Aerodynamic forces on bicycle racing wheels were investigated experimentally in a wind tunnel facility at the University of Calgary. The main geometric parameters investigated were the tire sidewall width, ( 21.40 mm ≤ T ≤ 26.15 mm ), rim depth, ( 55 mm ≤ D ≤ 90 mm ), rim width, ( 19.28 mm ≤ W ≤ 25.75 mm ), and angle of attack, ( 0 deg ≤ ψ ≤ 12.6 deg ). A total of six wheels and five tires were tested. Coefficient of drag area ( C d A ) and coefficient of side force area ( C s A ) versus angle of attack (ψ) were measured using a multi-axis force transducer. Wind tunnel conditions were set to simulate 2.94 m/s (6.6 mph) wind speeds and 13.4 m/s (30 mph) cyclist speeds. The performance of the wheel tire combinations was assessed using a wind-averaged drag method. The results show that the C d A of aerodynamic wheels is highly dependent on the wheel-tire combination. There is a strong linear correlation between wind averaged drag ( C d A ¯ ) and the ratio of the tire and rim width ( T / W ) . The C s A of wheels is primarily controlled by the rim depth (D) and only weakly correlated with tire width (T).

Mathematical model of oil flow in fluid film bearing in field of centrifugal forces is developed. Centrifugal forces for planet wheel bearing sliding surfaces and oil gap are formulated. This model is based on modification of two-dimensional Reynolds equation taking into account inertia centrifugal forces for oil film. Required modification of Reynolds equation is received from Navier–Stokes and continuity equations taking into account centrifugal forces acting on planet wheel bearing. Modified two-dimensional Reynolds equation is solved numerically using finite element discretization. Developed mathematical model, based on modified Reynolds equation, is verificated at comparison with solution of full Navier–Stokes equations system obtained in commercial software package. Results for pressure distribution in bearing with fixed axis and in planet wheel bearing are received and compared. The sufficient influence of centrifugal inertia forces in oil layer of planet wheel bearing on pressure distribution, bearing carrying force, and attitude angle is shown for specific shaft journal eccentricity ratio, eccentricity direction, and rotation velocity.

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.

In this work, we have studied how gas accumulates in an industrial centrifugal pump under various steady-state two-phase flow conditions. Thereby, we considered both horizontal and vertical pump installation positions. Phase fractions within the impeller region of the pump have been quantitatively disclosed using high-resolution gamma-ray computed tomography (HireCT) and applying time-averaged rotation-synchronized CT scanning technique. The study was made for inlet volumetric gas flow rates between 0% and 5%. To account for different inlet flow conditions, which are assumed to occur during unwanted gas entrainment by hollow vortices, we produced disperse and swirling gas–liquid inlet flows. In this way, the influence of inlet flow boundary conditions on the pump performance as well as gas fraction distributions and gas holdup within the impeller wheel region could be successfully analyzed and compared with respect to the impeller alignment. It was shown that the installation position offers only a minor effect on the pump performance in comparison to the inlet flow conditions. In addition, for the first time, thin gas films at the pressure side of the impeller wheel blades could be visualized in an industrial centrifugal pump.

This paper deals with a computational fluid dynamics (CFD) and experimental drag analysis on an isolated rotating wheel subsystem (including its accessories: tire, suspension, A-arms, and fender) of a motor tricycle vehicle with two wheels in front. The main goal of the present work is to study the effect of the fender on the wheel subsystem drag and its optimization. The Star CCM+ commercial code was used for the numerical simulations. Different flow conditions were simulated and some results were validated by comparison to wind tunnel experimental results. To perform drag optimization, several aerodynamic fender shapes were designed and simulated as part of the subsystem. A drastic drag reduction up to 30.6% compared to the original wheel subsystem was achieved through numerical simulations.

The flowfield around a 60% scale rotating Formula 1 tire in contact with the ground in a closed wind tunnel at a Reynolds number of 500,000 was examined computationally and experimentally. The goal of this study was to assess the accuracy of unsteady Reynolds-averaged Navier–Stokes (URANS) equations and confirm the existence of large scale vortical and flow recirculating features. A replica deformable F1 tire model that includes four tire treads and all brake components was used to determine the sensitivity of the wake to cross flow within the tire hub as well as the flow blockage caused by the brake assembly. Several turbulence closures were employed and the one that matched closest to the experimental PIV data was the Reynolds stress model. The variability between the six turbulence closures is shown by comparing velocity profiles, pressure distributions, and vortex eccentricity. The sensitivity of the wake to four different hub geometries, contact patch boundary conditions, multiple reference frame (MRF) rotor and spoke treatment, and time step size are also discussed.

