NUMERICAL ANALYSES OF OPENFOAM'S OVERTOPPING DEVICE SOLUTION

Studies related to ocean energy are getting more important lately, once world claims for renewable energy usage. The Overtopping Device is a kind of Ocean Waves Energy Converter (OWEC), which main concept is storing water provided by incident waves above sea level to feed a set of low head turbines. In order to obtain the desired effect, this device contains a ramp which elevates the incident waves toward the reservoir. Present study aims to perform a numerical model of a 2D Overtopping Device by means of OpenFOAM simulations. OpenFOAM is a free open source code which has shown applicability in many areas of engineering. The adopted solver (InterFOAM) is Volume of Fluid based (VOF) according to Finite Volume Method (FVM), these methodologies has been largely used among researchers in propagating waves field. FLUENT (commercial code) is used to verify OpenFOAM's results. Once, the main point of this paper is to present OpenFOAM as a considerable tool for propagating waves studies, it firstly presents a numerical wave verification with analytical solutions (second order Stokes theory). The second section of results presents overtopping time series peaks in 100 s of simulation. Also, by mass flow rate integration, it presents total mas of water climbed to the reservoir. The integration of mass flow rate takes 94 s of simulation (not 100 s) because it is noticeable a pause between two peaks of overtopping at that time. Results show agreement between wave elevation and wave velocity profiles with straight convergence of periods between analytical and numerical waves. Most important differences are found near air/water interface, owed to faster air flow at that region. Generally OpenFOAM and FLUENT results are similar, with converged overtopping time series peaks and their magnitudes too. Similarly, the amount of water marked by both software are close with very similar trend lines.

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The Effects of Tip Clearance on Performance of a Heavy Duty Multi Stages Axial Turbine

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-69553 ◽

2012 ◽

Cited By ~ 1

Author(s):

Mohammad Reza Shirzadi ◽

Hossein Saeidi

Keyword(s):

Pressure Drop ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Large Scale ◽

Tip Clearance ◽

Heavy Duty ◽

Penetration Length ◽

Axial Turbine ◽

Commercial Code

In this article aerodynamic effects of tip clearance on a heavy duty axial turbine are studied. Three different tip clearances are considered for each rotor. For simplicity, a simple tip profile is assumed and cooling air is not modeled. Aerodynamic behavior of all stages is studied in terms of polytropic efficiency, leakage mass flow, secondary and total losses, penetration length, and total mass flow rate for different pressure ratios. Also three well established correlations of tip clearance loss are compared with CFD results to obtain the best model for performance calculation of such a large-scale turbine. The steady states, viscous and compressible flow governing equations representing the flow field with k-epsilon turbulence model are solved using commercial code ANSYS CFX.12. Useful data are presented to predict the variation of efficiency of each individual rotor, as well as entire turbine, as a function of relative tip gap (k/h). This information may be useable in design and troubleshooting. According to the results, even though pressure drop in rear stages across tip gap is lower than pressure drop in front stages, leakage mass flow rate is considerably high for this LP stages. Consequently, tip clearance losses of rear stages have significant effect on the entire turbine efficiency.

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EXPERIMENTAL AND NUMERICAL INVESTIGATION OF METASTABLE FLOW OF REFRIGERANT R-22 THROUGH CAPILLARY TUBE

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING ◽

10.32852/iqjfmme.vol18.iss1.72 ◽

2018 ◽

Vol 18 (1) ◽

pp. 41-62

Author(s):

Esam M Abed ◽

Ammar A K Fathi

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Capillary Tube ◽

Numerical Data ◽

Design And Optimization ◽

Metastable Region ◽

Ansys Cfx ◽

Commercial Code ◽

Suction Line

This study presents an experimental investigation of metastable region take place forrefrigerant flow through adiabatic and non-adiabatic capillary tube of window type airconditioner. Large numbers of experiments are carried out to explain the effect of length ofstraight and helical capillary tube on metastable region under adiabatic and non-adiabaticconditions. for the case of adiabatic capillary tube, three different length are selected(70,100 and 150) cm and two helical capillary tube, the length of each tube is 100 cm withtwo coil diameters (2 and 6) cm. For the non-adiabatic capillary tube, the straight capillarytube suction line is 150 cm while the length of non-adiabatic helical capillary tube is 200 cmwith 8 cm coil diameter. The results show that the length is the most influence parameterson beginning of metastable region. In addition the helical coil tube effect on the beginningof metastable region. As well as for the adiabatic and non-adiabatic capillary tube it isconcluded that mass flow rate is the main parameters on beginning of metastable region.Also effect of length and coiling on both pressure drop and mass flow rate are discussed.The CFD commercial code, ANSYS CFX 16.1 based on finite volume method using Kturbulencemodel considering the homogeneous flow between phases applied to straightcapillary tube. The present numerical data has been validated with the present workexperimental data and with other researchers. A good agreement is obtained which can belead to use ANSYS CFX 16.1 in the design and optimization of capillary tube in airconditioner.

