Boundary Layer Separation Point Research Articles

The combined influence of spin and roughness frequency on sphere aerodynamics

AbstractThe lift and drag of spinning spheres roughened with macro-roughness elements are examined. The velocity field of these same spheres in flight is measured with particle image velocimetry (PIV). Several spheres with varying roughness are examined at various spin rates and fixed Reynolds number. Unlike previous studies, where the roughness height is varied, in the present work, the number of roughness elements is varied. The PIV datasets are used to determine the boundary layer separation points for each case. Comparing the lift and drag to the separation points reveals that (1) the separation points become more asymmetric with spin (the Magnus effect), (2) The drag increases with the size of the wake, and (3) the drag increases with the asymmetry of the separation points, meaning that lift on spheres is accompanied by increased drag. Scant evidence of this third effect has been reported previously. Additionally, it is shown that, counter to smooth spheres, the force transmitted to the surface through the roughness elements leads to significant drag. The drag is shown to increase with the number of roughness elements while the lift decreases. Results have implications for understanding aerodynamic forces on bluff bodies with roughness and passive control of aerodynamic forces through roughness element frequency rather than the traditional roughness height.

On the problem of determining the separation point of the laminar boundary layer by the example of the Howart–Tani flow

A new approach is proposed how to calculate the laminar boundary layer in slow flows. It is based on describing the velocity profile using a polynomial of indefinite degree and on introducing two additional coordinate-dependent parameters, one of which defines the separation of the boundary layer from a wall once this parameter reaches zero. The approach based on three integral relations and reducing the problem to the system of three ordinary differential equations was further developed. A numerical analysis performed for the Howart–Tani flow showed that the separation point of a laminar boundary layer is determined highly exactly using this approach. It was shown that introducing into consideration certain restrictions for the outer surface of a boundary layer allows one to find the problem solutions which would adequately define and fairly exactly determine the flow velocity distribution within this layer, and at any point up to the point of its separation. The proposed numerical-analytical calculation method based on three integral relations and two additional parameters and involving the definition of the flow velocity profile by a polynomial of indefinite degree can be extended to other slow flows past smooth two-dimensional surfaces.

Effect of Vortex Generations on Aerodynamic Performance of Rough Wind Turbine Airfoil

Experimental investigations were carried out in wind tunnel facilities to assess the effect of vortex generators on the aerodynamic characteristics of a NACA4418 airfoil, particularly in scenarios where surface roughness is precipitated by environmental elements like dust, sand, and insects. These elements are known to adversely affect the efficiency of power generation. These studies meticulously analyzed the airfoil’s pressure distribution and its aerodynamic coefficients, taking into account the roughness positioned at varying locations along the chord. Special attention was given to the roughness located at 0.2c due to its pronounced impact on aerodynamic efficiency. The research highlighted that vortex generators play a crucial role in mitigating boundary layer separation, thereby enhancing the lift-to-drag ratio, especially at higher angles of attack. Notably, the deployment of vortex generators on airfoils affected by surface roughness resulted in a more pronounced improvement, elevating the maximum lift coefficient by 11.6% compared to their effect on smooth airfoils. Furthermore, the study revealed that an increase in the Reynolds number significantly augments the benefits provided by vortex generators, improving the lift coefficient and delaying the stall angle for airfoils with surface roughness, while also shifting the boundary layer separation point towards the airfoil’s trailing edge.

An Investigation on the Steady and Unsteady Wake Flow Regimes and Aerodynamic Characteristics of the Trapezoidal Cylinders Using Immersed Boundary-Lattice Boltzmann Method

Abstract In this study, the flow physics of the forward-facing (FF) and backward-facing (BF) trapezoidal cylinders (TC) subjected to two-dimensional, incompressible, and laminar flow is investigated using an in-house developed flexible forcing immersed boundary-lattice Boltzmann solver. The Reynolds number (Re) is defined based on the cylinder's characteristic length D. For the steady and unsteady flow regimes, Re is varied in the ranges of 10–40 and 75–125, respectively. The TCs shape is varied by modifying its nondimensional axial H/D and transverse Y/D length scales, between 0.5 to 2 and 0 to 1, respectively. Here, TCs horizontal central axis is always aligned along the incoming flow direction. It is observed that the flow separation points on the FF-TC and BF-TC are strongly influenced by the geometric (H/D and Y/D) and flow parameters (Re). Based on the boundary layer separation point, we have categorized the wake flow regimes behind the FF-TC and BF-TC into four types. In addition, the effect of the geometric and flow parameters on the drag coefficient (Cd), vortex shedding frequency, and steady and unsteady wake characteristics are thoroughly investigated here. Furthermore, by performing nonlinear regression analysis, we have proposed a set of correlation equations for the Cd and Strouhal number (St), using which the aerodynamic characteristics of differently shaped TC can be derived in the considered Re range without performing rigorous numerical simulations or experiments.

