scholarly journals Impact of Turbulence Models on the Air Flow in a Confined Rectangular Space

2020 ◽  
pp. 46-53
Author(s):  
Jakub Mularski ◽  
Amit Arora ◽  
Muhammad Azam Saeed ◽  
Łukasz Niedźwiecki ◽  
Samrand Saeidi
Keyword(s):  
Experimental Data ◽  
Air Flow ◽  
Turbulence Models ◽  
The Other ◽  
Experimental Measurements ◽  
Wall Region ◽  
Sst Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
The Given

The paper regards the impact of four different turbulence models on the air flow pattern in a confined rectangular space. The following approaches are analyzed. The Baseline (BSL) Reynolds model, the Speziale-Sarkar-Gatzki (SSG) Reynolds model, the Menter's shear-stress transport (SST) model and the basic k-ε model. Computational fluid dynamics (CFD) results are compared with the experimental measurements in four different planes. The Reynolds number for the given conditions is equal to 5000. The k-ε model yielded the most accurate results with regard to the experimental data but its reliability decreased near the wall region. With respect to the other models, it was also found that the k-ε approach generated the least circulating flow.

On the Validation of Turbulence Models for Wheel and Wheelhouse Aerodynamics

2021 ◽  
Author(s):  
Kaloki Nabutola ◽  
Sandra Boetcher
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Vehicle Body ◽  
Flow Structures ◽  
Time Resolved ◽  
Flow Control Devices ◽  
Vehicle Aerodynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Drag And Lift

Abstract Vehicle aerodynamics plays an important role in reducing fuel consumption. The underbody contributes to around 50% of the overall drag of a vehicle. As part of the underbody, the wheels and wheelhouses contribute to approximately 25-30% of the overall drag of a vehicle. As a result, wheel aerodynamics studies have been gaining popularity. However, a consensus of an appropriate turbulence model has not been reached, partially due to the lack of experiments appropriate for turbulence model validation studies for this type of flow. Seven turbulence models were used to simulate the flow within the wheelhouse of a simplified vehicle body, and results were shown to be incongruous with commonly used experimental data. The performance of each model was evaluated by comparing the aerodynamic coefficients obtained using computational fluid dynamics (CFD) to data collected from the Fabijanic wind tunnel experiments. The various turbulence models generally agreed with each other when determining average values, such a mean drag and lift coefficients, even if the particular values did not fall within the uncertainty of the experiment; however, they exhibited differences in the level of resolution in the flow structures within the wheelhouse. These flow structures are not able to be validated with currently available experimental data. Properly resolving flow structures is important when implementing flow control devices to reduce drag. Results from this study emphasize the need for spatially and time-resolved experiments, especially for validating LES and DES for flow within a wheelhouse.

CFD Studies on a Large Diameter Jet Impingement Flow

2004 ◽  
Author(s):  
Zhiguo Zhang ◽  
Mounir Ibrahim
Keyword(s):  
Experimental Data ◽  
Computational Study ◽  
Large Diameter ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
University Of Minnesota ◽  
Inlet Conditions ◽  
The University ◽  
The Impact

This paper presents computational study for a large diameter (216 mm) and small space ratios (S/D = 0.25 and 0.5) jet impingement flow. CFD-ACE code was used as the computational tools; the code was first validated by comparing its predictions with both CFD and experimental data from the literature. Then, the study was performed for two different Reynolds numbers: 7600, 17700 and two different space ratios: 0.25 and 0.5. Also two different turbulence models were utilized in this study: low Reynolds number turbulent k-ε and k-ω. The CFD results were compared with flow visualization results conducted at the University of Minnesota for the same configurations. The impact of choosing different inlet conditions on the CFD flow field was examined. The k-ε model showed greater sensitivity to the selection of the inlet conditions. Moreover, the k-ω model showed much better agreement with the experimental data than the k-ε model.