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Measurement of Unsteady Pressure Field in a Turbocharger Compressor Using Pressure-Sensitive Paint

Volume 2B: Turbomachinery ◽

10.1115/gt2018-76267 ◽

2018 ◽

Cited By ~ 1

Author(s):

Takaaki Kitamura ◽

Masaharu Kameda ◽

Wataru Watanabe ◽

Kazutaka Horimoto ◽

Kenta Akimoto ◽

...

Keyword(s):

Time Series ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Pressure Field ◽

Operating Conditions ◽

Series Data ◽

Pressure Sensitive Paint ◽

Unsteady Pressure ◽

Pressure Sensitive

It is necessary to quantitatively resolve the flow field generated in compressors at various operating conditions including the surge. In this study, fast-responding pressure-sensitive-paint (PSP) and temperature-sensitive-paint (TSP) was applied to measurement of steady and unsteady pressure and temperature fields in a turbocharger compressor. The surface pressure of a compressor impeller and the diffuser downstream of the impeller was measured under the rotating speed of 133,000 rpm with various mass flow rate of the inlet. Blue LED strobes were used as the excitation light source for PSP/TSP. The luminescence from PSP/TSP were captured by a high-speed camera. These instruments were controlled using the signal synchronized with a fixed rotation angle of the impeller, which was detected using a gap sensor installed near the impeller. The pressure was calculated from the time-series of the PSP signal. The output of PSP/TSP was compared with the signal from semiconductor pressure transducers and the thermal image taken by an infrared camera. For the analysis of the diffuser, the power spectra of the pressure field were obtained using the fast Fourier transform of the time-series data of the pressure fluctuation. The pressure field on the impeller was successfully obtained with the aid of adequate temperature compensation by TSP. It was confirmed that the time-averaged pressure on the impeller blades increased as the inlet mass flow rate was decreased. Large-amplitude points were distributed on the extension line of the impeller blades in the diffuser when the surge occurs.

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Computational Modeling of Flow Rate Measurements Using an Orifice Flow Meter

Volume 2: Development and Applications in Computational Fluid Dynamics; Industrial and Environmental Applications of Fluid Mechanics; Fluid Measurement and Instrumentation; Cavitation and Phase Change ◽

10.1115/fedsm2018-83296 ◽

2018 ◽

Cited By ~ 1

Author(s):

YiQin Xu ◽

Daniel Coxe ◽

Yulia Peet ◽

Taewoo Lee

Keyword(s):

Measurement Uncertainty ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Rate Measurement ◽

Flow Rate Measurement ◽

Flow Meters ◽

Commercial Code ◽

Orifice Flow ◽

Orifice Flow Meter

This study is concerned with understanding and improvement of mass flow rate measurement uncertainty and errors encountered at low flow rates and start-up in commercially available flow rate measurement devices, such as orifice flow meters. The flow through a typical cylindrical flange-tapped orifice flow meter is modeled computationally so the actual mass flow rate is known a-priori. Empirical predictions from the reading of “virtual” pressure sensors are compared with the actual flow rate and the measurement errors are quantified and analyzed. Commercial code ANSYS-Fluent is compared in this study to the in-house high-fidelity spectral-element solver Nek5000, so that conclusions about the applicability of a commercial code to the calculations of measurement uncertainty in the orifice flow meters can be made.

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Numerical Study on Gaseous CO2 Leakage and Thermal Characteristics of Containers in a Transport Ship

Applied Sciences ◽

10.3390/app9122536 ◽

2019 ◽

Vol 9 (12) ◽

pp. 2536

Author(s):

Dae Yun Kim ◽

Chan Ho Jeong ◽

Beom Jin Park ◽

Min Suk Ki ◽

Myung-Soo Shin ◽

...

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Numerical Study ◽

Effective Area ◽

Confined Space ◽

Co2 Leakage ◽

Cfd Simulations ◽

Commercial Code ◽

Transport Ship

This study investigates numerically gaseous CO2 leakage characteristics inside the containers of a transport ship and examines thermal effects on the structural damage that might happen in the containers. First, with consideration of the phase change, the ejected mass flow rate was estimated using the commercial code of DNV PHAST. Based on this estimated mass flow rate, we introduced an effective area model for accounting for the fast evaporation of liquefied CO2 occurring in the vicinity of a crack hole. Using this leakage modeling, along with a concept of the effective area, the computational fluid dynamics (CFD) simulations for analyzing transient three-dimensional characteristics of gas propagation in a confined space with nine containers, as well as the thermal effect on the walls on which the leaking gas impinges, were conducted. The commercial code, ANSYS FLUENT V. 17.0, was used for all CFD simulations. It was found that there are substantial changes in the pressure and temperature of the gas mixture for different crack sizes. The CO2 concentration at human nasal height, a measure of clear height for safety, was also estimated to be higher than the safety threshold of 10% within 200 s. Moreover, very cold gas created by the evaporation of liquefied CO2 can cool the cargo walls rapidly, which might cause thermal damage.

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