KR20230064848A - Performance analysis of a fluidic oscillator with a tapered outlet - Google Patents

Abstract

The present invention includes an inlet for introducing fluid from the outside; a mixing chamber connected to the rear end of the inlet and discharging the fluid introduced through the inlet as a vibrating jet stream; a feedback passage that causes a portion of the fluid flowing along the inside of the mixing chamber to flow toward the inlet side of the mixing chamber, thereby generating vibrations in the fluid supplied from the inlet side; And an outlet connected to the rear end of the mixing chamber and discharging the fluid passing through the mixing chamber and the bypassed fluid to the outside, wherein the upper surface of the outlet is made of an inclined surface inclined at a corresponding angle, As it is provided on the wing of the aircraft, by discharging the vibrating jet stream to the wing of the aircraft, as the flow separation occurring on the wing of the aircraft by the discharged vibrating jet stream is controlled, the lift and aerodynamic performance of the aircraft wing can be improved. Provided is a fluid vibrator having an inclined outlet that can be.

Description

Performance analysis of a fluidic oscillator with a tapered outlet}

The present invention relates to a fluid vibrator having an inclined outlet, and more particularly, when using an inclined outlet, the overall performance of the fluid vibrator is improved, and the smaller the outlet height and the faster the inclination starts at the same outlet height. As the recording performance improves, it is provided on the wing of the aircraft, and the vibrating jet stream is discharged to the wing of the aircraft, and the flow separation occurring on the wing of the aircraft is controlled by the discharged vibrating jet stream. It relates to a fluid vibrator having an inclined outlet that can improve lift and aerodynamic performance.

In general, a very complex flow phenomenon occurs around an object that maneuvers while receiving lift, such as an airfoil or wing of an aircraft, and this flow phenomenon can be changed by various variables.

Flow separation in aircraft wings negatively affects aerodynamic performance.

Accordingly, many studies on flow separation control have been conducted. Flow control technology is classified into passive flow control (PFC), which attaches various structures to the surface, and active flow control (AFC), which uses actuators. AFC is a disadvantage of PFC. It has the advantage of being able to eliminate the problem of increasing drag, and effective separation control is possible. In particular, the method using the fluid vibrator among the AFC technologies showed superior control effects compared to other methods.

However, the prior art had a problem in that the structure was not only complicated, but also the flow separation control effect did not meet expectations.

As for the prior art, reference may be made to Patent Publication No. 10-1998-014328 (May 25, 1998).

The present invention improves the overall performance of the fluid vibrator when using an inclined outlet, and the smaller the outlet height and the faster the inclination starts at the same outlet height, the better the performance. Fluid with an inclined outlet that can improve the lift and aerodynamic performance of the wing of the aircraft by discharging the vibrating jet stream to the wing of the aircraft and controlling the flow separation occurring on the wing of the aircraft by the vibrating jet stream discharged. It aims to provide a vibrator.

The fluid vibrator having an inclined outlet according to the present invention includes an inlet for introducing fluid from the outside; a mixing chamber connected to the rear end of the inlet and discharging the fluid introduced through the inlet as a vibrating jet stream; a feedback passage that causes a portion of the fluid flowing along the inside of the mixing chamber to flow toward the inlet side of the mixing chamber, thereby generating vibrations in the fluid supplied from the inlet side; and an outlet connected to the rear end of the mixing chamber and discharging the fluid passing through the mixing chamber and the bypassed fluid to the outside, wherein an upper surface of the outlet is formed as an inclined surface inclined at a corresponding angle.

At this time, the inclined surface of the outlet part according to the present invention is preferably an inclined surface formed by connecting the outlet height (a / h) point and the slope starting position (b / L) point.

Here, the outlet height (a/h) according to the present invention is a height in the vertical direction based on the lowest point of the outflow end of the outlet, and is preferably any one of the total height of the outflow end of the outlet 1: 0.1 to 0.9. do.

In addition, the inclination start position (b / L) according to the present invention is the length of the exit direction based on the boundary point of the mixing room and the exit section, and the total length of the exit section is 1: preferably any one of 0.1 to 0.9. .

