Synthetic Jets, whose size and weight can be reduced easily, have become an attractive alternative to continuous Jets. Many experimental and numerical studies have been conducted on synthetic Jets to investigate their fundamental flow characteristics, including Jet structure, for applied research such as boundary layer control and enhanced fluid mixing. However, few studies have focused on fluid transportation devices using synthetic Jets as a driving source. Therefore, several issues concerning fluid transport characteristics still need to be resolved. In addition, although optimum operation of devices using synthetic Jets is essential for their practical use, few studies have focused on this issue. The present study experimentally demonstrates the influence of the dimensionless stoke L on the performance characteristics of a synthetic Jet Fan under Reynolds number Re = 1800 and the same Fan geometry; here, the stroke l is nondimensionalized by the primary slot width b. Furthermore, numerical simulations are conducted to complement the experiment. Velocity and pressure measurements are performed using a hot-wire anemometer, differential pressure manometer, and pressure transducer. The influence of the dimensionless stroke L on the performance/efficiency curves, static pressure distribution on the duct surface, and unsteady flow characteristics are investigated. Moreover, the flow field inside the duct is observed through numerical simulation. The results show that the performance characteristics and pressure recovery process depend on the dimensionless stroke L, and an optimum range of dimensionless stroke L exists for operation.

The mechanical ventilation smoke management system involves the use of supply Fan, Jet Fan, and exhaust Fans, which are activated at different times after a fire is extinguished. This paper numerically investigates the effect of the priority and delay of smoke management systems on smoke distribution and visibility in a car park after a fire, using Fire Dynamic Simulation Code 6.7.6. The flow rates of the exhaust Fan, supply Fan and Jet Fan are 1.9 m³/s, 1.43 m³/s, and 1.67 m³/s, respectively. The fire, located near the supply Fans, is modeled as a rectangle with dimensions of 2.0 × 0.8 m² and a power of 1.6 MW, lasting for one minute from ignition to extinguishment. Polyurethane is assumed as the flammable material. The priority and delay of the smoke management systems are evaluated through four scenarios over a period of 420 seconds. The results show that visibility reaches acceptable levels in all scenarios at all locations after 420 seconds. Additionally, the results indicate that the visibility of the upper half is highest for scenario a, at around 15 m. However, the visibility of the lower half is highest for scenario d, ranging between 20 and 30 m. It can be concluded that delaying the activation of smoke management systems is an effective strategy for facilitating smoke removal and fresh air intake.

This paper investigates the influence of a weak-Jet on the development of a turbulent axisymmetric strong Jet. A parametric study is carried out to evaluate simultaneously the effect to the Jets-spacing (S/D=3 and S/D=7. 5) and their velocity ratios in range 0≤ λ ≤ 1. The mixing phenomenon is studied numerically by the finite volume method using the 3D-RANS second-order model, which gives a good agreement with the available data. Three distinct regions of this type of Jets interaction are evidenced. This study confirms that the Jets spacing affects strongly the converging region and has a minor effect on the combining region. It is found that the weak Jet attracts the strong Jet and the combining region extends from 30D to 40D where the self-similarity of a single Jet is obtained. The Jet width decreases when velocity ratio and Jets spacing augment. In the combining region, in comparison with the free Jet, it is found that the addition of a weak-Jet increases the decay rate of the centerline velocity.

To understand the Jet flow characteristics of turboFan separate exhaust system, a parametric design method based on the initial Class Shape Transformation function was developed. HBPR and UHBPR turboFan separate exhaust systems were designed. Furthermore, the Jet flow characteristics of the HBPR turboFan exhaust system under take-off condition with zero angle of attack were studied based on numerical simulation. The Jet flow characteristics of the HBPR and UHBPR turboFan exhaust system under take-off condition with high angle of attack were also simulated. The effects of angle of attack and bypass ratio on the Jet flow characteristics were investigated and the related flow mechanisms were analyzed. Results show that the axisymmetric plumes of the HBPR turboFan exhaust system are distributed around the engine axis under take-off condition with zero angle of attack. With the plug wake as the center, the core flow, the Fan/core shear layer, the Fan flow, the Fan/free stream shear layer and the free stream are wrapped around the plug wake from inside out. Vortexes appear in the lee area at the back of the cowl and Jet flow under take-off condition with high angle of attack. These vortexes cause cross sectional secondary flow and expose the high-velocity core flow to the low-velocity free stream. The contact area and velocity gradient in the mixing region among the free stream, Fan flow and core flow increase. Therefore, the mixture among Jet flow and free stream strengthens. So the high-velocity region, the high-vorticity region, and the high turbulence kinetic energy region shorten by 55. 1%, 47. 7% and 50. 9% respectively. The vorticity values and turbulence kinetic energy level peak on the upper side of the exhaust plumes increase by about 30% and 87% respectively. Relative to these parameters from the HBPR turboFan exhaust system, the Jet velocity peak value of UHBPR turboFan decreases by 5. 5% under take-off condition with high angle of attack. The vorticity values and turbulence kinetic energy level reduce due to decreased velocity gradient in shear layers downstream of the nozzle exit plane. The turbulence kinetic energy level peak on the upper side of the exhaust plumes decreases by 29. 3%. The reasons are that the contact area between high-velocity core flow and the free stream decreases due to thicker Fan flow and the velocity gradient in the core flow and free stream mixing region decreases because of the lower core flow velocity.