Vortex Generators Research Articles

Investigating the impact of different SCWSVGs arrangements on thermo-hydrodynamic flow within pillow-plate type heat exchanger

This paper introduces an innovative approach aimed at enhancing heat transfer while simultaneously reducing pressure loss in the Pillow-plate type heat exchanger (PPHE) through the utilization of circular welding spots (CWS) with a dual role as vortex generators (VG) and convergent/divergent features. The VGs, strategically positioned in a configuration termed “SCWSVGs” (Staggered circular welding spot vortex generators), are fixed in place to augment heat transfer. This configuration results in an amplified heat transfer coefficient, increased turbulence, and intensified vortices and secondary flow behind the SCWSVGs. The effectiveness of this enhancement strategy is validated through comparisons with experimental data, correlations, and various channel arrangements. Furthermore, the study investigates the impact of SCWSVGs diameters and streamwise pitches (XL) by exploring the variation in the hydraulic diameter to streamwise length ratio (dh/XL) within the range of 0.036 to 0.070. Key parameters in the dataset include Nu, f, (Cx/Cx0)0.33, normalized heat transfer factor (St/St0), RAF, and TEF. Notably, at 1,000 ≤ Re ≤ 16,000, the highest and lowest heat transfer rates are observed for cases 1–5 and cases 15–20, respectively. The (Nu/Nu0)/(f/f0)0.33 reaches up to 67 %, while f decreases by 9 % (Re = 1,000) to 10 % (Re = 16,000) based on two times the streamwise length (XL). Varied XL values result in significant differences in Nu, highlighting the superior performance of PPHE compared to a smooth enclosure channel.

Improving flight performance of UAVs by ice shape modulation

Aircraft icing poses a great threat to flight safety. In response to the characteristics of high-power consumption, large volume, and heavy weight of traditional anti-/de-icing technologies, the concept of ice shape modulation is proposed, which is called ice tolerant flight. Firstly, the flight performance of Unmanned Aerial Vehicle (UAV) was compared in three states: no ice, full ice, and modulated ice through flight tests. It was found that ice shape modulation has a significant improvement effect on the aerodynamic performance of aircraft under icing conditions. Under the three modulated ice shape conditions in this experiment, the lift coefficient of the UAV under different ice shape modulation conditions increased by 18%–33%, and the stalling angle was delayed by 3°-5°. Subsequently, the pressure distribution, streamlines in the flow field, and detached vortex distribution of the UAV model in these three states were obtained through numerical simulation, to study the mechanism of ice shape modulation on the aerodynamic performance of aircraft. The simulation found that the reason for the improvement of the wings effect after ice shape modulation is that the modulated area forms a leading-edge protrusion structure similar to a vortex generator. This structure prolongs the mixed flow region on the wings surface and reduces the trend of flow separation, which plays a role in increasing lift and reducing drag for UAVs under icing conditions. Finally, a reverse reachable set that can be used for unexpected state recovery is used as the definition of flight safety boundaries, and an aircraft dynamics model is established to obtain flight safety boundaries for different states. Research has found that the flight safety boundary of the UAV in a no ice state is greater than that in a modulated ice state, and the safety boundary in a modulated ice state is greater than that in a full ice state. Compared with the full ice state, the flight safety boundary after modulation has expanded by 27.0%. The scheme of ice shape modulation can provide a basis for the flight safety of aircraft under icing conditions.

Energy Harnessing Performance of Oscillating Foil Submerged in the Wake of a Fixed Cylinder

The energy harnessing from flow-induced vibrations (FIV) by an oscillating foil placed tandemly behind a circular cylinder (which serves as a vortex generator) is investigated. The foil is submerged in the wake produced by the fixed cylinder and could oscillate in the direction perpendicular to the incoming flow with single-degree freedom. The spacing ratio ranges from 1.0 to 5.0. The oncoming fluid velocity is U = 1–10 m/s, corresponding to the reduced velocity Ur = 3.81–38.08 and the Reynolds number Re = 9.58 × 103–9.58 × 104. Four harnessing damping ratios (ζharness = 0.0054–0.0216) are used to simulate the energy conversion conditions. The main conclusions are: (1) The optimal oscillation pattern related to the highest harnessed energy emerges as the spacing ratio close to 1.0. (2) The airflow energy converted by the foil is positively correlated with the harnessing damping ratio because the amplitude responses are similar at various harnessing damping ratios. A high velocity yields the highest harnessed power. (3) The harnessing efficiency of the foil could reach 48.89%, which is much more than that of an isolated flapping foil.

