The objective of this research is to derive and validate scaling relationships for flexible lifting bodies in transitional and turbulent flows. The motivation is to help the design and interpretation of reduced-scale experimental studies of flexible hydrofoils, with focus on the influence of viscous effects on the hydroelastic response. The numerical method is based on a previous validated viscous FSI solver presented in [1]. It is based on the coupling between a commercial Computational Fluid Dynamics (CFD) solver, CFX, and a simple two-degrees-of-freedom (2-DOF) system that simulates the free tip section displacement of a cantilevered, rectangular hydrofoil. To validate the scaling relations, sample numerical results are shown for three geometrically similar models: full scale, 1/2 scale and 1/10 scale. On the fluid side, although the effects of gravity and compressibility are assumed to be negligible, three different methods of scaling the velocity are considered: Reynolds scaling, Froude scaling, and Mach scaling. The three scaling methods produce different velocity scales when the fluid properties and gravitational constant are the same between the model and prototype, which will lead to different scaling for the material properties. The results suggest that by applying Mach scaling (which does not mean the flow is compressible, but simply requires the relative inflow velocity and fluid properties to be the same between the model and the prototype) and Re ≥ 2 × 106, the same material as the full scale could be used, which will lead to similar stress distributions, in addition to similar strains, and hence similar hydroelastic response and failure mechanisms. However, if Re ≤ 2 × 106 and Mach scale is used, a viscous correction is required to properly extrapolate the experimental results to full-scale.

Experimental Measurements and Theoretical Predictions of the Thermohydraulic Performance of Clean Rooms for the Semi-Conductor Industry

1996 ◽  
Vol 210 (1) ◽  
pp. 9-18 ◽  
Author(s):  
G L Quarini ◽  
Y C Chang
Keyword(s):  
Food Processing ◽  
Semiconductor Manufacturing ◽  
Ventilation System ◽  
Experimental Measurements ◽  
Clean Room ◽  
Mean Flow ◽  
Numerical Predictions ◽  
Theoretical Predictions ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

There is a need to engineer working areas where air-borne pollution is below specified limits. This need arises from activities as diverse as food processing, semi-conductor manufacture and surgery. In this paper, detailed experimental measurements of flows in a semiconductor manufacturing room are reported. Computational fluid dynamics (CFD) has been used to study the flows within the room. Good agreement was found between the measured and predicted mean flow velocity distributions. Both the experimental measurements and the numerical predictions suggest that the ventilation system used in this room, which is of a common industrial design, does not produce ideal clean room conditions.

scholarly journals Comparative Study for the Prediction of Cavitating Flow inside a Square-Edged Orifice using Different Commercial CFD Software

2019 ◽  
Vol 128 ◽  
pp. 06003
Author(s):  
Gong-Hee Lee ◽  
June-Ho Bae
Keyword(s):  
Structural Damage ◽  
Nuclear Power ◽  
Cavitating Flow ◽  
Regulatory Body ◽  
Reactor Operation ◽  
Flow Acceleration ◽  
Service Testing ◽  
Ansys Cfx ◽  
Rapid Flow ◽  
Computational Fluid Dynamics Cfd

Nuclear power plant operators conduct in-service testing (IST) to verify the safety functions of safety–related pumps and valves and to monitor the degree of vulnerability over time during reactor operation. The system to which the pump and valve to be tested are installed has various sizes of orificesfor flow control and decompression. Rapid flow acceleration and accompanying pressure drop may cause cavitation inside the orifice, which may result in orifice degradation and structural damage. Though licensing applications supported by using Computational Fluid Dynamics (CFD) software are gradually increasing for IST–related problems, there is no CFD software which obtains a licensing from the domestic regulatory body until now. In this paper, to assess the prediction performance of different commercialCFD software for the analysis of cavitating flow inside a square–edged orifice, the simulation was conducted with ANSYS CFX and FLUENT R18.1. The results predicted were then compared with the measured data.

An Appraisal of the Paper by O'Carrol et al. (1990)

1995 ◽  
Vol 209 (3) ◽  
pp. 203-205 ◽  
Author(s):  
A Strozzi ◽  
A Unsworth
Keyword(s):  
Finite Element ◽  
Finite Elasticity ◽  
Experimental Measurements ◽  
Linear Elastic ◽  
Numerical Predictions ◽  
Elasticity Effects

The paper by O'Carrol et al. (1), which addresses the problem of an elastomeric disc indented by a spherical punch, has been evaluated. The sources of disagreement between linear elastic numerical predictions and experimental measurements noted in this paper have been critically examined in the light of finite element forecasts obtained with a package which incorporates finite elasticity effects and incompressibility.

scholarly journals Three-Dimensional Navier–Stokes Analysis and Redesign of an Imbedded Bellmouth Nozzle in a Turbine Cascade Inlet Section

1996 ◽  
Vol 118 (3) ◽  
pp. 529-535 ◽  
Author(s):  
P. W. Giel ◽  
J. R. Sirbaugh ◽  
I. Lopez ◽  
G. J. Van Fossen
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Inlet Section ◽  
Turbine Cascade ◽  
Blade Cascade ◽  
Inlet Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Transonic Turbine ◽  
Flow Nonuniformity

Experimental measurements in the inlet of a transonic turbine blade cascade showed unacceptable pitchwise flow nonuniformity. A three-dimensional, Navier–Stokes computational fluid dynamics (CFD) analysis of the imbedded bellmouth inlet in the facility was performed to identify and eliminate the source of the flow nonuniformity. The blockage and acceleration effects of the blades were accounted for by specifying a periodic static pressure exit condition interpolated from a separate three-dimensional Navier–Stokes CFD solution of flow around a single blade in an infinite cascade. Calculations of the original inlet geometry showed total pressure loss regions consistent in strength and location to experimental measurements. The results indicate that the distortions were caused by a pair of streamwise vortices that originated as a result of the interaction of the flow with the imbedded bellmouth. Computations were performed for an inlet geometry that eliminated the imbedded bellmouth by bridging the region between it and the upstream wall. This analysis indicated that eliminating the imbedded bellmouth nozzle also eliminates the pair of vortices, resulting in a flow with much greater pitchwise uniformity. Measurements taken with an installed redesigned inlet verify that the flow nonuniformity has indeed been eliminated.

