Experimental Measurements and Computational Solutions for Aerodynamic Forces on an Ahmed Body at Various Ground Clearances

2003 ◽  
Author(s):  
Ilhan Bayraktar ◽  
Drew Landman ◽  
Tuba Bayraktar
Keyword(s):  
Large Scale ◽  
Bluff Body ◽  
Ground Plane ◽  
Computational Simulation ◽  
Simulation Method ◽  
Full Scale ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Ground Clearance ◽  
Ahmed Body

Reliable computer solutions to external aerodynamic flow fields on road vehicles are extremely desirable to road vehicle designers. In a previous publication a study was performed to validate a Reynolds-averaged unsteady Navier-stokes solution for the aerodynamic characterization of a large-scale bluff body. In the present study, the external aerodynamics of this body as a function of ground clearance are explored. Experimental force measurements are obtained in a full-scale wind tunnel using an Ahmed body model and test conditions representative of full-scale operating conditions. A Reynolds averaged Navier-Stokes solver is employed for computational simulation of the external flowfield at the same conditions. Experimental and computational force coefficients versus vehicle ground clearance are presented for fixed ground, moving ground, and suction slot road simulations. Experimental results using boundary layer suction are compared to computational results with a moving ground plane in order to better understand the effect of a road simulation method.

Steady and Unsteady Modeling for Heat Transfer Predictions of High Pressure Turbine Blade Internal Cooling

2012 ◽  
Author(s):  
Rémy Fransen ◽  
Nicolas Gourdain ◽  
Laurent Y. M. Gicquel
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Cooling System ◽  
Transfer Problem ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Wall Region ◽  
Internal Cooling ◽  
Computational Domain ◽  
Complex Flow

This work focuses on numerical simulations of flows in blade internal cooling system. Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS) approaches are compared in a typical blade cooling related problem. The case is a straight rib-roughened channel with high blockage ratio, computed and compared for both a periodic and full spatial domains. The configuration was measured at the Von Karman Institute (VKI) using Particle Image Velocimetry (PIV) in near gas turbine operating conditions. Results show that RANS models used fail to predict the full evolution of the flow within the channels where massive separation and large scale unsteady features are evidenced. In contrast LES succeeds in reproducing these complex flow motions and both mean and fluctuating components are clearly improved in the channels and in the near wall region. Periodic computations are gauged against the spatial computational domain and results on the heat transfer problem are addressed.

scholarly journals Aerodynamics of an aerofoil in transonic ground effect: Methods for blowdown windtunnel scale testing

2012 ◽  
Vol 116 (1180) ◽  
pp. 599-620 ◽  
Author(s):  
G. Doig ◽  
T. J. Barber ◽  
A. J. Neely ◽  
D. D. Myre
Keyword(s):  
Wind Tunnel ◽  
Ground Plane ◽  
Ground Effect ◽  
Mirror Image ◽  
Navier Stokes ◽  
Oncoming Flow ◽  
Ground Clearance ◽  
Mach Numbers ◽  
Reynolds Averaged Navier Stokes ◽  
Symmetry Method

Abstract Experimental aerodynamic testing of objects in close ground proximity at high subsonic Mach numbers is difficult due to the construction of a transonic moving ground being largely unfeasible. Two simple, passive methods have been evaluated for their suitability for such testing in a small blowdown wind tunnel: an elevated ground plane, and a symmetry (or mirror-image) approach. The methods were examined using an unswept wing of RAE2822 section, with experiments and Reynolds-Averaged Navier Stokes CFD used synergistically to determine the relative merits of the techniques. The symmetry method was found to be a superior approximation of a moving ground in all cases, with mild discrepancies observed only at the lowest ground clearance. The elevated ground plane was generally found to influence the oncoming flow and distort the flowfield between the wing and ground, such that the method provided a less-satisfactory match to moving ground simulations compared to the symmetry technique.

