A Computational Study of the Flow Around an Isolated Wheel in Contact With the Ground

2005 ◽  
Vol 128 (3) ◽  
pp. 520-530 ◽  
Author(s):  
James McManus ◽  
Xin Zhang
Keyword(s):  
Computational Study ◽  
Experimental Results ◽  
Navier Stokes ◽  
Flow Structures ◽  
Road Vehicles ◽  
Accurate Representation ◽  
Drag Forces ◽  
Mechanisms Of Formation ◽  
Lift And Drag ◽  
Good Agreement

The flow around an isolated wheel in contact with the ground is computed by the Unsteady Reynolds-Averaged Navier-Stokes (URANS) method. Two cases are considered, a stationary wheel on a stationary ground and a rotating wheel on a moving ground. The computed wheel geometry is a detailed and accurate representation of the geometry used in the experiments of Fackrell and Harvey. The time-averaged computed flow is examined to reveal both new flow structures and new details of flow structures known from previous experiments. The mechanisms of formation of the flow structures are explained. A general schematic picture of the flow is presented. Surface pressures and pressure lift and drag forces are computed and compared to experimental results and show good agreement. The grid sensitivity of the computations is examined and shown to be small. The results have application to the design of road vehicles.

Influence of wing kinematics on aerodynamic performance in hovering insect flight

2007 ◽  
Vol 594 ◽  
pp. 341-368 ◽  
Author(s):  
FRANK M. BOS ◽  
D. LENTINK ◽  
B. W. VAN OUDHEUSDEN ◽  
H. BIJL
Keyword(s):  
Insect Flight ◽  
Fruit Fly ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Insect Wing ◽  
Wing Kinematics ◽  
Drag Forces ◽  
Kinematic Models ◽  
Characteristic Features ◽  
Lift And Drag

The influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied.The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.

Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

2022 ◽  
pp. 147509022110707
Author(s):  
Ugur Can ◽  
Sakir Bal
Keyword(s):  
High Speed ◽  
Full Scale ◽  
Navier Stokes ◽  
Drag Forces ◽  
Fluid Body ◽  
Unsteady Rans ◽  
Lift Forces ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Model Family

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

Numerical Investigation of Unsteady Incompressible 3D Turbulent Flow and Torque Transmission in Fluid Couplings

1994 ◽  
Author(s):  
L. Bal ◽  
A. Kost ◽  
M. Fiebig ◽  
N. K. Mitra
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Flow Structures ◽  
Optimized Design ◽  
Navier Stokes Equations ◽  
Reference Flow ◽  
Torque Transmission ◽  
Adequate Understanding ◽  
Volume Method ◽  
Good Agreement

The adequate understanding of the flow structure in fluid couplings is necessary for the optimized design of such devices. Up to now, empiricism plays an important role in design. Detailed studies of the unsteady 3D flow and torque transmission in fluid couplings were rarely carried out. In this paper the unsteady Reynolds time-averaged Navier-Stokes equations coupled with the k-ε model have been solved by a finite-volume method. The calculations were done by using boundary-fitted grids with non-staggered variable arrangement for a rotating frame of reference. Flow structures in fluid couplings were obtained. The results give insights into the physical process of torque transmission. A comparsion of the calculated torque transimission with the experimental measurements in the literature shows good agreement for low slip.

The Influence of Wing Span and Angle of Attack on Racing Car Wing/Wheel Interaction Aerodynamics

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Sammy Diasinos ◽  
Tracie J. Barber ◽  
Graham Doig
Keyword(s):  
Angle Of Attack ◽  
Ground Effect ◽  
Navier Stokes ◽  
Flow Structures ◽  
Wing Span ◽  
Complex Interactions ◽  
Lift And Drag ◽  
Two Bodies ◽  
Wing In Ground Effect

A numerical-based (Reynolds-averaged Navier–Stokes (RANS)) investigation into the role of span and wing angle in determining the performance of an inverted wing in ground effect located forward of a wheel is described, using a generic simplified wheel and NACA 4412 geometry. The complex interactions between the wing and wheel flow structures are investigated to explain either increases or decreases for the downforce and drag produced by the wing and wheel when compared to the equivalent body in isolation. Geometries that allowed the strongest primary wing vortex to pass along the inner face of the wheel resulted in the most significant reductions in lift and drag for the wheel. As a result, the wing span and angle combination that would produce the most downforce, or least drag, in the presence of the wheel does not coincide with what would be assumed if the two bodies were considered only in isolation demonstrating the significance of optimizing these two bodies in unison.