CFD analysis of the effect of nozzle stand-off distance on turbulent impinging jets

2013 ◽  
Vol 40 (7) ◽  
pp. 603-612 ◽  
Author(s):  
Mehrdad Shademan ◽  
Ram Balachandar ◽  
Ronald M. Barron
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Axial Direction ◽  
Reynolds Stress Model ◽  
Impinging Jets ◽  
Diameter Ratio ◽  
Wall Region ◽  
Nozzle Height ◽  
Jet Characteristics

Three-dimensional steady Reynolds Averaged Navier-Stokes simulations have been carried out to investigate the effect of the nozzle stand-off distance on the mean and turbulence characteristics of jets impinging vertically on flat surfaces. As part of the study, the performance of different turbulence models such as Realizable k–ε, k–ω SST, and Reynolds Stress Model (RSM) were evaluated. Based on comparisons with experimental data, RSM was chosen to further evaluate the characteristics of impinging jets. The Reynolds number based on the jet exit velocity and nozzle diameter is 100 000. Three different nozzle height-to-diameter ratios, representing different types of impinging jets, were simulated and compared with available experimental data. A strong dependency of the jet characteristics on the nozzle height-to-diameter ratio was observed. The simulations show that an increase in this ratio results in larger shear stress and more distributed pressure on the wall, more development of the flow in the axial direction and faster progress of the jet in the wall region. The current simulations present a robust step-by-step computational fluid dynamics approach to investigate the role of the nozzle height-to-diameter ratio on the impinging jet flow parameters.

Model Testing and CFD Analysis of 2D Profiles Towards Offshore Applications

2013 ◽  
Author(s):  
Lucas do Vale Machado ◽  
Antonio Carlos Fernandes ◽  
Gustavo César Rachid Bodstein
Keyword(s):  
Experimental Data ◽  
Experimental Measurements ◽  
Cfd Analysis ◽  
Two Dimensional ◽  
Reference Simulation ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Naca 0015 ◽  
Good Agreement

In this paper we present numerical and experimental work motivated by the study of a rudder profile with significant levels of lift that provides better performance for the maneuvering and stabilization of a ship. This is the so-called Schilling profile. The analysis of the two-dimensional subsonic steady flow over four profiles was carried out using computational fluid dynamics (CFD) tools with a κ-ω SST turbulence model. We consider three Schilling profiles with different thicknesses and the classical NACA 0015 profile, taken as a reference. Simulation results were compared to our experimental measurements at various angles of attack and two orders of magnitude of the Reynolds number, 5.45 × 104 and 1.09 × 105. The numerical results show general good agreement with experimental data and highlight the distinct behavior of Schilling profile.

scholarly journals DESIGN OF DETERMINISTIC MODEL OF SIGNAL TRANSDUCTION BETWEEN NEURONAL CELLS

2015 ◽  
Vol 20 (1) ◽  
pp. 76-93 ◽  
Author(s):  
Maryna A. Hliatsevich ◽  
Pavel M. Bulai ◽  
Taras N. Pitlik ◽  
Andrey A. Denisov ◽  
Sergey N. Cherenkevich
Keyword(s):  
Experimental Data ◽  
Signal Transduction ◽  
Deterministic Model ◽  
Experimental Measurements ◽  
Nonlinear Ordinary Differential Equations ◽  
System Parameters ◽  
The Cauchy Problem ◽  
Synaptic Parameters ◽  
The Given ◽  
Fitting Model

Mathematical model describing signal transduction between neurons has been presented using the system of nonlinear ordinary differential equations. The Cauchy problem for the given system has been solved numerically and system parameters were adjusted to match the results of experimental measurements of extracellular postsynaptic potentials in rat hippocampus slices. While fitting model to the experimental data some values of synaptic parameters have been determined.

External Air Flow Over a Pickup Truck: CFD Modeling and Investigation

2016 ◽  
Author(s):  
Scott Kruepke ◽  
Subha Kumpaty
Keyword(s):  
Drag Coefficient ◽  
Air Flow ◽  
Turbulence Models ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Flow Solver ◽  
Segregated Flow ◽  
Physics Modeling ◽  
The Impact ◽  
Open Position

Pickup trucks offer operators the advantage of towing payload capacity, but at higher operating costs in terms of fuel usage. Some of the increased fuel usage can be attributed to the shape of the truck, which is not aerodynamically advantageous, especially when compared to the other vehicles. This analysis reviews the air flow patterns around a truck during highway travel and uses computational fluid dynamics (CFD) modeling to analyze the best method to predict drag coefficient for the truck. This paper investigates the various mesh features available and the physics models that can be used to approximate the fluid flow, determining the significance of each numerical method. The results indicated that a polyhedral mesh with an incompressible fluid assumption, solved using a segregated flow solver and Reynolds Averaged Navier Stokes k-ε equations provided a suitable balance between accuracy and computational investment when compared to other turbulence models or physics modeling solvers. Further, the analysis investigated the impact on drag of driving the truck with the bed tailgate in the raised, closed position versus driving with the bed tailgate lowered in the open position. The findings actually show that the truck drag coefficient is reduced by about 3% when the truck is operated with the tailgate in the lowered, open position.

