Influence of Inlet Boundary Conditions on Simulations of an Asymmetric Diffuser With the V2F Turbulence Model

2015 ◽  
Author(s):  
James Crawford ◽  
A. M. Birk
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Excellent Agreement ◽  
Turbulence Model ◽  
Two Dimensional ◽  
Ansys Fluent ◽  
Inlet Velocity

A set of numerical simulations were performed on an asymmetric, two dimensional diffuser using ANSYS Fluent 14.0, a commercially available RANS based CFD code. The ν′2¯-f turbulence model, which has previously been shown to be a good model for this geometry, was implemented through a user defined function, and the influence of inlet boundary conditions was evaluated. It was shown that the inlet velocity and turbulence profiles had a significant effect on the calculated performance of the diffuser, especially in terms of the onset of diffuser stall. It was shown that when the boundary conditions were set appropriately, excellent agreement with LES and experimental data was obtained.

scholarly journals Comparison of Reactive Flow Simulations for a LOX/CH4 Multi-element Rocket Engine

2019 ◽  
Vol 304 ◽  
pp. 07007
Author(s):  
Ainslie D. French ◽  
Luigi Cutrone ◽  
Antonio Schettino ◽  
Marco Marini ◽  
Francesco Battista ◽  
...  
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Rocket Engine ◽  
Engine Performance ◽  
Heat Fluxes ◽  
Reactive Flow ◽  
Flow Data ◽  
Flow Simulations ◽  
Experiment Validation

This study details the reactive flow simulations of a LOX/CH4 Multi-element rocket engine. The work has been conducted within the framework of the HYPROB-BREAD project whose main objective is the design, manufacture and testing of a LOX/LCH4 regeneratively cooled ground demonstrator. Numerical simulations have been carried out with both commercial software and CIRA software developed in house. Two sets of boundary conditions, nominal and experimental, have been applied from which a code-to-code validation has been effected with the former and a code-to-experiment validation with the latter. The results presented include both flow data and heat fluxes as well as parameters associated with engine performance, and indicate an excellent agreement with experimental data of a LOX/CH4 Multi-element rocket engine.

Numerical Study on Hydraulic Performances of Pump as Turbine With Forward-Curved Blades

2014 ◽  
Author(s):  
Tao Wang ◽  
Fanyu Kong ◽  
Sunsheng Yang ◽  
Yanxia Fu
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Numerical Simulations ◽  
Turbulence Model ◽  
Numerical Study ◽  
Internal Flow ◽  
Hydraulic Turbine ◽  
Experimental Results ◽  
Computational Accuracy ◽  
Computational Stability

A reserved running centrifugal pump can work as a hydraulic turbine with its wide application in industrial energy recovery and the development of micro-hydraulic power. In order to improve the efficiency from the point of turbine working condition, the impeller with forward-curved blades was designed and the hydraulic performances were further analyzed based on the commercial software ANSYS CFX 12.0 in this study. Moreover, to improve the computational accuracy of numerical simulations on turbines, the grid number, the turbulence model, the circumferential flow distribution in the clearance between the volute and the impeller as well as the grid distribution in the boundary layer were considered. According grid independency analysis, the 1.2 million grids’ number was assumed for numerical simulations. Considering the consuming time and computational stability, as well as the accuracy of the CFD calculation, the k–ε turbulence model was chosen for further calculations. The shaft power and the efficiency of the turbine were more close to the experimental data as the whole computational flow domain in the clearance between the volute and the impeller was connected on the impeller domain. Compared with the performance curves with or without grids in the boundary layer, the boundary layer with grids used in the PAT during numerical simulations was more close to the experimental one. Compared with the experimental data, the H-Q curves of the hydraulic performances of the turbine with forward-curved blades predicted by CFD were positioned under the experimental one. With respect to the efficiency of the turbine, the various ranges of the efficiency is less than 5%, even there is some deviations between the CFD and experimental results. Therefore, the good agreement of the hydraulic performances between CFD and experimental results in present study indicates that the proposed numerical methods can adequately capture the internal flow in a hydraulic turbine with forward-curved blades, and can also provide a reliable reference for the design of hydraulic turbines.

scholarly journals Angular Dependence of Highly Nonlinear Pulse Splitting in a Two Dimensional Granular Network

2010 ◽  
Author(s):  
D. Ngo ◽  
F. Fraternali ◽  
C. Daraio
Keyword(s):  
Experimental Data ◽  
Stainless Steel ◽  
Numerical Simulations ◽  
Angular Dependence ◽  
Granular System ◽  
Two Dimensional ◽  
Highly Nonlinear ◽  
Solitary Pulse ◽  
First Time ◽  
Pulse Splitting

We investigate experimentally and numerically the propagation of highly nonlinear signals in a branched two-dimensional granular system composed by chains of uniform spherical beads. The system consists of a Y-shaped guide with various branch angles in which stainless steel spheres are arranged. We study the dynamic behavior of a solitary pulse crossing the bifurcated interface, and splitting between the two branches. We report for the first time the dependence of the split pulses’ speed on the branch angles. Numerical simulations based on Hertzian interaction between the particles are found in agreement with the experimental data.