Laminar flow of an incompressible fluid past a bluff body: the separation, reattachment, eddy properties and drag

1979 ◽  
Vol 92 (1) ◽  
pp. 171-205 ◽  
Author(s):  
F. T. Smith
Keyword(s):  
Circular Cylinder ◽  
Large Scale ◽  
Bluff Body ◽  
Reynolds Numbers ◽  
The Body ◽  
Navier Stokes ◽  
Pressure Drag ◽  
Body Scale ◽  
Flow Situation ◽  
Large Scale Flow

The asymptotic theory for the laminar, incompressible, separating and reattaching flow past the bluff body is based on an extension of Kirchhoff's (1869) free-streamline solution. The flow field (only the upper half of which is discussed since we consider a symmetric body and flow) consists of two basic parts. The first is the flow on the body scalel*, which is described to leading order by the Kirchhoff solution with smooth inviscid separation, but with an$O(Re^{-\frac{1}{16}})$modification to explain fully the viscous separation (hereRe([Gt ] 1) is the Reynolds number). The influence of this$O(Re^{-\frac{1}{16}})$modification is determined for the circular cylinder. The second part is the large-scale flow, comprising mainly the eddy and the ultimate wake. The eddy has length scaleO(Rel*), widthO(Re½l*) and is of elliptical shape to keep the eddy pressure almost uniform. The ultimate wake is determined numerically and fixes the eddy length. The (asymptotically small) back pressure from the eddy acts (on the body scale) both in the free stream and in the eddy, and it has a marked effect at moderate Reynolds numbers; combined with the Kirchhoff solution, it predicts the pressure drag on a circular cylinder accurately, to within 10% whenRe= 5 and to within 4% whenRe= 50. Other predictions, for the eddy length and width, the front pressure and the eddy pressure, also show encouraging agreement with experiments and Navier-Stokes solutions at moderate Reynolds numbers (of about 30), both for the circular cylinder and the normal flat plate. Finally, an analysis in the appendix indicates that, in wind-tunnel experiments, the tunnel walls (even if widely spaced) can exert considerable influence on the eddy properties, eventually forcing an upper bound on the eddy width asReincreases instead of theO(l*Re½) growth appropriate to the unbounded flow situation.

scholarly journals Unsteady Flow Structures within a Turbine Rim Seal Cavity in the Presence of Purge Flow—An Experimental and Computational Unsteady Aerodynamics Investigation

Aerospace ◽  
2019 ◽  
Vol 6 (5) ◽  
pp. 60
Author(s):  
Cengiz Camci ◽  
Michael Averbach ◽  
Jason Town
Keyword(s):  
Large Scale ◽  
Computational Study ◽  
Guide Vane ◽  
Computational Simulation ◽  
Unsteady Aerodynamics ◽  
Azimuthal Velocity ◽  
Fast Response ◽  
Navier Stokes ◽  
Rotor Speed ◽  
Nozzle Guide

Flow within the space between the rotor and stator of a turbine disk, and an area referred to as the rim seal cavity, develops azimuthal velocity component from the rotor disk. The fluid within develops unsteady structures that move at a fraction of the rotor speed. A test is designed to measure the number of unsteady structures and the rotational speed at which they are moving in the rim seal cavity of an experimental research rig. Data manipulation was developed to extract the speed, and the numbers of structures present using two fast-response aerodynamic probes measuring static pressure on the surface of the nozzle guide vane (NGV)-side rim seal cavity. A computational study is done to compare measured results to a transient unsteady Reynolds-averaged Navier–Stokes (URANS). The computational simulation consists of eight vanes and ten blades, carefully picked to reduce the error caused by blade vane pitch mismatch and to allow for the structures to develop correctly, and the rim seal cavity to measure the speed and number of the structures. The experimental results found 15 structures moving at 77.5% of the rotor speed, and the computational study suggested 14.5 structures are moving at 81.7% rotor speed. The agreement represents the first known test of its kind in a large-scale turbine test rig and the first known “good” agreement between computational and experimental work.