Temperature uniformity analysis and multi-objective optimization of the microchannel heat sink with cavities under longitudinal vortex flow

With the development of electronic devices toward a more centralized direction, there is an urgent need to introduce new technologies in the microchannel heat sink to address thermal deformation or failure caused by uneven temperature distribution. Therefore, microchannels with longitudinal vortex generators (LVGs) and different shapes of cavity structures combination are designed innovatively to address this issue. The laminar flow solver solves for single-phase, steady, and fully developed liquid flows through microchannels in the inlet Reynolds number range of 168–793. Study finds that the longitudinal vortex flow not only mixes the fluid in the mainstream region but also effectively weakens the retention effect in the cavities. Among all microchannels, the microchannel with LVGs and triangular cavities combination (MC-LTC) shows the best performance. Subsequently, multi-objective optimization of the MC-LTC is carried out using Non-dominated Sorting Genetic II Algorithm with the pumping power (Pp) and the temperature uniformity factor (E) as objective functions, and the relative heights (α, β, γ) of the three pairs of LVGs as the three design variables. The optimal solutions set for Pp and E range from 0.706 mW to 1.018 mW and 0.547 to 0.716, respectively. Among the five selected Pareto optimal solution parameters, MC-LTC (α = 0.6001, β = 1.3528, γ = 1.3707) and MC-LTC (α = 0.6001, β = 1.0725, γ = 1.3017) show the best temperature uniformity performance.

Effect of structure parameters on thermal performance of novel punched V-shape VGs for hear exchangers: An experimental approach

The use of perforated technology on the surface of the vortex generator (VG) has been proven to further enhance heat transfer performance by reducing its pressure loss. Based on this technology, a new type of turbulence insert is proposed in this work, which is composed of a V-shaped fixed ring with perforated rectangular VGs. The influence of its number (N = 2, 4, 6), VG area (S = 10, 20, 30 mm2), and pitch (P = 25, 50, 75 mm) on heat transfer and pressure drop under turbulent conditions was investigated through experiments. The results show that the influence of N and S on heat transfer intensity and pressure drop is consistent, but the value of P is inversely proportional to pressure drop and heat transfer intensity. Regardless of the influence of parameters on heat transfer intensity, it is explained by the field synergy number. Within the parameter range studied in this article, the optimal TEF value of 1.42 is attained when S=10mm2, N = 6, and Re=7454.

The effect of vortex generators having Clark-Y airfoil on tapered swept-back wing

In the experimental study, the effects of vortex generators (VGs) having Clark-Y airfoil and triangular VGs are investigated. The tests were carried out on a tapered swept-back wing at Re = 6.0×104 using counter-rotating vortex generators having Clark-Y airfoil at five different locations that are x/c= 0.1, 0.2, 0.3, 0.4, and 0.5 and triangular VGs at x/c=0.1 location. A load cell is used to measure forces at angles of attack (AoA) ranging from 0° to 30°. It is observed that the maximum lift coefficient (CLmax) and aerodynamic performance of VGs having Clark-Y airfoil decrease when the position of the vortex generators changes from 0.1 to 0.5. The optimal results obtained from the study show that the tapered swept-back wing with the VGs having Clark-Y airfoil exhibits a significant increase of 37.5% in the CLmax and approximately 55% in the lift to drag ratio (L/D) at x/c=0.1 compared to the baseline. At low AoA, the VGs having Clark-Y airfoil provided better lift, whereas at high AoA, the triangular VGs provided better lift.

Multi-objective hydrothermal performance optimization of a microchannel heat sink equipped with delta winglet vortex generators using NSGA-II genetic algorithm