scholarly journals Model Calibration for a Rigid Hexapod-Based End-Effector with Integrated Force Sensors

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3537
Author(s):  
Christian Friedrich ◽  
Steffen Ihlenfeldt
Keyword(s):  
Parameter Identification ◽  
Degrees Of Freedom ◽  
Force Measurement ◽  
Experimental Studies ◽  
Measurement Model ◽  
Calibration Procedure ◽  
Force Sensors ◽  
End Effector ◽  
Measurement Models ◽  
Fast Procedure

Integrated single-axis force sensors allow an accurate and cost-efficient force measurement in 6 degrees of freedom for hexapod structures and kinematics. Depending on the sensor placement, the measurement is affected by internal forces that need to be compensated for by a measurement model. Since the parameters of the model can change during machine usage, a fast and easy calibration procedure is requested. This work studies parameter identification procedures for force measurement models on the example of a rigid hexapod-based end-effector. First, measurement and identification models are presented and parameter sensitivities are analysed. Next, two excitation strategies are applied and discussed: identification from quasi-static poses and identification from accelerated continuous trajectories. Both poses and trajectories are optimized by different criteria and evaluated in comparison. Finally, the procedures are validated by experimental studies with reference payloads. In conclusion, both strategies allow accurate parameter identification within a fast procedure in an operational machine state.

Experimental Studies of Adiabatic Flow Boiling in Fractal-Like Branching Micro-Channels

2008 ◽  
Author(s):  
Brian J. Daniels ◽  
James A. Liburdy ◽  
Deborah V. Pence
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Channel Length ◽  
Channel Height ◽  
Channel Network ◽  
Adiabatic Flow ◽  
Numerical Predictions ◽  
Micro Channels

Experimental results of adiabatic boiling of water flowing through a fractal-like branching microchannel network are presented and compared to numerical simulations for identical flow conditions. The fractal-like branching channel network had channel length and width ratios between adjacent branching levels of 0.7071, a total flow length of 18 mm, a channel height of 150 μm and a terminal channel width of 100 μm. The channels were DRIE etched into a silicon disk and pyrex was anodically bonded to the silicon to form the channel top and allowed visualization of the flow within the channels. The water flowed from the center of the disk where the inlet was laser cut through the silicon to the periphery of the disc. The flow rates ranged from 100 to 225 g/min and the inlet subcooling levels varied from 0.5 to 6 °C. Pressure drop across the channel as well as void fraction in each branching level were measured for each of the test conditions. The measured pressure drop ranged from 20 to 90 kPa, and the measured void fraction ranged from 0.3 to 0.9. The pressure drop results agree well with the numerical predictions. The measured void fraction results followed the same trends as the numerical results.

scholarly journals Impact of Turbulence Models on the Air Flow in a Confined Rectangular Space

2020 ◽  
pp. 46-53
Author(s):  
Jakub Mularski ◽  
Amit Arora ◽  
Muhammad Azam Saeed ◽  
Łukasz Niedźwiecki ◽  
Samrand Saeidi
Keyword(s):  
Experimental Data ◽  
Air Flow ◽  
Turbulence Models ◽  
The Other ◽  
Experimental Measurements ◽  
Wall Region ◽  
Sst Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
The Given

The paper regards the impact of four different turbulence models on the air flow pattern in a confined rectangular space. The following approaches are analyzed. The Baseline (BSL) Reynolds model, the Speziale-Sarkar-Gatzki (SSG) Reynolds model, the Menter's shear-stress transport (SST) model and the basic k-ε model. Computational fluid dynamics (CFD) results are compared with the experimental measurements in four different planes. The Reynolds number for the given conditions is equal to 5000. The k-ε model yielded the most accurate results with regard to the experimental data but its reliability decreased near the wall region. With respect to the other models, it was also found that the k-ε approach generated the least circulating flow.

APPLICATION OF THE FINITE STRIP METHOD TO MODELING OF VIBRATIONS OF COLLECTING ELECTRODES

2013 ◽  
Vol 13 (07) ◽  
pp. 1340001 ◽  
Author(s):  
IWONA ADAMIEC-WÓJCIK ◽  
ANDRZEJ NOWAK ◽  
STANISŁAW WOJCIECH
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Geometrical Parameters ◽  
Experimental Measurements ◽  
Newmark Method ◽  
Algebraic Equations ◽  
Finite Strip ◽  
Strip Method ◽  
Finite Strip Method ◽  
Large Length

The paper presents an application of the finite strip method to modeling of vibrations of the collecting electrodes, which are shells with large length (up to 16 m), width of 0.5 m and thickness of 0.002 m. The models and computer programs have been worked out and validated. Comparison of results obtained from numerical simulations and experimental measurements are presented and discussed. The equations of motion have been solved using methods for solution of sparse algebraic equations and Newmark method. The strip method has proved to be numerically effective. The programs enable us to carry out calculations for a system with several hundred thousands of degrees of freedom with time of analysis requiring thousand integration steps during less than 90 min on a PC computer. High numerical efficiency enables the geometrical parameters of the collecting electrodes to be selected in order to ensure large accelerations caused by a beater to be spread evenly over the surface of the electrodes. Conclusions concerning the influence of length of the collecting electrodes on the normal and tangentz accelerations are formulated.

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