Mean Velocity Profiles Research Articles

Characterization of flow field and combustion dynamics in a novel pressurized side-wall quenching burner using high-speed PIV/OH-PLIF measurements

A novel, pressurized side-wall quenching (SWQ) burner test rig enabling investigations on flame-wall interactions (FWI) of a fully premixed V-shaped flame at conditions mimicking some characteristics of practical devices, e.g. increased pressures and Reynolds numbers, is introduced within this study. Two operating cases featuring turbulent flow conditions at atmospheric and 3 bar operating pressure are defined and characterized based on velocity fields and flame front positions provided by simultaneous high-speed particle image velocimetry (PIV) and planar laser-induced fluorescence of the OH radical (OH-PLIF). For non-reacting conditions, profiles of mean velocities and mean velocity fluctuations are measured in addition to near-wall flow fields at locations where FWI occurs for chemically reacting conditions. For reacting conditions, near-wall flows are characterized in the vicinity of the quenching zone. Based on measured fluctuations of the streamwise velocity component, the turbulent flame is classified at the transition from the wrinkled to the corrugated flamelet regime. Using the derived flame front positions, the instantaneous flame-wall interaction is classified into SWQ-like, head-on quenching (HOQ)-like and multi-zone quenching events and the transition between these scenarios is identified by means of OH-PLIF image sequences. A statistical analysis of the flame front topology is performed based on the flame brush and deduced frequency distributions. Statistically significant differences between both operating cases are confirmed by chi-squared homogeneity tests.

Mean velocity profile in high Re-number turbulent boundary layer (Comparison with large wind tunnels in the world)

Mean velocity profile in high Re-number turbulent boundary layer (Comparison with large wind tunnels in the world)

Mean and Turbulent Characteristics of a Bottom Mixing‐Layer Forced by a Strong Surface Tide and Large Amplitude Internal Waves

AbstractWe present 15 days of both mean and turbulent field observations bottom mixing‐layer at a gently sloping 250 m deep continental shelf site, energized by tides and nonlinear internal waves (NLIWs). The tidal frequency forcing was due to the combined effects of the barotropic tide and a mode‐1 internal tide (IT), while the NLIWs were predominantly mode‐1 waves of depression. The bottom mixing‐layer thickness varied at both semidiurnal and sub‐tidal ∼O(10)d frequencies, with an average thickness of around 10 m. Compression and expansion of the mixing‐layer by both the IT and NLIWs affected the mean velocity profiles in the mixing‐layer, while the phasing between the barotropic and baroclinic flows led to an asymmetry in mean velocity profiles between periods of rising and falling isotherms. With the exception of periods of flow reversal, the turbulent kinetic energy balance and turbulent stress observations were consistent with the existence of an inertial‐sublayer with thickness of approximately 10%–15% of the mixing‐layer thickness ( ∼1 m), even beneath NLIWs. In the outer portion of the mixing‐layer—that is, above the inertial‐sublayer—NLIWs modulated the local turbulence spectra. We discuss the observations in the context of a predictive model for mixing‐layer thickness. The analysis suggests that the high‐frequency variability in mixing‐layer thickness was dominated by internal wave pumping, though strength of the ambient stratification and the frequency of the forcing were important controls on the time‐averaged (sub‐tidal) variation.

Wind tunnel study on the wake characteristics of a wind turbine model subjected to surge and sway motions

An experimental study was performed in a uniform incoming flow wind tunnel to investigate the effect of surge and sway motions on the wake characteristics of a wind turbine model. The platform surge and sway motions can be simulated at prescribed amplitudes and frequencies through a translation stage mounted on the base of the turbine model. The flow fields of near, intermediate, and far wakes of the turbine model were characterized by a particle image velocimetry system. Results show that the mean velocity profiles during the whole surging and swaying process of the downwind wakes were almost unchanged with that of a base-fixed turbine; however, the maximum mean velocity differences appeared near the blade tips for both motions compared with the base-fixed cases. Little difference was found between the mean velocity profiles of the turbine model while moving in different directions, for both the surge and sway motions. Later, the characteristics of instantaneous velocity profiles were investigated, and the lateral offset of the instantaneous velocity profiles for the swaying turbine at the two ends of the sway motion was observed. The offset distance was very close to sway amplitudes within the near wake, and it gradually decreased until it disappeared as the downstream distance increases. This work may provide an instrumental guide in the further research on the wake of floating offshore wind turbines.

