scholarly journals Simulation of Pharyngeal Airway Interaction with Air Flow Using Low-Re Turbulence Model

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
M. R. Rasani ◽  
K. Inthavong ◽  
J. Y. Tu
Keyword(s):  
Turbulence Model ◽  
Air Flow ◽  
Three Dimensional ◽  
Lagrangian Description ◽  
Three Dimensional Model ◽  
Pharyngeal Airway ◽  
Partitioned Approach ◽  
Flow Features ◽  
Airway Opening ◽  
Sst Turbulence Model

This paper aims to simulate the interaction between a simplified tongue replica with expiratory air flow considering the flow in the pharyngeal airway to be turbulent. A three-dimensional model with a low-Re SST turbulence model is adopted. An Arbitrary Eulerian-Lagrangian description for the fluid governing equation is coupled with the Lagrangian structural solver via a partitioned approach, allowing deformation of the fluid domain to be captured. Both the three-dimensional flow features and collapsibility of the tongue are presented. In addition, examining initial constriction height ranging from 0.8 mm to 11.0 mm and tongue replica modulus from 1.25 MPa to 2.25 MPa, the influence of both of these parameters on the flow rate and collapsibility of the tongue is also investigated and discussed. Numerical simulations confirm expected predisposition of apneic patients with narrower airway opening to flow obstruction and suggest much severe tongue collapsibility if the pharyngeal flow regime is turbulent compared to laminar.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

2014 ◽  
Vol 30 (6) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Moshizi ◽  
M. H. Nakhaei ◽  
M. J. Kermani ◽  
A. Madadi
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Streamline Curvature ◽  
Sst Turbulence Model ◽  
Stator Blade ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

Analysis of plunging phenomenon in dam reservoirs using three-dimensional density flow simulations

2008 ◽  
Vol 35 (10) ◽  
pp. 1138-1151 ◽  
Author(s):  
Fatih Üneş
Keyword(s):  
Turbulence Model ◽  
Coriolis Force ◽  
Present Model ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Dam Reservoir ◽  
Reservoir Flow ◽  
Dam Reservoirs ◽  
Density Flow

Density flow is investigated in a three-dimensional model through a dam reservoir with diverging and sloping bottom channels. When an inflow of higher density enters ambient dam reservoir water, it plunges below the ambient water and becomes density underflow. In the present model, nonlinear and unsteady continuity, momentum, energy, and turbulence model equations are formulated in the Cartesian coordinates. The k–ε turbulence model is used with an extension to include production or destruction of turbulent kinetic energy. To investigate the Coriolis force effect on the density flow in a dam reservoir, a Coriolis force parameter is included in the governing equations. The equations of the model are solved based on the initial and boundary conditions of the dam reservoir flow for a range of bottom slopes and divergence angles. In this paper, variation in density flow parameters, such as velocity, temperature, and turbulence viscosity through the dam reservoir, is investigated. Moreover, mixing rate, plunging points, and plunging depths are determined from the simulation results. The results of the present model are compared with the previous experimental work and model. The present model results follow the expected basic trend. The three-dimensional model simulation and analysis improve the understanding of density flow, underflow, divergence flow, mass transport, and dam–reservoir flow interaction.

The Effect of Reynolds Number on the Ventilation Efficiency in a Wind Tunnel

2004 ◽  
Author(s):  
Jun Li ◽  
Ibrahim Yavuz ◽  
Ismail B. Celik ◽  
Steven E. Guffey
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Concentration Field ◽  
Reynolds Numbers ◽  
Ethanol Vapor ◽  
Vapor Concentration ◽  
Equivalent Diameter ◽  
Three Dimensional Model ◽  
Rng Turbulence Model

The present work is concerned with the effect of the ventilation intensity on the worker exposure in a tunnel when the worker is facing the downstream direction and a gaseous contaminant is released in an arm length of his reach. A three-dimensional model of a manikin which was used in the experiments was created in order to study the effect of the mean inlet velocity which can be characterized by the Reynolds number based on the equivalent diameter of the head of the manikin. For this study, turbulent flow was assumed to enter the ventilation tunnel and exit at the other end from an exhaust duct. The scalar transport method was employed to determine the ethanol vapor concentration field. The results with the low_Re RNG turbulence model are compared to the ones with the RNG turbulence model. The results with the RNG k-ε turbulence model seem to agree better with the experimental data at higher Reynolds numbers. At lower Reynolds numbers there are significant differences between experiments and predictions.

scholarly journals Numerical study of the low-Reynolds flows in the vertical heated caverns

