A Numerical 3-D Model of a Trapezoidal Three-Hole Pneumatic Pressure Probe for Incompressible Flow

2010 ◽  
Author(s):  
Katia Mari´a Argu¨elles Di´az ◽  
Jesu´s Manuel Ferna´ndez Oro ◽  
Eduardo Blanco Marigorta ◽  
Rau´l Barrio Perotti
Keyword(s):  
Incompressible Flow ◽  
Turbulence Models ◽  
Pressure Probe ◽  
Flow Conditions ◽  
Pneumatic Pressure ◽  
Stagnation Points ◽  
Commercial Code ◽  
Reliable Model ◽  
Definition Of ◽  
D Model

Pneumatic pressure probes are well-mature measuring devices to characterize both pressure and velocity fields for external and internal flows. The measuring range of a particular probe is significantly influenced by important factors, like its geometry, the separation angle between the holes, the holes tapping or even flow conditions like separation and stagnation points or the local Reynolds number. Ideally, every pressure probe must be specifically designed for the particular application where it is needed. However, this procedure requires a detailed calibration of the probe for the whole expected range of velocities and incidences. This implies an important cost in both economic terms and operating times. Thus, the definition of an accurate numerical model for the design and calibration of pressure probes at different flow conditions is particularly desirable for these purposes. The first step towards the establishment of this useful methodology is the development of a reliable model to predict numerically the probe measuring characteristics. Thus, in this paper a numerical 3-D model is presented to characterize the calibration of a three-hole pneumatic pressure probe. In particular, a trapezoidal geometry with a 60 degree angle between the holes is considered here. The simulation of the flow incidence is carried out using the commercial code FLUENT, analyzing the influence of different mesh densities and turbulence models. The complete set of numerical cases includes different flow velocities and several yaw angles. The numerical results have been validated using experimental results obtained in a calibration facility, focusing on the definition of a numerical tool for the design and calibration of three-hole pneumatic probes under incompressible flow conditions.

scholarly journals Equivalent Scalar Stress Formulation Taking into Account Non-Resolved Turbulent Scales

2021 ◽  
Author(s):  
Lucas Konnigk ◽  
Benjamin Torner ◽  
Martin Bruschewski ◽  
Sven Grundmann ◽  
Frank-Hendrik Wurm
Keyword(s):  
Mechanical Stress ◽  
Turbulence Models ◽  
Turbulent Channel Flow ◽  
Simulation Method ◽  
Blood Damage ◽  
Stress Calculation ◽  
High Risk Factors ◽  
Cardiovascular Engineering ◽  
Scalar Stress ◽  
Definition Of

Abstract Purpose Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation. Methods We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data. Results The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases. Conclusion With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.

POSITIVITY OF k-EPSILON TURBULENCE MODELS FOR INCOMPRESSIBLE FLOW

2002 ◽  
Vol 12 (03) ◽  
pp. 393-406 ◽  
Author(s):  
ZI-NIU WU ◽  
SONG FU
Keyword(s):  
Reynolds Number ◽  
Point Source ◽  
Incompressible Flow ◽  
Iterative Procedure ◽  
High Reynolds Number ◽  
Operator Splitting ◽  
Turbulence Models ◽  
Diffusion Equations ◽  
Advection Diffusion ◽  
High Reynolds

The k-epsilon turbulence model for incompressible flow involves two advection–diffusion equations plus point-source terms. We propose a new method for positivity analysis. This method uses an iterative procedure combined with an operator splitting. With this method we recover the well-known positivity result for the standard high Reynolds number model. Most importantly, we are able to prove the positivity result for general low Reynolds number k-epsilon models.

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

Assessment of Certainty of Ventilation Processes Mathematical Modeling

2015 ◽  
Vol 725-726 ◽  
pp. 1255-1260
Author(s):  
Tamara Daciuk ◽  
Vera Ulyasheva
Keyword(s):  
Mathematical Modeling ◽  
Turbulent Flows ◽  
Turbulence Models ◽  
Field Measurements ◽  
Heat Emission ◽  
Emission Sources ◽  
Wide Range ◽  
Calculation Results ◽  
Definition Of ◽  
Semiempirical Models

Numerical experiment has been successfully used during recent 10-15 years to solve a wide range of thermal and hydrogasodynamic tasks. Application of mathematical modeling used to design the ventilation systems for production premises characterized by heat emission may be considered to be an effective method to obtain reasonable solutions. Results of calculation performed with numerical solution of ventilation tasks depend on turbulence model selection. Currently a large number of different turbulence models used to calculate turbulent flows are known. Testing and definition of applicability limits for semiempirical models of turbulence should be considered to be a preliminary stage of calculation. This article presents results of test calculations pertaining to thermal air process modeling in premises characterized by presence of heat emission sources performed with employment of different models of turbulence. Besides, analysis of calculation results and comparison with field measurements data are presented.