In addition, it is preferable that the inlet according to the present invention form a shape in which the width gradually narrows in the direction in which the fluid flows.

In addition, it is preferable that the outlet part according to the present invention form a shape in which the width gradually expands in the direction in which the fluid flows.

Effects exhibited by the fluid vibrator having an inclined outlet according to the present invention are as follows.

When using an inclined outlet, the performance of the fluid vibrator is generally improved, and as the outlet height decreases and the inclination starts faster at the same outlet height, the performance improves. As it is provided on the wing of the aircraft, By discharging the vibrating jet stream, the lift and aerodynamic performance of the wing of the aircraft can be improved as flow separation occurring on the wing of the aircraft is controlled by the discharged vibrating jet stream.

1 is a cross-sectional view of a fluid vibrator having an inclined outlet according to an embodiment of the present invention.
Figure 2 is a side view showing the side of the fluid vibrator having an inclined outlet according to an embodiment of the present invention.
3a to 3d are the frequency, maximum speed ratio, pressure drop and jetting angle according to the change of the outlet height (a / h) of the fluid vibrator having an inclined outlet according to an embodiment of the present invention. This is the graph showing the change.
4a to 4d are the frequency, maximum speed ratio, pressure drop (friction coefficient) and jet jet angle according to the change of the inclined start position (b / L) of the fluid vibrator having an inclined outlet according to an embodiment of the present invention It is a graph showing the change of (jetting angle).
5 is a contour diagram showing time average velocity distribution on the zx plane of the fluid vibrator having an inclined outlet according to an embodiment of the present invention.
6 is a contour diagram showing changes in the flow field inside the fluid vibrator according to the vibration phase of the fluid vibrator having an inclined outlet according to an embodiment of the present invention.
7 is a contour diagram showing a change in flow field according to a change in the outlet height (a/h) of a fluid vibrator having an inclined outlet according to an embodiment of the present invention.
8 is a contour diagram showing a change in flow field according to a change in an inclination start position (b/L) of a fluid vibrator having an inclined outlet according to an embodiment of the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the usual or dictionary meaning, and the inventor appropriately uses the concept of terms in order to explain his/her invention in the best way. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical spirit of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, so at the time of this application, they are equivalent alternatives that can be replaced. It should be understood that variations may exist.

The present invention improves the overall performance of the fluid vibrator when using an inclined outlet, and the smaller the outlet height and the faster the inclination starts at the same outlet height, the better the performance. Fluid with an inclined outlet that can improve the lift and aerodynamic performance of the wing of the aircraft by discharging the vibrating jet stream to the wing of the aircraft and controlling the flow separation occurring on the wing of the aircraft by the vibrating jet stream discharged. Regarding the vibrator, the following will be described with reference to the drawings.

The fluid vibrator 100 having an inclined outlet according to an embodiment of the present invention with reference to FIGS. 1 and 2 first has an overall shape of a plate with a height of 1 to 2 mm, an inlet 110, a mixing chamber ( 120), a pair of feedback passages 130, and an outlet part 140.

The inlet 110 introduces fluid at a constant pressure from the outside.

At this time, it is preferable that the inlet portion 110 has a shape in which the width gradually narrows in the direction in which the fluid flows, so that the overall shape is a hopper shape.

In addition, a mixing chamber 120 is connected to the rear end of the inlet 110, and the mixing chamber 120 causes the fluid introduced through the inlet 110 to flow along the inner surface of either side.

At this time, the mixing chamber 120 has a shape in which the width of the inlet 121 side through which the fluid flows into the mixing chamber 120 gradually expands in the direction in which the fluid flows, The fluid introduced through the inlet 110 flows along the inner side of either side of the mixing chamber 120, and the outlet 122 side of which the fluid flows out of the mixing chamber 120 forms a curved shape .

Therefore, the fluid introduced into the mixing chamber 120 through the inlet 110 is discharged through the outlet 122 of the mixing chamber 120 while flowing along one of the inner surfaces of the mixing chamber 120 .

In addition, the mixing chamber 120 is provided with a feedback passage 130, which is branched from the left and right sides of the outlet 122 of the mixing chamber 120 as a pair to form the mixing chamber 120. ) is connected so that the fluid flows toward the inlet 121 side.

