Slotted Scheme Research Articles

Study on the Influence of Different Slot Sizes on the Flow Field of Transonic Compressor Rotors

Blade slotting technology is an effective measure to improve the flow structure on the suction surface of a blade and enhance the performance of turbomachinery. To investigate the impact of various slot sizes on the flow field of a single-stage transonic compressor rotor, seven kinds of slot schemes were designed and calculated by numerical simulations. The results show that the above slotting schemes significantly enhance the stability margin of the compressor. In particular, the slotting scheme H9W3 increases the surge margin by 60.9% and slightly reduces peak efficiency by 0.3%, with an almost identical maximum pressure ratio. Slotting promotes high-energy fluid to generate jets from the slot located at the exit of the suction side, effectively controlling blade surface flow separation and reducing channel blockage. Square slots are more effective than elongated slots for controlling separation when using differently shaped slots with equal areas. Increasing slot area gradually decreases outlet total pressure at a constant aspect ratio. A slight increase in the overall blade load causes a backward shift in the front portion load.

Investigation of control effects of end-wall self-adaptive jet on three-dimensional corner separation of a highly loaded compressor cascade

To overcome the limitations posed by three-dimensional corner separation, this paper proposes a novel flow control technology known as passive End-Wall (EW) self-adaptive jet. Two single EW slotted schemes (EWS1 and EWS2), alongside a combined (COM) scheme featuring double EW slots, were investigated. The results reveal that the EW slot, driven by pressure differentials between the pressure and suction sides, can generate an adaptive jet with escalating velocity as the operational load increases. This high-speed jet effectively re-excites the local low-energy fluid, thereby mitigating the corner separation. Notably, the EWS1 slot, positioned near the blade leading edge, exhibits relatively low jet velocities at negative incidence angles, causing jet separation and exacerbating the corner separation. Besides, the EWS2 slot is close to the blade trailing edge, resulting in massive low-energy fluid accumulating and separating before the slot outlet at positive incidence angles. In contrast, the COM scheme emerges as the most effective solution for comprehensive corner separation control. It can significantly reduce the total pressure loss and improve the static pressure coefficient for the ORI blade at 0°-4° incidence angles, while causing minimal negative impact on the aerodynamic performance at negative incidence angles. Therefore, the corner stall is delayed, and the available incidence angle range is broadened from −10°–−2° to −10°–4°.This holds substantial promise for advancing the aerodynamic performance, operational stability, and load capacity of future highly loaded compressors.

Controlling secondary flow in high-lift low-pressure turbine using boundary-layer slot suction

The design of high-lift Low-Pressure Turbines (LPTs) causes the separation of the boundary layer on the suction side of the blade and leads to a strong secondary flow. This present study aims to minimize secondary losses through endwall slot suction and incoming wakes in a front-loaded high-lift LPT cascade with Zweifel of 1.58 under low Reynolds number of 25000. Two slotted schemes for the boundary layer of the endwall were designed (Plan A and Plan B), and the effects of suction mass flow on secondary flow were studied. The underlying physics of the endwall boundary layer of the suction and secondary flow under unsteady wakes was discussed. The results show that slot suction at the endwall boundary layer can significantly suppress the secondary flow by removing low-momentum fluids. Plans A and B significantly reduced the secondary kinetic energy by 44.2% and 36.9%, respectively, compared with the baseline cascade at the suction mass flow ratios of 1%. With an increase in the mass flow ratio of suction, the secondary flow was gradually reduced in both Plans A and B. It is more beneficial to control the secondary flow to destroy the intersection of the pressure side and suction side of the horseshoe vortex before it develops into a passage vortex. Under unsteady wakes, the combined effects of incoming wakes and endwall boundary layer suction can further suppress the secondary flow at the suction mass flow ratios of 2% for Plan A, because the positive and negative vorticity inside upstream wakes accelerated the mixing of the main flow and secondary flow and thus increased the energy of secondary vortices.

