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The purpose of this paper is to present the results of mixing promotion and screech frequency of controlled elliptical supersonic jet.

Flow field characteristics of low-aspect-ratio elliptical jets are examined at over-expanded, under-expanded and correctly expanded conditions. The tabs are placed at elliptical jet exit along the major and minor axes.

The results show that the mixing done by the minor axis is superior to the tabs along major axis. At all pressure ratios, the content of jet noise and the frequency are high for the tabs along the major axis because of increase in the amplitude of screech frequency. Further the tabs along minor axis show a dominance of large-scale vertical structures. In under-expanded conditions, the shock cell shows the rapid change because of the presence of tabs. The tabs along minor axis are making the shock weaker, hence no evidence of axis switching.

To achieve the greater performance of jet, the authors need to reduce the potential core length of the issuing jet. This can be achieved by implementing different types of tabs at the exit of the nozzle.

The present paper represents the flow of controlled jet using inverted triangular tabs. By achieving the controlled jet flow, the performance of propulsion systems can be improved. This can be used in systems such as combustion chamber, missile’s noise reduction and thrust vector control.

The purpose of this research is to study and investigate the flow control of 0.8 Mach jet using three tab configurations. The tabs with the slots will eventually lead to generation of vortices and thus enhances the mixing characteristics.

The jet flow control is achieved by the usage of three tabs, namely, Tab A, Tab B and Tab C that are placed at the exit plane of the convergent nozzle at 180 degrees apart. Three tabs with different slot profile are designed with the same constant blockage ratio of 7.3%. The tabs produce vortices of varying sizes that directly influence and modify the jet structure, thereby enhancing the efficiency in mass entrainment and mixing. The tabs are studied numerically first and then are compared with the results of the experiments.

The results are compared with that of the results of the uncontrolled jet. For Mach 0.8 jet, Tab C is found to reduce the core length and gives reduction of 90.23%, in comparison to Tab A and Tab B, which provides 84.1% and 87.79%, respectively. The results of numerical are then compared with the centerline results obtained via experiments. With the engagement of Tabs A, B and C, the jet structure is seen to have been modified at Mach 0.8 with Tab C performing better.

The tabs are a passive control device that can be practically enabled in the aircraft nozzles to control the flow and even suppress the noise emanated by the jet. Tabs can be effectively used for better thrust vector control and assist in jet noise suppression. Thus, this study on tabs and its uses are important and essential in aerospace technology.

This particular study on mechanical slotted tabs is innovatively carried out by designing the tabs in such a way that one such has not been designed before. The slots run through the adjacent sides of the tabs which is a novelty in itself, whereas perforations made only through the opposite sides of the tabs are studied by various researchers till now. The slots in the adjacent faces modify the flow physics in such a way that it enhances mixing by the creation of turbulence because of the interaction between the main stream and the secondary jet exactly at the core. So far, such slots and profiles are not investigated. By the usage of such tabs, the flow to mix faster is much closer to the core of the jet by creating mixed size vortices and thus has higher efficiency.

The purpose of this paper is to propose a combination bank-to-turn control mode with the single moving mass and reaction jet and design the roll control law for the long-range reentry maneuverable warhead.

Based on the dynamics model of this new control mode, the control model of roll channel is converted into a perturbed double-integrator system. The on-off optimal feedback control law is designed on the phase plane formed by Euler angle error and angular velocity error. To weaken the “on-off chattering” that is generated near the origin of the phase-plane and effectively reduce the jet fuel consumption for stability control, an on-off control outer ring and an inner ring are introduced into the phase plane.

This control mode can not only avoid the aerodynamic rudder ablation to improve the efficiency of attitude control, but also reduce the fuel consumption of jet control by using moving mass control. The simulation results indicate that the designed control law can meet the speediness and robustness requirements of the long-range maneuverable warhead controlled by the single moving mass and reaction jet. This measure can also eliminate the on-off chattering effectively.

The new control mode solves some engineering problems of long-range reentry maneuverable warhead controlled by only one actuator. The control mode has a promising prospect in engineering practice.

The paper provides a new control mode and a combination control strategy, and designs an effective control law.

