Acoustoelastic Interaction in Combustion Chambers: Modeling and Experiments

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
R. A. Huls ◽  
J. F. van Kampen ◽  
P. J. M. van der Hoogt ◽  
J. B. W. Kok ◽  
A. de Boer
Keyword(s):  
Cfd Simulation ◽  
Pressure Sensors ◽  
Structural Vibration ◽  
Navier Stokes ◽  
Laser Vibrometer ◽  
Combustion Chambers ◽  
Lean Premixed Combustion ◽  
Frequency Independent ◽  
Modeling And Experiments ◽  
Computational Fluid Dynamics Cfd

To decrease NOx emissions from combustion systems, lean premixed combustion is used. A disadvantage is the higher sensitivity to combustion instabilities, leading to increased sound pressure levels in the combustor and resulting in an increased excitation of the surrounding structure: the liner. This causes fatigue, which limits the lifetime of the combustor. This paper presents a joint experimental and numerical investigation of this acoustoelastic interaction problem for frequencies up to 1kHz. To study this problem experimentally, a test setup has been built consisting of a single burner, 500kW, 5bar combustion system. The thin structure (liner) is contained in a thick pressure vessel with optical access for a traversing laser vibrometer system to measure the vibration levels of the liner. The acoustic excitation of the liner is measured using pressure sensors measuring the acoustic pressures inside the combustion chamber. For the numerical model, the finite element method with full coupling between structural vibration and acoustics is used. The flame is modeled as an acoustic volume source corresponding to a heat release rate that is frequency independent. The temperature distribution is taken from a Reynolds averaged Navier Stokes (RaNS) computational fluid dynamics (CFD) simulation. Results show very good agreement between predicted and measured acoustic pressure levels. The predicted and measured vibration levels also match fairly well.

A Verification and Validation Study of CFD Simulation of Wind-Induced Ventilation on Building with Single-Sided Opening

2014 ◽  
Vol 554 ◽  
pp. 696-700 ◽  
Author(s):  
Nur Farhana Mohamad Kasim ◽  
Sheikh Ahmad Zaki ◽  
Mohamed Sukri Mat Ali ◽  
Ahmad Faiz Mohammad ◽  
Azli Abd Razak
Keyword(s):  
Open Source Software ◽  
Natural Ventilation ◽  
Cfd Simulation ◽  
Previous Experiment ◽  
Experimental Methods ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Computational Fluid Dynamics Cfd ◽  
Model Approach

Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.

Numerical Modeling of Static and Rotordynamic Characteristics for Three Types of Helically Grooved Liquid Annular Seals

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Zhigang Li ◽  
Zhi Fang ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Perturbation Method ◽  
Navier Stokes ◽  
Force Coefficients ◽  
Numerical Predictions ◽  
Curve Fit ◽  
Annular Seal ◽  
Frequency Independent ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Reference ◽  
Annular Seals

Abstract This paper deals with numerical predictions of the leakage flowrates, drag power, and rotordynamic force coefficients for three types of helically grooved liquid annular seals, which include a liquid annular seal with helically grooved stator (GS/SR seal), one with helically grooved rotor (SS/GR seal), and one with helical grooves on stator and rotor (GS/GR seal). A novel transient computational fluid dynamics (CFD)-based perturbation method was proposed for the predictions of the leakage flowrates, drag power, and rotordynamic force coefficients of helically grooved liquid annular seals. This method is based on the unsteady Reynolds-averaged Navier–Stokes (RANS) solution with the mesh-deformation technique and the multiple reference frame theory. The time-varying fluid-induced forces acting on the rotor/stator surface were obtained as a response to the time-dependent perturbation of the seal stator surface with the periodic motion, based on the multiple-frequency elliptical-orbit stator whirling model. The frequency-independent rotordynamic force coefficients were determined using curve fit and fast Fourier transform (FFT) in the frequency domain. The CFD-based method was adequately validated by comparisons with the published experiment data of leakage flowrates and fluid response forces for three types of helically grooved liquid annular seals. Based on the transient CFD-based perturbation method, numerical results of the leakage flowrates, drag powers, and rotordynamic force coefficients were presented and compared for three types of helically grooved liquid annular seals at five rotational speeds (n = 0.5 krpm, 1.0 krpm, 2.0 krpm, 3.0 krpm, and 4.0 krpm), paying special attention to the effective stiffness coefficient and effective damping coefficient.