Study on Three-Dimensional Wind Field Characteristics of Thunderstorm Microbursts Using Computational Fluid Dynamics

2011 ◽  
Vol 243-249 ◽  
pp. 5033-5036
Author(s):  
Bai Feng Ji ◽  
Wei Lian Qu ◽  
Yan Li ◽  
Yi Fei Wang ◽  
Zhong Shan He
Keyword(s):  
Wind Field ◽  
Computational Simulation ◽  
Three Dimensional ◽  
Simulation Method ◽  
Computational Method ◽  
Navier Stokes ◽  
Transmission Tower ◽  
Lower Altitude ◽  
Structural Failures ◽  
Wind Distribution

Thunderstorm microbursts, which are sources of extreme wind loadings in nature, have caused numerous structural failures, especially collapses of transmission tower around the world. It is important to study wind field characteristics of thunderstorm microbusts from the perspective of wind-resistant design. In this paper, the three-dimensional wind field characteristics of thunderstorm microbursts were studied using computational simulation method. Firstly, the three-dimensional wind field of microburst was computational simulated using time-filtered Reynolds Averaged Navier-Stokes (RANS) numerical computational method. Then, the three-dimensional wind field characteristics including the wind distribution of wind velocity at different heights, the wind contours at lower altitude positions were studied in detail. The results indicate that the three-dimensional wind field of microbursts winds presents quite different characteristics at different heights and radial positions.

Experimental and Numerical Investigation of Unsteady Structures Within the Rim Seal Cavity in the Presence of Purge Mass Flow

2016 ◽  
Author(s):  
Jason Town ◽  
Michael Averbach ◽  
Cengiz Camci
Keyword(s):  
Large Scale ◽  
Computational Study ◽  
Computational Simulation ◽  
Azimuthal Velocity ◽  
Fast Response ◽  
Experimental Results ◽  
Test Facility ◽  
Navier Stokes ◽  
State University ◽  
Rotor Speed

Flow within the space between the rotor and stator of a turbine disk, an area referred to as the rim seal cavity, develops azimuthal velocity component from the rotor disk. The fluid within develops unsteady structures that move at a fraction of the rotor speed. A measurement strategy is developed to measure the number of unsteady structures and the rotational speed at which they are moving in the rim seal cavity of an experimental turbine research rig. Data manipulation was developed to extract the speed and the numbers of structures present using two fast response aerodynamic probes measuring static pressure on the surface of the stator side rim seal cavity. A computational study is completed to compare measured results to a transient Unsteady Reynolds Averaged Navier-Stokes (URANS). The computational simulation domain consists of 8 vanes and 10 blades (the full test facility consisted of 29 vanes and 36 blades), carefully picked to reduce error caused by blade vane pitch mismatch and to allow for the structures to develop correctly, and the rim seal cavity to measure the speed and number of the structures. The experimental results found 15 structures moving at 77.5% of the rotor speed, computational results are based on the size of the domain and guidance from the experimental results found 14.5 structures are moving at 81.7% rotor speed. The agreement represents the first known test of its kind and the first known agreement between computational and experimental work performed in the large scale and rotating turbine research facility AFTRF at the Pennsylvania State University.

CFD-Based Hydrodynamic Analysis of High Performance Racing Yachts

2009 ◽  
Author(s):  
Len Imas ◽  
Bryan Baker ◽  
Britton Ward ◽  
Gregory Buley
Keyword(s):  
High Performance ◽  
Large Scale ◽  
Rigid Body Dynamics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Hydrodynamic Analysis ◽  
Efficient Performance ◽  
Body Dynamics ◽  
Free Surface Capturing

Recent development in Navier-Stokes solver technology and meshing techniques have furthered the ability of naval architects and hydrodynamicists to analyze intricate flow simulations of high performance racing yachts. The effect of this development has contributed to enlarging the bounds of the design space aiding in comprehension and optimization of high performance yachts. This paper will present selected examples from a research study based around tow tank tests and CFD simulations of a canonical high-performance racing yacht. The geometry configurations studied were fully appended with rudders, keel/bulb and a dagger-board. Simulations were performed with various operating conditions covering both lifting and non-lifting flow regimes. Topics covered will address (i) validation against tow tank measurements; (ii) efficient performance of large-scale computations; and (iii) numerical issues related to (a) mesh generation, (b) solution, discretization, and free surface capturing algorithms, (c) turbulence modelling, (d) rigid body dynamics and sail force models.

