Joint Computational/Experimental Aerodynamic Study of a Simplified Tractor/Trailer Geometry

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Subrahmanya P. Veluri ◽  
Christopher J. Roy ◽  
Anwar Ahmed ◽  
Rifki Rifki ◽  
John C. Worley ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Test Section ◽  
Bluff Body ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Initial Assessment ◽  
Validation Data ◽  
Data Set ◽  
Fine Mesh

Steady-state Reynolds averaged Navier–Stokes (RANS) simulations are presented for the three-dimensional flow over a generic tractor trailer placed in the Auburn University 3×4 ft2 suction wind tunnel. The width of the truck geometry is 10 in., and the height and length of the trailer are 1.392 and 3.4 times the width, respectively. The computational model of the wind tunnel is validated by comparing the numerical results with the data from the empty wind tunnel experiments. The comparisons include the boundary layer properties at three different locations on the floor of the test section and the flow angularity at the beginning of the test section. Three grid levels are used for the simulation of the truck geometry placed in the test section of the wind tunnel. The coarse mesh consists of 3.4×106 cells, the medium mesh consists of 11.2×106 cells and the fine mesh consists of 25.8×106 cells. The turbulence models used for both the empty tunnel simulations and the truck geometry placed in the wind tunnel are the standard Wilcox 1998 k-ω model, the SST k-ω model, the standard k-ε model, and the Spalart–Allmaras model. The surface pressure distributions on the truck geometry and the overall drag are predicted from the simulations and compared with the experimental data. The computational predictions compared well with the experimental data. This study contributes a new validation data set and computations for high Reynolds number bluff-body flows. The validation data set can be used for initial assessment in evaluating RANS models, which will be used for studying the drag or drag trends predicted by the baseline truck geometries.

scholarly journals 2D Numerical Simulation Study of Airfoil Performance

2021 ◽  
Author(s):  
Nasser Shelil
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Air Temperature ◽  
Wind Turbines ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Ansys Fluent

Abstract. The aerodynamic characteristics of DTU-LN221 airfoil is studied. ANSYS Fluent is used to simulate the airfoil performance with seven different turbulence models. The simulation results for the airfoil with different turbulence models are compared with the wind tunnel experimental data performed under the same operating conditions. It is found that there is a good agreement between the computational fluid dynamics (CFD) predicted aerodynamic force coefficients with wind tunnel experimental data especially with angle of attack between −5° to 10°. RSM is chosen to investigate the flow field structure and the surface pressure coefficients under different angle of attack between −5° to 10°. Also the effect of changing air temperature, velocity and turbulence intensity on lift and drag coefficients/forces are examined. The results show that it is recommended to operate the wind turbines airfoil at low air temperature and high velocity to enhance the performance of the wind turbines.

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.

A three-dimensional model of fine particle retention during percolation through a fiber mat

TAPPI Journal ◽  
2015 ◽  
Vol 14 (8) ◽  
pp. 546-554
Author(s):  
TERRY BLISS ◽  
MARTIN OSTOJA-STARZEWSKI ◽  
JAIME CASTRO
Keyword(s):  
Experimental Data ◽  
Fine Particles ◽  
Fiber Diameter ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Three Dimensional Model ◽  
Retention Model ◽  
Data Set ◽  
Fiber Mats ◽  
Rayon Fiber

Fine particles are usually retained in fiber mats by sieving. To date, no theory has combined fiber and mat characteristics into a predictive retention model. A multilayer analytical retention model developed during this study predicts retention within a thick fiber mat by modeling retention as particles pass through a series of very thin fiber mats. A suspension of 5-75 μm toner particles was percolated through rayon fiber mats. The model’s prediction approached the experimental data only when the ratio of particle diameter to fiber diameter increased toward 2.0, the upper limit within the rayon fiber mat data set. Retention was also experimentally determined on the macroscale with simulated fiber mats, through which 4-20 mm beads were dropped. The particle diameter was at least 2.2 times the fiber diameter for all of the macroscale experimental data, explaining the much better fit of the data from those experiments to the model’s predictions.