CFD Simulation of Propeller and Tunnel Thruster Performance

2014 ◽  
Author(s):  
Ping Lu ◽  
Sue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Open Water ◽  
Ship Hull ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Computational Domain ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Drag And Lift

In the present study, the hydrodynamic performance of a typical North Sea dynamic positioning (DP) shuttle tanker consisting of two main propellers, two rudders, and two bow tunnel thrusters is investigated by solving Reynolds-averaged Navier-Stokes (RANS) equations for a viscous flow. The focus of the numerical simulation is on the performance of propellers/rudders and bow tunnel thrusters considering the hydrodynamic interactions between propellers/thrusters, hull and current. The numerical model includes hull, propeller, rudder, bow tunnel thruster and flow field. First, an analysis of a propeller performance in open water is carried out by calculating the coefficient of thrust, torque, and propeller efficiency. Then, rudders are included in the analysis for the assessment of propeller/rudder performance. The pressure distribution on rudders, rudder’s drag and lift coefficients for different angles of attack, and flow field around the rudder are obtained. The interaction effects between propeller, rudder, ship hull, as well as bow tunnel thruster and ship hull are analyzed by adding detailed ship hull geometry in the computational domain. The tunnel thruster efficiency reduction due to current and ventilation is also analyzed. The presence of current leads to significant changes in the flow velocity and distribution of pressure in the tunnel outflow area as well as significant deflection of the propeller jet emitting from the tunnel. A comparison between Computational Fluid Dynamics (CFD) and model test results of flow features near the tunnel area with various current speeds is presented.

scholarly journals The Efficient Application of an Impulse Source Wavemaker to CFD Simulations

2019 ◽  
Author(s):  
Pál Schmitt ◽  
Christian Windt ◽  
Josh Davidson ◽  
John V. Ringwood ◽  
Trevor Whittaker
Keyword(s):  
Shallow Water ◽  
Source Function ◽  
Cfd Simulation ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Wide Range ◽  
Rans Models ◽  
Hydrodynamic Processes ◽  
Computational Fluid Dynamics Cfd ◽  
Shallow Water Models

Computational Fluid Dynamics (CFD) simulations, based on Reynolds Averaged Navier Stokes (RANS) models, are a useful tool for a wide range of coastal and offshore applications, providing a high fidelity representation of the underlying hydrodynamic processes. Generating input waves in the CFD simulation is performed by a numerical wavemaker (NWM), with a variety of different NWM methods existing for this task. While NWMs, based on impulse source methods, have been widely applied for wave generation in depth averaged, shallow water models, they have not seen the same level of adoption in the more general RANS based CFD simulations, due to difficulties in relating the required impulse source function to the resulting free surface elevation for non-shallow water cases. This paper presents an implementation of an impulse source wavemaker, which is able to self-calibrate the impulse source function to produce a desired wave series in deep or shallow water at a specific point in time and space. Example applications are presented, for a numerical wave tank (NWT), based on the opensource CFD software OpenFOAM, for wave packets in deep and shallow water, highlighting the correct calibration of phase and amplitude. Also, the suitability for cases requiring very low reflection from NWT boundaries is demonstrated. Possible issues in the use of the method are discussed and guidance for good application is given.

scholarly journals VERIFICATION OF SCHRENK METHOD FOR WING LOADING ANALYSIS OF SMALL UNMANNED AIRCRAFT USING NAVIERSTOKES BASED CFD SIMULATION

2018 ◽  
Vol 15 (2) ◽  
pp. 161 ◽  
Author(s):  
Arifin Rasyadi Soemaryanto ◽  
Nurhayyan Halim Rosid
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Approximation Method ◽  
Cfd Simulation ◽  
Unmanned Aircraft ◽  
Navier Stokes ◽  
Aerodynamic Load ◽  
Wing Loading ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Prediction of an aerodynamic load acting on a wing or usually called wing loading becomes an important stage for structural analysis. Several methods have been used in estimating the wing loading. Schrenk approximation method is commonly used to achieve the fast estimation of lift distribution along wingspan, but in order to achieve a high level accuracy of aerodynamic prediction, computational fluid dynamics (CFD) with Navier Stokes-based equation can be used. LAPAN Surveillance UAV (LSU series) has been chosen to represent an aerodynamics analysis on generic small unmanned aircraft with twinboom vertical stabilizer configuration. This study was focused to verify the Schrenk approximation method using high accuracy numerical simulation (CFD). The goal of this study was to determine the lift distribution along wingspan and a number of errors between Schrenk approximation and CFD method. In this study, Schrenk approximation result showed similarity with the CFX simulation. So the two results have been verified in analysis of wing loading. ABSTRAKPrediksi dari beban aerodinamika yang terjadi pada sayap menjadi salah satu tahap yang penting dalam analisis struktur perancangan pesawat. Beberapa metode telah digunakan untuk mengestimasi besarnya beban aerodinamika pada sayap. Metode Schrenk umum digunakan untuk estimasi cepat perhitungan besar distribusi gaya angkat di sepanjang sayap. Guna mencapai tingkat akurasi yang tinggi dari prediksi aerodinamika, simulasi Computational Fluid Dynamics (CFD) dengan berbasis persamaan Navier-Stokes dapat digunakan. Pesawat nirawak LSU dipilih untuk merepresentasikan analisis aerodinamika pada pesawat nirawak dengan konfigurasi twin-tailboom pusher. Fokus dari studi yang dilakukan adalah untuk memverifikasi dari metode pendekatan dari Schrenk dengan menggunakan metode yang memiliki akurasi tinggi seperti simulasi CFD. Tujuan dari studi adalah untuk menghitung distribusi gaya angkat sepanjang sayap dan menentukan seberapa besar error dari kedua metode.