Wake flow structure and hydrodynamic characteristics of flow around a C-shaped cylinder with variable attack angle at low Reynolds numbers

A numerical investigation is conducted on the flow over a C-shaped cylinder in the low Reynolds number range of Re = 40–160. The effect of attack angle (α) ranging from 0° to 180° is examined simultaneously. Wake evolution and vortex structure as well as the hydrodynamic characteristics are analyzed. Seven flow patterns are identified based on the location of boundary layer separation points and the evolution of near-wall vortices. The boundary layer separation points lock on the two ends of the C-shaped cylinder, resulting in the typical Karman vortex street (Pattern I). A separation point shifts to the curved surface in Pattern II-1 and Pattern II-2, and a quasi-stagnation vortex (QS) is formed within the groove in Pattern II-2. In Pattern III-1 and Pattern III-2, the QS fills the groove. The subordinate vortex is observed in the groove close to the lower end (Pattern IV). The complicated vortex merging occurs around the lower end in Pattern V. The separation points lock on the two ends, exhibiting a pair of counter-rotating vortex shedding downstream of the two ends (Pattern VI). No vortex shedding is found in Pattern VII. Additionally, the characteristic parameters and the hydrodynamic coefficients are related, and they are associated with the flow pattern partition. Four types of vortex street are identified in the wake of the C-shaped cylinder, including no vortex street, 2S vortex mode and decayed vortex street, 2S vortex mode and secondary vortex street (2S-SVS), and P + S vortex mode and secondary vortex street in vortex evolution (P + S-SVS).

Mapping of the flow structure and hydrodynamic properties of a round-ended cylinder

This paper reports the numerical results of flow past a round-ended cylinder with various incidence angles in a low Reynolds number range of Re = 60–160. Mapping of the flow structure and hydrodynamic properties is examined in the incidence angle range of α = 0°–90° with increment of 15°. Three wake patterns are identified, including the steady and symmetric wake without vortex shedding (Pattern I), the Karman vortex street (Pattern II), and the Karman vortex street with the occurrence of subordinate vortex (Pattern III). The reattachment of boundary layers results in the occurrence of a subordinate vortex and hence the non-single-frequency fluctuation of hydrodynamic coefficients (CL and CD, which are lift and drag coefficients, respectively). Elliptical and figure-eight CL–CD curves are observed, depending on the frequency ratios of the two coefficients and their weights. Non-zero time-averaged CL occurs when 0° < α < 90°, due to the asymmetric boundary layer separation. The backward migration of boundary layer separation point contributes to the reduction of frictional drag and the vortex formation length. The shortening of the vortex formation length results in the enhanced fluctuations of CL and CD.

Vortex-Induced vibration suppression for a cylinder with random grooves inspired by rough tree bark

The vortex-induced vibration (VIV) response of a 2-degree-of-freedom cylinder with random grooves is investigated numerically based on the Reynolds Average Navier–Stokes (RANS) method. The Newmark-β method is used to solve the equations of motion of the cylinder. The effects of the random groove on VIV suppression are discussed in detail. The coverage ratios (k) of the random groove include 0%, 25%, 50%, 75%, and 100%. The vibration suppression effect of k = 75% and k = 100% is not significant. However, the VIV amplitude of the cylinders with k = 25% is greatly suppressed. In particular, the cross-flow amplitude ratio is reduced from 1.50 (k = 0%, a smooth cylinder) to 0.65 (k = 25%). First, the boundary-layer separation point of the grooves is fixed, so the random grooves destroy the normal separation and development of the main vortices. Therefore, two rows of vortices with different sizes are generated on both sides of the cylinder, which may cause unstable vibration. Meanwhile, a series of small vortices are formed in the grooves. These small vortices cannot merge synchronously into the main vortices and further reduced the strength of the main vortices. Consequently, the driving force of the vibration, which is generated by the main vortices, is reduced. As a result, the VIV responses are suppressed.