Accurate Prediction and Validation of Response to Endocrine Therapy in Breast Cancer

2015 ◽  
Vol 33 (20) ◽  
pp. 2270-2278 ◽  
Author(s):  
Arran K. Turnbull ◽  
Laura M. Arthur ◽  
Lorna Renshaw ◽  
Alexey A. Larionov ◽  
Charlene Kay ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Clinical Response ◽  
Estrogen Receptor Alpha ◽  
Quantitative Polymerase Chain Reaction ◽  
Three Dimensional ◽  
Gene Signature ◽  
Molecular Response ◽  
Cancer Specific Survival ◽  
Validation Data ◽  
Data Set

Purpose Aromatase inhibitors (AIs) have an established role in the treatment of breast cancer. Response rates are only 50% to 70% in the neoadjuvant setting and lower in advanced disease. Accurate biomarkers are urgently needed to predict response in these settings and to determine which individuals will benefit from adjuvant AI therapy. Patients and Methods Pretreatment and on-treatment (after 2 weeks and 3 months) biopsies were obtained from 89 postmenopausal women who had estrogen receptor–alpha positive breast cancer and were receiving neoadjuvant letrozole for transcript profiling. Dynamic clinical response was assessed with use of three-dimensional ultrasound measurements. Results The molecular response to letrozole was characterized and a four-gene classifier of clinical response was established (accuracy of 96%) on the basis of the level of two genes before treatment (one gene [IL6ST] was associated with immune signaling, and the other [NGFRAP1] was associated with apoptosis) and the level of two proliferation genes (ASPM, MCM4) after 2 weeks of therapy. The four-gene signature was found to be 91% accurate in a blinded, completely independent validation data set of patients treated with anastrozole. Matched 2-week on-treatment biopsies were associated with improved predictive power as compared with pretreatment biopsies alone. This signature also significantly predicted recurrence-free survival (P = .029) and breast cancer –specific survival (P = .009). We demonstrate that the test can also be performed with use of quantitative polymerase chain reaction or immunohistochemistry. Conclusion A four-gene predictive model of clinical response to AIs by 2 weeks has been generated and validated. Deregulated immune and apoptotic responses before treatment and cell proliferation that is not reduced 2 weeks after initiation of treatment are functional characteristics of breast tumors that do not respond to AIs.

Experimental and Numerical Investigation of Stationary Ribbed Ducts

2004 ◽  
Author(s):  
A. Magi ◽  
F. Montomoli ◽  
P. Adami ◽  
C. Carcasci
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Cfd Simulation ◽  
Low Cost ◽  
Turbulence Models ◽  
Data Set ◽  
Contour Maps ◽  
Accuracy Level ◽  
Coolant System ◽  
Good Agreement

Goal of this work is to define the main issues and guidelines for an accurate heat transfer CFD simulation of internal ribbed ducts. To this aim, two different ribbed ducts (AR = 1,3) have been experimentally investigated to obtain a data set useful to validate numerical analyses. Experimental HTC contour maps have been obtained using unsteady TLC technique. CFD activity deals with numerical simulation using both a commercial (Star-CD™) and an “in house” solver (HybFlow). Four different variants of the well-known two-equation turbulence models have been considered. Low cost heat transfer predictions of internal ducts are highly demanded by industry despite the uncommon complexity of modern internal coolant system. Accordingly, the main aim of the work is to provide some indications for the numerical modelling and to evaluate the accuracy level of predicted heat transfer when commercial or research packages are employed along with different grid resolution levels. Overall results are in good agreement with experimental data even if some local discrepancies are present.

scholarly journals Undesirable Flow Behavior in a Proposed Validation Data Set

2010 ◽  
Author(s):  
Richard W. Johnson ◽  
Hugh M. McIlroy ◽  
Ryan C. Johnson ◽  
Daniel P. Christensen
Keyword(s):  
Experimental Data ◽  
Recirculation Zone ◽  
Flow Behavior ◽  
National Laboratory ◽  
Index Of Refraction ◽  
Department Of Energy ◽  
Computational Domain ◽  
Scaled Model ◽  
Validation Data ◽  
Data Set