Three-dimensional steady and unsteady (pulsating) compressible flows in a vane-less turbocharger turbine of a 1.7 liter SI engine are simulated numerically, and the results are validated experimentally using a turbocharged on-engine test cell. Simulations are carried out for a 720° engine cycle at three engine speeds, and the complete forms of volute and rotor vanes are modeled. Two ways for modeling the rotating wheel, multiple reference frames (MRF), and sliding mesh (SM) techniques are also examined. Finally, the effects of pulsating flow on the turbocharger turbine performance parameters (TTPP) such as the inlet static pressure, reduced mass flow rate, and efficiency are obtained and compared with their values under steady flow. The results show that the accuracy of steady characteristic map to estimate the TTPPs has some source of ambiguity, which should be considered for detailed analysis. TTPP values under steady flow conditions are found to be significantly deviated from the unsteady results. These deviations are decreased as the engine speed increases.

The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel at a Reynolds number of 500,000 was computationally examined in order to assess the accuracy of different turbulence modeling techniques and confirm the existence of large scale flow features. A simplified and replica tire model that includes all brake components was tested to determine the sensitivity of the wake to cross flow within the tire hub along with the flow blockage caused by the brake assembly. The results of steady and unsteady Reynolds averaged Navier-Stokes (URANS) equations and a large eddy simulation (LES) were compared with the experimental data. The LES closure and the RANS closure that accounted for unsteadiness with low eddy viscosity (unsteady kω-SST) matched closest to the experimental data both in point wise velocity comparisons along with location and intensity of the strong counter-rotating vortex pair dominating the far wake of the tire.

The performance of a semiracing spoked wheel is numerically and experimentally studied at full size in a wind tunnel. The numerical investigation is divided into two parts. In the first part, the wheel is considered to be fixed (no rotation) and the numerical results are compared to the experimental measurements. The flow past the wheel is treated as stationary and turbulent. The effects of cross wind and the wheel’s speed on the drag, side force, and yaw moment are investigated. Numerical results are presented via diagrams and plots at various yaw angles. Both the measurements and predictions agree quite well and they show a considerable increase in the yaw moment and side force at medium and high yaw angles. The axial drag force initially increases with yaw angle (up to 7.5 deg) and eventually decreases. Ground effects did not affect the overall loads, except for the vertical force at high yaw angles. In the second part, the effects of rotation have been taken into account. The wheel rotates at constant angular velocities and the flow is modeled as nonstationary and turbulent. The aerodynamic performance of the wheel is strongly affected by the rotational speed. In most of the cases, as the latter parameter increases, the loads nonlinearly increase. The rotation generates asymmetrical loading, since the flow is accelerated in one side and decelerated in the other (the Magnus effect). A vertical force is produced, which is dependent on the ratio of the rotational to the free-stream speed. Moreover, in an attempt to assess the effects of the number of spokes to the aerodynamic performance, two other models with 8 and 32 spokes have been numerically tested and compared to the original one (16 spokes). The results revealed, as expected, an increase in the axial drag and vertical force with the number of spokes.

The flow around generic wheels in wheel housings used in previous experimental investigations is studied using large eddy simulations (LES). A comparison is given here of the results of the simulations with existing experimental data and previous results of RANS simulations. Both instantaneous and time-averaged flows are described, showing agreement with previous knowledge and adding new insight in flow physics. Two different widths of the wheel housing are used in the simulations, and their influence on the flows is studied. The present work shows that the width of the wheel housing has an influence on flows on both the inside and the outside of the wheelhouse.

A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example.

The fundamental aerodynamic influence of downstream wheels on a front wing flow field and vice versa has been investigated using generic wind tunnel models. The research has been conducted using a wing with a fixed configuration, whereas the wing ride height with respect to the ground has been varied as the primary variable. The overlap and gap between the wing and wheels have been kept constant within the context of the current paper. At higher ride heights the wheels reduce wing downforce and increase wing drag, whereas the drag of the wheels themselves also rises. At low ride heights, however, the opposite happens and the wing performance improves, while the wheels produce less drag. The ride height range has been subdivided into force regions with consistent characteristics throughout each of them. Force and pressure measurements, particle image velocimetry results, and oil flow images have been used to explain the differences between the force regions and to derive the governing flow mechanisms. The trajectories and interaction of vortices play a dominant role in the observed force behavior, both as force enhancing and reducing mechanisms. The effect of wheel circulation, flow separation, and flow channeling by the ground and by the wheels are among the other main contributors that have been discussed within this paper.