Comparison of experimental data and numerical simulation of two-phase flow pattern in vertical minichannel

2012 ◽  
Vol 33 (1) ◽  
pp. 63-71
Author(s):  
Jarosław Sowiński ◽  
Marek Krawczyk ◽  
Marek Dziubiński
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Computational Domain ◽  
Two Phase ◽  
Ansys Fluent ◽  
Satisfactory Description

Comparison of experimental data and numerical simulation of two-phase flow pattern in vertical minichannel The aim of the study was the implementation of a numerical simulation of the air-water two-phase flow in the minichannel and comparing results obtained with the values obtained experimentally. To perform the numerical simulations commercial software ANSYS FLUENT 12 was used. The first step of the study was to reproduce the actual research installation as a three-dimensional model with appropriate and possible simplifications - future computational domain. The next step was discretisation of the computational domain and determination of the types of boundary conditions. ANSYS FLUENT 12 has three built-in basic models with which a two-phase flow can be described. However, in this work Volume-of-Fluid (VOF) model was selected as it meets the established requirements of research. Preliminary calculations were performed for a simplified geometry. The calculations were later verified whether or not the simplifications of geometry were chosen correctly and if they affected the calculation. The next stage was validation of the chosen model. After positive verification, a series of calculations was performed, in which the boundary conditions were the same as the starting conditions in laboratory experiments. A satisfactory description of the experimental data accuracy was attained.

Numerical Simulations of Tsunami Wave Generation by Submarine and Aerial Landslides Using RANS and SPH Models

2009 ◽  
Author(s):  
Kaushik Das ◽  
Ron Janetzke ◽  
Debashis Basu ◽  
Steve Green ◽  
John Stamatakos
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Simulations ◽  
Tsunami Wave ◽  
Wave Generation ◽  
Numerical Results ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Tsunami Waves ◽  
Time Histories

Tsunami wave generation by submarine and aerial landslides is examined in this paper. Two different two-dimensional numerical methods have been used to simulate the time histories of fluid motion, free surface deformation, shoreline movement, and wave runup from tsunami waves generated by aerial and submarine landslides. The first approach is based on the Navier-Stokes equation and the volume of fluid (VOF) method: the Reynolds Averaged Navier-Stokes (RANS)-based turbulence model simulates turbulence, and the VOF method tracks the free surface locations. The second method uses Smoothed Particle Hydrodynamics (SPH)—a numerical model based on a fully Lagrangian approach. In the current work, two-dimensional numerical simulations are carried out for a freely falling wedge representing the landslide and subsequent wave generations. Numerical simulations for the landslide-driven tsunami waves have been performed with different values of landslide material densities. Numerical results obtained from both approaches are compared with experimental data. Simulated results for both aerial and submerged landslides show the complex flow patterns in terms of the velocity field, shoreline evolution, and free-surface profiles. Flows are found to be strongly transient, rotational, and turbulent. Predicted numerical results for time histories of free-surface fluctuations and the runup/rundown at various locations are in good agreement with the available experimental data. The similarity and discrepancy between the solutions obtained by the two approaches are explored and discussed.

Numerical Investigation of Transonic Compressor Rotor Flow Using an Implicit 3D Flow Solver With One-Equation Spalart-Allmaras Turbulence Model

2001 ◽  
Author(s):  
Fangfei Ning ◽  
L. Xu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Model Equation ◽  
Stokes Equations ◽  
Turbulence Closure ◽  
Two Dimensional ◽  
Mean Flow ◽  
Internal Flows ◽  
Flow Equations ◽  
Transonic Compressor

A CFD code for three-dimensional viscous flows, in particular for those in turbomachinery, has been developed based on Favre-averaged compressible Navier-Stokes equations and one-equation Spalart-Allmaras turbulence closure. The model equation of Spalart-Allmaras turbulence closure is converted into conservative form and discretized in the same manner as that for mean flow equations. A two-dimensional transonic diffuser flow and a two-dimensional transonic nozzle flow which feature pressure-gradient induced separation and shock wave/boundary layer interaction respectively are used to validate the code and application of the Spalart-Allmaras model (hereafter the S-A model) in internal flows. It is shown that the S-A model can give fairly good results compared to the experimental data. Some modifications of model equation are introduced for improving the grid insensitivity of the turbulence model. To validate the applicability of the code to the complex flows in transonic turbomachines, flows through two transonic compressor rotors, NASA Rotors 67 and 37 are calculated, and numerical results are compared with the well documented experimental data. The calculated results agree reasonably well with the experiments, and as expected, the S-A model, which is primarily developed for external flows, can also be effectively applied to internal flows. Discrepancies between the experimental data and calculations and the possible causes are also discussed.