Numerical Analysis of Flow Over the NASA Common Research Model Using the Academic Computational Fluid Dynamics Code Galatea

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Analysis ◽  
Computational Study ◽  
Research Model ◽  
Drag Forces ◽  
Efficient Prediction ◽  
Wind Tunnel Data ◽  
Computational Fluid Dynamics Cfd ◽  
Lift And Drag

A recently developed academic computational fluid dynamics (CFD) code, named Galatea, is used for the computational study of fully turbulent flow over the NASA common research model (CRM) in a wing-body configuration with and without horizontal tail. A brief description of code's methodology is included, while attention is mainly directed toward the accurate and efficient prediction of pressure distribution on wings' surfaces as well as of computation of lift and drag forces against different angles of attack, using an h-refinement approach and a parallel agglomeration multigrid scheme. The obtained numerical results compare close with both the experimental wind tunnel data and those of reference solvers.

Study of Flow and Thrust in Nozzle-Flapper Valves

1975 ◽  
Vol 97 (1) ◽  
pp. 39-50 ◽  
Author(s):  
S. Hayashi ◽  
T. Matsui ◽  
T. Ito
Keyword(s):  
Approximate Formula ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Relaxation Method ◽  
Experimental Results ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vena Contracta ◽  
Radial Gap ◽  
Good Agreement

The Navier-Stokes equations and the equation of continuity describing the flow in the flat-faced nozzle-flapper valve are numerically solved by the iterative relaxation method and the effect of the flow contraction (vena contracta) occurring in the radial gap in the valve is investigated. Furthermore, an approximate formula for the flow force acting on the flapper is derived on the basis of the numerical solutions. The formula for the flow force is in good agreement with experimental results.

Experimental Force Coefficients for a Parametric Series of Spinnakers

2003 ◽  
Author(s):  
William C. Lasher ◽  
James R. Sonnenmeier ◽  
David R. Forsman ◽  
Cheng Zhang ◽  
Kenton White
Keyword(s):  
Aspect Ratio ◽  
Thrust Force ◽  
Statistical Design ◽  
Navier Stokes ◽  
Statistical Design Of Experiments ◽  
Force Coefficient ◽  
Force Coefficients ◽  
Drag Forces ◽  
Parametric Series ◽  
Lift And Drag

A parametric series of eight spinnaker models was built and tested in a wind tunnel according to the theory of statistical Design of Experiments. In these models, three sail shape parameters were varied - cross section camber ratio, sail aspect ratio, and sweep. Lift and drag forces were measured for a range of angles of attack, and the thrust force coefficient was determined as a function of apparent wind angle for each of the eight sails. It was found that flat spinnakers are faster than full spinnakers and that spinnakers with low sweep (more vertical) are faster than spinnakers with high sweep. This is consistent with general sailing practice, which maximizes projected sail area by pulling the pole back and down. The influence of aspect ratio on drag coefficient was small and within experimental error. A description of the sail shapes and corresponding force coefficients is presented for future validation of Reynolds Averaged Navier-Stokes simulations.

Turbulent fluid-structure interaction of water-entry/exit of a rotating circular cylinder using SPH method

2015 ◽  
Vol 26 (08) ◽  
pp. 1550088 ◽  
Author(s):  
Jafar Ghazanfarian ◽  
Roozbeh Saghatchi ◽  
Mofid Gorji-Bandpy
Keyword(s):  
Circular Cylinder ◽  
Water Entry ◽  
Numerical Code ◽  
Navier Stokes ◽  
Inertia Force ◽  
Entry And Exit ◽  
Sph Method ◽  
Drag Forces ◽  
Rotating Circular Cylinder ◽  
Lift And Drag