Numerical Simulations of Heat Transfer and Fluid Flow for a Rotating High-Pressure Turbine

2006 ◽  
Author(s):  
F. Mumic ◽  
L. Ljungkruna ◽  
B. Sunden
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Fluid Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
High Pressure Turbine ◽  
Experimental Heat ◽  
Commercial Code ◽  
Stator Vane

In this work, a numerical study has been performed to simulate the heat transfer and fluid flow in a transonic high-pressure turbine stator vane passage. Four turbulence models (the Spalart-Allmaras model, the low-Reynolds-number realizable k-ε model, the shear-stress transport (SST) k-ω model and the v2-f model) are used in order to assess the capability of the models to predict the heat transfer and pressure distributions. The simulations are performed using the FLUENT commercial software package, but also two other codes, the in-house code VolSol and the commercial code CFX are used for comparison with FLUENT results. The results of the three-dimensional simulations are compared with experimental heat transfer and aerodynamic results available for the so-called MT1 turbine stage. It is observed that the predictions of the vane pressure field agree well with experimental data, and that the pressure distribution along the profile is not strongly affected by choice of turbulence model. It is also shown that the v2-f model yields the best agreement with the measurements. None of the tested models are able to predict transition correctly.

Simulation Comparison of PEMFC Micro-Cogeneration Units With Conventional and Innovative Fuel Processing

2010 ◽  
Author(s):  
Leonardo Roses ◽  
Davide Bonalumi ◽  
Stefano Campanari ◽  
Paolo Iora ◽  
Giampaolo Manzolini
Keyword(s):  
Polymer Electrolyte Membrane ◽  
Performance Comparison ◽  
Fuel Processing ◽  
Electrolyte Membrane ◽  
Simulated Performance ◽  
Commercial Code ◽  
The One ◽  
Definition Of ◽  
Performance Results ◽  
Energy Balances

This paper deals with the performance comparison over simulated micro-cogeneration units based on polymer electrolyte membrane fuel cells (PEMFC or PEM), when the fuel is processed by means of two contrasting techniques. On the one hand with the use of conventional natural gas steam reforming (SR), and on the other, the adoption of an innovative palladium based membrane-reformer. After the definition of the plant layout, which reflects the results of previous studies and includes all the components of a 4 kW PEM for combined heat and power production, the comparison among the plant performances is carried out with two approaches: (i) using a in-house developed code (GS), able to calculate mass and energy balances, as well as a number of specific component parameters, already applied to a large variety of plant simulations, and (ii) using a commercial code (Aspen Plus®). The comparison allows to validate the simulated performance results as well as to evidence the advantages of the two approaches and to assess the effects of different simulation assumptions.

CFD Analysis of Stall in a Wells Turbine

2018 ◽  
Author(s):  
Kellis Kincaid ◽  
David W. MacPhee
Keyword(s):  
Source Code ◽  
Turbulence Models ◽  
Ocean Waves ◽  
Cfd Analysis ◽  
Oscillating Water Column ◽  
Blade Profile ◽  
Flow Conditions ◽  
Wells Turbine ◽  
Sst Model ◽  
Blade Shape

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.

Selection of an Appropriate Turbulence Model to Evaluate Performances of Novel Fuel Geometries for the “IRIS” Reactor

2003 ◽  
Author(s):  
Emilio Baglietto ◽  
Hisashi Ninokata
Keyword(s):  
Linear Models ◽  
Flow Direction ◽  
Turbulence Models ◽  
Shear Stresses ◽  
Plane Normal ◽  
Rod Bundle ◽  
Commercial Code ◽  
Non Linear ◽  
Turbulence Closures ◽  
Tight Lattice

A comparative study of different turbulence models is presented to select the most appropriate one for the evaluation of thermo-hydraulic performances of innovative core designs. The standard k-ε and different, linear and non linear, low Reynolds k-ε models are applied to fully developed flow in a triangular lattice rod bundle. Shear stresses and velocity distributions are evaluated using the commercial code Star-CD. The relative performance of the models is assessed indicating different predictions between linear and non linear turbulence closures. The results show that the capability of non linear models to account for anisotropic effects leads to better performances in modeling turbulent flow in tight lattice rod bundles. This capability is clearly shown by the existence of a secondary flow field in the plane normal to the flow direction.

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