Numerical investigation on flow-induced vibration response of the cylinder inspired by the honeycomb

The honeycomb-shaped structure has been proved to have good mechanical properties, and is it possible combining its good mechanical properties together with its flow characteristics? This will determine whether the honeycomb-shaped cylinder can be further extended to the practical application in ocean engineering or wind engineering. Therefore, the flow-induced vibration (FIV) responses of the three-dimensional cylinders inspired by the honeycomb are numerically investigated. Three different structures are considered, including the smooth cylinder (P0), the P60 cylinder corresponds to the direct impingement of the freestream on the saddle point, and the P30 cylinder corresponds to the vertical impingement of the freestream on the one edge of the structural element. The Reynolds number ranges of the simulations are 0.8 × 104 ≤ Re ≤ 8.0 × 104. Compared with the maximum cross-flow amplitude of P0, it is reduced by 59.33% for P60. The maximum mean-drag coefficients of P60 and P30 are about 1.85 and 2.10, which are reduced by about 38.33% and 30% compared with that of P0. The slope (β) of the actual lift coefficient (CT(t)) and the actual angle of attack (α(t)) is defined. For P60, β is greater than 0, so galloping doesn't occur. However, as for sample P30, β is less than 0 and thus galloping happens in the high reduced velocity range. Especially, the maximum in-line amplitude ratio reaches 0.6 when Ur = 20 for P30. Due to the existence of two boundary-layer separation points and the concave structure, the flow of P60 is weakened, so that the FIV response of P60 is suppressed. The flow separation and the flow reattachment are the fundamental causes of galloping response for P30. The critical angle of attack (θ) at which galloping response occurs is 40° for the honeycomb-shaped cylinder. When θ ≥ 40, β ≥ 0, the large-amplitude motion will not occur in the high reduced velocity range. When θ < 40, β < 0, and the negative damping phenomenon is observed and the galloping occurs.

The Bump Suppression Strategy for the Transonic Buffet of the Supercritical Airfoil

Transonic buffet brings challenges to civil aircraft design, including but not limited to the structural fatigue and the handling quality degradation. Therefore, it is necessary to analyze the transonic buffet of the supercritical airfoil and propose the buffet suppression strategy. This paper first employs the delayed detached-eddy simulation method to simulate the unsteady buffet process of the OAT15A supercritical airfoil. Then, the temporal–spatial characteristics of the flowfield and the separation region dynamics are analyzed based on the time-domain analysis method and the dynamic mode decomposition method. After that, different two-dimensional bumps are arranged in the shock motion region to suppress the shock oscillation, and the suppression mechanism and suppression strategy are studied. The results show that the process of the developed transonic buffet is significantly influenced by the merging of the front and the rear separation regions. In case the bump obstructs this confluence phenomenon, the developed transonic buffet can be suppressed. Furthermore, it is also found that a two-dimensional bump with superior buffet performance should have the following features: The bump should be placed after the shock-induced boundary-layer separation point to make the shock-induced boundary-layer separation bubble generate on the bump ramp. Also, the height of the bump should be carefully designed to prevent the front and rear separation regions from merging and to make the front separation region disappear quickly. Finally, this strategy is successfully applied to another supercritical airfoil to confirm the universality of the controlling strategy proposed.

Aerodynamic performance enhancement of the DU99W405 airfoil for horizontal axis wind turbines using slotted airfoil configuration

Unsteady aerodynamics is a significant problem in designing thicker airfoils for HAWT applications. The inboard airfoils of the wind turbine blades are kept thicker to maintain structural integrity, but it comes with some cons, such as loss of aerodynamic efficiency. The current study is focused on solving this problem for thick airfoils by introducing a lift control device – slot. A novel slot design is introduced to the DU-99-W-405 airfoil geometry to study the effect of the slot on lift and drag coefficients (Cl and Cd) of the airfoil over a wide range of angles of attack. The boundary layer separation point on the upper surface is observed by performing a numerical simulation of the clean airfoil. Five different positions of the slot along the chord (slots 1, 2, 3, 4, and 5) are considered for numerical simulation. Slots 1 and 5 are near the leading and trailing edges of the airfoil. The other slots are kept between them. Cl and Cd values are calculated for all the slotted configurations, and the results were plotted with respect to the angle of attack. The optimum Cl, Cd, and Cl/Cd values are obtained for the slot 2 configuration, with corresponding improvement of 68.8%, 36.9%, and 116%.