Microchannel heat sinks provide the solution to the ever-increasing heat flux generated from micro-electric components. In this study, performance optimization of a microchannel heat sink with delta winglet vortex generators was carried out based on the data obtained from numerical CFD simulations. A total of 192 design points were generated by altering the fluid velocity in terms of Reynolds number (Re), winglet width (Wd), length (Ld), and the angle of attachment (β) of the winglet. The Artificial Neural Network (ANN) model coupled with Non-dominated Sorting Genetic Algorithm NSGA-II was used simultaneously to minimize the friction factor and increase the Nusselt number. The ANN model predicted the output values within the error limit of 10%. The Pareto optimal front generated by the algorithm contains the input parameters in the range 982 < Re < 988, 177 μm <Ld < 233 μm, 10 μm <Wd < 25 μm, 57° <β < 64°. Decision-making methods TOPSIS, LINMAP, and Shannon entropy were employed to calculate the optimal solution from the data set and the obtained points showcased 70%, 120% and 158% surge in Nusselt number while an increase of friction factor by 35%, 109%, and 140% respectively is reported. The Performance Evaluation Criteria (PEC) values obtained from the best solutions were 1.52, 1.72, and 1.92, respectively. Furthermore, the accuracy of the optimal solutions was verified numerically. The flow and thermal field of the microchannel are also analyzed, and results showed that the angle of attachment and width of the winglet played a crucial role in the overall performance.

Numerical analysis of microchannel heat sink performance using delta vortex generator

The design of unique microsinks arises from the desire to provide efficient cooling at low pressure drop for a more compact miniaturized electronic equipment. Three-dimensional numerical investigations of heat transfer and fluid flow have been carried out with delta vortex generator (DVG) structures in the rectangular microchannel. A pair of delta vortex generators (DVGs) are placed symmetrically about the horizontal mid plane in rectangular microchannels. Performance variances are assessed on the basis of the average Nusselt number (Nu), friction factor (f), and thermal performance (TP) along with the thermal resistance (RT) and hydraulic resistance (RH) for the Reynolds number in the range of 93 to 746. The parametric variation has been carried out by altering geometric parameters such as the angle of DVGs with centerline (θ), the number of pair of DVGs (n), the length of DVGs (l), the distance of DVGs from the centerline (B), the position of DVGs from the inlet for first pair (L1), and the distance between the vortex generators (S). The objective is kept to maximize the TP, to minimize the value of thermal resistance, and to decrease the increase in the hydraulic resistance for the same geometrical variation. The highest thermal performance equal to 1.256 has been achieved with the combination of θ, n, l, B, S, and L1 equal to 45°, 3, 0.6 mm, 0.1 mm, 4.5 mm, and 5.334 mm, respectively. For the same geometrical parameters, a minimum thermal resistance equal to 0.98 K/W and a hydraulic resistance equal to 3.234 kPa-min/ml have been attained at Re about 745.66. By minimizing the thermal and hydraulic resistance of the microchannel with DVGs, it becomes possible that heat can be more effectively transferred across the interface and the desired cooling can be achieved with less power input. The implementation of DVGs enhances intermixing through the generation of longitudinal and transverse vortices, leading to a more evenly distributed temperature across the channel. This enhancement in the heat transfer reduces the thermal resistance. Additionally, the vortices generated by DVGs modify the velocity profile, thereby decreasing the pressure drop and the hydraulic resistance. The specific impact of longitudinal vortices on the enhancement of the heat transfer through adjustments in geometric parameters is thoroughly elucidated.

Numerical study of the use of shear-thinning nanofluids in a microchannel heat sink with different pin densities and including vortex generator

This article numerically investigates the thermal and hydraulic performance of shear-thinning nanofluids when used as heat-conducting fluids in a microchannel heat sink device. Five geometries are evaluated: four with different pin densities and one with vortex generators. Six Reynolds numbers are studied, ranging between 200 and 1200. Numerical experiments show a comparison of using a water/ethylene-glycol mixture with and without alumina nanoparticles and multiwalled carbon nanotubes. Two different concentrations of nanoparticles were evaluated, both given shear-thinning nanofluid behavior. The viscous properties of the fluids are fitted from previously reported experimental data. The other thermophysical properties are modeled using single-phase expressions adjusted to consider hybrid nanofluids. Numerical results show that the heat transfer rates and pressure drop increase when the pin density increases, resulting in thermal blocking in the case of higher pin density. These key findings are a result of the increase in the heat transfer of shear-thinning nanofluids and the reduction of the pressure drop when compared with Newtonian fluids. Apparent viscosity contours are used to understand the thermal and hydraulic performance. Between the two nanofluids studied, the one with the lowest power-law index was the best in terms of heat extraction and pressure drop, indicating that fluids with thinning rheology may be recommended for heat transport in microchannel heat sink devices.