The next generation nuclear plant (NGNP), whose development is supported by the U. S. Department of Energy, will be a very high temperature reactor (VHTR). The VHTR is a single-phase helium-cooled reactor that will provide helium at up to 800 °C. The prospect of a coolant at these temperatures circulating in the reactor vessel demands that careful analysis be performed to ensure that excessively hot spots are not created and that sufficient mixing of the coolant is obtained. Computational fluid dynamics (CFD) coupled with heat transfer will be used to perform the desired analyses. However, primarily because of the imperfect nature of modeling turbulent flow, any CFD calculations used to perform nuclear reactor safety analysis must be validated against experimental data. Experimental data have been taken in a scaled section of the lower plenum of a prismatic VHTR at the matched index of refraction (MIR) facility at the Idaho National Laboratory. These data were taken with the intent that they be examined for use as validation data. A series of investigations have been conducted to assess the MIR data. Issues that have already been examined include the extent of the required computational domain, the outlet boundary condition, the inlet data and the effect of the turbulence model. One of the jets that flow into the model impacts on a wedge, which represents a portion of a hexagonal graphite block that is part of the inner wall of the lower plenum. The nature of the flow below this particular jet is such that a randomly varying recirculation zone is created. This recirculation zone is seen to change in size, causing a relatively long-time scale of motion or disturbance on the flow downstream. It is concluded that such a feature is undesirable in a validation data set, firstly because of its apparent random nature and, secondly, because to obtain an appropriate longtime average would be impractical because of the compute time required. It is found that by eliminating the first of the four inlet jets into the scaled model, the resulting recirculation zone is rendered stable.

Study of Turbulence Models in Flows Through Adverse Pressure Gradient System

2005 ◽  
Author(s):  
E. Karunakaran ◽  
V. Ganesan
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Gradient ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Gradient System ◽  
Field Development

This paper is concerned with the study of performance of popular turbulence models used in the CFD analysis. Turbulence models considered for evaluation include the eddy viscosity models and the Reynolds stress model. The recent k-ε-v2-f model recommended for a flow with separation is also studied. Evaluation of the turbulence models in the present study focuses on a three-dimensional flow field development with adverse pressure gradient and flows that simulate wall-bounded turbulence. Numerical calculations are performed using SIMPLE based algorithm. Nowadays, decelerating flow in a diffuser is assessed by numerical simulations and the validation is done with experimental results. A comparison of the numerical results and the experimental data are presented. The main objective of the comparison is to obtain information on how well the numerical simulations representing the flow field with the standard turbulence models, are able to reproduce the experimental data.

The Effect of the Source Location on the Acoustic Excitation on Laminar-Turbulent Transition on Swept Wing Boundary Layer

2002 ◽  
Author(s):  
B. Gu¨lac¸ti ◽  
S. Aubrun ◽  
A. Seraudie ◽  
D. Arnal
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Three Dimensional ◽  
Source Location ◽  
Sound Level ◽  
Acoustic Excitation ◽  
Hot Wire ◽  
Swept Wing ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition

The effect of the source location and the direction of the propagation on the laminar-turbulent transition on swept-wing three-dimensional boundary layers are investigated experimentally. Also the crossflow case is handled in detail. The source for the acoustic excitation is placed in four different locations: in front of the wing, on top of the test section, behind the wing and in front of the wind tunnel. Three different experimental cases (streamwise, crossflow and mixed cases) are examined for each location with two different excitation bands. For the most efficient frequency ranges and the highest sound pressure levels an upstream shift of transition motion between 20%–35% of chord length for streamwise case and between 5%–10% for the crossflow case are observed. While in front of the wing and behind the wing are the most efficient loudspeaker positions in the streamwise case, in the crossflow case the most efficient locations are observed to be in front of the wing and on top of the test section. It is concluded that acoustic sound level plays a more important role in the upstream shift of the transition than the source location and placing the loudspeaker in front of the wind tunnel is not an efficient position. For the crossflow instabilities dominated transition the stationary vortices are clearly seen from the velocity contours obtained by the hot-wire. Secondary instabilities couldn’t be observed in the hot-wire spectra. The surface roughness of the wing that is reduced to 0.25µm does not change the transition location in the crossflow case.

