Study of Available Turbulence and Cavitation Models to Reproduce Flow Patterns in Confined Flows

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
M. Coussirat ◽  
F. Moll ◽  
F. Cappa ◽  
A. Fontanals
Keyword(s):  
Numerical Models ◽  
Internal Flow ◽  
Numerical Results ◽  
Flow State ◽  
Quantitative Criterion ◽  
Complex Flow ◽  
Two Phase ◽  
Computational Costs ◽  
Extensive Analysis ◽  
Confined Flows

Cavitating flow in nozzles is a complex flow which implies a highly turbulent two-phase one. An accurate simulation which improves some numerical results found in the literature was achieved by means of an extensive analysis of the capabilities of several numerical models for turbulence and cavitation. The analysis performed involves calibration/optimization tasks based on the physics of this kind of flow. This work aims to provide a quantitative criterion for the judgment of internal flow state, because it was demonstrated that the numerical results obtained with noncalibrated models could be enhanced by means of a careful calibration and thus saving computational costs.

Numerical solutions to wave interaction with rubblemound breakwaters

1990 ◽  
Vol 17 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Kevin R. Hall
Keyword(s):  
Numerical Modelling ◽  
Numerical Solution ◽  
Numerical Solutions ◽  
Scale Effects ◽  
Numerical Models ◽  
Internal Flow ◽  
Wave Interaction ◽  
Theoretical Development ◽  
Porous Media Flow ◽  
Complex Flow

The interaction of a wave with a rubblemound breakwater results in a complex flow field which is both nonlinear and turbulent, particularly within a region close to the surface of the structure. Numerical models describing internal flow in a rubblemound breakwater are becoming increasingly important, particularly as the influence of scale effects on internal flow in physical hydraulic models are becoming understood as important. A number of numerical models to predict the internal breakwater flow kinematics have been produced in the past two decades. This paper provides a review of the state-of-the-art of numerical modelling of wave interaction with rubblemound breakwaters. Details of the theoretical development and the resulting numerical solution techniques are presented. Methods for incorporating secondary effects such as two-phase (air–water) flow, inertia, and unbalanced boundary conditions are discussed. Limitations of the models resulting from the validity of the assumptions made in order to effect a numerical solution are discussed. Key words: breakwaters, internal flow, porous media flow, numerical modelling, rubblemound breakwaters.

Study on Influence of Nozzle Structure on Flow in Diesel Nozzle Orifice

2012 ◽  
Vol 246-247 ◽  
pp. 127-130
Author(s):  
Bing Li ◽  
Xue Song Hu ◽  
Xiao Feng Cao ◽  
Gui Qi Jia ◽  
Fang Xi Xie ◽  
...  
Keyword(s):  
Flow Characteristics ◽  
Internal Flow ◽  
Key Factors ◽  
Complex Flow ◽  
Two Phase ◽  
Nozzle Orifice ◽  
Fuel Flow ◽  
Flow Features ◽  
Diesel Nozzle ◽  
Nozzle Hole

The fuel flow characteristics in diesel nozzle orifice are key factors to the atomization of fuel near the nozzle orifice. In the paper, two-phase flow model is used to simulate the complex flow features in nozzle orifice, and to study the influences of the relative position of nozzles orifice axis and nozzle axis, and inclination angle of nozzle hole on the internal flow feature.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

2011 ◽  
Vol 418-420 ◽  
pp. 2006-2011
Author(s):  
Rui Zhang ◽  
Cheng Jian Sun ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

Visualization Experiment with PIV and Analysis of Flow Field in Hydrodynamic Coupling

2010 ◽  
Vol 29-32 ◽  
pp. 1327-1333
Author(s):  
Xiu Quan Lu ◽  
Wen Xing Ma ◽  
Li Dan Fan ◽  
Bo Sen Cai
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Internal Flow ◽  
Two Dimensions ◽  
Flow State ◽  
Complex Flow ◽  
Piv Technique ◽  
Hydrodynamic Coupling ◽  
Visualization Experiment ◽  
Testing Technology

In order to study the complex flow state of the internal flow field while the hydrodynamic coupling is under working conditions, the two dimensions PIV technique of the modern testing technology is adopted to test and analyze typical working conditions of hydrodynamic coupling. According to the experimental results, the internal flow field of the typical working conditions is analyzed and compared in qualitative way. The research of this paper has guiding significance for the hydrodynamic coupling design.

scholarly journals Evaluation of velocity fields in horizontal gas-liquid intermittent flows using Stereoscopic-PIV and instantaneous masking procedure

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Leonardo Soares Fernandes ◽  
Rodrigo dos Santos Navarro De Mesquita ◽  
Fabio Jessen Werneck de Almeida Martins ◽  
Luis Fernando Alzuguir Azevedo
Keyword(s):  
Liquid Velocity ◽  
Numerical Models ◽  
Velocity Fields ◽  
Gas Bubble ◽  
Complex Flow ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Stereoscopic Piv ◽  
Liquid Flows