Hydrodynamic characteristics and wake structure of flow over a round-ended cylinder at a low Reynolds number

Hydrodynamic characteristics and wake structures of the flow over a round-ended cylinder are invaluable for the design of associated cylindrical structures such as bridge piers and submerged floating tunnels. This paper reports the results of a numerical investigation into the flow past a round-ended cylinder and the associated hydrodynamic forces as well as the evolution of vortex structure and boundary layer separation. The effect of incidence angle α, ranging from 0° to 90°, is examined at a low Reynolds number of 100 based on the projected length. Both the drag and lift forces are sensitive to the incidence angle. When 0° &amp;lt; α &amp;lt; 90°, boundary layers asymmetrically separate from two sides of the cylinder, giving rise to a time-mean pressure difference that is not perpendicular to the incoming flow direction. There are two directly related results, one is the non-zero time-mean lift coefficient, and the other is the occurrence of a secondary frequency of drag coefficient, the same as that of lift coefficient. The most forward separation point of the upper boundary layer and the maximum size difference of vortices generated from two sides contribute to the maximum time-mean lift coefficient occurring at α = 45°. The vortex formation length is shortened with increasing α, resulting in the augment of the fluctuation amplitudes of fluid forces. The enlargement of drag force is mainly attributed to the broadened wake width with the increase in α.

Aerodynamic Efficiency Improvement on a NACA-8412 Airfoil via Active Flow Control Implementation

The present paper introduces a parametric optimization of several Active Flow Control (AFC) parameters applied to a NACA-8412 airfoil at a single post-stall Angle of Attack (AoA) of 15∘ and Reynolds number Re = 68.5×103. The aim is to enhance the airfoil efficiency and to maximize its lift. The boundary layer separation point was modified using Synthetic Jet Actuators (SJA), and the airfoil optimization was carried on by systematically changing the pulsating frequency, momentum coefficient and jet inclination angle. Each case has been evaluated using Computational Fluid Dynamic (CFD) simulations, being the Reynolds Averaged Navier–Stokes equations (RANS) turbulence model employed the Spalart Allmaras (SA) one. The results clarify which are the optimum AFC parameters to maximize the airfoil efficiency. It also clarifies which improvement in efficiency is to be expected under the operating working conditions. An energy balance is presented at the end of the paper, showing that for the optimum conditions studied the energy saved is higher than the one needed for the actuation. The paper clarifies how a parametric analysis has to be performed and which AFC parameters can be initially set as constant providing sufficient previous knowledge of the flow field is already known. A maximum efficiency increase versus the baseline case of around 275% is obtained from the present simulations.

Influence of upstream cylinder on flow-induced vibration and heat transfer of downstream cylinder

The effect of upstream stationary cylinder on the flow-induced vibration (FIV) and heat transfer characteristics of downstream elastically supported cylinder was investigated numerically. The influence of reduced velocity (U*) and gap between two cylinders (S/D) on the vortex formation, temperature distribution, FIV response, and Nusselt number was studied. The results show that the FIV of cylinder has positive and negative effects on heat transfer. When U* is low, the heat transfer of the downstream oscillatory cylinder is weakened. As U* increases, the FIV will gradually enhance the heat transfer. When S/D = 1.1–3.0, the FIV of the downstream oscillator can drastically enhance the heat exchange of the upstream one, and the average Nusselt number (NuA) of the upstream cylinder can increase by 19.51%. When S/D rises to 4 or 5, the change of the boundary layer separation point of two cylinders is similar and the heat transfer characteristics of the upstream cylinder are about the same as the cases when both cylinders are stationary. For the downstream cylinder, the heat transfer will be significantly strengthened, and NuA can increase by up to 150.42%.