At this time, it is preferable to form branch protrusions 123 in a '∧' shape to facilitate branching of the fluid at points where the pair of feedback passages 130 diverge among the mixing chamber 120.

Therefore, some of the fluid flowing along the inner surface of the mixing chamber 120 is branched by the branching protrusion 123, bypasses along the feedback passage 130, and returns to the inlet 121 of the mixing chamber 120. The main flow direction of the fluid introduced into the mixing chamber 120 through the inlet 110 by the air flow flowing into the mixing chamber 120 and branched off from the mixing chamber 120 into the inlet 121 of the mixing chamber 120. Let this lean to one side.

Therefore, as the main flow of the fluid through the pair of feedback passages 130 alternately repeats the phenomenon of the jet stream flowing in one direction, the mixing chamber 120 generates and discharges the vibrating jet stream. .

And, the outlet part 140 is connected to the rear end of the mixing chamber 120, and the outlet part 140 discharges the vibrating jet stream flowing out of the mixing chamber 120.

At this time, it is preferable that the outlet part 140 form a shape in which the width gradually expands in the direction in which the fluid flows.

In addition, the outlet portion 140 is preferably made of an inclined surface 141, the upper side of the outlet portion 140 is inclined at a corresponding angle.

The inclined surface 141 of the outlet part 140 is determined by the change in the outlet height (a/h) and the inclination start position (b/L), and the change in the outlet height (a/h) determines the maximum output of the outlet jet. The speed ratio, frequency and spray angle can be varied.

At this time, the outlet height (a / h) is a vertical height based on the lowest point of the outflow end of the outlet part 140, and the total height of the outflow end of the outlet part 140 is 1: any one of 0.1 to 0.9. point, and the inclination start position (b / L) is a length in the exit direction based on the boundary point of the mixing room and the exit section, and is any one of the total length of the exit section 1: 0.1 to 0.9.

Among them, the maximum speed ratio may be defined as [Equation 1] below.

은 최대 속도 비이고,

는 진동기 출구에서 시간 평균 된 제트 속도의 최대값이며,

는 기준 속도로서 출구 목(throat)에서의 속도이다.here,

is the maximum velocity ratio,

is the maximum of the time-averaged jet velocity at the vibrator exit,

is the speed at the exit throat as the reference speed.

는 아래의 [수학식 2]에 의해 구해질 수 있다.and

Can be obtained by [Equation 2] below.

는 입구에서의 질량 유량,

는 출구 목의 면적, ρ는 25℃에서 공기 밀도이다.here,

is the mass flow rate at the inlet,

is the area of the outlet throat, and ρ is the air density at 25 °C.

)는 아래의 [수학식 3]에 의해 정의된다.In addition, the friction coefficient representing the pressure load in the vibrator (

) is defined by [Equation 3] below.

는 유체진동기 내부의 압력강하이고,

는 출구 목에서 수력 직경이다.here,

is the pressure drop inside the fluid vibrator,

is the hydraulic diameter at the outlet neck.

A numerical analysis of the fluid vibrator 100 having an inclined outlet according to an embodiment of the present invention is as follows.

For flow analysis, commercial CFD software ANSYS CFX 15.0® was used, the 3D Unsteady Reynolds-averaged Navier-Stokes (URANS) equation and continuity equation were used for analysis, and the SST (Shear Stress Transport) model was used as the turbulence model. this was used

It has been reported that the URANS analysis using the SST model predicts the internal flow of a fluid vibrator more accurately than the LES analysis using the WALL model.

In addition, it has been reported that the SST model accurately predicts the flow separation due to the inverse pressure gradient.

의 균일 유동 조건을 부여하였으며, 벽에는 점착조건(no-slip conditions)을 사용하였고, 작동 유체는 25°C에서 공기를 사용하였으며, 이상 기체로 가정하였다.As a boundary condition, at the entrance

A uniform flow condition of was applied, no-slip conditions were used for the wall, air was used as the working fluid at 25°C, and an ideal gas was assumed.