Effect of combined boundary layer suction on the separation control in a highly loaded transonic compressor cascade

A numerical investigation is conducted to explore the potential of combined slot suction in controlling the shock wave and flow separation in a transonic compressor cascade. The three slots in the combined scheme are arranged in different directions on the suction surface and endwall. The locations are determined by the shock wave and separation point in the baseline cascade. Based on these locations, two combined schemes and three single schemes are provided to explore the control mechanism. For each suction scheme, five bleed mass ratios are examined at the same inlet Mach number. The results suggested that the cascade throughflow loss could be decreased by three single schemes. However, the cascade performance is improved slightly or even deteriorated when the losses generated by the suction are considered. The key reasons are the local effects of single scheme and the opposite trend between corner stall and the suction surface separation. Both corner stall and the suction surface separation are eliminated by the combined scheme with two slots, and the maximum reduction in throughflow losses is 75%. The new corner separation evolved from the horseshoe vortex limited the performance of combined scheme. When the bleed mass ratio excided 5%, the combined scheme with three slots is better than the two slots scheme in loss control. The reason is the improved endwall boundary layer and the eliminated new corner separation. By inducing the horseshoe vortex into the slot, the interaction of the two endwall slots eliminates the new corner separation.

Effect investigation of single-slotted and double-slotted configurations on the corner separation and aerodynamic performance in a high-load compressor cascade

Controlling the corner separation through blade-end slotting has been widely proven advantageous in compressors. This study proposed a new double-slotted configuration and deeply revealed its benefits and flow control mechanisms by compared with the single-slotted configuration. Based on a high-load compressor cascade, the Slotted_A scheme with a single blade-end slot1 and the Slotted_B scheme with a smaller slot2 behind the slot1 were established and detailedly evaluated. The results showed that, since the slot jet with high momentum has efficacious re-energizing effects for the local low-energy fluid, both the two slotted schemes can prevent the original cascade from entering the corner stall condition. But the slot2 jet can further control the end-wall secondary flow developing and separating behind the slot1 in the Slotted_A cascade. Therefore, the Slotted_B scheme behaves better in controlling the corner separation than the Slotted_A scheme, resulting in larger turning angles, smaller vortex structures, and weaker flow blockage. As a whole, the Slotted_A scheme and Slotted_B scheme can respectively increase the turning angle by an average of 0.93° and 1.53°, improve the static pressure coefficient by 18.2% and 21.7% on average, and achieve an average reduction of 38.3% and 43.7% in the total pressure loss. In contrast, the Slotted_B scheme is more advantageous in improving the pressure diffusion capacity and stability margin for the high-load compressor blade.

PERFORMANCE ANALYSIS OF IEEE 802.15.4 CHANNEL ACCESS MECHANISMS DURING EVENT DETECTIONS IN WIRELESS SENSOR NETWORKS

The IEEE 802.15.4 protocol defines the medium access control layer of Zigbee, a widely implemented WSN technology. This protocol implements both the guaranteed time slot (GTS) scheme, where note request for slot(s) to transmit their packets collision-free and the contention-based scheme where nodes randomly draw a back-off counter to win channel access. This paper analyzes the performance of both schemes in WSNs when an event is detected and the packet arrival rate of the network increases using packet delivery ratio(PDR), network throughput and packet latency as the quality of service parameters. We consider various network densities (4, 9 and 16 nodes within a common transmission range). Simulations using Castalia 3.2 shows the GTS scheme has better PDR and latency than the contention-based scheme in the 4 and 9 nodes network. However, in a dense network (16 nodes), when the packet arrival rate increases, the contention-based scheme outperforms the GTS scheme.

Time allocation improvement method for UAV-based wireless energy transfer cooperative mobile edge

Wireless power transfer (WPT) and mobile edge computing (MEC) are two advanced technologies that could improve the computing power and range of mobile devices. However, by integrating the unmanned aerial vehicle (UAV) into wireless powered MEC systems, wireless energy transfer will be susceptible to the “double near–far” effect. Therefore, in order to further overcome the influence of the “double near–far” effect, this paper considers the optimization of time slot allocation for UAV-assisted wireless powered cooperative MEC system, which includes an access point (UAV) and two mobile devices. The purpose of the study is to minimize the total transmission energy of the UAV while satisfying the delay and size of the computational tasks, so this paper proposed a 2:1:1 time-slot optimization allocation method. The method exploits the synergy of users so that the mobile device which is closer to the UAV acts as an offloading relay, by combining power and time slot optimization to minimize the total energy consumption of the UAV. Compared with the equal time slot scheme before the improvement, this method can not only utilize the wireless transmission energy to charge the mobile device for more time in the first period, but also can save the time of data transmission of the closer device in the third period, and it can enhance the rate of data transmission of the mobile devices at the same time. The results show that the task capacity of the system computed will be increased compared to the original scheme; the total transmission rate of the whole system is also improved by the same order of magnitude. The simulation results verify the effectiveness and reliability of the algorithm of the paper, and the comprehensive performance of the system can be maximized by the flexible offloading algorithm.