Rotor-Alone Tones in the Outflow Noise of a Centrifugal Compressor

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Armin Faßbender ◽  
Martin Enneking ◽  
Peter Jeschke
Keyword(s):  
Centrifugal Compressor ◽  
Large Scale ◽  
Pressure Fluctuations ◽  
Sound Field ◽  
Operating Conditions ◽  
Mode Analysis ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Fourier Decomposition ◽  
Generation Mechanisms

Abstract This article investigates the generation of rotor-alone tones and their contribution to the outflow noise of a transonic centrifugal compressor stage with vaneless diffuser and volute by means of unsteady full-annulus computational fluid dynamics (CFD) simulations. The aerodynamic field and the generation and propagation of sound were simulated simultaneously using the unsteady Reynolds-averaged Navier–Stokes (URANS) approach of the solver trace and a numerical grid consisting of 170 M cells. To assess the accuracy of the predicted fluctuations, the investigation compares the simulated diffuser flow field to measured flow angles and pressure fluctuations obtained from experiments conducted on a large-scale test rig. The analysis explains the different sound generation mechanisms responsible for tonal components in the acoustic spectrum at the compressor outlet based on the Fourier decomposition of the pressure fluctuations in diffuser and volute. Furthermore, this article analyzes the modal structure of the simulated sound field at the volute outlet by means of a radial mode analysis and discusses the influence of changing operating conditions on the sound power emitted. The analyses reveal that supersonic flow phenomena occurring at choked operating conditions cause a significant increase in noise emissions. Furthermore, the investigation shows that the sound field at the volute outlet is dominated by few low-order modes, a fact that justifies the analysis using methods based on the compressed sensing in future experimental investigations.

scholarly journals Investigation of fungicidal activity of biocides by method of direct contact with test cultures

2018 ◽  
Vol 251 ◽  
pp. 01018 ◽  
Author(s):  
Valeriya Strokova ◽  
Viktoriya Nelyubova ◽  
Marina Rykunova
Keyword(s):  
Direct Contact ◽  
Large Scale ◽  
Fungicidal Activity ◽  
Cost Savings ◽  
Full Scale ◽  
Operating Conditions ◽  
Express Method ◽  
Test Cultures ◽  
Full Scale Testing

The article substantiates the possibility of using the method of direct contact with test cultures as an express method for assessing the quality of biocidal substances. This technique allows to test soluble biocidal preparations, while reducing the time of biocide selection, which eliminates the need for large-scale full-scale testing of structures under real operating conditions, providing cost savings.

Adsorption Isotherm Predictions for Multiple Molecules in MOFs Using the Same Deep Learning Model

2019 ◽  
Author(s):  
Ryther Anderson ◽  
Achay Biong ◽  
Diego Gómez-Gualdrón
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Molecular Simulation ◽  
Large Scale ◽  
Learning Model ◽  
Operating Conditions ◽  
Small Subset ◽  
Screening Methods ◽  
Large Set ◽  
Metal Organic

<div>Tailoring the structure and chemistry of metal-organic frameworks (MOFs) enables the manipulation of their adsorption properties to suit specific energy and environmental applications. As there are millions of possible MOFs (with tens of thousands already synthesized), molecular simulation, such as grand canonical Monte Carlo (GCMC), has frequently been used to rapidly evaluate the adsorption performance of a large set of MOFs. This allows subsequent experiments to focus only on a small subset of the most promising MOFs. In many instances, however, even molecular simulation becomes prohibitively time consuming, underscoring the need for alternative screening methods, such as machine learning, to precede molecular simulation efforts. In this study, as a proof of concept, we trained a neural network as the first example of a machine learning model capable of predicting full adsorption isotherms of different molecules not included in the training of the model. To achieve this, we trained our neural network only on alchemical species, represented only by their geometry and force field parameters, and used this neural network to predict the loadings of real adsorbates. We focused on predicting room temperature adsorption of small (one- and two-atom) molecules relevant to chemical separations. Namely, argon, krypton, xenon, methane, ethane, and nitrogen. However, we also observed surprisingly promising predictions for more complex molecules, whose properties are outside the range spanned by the alchemical adsorbates. Prediction accuracies suitable for large-scale screening were achieved using simple MOF (e.g. geometric properties and chemical moieties), and adsorbate (e.g. forcefield parameters and geometry) descriptors. Our results illustrate a new philosophy of training that opens the path towards development of machine learning models that can predict the adsorption loading of any new adsorbate at any new operating conditions in any new MOF.</div>

Sign in / Sign up

Export Citation Format

Share Document