For the grating system of the fluid vibrator 100, an unordered tetrahedral grating was created in all regions using ICEM CFD 15.0®, and a 12-layer prism grating was created to accurately predict the high velocity gradient in the boundary layer.

개 격자점의 최적 격자계를 사용하였다. To use the SST turbulence model at a low Reynolds number, the first grid point near the wall was located at Y+<2 from the wall, and a grid dependence test was performed based on the same calculation of the Grid-convergence index (GCI). for vibrator

An optimal grid system of individual grid points was used.

로 설정하였다. For the analysis of the internal flow of the fluid vibrator (100), the total calculation time per unit calculation is 0.03s, and the time step is

was set to

미만으로 유지되었다. For the URANS analysis, the steady-state RANS calculation result was used as the initial value of the analysis, and the root-mean-square (RMS) value of the relative residual was used as the convergence criterion.

kept below

First, referring to FIGS. 3A to 3D, looking at changes in the frequency, maximum speed ratio, pressure drop, and jetting angle according to the change in the exit height (a / h) of the fluid vibrator 100, the jetting angle is is the oscillation amplitude of the jet at the exit.

To find out the change in vibrator performance according to the change in height, the outlet height (a/h) was calculated by changing the value by 0.1 in the range of a/h = 0.2 ~ 1.0, and the slope start position (b / L) was fixed at b/L = 0.

It can be seen that all performances, except for the friction coefficient related to the pressure drop (see FIG. 3c), improve as the outlet height decreases, and as the outlet height (a/h) decreases, the frequency, maximum speed ratio, and spray angle all decrease. gradually increased.

Therefore, in terms of frequency, maximum speed ratio, and pressure drop, the inclined shape (a/h <1.0) shows superior performance compared to the non-inclined case (a/h = 1.0).

However, in the case of the pressure drop according to the increase in the outlet height (a/h), it slightly increases in the entire section, but there is no significant change in the area except for the sections a/h = 1.0 to 0.9 and a/h = 0.4 to 0.2. there is.

4 shows changes in the frequency, maximum speed ratio, pressure drop, and jetting angle according to the inclination start position (b/L), which is the position at which the inclination of the outlet part starts.

At this time, the exit height (a/h) was fixed at a/h = 0.5, and the slope starting position (b/L) was indicated in the range of b/L = 0 to 1.0.

Unlike the change according to the exit height (a / h), the overall performance change according to the slope start position (b / L) is not large, but the change is relatively large in the section where the slope start position b / L = 0.9 ~ 1 In the case of , it can be seen that there is a rapid change in this section.

In FIGS. 4A and 4B, as the position of the slope start position (b/L) decreases, that is, as the slope starts early, the ratio between the frequency of the jet and the maximum speed becomes gentle in most sections except near the slope start position b/L = 1.0. increase can be seen.

The friction coefficient shown in FIG. 4c shows an almost constant value of Ff = 1.4 in the section except for the slope start position (b/L) near b/L = 0 and 1.0.

In the case of the jet jet angle of FIG. 4D, a constant angle of about 46 degrees is maintained in most sections except near b/L = 1.0.

These results show that the frequency and maximum speed ratio of the outlet change in proportion to the inclination angle of the outlet, but in the case of the injection angle and friction coefficient, the influence of the inclination angle can be ignored except for some sections.

The phenomenon that the performance of the fluid vibrator is improved as the outlet height (a / h) shown in FIGS. 3A to 3D is reduced, as shown in the time average velocity distribution on the z-x plane of FIG. It seems to be a phenomenon that occurs because of the increase.

It is believed that the phenomenon in which the velocity decreases in the direction of the exit from the reference shape is because the cross section of the exit section expands toward the exit surface.

And in FIG. 5, the phenomenon that the maximum velocity point at the exit surface is deflected toward the inclined surface 141 is shown for the exit height (a / h), and even when the exit height is a / h = 0.9, this biased velocity distribution is clearly However, at the exit height a/h = 1.0, which is the standard shape, a symmetrical velocity distribution with the maximum velocity occurring at the center is shown.

The sudden change of the velocity distribution in the exit height a / h = 0.9-1.0 section is shown in Figs. 3a, 3c and 3d for the frequency, friction coefficient and injection angle, respectively, It is thought to have an effect on rapid change.