Analysis of velocity profile measurements obtained by different methods in low-speed, small-scale wind tunnel

A low-speed small-scale wind tunnel was designed for spray investigation under cross and co-flow conditions. Precisely defined profiles of mean velocity and turbulent intensity in the wind tunnel test section are crucial parameters for any rigorous flow study. Different velocity measurement techniques were used to evaluate the velocity and turbulent intensity profiles in the test section. Two non-intrusive techniques, Phase-Doppler Anemometry and Laser-Doppler Anemometry (PDA, LDA), and two intrusive techniques, Constant Temperature Anemometry (CTA) and pitot static tubes of S and L-type were applied. The velocity was measured in 19 equidistantly spaced positions in a centrally placed horizontal plane. The data were obtained for four different mean velocities in the test section (7, 14, 21, 28 m/s). Results of different measurement techniques were mutually compared, and repeatabilities and uncertainties of PDA and CTA measurements were assessed. Turbulent velocity spectra measured by the CTA were analysed. The effect of declination of the pitot static tubes (L-type and S-type) was briefly discussed and compared with an industrial velocity probe QuadraTherm® 640i In-Line Mass Flow Meter with a measuring range of 5–300 m/s. Velocity and declination of pitot static tubes were analysed only in the central point of the test section. The results show that a fully turbulent and uniform flow is developed 15 mm upstream the test section area. Mean velocity and turbulent intensity profiles obtained by different techniques are in a good agreement. Uncertainties of type B of PDA and CTA measurement method are below 5%. Turbulent intensity in the main stream is under 5%. Advantages and drawbacks of the presented measurement techniques were discussed. The PDA was found to be the most suitable measurement technique due to its precision and non–intrusive flow probing.

Characteristics and calibration of the mexican boundary layer wind tunnel at UNAM

With the aim to improve and promote Mexican Wind Engineering research, a low-speed closed return wind tunnel for atmospheric environment and structural wind-loading simulations was built at the National Autonomous University of Mexico (UNAM). The testing calibration procedure was developed based on many recommendations specified by several authors on the literature to assure compliance with full-scale measurements, laboratory results and international coding. The calibration procedure consists of four stages: the first stage is to represent adequately the atmospheric boundary layer; the second, to obtain adequate pressure coefficients for rigid models; the third, to perform tests to obtain the aerodynamic forces and some dynamic properties from structural models; and the fourth is to develop aeroelastic models. This paper focuses on the first two stages. Therefore, during the first stage, various tasks were developed to perform adequate representation on the lower-portion of the atmospheric boundary layer to characterize mean velocity profiles and turbulence fluctuations. On the second stage, the main task was to replicate external mean pressure coefficients of a typical cubic low-rise building as many other laboratories have done before. During the first stage it was possible to adequately replicate an urban atmospheric boundary layer artificially. During the second stage, some results reveal the need to update the current Mexican regulations for wind design, since some pressure coefficients considerably exceeds the threshold values. Finally, although other types of tests are in progress, it is considered that the new boundary layer wind tunnel of the UNAM can be used with confidence to test different type of structures and contribute to the development of Mexican Wind Engineering.

Development of eddy viscosity measurement system utilizing velocity profiler

We propose a novel turbulent eddy viscosity profiler to evaluate the influence of interactions between turbulent eddies and dispersed materials as an effective eddy viscosity in Taylor-Couette geometry for frictional drag reduction studies. This method was conceived from the ultrasonic spinning rheometry which evaluates rheological properties by substituting experimentally obtained velocity profiles into the equation of motion. The eddy viscosity is calculated using a model derived from Reynolds-averaged Navier-Stokes equation. By modeling the Reynolds shear stress using the concept of the eddy viscosity, only the spatial distribution of the eddy viscosity remains to be estimated from the mean velocity distribution. We can extract the contributions of eddies with different time and spatial scales depending on the definition of the averaging operation, since mean velocity profiles include the information of momentum transfer by eddies which have the specific time and spatial scales. In this paper we derive the analytical model equation where velocity profile is averaged in temporal and axial directions and the molecular viscosity term balances with the eddy viscosity term. In this case, we can separate the original flow field into Couette-like mean velocity and fluctuation components corresponding to Taylor vortices and smaller fluctuations. Additionally, we show the experimental apparatus and the result for a glycerin aqueous solution using the equation with the above averaging operation. The distribution of eddy viscosity is obtained as a function of radial position.