Validation of CFD simulations for X-31 wind-tunnel models

2015 ◽  
Vol 119 (1214) ◽  
pp. 479-500 ◽  
Author(s):  
M. Ghoreyshi ◽  
A. D. H. Kim ◽  
A. Jirasek ◽  
A. J. Lofthouse ◽  
R. M. Cummings
Keyword(s):  
Wind Tunnel ◽  
Aerodynamic Force ◽  
Numerical Algorithms ◽  
Turbulence Models ◽  
Leading Edge ◽  
Convergence Acceleration ◽  
Cfd Simulations ◽  
Data Set ◽  
Cfd Models ◽  
Sinusoidal Oscillations

AbstractComputational Fluid Dynamics (CFD) has become an attractive method of choice in the design of many aerospace vehicles because of advances in numerical algorithms and convergence acceleration methods. However, the flow around an advanced fighter aircraft is complicated and usually unsteady due to the presence of vortex-dominated flows. The accuracy and predictability of conventional turbulence models for these applications may be questionable and therefore results obtained from these models must be validated and evaluated on the basis of experimental data from wind tunnels and/or flight tests. This work aims to validate CFD simulations of X-31 wind-tunnel models with and without a belly-mounted sting. The sting setup facilitates forced sinusoidal oscillations in one of three modes of: pitch, yaw, and roll. However, the results show that measured aerodynamic data are altered by the turbulent wake behind the sting, even at small angles of attack. The high angle-of-attack flow around the X-31 is also very complicated and unsteady due to canard and wing vortices. Therefore, validation of CFD models for predicting these complex flows can be a very challenging task. The X-31 wind-tunnel experiments were carried out in the German Dutch low-speed wind tunnel at Braunschweig and include aerodynamic force and moment measurement as well as span-wise pressure distributions at locations of 60% and 70% chord length. This data set is used to validate the Cobalt and Kestrel flow solvers and the results are similar and match quiet well with experiments for small to moderate angles of attack. The main discrepancies between CFD and measurements occur close to the wing tip, where leading-edge flaps are located.

scholarly journals Three-dimensional Lagrangian Voronoï analysis for clustering of particles and bubbles in turbulence

2012 ◽  
Vol 693 ◽  
pp. 201-215 ◽  
Author(s):  
Yoshiyuki Tagawa ◽  
Julián Martínez Mercado ◽  
Vivek N. Prakash ◽  
Enrico Calzavarini ◽  
Chao Sun ◽  
...  
Keyword(s):  
Experimental Data ◽  
Isotropic Turbulence ◽  
Response Times ◽  
Three Dimensional ◽  
Voronoi Cell ◽  
Reynolds Numbers ◽  
Point Particle ◽  
Heavy Particles ◽  
Data Set ◽  
Light Particles

AbstractThree-dimensional Voronoï analysis is used to quantify the clustering of inertial particles in homogeneous isotropic turbulence using data sets from numerics in the point particle limit and one experimental data set. We study the clustering behaviour at different density ratios, particle response times (i.e. Stokes numbers $\mathit{St}$) and two Taylor–Reynolds numbers (${\mathit{Re}}_{\lambda } = 75$ and 180). The probability density functions (p.d.f.s) of the Voronoï cell volumes of light and heavy particles show different behaviour from that of randomly distributed particles, i.e. fluid tracers, implying that clustering is present. The standard deviation of the p.d.f. normalized by that of randomly distributed particles is used to quantify the clustering. The clustering for both light and heavy particles is stronger for higher ${\mathit{Re}}_{\lambda } $. Light particles show maximum clustering for $\mathit{St}$ around 1–2 for both Taylor–Reynolds numbers. The experimental data set shows reasonable agreement with the numerical results. The results are consistent with previous investigations employing other approaches to quantify the clustering. We also present the joint p.d.f.s of enstrophy and Voronoï volumes and their Lagrangian autocorrelations. The small Voronoï volumes of light particles correspond to regions of higher enstrophy than those of heavy particles, indicating that light particles cluster in higher vorticity regions. The Lagrangian temporal autocorrelation function of Voronoï volumes shows that the clustering of light particles lasts much longer than that of heavy or neutrally buoyant particles. Due to inertial effects arising from the density contrast with the surrounding liquid, light and heavy particles remain clustered for much longer times than the flow structures which cause the clustering.

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