Propagation of optical vortices in an add-drop resonator based on a vertical array of ring resonators

Propagation of optical vortices in an add-drop resonator based on a vertical array of ring resonators

Insight into blade tip vibration and deformation characteristics of boiler circulation pumps induced by tip leakage vortex under different tip clearances

For circulating pumps in large power plant boilers, tip leakage flow is the main cause of blade fatigue. To investigate the correlation between tip leakage vortex and blade fatigue, in this paper, the bidirectional fluid structure coupling method is used to simulate the full flow field of the boiler circulating pump under different tip clearance sizes. The accuracy of the delayed detached vortex simulation method is verified by combining the external characteristics and vibration characteristics of the pump. It is obtained that tip leakage vortex is the main cause of blade tip vibration and deformation. Under deep stall conditions, the increase in tip clearance size suppresses the vibration displacement of the blade leading edge, while the opposite is true under optimal conditions. After decomposing tip leakage vortex, it is found that the compression–expansion term played a major role in the deformation of the blade tip, while the viscous dissipation term and the stretching term mainly affected the vibration frequency. At optimal working conditions, the main frequency of blade vibration is basically consistent with the main frequency of vortex generation. In deep stall condition, as the tip clearance size increases, the amplitude of the vibration main frequency decreases and the number of harmonic frequencies decreases, while the optimal condition is the opposite.

Vortex shedding from a square cylinder interacting with an undular bore wave train

In this work, we studied the wave-induced vortex generation and shedding from a semi-submerged vertical square cylinder interacting with an upcoming undular bore wave train under a shallow water configuration. This unsteady and rapid process was investigated by means of numerical and experimental approaches. A numerical simulation, solving the full turbulent viscous Navier–Stokes equations, was carried out in order to study and characterize both the undular bore wave properties and the vortex dynamics triggered during this unsteady interaction. Starting with fluid at rest, the undular bore was generated by the impulsive translational motion of a piston wavemaker at laboratory scale in both a numerical and an experimental wave tank. When the undular bore impinges on the cylinder, filamentary vortex structures were formed at the four cylinder's edges synchronized with the propagating wave motion, leading to the vortex shedding phenomena at a frequency that matched the wave instantaneous frequency. These vortices extended along the entire cylinder span under the water column, from the free surface to the seabed. At the trailing edge of the cylinder, a pairing process of two shed vortices was observed, similar to a Lamb–Oseen vortex pair. These vortices were present during the whole undular bore wave train dynamic forcing. An overall agreement was found with the experimental version of the bore–cylinder interaction, carried out in a physical wave tank. Laser sheet bore profiling and particle image velocimetry measurements of the velocity field confirmed undular bore properties, the onset of vortex formation, subsequent shedding, and pairing in the experiments performed in similar conditions with the numerical approach.

Study on the application of vortex generator to suppress ship propeller cavitation excitation

ABSTRACT A triangular vortex generator (VG) is used to suppress the hull vibration induced by propeller cavitation in this paper. Firstly, the numerical simulation method is used to simulate the original flow field around the ship, and the high wake area caused by the separation of the flow at the stern is analysed, which leads to serious cavitation on the propeller and induced hull vibration. Then, the effects of the installation angle and position of the VG on the wake of the ship are analysed, and the appropriate design parameters of the VG are obtained. Through the numerical simulation of cavitation on the propeller, the effects of VG on cavity shape and hull fluctuating pressure induced by cavitation are analysed. The VG can improve the non-uniformity of wake field, delay cavitation generation, and weaken the cavitation on the propeller tip area. The maximum reductions of the first, second, and third harmonics of fluctuating pressure are about −41.2%, −36.6%, and −78.5%, respectively. Finally, the vibration of each cabin of the full scale vessel is significantly reduced after the installation of the VG, especially in the cabin near the propeller. The reduction range is up to −54.5%, and a good vibration reduction effect is obtained.