Numerical simulation on hydrodynamic and flow noise of different shape sonars

Objectives In order to reduce the flow noise on the outer surface of the traditional circular sonar, three different sonar shapes (circular, elliptical and square) are designed, and the hydrodynamic and flow noise on their outer surfaces are studied. Methods Based on the standard \begin{document}$k - \varepsilon $\end{document} turbulence calculation model in Fluent and Lighthill's acoustic analogy method, this paper analyzes the flow field and sound field of the outer surfaces of three different sonar shapes. Results Comparing the hydrodynamic results of the three sonar shapes, it is found that the square has the largest lift coefficient amplitude and average drag coefficient, and the ellipse has the smallest. The hydrodynamic difference is caused by the differences in the boundary layer separation points and wake vortex. Comparing the flow noise results, it is found that the total sound pressure level of the circle is the largest and that of the ellipse is the smallest. The circle and square show the characteristics of a positive figure eight dipole sound source, and the maximum sound radiation is perpendicular to the incoming flow direction, while the ellipse shows the characteristics of an inverted figure eight dipole sound source, and the maximum sound radiation is horizontal to the incoming flow direction. Conclusions This study can provide references for the shape design of sonar, such as replacing the traditional circular sonar with the elliptical sonar.

Wake structure and evolution of flow over a finned circular cylinder

This paper reports the results of a numerical investigation into the flow over a circular cylinder evenly attached with rectangular ribs around its circumference and the associated near-wall vortex structure as well as the evolution of wake flow. The effect of the number of ribs (n) ranging from 1 to 12 is examined in a low Reynolds number range of 60–180. Five kinds of near-wall vortices are identified with the presence of rectangular ribs, including quasi-stagnation vortices, subordinate vortices, inter-rib vortices, inter-rib quasi-stagnation vortices, and dynamic inter-rib vortices. These near-wall vortices and their evolution are sensitive to Re as well as n. With the introduction of ribs, each boundary layer experiences multiple separations that increase from 2 to 4 as n increases from 1 to 12. The intermittent emergency of the last separation is attributed to the switching of the final separation between two adjacent ribs. Furthermore, the duration of the last separation depends on Re and the evolution of dynamic inter-rib vortices. The hydrodynamic coefficients and vortex shedding frequency are closely related to the vortex formation length (Lf*) and wake width (W*). The different variation of Lf* and W* with Re is possibly associated with the appearance and number of subordinate vortices. In addition, the fluctuation of W* is mainly attributed to the switching of boundary layer separation point. The wake flow experience two evolutions as the vortices are convected downstream: the transition from one-row primary vortex street to the two-layered vortices, and the transition from two-layered vortices to the secondary vortex street. The latter is only observed in the wake of a finned cylinder with 3–5 ribs at Re = 180, while the two-layered vortices are decayed in the far wake in other cases.

Effects of the position of pipe-type appendages on the flow induced motions, energy transformation, and drag force of a TLP

Flow-induced motions (FIM) can cause fatigue damage to the mooring and riser systems of deepwater offshore structures, especially for cylindrical platforms, such as Tension Leg Platform(TLP). Previous experimental and numerical studies have showed conservative FIM prediction compared to the field measurements, due to many significant factors such as the Reynolds number, the nonuniformity of the incident current, the unsteadiness of the current velocity and platform heading, the coupled current and wave presence. Besides, the appendages covering the hull surface of platforms also played an important role in the smaller FIM responses of the field measurements. In order to specifically examine the influence of position of pipe-type appendages, this paper experimentally investigated the FIM of a TLP with different positions of appendages at 0°-incidence and compared the FIM responses, energy transformation, and average drag coefficients with those of the bare hull. An air-bearing system and a horizontal mooring system were employed to provide vertical pretension and horizontal restoring forces, respectively, and to ensure the low-friction horizontal motions. The results showed that for 0°-incidence whatever the appendages position, the transverse and yaw motions were all mitigated and the TLP with appendages-45° was the most effective configuration, with a reduction of 55% for the transverse motion and 52% for the yaw motion, mainly owing to the changes of the boundary layer separation point. However, the analysis of energy transformation indicated the development trend of the galloping phenomenon for the TLP with appendages-45°. In addition, the influence of the FIM behavior on the drag force of the TLP at 0° 22.5° and 45°-incidences was also studied. It showed that the FIM could contribute to larger drag force and the increase of drag force is the most significant at 0°-incidence, with a value of around 39%.

Effect of Non-uniform Magnetic Field on Non-newtonian Fluid Separation in a Diffuser

The purpose of the present study is to investigate the boundary layer separation point in a magnetohydrodynamics diffuser. As an innovation, the Re value on the separation point is determined for the non-Newtonian fluid flow under the influence of the non-uniform magnetic field due to an electrical solenoid, in an empirical case. The governing equations including continuity and momentum are solved by applying the semi-analytical collocation method (C.M.). The analysis revealed that for specific values of De from 0.4 to 1.6, α from 20o to 2.5o and Ha from zero to 8, the Re value on the separation point is increased from 52.94 to 1862.78; thus, the boundary layer separation postponed. Furthermore, the impact of the magnetic field intensity on the separation point is analyzed from the physical point of view. It is observed the wall shear stress increases by increasing magnetic field intensity that leads to delaying the boundary layer separation.