Investigation of the film-cooling and flow characteristics of trapezoidal slot scheme on the blade tip with partial pressure side squealer in transonic flow

The present work first introduces and studies the blade tip with a discrete trapezoidal slot scheme. The film-cooling characteristics of the discrete trapezoidal slot scheme on the blade tip with the partial pressure side squealer and full suction side squealer is experimentally investigated by the Pressure Sensitive Paint technique in transonic flow. The effects of the mass-flow-ratio and tip-clearance-gap are investigated, and the experiment is carried out at four mass-flow-ratios of 0.1% + 0.05%, 0.14% + 0.07%, 0.17% + 0.085%, and 0.21% + 0.105% and three tip-clearance-gaps of 0.7%, 1.1%, and 1.5%. The cascade exit Mach numbers is 1.05. The flow characteristics of the blade tip is studied by the calculation. The results indicate that the coolant can cover the whole blade tip bottom surface at the tip clearance of 1.5% and high mass-flow-ratios; With the tip-clearance-gap increasing, the adiabatic film effectiveness near the squealer rim of the suction side is significantly improved; The adiabatic film effectiveness near the leading edge at the small tip-clearance-gap is higher than that at the large tip-clearance-gap under the mass-flow-ratio of 0.1% + 0.05% condition due to the mainstream-blockage-effect; With the tip-clearance-gap increasing, the high aerodynamic loss coefficient region is significantly enlarged. At three tip-clearance-gaps, changing the mass-flow-ratio shows a slight effect on the aerodynamic loss coefficient distribution.

Combined flow control with full-span slot and end-wall boundary layer suction in a large-camber compressor cascade

To investigate combined flow control strategies with full-span slot and end-wall (EW) boundary layer suction, a large-camber compressor cascade was treated with a full-span slot configuration firstly. Then, two combined flow control schemes with different EW boundary layer suction slots were set up based on the full-span slot configuration. Finally, the performance of the baseline cascade and the slotted cascades was evaluated and compared numerically. The results show that the full-span slotted scheme can eliminate the trailing edge (TE) separation near the blade midspan and weakens the corner separation. However, the EW secondary flow still develops on the blade suction surface (SS) before the full-span slot outlet and separates to form the wall vortex (WV). In contrast, the two combined flow control schemes can effectively inhibit the development of the EW secondary flow on the blade SS, contributing to the smaller total pressure loss and stronger static pressure recovery capacity. Between them, the combined flow control scheme with full-chord-length EW suction slot behaves better. It can effectively eliminate the concentrated shedding vortex, WV and corner vortex in the cascade passage, and the passage vortex is also weakened to some extent. Therefore, the TE separation and the corner separation are basically eliminated. The total pressure loss, flow turning angle and static pressure coefficient can be increased by an average of −38.4%, 3.1° and 16.2% in the combined flow control cascade with full-chord-length EW suction slot respectively, which is beneficial for improving the stability margin and static pressure recovery capacity of compressor blades.

Impact Evaluation of Full-Span Slot and Blade-End Slot on Performance of a Large Camber Compressor Cascade

It has been proved that suitable slot structure of compressor slotted blade can generate high-momentum jet flow through pressure difference between the pressure and suction surface, the slot jet flow can reenergize the local low-momentum fluid to effectively eliminate the flow separation. In order to investigate and evaluate the impact of full-span slot and blade-end slot on the performance of the post-loaded blade, which has serious flow separation on the suction surface both near blade midspan and endwall, a diffusion stator cascade with large camber angle is selected as the research object. Firstly, the blade-end slotted scheme and the full-span slotted scheme are set up. Then the performance of datum cascade and two slotted cascades is computed in the wide incidence angle range of -8º to 6º at the Mach number of 0.7, the corresponding blade-chord-based Reynolds number 〖Re〗_C is 7.7×10^5. Finally, the performance of the three cascades is analyzed and compared. The results show that, in the computational incidence angle range, both of the two slotted schemes can reduce the total pressure loss for datum cascade and enhance its pressure diffusing capability. However, compared with the blade-end slot, the full-span slot has a better comprehensive control effect on the corner separation and the boundary layer separation near blade midspan, hence, compared with those of blade-end slotted cascade, the total pressure loss coefficients and the static pressure coefficients of full-span slotted cascade are respectively further decreased and increased. Under the blowing effect of full-span slot jet, the total pressure loss coefficients of datum cascade are significantly decreased, ranging as high as 21.2%, 23.1%, 24.5% and 23.4% under the incidence angles of 0°, 2°, 4° and 6°, respectively. The full-span slotted scheme has a better adaptability to wide incidence angle range, it can effectively broaden the available incidence angle range for datum cascade.