2019 ◽  
Vol 213 ◽  
pp. 02065
Author(s):  
Mikhail Petrichenko ◽  
Vitaly Sergeev ◽  
Darya Nemova ◽  
Evgeny Kotov ◽  
Darya Tarasova
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Turbulence Model ◽  
Energy Equation ◽  
Numerical Study ◽  
Temperature Drop ◽  
Three Dimensional ◽  
Experimental Results ◽  
Sst Turbulence Model ◽  
Heated Plates

The object of research is the critical geometry of a three-dimensional air flow in a cavern between two vertical heated plates. In this rate the convection's contribution to heat transfer will be limited due to thermal conductivity at a fixture temperature drop. A three-dimensional RANS approach closed by the k-w SST turbulence model in conjunction with the energy equation. The model validated and verified by comparison with the experimental results. The results of the work applied in developing of ventilated façades.

scholarly journals Validating the k-ω Turbulence Model for 3D Flows within the CFD Solver Eilmer

2016 ◽  
Vol 846 ◽  
pp. 67-72
Author(s):  
Samuel Stennett ◽  
Wilson Chan ◽  
David E. Gildfind ◽  
Peter Jacobs
Keyword(s):  
Turbulence Model ◽  
High Speed ◽  
Compressible Flows ◽  
Three Dimensional ◽  
Cross Flow ◽  
Main Flow ◽  
Test Cases ◽  
Flow Features ◽  
The University ◽  
3D Flows

The computational fluid dynamics solver Eilmer has proven useful to The University of Queensland’s Centre for Hypersonics for its ability to simulate high-speed compressible flows. In Eilmer, turbulence is modelled using Wilcox’s 2006 k-ω model. While the turbulence model implementation has been validated for two-dimensional and axisymmetric flows, validation is required for three-dimensional flows. The present paper describes the progress of the validation of the k-ω turbulence model for two three-dimensional test cases. A case featuring Mach 4.5 air flow over a flat plate produced results that correlated with previous numerical results within 4%. A second case featuring the injection of Mach 1 air into a Mach 4 air cross-flow produced results indicating that the code successfully captured the main flow features.

Development of Quasi-Three Dimensional Turbulence Model for Film Cooling on Flat Plate

1993 ◽  
Author(s):  
Joo Sung Maeng ◽  
Jong Shin Lee
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Coordinate Systems ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Flat Plates ◽  
Finite Analytic Method ◽  
Simpler Algorithm

The present paper describes predictions of Full Coverage Film Cooling. The calculations have been performed by a quasi-three dimensional model that account for the basically three dimensional nature of the flow. The quasi-three dimensional model are solved by finite analytic method, modified simpler algorithm and body fitted coordinate systems. The turbulent stresses and heat fluxes are obtained from the low Reynolds K-ε turbulence model. The results are given for flows over flat plates for different injection angles, relative spacings, blowing rates and injection temperatures.

Flow and Heat Transfer Computations in a Rotating Cavity With Tangential Seal Air Flow

1997 ◽  
Author(s):  
Prabhat Tekriwal
Keyword(s):  
Heat Transfer ◽  
Air Flow ◽  
Three Dimensional ◽  
Thermomechanical Analysis ◽  
Heat Transfer Analysis ◽  
Symmetric Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Life Study ◽  
Analysis And Design

Axi-symmetric and three-dimensional CFD models for a rotating open interdisk cavity have been developed to predict flow, heat transfer, windage power loss and cavity air temperatures as a part of the rotor thermomechanical analysis and design life study. The cavity has a tangential (axial and circumferential) seal air flow above it. The rotational Reynolds number is 4.8 × 106 and the non-dimensional seal flow rate is 9.8 × 104. Measured wall temperatures are used as boundary conditions in the model. The axi-symmetric model smears the cavity bolts as 360° continuous rings and therefore ignores the bolts pumping effect. The windage loss calculation from the axi-symmetric model is in good agreement with the experimental data in the literature. The heat transfer coefficient values from the axi-symmetric and three-dimensional models are comparable in most of the regions apart from near the bolts. Also, the three-dimensional model simulates the bolt pumping effects and yields a much higher windage loss value, which in turn raises the cavity air temperature. It is concluded that a three-dimensional model is necessary for an accurate heat transfer analysis.

On the Correction of k-ω SST Turbulence Model to Three-Dimensional Shock Separated Flow

2021 ◽  
pp. 373-384
Author(s):  
Yiming Du ◽  
Bowen Shu ◽  
Zhenghong Gao ◽  
Shengyang Nie ◽  
Rui Ma
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Separated Flow ◽  
Sst Turbulence Model
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