The purpose of this paper is to study the yaw control of the flapless aircraft and investigate the equivalent control effect (ECE) and the power consumption of the pneumatic control.

The control effects of the mechanical control and the pneumatic control are calculated and the ECE curves are obtained. The power consumption of the pneumatic control is analyzed. A new pneumatic drag-type yaw control method is proposed. The mechanisms of the drag-type yaw control and the conventional thrust-type yaw control are explored. The drag-type yaw control is divided into two combined blowing forms: inner-top outer-bottom blowing and inner-bottom outer-top blowing. The differences between two kinds of the drag-type yaw control at a small angle of attack and a large angle of attack are explored.

The ECE curves of the pneumatic control are obtained. The power consumption of the drag-type yaw control is much lower than that of the thrust type. The lift coefficient of the inner-top outer-bottom blowing is higher than that of the inner-bottom outer-top blowing, but the inner-bottom outer-top blowing has higher efficiency of the yaw control at a large angle of attack.

This paper contributes to the research of the flapless aircraft.

A new pneumatic drag-type yaw control method of the flapless aircraft is proposed.

FLUIDICS is a term coined recently defining a rapidly emerging technology which involves the use of gaseous or liquid fluids in motion to perform functions such as amplification, sensing, switching, logic or computation. The accelerating interest in fluidics is no doubt due to the increasing awareness that fluid energy can be manipulated in much the same way as electricity and without moving parts. Also, since fluidic control components are highly reliable under extreme environmental conditions and are impervious to radiation — magnetic or nuclear—they offer many advantages for use in aerospace or nuclear engineering. These particular advantages and others, coupled with the probable low ultimate economic costs of fluidic components, are further stimulating active interest in many commercial and industrial applications.

The purpose of this paper is to evaluate the synthetic jet actuator design's performance based on piezoelectric diaphragms that can be appropriately used for flow separation control.

Design the synthetic jet actuators by means of estimating the several parameters and non‐dimensional parameters. Understanding the relationship and coupling effects of these parameters on the actuator to produce exit air jet required. Experiments were conducted to measure the exit air jet velocity using a hot‐wire anemometry and determine the good operational frequencies and voltages of the actuators for different cavity volume.

The performance of synthetic jet actuator is not consistent to a particular given frequency and it depends on design configurations. Each actuator will give a very good speed for a certain frequency. The results show that the exit air jet velocity increases would be better if the cavity volume is reduced and if the input voltage is increased to certain limits.

The limit of input voltage for the actuators that can be achieved for good jet speed is 2V of about 205V output voltage for each frequency. The jet speed obtained is sufficient enough to control the separation for an aircraft which has a small wing chord and low speed. Therefore, more studies are needed to optimize the sizes of an orifice and cavity, and the selection of piezoelectric diaphragm.

The study helps in establishing a flow control device for controlling flow separation, especially on airfoils.

Design the synthetic jet actuators based on piezoelectric diaphragm for applications of flow separation control.

This paper aims to present the jet mixing effectiveness of triangular tabs with semi-circular corrugations to control the subsonic and sonic correctly expanded jets.

Three semi-circular corrugated triangular tabs (Tab A, Tab B and Tab C) of equal blockage 5.11% are used, in which the corrugation locations on the tabs are varied. The offset distance between the semi-circular corrugations at the leaned edges of the triangular tabs are 0.0, 0.75 and 1.5 mm for the Tabs A, B and C, respectively. Two identical semi-circular corrugated tabs has been placed exactly 180° apart at the exit of the convergent nozzle. The pitot pressure measurements were taken to study the jet mixing characteristics of the tabs for the jet exit Mach numbers of 0.6, 0.8 and 1.0, and it is compared with the free jet.

The jet centerline pitot pressure decay reveals that, Tab A is very effective than Tab B and Tab C. For the jet exit Mach numbers of 0.6, 0.8 and 1.0, the potential core reduction for the Tab A is found to be 69.1%, 69.7% and 70.8%, respectively, when compared with the free jet.

The semi-circular corrugated triangular tabs were found to be more effective than the plain triangular tabs of equal blockage ratio for reducing the core length with minimum thrust loss.