Swirling flow heat transfer and hydrodynamics in the model of blade cyclone cooling with inlet co-swirling flow

Swirling flow heat transfer and hydrodynamics were studied experimentally in the round passage, simulating the blade cyclone cooling. The smooth passage with one- and two inclined-tangential flow supply and the additional co-swirling flow at the inlet is considered. The Reynolds number, based on the average axial speed and passage internal diameter was ranged from 40 000 to 108 000, the co-swirling flow ratio Gd/GƩ was varied from 0 to 0.23. At Gd/GƩ ≤ 0.11 in the passage with one tangential slot the co-swirling flow influences weakly on the heat transfer enhancement and pressure drop ratio. In the passage with two slots, the Nud/Nud0 ratio drops down immediately from Gd = 0, moreover in this case the heat transfer is about 20% lower than that in the passage with one slot. At the identical total pressure in front of the passage, both schemes are comparable in terms of the total pressure losses. When pressure losses in swirl generators are taken into consideration at Gd = 0 two slots scheme demonstrates a greater Reynolds analogy factor than that for the one slot configuration. Also in terms of this factor, the two slots scheme looks better than the continuous and broken V-shaped ribs commonly used in the internal blade cooling. At Gd/GƩ > 0.5 - 0.6, the co-swirling flow reduces the heat transfer ratio and Reynolds analogy factor. In the passage with one inlet slot in the limited area of Gd/GƩ ratio, the pressure losses in the 90° exit bend are lower compared with the axial flow in the bend. In the passage with two slots in the entire range of Reynolds number, these losses are below those if the axial flow exists in the bend. This very attractive feature can be employed in the blade cyclone cooling design when the coolant discharges into the trailing edge area.

Passive Control with Blade-End Slots and Whole-Span Slot in a Large Camber Compressor Cascade

Suitable slot structure of the compressor blade can generate high-momentum jet flow through pressure difference between the pressure and suction surface, it has been proved that the slot jet flow can reenergize the local low-momentum fluid to effectively suppress the flow separation on the suction surface. In order to explore a slotted method for better comprehensive suppressing effects on the boundary layer separation near blade midspan and the three-dimensional corner separation, a diffusion stator cascade with large camber angle is selected as the research object. Firstly, the Slotted_1 and Slotted_2 whole-span slotted schemes are set up, then the Slotted_3 scheme with whole-span slot and blade-end slots is proposed, finally the performance of original cascade and slotted cascades is computed under a wide range of incidence angles at the Mach number of 0.7. The results show that: in the full range of incidence angles, compared with the whole-span slotted cascades, the development of the endwall secondary flow on the suction surface of Slotted_3 cascade is effectively suppressed, the degree of the mutual interference between the secondary flow and the main flow is reduced. Besides, on the suction surface of Slotted_3 cascade, the boundary layer separation near blade midspan and the corner separation are basically eliminated. As a result, compared with those of original cascade, the total pressure losses of Slotted_3 cascade are reduced in the full range of incidence angles, and its operating range of incidence angles is broadened. Moreover, compared with the whole-span slotted schemes, Slotted_3 scheme has a better adaptability to wide range of incidence angles.

Influence of endwall slotted injection on performance and flow physics in a compressor cascade

Air injection is an effectively methodology to suppress flow separation and to improve blade loading of airfoils and compressors. In order to remove corner separations in a cascade, investigation of endwall slotted injection was carried out numerically in this study. Based on endwall slot schemes of other flow control methods, six different endwall slots were designed, aiming at revealing the axial location effect and pitchwise location effect. For each endwall slot, numerical simulations were performed with six different injection directions to uncover the injection direction effect. Results showed that endwall slotted injection can effectively remove the corner separation. The overall loss coefficient and endwall loss coefficient of the cascade were reduced by 10.3% and 36.8% at most, respectively. Injection from leading edge and mid-chord can reduce endwall loss; however, the optimal axial location of endwall slot is near the trailing edge, where the corner separation is located. Different with other flow control methods, in general, the optimal pitchwise location of endwall slot is not close to suction surface but 0.16 pitch away from it. Injection near the suction surface is more sensitive to injection direction compared with injection at 0.16 pitch away from suction surface. Injection with velocity components both downstream and toward suction surface promises optimal control effect on corner separation. However, at mid-span, trailing edge separation is deteriorated and the flow turning angle is reduced, the flow mechanism being that the low-momentum fluid migrates along spanwise.