Thermal performance augmentation in a pipe employing hybrid nanofluid and a plate as turbulator with V-shaped double-winglet ribs

This article employs a plate with V-shape ribs inside a tube as turbulator to augment the heat transfer rate. The utilized vortex generators are double-winglets arranged in a V-shape placed on both sides of the plate. The proposed system’s suggested working fluids are water-based hybrid nanofluids, including Al2O3–Cu/water, Cu–CuO/water, and Cu–TiO2/water. This work involves a numerical evaluation of the effects of the type and volume concentration of the examined hybrid nanofluids on the enhancement of heat transfer. The experimental results are used to validate the numerical model. It is worth mentioning that all the obtained numerical results are compared with the simple tube, without any turbulator (vortex generator) and in the presence of water instead of the hybrid nanofluids. Based on the numerical results, it can be concluded that all employed hybrid nanofluids showed improved thermal performance compared to pure water. Furthermore, the differences between the models are more substantial for higher Reynolds numbers than for lower Reynolds numbers. In Re = 30,000, the Cu–TiO2/water exhibits the lowest thermal performance improvement (augmentation of about 0.3%), while the Cu–CuO/water at Re = 50,000 exhibits the largest thermal performance improvement (augmentation of approximately 5.7%), in the case of ∅1 = ∅2 = 0.5%. For ∅1 = ∅2 = 1%, the Cu–TiO2/water at Re = 30,000 has the lowest thermal performance improvement (augmentation of around 1.1%), while the Cu–CuO/water at Re = 50,000 has the most thermal performance improvement (augmentation of roughly 8.7%). According to the augmentation of around 2.8% at Re = 30,000 for Cu–TiO2/water and approximately 10.8% at Re = 50,000 for Cu–CuO/water, the thermal performance increase in the scenario of ∅1 = ∅2 = 1.5% is the lowest. In Conclusion, the Cu–CuO/water hybrid nanofluid with a volume concentration of ∅1 = ∅2 = 1.5% has the greatest thermal performance value of all the hybrid nanofluids studied.

Generation of elliptical perfect optical vortex beams and their propagation in free-space.

We investigate the generation of an elliptical perfect optical vortex (EPOV) beam through the optical Fourier transformation of an elliptical Bessel-Gaussian beam and derive an analytical expression for its complex field amplitude. Our analysis includes the examination of the beam's propagation in free-space and the influence of topological charge on its transmission. The EPOV beam's propagation in free-space can be categorized into non-diffracting and diffracting stages. During the non-diffracting stage, the beam intensity and profile size are effectively preserved over a short transmission distance. Subsequently, in the diffracting stage, the beam profile initially contracts and then expands with a change in the beam intensity. Notably, the impact of topological charge on the beam intensity and profile size varies across different stages of propagation. We compare our results with those of the circular perfect optical vortex beam propagating in free-space, observing that the EPOV beam exhibits non-diffracting behavior for short propagation distances compared to its circular counterpart. The signature of the focusing behavior of the EPOV beam is observed at a relatively small propagation distance compared to the circular case.

Analysis of vortex mixing in passive micromixers with misaligned inlet and rectangular winglets

In the present study, a three-dimensional design of a passive micromixer is proposed which induces the swirling flow pattern by employing the misaligned inlets and winglets. The concepts of fluid stretching and twisting are utilized to improve the mixing efficiency. Stretching is quantified in terms of the modified flow tortuosity parameter. The dependence of various geometrical parameters on flow tortuosity is examined to increase the diffusive mixing by increasing the lateral Peclet number. A detailed analysis is carried out to understand the impact of geometrical features on the vortex formation, propagation, and intensification. Lambda 2 and the helicity approach are used to identify the vortex core region and quantified using a modified swirl number & vortex index. For vortex T misalignment, the aspect ratio 1 along with the staggered common flow-down configuration of winglets is highly effective. For misaligned Y inlet, both interfacial diffusive mixing along with longitudinal vortices at winglets generate highly effective mixing even at a low Reynolds number. For Reynolds number 1 to 70 and channel length 3.5 mm, mixing efficiency above 82% is achieved, and the mixing energy cost is subsequently reduced. A detailed comparative study is done to establish the effectiveness of the present design.