Aerodynamic Comparison and Validation of RANS, URANS and SAS Simulations of Flat Plate Film-Cooling

2010 ◽  
Author(s):  
Stefan Voigt ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Film Cooling ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
3 Dimensional ◽  
Commercial Code ◽  
Sst Model ◽  
Rans Models

The present paper deals with the detailed numerical simulation of film cooling including conjugate heat transfer. Five different turbulence models are used to simulate a film cooling configuration. The models include three steady and two unsteady models. The steady RANS models are the Shear stress transport (SST) model of Menter, the Reynolds stress model of Speziale, Sarkar and Gatski and a k-ε explicit algebraic Reynolds stress model. The unsteady models are a URANS formulation of the SST model and a scale-adaptive simulation (SAS). The solver used in this study is the commercial code ANSYS CFX 11.0. The results are compared to available experimental data. These data include velocity and turbulence intensity fields in several planes. It is shown that the steady RANS approach has difficulties with predicting the flow field due to the high 3-dimensional unsteadiness. The URANS and SAS simulations on the other hand show good agreement with the experimental data. The deviation from the experimental data in velocity values in the steady cases is about 20% whereas the error in the unsteady cases is below 10%.

A Comparison of Some Recent Eddy-Viscosity Turbulence Models

1996 ◽  
Vol 118 (3) ◽  
pp. 514-519 ◽  
Author(s):  
F. R. Menter
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Pressure Gradient ◽  
Eddy Viscosity ◽  
State Of The Art ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Gradient Flows ◽  
Grid Convergence ◽  
Sst Model

The performance of recently developed eddy-viscosity turbulence models, including the author’s SST model, is evaluated against a number of attached and separated adverse pressure gradient flows. The results are compared in detail against experimental data, as well as against the standard k-ε model. Grid convergence was established for all computations. The study involves four different, state-of-the-art finite difference (finite volume) codes.

The Impact of Payoff Interdependence on Trust and Trustworthiness

2008 ◽  
Vol 9 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Werner Güth ◽  
M. Vittoria Levati ◽  
Matteo Ploner
Keyword(s):  
Experimental Data ◽  
Convex Combination ◽  
The Other ◽  
The Impact

Abstract In one-shot investment games where each player’s payoff is a convex combination of own and other’s profit, we measure trust by the amount given to the trustee and trustworthiness by the amount returned to the trustor by the trustee. Does the degree of payoff interdependence increase both trust and trustworthiness or one but not the other or neither of them? According to our experimental data, trust remains unaffected by the extent of interdependence whereas trustworthiness reacts positively to it.

Modeling for the Aerodynamics Analysis of the Four Blades Movable Vanes Type Vertical Axis Wind Turbine (VVAWT)

2015 ◽  
Vol 793 ◽  
pp. 338-342
Author(s):  
Kadhim Hussein Suffer ◽  
Ghulam Abdul Quadir ◽  
Khairul Azwan bin Ismail ◽  
Ryspek Uzobomatove
Keyword(s):  
Wind Turbine ◽  
Turbulence Models ◽  
Vertical Axis ◽  
The Other ◽  
Vertical Axis Wind Turbine ◽  
Computational Fluid Dynamics Cfd ◽  
Aerodynamic Parameters ◽  
The Individual ◽  
Better Than ◽  
Good Agreement

The power generated by a Vertical Axis Wind Turbine (VAWT) depends on the drag force generated by the individual blades and interactions between them in a rotating configuration. The present Analysis is on attempt to predict numerically the coefficient of drag and other aerodynamic parameters for a four blade Vane type Vertical Axis Wind Turbine (VVAWT) with different blades and vanes position. For numerical investigation, commercial available computational fluid dynamics CFD software GAMBIT and FLUENT are used. In this numerical analysis the Shear Stress Transport (SST) k-ω turbulence model is used which is better than the other turbulence models available as suggested by some researchers. The computed results show good agreement with published experimental results.

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