Kinetic-energy-flux-constrained model using an artificial neural network for large-eddy simulation of compressible wall-bounded turbulence

Kinetic energy flux (KEF) is an important physical quantity that characterizes cascades of kinetic energy in turbulent flows. In large-eddy simulation (LES), it is crucial for the subgrid-scale (SGS) model to accurately predict the KEF in turbulence. In this paper, we propose a new eddy-viscosity SGS model constrained by the properly modelled KEF for LES of compressible wall-bounded turbulence. The new methodology has the advantages of both accurate prediction of the KEF and strong numerical stability in LES. We can obtain an approximate KEF by the tensor-diffusivity model, which has a high correlation with the real value. Then, using the artificial neural network method, the local ratios between the real KEF and the approximate KEF are accurately modelled. Consequently, the SGS model can be improved by the product of that ratio and the approximate KEF. In LES of compressible turbulent channel flow, the new model can accurately predict mean velocity profile, turbulence intensities, Reynolds stress, temperature–velocity correlation, etc. Additionally, for the case of a compressible flat-plate boundary layer, the new model can accurately predict some key quantities, including the onset of transitions and transition peaks, the skin-friction coefficient, the mean velocity in the turbulence region, etc., and it can also predict the energy backscatters in turbulence. Furthermore, the proposed model also shows more advantages for coarser grids.

Shape and scaling of the mean-velocity profile in thermally-stratified plane-Couette flows

It has long been known from measurements that buoyant motions cause the mean-velocity profile (MVP) in thermally-stratified, wall-bounded turbulent flows to significantly deviate from its constant-density counterpart. Theoretical analysis has restricted attention to an ‘intermediate layer’ of the MVP, akin to the celebrated ‘log layer’ in the constant-density case. Here, for thermally-stratified plane-Couette flows, we study the shape and scaling of the whole MVP. We elucidate the mechanisms that dictate the shape of the MVP by using the framework of the spectral link (Gioia et al 2010 Phys. Rev. Lett. 105 184501), and obtain scaling laws for the whole MVP by generalizing the Monin-Obukhov similarity theory.

Experimental and numerical investigation of the transition progress of strut-induced wakes in the supersonic flows

Strut serves as an effective and robust flameholder in a scramjet combustor, and the resultant wakes have a great impact on the fuel mixing and flame stabilization. Present work focuses on the non-reactive flow induced by strut without fuel injection, removing the effect of chemical reactions on turbulence. To investigate the transition process of turbulent wakes, both high-resolution experiments and numerical simulations are conducted. An advanced optical measurement technique is adopted to visualize the flow structures in different Mach conditions, and to disclose the compressible effect on the shear layer. Experimental results indicate that the scale of turbulent vortices decreases and the transition becomes difficult with the decline of Reynolds number in the cases with the same total temperature and pressure. Evidently, the viscous effect gets weakened for the supersonic flow with a high Reynolds number, giving rise to large scale vortex streets. On this basis, the intrinsic mechanism that governs the instability of shear layer is investigated by large eddy simulation. The strut-induced wakes can be divided into three parts, namely the recirculation zone, the transition zone and the downstream turbulent zone. A type of Kelvin-Helmholtz instability produced by the interactions of the reattachment shock and shear stress, should be responsible for the generation of the initial streamwise vortices during the transition process of shear layer. Thus, the flow instability rapidly grows as a form of nonlinear, magnifies, and changes the mean velocity profile of the shear layer, leading to its transition from laminar state to turbulence. Finally, the influence of turbulence on the temporal and spatial evolution of the vortices in the wakes is analyzed in deep. The upstream turbulent fluctuations facilitate the occurrence of transition process, and promote to generate larger scale spanwise vortex streets. Present work can help us understand the flow dynamics of turbulent wakes in a strut-stabilized scramjet combustor.

High-order gas-kinetic scheme for large eddy simulation of turbulent channel flows

In this study, the high-order gas kinetic scheme (GKS) is employed for explicit large eddy simulation (hereafter referred to simply as “LES”) and implicit large eddy simulation (iLES) of turbulent channel flows. The main objective is to compare the performance of iLES and LES in the high-order finite volume framework, and study which is most suitable for turbulence simulation. The prediction abilities of different explicit LES models and iLES method on various statistics and flow structures are compared. Most results from both iLES and explicit LES are very close to those of direct numerical simulation. Moreover, iLES is generally superior to explicit LES in predicting several important flow properties, including the mean velocity profiles, Reynolds stress, and Q-criterion iso-surfaces. This superior performance of iLES may arise that the numerical dissipation of the high-order scheme is enough to replace the subgrid dissipation needed in large eddy simulation of turbulence. If the explicit LES model is further adopted, the dissipation will increase, so the results degrade. The overall satisfactory results show that the high-order GKS can provide appropriate numerical dissipation and is suitable for iLES of turbulence.