Energy efficient scheduling in local area networks

In Wireless Local Area Networks (WLAN), portable devices such as notebooks, tabs, and smart phones are powered by batteries with limited energy. With the great increase of using such portable devices, energy efficiency becomes one of the most important issues in wireless networks that are based on IEEE 802.11b standard. Although, IEEE 802.11b standard enables devices with limited batteries’ capacity to send and receive more data, it is not suitable for high load networks. In high load networks, Access Point (AP) cannot immediately deliver buffered packets to portable devices which leads to batteries’ drain as devices have to stay in active state for long time. Towards solving this great issue, an energy efficient downlink scheduling algorithm for WLAN is presented in this paper. The proposed scheduler aims to reduce the probability of medium contention and waiting time during the reception of buffered data packets from the AP without affecting the quality of service performance. The presented scheduler proposes a time slotted scheme to enhance the Power Saving Mode of IEEE 802.11b standard. The proposed approach is validated analytically and experimentally. Qualnet network simulator is used for this purpose. Promising results are obtained compared to legacy IEEE 802.11 protocol, and the Shortest Job First scheduler protocol in terms of energy saving, and throughput.

A Request-Transmission Splitting Scheme for V2X Networks: Design and Throughput Analysis

In the existing slotted ALOHA-based access schemes for vehicle-to-everything (V2X) networks, the duration of a time interval for competitive users contains the whole process of requesting and transmission. To improve the access capacity for V2X networks, unlike these schemes, we propose a request-transmission splitting slotted ALOHA-based scheme, referred to as the RTS-SA, in which a frame is divided into three phases. The first phase is short and utilized by vehicles when competitively transmitting their identities to roadside units (RSUs) for accessing requests in a coded manner. Then, RSUs implement multiuser detection and decoding simultaneously and act as the coordinator to broadcast the allocated time slots for the vehicles to guarantee contention-free transmission in the third phase. Compared to the VeMAC scheme, the RTS-SA can improve vehicles’ successful access performance compared to the VeMAC scheme, which is indexed by increasing the throughput. Simulation results verify the effectiveness of our proposed scheme.

Appointment overbooking with different time slot structures

Unattended appointments result in underperformance of a healthcare service provider. Such uncertainty in the appointment process not only lowers healthcare utilization and productivity but also hinders patients from having timely access to healthcare services and extends waiting time for receiving medical examinations or treatments. In this study, we formulate this stochastic optimization problem for appointment scheduling as its two-stage deterministic equivalent to simultaneously optimize overbooking and scheduling decisions to compensate patient no-shows with different time slot structures. We examine the impacts of three types of time slot structures, which are of fixed-length slot intervals, dome-pattern slot intervals and flexible appointment start times, on the efficiency of the system. With the optimal solutions found, we investigate the interaction between the time slot structure and the optimal overbooking solution. We found that the flexibility in appointment start times result in a “dome-dome-dome pattern with alternate long and short time slots” and could achieve a better patient experience (regarding the patient waiting time) while maintaining the same service provider efficiency (regarding the resource overtime and idle time), compared with the pre-defined time intervals. While there has been a large body of literature on appointment scheduling, to the best of our knowledge, this “dome-dome-dome” pattern has not been reported in the existing literature. Sensitivity analysis further shows that the flexible slot scheme is more effective when the number of overbooked patients is relatively low and the service duration is relatively long.