The offset distance of the semi-circular corrugations are varied along the leaned sides of the triangular tabs, which is the novelty of this study.

The purpose of this study is to compare two unsteady actuators: an oscillator and a sweeping jet. Both actuators can produce an oscillating jet of different amplitudes and frequencies without any moving parts, making them an attractive actuator concept. The Coanda effect phenomenon can explain the operating principles of these two unsteady actuators.

A numerical study was conducted to compare the amplitudes and frequencies of fluidic and sweeping jet (SJ) oscillators to obtain an efficient actuator to control separated flows at high Reynolds numbers. For this goal, two-dimensional unsteady Reynolds-averaged Navier-Stokes simulations were carried out using computational fluid dynamics (CFD) fluent code to evaluate the actuator performances. The discrete fast Fourier transform method determined the oscillation frequencies.

The oscillation frequencies gradually increase as the inlet pressure increases. The characteristics and dimensions of the vortices produced in the mixing chamber and feedback loops vary overtime when the injected fluid is swept sideways. The frequencies supplied by the SJ are stronger than those obtained by the fluidic oscillator, which may contribute to improving the aerodynamic performance at a lower power supply cost.

The existence of the splitter in the fluidic oscillator led to the production of separate pulses, which would be useful in various industrial applications, including active control of combustion and mixing processes while other applications such as flow separation control require SJs. With the latter actuator higher and interesting frequencies can be obtained, leading to efficient flow control.

This paper presents an experimental investigation to study the effectiveness of micro jets under the influence of Over, Under, and Correct expansion to control the base pressure in suddenly expanded axi‐symmetric ducts.

Four micro jets of 1 mm orifice diameter located at 90° intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region was employed as active controls. The tests were conducted for Mach numbers 1.5, 1.3, 1.6, 1.8, 2.0, 2.5, and 3.0. The jets were expanded suddenly into an axi‐symmetric tube with cross‐sectional area 2.56 times that of nozzle exit area. The L/D ratio of the sudden expansion tube was varied from 10 to 1.

From the present studies, it was found that the maximum increase in base pressure is 152 percent for Mach number 2.58. It is found that the micro jets do not adversely influence the wall pressure distribution.

As a result of developments in space flights and missile technology, the base flows at high Reynolds numbers continues to be an important area of research. Our understanding of many features of base flows remains poor, due to inadequate knowledge of turbulence, particularly in the presence of strong pressure gradient.

The paper shows that micro jets can serve as an effective controller raising the base suction to almost zero level for some combination for parameters. The nozzle pressure ratio has a definite role to play in fixing the base pressure with and without control. There is no adverse effect of the micro jets on the flow field in the duct.

Studying the effect of localized wall discharge on the fluid flow and heat transfer for a flow over backward facing step is the main purpose of this paper. Jet is used to control the reattachment length which controls the fluid flow and heat transfer downstream the step. Several parameters are to be investigated: geometric; expansion ratio, location of the jet, and jet angle flow; Reynolds number, jet velocity.

Numerical simulation using both the standard K−ε and renormalized group turbulence theory (RNG) K−ε models are used to model flow in the computational domain. The energy equation is also used to model the heat transfer characteristics of the flow. The model equations are solved numerically using a finite volume code.

It is found that the presence of the wall jet at a proper location can significantly influence the flow and heat characteristics of the problem. Furthermore, varying the ratio of the jet velocity to the main stream velocity could play an important role in controlling the size of the circulating bubble and, therefore, the fluid and heat transfer characteristics of the flow, whereas, the expansion ratio has less influence. It is also found that increasing Reynolds number increases the value of maximum heat transfer but has less influence on either its location or the reattachment length.

The range of the Reynolds number considered in this research covers only the turbulent regime. The research does not cover laminar flows. The results and conclusions cover only three values of expansion ratios. Namely (expansion ratio (ER)=1.67, 1.8 and 2). Conclusions should not be read beyond these values of ER.

This work gives designers of similar flows a new method of controlling the fluid flow and heat transfer by varying jet angle.

This work has not been done before and it can initiate additional research projects as investigating the effect of applying wall jets in combustors.