An Assessment of Turbulence Models for S-Duct Diffusers With Flow Control

2013 ◽  
Author(s):  
S. P. Bhat ◽  
R. K. Sullerey
Keyword(s):  
Experimental Data ◽  
Flow Control ◽  
Turbulence Model ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Experimental Results ◽  
Cfd Analysis ◽  
Duct Flow ◽  
Ansys Fluent ◽  
Sst Model

The selection of a turbulence model for a problem is not trivial and has to be done systematically after comparison of various models with experimental data. It is a well known fact that there is no such turbulence model which fits all problems ([3], [13]). The flow in S-duct diffuser is a very complex one where both separation and secondary flow coexist. Previous work by the author on CFD analysis of S-duct diffuser was done using k-ε-Standard model [1], however it has been seen that choosing other turbulence model may result in better capturing of the physics in such a problem. Also flow control, to reduce energy losses, is achieved using a technique called Zero Net Mass Flow (ZNMF), in which suction and vortex generation jets (VGJ) are combined and positioned at optimum location. A proper turbulence model has to be chosen for capturing these phenomena effectively. Extensive experimental data is available on this problem and ZNMF technique from previous work done by one of the authors which is used for validating the CFD results. Here the focus is on choosing the best turbulence model for the S-duct diffuser. Numerical (CFD) analysis is carried out using Ansys Fluent 13.0 with six turbulence models for the geometry with (ZNMF) and without (Bare duct) flow control and then compared with the experimental results. The turbulence models used are Spalart-Allmaras, three variants of k-ε – Standard, RNG and Realizable and two variants of k-ω – Standard and SST model. All the parameters of comparison are non-dimensionalized using the free stream properties, so that the results are applicable to a wider range of problems. This work is limited to incompressible flow analysis, as the experimental data is only available for low Mach number flows. Comparison of all these models clearly shows that results obtained using k-ω-SST model are very comparable to the experimental results for the bare duct (without flow control) and flow controlled duct both in terms of distribution of properties and aggregate results. Compressible flow analysis can be attempted to achieve reliable results in future with ZNMF using the best turbulence model based on this study.

scholarly journals Selection of a turbulence model to calculate the temperature profile near the surface of VVER-1000 fuel assemblies in the NPP spent fuel pool

2021 ◽  
Vol 7 (2) ◽  
pp. 79-84
Author(s):  
Aleksandra V. Voronina ◽  
Sergey V. Pavlov
Keyword(s):  
Experimental Data ◽  
Natural Convection ◽  
Fuel Assembly ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Calculated Data ◽  
Spent Fuel ◽  
Average Deviation ◽  
Ansys Fluent

The paper considers the problem of selecting a turbulence model to simulate natural convection near the surface of a VVER-1000 fuel assembly unloaded from the reactor by computational fluid dynamics (CFD simulation) methods. The turbulence model is selected by comparing the calculated data obtained using the Ansys Fluent software package with the results of experimental studies on the natural convection near the surface of a heated vertical plate immersed in water, which simulates the side face of the VVER-1000 fuel assembly in a first approximation. Two-parameter semi-empirical models of turbulence, k-ε and k-ω, are considered as those most commonly used in engineering design. The calculated and experimental data were compared based on the excessive temperature of the plate surface and the water temperature profiles in the turbulent boundary layer for convection modes with a Rayleigh number of 8∙1013 to 3.28∙1014. It has been shown that the best agreement with experimental data, with an average deviation not exceeding ~ 8%, is provided by the RNG k-ε model which is recommended to be used to simulate natural convection near the surface of VVER-1000 FAs in the NPP spent fuel storage pool.

Boundary Conditions for Limited Area Models Based on the Shallow Water Equations

2013 ◽  
Vol 14 (3) ◽  
pp. 664-702 ◽  
Author(s):  
Arthur Bousquet ◽  
Madalina Petcu ◽  
Ming-Cheng Shiue ◽  
Roger Temam ◽  
Joseph Tribbia
Keyword(s):  
Boundary Conditions ◽  
Numerical Simulations ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Water System ◽  
Limited Area ◽  
Two Dimensional ◽  
One Dimensional ◽  
Shallow Water System ◽  
The Waves

AbstractA new set of boundary conditions has been derived by rigorous methods for the shallow water equations in a limited domain. The aim of this article is to present these boundary conditions and to report on numerical simulations which have been performed using these boundary conditions. The new boundary conditions which are mildly dissipative let the waves move freely inside and outside the domain. The problems considered include a one-dimensional shallow water system with two layers of fluids and a two-dimensional inviscid shallow water system in a rectangle.

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