Numerical study of cavitation regimes in flow over a circular cylinder

Cavitating flow over a circular cylinder is investigated over a range of cavitation numbers for both laminar and turbulent regimes. We observe non-cavitating, cyclic and transitional cavitation regimes with reduction in freestream $\sigma$. The cavitation inside the Karman vortices in the cyclic regime, is significantly altered by the onset of "condensation front" propagation in the transitional regime. At the transition, an order of magnitude jump in shedding Strouhal number is observed as the dominant frequency shifts from periodic vortex shedding in the cyclic regime, to irregular-regular vortex shedding in the transitional regime. In addition, a peak in pressure fluctuations, and a maximum in St versus $\sigma$ based on cavity length are observed at the transition. Shedding characteristics in each regime are discussed using dynamic mode decomposition. It is demonstrated that the condensation fronts observed in the transitional regime are supersonic (referred as "condensation shocks"). In the presence of NCG, multiple condensation shocks in a given cycle are required for complete cavity condensation and detachment, as compared to a single condensation shock when only vapor is present. This is explained by the reduction in pressure ratio across the shock in the presence of NCG effectively reducing its strength. In addition, at $\sigma=0.85$ (near transition from the cyclic to the transitional regime), presence of NCG suppresses the low frequency irregular-regular vortex shedding. Vorticity transport at $Re=3900$, in the transitional regime, indicates that the region of attached cavity is nearly two-dimensional with very low vorticity, affecting Karman shedding in the near wake. In addition, the boundary-layer separation point is found to be strongly dependent on the amounts of vapor and gas in the freestream for both laminar and turbulent regimes.

An investigation of airfoil dual acoustic feedback mechanisms at low-to-moderate Reynolds number

An experimental investigation was performed in an anechoic wind tunnel involving acoustic measurements, hot-wire anemometry and surface flow visualisation techniques to investigate airfoil tonal noise generating mechanisms. Tests were conducted using a NACA 0012 airfoil at corrected angles of attack of 0° and 1.58° and Reynolds numbers of 50,000 to 150,000. A dual acoustic feedback model is presented, where feedback processes act independently on the airfoil pressure and suction surfaces between the point of boundary layer separation and the trailing edge. It is proposed that the tones generated on both airfoil surfaces, with the same or similar frequencies on each surface, interfere constructively. The primary tone possesses near exact frequencies on both surfaces, whereas the secondary tones have larger differences in frequencies between both surfaces, thus explaining their relative magnitudes based on acoustic superposition. This model provides a better comparison with the experimentally obtained tonal frequencies than the existing feedback models. Despite this agreement, the feedback model cannot perfectly predict the acoustic tones as the tones are not perfectly equispaced. An empirical feedback length is calculated by reverse engineering an acoustic feedback length scale by using the recorded primary tone as an input that also minimises the secondary tone prediction errors. This empirical length closely matches the dual acoustic feedback model presented in this paper.

PIV analysis of near-wake flow patterns of an ice-accreted bridge cable in low and moderately turbulent wind

The study contributes to the explanation of flow behaviour and the basis of phenomena existing during two-dimensional airflow around an ice-accreted cylinder, representing the section model of a bridge cable. The geometrical features and flow characteristics of the near-wake flow patterns of the iced cable were investigated within the Reynolds number range of 2.2·104–6.4·104 in low and moderately turbulent flow. The experimental procedure was conducted to create ice accretion on the cylindrical model. The shape of the ice was registered using a photogrammetry method. For the aerodynamic investigations the ice-accreted model was reproduced at a smaller scale by means of 3D printing. Representative snapshots of the flow field behind the stationary horizontal simulated iced cable were digitally analyzed by the Particle Image Velocimetry technique. The flow visualization provided quantitative data about the velocity and the direction of flow streams within both the near-wake and the sidewise regions of distributed flow around the model. Evidence of the existence of the vortex excitation process was obtained at three principal angles of attack. The characteristics of the vortex street and the location of the flow boundary layer separation points were recognized. The obtained results were compared with results for a smooth cylinder.