Short-Packet Two-Way Amplify-and-Forward Relaying

This letter investigates an amplify-and-forward two-way relay network (TWRN) for short-packet communications. We consider a classical three-node TWRN consisting of two sources and one relay. Both two time slots (2TS) scheme and three time slots (3TS) scheme are studied under the finite blocklength regime. We derive approximate closed-form expressions of sum-block error rate (BLER) for both schemes. Simple asymptotic expressions for sum-BLER at high signal-to-noise ratio (SNR) are also derived. Based on the asymptotic expressions, we analytically compare the sum-BLER performance of 2TS and 3TS schemes, and attain an expression of critical blocklength, which can determine the performance superiority of 2TS and 3TS in terms of sum-BLER. Extensive simulations are provided to validate our theoretical analysis. Our results discover that 3TS scheme is more suitable for a system with lower relay transmission power, higher differences between the average SNR of both links and relatively lower requirements on data rate and latency.

On the Modeling and Performance Assessment of Random Access With SIC

In this paper, we review the key figures of merit to assess the performance of advanced random access (RA) schemes exploiting physical layer coding, repetitions, and collision resolution techniques. We then investigate RA modeling aspects and their impact on the figures of merit for the exemplary advanced RA schemes: contention resolution diversity slotted ALOHA (CRDSA), irregular repetition slotted ALOHA (IRSA), coded slotted ALOHA (CSA) and enhanced spread-spectrum ALOHA (E-SSA). We show that the typical simplifications of the reception model when used to optimize RA schemes lead to inaccurate findings, both in terms of parameter optimization and figures of merit, such as the packet loss ratio (PLR) and throughput. We also derive a generic RA energy efficiency model able to compare the schemes in terms of the energy required to transmit a packet. The combination of achievable RA throughput at the target PLR and energy efficiency, for the same average user power investment per frame and occupied bandwidth, shows that E-SSA, which is an unslotted scheme, provides the best overall performance, while, in terms of the slotted schemes, CRDSA outperforms the more elaborated IRSA and CSA. This surprising results are due to the fact that the IRSA and CSA optimization has so far been performed using RA channel models that are not accurately reflecting the physical layer receiver behavior. We conclude by providing insights on how to include more accurate reception models in the IRSA and CSA design and optimization.

Self-Synchronization in Duty-Cycled Internet of Things (IoT) Applications

In recent years, the networks of low-power devices have gained popularity. Typically, these devices are wireless and interact to form large networks such as the machine to machine networks, Internet of Things, wearable computing, and wireless sensor networks. The collaboration among these devices is a key to achieving the full potential of these networks. A major problem in this field is to guarantee robust communication between elements while keeping the whole network energy efficient. In this paper, we introduce an extended and improved emergent broadcast slot (EBS) scheme, which facilitates collaboration for robust communication and is energy efficient. In the EBS, nodes communication unit remains in sleeping mode and are awake just to communicate. The EBS scheme is fully decentralized, that is, nodes coordinate their wake-up window in a partially overlapped manner within each duty-cycle to avoid message collisions. We show the theoretical convergence behavior of the scheme, which is confirmed through real test-bed experimentation.

Experimental Flow-Field Investigations Downstream a Scaled-Up Micro-Tangential-Jet Scheme Using the Particle Image Velocimetry Technique

This paper presents experimental investigations of the flow-field characteristics downstream a Scaled-Up Micro-Tangential-Jet (SUMTJ) film-cooling scheme using the particle image velocimetry (PIV) technique over a flat plate. The SUMTJ scheme is a shaped scheme designed so that the secondary jet is supplied tangentially to the surface. The scheme combines the thermal benefits of tangential injection and the enhanced material strength of discrete holes’ schemes compared with continuous slot schemes. The flow-field characteristics downstream one row of holes were investigated at three blowing ratios, 0.5, 1.0, and 1.5, and were calculated based on the scheme exit area. A density ratio of unity, a Reynolds number of 1.16 × 105, and an average turbulence intensity of 8% were used throughout the investigations. The performance of the SUMTJ scheme was compared to that of the circular hole scheme, base line case case, at the same test conditions and blowing ratios. From the investigations, it was noticeable that the SUMTJ scheme jet stays attached to the surface for long downstream distances at all investigated blowing ratios. Moreover, the lateral expansion angles of the scheme help perform a continuous film from adjacent jets close to the schemes’ exits; however, they have a negative impact on the uniformity of the film thickness in the lateral direction. The vorticity strength downstream the SUMTJ scheme in the y-z plane was much less than the vorticity strength downstream the circular scheme at all blowing ratios. However, the vorticity behavior in the shear layer between the secondary SUMTJ scheme jet and the main stream was changing dramatically with the blowing ratio. The latter is expected to have a significant impact on the film-cooling performance as the blowing ratio increases.