Turbulent flow in curved channels

Fully developed turbulent flow in channels with mild to strong longitudinal curvature is studied by direct numerical simulations. The Reynolds based on the bulk mean velocity and channel half-width $\delta$ is fixed at $20\,000$ , resulting in a friction Reynolds number of approximately 1000. Four cases are considered with curvature varying from $\gamma = 2\delta /r_c = 0.033$ to 0.333, where $r_c$ is the curvature radius at the channel centre. Substantial differences between the mean wall shear stress on the convex and concave walls are already observed for $\gamma = 0.033$ . A log-law region is absent and a region with nearly constant mean angular momentum develops in the channel centre for strong curvatures. Spanwise and wall-normal velocity fluctuations are strongly amplified by curvature in the outer region of the concave channel side. Only near the walls, where curvature effects are relatively weak, do the mean velocity and velocity fluctuation profiles approximately collapse when scaled by wall units based on the local friction velocity. Budgets of the streamwise and wall-normal Reynolds-stress equations are presented and turbulence structures are investigated through visualizations and spectra. In the case with strongest curvature, the flow relaminarizes locally near the convex wall. On the concave channel side, large elongated streamwise vortices reminiscent of Taylor–Görtler vortices develop for all curvatures considered. The maximum in the premultiplied two-dimensional wall-normal energy spectrum and co-spectrum shifts towards larger scales with increasing curvature. The large scales substantially contribute to the wall-normal velocity fluctuations and momentum transport on the concave channel side.

Theoretical and experimental investigations on swirling steam-water mixture flow in a circular channel with modified surface walls

The influence of surface roughness as well as protrusion geometry laid over the inner wall of the horizontal channel, on mean velocity and turbulent quantities along with thermal quantities of the swirling steam-water flow are determined experimentally. These were compared with the measurements for those obtained for smooth inner surface of the channel. The test facility has comprised of a Perspex pipe having inner diameter of 15 cm and length 30 cm. It contains three sections; one has smooth inner surface, second has rough inner surface with mild sand blasting and the third has square circular protruded collars along with mild treatment with the sand blasting. Mean velocity profile within the region close to the vicinity of the surface roughness has been lower than the values of the mean velocity profile in case of smooth inner surface of the pipe. And mean velocity values with protruded collar along with roughened surface are even lower than those in case of inner rough surface. However, the mean velocity values at distance away from the rough surface match among the three cases. Similar profiles representative of the three surfaces are obtained in case of velocity deficit. Whereas different turbulent characteristics are observed among smooth, rough, and protruded surfaces. Significant influences on the normal and Reynolds stresses occur over the whole of the layer due to the rough and protruded surfaces than those of the stresses generated in case of smooth surface. Although velocity spectra exhibit differences between the three surfaces, the mean energy dissipation rate does not appear to be significantly affected by the roughness and protruded surface. Nusselt number with passage of time following initiation of steam into the pipe, drops to an equilibrium value after passage of about 50–70 s. And the heat transfer characterized by normalized Stanton number ratio of rough surface to smooth surface, increases with increase in size of the sand grain for all the three surfaces. The increase in Stanton number ratio representing the rough surfaces is higher than the values of ratio in case of smooth surface. However, the major outcome of this study has been owed to the vorticities shed through the roughness, which is comparable to the roughness scale, k and this was found substantial than the turbulence scale of the outer layer.

Performance of Wall-Modeled LES with Boundary-Layer-Conforming Grids for External Aerodynamics

We investigate the error scaling and computational cost of wall-modeled large-eddy simulation (WMLES) for external aerodynamic applications. The NASA Juncture Flow is used as representative of an aircraft with trailing-edge smooth-body separation. Two gridding strategies are examined: 1) constant-size grid, in which the near-wall grid size has a constant value and 2) boundary-layer-conforming grid (BL-conforming grid), in which the grid size varies to accommodate the growth of the boundary-layer thickness. Our results are accompanied by a theoretical analysis of the cost and expected error scaling for the mean pressure coefficient and mean velocity profiles. The prediction of is within less than 5% error for all the grids studied, even when the boundary layers are marginally resolved. The high accuracy in the prediction of is attributed to the outer-layer nature of the mean pressure in attached flows. The errors in the predicted mean velocity profiles exhibit a large variability depending on the location considered, namely, fuselage, wing-body juncture, or separated trailing edge. WMLES performs as expected in regions where the flow resembles a zero-pressure-gradient turbulent boundary layer such as the fuselage ( error). However, there is a decline in accuracy of WMLES predictions of mean velocities in the vicinity of wing-body junctions and, more acutely, in separated zones. The impact of the propagation of errors from the underresolved wing leading edge is also investigated. It is shown that BL-conforming grids enable a higher accuracy in wing-body junctions and separated regions due to the more effective distribution of grid points, which in turn diminishes the streamwise propagation of errors.