The maximum outlet velocity ratio (FVR) decreases in proportion to the increase in the outlet height (a/h), which is due to the decrease in flow rate inversely proportional to the increase in cross-sectional area. It shows a similar aspect to the phenomenon that occurs due to the biased velocity distribution due to bending in the fluid vibrator.

6 shows the change in the flow field inside the fluid vibrator according to the phase of vibration. As the exit height (a / h) decreases through the flow field, the spray angle of the jet moving left and right increases noticeably and the width of the jet widens. all.

7 shows the flow field change according to the change of the outlet height (a / h) to compare the time average flow field according to the shape change, and FIG. 8 shows the flow field change according to the change of the slope start position (b / L) will be.

As shown in FIG. 7, it can be seen that the spray angle gradually increases as the outlet height (a/h) decreases, but the flow field does not clearly change in areas other than the outlet.

On the other hand, in the case of FIG. 8, the change in the internal flow according to the slope start position (b / L) is not large except near the slope start position b / L = 1.0.

Therefore, in order to evaluate the performance of the fluid vibrator 100 having an inclined outlet according to an embodiment of the present invention, various performances such as frequency, maximum speed ratio, pressure drop, and jet spray angle were evaluated by the outlet height (a / h) and the outlet The change in the slope starting position (b/L), which is the starting point of the minor slope, was analyzed.

As a result of the calculation, the performance of the vibrator excluding the pressure drop in the case of the inclination (outlet height a/h < 1.0) compared to the case of no inclination at the outlet (exit height a/h = 1.0 or inclination start position b/L = 1.0) shows that it is always improving.

As the outlet height (a/h) decreased, it was confirmed that the frequency, outlet maximum speed ratio, and injection angle increased at an almost constant rate. It wasn't great.

In the case of the slope start position (b/L), the effect on performance was generally smaller than that of the outlet height (a/h), and in particular, the change in pressure drop and spray angle was significantly different except near the slope start position b/L = 1.0. It was very small.

As the slope start position (b/L) became smaller, the frequency and maximum speed ratio gradually improved.

Therefore, it can be seen that the performance of the fluid vibrator generally improves when the inclined outlet is used, and the performance improves as the outlet height decreases and the inclination starts faster at the same outlet height.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is only exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

100: fluid vibrator
110: entrance
120: mixing room
121: inlet
122: outlet
123: divergent projection
130: Feedback Euro
140: exit part
141: slope

Claims (6)

An inlet for introducing fluid from the outside;
a mixing chamber connected to the rear end of the inlet and discharging the fluid introduced through the inlet as a vibrating jet stream;
a feedback passage that causes a portion of the fluid flowing along the inside of the mixing chamber to flow toward the inlet side of the mixing chamber, thereby generating vibrations in the fluid supplied from the inlet side; and
An outlet connected to the rear end of the mixing chamber and discharging the fluid passing through the mixing chamber and the bypassed fluid to the outside; including,
A fluid vibrator having an inclined outlet portion in which an upper surface of the outlet portion is formed of an inclined surface inclined at a corresponding angle.
The method of claim 1,
The inclined surface of the outlet is
A fluid vibrator having an inclined outlet, which is a slope formed by connecting the outlet height (a/h) point and the slope start position (b/L) point.
The method of claim 2,
The outlet height (a / h) is
The height in the vertical direction based on the lowest point of the outlet end of the outlet,
The total height of the outflow end of the outlet part is 1: a fluid vibrator having an inclined surface that is any one of 0.1 to 0.9.
The method of claim 2,
The slope start position (b / L) is
The length of the exit direction based on the boundary point of the mixing room and the exit part,
The total length of the outlet 1: Fluid vibrator having an inclined outlet portion that is an inclined surface of any one of 0.1 to 0.9.
The method of claim 1,
the inlet
A fluid vibrator with an inclined outlet that gradually narrows in width in the direction of fluid flow.
The method of claim 1,
the exit part
A fluid vibrator with an inclined outlet that gradually expands in width in the direction of fluid flow.

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