This paper studies the two-dimensional (2D) water-entry and exit of a rotating circular cylinder using the Sub-Particle Scale (SPS) turbulence model of a Lagrangian particle-based Smoothed-Particle Hydrodynamics (SPH) method. The full Navier–Stokes (NS) equations along with the continuity have been solved as the governing equations of the problem. The accuracy of the numerical code is verified using the case of water-entry and exit of a nonrotating circular cylinder. The numerical simulations of water-entry and exit of the rotating circular cylinder are performed at Froude numbers of 2, 5, 8, and specific gravities of 0.25, 0.5, 0.75, 1, 1.75, rotating at the dimensionless rates of 0, 0.25, 0.5, 0.75. The effect of governing parameters and vortex shedding behind the cylinder on the trajectory curves, velocity components in the flow field, and the deformation of free surface for both cases have been investigated in detail. It is seen that the rotation has a great effect on the curvature of the trajectory path and velocity components in water-entry and exit cases due to the interaction of imposed lift and drag forces with the inertia force.

scholarly journals Prediction of Turbulent Flow Around a Square Cylinder With Rounded Corners

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
S. S. Dai ◽  
B. A. Younis ◽  
H. Y. Zhang
Keyword(s):  
Turbulent Flow ◽  
Vortex Shedding ◽  
Turbulence Closure ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Mean Flow ◽  
Drag Forces ◽  
Turbulence Closures ◽  
High Reynolds ◽  
Lift And Drag

Predictions are reported of the two-dimensional turbulent flow around a square cylinder with rounded corners at high Reynolds numbers. The effects of rounded corners have proved difficult to predict with conventional turbulence closures, and hence, the adoption in this study of a two-equation closure that has been specifically adapted to account for the interactions between the organized mean-flow motions due to vortex shedding and the random motions due to turbulence. The computations were performed using openfoam and were validated against the data from flows past cylinders with sharp corners. For the case of rounded corners, only the modified turbulence closure succeeded in capturing the consequences of the delayed flow separation manifested mainly in the reduction of the magnitude of the lift and drag forces relative to the sharp-edged case. These and other results presented here argue in favor of the use of the computationally more efficient unsteady Reynolds-averaged Navier-Stokes approach to this important class of flows provided that the effects of vortex shedding are properly accounted for in the turbulence closure.

An analysis of aerodynamic forces on a delta wing

1996 ◽  
Vol 316 ◽  
pp. 173-196 ◽  
Author(s):  
Chien-Cheng Chang ◽  
Sheng-Yuan Lei
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Delta Wing ◽  
Leading Edge ◽  
Navier Stokes ◽  
Flow Structures ◽  
Aerodynamic Forces ◽  
Navier Stokes Equations ◽  
Lift And Drag ◽  
Secondary Vortices

The present study aims at relating lift and drag to flow structures around a delta wing of elliptic section. Aerodynamic forces are analysed in terms of fluid elements of non-zero vorticity and density gradient. The flow regime considered is Mα = 0.6 ∼ 1.8 and α = 5° ∼ 19°, where Mα denotes the free-stream Mach number and α the angle of attack. Let ρ denote the density, u velocity, and ω vorticity. It is found that there are two major source elements Re(x) and Ve(x) which contribute about 95% or even more to the aerodynamic forces for all the cases under consideration, \[R_e({\bm x})=-\frac{1}{2} {\bm u}^2 \nabla\rho \cdot \nabla\phi\quad {\rm and}\quad V_e ({\bm x}) = -\rho{\bm u}\times {\bm \omega}\cdot \nabla\phi,\] where θ is an acyclic potential, generated by the delta wing moving with unit velocity in the negative direction of the force (lift or drag). All the physical quantities are non-dimensionalized. Detailed force contributions are analysed in terms of the flow structures and the elements Re(x) and Ve(x). The source elements Re(x) and Ve(x) are concentrated in the following regions: the boundary layer in front of (below) the delta wing, the primary and secondary vortices over the delta wing, and a region of expansion around the leading edge. It is shown that Ve(x) due to vorticity prevails as the source of forces at relatively low Mach number, Mα < 0.7. Above about Mα = 0.75, Re(x) due to compressibility generally becomes the dominating contributor to the lift, while the overall contribution from Ve(x) decreases with increasing Mα, and even becomes negative at Mα = 1.2 for the lift, and at a higher Mα for the drag. The analysis is carried out with the aid of detailed numerical results by solving the Reynolds-averaged Navier–Stokes equations, which are in close agreement with experiments in comparisons of the surface pressure distributions.

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