Pressure Gradient Effects on the Performance of Riblets Installed on Aircraft Surfaces

A method for estimating the drag reduction performance of riblets installed on the surfaces of an aircraft was extended to take the effect of the pressure gradient over the aircraft into account. This method simply and roughly estimates the effectiveness of riblets applied to arbitrary surfaces of any aircraft by fusing wind tunnel test data and computational fluid dynamics analysis. The drag reduction rate is calculated from the relationships between friction drag reduction , wall-normalized riblet spacing , and Clauser pressure gradient parameter . To obtain this relationship, a wind tunnel test with straight riblets in an adverse pressure gradient was carried out. The resulting shift in the value in the intercept of the log-law region of the mean velocity profile for riblet cases indicates that the drag reduction effect decreases as the Clauser parameter increases. Based on these results, an approximate surface for the relationship between , , and was proposed, and the drag reduction performance of riblets installed on the surfaces of a conceptual aircraft was estimated. The total drag reduction rates estimated by the extended method considering pressure gradient effects and the original method case were both about 2%, which indicates that the effects of the pressure gradient on the aircraft on overall riblet performance are small.

Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets.

The effect of nozzle geometry on the dynamics and mixing of turbulent jets is experimentally investigated. The jets with a Reynolds number of 13,000 were issued from four different pipes with circular, elliptical, square and triangular cross sections. The velocity field was measured in the self-similar region of the jets using an acoustic Doppler velocimeter. Statistical parameters, such as the mean velocities, velocity variances, spreading rates, mass flow rates, and entrainment rates are presented. The results show that despite having approximately similar decay rates for the mean centerline velocities, the radial profiles of the axial mean velocity varied in jets with different nozzle cross sections and were widest for elliptical jets and narrowest for the triangular ones. On the other hand, velocity variances were greatest for the triangular jet when compared to the jets released from cross sections of other geometries. Furthermore, the spreading rate, mass flow rate, and entrainment rate were highest for the elliptical jet, and lowest for the triangular jet. From this it can be inferred that the elliptical jet has the highest mixing and dilution. The results of this study could help to improve the initial mixing of pollutants by optimizing the initial conditions.

Influence of Particle Mass Fraction over the Turbulent Behaviour of an Incompressible Particle-Laden Flow

The presence of spherical solid particles immersed in an incompressible turbulent flow was numerically investigated from the perspective of the particle mass fraction (PMF or ϕm), a measure of the particle-to-fluid mass ratio. Although a number of different changes have been reported to be obtained by the presence of solid particles in incompressible turbulent flows, the present study reports the findings of varying ϕm in the the turbulent behaviour of the flow, including aspects such as: turbulent statistics, skin-friction coefficient, and the general dynamics of a particle-laden flow. For this purpose, a particle-laden turbulent channel flow transporting solid particles at three different friction Reynolds numbers, namely Reτ=180, 365, and 950, with a fixed particle volume fraction of ϕv=10−3, was employed as conceptual flow model and simulated using large eddy simulations. The value adopted for ϕv allowed the use of a two-way coupling approach between the particles and the flow or carrier phase. Three different values of ϕm were explored in this work ϕm≈1,2.96, and 12.4. Assessment of the effect of ϕm was performed by examining changes of mean velocity profiles, velocity fluctuation profiles, and a number of other relevant turbulence statistics. Our results show that attenuation of turbulence activity of the carrier phase is attained, and that such attenuation increases with ϕm at fixed Reynolds numbers and ϕv. For the smallest Reynolds number case considered, flows carrying particles with higher ϕm exhibited lower energy requirements to sustain constant fluid mass flow rate conditions. By examining the flow velocity field, as well as instantaneous velocity components contours, it is shown that the attenuation acts even on the largest scales of the flow dynamics, and not only at the smaller levels. These findings reinforce the concept of a selective stabilising effect induced by the solid particles, particularly enhanced by high values of ϕm, which could eventually be exploited for improvement of energetic efficiency of piping or equivalent particles transport systems.