Scale Effects on Ship Maneuverability Using RANS

2018 ◽  
Author(s):  
Motoki Araki
Keyword(s):  
Cfd Simulation ◽  
Scale Effects ◽  
Full Scale ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Ship Maneuvering ◽  
Ship Maneuverability ◽  
Computational Fluid Dynamics Cfd ◽  
Rudder Angle ◽  
Maneuvering Simulations

Predicting ship maneuverability is one of the important topics in ship engineering. However because of the huge difference between model and full scale Reynolds number (Re), it is almost impossible to predict full scale ship maneuverability using conventional methods such as model test. On the other hands, with the developments of computational technologies and computational fluid dynamics (CFD) techniques, CFD simulations are widely applied on ship maneuvering problems (e.g. Stern et al., 2011). Moreover some of the researchers start the CFD simulation with full scale Re especially on propulsion problems (e.g. Tezdogan et al., 2015) which showing reasonable results. Therefore, in this paper, captive maneuvering simulations (rudder angle test) in model/full scale Re on KVLCC2 are carried out using Reynolds-averaged Navier–Stokes (RANS) solver NAGISA (Ohashi et al., 2014) with the overset gird method UP_GRID (Kodama et al., 2012). And the results between model and full scale simulations are compared in maneuvering coefficients and flow field to reveal the scale effect on ship maneuverability.

scholarly journals Comparison of CFD Simulation to UAS Measurements for Wind Flows in Complex Terrain: Application to the WINSENT Test Site

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1992 ◽  
Author(s):  
Asmae El Bahlouli ◽  
Alexander Rautenberg ◽  
Martin Schön ◽  
Kjell zum Berge ◽  
Jens Bange ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cfd Simulation ◽  
Test Site ◽  
Unmanned Aircraft ◽  
Navier Stokes ◽  
Area Index ◽  
Flow Features ◽  
High Turbulence ◽  
Computational Fluid Dynamics Cfd ◽  
Aircraft System

This investigation presents a modelling strategy for wind-energy studies in complex terrains using computational fluid dynamics (CFD). A model, based on an unsteady Reynolds Averaged Navier-Stokes (URANS) approach with a modified version of the standard k-ε model, is applied. A validation study based on the Leipzig experiment shows the ability of the model to simulate atmospheric boundary layer characteristics such as the Coriolis force and shallow boundary layer. By combining the results of the model and a design of experiments (DoE) method, we could determine the degree to which the slope, the leaf area index, and the forest height of an escarpment have an effect on the horizontal velocity, the flow inclination angle, and the turbulent kinetic energy at critical positions. The DoE study shows that the primary contributor at a turbine-relevant height is the slope of the escarpment. In the second step, the method is extended to the WINSENT test site. The model is compared with measurements from an unmanned aircraft system (UAS). We show the potential of the methodology and the satisfactory results of our model in depicting some interesting flow features. The results indicate that the wakes with high turbulence levels downstream of the escarpment are likely to impact the rotor blade of future wind turbines.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

scholarly journals CFD Simulation for Estimating Efficiency of PBCF Installed on a 176K Bulk Carrier under Both POW and Self-Propulsion Conditions

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1192
Author(s):  
Dong-Hyun Kim ◽  
Jong-Chun Park ◽  
Gyu-Mok Jeon ◽  
Myung-Soo Shin
Keyword(s):  
Cfd Simulation ◽  
Open Water ◽  
Navier Stokes ◽  
Water Efficiency ◽  
Ocean Engineering ◽  
Bulk Carrier ◽  
Incompressible Viscous Flow ◽  
Korea Research Institute ◽  
Torque Coefficient ◽  
Viscous Flow Field

In this paper, the efficiency of Propeller Boss Cap Fins (PBCF) installed at the bulk carrier was estimated under both Propeller Open Water (POW) and self-propulsion conditions. For this estimation, virtual model-basin tests (resistance, POW, and self-propulsion tests) were conducted through Computational Fluid Dynamics (CFDs) simulation. In the resistance test, the total resistance and the wake distribution according to ship speed were investigated. In the POW test, changes of thrust, torque coefficient, and open water efficiency on the propeller according to PBCF installation were investigated. Finally, the International Towing Tank Conference (ITTC) 1978 method was used to predict the effect of PBCF installation on self-propulsive coefficient and brake horsepower. For analyzing incompressible viscous flow field, the Reynolds-Averaged Navier–Stokes (RANS) equation with SST k-ω turbulence model was calculated using Star-CCM+ 11.06.010-R8. All simulation results were validated by comparing the results of model tests conducted at the Korea Research Institute of Ships and Ocean Engineering (KRISO). Consequently, for the self-propulsion test with the PBCF, a 1.5% reduction of brake horsepower was estimated in the simulation and a 0.5% reduction of the brake horsepower was estimated in the experiment.

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