A comprehensive investigation was carried out using two different experimental setups: A 1.5-stage axial turbine and a simplified model, a “spoked-wheel” setup with a rotating wake generator consisting of cylindrical bars. The second stator of the turbine was designed at MTU Aero Engines as a high-lift profile with a Reynolds number typical for low-pressure turbines in jet engines. At design conditions, the flow on the stator 2 suction side features a pronounced separation bubble. To study the behavior of the stator 2 boundary layer and the interaction mechanisms between stator and rotor wakes, different measurement techniques were used: X-wire probes, five-hole probes, static pressure tappings, and surface mounted hot-film gauges. It was found that a rotating wake generator of the spoked-wheel type is not capable of resolving the relevant clocking mechanisms that occur in a real engine. However, such a simplified setup is useful to separate some of the physical mechanisms, and in case that the interaction of the stator 1 wakes with the stator 2 boundary layer is negligible, a spoked-wheel setup is well suited to simulate the influence of periodically incoming wakes on the transition behavior of stator 2.

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.

The flow around a generic airliner landing-gear truck is calculated using the methods of Detached-Eddy Simulation, and of Unsteady Reynolds-Averaged Navier-Stokes Equations, with the Spalart-Allmaras one-equation model. The two simulations have identical numerics, using a multi-block structured grid with about 2.5 million points. The Reynolds number is 6 × 10 5 . Comparison to the experiment of Lazos shows that the simulations predict the pressure on the wheels accurately for such a massively separated flow with strong interference. DES performs somewhat better than URANS. Drag and lift are not predicted as well. The time-averaged and instantaneous flow fields are studied, particularly to determine their suitability for the physics-based prediction of noise. The two time-averaged flow fields are similar, though the DES shows more turbulence intensity overall. The instantaneous flow fields are very dissimilar. DES develops a much wider range of unsteady scales of motion and appears promising for noise prediction, up to some frequency limit.

A numerical algorithm is developed for a detailed 3D simulation of the two-phase flow field in fluid-energy mills used for pulverization and drying of fossil fuels in large power plants. The gas phase equations are solved using finite differences and the control volume method, whereas a Lagrangian formulation with a stochastic particle dispersion model is adopted for the particulate phase. Fluid-particle interaction is taken into account to calculate the mass, momentum, and heat transfer between phases. Advanced numerical techniques for partially-blocked cells and local grid refinement have been utilized to achieve an accurate representation of the domain geometry and to enhance the accuracy of the results. Particle collisions, fragmentation mechanism, and moisture evaporation are simulated by corresponding models, whereas the special treatment employed for the rotating fan region provides the capability to solve the two-phase flow simultaneously in the entire rotating and nonrotating mill domain. The flow and the operation characteristics of a recently developed lignite mill are measured, and the numerical algorithm is used to predict the mill performance under various inlet profiles of the fuel mass flow rate. The predicted results are reasonable, and in agreement with the available measurements and observations, thus offering a deeper insight into the complex dynamic and thermal behavior of the two-phase flow in the mill.

In Part I of this paper, we analyzed the turbulent flow structure and the torque transport characteristics of a fluid coupling. The results suggested certain modifications of the geometry which can improve the start-up behavior and reduce at the same time the material costs. In Part II we perform the numerical simulation of the flow in the modified geometry and investigate the influence of the modification on the performance. [S0098-2202(00)02204-5]

A quarter-scale model of an enclosed wheel racing car was tested using the elevated ground plane wind tunnel technique. To increase the aerodynamic down force, two longitudinal underbody channels were built into the vehicle’s lower surface, and a rear wing was added. The effect of these underbody channels, and of wing angle of attack and position, on the vehicle’s drag and down force was experimentally investigated. Results of the experiments indicate that the flow under the car is affected by the presence of the wheels, and the vehicle without a rear wing generates only a negligible downforce. However, the addition of a rear wing enhanced the flow under the vehicle body, resulting in an increased aerodynamic downforce.

Results are presented from an experimental study of the lift, drag, pitching moment, and flow field of a series of rounded edge simple bluff bodies of various cambers and tapers. The bodies were proportioned to be similar to those of idealized ground vehicles such as automobiles, vans, and trucks. The models were tested with and without simulated wheels, underbody roughness, and proximity to a stationary and moving ground plane. The pitch angle was varied at zero yaw angle. The force and moment coefficients and flow visualization studies indicated the existence and importance of flow regimes characterized by a pair of trailing vortices on the leeward side of the body similar to those found over an inclined body of revolution and over slender delta wings. These flows can suppress bubble-type separation. The effects of a rough underbody are generally detrimental although less so if the rough surface is on the windward side. A moving ground plane was found to give significantly different lift and drag for small ground clearances characteristic of actual road vehicles.

A new technique for measuring residual surface stresses in metals is described. This technique, which is based on the dissection method, yields detailed biaxial residual stress distributions. Metal layers are continuously removed from the specimen by electro-polishing, and the pertinent specimen shape changes are continuously monitored by differential transformers and the required circuitry. Calculations are carried out using a digital computer. The technique was used to measure residual stresses induced in 304 stainless steel by coated abrasive grinding, low-density abrasive treatment, shot peening, bonded wheel grinding, lathe finish machining, milling machine finish machining, and shaper finish machining (finish machining here is defined as light cuts).