Numerical simulation analysis of high-temperature bent sodium heat pipes

Abstract High-temperature bent heat pipes are safety-level heat transfer components used in heat pipe cooled reactor, and their applications are becoming increasingly widespread. In this study, a comprehensive three-dimensional numerical model was established to evaluate the effects of different bending angles and radii on the performance of high-temperature heat pipes. The model solved for the temperature, pressure, and velocity fields in the wall, wick, and evaporator, considers the compressibility effect of the vapor. The study investigated parameters such as vapor pressure, vapor velocity, radial secondary flow field, wall temperature, wick temperature, and equivalent thermal resistance of powder sintered core sodium heat pipes with bending angles of 45°, 90°, 135°, 180°, and a bending radius under 90°. The results showed that when sodium vapor enters the bent pipe, the vapor flow deviates towards the outer side, resulting in higher vapor pressure at the outer side than the vapor pressure at the inner side, and the generation of radial secondary vortex. This leads to higher temperature in the evaporator and adiabatic sections of the bent heat pipe, while lower temperature in the condenser. Fractal patterns are observed in the outer and inner wall temperature curve in the adiabatic section, with lower temperatures on the inner side and higher temperatures on the outer side. The bent heat pipe exhibits higher equivalent thermal resistance than that of a straight heat pipe, and the equivalent thermal resistance increases with increasing bending angle, and the equivalent thermal resistance decreases with increasing bending radius.

Numerical study on the cavitation instability from the perspectives of pressure change and hydrodynamics evolution in the cavitating flow over a hydrofoil

The objective of this study is to investigate cavitation instability by analyzing the pressure change and hydrodynamics evolution in the cavitating flow over a hydrofoil. Two-dimensional (2D) simulation results indicate that the multi-peak pressure features are influenced by the position on the hydrofoil surface. The increased cavitation number in a certain range aggravates the oscillation of partial cavitation and promotes the cavity change, then leads to the occurrence of higher peak pressure and more complicated fluctuation frequency. The lift coefficient presents a near-linear increasing trend due to the extended low-pressure area on the suction surface and the suppression on the vortex generation in the stable development stage of sheet cavity. The interaction between the vortex with different directions on the trailing edge dominates the fluctuation of lift coefficient. The differences in three-dimensional (3D) cavitating flows with constant velocity inlet and sinusoidal velocity inlet are the flow separation point distribution and vortex changes. More separation points form in the downstream of the hydrofoil due to more cloud cavity reattachment behaviours for sinusoidal velocity inlet. Furthermore, the sinusoidal velocity inlet promotes a more violent cavity detachment and the large-scale vortex formation, which enhances the fluctuations of pressure change, lift and drag coefficient.

The influence of magneto-hydrodynamics and vortex generators on nanofluids heat transfer

This paper investigates the effects of a vortex generator (VG) and magneto-hydrodynamics (MHD) on the thermal properties of nanofluids in a microchannel. A variety of test scenarios within the laminar flow regimes are numerically examined: nanofluids in a hot-walled simple channel (SC); nanofluids in a heated-walled channel where a circular cylinder is embedded within the channel and functions as a vortex generator (VG); nanofluids in a heated-walled channel that incorporates both a vortex generator and magneto-hydrodynamics (VG-MHD). The channel has a circular cylinder with a diameter of D that is fixed inside the channel with various gap ratios (GR = G/D) ranging from 0.5 to 4.0. Numerical investigations for laminar flow with Re ≤ 1,000 are carried out. The nanoparticle volume fractions range from 0 % to 7 %, and the magnetic field is set at 0.05 T. The best heat transmission conditions with the lowest skin friction coefficient are evaluated for the optimal GR. It is found that heat transfer is enhanced by approximately 20 % when MHD and VG effects are employed, in contrast to a traditional channel that does not utilize the MHD effect.

Turbulent transports in the flow around a rectangular cylinder with different aspect ratios

The flow around a rectangular cylinder exhibits intricate features, encompassing phenomena such as separation, reattachment, boundary layer transition, and relaminarization. This study explores the intense transport of turbulent fluctuations in these complex flow phenomena, including momentum and turbulent kinetic energy (TKE) transport, for three aspect ratios (L/D=5,10 and 15) at a medium Reynolds number (Re=1000). The connection between these transports and crucial vortical structures is elucidated for the first time. On the lateral side of the cylinder, strong momentum transport occurs, dominated by ejection and sweep events associated with the hairpin vortex. The generation of the LE vortex also leads to active TKE production. The existence of the LE separation bubble, as well as the relaminarization of the downstream boundary layer at L/D=10 and 15, affects the distribution of production terms. This perspective offers an effective yet novel approach that has not been previously addressed in prior researches. The redistribution of TKE results in a disturbance growth, linked to boundary layer transition. The source term reveals that streamwise TKE carried into the recirculating region is closely related to the frequency prior amplified by the LE shear layer. In the wake behind TE, turbulent transports are influenced by vortex shedding patterns.