The structure of a highly decelerated axisymmetric turbulent boundary layer

Experiments were performed over a body of revolution at a length-based Reynolds number of 1.9 million. While the lateral curvature parameters are moderate ( $\delta /r_s < 2, r_s^+>500$ , where $\delta$ is the boundary layer thickness and r s is the radius of curvature), the pressure gradient is increasingly adverse ( $\beta _{C} \in [5 \text {--} 18]$ where $\beta_{C}$ is Clauser’s pressure gradient parameter), representative of vehicle-relevant conditions. The mean flow in the outer regions of this fully attached boundary layer displays some properties of a free-shear layer, with the mean-velocity and turbulence intensity profiles attaining self-similarity with the ‘embedded shear layer’ scaling (Schatzman & Thomas, J. Fluid Mech., vol. 815, 2017, pp. 592–642). Spectral analysis of the streamwise turbulence revealed that, as the mean flow decelerates, the large-scale motions energize across the boundary layer, growing proportionally with the boundary layer thickness. When scaled with the shear layer parameters, the distribution of the energy in the low-frequency region is approximately self-similar, emphasizing the role of the embedded shear layer in the large-scale motions. The correlation structure of the boundary layer is discussed at length to supply information towards the development of turbulence and aeroacoustic models. One major finding is that the estimation of integral turbulence length scales from single-point measurements, via Taylor's hypothesis, requires significant corrections to the convection velocity in the inner 50 % of the boundary layer. The apparent convection velocity (estimated from the ratio of integral length scale to the time scale), is approximately 40 % greater than the local mean velocity, suggesting the turbulence is convected much faster than previously thought. Closer to the wall even higher corrections are required.

Large-Eddy Simulation of a Hydrocyclone with an Air Core Using Two-Fluid and Volume-of-Fluid Models

Large-eddy simulations have been conducted for two-phase flow (water and air) in a hydrocyclone using Two-Fluid (Euler–Euler) and Volume-of-Fluid (VOF) models. Subgrid stresses are modeled using a dynamic eddy–viscosity model, and results are compared to those using the Smagorinsky model. The effects of grid resolutions on the mean flow and turbulence statistics have been thoroughly investigated. Five block-structured grids of 0.72, 1.47, 2.4, 3.81, and 7.38 million elements have been used for the simulations of Hsieh’s 75 mm hydrocyclone Mean velocity profiles and normal Reynolds stresses have been compared with experimental data. Results of the two-fluid model are in good agreement with those of the VOF model. A fine mesh in the axial and radial directions is necessary for capturing the turbulent vortical structure. Turbulence structures in the hydrocyclone are dominated by helical vortices around the air core. Energy spectra are analyzed at different points in the hydrocyclone, and regions of low turbulent kinetic energy are identified and attributed to stabilizing effects of the swirling velocity component.

Wake Flow Measurements Behind Rotating Smooth Spheres and Baseballs Near Critical Reynolds Numbers

Abstract The flow field behind spinning baseballs at two different seam orientations was investigated, and compared with a smooth sphere, to isolate effects of seams on the Magnus effect at Reynolds numbers of 5×104 and 1×105. The rotational speed of the three spheres varied from 0 to 2400 rpm, which are typical of spin rates imparted to a thrown baseball. These spin rates are represented nondimensionally as a relative spin rate relating the surface tangential velocity to the freestream velocity, and varied between 0 and 0.94. Mean velocity profiles, streamline patterns, and power spectral density of the velocity signals were taken using hot-wire anemometry and/or stereoscopic particle image velocimetry in the wake region. The sphere wake orientation changed over a range of relative spin rates, indicating an inverse Magnus effect. Vortex shedding at a Strouhal number of 0.25 was present on the sphere at low relative spin rates. However, the seams on the baseball prevented any consequential change in wake orientation and, at most spin rates, suppressed the shedding frequency exhibited by the sphere. Instead, frequencies corresponding to the seam rotation rates were observed in the wake flow. It was concluded that the so-called inverse Magnus effect recorded by previous investigators at specific combinations of Reynolds number and relative spin rate on a sphere exists for a smooth sphere or an axisymmetrically dimpled sphere but not for a baseball near critical Reynolds numbers, where the wake flow pattern is strongly influenced by the raised seams.