The main goal of this work was to obtain well-converged liquid velocity profiles for intermittent gas-liquid flows in a horizontal pipe. To this end, air and water with superficial velocities of JG = 0.5 m/s and JL = 0.3, 0.4 and 0.5 m/s, respectively, were driven into a 18-m acrylic test section with an inner diameter of 40 mm. All three-components of the velocity vectors were measured in a pipe cross-section using a highfrequency stereoscopic PIV system, together with the laser induced fluorescence technique. Photogates were used to measure the unit cell translational velocity, as well as to trigger data acquisition, allowing the calculation of ensemble-averaged velocity fields at specific positions, referenced to the gas-bubble nose tip position. An instantaneous image masking procedure was implemented, allowing the determination of non-dimensional ensemble-averaged velocity profile in the liquid film, referenced to gas-bubble boundary. The high-frequency system employed allowed the determination of the influence of the faster-moving gas bubble on the liquid velocity field in the plug region. The data presented are relevant to the validation and improvement of one-dimensional two-phase numerical models, as well as to better understand this complex flow.

Modeling Strategy for the Analysis of Forced Draft Air-Cooled Condensers Using Rotational Fan Models

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Ruan A. Engelbrecht ◽  
Chris J. Meyer ◽  
Johan van der Spuy
Keyword(s):  
Numerical Models ◽  
Axial Flow ◽  
Numerical Results ◽  
Evaluation Tool ◽  
Complex Flow ◽  
Recovery Coefficient ◽  
Disk Model ◽  
Alternative Evaluation ◽  
Flow Phenomena ◽  
Modeling Strategy

Air-cooled condenser (ACC) design methodologies use empirical correlations that are unable to account for the complex flow phenomena associated with ACCs. Numerical models are seen as an alternative evaluation tool. This paper details the development of a modeling strategy for an ACC in the computational fluid dynamics (CFD) code of OpenFOAM. The axial flow fan is modeled using the extended actuator disk model (EADM) and validated using the B2a-fan. A good agreement between experimental and numerical results are noted for the volumetric flow rates expected in the ACC operating range. The A-frame heat exchanger is also validated using the empirical data. The ACC operating point is numerically and analytically determined. An overprediction of the numerical results to the analytical solution is attributed to the presence of kinetic energy recovery and validated using experimental results. A numerical recovery coefficient of 0.527 is measured and correlates well with the experimentally determined coefficient of 0.553.

scholarly journals A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem

2020 ◽  
Vol 8 (11) ◽  
pp. 905
Author(s):  
Selahattin Kocaman ◽  
Kaan Dal
Keyword(s):  
Image Processing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Numerical Results ◽  
Dam Break ◽  
Frame Rate ◽  
Image Processing Technique ◽  
Complex Flow ◽  
The Impact

The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods.

ACCURACY ANALYSIS OF DIRECT INFRARED TEMPERATURE MEASUREMENTS OF TWO-PHASE CONFINED FLOWS

2018 ◽  
Author(s):  
Andrea Catarsi ◽  
Davide Fioriti ◽  
Mauro Mameli ◽  
Sauro Filippeschi ◽  
Paolo Di Marco
Keyword(s):  
Temperature Measurements ◽  
Accuracy Analysis ◽  
Two Phase ◽  
Confined Flows

scholarly journals Nonlinear multiscale simulation of instabilities due to growth of an elastic film on a microstructured substrate

2020 ◽  
Vol 90 (11) ◽  
pp. 2397-2412
Author(s):  
Iman Valizadeh ◽  
Oliver Weeger
Keyword(s):  
Deformation Gradient ◽  
Multiscale Simulation ◽  
Numerical Results ◽  
Unit Cell ◽  
Homogeneous Material ◽  
Two Phase ◽  
Biological Phenomena ◽  
Elastic Film ◽  
Living Tissues ◽  
Analytical Approaches

Abstract The objective of this contribution is the numerical investigation of growth-induced instabilities of an elastic film on a microstructured soft substrate. A nonlinear multiscale simulation framework is developed based on the FE2 method, and numerical results are compared against simplified analytical approaches, which are also derived. Living tissues like brain, skin, and airways are often bilayered structures, consisting of a growing film on a substrate. Their modeling is of particular interest in understanding biological phenomena such as brain development and dysfunction. While in similar studies the substrate is assumed as a homogeneous material, this contribution considers the heterogeneity of the substrate and studies the effect of microstructure on the instabilities of a growing film. The computational approach is based on the mechanical modeling of finite deformation growth using a multiplicative decomposition of the deformation gradient into elastic and growth parts. Within the nonlinear, concurrent multiscale finite element framework, on the macroscale a nonlinear eigenvalue analysis is utilized to capture the occurrence of instabilities and corresponding folding patterns. The microstructure of the substrate is considered within the large deformation regime, and various unit cell topologies and parameters are studied to investigate the influence of the microstructure of the substrate on the macroscopic instabilities. Furthermore, an analytical approach is developed based on Airy’s stress function and Hashin–Shtrikman bounds. The wavelengths and critical growth factors from the analytical solution are compared with numerical results. In addition, the folding patterns are examined for two-phase microstructures and the influence of the parameters of the unit cell on the folding pattern is studied.

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